Q-1 What do you mean by pressure vessel? Enlist the applications of it.
Ans.
A pressure vessel is a container designed to hold fluids or gases at a pressure significantly different
from the ambient pressure. It is constructed to withstand the internal pressure and maintain the
safety of its contents. Pressure vessels are commonly used in various industries and applications due
to their ability to store and transport substances under high pressure. Here are some notable
applications of pressure vessels:
1. Industrial Manufacturing: Pressure vessels are extensively used in industries such as chemical
processing, oil and gas, pharmaceuticals, petrochemicals, and food processing. They play a crucial
role in storing and processing various chemicals, gases, and liquids.
2. Power Generation: Pressure vessels are an integral part of power generation systems. They are
used in boilers to generate steam at high pressure and temperature, which is then used to drive
turbines and produce electricity in power plants.
3. Oil and Gas Industry: Pressure vessels are vital components in the oil and gas industry for storing
and transporting crude oil, natural gas, and other petroleum products. They are used in refineries,
offshore platforms, and pipelines.
4. Nuclear Industry: Nuclear power plants employ pressure vessels to contain nuclear reactors and
maintain the high-pressure coolant that circulates around the reactor core. These vessels are built
to withstand extreme conditions and ensure the safe operation of nuclear reactors.
5. Aerospace and Aviation: Pressure vessels are utilized in aerospace applications, such as spacecraft,
satellites, and aircraft. They are used to store fuel, gases, and other fluids required for propulsion
and life support systems.
6. Water Treatment: Pressure vessels are employed in water treatment plants for various purposes,
including filtration, reverse osmosis, and water softening. They help in the purification and
distribution of clean water.
7. Automotive Industry: Compressed natural gas (CNG) cylinders used in vehicles are a type of
pressure vessel. These cylinders store natural gas at high pressure and provide an alternative fuel
source for automobiles.
8. Refrigeration and HVAC Systems: Pressure vessels are used in refrigeration and air conditioning
systems to store and circulate refrigerants under high pressure. They play a crucial role in maintaining
the desired temperature and cooling effect.
9. Research and Development: Pressure vessels find applications in laboratories and research
facilities for conducting experiments, simulations, and testing of materials under specific pressure
conditions.
It is important to note that pressure vessels are subject to strict regulations and codes to ensure their
safe design, construction, and operation. Regular inspections and maintenance are essential to
prevent failures and ensure the integrity of pressure vessels in various industries.
Q-2 What do you understand by prestressing of the cylinders?
Ans.
Prestressing of cylinders refers to the application of internal or external forces to induce compressive
stresses within the cylinder's structure before it is subjected to any external loads. This technique is
commonly employed in the construction of concrete and steel cylinders to enhance their structural
strength, durability, and resistance to certain types of loading.
In the context of concrete cylinders, prestressing is typically achieved by embedding high-strength
steel wires, strands, or bars within the concrete before it cures. These elements, known as
prestressing tendons, are tensioned or stretched to a predetermined level and then anchored to the
cylinder. As a result, when the concrete sets and hardens, it experiences compressive forces due to
the pulling action of the prestressed tendons.
Prestressing of cylinders offers several advantages:
1. Increased Load-Carrying Capacity: The compressive stresses induced by prestressing counteract
the tensile stresses that would occur under external loads. This effectively increases the loadcarrying capacity of the cylinder and allows it to withstand larger applied forces.
2. Crack Control: By introducing compressive stresses in the cylinder, prestressing helps control and
minimize cracking. The compressive forces resist tensile forces that could cause cracks to develop
and propagate within the structure.
3. Improved Durability: Prestressed cylinders exhibit improved resistance against various forms of
degradation, such as shrinkage, temperature changes, and chemical attacks. The compressive
stresses mitigate the effects of these factors and enhance the overall durability of the structure.
4. Longer Spans: Prestressing allows for the construction of cylinders with longer spans between
supports. The increased load-carrying capacity and reduced deflections enable the use of thinner
and more lightweight cylinders, leading to cost savings in material and construction.
5. Efficient Material Usage: Prestressing helps optimize the use of construction materials by reducing
the amount of concrete or steel required to achieve the desired structural capacity. This can lead to
cost savings and more sustainable construction practices.
Prestressed cylinders are commonly used in a variety of applications, including bridges, storage
tanks, water pipes, silos, and other structures that require high strength and resistance to external
forces. The technique of prestressing has significantly contributed to the advancement of structural
engineering, allowing for the construction of more efficient and durable cylindrical structures.
Q-3 Give proper classification of Pressure vessel in detail.
Ans.
Pressure vessels can be classified based on various criteria. Here is a detailed classification of
pressure vessels:
1. Based on Design Configuration:
a. Cylindrical Vessels: These vessels have a cylindrical shape and are the most common type of
pressure vessel. They can have flat or dished ends.
b. Spherical Vessels: These vessels have a spherical shape, offering uniform internal pressure
distribution and minimizing stress concentrations. They are suitable for high-pressure applications.
c. Conical Vessels: These vessels have a conical shape, typically used for specialized applications
such as storage hoppers and separators.
d. Multilayered Vessels: These vessels consist of multiple layers, often with insulation between
them, to meet specific requirements like temperature control.
2. Based on Purpose:
a. Storage Vessels: These vessels are designed to store fluids or gases under pressure, such as in
tanks for storing liquids or gas cylinders.
b. Process Vessels: These vessels are used for chemical reactions, heat exchange, or other
processes. Examples include reactors, distillation columns, and heat exchangers.
3. Based on Construction Material:
a. Steel Vessels: Steel is a common material used in pressure vessel construction due to its strength,
durability, and suitability for a wide range of applications.
b. Non-Steel Vessels: Pressure vessels can also be constructed from non-ferrous metals like
aluminum, titanium, or alloys, as well as composite materials.
4. Based on Pressure Level:
a. Low-Pressure Vessels: These vessels are designed to operate at relatively low pressures, typically
below 15 psi (pounds per square inch).
b. Medium-Pressure Vessels: These vessels operate at moderate pressures, ranging from around
15 psi to a few hundred psi.
c. High-Pressure Vessels: These vessels are designed to handle high-pressure applications, typically
above a few hundred psi and reaching several thousand psi.
5. Based on Function:
a. Separators: These vessels are used to separate different components of a mixture, such as in oil
and gas production, where they separate oil, gas, and water.
b. Accumulators: These vessels store fluid under pressure for various purposes, such as hydraulic
systems to provide energy for rapid release when needed.
c. Reactors: Pressure vessels used for chemical reactions, such as in the production of
petrochemicals or pharmaceuticals.
d. Heat Exchangers: These vessels facilitate the transfer of heat between two fluids, such as in
industrial processes or HVAC systems.
6. Based on Regulatory Codes:
Pressure vessels are also classified based on the specific regulatory codes they adhere to, such as
ASME (American Society of Mechanical Engineers) Boiler and Pressure Vessel Code, PED (Pressure
Equipment Directive), or other national or international standards.
It's important to note that pressure vessels must comply with relevant design codes, standards, and
regulations to ensure their safe design, fabrication, and operation. These classifications help in
understanding and categorizing pressure vessels based on their design, purpose, and application
requirements.
Q-4 Why pressure vessel fails? Explains modes of failure.
Ans.
Pressure vessels can fail due to various factors, including design flaws, material defects, operational
errors, or external factors. Here are some common modes of pressure vessel failure:
1. Overpressure Failure: Excessive internal pressure beyond the vessel's design limits can lead to
overpressure failure. This can occur due to equipment malfunctions, control system failures, or
operator errors. The vessel may rupture or burst, causing a catastrophic failure.
2. Fatigue Failure: Repeated cyclic loading and unloading of a pressure vessel can lead to fatigue
failure over time. This occurs when the material undergoes progressive damage and cracks develop
and propagate under the applied cyclic stresses. Fatigue failure is common in vessels subjected to
fluctuating pressures or temperature variations.
3. Brittle Fracture: Brittle materials, such as certain steels at low temperatures, are susceptible to
brittle fracture. When subjected to sudden or excessive stress, they can fracture without significant
deformation or warning signs. Brittle fractures are often characterized by a sudden and complete
separation of the vessel.
4. Corrosion Failure: Corrosion is a common cause of pressure vessel failure, particularly in vessels
that handle corrosive fluids or gases. Prolonged exposure to corrosive environments can weaken the
material, leading to localized thinning, pitting, or stress corrosion cracking. Corrosion can
compromise the structural integrity of the vessel, resulting in leaks or ruptures.
5. Welding or Joint Failure: Pressure vessels are typically fabricated by welding various components
together. Poor welding techniques, improper material selection, or inadequate inspection of welds
can result in welding or joint failures. These failures may occur at the weld itself or in the heataffected zone surrounding the weld, leading to leakage or rupture.
6. Creep Failure: When a pressure vessel is exposed to high temperatures and sustained loads over
an extended period, it may experience creep failure. Creep is a time-dependent deformation that
occurs at elevated temperatures and can lead to permanent distortion or rupture of the vessel.
7. External Damage: Pressure vessels can be subjected to external damage from factors such as
impact, fire, or seismic events. These external forces can cause dents, cracks, or distortions in the
vessel, compromising its structural integrity and leading to failure.
8. Material Defects: Inadequate material quality, manufacturing defects, or material degradation
over time can contribute to pressure vessel failure. Material defects, such as inclusions or weak
spots, can act as stress concentration points and initiate cracks or fractures.
It is essential to conduct regular inspections, maintenance, and testing of pressure vessels to identify
any potential signs of failure and take appropriate preventive measures. Adhering to relevant design
codes and standards, using quality materials, employing proper fabrication techniques, and
implementing robust quality control measures are crucial for minimizing the risk of pressure vessel
failures.
Q-5 Differentiate between IBR and non IBR pressure vessel.
Ans.
IBR (Indian Boiler Regulations) and non-IBR pressure vessels are two categories that differentiate
pressure vessels based on their compliance with specific regulatory standards. Here are the key
differences between IBR and non-IBR pressure vessels:
1. Regulatory Compliance:
- IBR Pressure Vessel: IBR pressure vessels are designed, manufactured, and operated in
accordance with the regulations set forth by the Indian Boiler Regulations (IBR). These regulations
are enforced in India and cover various aspects, including design, construction, inspection, and
certification of boilers and pressure vessels.
- Non-IBR Pressure Vessel: Non-IBR pressure vessels do not need to comply with the specific
requirements outlined by the Indian Boiler Regulations. They may still adhere to other applicable
standards or codes, but they are not subject to the IBR certification process.
2. Certification and Inspection:
- IBR Pressure Vessel: IBR pressure vessels must undergo a stringent certification process as per the
Indian Boiler Regulations. The design, fabrication, and inspection of these vessels are subject to
scrutiny by authorized inspection agencies to ensure compliance with safety standards. The vessels
need to obtain an IBR certification before they can be operated in India.
- Non-IBR Pressure Vessel: Non-IBR pressure vessels are not required to undergo the IBR
certification process. However, they may still be subject to inspections and certifications mandated
by other relevant codes or standards applicable in their respective regions.
3. Jurisdiction:
- IBR Pressure Vessel: The Indian Boiler Regulations primarily apply to pressure vessels used in
India. These vessels must comply with the regulations to ensure their safety and legality within the
Indian jurisdiction.
- Non-IBR Pressure Vessel: Non-IBR pressure vessels are not bound by the specific regulations of
the Indian Boiler Regulations. They may be designed and operated based on other relevant
international or local standards depending on the country or region where they are being used.
4. Documentation and Record-keeping:
- IBR Pressure Vessel: IBR pressure vessels require extensive documentation and record-keeping
throughout their lifecycle. This includes design calculations, material certifications, inspection
reports, and other relevant documents specified by the Indian Boiler Regulations.
- Non-IBR Pressure Vessel: Non-IBR pressure vessels may still require documentation and records
as mandated by other applicable standards or local regulatory requirements.
It is important to note that the specific requirements and regulations for pressure vessels may vary
from country to country. Compliance with the appropriate regulations ensures the safe design,
fabrication, and operation of pressure vessels, protecting both personnel and the environment.
Q-6 Explain various allowances in design of pressure vessel.
Ans.
In the design of pressure vessels, various allowances are incorporated to account for different factors
and ensure the safety, reliability, and functionality of the vessel. Here are some of the key allowances
considered during the design process:
1. Thickness Allowance: The thickness allowance is an additional thickness added to the vessel's wall
to account for factors such as corrosion allowance, erosion, wear, and potential future degradation.
It provides a margin of safety and allows for the vessel's extended service life by accommodating
potential material loss over time.
2. Welding Allowance: Welding allowance refers to the additional material added to the joint during
welding. It compensates for weld shrinkage, distortion, and the need for proper welding penetration
and reinforcement. Welding allowances ensure the strength and integrity of welded joints,
accounting for the material consumed during the welding process.
3. Flange Facing and Gasket Seating Allowance: Flange facing allowance is the additional material
provided on the flange face to allow for proper gasket seating and sealing. It ensures a reliable and
leak-free connection between flanged components. The gasket seating allowance accounts for the
compression and deformation of the gasket material to achieve an effective seal.
4. Reinforcement Allowance: Reinforcement allowance is the additional material provided around
openings, nozzles, or connections in the vessel's wall to strengthen the structure and prevent stress
concentrations. It ensures that the vessel can withstand the stresses induced by the connected
piping or equipment.
5. Nozzle Projection Allowance: Nozzle projection allowance is the additional length or protrusion
provided for nozzles extending through the vessel's wall. It allows for proper connection, sealing,
and accessibility for piping or equipment attachment to the vessel.
6. Hydrostatic Test Allowance: Hydrostatic test allowance refers to the additional thickness or
reinforcement added to the vessel's wall to account for the temporary internal pressure during the
hydrostatic testing process. It ensures that the vessel can withstand the test pressure without
permanent deformation or failure.
7. Material Allowance: Material allowance accounts for the expected variations in material
properties, such as mechanical strength, corrosion resistance, and other factors. It ensures that the
selected material has sufficient margin to meet the required design specifications and provides a
safety factor against potential material deviations.
8. Fabrication and Machining Allowance: Fabrication and machining allowances consider the
tolerances, allowances, and additional material required during the manufacturing process. It
accounts for factors such as machining operations, surface finish, dimensional variations, and
alignment requirements during fabrication.
These allowances are essential in pressure vessel design to accommodate potential variations,
uncertainties, and operational conditions. They ensure that the vessel can withstand anticipated
loads, environmental factors, and potential degradation over its intended service life. Designers
consider these allowances based on engineering standards, codes, and experience to achieve safe
and reliable pressure vessel designs.
Q-7 Discuss various steps of piping design.
Ans.
Piping design involves several steps to ensure the efficient and safe transportation of fluids or gases
within a facility or system. Here are the various steps involved in the piping design process:
1. Understanding Project Requirements: The first step is to gather and understand the project
requirements, including the fluid or gas being transported, flow rates, pressure and temperature
conditions, system constraints, and safety considerations. This information forms the basis for the
design process.
2. Piping Layout Planning: In this step, the overall layout and arrangement of the piping system are
planned. Factors such as equipment locations, space availability, accessibility for maintenance, and
safety requirements are taken into account. Preliminary routing of main lines and identification of
major components are determined.
3. Equipment and Component Selection: Based on the project requirements, suitable equipment and
components such as pumps, valves, fittings, and instruments are selected. Factors such as pressure
rating, material compatibility, operational conditions, and industry standards are considered during
the selection process.
4. Sizing and Hydraulic Analysis: The sizing of pipes is performed to ensure the desired flow rates and
pressure drops are achieved within the system. Hydraulic analysis involves calculating pressure
losses, selecting pipe sizes, and determining the pump or compressor requirements. Consideration
is given to factors such as fluid properties, pipe lengths, fittings, and flow characteristics.
5. Stress Analysis: Stress analysis is crucial to ensure the integrity and safety of the piping system. It
involves evaluating the stress levels, deflection, and potential failure points due to various loads,
including pressure, temperature, weight, and external forces. Analysis is performed using software
tools and industry codes and standards such as ASME B31.1 or B31.3.
6. Material Selection: The appropriate materials for pipes, fittings, and other components are
selected based on factors such as fluid properties, temperature, pressure, corrosion resistance, and
cost. Materials must comply with relevant standards and codes to ensure compatibility and longevity.
7. Piping Specification and Detailing: Detailed specifications and drawings are prepared, specifying
the dimensions, materials, fittings, and components for each segment of the piping system. This
includes specifying welding requirements, flange ratings, insulation, and other necessary details.
Compliance with applicable codes and standards is ensured.
8. 3D Modeling and Clash Detection: Using computer-aided design (CAD) software, a 3D model of
the piping system is created. Clash detection is performed to identify any interference or clashes
with other equipment, structures, or piping within the plant. Modifications are made to resolve
clashes and ensure proper fit and functionality.
9. Support Design: Piping supports and hangers are designed to provide adequate support, minimize
stress, and prevent excessive movement or vibration. Support locations, types, and materials are
determined to ensure proper weight distribution and thermal expansion compensation.
10. Documentation and Deliverables: Comprehensive documentation is prepared, including piping
isometric drawings, bill of materials, equipment datasheets, valve lists, and other required
deliverables. These documents serve as references for construction, installation, and future
maintenance and are essential for project execution.
It's important to note that the steps may vary depending on the complexity and specific
requirements of the project. Collaboration with other engineering disciplines, adherence to relevant
codes and standards, and regular reviews and checks throughout the design process are crucial for
a successful piping design.
Q-8 Differentiate: Hydrodynamic Bearing and Hydrostatic bearing.
Ans.
Hydrodynamic bearings and hydrostatic bearings are two types of bearings that differ in the way
they generate the necessary fluid film to support the rotating shaft. Here's a comparison between
hydrodynamic bearings and hydrostatic bearings:
1. Operating Principle:
- Hydrodynamic Bearing: In a hydrodynamic bearing, the rotating shaft generates a wedge of fluid
between the bearing surface and the shaft through the relative motion and pressure difference. This
fluid wedge creates a hydrodynamic lift, which supports the shaft and reduces contact and friction.
- Hydrostatic Bearing: In a hydrostatic bearing, an external pressurized fluid supply is used to create
a high-pressure fluid film between the bearing surface and the shaft. This pressurized fluid is supplied
by a pump or another source and is used to support the shaft, providing a hydrostatic lift.
2. Fluid Supply:
- Hydrodynamic Bearing: A hydrodynamic bearing does not require an external fluid supply. The
fluid film is generated solely by the relative motion between the rotating shaft and the bearing
surface.
- Hydrostatic Bearing: A hydrostatic bearing requires an external fluid supply to generate the highpressure fluid film. The fluid is supplied through dedicated channels or through a pressurized
lubrication system.
3. Load Capacity:
- Hydrodynamic Bearing: The load capacity of a hydrodynamic bearing is limited by the bearing
geometry, relative speed, and fluid properties. It can handle moderate to high loads depending on
the design.
- Hydrostatic Bearing: Hydrostatic bearings have a higher load capacity compared to hydrodynamic
bearings. The external pressurized fluid supply allows for increased load-carrying capability, making
them suitable for applications with high loads.
4. Stiffness and Damping:
- Hydrodynamic Bearing: Hydrodynamic bearings provide relatively lower stiffness and damping
compared to hydrostatic bearings. They exhibit some inherent damping properties due to the fluid
film, which can help attenuate vibrations.
- Hydrostatic Bearing: Hydrostatic bearings offer higher stiffness and damping characteristics. The
pressurized fluid film provides a more rigid support, allowing for improved control of vibrations and
better damping of dynamic loads.
5. System Complexity:
- Hydrodynamic Bearing: Hydrodynamic bearings are generally simpler in design and do not require
additional components or fluid supply systems. They are self-sustaining and rely on the rotating shaft
for generating the fluid film.
- Hydrostatic Bearing: Hydrostatic bearings are more complex as they require an external fluid
supply, which involves additional components such as pumps, filters, regulators, and control systems.
This complexity adds to the cost and maintenance requirements.
6. Speed Limitations:
- Hydrodynamic Bearing: Hydrodynamic bearings have limitations on the maximum operating
speed. Excessive speeds can lead to reduced fluid film thickness and increased friction, causing wear
and potential bearing failure.
- Hydrostatic Bearing: Hydrostatic bearings can operate at higher speeds since the pressurized fluid
supply ensures a constant fluid film thickness and reduced friction.
Both hydrodynamic and hydrostatic bearings have their specific advantages and limitations, and the
choice between them depends on the application requirements, load conditions, speed, and other
factors.
Q-9 Describe any two clamping components for fixture.
Ans.
Clamping components play a crucial role in fixturing, which is the process of holding and securing a
workpiece in place during machining, assembly, or inspection operations. These components provide
stability, accuracy, and repeatability in the workpiece positioning. Here are some common clamping
components used in fixtures:
1. Clamps: Clamps are versatile and widely used clamping components in fixtures. They come in
various types, including:
- Toggle Clamps: Toggle clamps use a lever mechanism to exert clamping force. They have a quickrelease feature and are ideal for applications that require rapid clamping and unclamping.
- C-Clamps: C-Clamps have a C-shaped frame with a screw mechanism for tightening and releasing.
They are commonly used for general-purpose clamping.
- Strap Clamps: Strap clamps consist of a flexible strap or band that wraps around the workpiece
and is tightened using a tensioning mechanism. They are suitable for irregularly shaped or fragile
workpieces.
- Bar Clamps: Bar clamps utilize a long bar or pipe to provide clamping force. They are useful for
securing larger workpieces or multiple workpieces simultaneously.
2. Vises: Vises are robust clamping components typically used for holding workpieces securely in a
fixed position during machining operations. They offer a stable platform and allow for precise
positioning. Common types include:
- Bench Vises: Bench vises are mounted on workbenches or tables and provide clamping force using
a screw mechanism. They are commonly used in woodworking, metalworking, and general assembly
applications.
- Machine Vises: Machine vises are specifically designed for use on machine tools. They are typically
mounted on milling machines, drill presses, or CNC machines and provide secure clamping during
machining processes.
3. Clamping Fixtures: Clamping fixtures are specialized components designed for specific workpiece
shapes or operations. They are custom-built to ensure accurate and repeatable positioning of the
workpiece. Some common types include:
- Cylindrical Fixtures: Cylindrical fixtures are designed to securely hold round or cylindrical
workpieces. They may include adjustable jaws or collets to accommodate various diameters.
- Four-Jaw Chucks: Four-jaw chucks are used for holding irregularly shaped or non-circular
workpieces. They feature four independently adjustable jaws to provide flexibility in clamping.
- Pneumatic or Hydraulic Clamps: Pneumatic or hydraulic clamps use air or fluid pressure to exert
clamping force. They provide consistent and powerful clamping and are often used in highproduction environments.
4. Clamping Straps and Blocks: Clamping straps and blocks are used to hold workpieces firmly against
a fixture or work surface. They may consist of straps, clamping blocks, or wedges that apply pressure
to the workpiece, ensuring stability during machining or assembly processes.
These are just a few examples of clamping components used in fixtures. The selection of clamping
components depends on the specific requirements of the workpiece, the type of operation being
performed, and the desired level of accuracy and repeatability.
Q-10 What is MEMS? How it is useful in Machine design?
Ans.
MEMS stands for Microelectromechanical Systems. It refers to the integration of miniature
mechanical and electrical components, such as sensors, actuators, and microelectronics, on a single
microchip. MEMS technology allows for the creation of tiny devices or systems that can sense,
control, and interact with the surrounding environment.
MEMS devices have various applications in machine design and offer several advantages:
1. Miniaturization: MEMS devices are extremely small in size, typically ranging from micrometers to
millimeters. This miniaturization enables the integration of complex mechanical and electrical
components into compact systems. In machine design, this allows for the creation of smaller, more
efficient, and lightweight devices or sensors.
2. Sensing and Actuation: MEMS devices can incorporate sensors and actuators to detect and
measure physical phenomena, such as pressure, temperature, acceleration, rotation, and chemical
properties. These sensors can provide real-time data about the operating conditions of a machine,
allowing for intelligent control and optimization.
3. Enhanced Performance: By integrating MEMS sensors, machines can achieve improved
performance and functionality. For example, accelerometers can measure vibrations or motion,
enabling vibration analysis and control systems to minimize structural damage and enhance
precision. Pressure sensors can monitor fluid pressure to ensure optimal performance and prevent
failures.
4. Energy Efficiency: MEMS technology enables the development of energy-efficient machines. For
instance, MEMS sensors can be used to monitor and control energy consumption, optimizing the
operation of motors, pumps, and other devices. This leads to energy savings and improved overall
efficiency.
5. Reliability and Durability: MEMS devices are known for their robustness and durability due to their
small size and monolithic integration. They are less susceptible to mechanical wear and have fewer
moving parts, reducing the chances of failure. This reliability makes MEMS devices suitable for harsh
environments and long-term operation.
6. Cost-Effectiveness: The mass production capabilities of MEMS technology have led to reduced
manufacturing costs for these devices. The small size, integration, and batch fabrication techniques
make MEMS devices cost-effective for various applications. This affordability opens up opportunities
for incorporating MEMS technology in machine design, even for cost-sensitive projects.
7. Connectivity and Internet of Things (IoT): MEMS devices can be easily integrated with wireless
communication capabilities and network connectivity. This allows for seamless data transfer, remote
monitoring, and control. In the era of IoT, MEMS devices play a crucial role in enabling connectivity
and smart functionalities within machines and industrial systems.
Overall, MEMS technology offers significant advantages in machine design, including miniaturization,
sensing and actuation capabilities, enhanced performance, energy efficiency, reliability, costeffectiveness, and connectivity. These benefits enable the development of smarter, more efficient,
and responsive machines that can revolutionize various industries, including robotics, healthcare,
automotive, aerospace, and manufacturing.
Q-11 Describe design consideration for fixture.
Ans.
Designing a fixture involves considering various factors to ensure its effectiveness, efficiency, and
reliability in holding and positioning a workpiece during machining, assembly, or inspection
processes. Here are some key design considerations for fixtures:
1. Workpiece Accessibility: The fixture design should provide easy access to the workpiece for
loading and unloading. Sufficient clearance and space must be provided to accommodate tools,
clamps, and operator's hands for efficient workpiece handling.
2. Workpiece Positioning and Alignment: The fixture should accurately position and align the
workpiece to ensure consistent and precise machining or assembly. Proper locating features, such as
pins, slots, or clamps, should be incorporated to secure the workpiece in the desired position.
3. Clamping and Holding Mechanism: The clamping mechanism of the fixture should securely hold
the workpiece in place to resist machining forces, vibrations, and other external loads. The clamps
or holding elements must be designed to provide adequate clamping force without distorting or
damaging the workpiece.
4. Modular Design: Modular fixtures allow for versatility and adaptability to accommodate different
workpiece sizes, shapes, and configurations. Incorporating adjustable elements or interchangeable
components within the fixture design enables quick setup and reconfiguration for different
workpiece requirements.
5. Rigidity and Stability: The fixture should be rigid and stable to minimize deflection and vibration
during machining or assembly operations. Proper material selection and structural design, including
reinforcements and gussets, are essential to maintain fixture stability and ensure accurate results.
6. Clearances and Interference: Sufficient clearance should be provided between the workpiece,
tools, and fixtures to prevent interference during machining or assembly. This includes considering
the tool paths, tool lengths, and any additional components like sensors or actuators that may be
required.
7. Ergonomics and Operator Safety: The fixture design should consider ergonomic factors to provide
a comfortable and safe working environment for the operator. This includes considerations such as
operator reach, visibility, and access to controls, as well as incorporating safety features to prevent
accidental contact with moving parts or sharp edges.
8. Material and Surface Finish: The choice of fixture material should be compatible with the
workpiece material to avoid contamination or damage. Additionally, surface finishes should be
carefully considered to provide appropriate friction and wear characteristics, ensuring smooth
workpiece movement and preventing damage.
9. Chip and Coolant Management: The fixture design should incorporate provisions for effective chip
removal and coolant drainage to maintain a clean working environment and prevent chip
accumulation that may interfere with machining operations or affect workpiece quality.
10. Tolerance and Repeatability: The fixture design should account for the required tolerances and
repeatability of the machining or assembly processes. Proper dimensional control, precision
machining, and suitable locating and clamping features are essential to ensure consistent and
accurate results.
11. Maintenance and Inspection: The fixture design should allow for easy maintenance and
inspection. Accessibility to critical components, provision for lubrication, and ease of disassembly
are important factors to consider to ensure efficient upkeep and troubleshooting.
By considering these design considerations, engineers can develop fixtures that optimize
productivity, accuracy, and safety in machining, assembly, or inspection operations. Collaborating
with manufacturing and tooling experts and adhering to relevant industry standards and best
practices can further enhance the effectiveness and reliability of fixture designs.
Q-12 Describe the planning of fixture design.
Ans.
The planning phase of fixture design involves careful consideration and preparation before starting
the actual design process. It entails gathering information, defining objectives, and establishing a
clear roadmap for creating an effective fixture. Here are the key steps involved in the planning of
fixture design:
1. Understand Requirements: Begin by thoroughly understanding the requirements and
specifications of the workpiece and the machining or assembly process. Gather relevant information
such as part drawings, dimensions, tolerances, production volume, and expected cycle time.
2. Analyze Workpiece and Process: Analyze the workpiece geometry, material properties, and the
steps involved in the machining or assembly process. Identify critical features, areas requiring
support or clamping, and any special considerations such as access points, orientations, or tooling
requirements.
3. Determine Fixture Type: Based on the workpiece characteristics and process requirements,
determine the appropriate type of fixture. Common types include milling fixtures, drilling fixtures,
assembly fixtures, welding fixtures, and inspection fixtures. Consider factors such as workpiece
accessibility, clamping needs, and desired level of flexibility.
4. Establish Design Objectives: Clearly define the objectives and expectations for the fixture design.
This includes factors such as accuracy, repeatability, stability, ease of use, modularity, and costeffectiveness. Establishing specific design goals will guide the subsequent design decisions.
5. Conceptualize Fixture Design: Generate initial design concepts by brainstorming and sketching
different ideas. Explore various approaches for workpiece positioning, clamping mechanisms,
locating features, and overall fixture structure. Consider factors such as part accessibility, ease of
setup, and potential limitations.
6. Evaluate Feasibility: Evaluate the feasibility of the conceptual designs based on technical
considerations, manufacturing capabilities, and available resources. Assess the compatibility of the
chosen design concepts with the machining or assembly equipment, tooling, and any existing
fixtures or infrastructure.
7. Conduct Design Reviews: Seek input and feedback from relevant stakeholders, including
manufacturing engineers, tooling experts, operators, and quality control personnel. Conduct design
reviews to ensure that the proposed fixture design meets all requirements and addresses potential
concerns or challenges.
8. Iterative Design Refinement: Refine the fixture design based on the feedback and insights gained
during the design reviews. Incorporate necessary modifications and optimizations to improve
functionality, ease of use, efficiency, and manufacturability.
9. Create Detailed Design: Once the initial concept is refined, proceed to create a detailed design of
the fixture. This involves specifying dimensions, selecting materials, finalizing clamping mechanisms,
and incorporating necessary features such as chip management, coolant provision, and inspection
access.
10. Perform Design Validation: Validate the fixture design through virtual simulations, prototyping,
or testing. Analyze the design for structural integrity, clamping force adequacy, ergonomic
considerations, and any other performance factors. Make necessary adjustments based on the
validation results.
11. Documentation and Communication: Document the fixture design thoroughly, including detailed
drawings, bill of materials (BOM), assembly instructions, and any specific guidelines for setup,
operation, and maintenance. Ensure clear communication of the design specifications and
requirements with the manufacturing and production teams.
By following a systematic planning process, engineers can ensure that the fixture design meets the
desired objectives, aligns with the workpiece and process requirements, and facilitates efficient and
accurate machining or assembly operations.
Q-13 Differentiate between static and dynamic stiffness of machine tool.
Ans.
Static stiffness and dynamic stiffness are two important characteristics of machine tools that describe
their mechanical behavior in different operating conditions. Here's a differentiation between static
and dynamic stiffness:
Static Stiffness:
1. Definition: Static stiffness refers to the ability of a machine tool or structure to resist deformation
or deflection when subjected to a static load or force.
2. Operating Condition: Static stiffness is evaluated when the machine tool is subjected to a constant
load or force without any dynamic or varying components.
3. Measurement: Static stiffness is typically measured by applying a known force to the machine tool
and measuring the resulting displacement or deflection. It quantifies the rigidity or stiffness of the
machine tool under static loading conditions.
4. Importance: Higher static stiffness indicates that the machine tool will experience minimal
deflection or deformation during machining operations, leading to better accuracy, precision, and
stability.
5. Influence: Static stiffness primarily affects the dimensional accuracy, surface finish, and tool life in
machining processes that involve steady-state cutting or when the workpiece is stationary.
Dynamic Stiffness:
1. Definition: Dynamic stiffness refers to the ability of a machine tool or structure to resist
deformation or deflection when subjected to dynamic or time-varying loads, forces, or vibrations.
2. Operating Condition: Dynamic stiffness is evaluated when the machine tool is subjected to varying
forces, impacts, or vibrations caused by cutting forces, acceleration/deceleration, tool
engagement/disengagement, or external disturbances.
3. Measurement: Dynamic stiffness is typically determined through modal analysis or dynamic
testing methods, such as impact testing or frequency response analysis. It characterizes the response
of the machine tool to dynamic or harmonic loading conditions.
4. Importance: Higher dynamic stiffness indicates that the machine tool can effectively absorb and
dampen vibrations, reducing the risk of chatter, improving surface finish, extending tool life, and
enhancing overall machining performance.
5. Influence: Dynamic stiffness is particularly critical in high-speed machining operations, where
rapid changes in cutting forces and vibrations occur. It affects the machine tool's ability to maintain
stability, accuracy, and reliability under dynamic loading conditions.
In summary, static stiffness relates to the machine tool's resistance to deformation under static loads,
while dynamic stiffness focuses on its response to dynamic loads and vibrations. Both static and
dynamic stiffness are essential for ensuring the performance, precision, and stability of machine
tools during various machining operations.
Q-14 Write short note on speed chart.
Ans.
A speed chart, also known as a cutting speed chart or cutting data chart, is a graphical representation
or tabulated data that provides recommended cutting speeds for different machining operations. It
is a valuable reference tool for machinists, engineers, and operators involved in metal cutting
processes. Here's a short note on speed charts:
1. Purpose: The primary purpose of a speed chart is to provide guidelines for determining the optimal
cutting speed for a specific material and machining operation. It helps in achieving efficient metal
removal rates, prolonging tool life, and ensuring good surface finish.
2. Variables: Speed charts take into account several variables that influence cutting speed, including
the material being machined, the type of tooling (e.g., high-speed steel, carbide), the diameter or
size of the tool, and the type of machining operation (e.g., turning, milling, drilling).
3. Cutting Speed: Cutting speed refers to the relative velocity between the cutting tool and the
workpiece surface during a machining operation. It is typically measured in surface feet per minute
(sfm) or meters per minute (m/min). Cutting speed significantly impacts tool life, chip formation,
heat generation, and surface finish.
4. Material Considerations: Speed charts list recommended cutting speeds for various materials such
as metals, alloys, plastics, and composites. Different materials have different hardness, thermal
conductivity, and machinability characteristics, necessitating adjustments in cutting speed for
optimal performance.
5. Machining Operations: Speed charts are typically categorized by machining operations, including
turning, milling, drilling, and reaming. Each operation has its own unique considerations, such as tool
engagement, chip formation, and heat generation, which affect the recommended cutting speed.
6. Tool Selection: Speed charts often provide cutting speed ranges based on the type of tooling used.
For example, different cutting speeds may be recommended for high-speed steel tools compared to
carbide tools. The choice of tool material influences the cutting speed due to variations in tool
strength, heat resistance, and wear characteristics.
7. Consultation and Validation: While speed charts offer valuable guidelines, they are not absolute
values. Factors such as machine rigidity, coolant application, workpiece condition, and operator
experience can influence the actual cutting speed used. It is essential to consult the machine
manufacturer's recommendations and validate the cutting speed through practical testing and
adjustments.
8. Safety Considerations: When utilizing speed charts, it is crucial to prioritize safety. Always follow
appropriate safety guidelines and recommendations to ensure the well-being of operators and
prevent tool breakage or workpiece damage.
Speed charts serve as a convenient reference tool for machinists to quickly determine the
appropriate cutting speeds for different materials and machining operations. However, it is
important to note that other cutting parameters, such as feed rate and depth of cut, also need to be
considered in conjunction with cutting speed for optimal machining performance.
Q-15 What are the different methods of adjusting clearances in slideways.
Ans.
In machine tool slideways, clearances play a crucial role in ensuring smooth and accurate motion
while minimizing friction and wear. Various methods are employed to adjust these clearances and
maintain optimal performance. Here are different methods of adjusting clearances in slideways:
1. Shimming: Shimming involves placing thin metal or composite shims between the sliding surfaces
to adjust the clearance. Shims of varying thicknesses are used to achieve the desired fit and
clearance. Shimming is a common method for adjusting clearances in machine tool slideways,
providing precise control over the clearance adjustments.
2. Gib Adjustment: Gibs are adjustable components that are used to fine-tune the clearance in
slideways. Gibs are typically wedge-shaped or tapered pieces that are positioned between the sliding
surfaces. By adjusting the position or angle of the gibs, the clearance can be increased or decreased.
Gib adjustment is commonly used in machine tool applications, such as lathe cross slides or milling
machine tables.
3. Preload Adjustment: Preload adjustment involves applying a controlled amount of force or tension
to reduce clearances in slideways. This method is commonly used in linear motion systems, such as
ball screws or linear guides. By applying a preloading force, the contact between the sliding surfaces
is increased, minimizing clearance and providing enhanced rigidity and precision.
4. Wear Compensation: Over time, wear can occur in slideways due to continuous use. Wear
compensation methods involve adjusting the clearances to compensate for the wear and restore
optimal performance. This may involve repositioning or replacing components, such as adjusting
screws, gibs, or sliding surfaces, to ensure proper fit and clearance.
5. Hydrostatic or Hydrodynamic Systems: In certain high-precision applications, hydrostatic or
hydrodynamic systems are employed to maintain extremely low clearances and provide enhanced
lubrication and support. These systems utilize a thin film of fluid or air to create a cushioning effect
between the sliding surfaces, effectively reducing clearance and friction.
6. Thermal Compensation: Temperature variations can affect the clearances in slideways. In some
cases, thermal compensation methods are employed to adjust the clearances based on the operating
temperature. This may involve the use of thermal expansion coefficients or temperature sensors to
monitor and adjust the clearances accordingly.
It's worth noting that the specific method of adjusting clearances in slideways depends on the design
and application of the machine tool. Manufacturers often provide guidelines and recommendations
for the appropriate adjustment methods for their specific slideway systems. It is important to follow
these guidelines and consult the machine manufacturer's documentation for accurate and effective
clearance adjustments.
Q-16 Explain the design criteria for machine tool structures.
Ans.
The design of machine tool structures involves considering various criteria to ensure the structural
integrity, stability, and performance of the machine. Here are some key design criteria for machine
tool structures:
1. Stiffness: Stiffness is a critical design criterion for machine tool structures. The structure should
exhibit high stiffness to resist deflections, vibrations, and deformations during machining operations.
A stiff structure helps maintain accuracy, precision, and stability, ensuring that the tool remains in
the desired position and orientation.
2. Damping: Damping refers to the ability of the machine tool structure to dissipate vibrations and
minimize the propagation of dynamic forces. Incorporating damping mechanisms, such as vibrationabsorbing materials, isolation pads, or tuned mass dampers, can help reduce vibrations, chatter, and
noise, leading to improved surface finish, tool life, and overall performance.
3. Stability: Stability is crucial to ensure the machine tool can maintain its position and resist
undesired movements or vibrations. The structure should be designed to resist tipping, rocking, or
any other form of instability that could compromise machining accuracy and safety. Proper weight
distribution, base design, and center of gravity considerations contribute to stability.
4. Material Selection: Choosing appropriate materials is essential for machine tool structure design.
The materials should possess high strength, rigidity, and fatigue resistance to withstand the forces
and stresses encountered during machining. Common materials used include cast iron, steel,
composite materials, or a combination thereof, depending on the specific requirements of the
machine tool.
5. Structural Optimization: Structural optimization techniques, such as finite element analysis (FEA),
can be employed to refine the design and maximize structural performance. By analyzing the stress
distribution, deflection, and natural frequencies, designers can identify areas of high stress or
potential weaknesses and make necessary modifications to improve the structure's strength and
performance.
6. Ergonomics and Accessibility: Machine tool structures should consider ergonomic factors to
ensure operator comfort and accessibility. The design should facilitate easy access to the workpiece,
tooling, controls, and maintenance areas. Proper consideration of ergonomics enhances operator
productivity, reduces fatigue, and improves safety.
7. Thermal Effects: Machine tool structures may experience thermal effects due to heat generated
during machining processes. Design considerations should include the thermal expansion of
materials, heat dissipation, and thermal stability to minimize the impact of temperature changes on
the structural integrity and dimensional accuracy of the machine.
8. Vibration Isolation: To minimize the transmission of vibrations to other components or the
surrounding environment, machine tool structures may incorporate vibration isolation techniques.
These include the use of resilient mounts, damping materials, or structural configurations that
effectively absorb or dissipate vibrations.
9. Rigidity of Joints and Connections: The joints and connections between different structural
components should be designed to ensure rigidity and maintain alignment under load. Proper
fastening methods, such as bolted or welded connections, should be employed to avoid loosening,
shifting, or misalignment that can adversely affect machine tool performance.
10. Safety Considerations: Safety is a paramount concern in machine tool design. The structure
should be designed to withstand the anticipated forces and loads without compromising operator
safety. Incorporating safety features such as machine guards, interlocks, emergency stops, and
ergonomic considerations are essential aspects of the overall machine tool structure design.
Designing machine tool structures requires a comprehensive understanding of the machining
processes, materials, and operational requirements. By addressing these design criteria, engineers
can develop robust and reliable machine tool structures that provide high performance, accuracy,
and safety in various machining applications.
Q-17 Analyze how kinematics helps in designing machine structures. Describe your views with an
example.
Ans.
Kinematics plays a crucial role in designing machine structures as it helps engineers understand and
analyze the motion and behavior of mechanical systems. By studying kinematics, designers can make
informed decisions regarding the structure's geometry, dimensions, and material selection, leading
to optimal machine performance. Here's an analysis of how kinematics aids in designing machine
structures, along with an example:
1. Motion Analysis: Kinematics allows engineers to analyze the motion patterns, velocities,
accelerations, and displacements of machine components. By understanding the desired motions of
the machine, such as linear or rotary movements, designers can determine the structural
requirements to support and facilitate these motions. For example, in the design of a CNC milling
machine, kinematics analysis helps determine the range of linear and rotational movements required
for the tool head and workpiece, which guides the design of the supporting structure.
2. Workspace Determination: Kinematics analysis helps in defining the workspace or the range of
motion that a machine can achieve. By considering the kinematic constraints and limitations, such
as joint angles, link lengths, and clearances, designers can ensure that the machine structure
provides sufficient space and freedom of movement. For instance, in the design of a robotic arm,
kinematics analysis is used to determine the range of motion required for various joints, which
influences the design of the arm structure to accommodate the desired workspace.
3. Linkage Design: Kinematics assists in designing the linkages and mechanisms within the machine
structure. By studying the kinematic relationships between the various links, joints, and actuators,
designers can optimize the structure's geometry and dimensions for smooth and efficient motion
transmission. For example, in the design of a four-bar linkage for a scissor lift, kinematics analysis
helps determine the ideal link lengths and joint angles to achieve the desired lifting motion while
maintaining structural stability.
4. Dynamic Loads: Kinematics analysis provides insights into the dynamic loads and forces acting on
the machine structure during operation. By studying the acceleration, deceleration, and dynamic
forces exerted by moving components, engineers can design the structure to withstand these loads
without excessive deflection or deformation. For instance, in the design of a high-speed spindle for
a milling machine, kinematics analysis helps determine the dynamic forces and vibrations resulting
from the rotational motion, guiding the structural design to ensure sufficient stiffness and stability.
5. Structural Optimization: Kinematics analysis aids in structural optimization by identifying areas of
high stress, potential vibrations, or excessive deflection. By incorporating kinematic data into finite
element analysis (FEA) or computational modeling, engineers can refine the structure's design to
enhance stiffness, reduce weight, and improve overall performance. For example, in the design of a
gantry system for a CNC router, kinematics analysis combined with FEA helps optimize the beam
profiles, support structures, and material selection to ensure adequate stiffness and minimize
deflection during high-speed machining operations.
In summary, kinematics provides valuable insights into the motion, forces, and constraints involved
in machine operation. By leveraging kinematics analysis, designers can make informed decisions
regarding the geometry, dimensions, materials, and structural considerations for machine structures.
This ultimately leads to the development of robust and efficient machine designs that meet the
desired performance requirements.
Q-18 Explain the significance of thermal stresses in pressure vessel design.
Ans.
Thermal stresses play a significant role in the design of pressure vessels. These stresses are induced
by temperature variations and can have a considerable impact on the structural integrity and safety
of the vessel. Here are some key points highlighting the significance of thermal stresses in pressure
vessel design:
1. Differential Expansion: Pressure vessels are often subjected to significant temperature changes
during their operation. Different parts of the vessel, such as the shell, heads, and nozzles, may
experience different rates of expansion or contraction due to variations in temperature. This
differential expansion results in thermal stresses that can potentially exceed the material's yield
strength and lead to structural failure if not properly accounted for in the design.
2. Stress Concentration: Thermal stresses tend to concentrate at points of geometric irregularities or
stress concentration features such as welds, sharp corners, or changes in cross-section. These
localized stress concentrations can significantly weaken the vessel's integrity and increase the risk of
cracks or fractures. Designers need to carefully consider these factors and apply appropriate design
measures to minimize stress concentrations and potential failure points.
3. Fatigue Failure: Thermal cycling due to temperature fluctuations can induce cyclic thermal stresses
in the pressure vessel. This can contribute to fatigue failure, where the repeated loading and
unloading of stresses over time can lead to crack initiation and propagation. Proper consideration of
thermal stresses is essential to ensure that the vessel's design and material selection can withstand
the anticipated number of thermal cycles and prevent premature fatigue failure.
4. Brittle Fracture: In certain materials, such as brittle alloys or low-temperature applications,
thermal stresses can increase the susceptibility to brittle fracture. The combination of low
temperature and high thermal stress levels can exceed the material's fracture toughness, leading to
sudden and catastrophic failure without significant plastic deformation or warning signs. It is critical
to consider the potential for brittle fracture and incorporate appropriate safety margins and material
selection to mitigate this risk.
5. Thermal Relief: To minimize the effects of thermal stresses, pressure vessel design often includes
provisions for thermal relief. This can include the use of expansion joints, bellows, or flexible
connections that accommodate thermal expansion and contraction without subjecting the vessel to
excessive stress. These features help reduce the impact of temperature changes and promote the
overall structural integrity and longevity of the pressure vessel.
6. Codes and Standards: Recognizing the significance of thermal stresses, various industry codes and
standards, such as the ASME Boiler and Pressure Vessel Code, include specific requirements and
guidelines for addressing thermal stresses in pressure vessel design. These codes provide design
formulas, allowable stress limits, and testing requirements to ensure that the vessel can safely
handle the anticipated thermal loading.
In conclusion, considering thermal stresses in pressure vessel design is crucial for ensuring the
structural integrity, longevity, and safety of the vessel. By accounting for differential expansion, stress
concentrations, fatigue failure, brittle fracture, and incorporating appropriate design measures,
engineers can develop robust pressure vessel designs that can withstand the effects of temperature
variations and maintain operational reliability.
Q-19 What do you mean by Autofrettage of thick cylinders?
Ans.
Autofrettage is a process used to enhance the strength and fatigue resistance of thick-walled
cylinders, particularly those used in high-pressure applications. It involves subjecting the cylinder to
internal pressure that exceeds the intended operating pressure, causing plastic deformation and
residual compressive stresses in the cylinder material. This process helps to improve the structural
integrity and increase the maximum allowable operating pressure of the cylinder. Here's a detailed
explanation of autofrettage of thick cylinders:
Thick-walled cylinders, such as pressure vessels or gun barrels, experience significant internal
pressure that can induce high tensile stresses in the cylinder wall. These tensile stresses can lead to
failure, particularly in areas with stress concentrations or flaws. Autofrettage is employed as a
preventive measure to increase the cylinder's strength and reduce the likelihood of failure.
The autofrettage process typically involves the following steps:
1. Initial Elastic Deformation: The thick-walled cylinder is initially subjected to an internal pressure
that is significantly higher than the intended operating pressure. This pressure is maintained for a
specific period, allowing the cylinder material to deform elastically.
2. Plastic Deformation: After the initial elastic deformation, the internal pressure is further increased,
causing the cylinder material to undergo plastic deformation. The material in the inner layers of the
cylinder wall yields and expands outward, while the outer layers remain relatively undeformed.
3. Pressure Release: Once the desired plastic deformation has been achieved, the internal pressure
is released. The cylinder wall undergoes elastic recovery, causing the inner layers to contract and
apply compressive stresses on the remaining material.
The process of autofrettage results in the redistribution of stresses within the cylinder wall, leading
to residual compressive stresses near the inner surface and residual tensile stresses near the outer
surface. These residual compressive stresses significantly enhance the strength of the cylinder by
counteracting the tensile stresses induced by the operating pressure.
The benefits of autofrettage include:
1. Increased Strength: The compressive residual stresses generated through autofrettage increase
the yield strength of the cylinder, allowing it to withstand higher internal pressures without
experiencing plastic deformation or failure.
2. Improved Fatigue Resistance: The compressive stresses resulting from autofrettage also help to
reduce the occurrence and propagation of fatigue cracks. The compressive stresses act to close any
existing cracks, making it more difficult for them to propagate under cyclic loading.
3. Weight Reduction: By increasing the cylinder's strength through autofrettage, it is possible to
reduce the wall thickness and, consequently, the weight of the cylinder. This can lead to cost savings
and improved overall efficiency.
It is important to note that the autofrettage process requires careful consideration of factors such as
material properties, operating conditions, and the desired level of plastic deformation. The process
must be performed within the limits of the material's ductility to avoid excessive deformation or
structural damage.
In summary, autofrettage is a process used to enhance the strength and fatigue resistance of thickwalled cylinders by subjecting them to controlled plastic deformation and generating residual
compressive stresses. This process helps to increase the maximum allowable operating pressure,
improve structural integrity, and extend the service life of the cylinder.
Q-20 Suggest suitable materials for the pressure vessels and justify its selection.
Ans.
The selection of materials for pressure vessels depends on several factors, including the intended
application, operating conditions, required strength, corrosion resistance, and cost considerations.
Here are some commonly used materials for pressure vessels and their justifications for selection:
1. Carbon Steel: Carbon steel, such as ASTM A516 Grade 70, is a widely used material for pressure
vessels due to its excellent strength and affordability. It offers good tensile and yield strength
properties, making it suitable for moderate to high-pressure applications. Carbon steel is also readily
available and easily weldable, making it a cost-effective choice for many industrial applications.
2. Stainless Steel: Stainless steel, particularly austenitic grades such as 304 and 316, is commonly
employed in pressure vessels that require high corrosion resistance. These alloys offer excellent
resistance to a wide range of corrosive environments, including acids, alkaline solutions, and
chlorides. Stainless steel also provides good strength properties and high-temperature resistance,
making it suitable for various process industries.
3. Nickel Alloys: Nickel-based alloys, such as Inconel or Hastelloy, are selected for pressure vessels
that require exceptional resistance to corrosion, high temperatures, and aggressive environments.
These alloys offer superior corrosion resistance to a wide range of chemicals, including acids, alkalis,
and seawater. Nickel alloys maintain their mechanical properties at elevated temperatures, making
them suitable for applications in chemical processing, petrochemical, and offshore industries.
4. Aluminum Alloys: Aluminum alloys, like 5052 or 6061, are lightweight materials with good
strength-to-weight ratios. They are commonly used in pressure vessels where weight reduction is a
significant consideration, such as aerospace and automotive applications. Aluminum alloys offer
excellent corrosion resistance in certain environments and are easily formable, allowing for complex
vessel shapes.
5. Composite Materials: Composite materials, such as carbon fiber-reinforced polymers (CFRP), are
gaining popularity in pressure vessel applications. CFRP offers high strength-to-weight ratios,
excellent corrosion resistance, and design flexibility. Composite pressure vessels are commonly used
in industries like aerospace, automotive, and gas storage, where weight reduction and durability are
critical.
The selection of suitable materials for pressure vessels involves a trade-off between factors such as
strength, corrosion resistance, temperature limitations, cost, and fabrication considerations. It is
essential to carefully evaluate the specific requirements of the application and consult relevant
industry standards and codes (e.g., ASME Boiler and Pressure Vessel Code) to ensure compliance
and safety.
Furthermore, considerations such as compatibility with the contained fluid, operating temperature
range, cyclic loading, and potential for stress corrosion cracking should also be taken into account
when selecting materials for pressure vessels. Consulting with materials engineers and following
established design practices will help in making informed decisions regarding material selection for
pressure vessel applications.
Carbon steel: strength & moderate corrosion resistance
Low-alloy steels: strength at high temperatures
Stainless steels: corrosion resistance
Nickel alloys: corrosion resistance
Copper alloys: seawater resistance
Aluminum: Light, low-temperature toughness
Titanium: seawater, chemical resistance
Refractories: very high temperatures
Non-metallic: corrosion & chemicals
Factors Affecting Selection of Material is as follows:
Process fluids (i.e. a plastic might be perfect for the fluid corrosiveness, but will melt when the
operators ‘steam’ the equipment during cleaning)
Operating temperature
Operating pressure
Fluid Velocity
Contamination of product
Required life of the equipment (May choose to incur shorter life and replace more often)
Cost of the materials of construction (base material + fabrication costs)
Q-21 Sketch and explain in detail the support for the pressure vessel.
Ans.
Support for a pressure vessel is an integral part of its design, ensuring its stability, structural integrity,
and safe operation. The support system helps distribute the weight of the vessel and the contained
fluid, while also accommodating thermal expansion, external loads, and seismic forces. Here is a
detailed explanation of the support types commonly used for pressure vessels:
1. Skirt Support: The skirt support is a cylindrical or conical extension of the pressure vessel's bottom
head or shell. It provides vertical support and stability to the vessel. The skirt is usually welded to
the vessel and extends downward to the foundation or a support structure. The skirt can be designed
with stiffening rings or gussets to increase its strength and resistance to bending moments. It is
commonly used for tall and narrow pressure vessels.
2. Leg Support: Leg supports consist of individual legs or columns that are attached to the bottom
head or shell of the pressure vessel. These legs provide vertical support and allow for the vessel's
elevation above the ground or a support structure. Leg supports are often used for smaller vessels
or vessels that require portability, such as storage tanks or small-scale process vessels.
3. Lug Support: Lug supports involve the use of brackets or lugs attached to the pressure vessel's
shell or heads. These lugs provide attachment points for supporting structures, such as beams or
frames. Lug supports are suitable for vessels that require specialized mounting or attachment
configurations, such as vessels mounted on skids or platforms.
4. Saddle Support: Saddle supports consist of two curved supports or saddles that cradle the
pressure vessel at its bottom portion. The saddle supports help distribute the weight of the vessel
and maintain its stability. The saddles are typically made of structural steel or other load-bearing
materials and are designed to accommodate the vessel's shape and load distribution. Saddle
supports are commonly used for horizontal pressure vessels, such as storage tanks.
Figure 2 Pressure vessel supported at saddle
5. Ring Support: Ring supports involve the use of multiple horizontal rings or hoops that encircle the
pressure vessel. These rings provide support and prevent the vessel from excessive deformation
under internal pressure. Ring supports are especially critical for large-diameter pressure vessels or
vessels with high internal pressures. The rings can be attached to the vessel through welding or
clamping mechanisms and are typically designed to evenly distribute the load along the vessel's
circumference.
In addition to these primary support types, other support elements may be incorporated based on
the specific requirements and design considerations of the pressure vessel. These include anchor
bolts, base plates, guide brackets, seismic restraints, and expansion joints to accommodate thermal
expansion and contraction.
When designing the support system for a pressure vessel, engineers must consider factors such as
the vessel's size, weight, operating conditions, seismic loads, wind loads, and foundation or
structural constraints. Compliance with relevant industry codes and standards, such as the ASME
Boiler and Pressure Vessel Code, is crucial to ensure the support system's adequacy and the overall
safety of the pressure vessel.
Overall, a well-designed support system is essential for maintaining the stability, integrity, and safe
operation of a pressure vessel throughout its service life. It must effectively distribute the loads,
accommodate thermal expansion, and withstand external forces to prevent excessive stresses,
deformation, or failure of the vessel.
Q-22 Discuss about various codes used for design of vessels.
Ans.
Pressure vessels are designed to operate safely at a specific pressure and temperature, technically
referred to as the “Design Pressure” and “Design Temperature”. A vessel that is inadequately
designed to handle a high pressure constitutes a very significant safety hazard. Because of that, the
design and certification of pressure vessels is governed by design codes such as the ASME Boiler and
Pressure Vessel Code in North America, the Pressure Equipment Directive of the EU (PED), Japanese
Industrial Standard (JIS), CSA B51 in Canada, Australian Standards in Australia and other international
standards like Lloyd’s, Germanischer Lloyd, Det Norske Veritas, Société Générale de Surveillance (SGS
S.A.), Lloyd’s Register Energy Nederland (formerly known as Stoomwezen) etc.
It is a standard that provides rules for the design, fabrication, and inspection of boilers and pressure.
This establishes and maintains design, construction, and inspection standards providing for
maximum protection of life and property.
ASME Section VIII: Boiler and Pressure Vessel Code (BPVC)
Division 1 – Rules for Construction of Pressure Vessels
Division 2 – Alternative Rules
Division 3 – Alternative Rules for Construction of High-Pressure Vessels
Several codes and standards are used worldwide for the design of pressure vessels to ensure their
safe and reliable operation. Here are some of the prominent codes commonly employed in the
design of vessels:
1. ASME Boiler and Pressure Vessel Code (BPVC): The ASME BPVC is one of the most widely
recognized codes for the design, construction, inspection, and certification of pressure vessels in the
United States and many other countries. It provides guidelines for various types of vessels, including
boilers, reactors, heat exchangers, and storage tanks. The ASME BPVC consists of several sections,
such as Section VIII for pressure vessels and Section II for materials.
2. European Pressure Equipment Directive (PED): The PED is a European Union directive that
establishes essential safety requirements for pressure equipment, including vessels. It outlines
design, fabrication, inspection, and conformity assessment procedures for pressure vessels intended
for use in Europe. Compliance with the PED is indicated by affixing the CE marking on the vessel.
3. British Standard BS 5500: BS 5500, also known as PD 5500, is a British standard that provides
guidance on the design, manufacture, and inspection of pressure vessels. It covers various types of
vessels, including cylindrical, spherical, and conical vessels. BS 5500 is widely used in the United
Kingdom and has gained international recognition.
4. API Standards: The American Petroleum Institute (API) has developed a range of standards
applicable to pressure vessels used in the oil and gas industry. Notable API standards include API 510
(pressure vessel inspection, rating, repair, and alteration), API 620 (design and construction of large,
welded, low-pressure storage tanks), and API 650 (design and construction of large, welded, lowpressure storage tanks for the petroleum industry).
5. TEMA Standards: The Tubular Exchanger Manufacturers Association (TEMA) provides standards
for the design and construction of heat exchangers, including shell-and-tube and other types of heat
exchangers. These standards cover aspects such as mechanical design, materials, fabrication, and
testing.
6. JIS Standards: The Japanese Industrial Standards (JIS) include specifications for various industrial
products, including pressure vessels. JIS B 8243 is the standard for designing and manufacturing
unfired pressure vessels in Japan. It provides guidelines on design calculations, materials, fabrication,
and inspection.
7. EN Standards: The European Norm (EN) standards cover various aspects of pressure vessel design
and construction. EN 13445 is the standard for unfired pressure vessels and provides requirements
for design, materials, fabrication, testing, and inspection.
These are just a few examples of the codes and standards used for the design of pressure vessels.
The selection of the appropriate code depends on factors such as the geographical location, intended
application, industry requirements, and applicable regulations. It is essential to consult the relevant
code and ensure compliance during the design, fabrication, and operation of pressure vessels to
ensure their safe and reliable performance.
Q-23 Discuss design consideration regarding IBR in brief.
Ans.
Design considerations regarding the Indian Boiler Regulations (IBR) are essential to ensure
compliance with the regulatory requirements for the design, manufacturing, installation, and
operation of boilers and pressure vessels in India. Here are some key design considerations regarding
IBR:
1. Material Selection: IBR specifies the acceptable materials for various components of boilers and
pressure vessels. Designers must carefully select materials that meet the prescribed criteria,
including strength, corrosion resistance, and temperature limitations. Material certificates and
compliance with IBR standards are typically required to demonstrate the suitability of the chosen
materials.
2. Design Calculations: Design calculations play a crucial role in IBR compliance. Designers must
perform calculations to determine critical parameters such as maximum allowable working pressure
(MAWP), minimum required wall thickness, safety margins, and stress levels. These calculations
should follow the formulas and methodologies prescribed by IBR to ensure the structural integrity
and safety of the boiler or pressure vessel.
3. Pressure Parts Design: The design of pressure parts, such as shells, heads, tubes, and nozzles,
should adhere to the guidelines specified in IBR. This includes considerations for dimensions,
minimum thickness requirements, reinforcement requirements, and appropriate safety factors.
Detailed drawings and documentation of the pressure parts, including weld details, are typically
required for IBR certification.
4. Welding Procedures and Qualifications: IBR outlines specific requirements for welding procedures
and qualifications. Designers must ensure that welding procedures comply with the approved IBR
codes and standards. Qualified welders and welding operators should be employed, and proper
welding techniques, inspections, and documentation should be followed to meet IBR requirements.
5. Safety Features: IBR emphasizes the incorporation of safety features to prevent accidents and
ensure safe operation. Designers must consider safety features such as safety valves, pressure relief
devices, level indicators, and control systems to meet the prescribed IBR standards. The design
should include provisions for easy access to these safety devices for maintenance and inspection
purposes.
6. Documentation and Inspection: IBR mandates the preparation and submission of various design
documents, including drawings, calculations, material certificates, welding records, and quality
control documentation. Designers should ensure the availability of accurate and complete
documentation as per IBR requirements. Additionally, regular inspections and audits by IBRapproved inspection agencies are necessary to verify compliance with the regulations.
7. Quality Assurance: Implementing a robust quality assurance program is crucial for IBR compliance.
Designers should establish quality control processes and procedures that cover material
procurement, manufacturing, welding, testing, and inspection. Adherence to the relevant Indian
Standards (IS) and IBR requirements is essential to maintain quality throughout the design,
fabrication, and installation stages.
It is important to note that the above points provide a general overview of the design considerations
related to IBR. Detailed compliance with the specific requirements outlined in the Indian Boiler
Regulations, including amendments and updates, is necessary for each individual project.
Consulting with qualified professionals experienced in IBR compliance and adhering to the guidelines
and standards set forth by the regulatory authority will ensure the successful design and operation
of boilers and pressure vessels in accordance with IBR requirements.
Q-24 Justify the need of structure diagram and ray diagram for design of multi speed Gearbox.
Ans.
The structure diagram and ray diagram are essential tools in the design of a multi-speed gearbox.
They provide a visual representation of the gearbox's internal components, their arrangement, and
the paths of power transmission. Here's a justification for the need of structure and ray diagrams in
designing a multi-speed gearbox:
1. Structure Diagram:
The structure diagram, also known as the exploded view or assembly diagram, illustrates the physical
arrangement and interconnection of the gearbox components. It showcases the gears, shafts,
bearings, and other elements in their relative positions and provides an overview of the gearbox's
internal structure. Here's why the structure diagram is necessary:
a. Component Visualization: The structure diagram allows designers to visualize the arrangement of
gears, shafts, and other components within the gearbox. This helps in understanding the overall
layout, identifying potential interference issues, and ensuring proper assembly.
b. Clearances and Tolerances: By studying the structure diagram, designers can determine the
required clearances between components, such as gears and housing, and establish the necessary
manufacturing tolerances. This ensures smooth operation and prevents unwanted contact or binding
during gear shifting.
c. Accessibility and Serviceability: The structure diagram helps in assessing the accessibility of various
components for maintenance and repair purposes. Designers can ensure that critical parts can be
easily accessed and replaced when necessary, reducing downtime and improving serviceability.
2. Ray Diagram:
The ray diagram, also known as the power flow diagram or kinematic diagram, represents the paths
followed by the power transmission within the gearbox. It shows how the input power from the
engine or motor is transmitted through different gear stages to achieve various output speeds. Here's
why the ray diagram is important:
a. Power Flow Visualization: The ray diagram provides a clear visualization of how power flows from
the input shaft to the output shaft(s) through the different gear stages. This helps designers
understand the torque and speed relationships at each stage and ensures efficient power
transmission.
b. Gear Selection and Ratios: By studying the ray diagram, designers can determine the gear ratios
between different gear pairs and select suitable gear combinations for achieving the desired output
speeds. This ensures proper gear ratio selection to meet the desired performance requirements of
the gearbox.
c. Efficiency Analysis: The ray diagram allows designers to analyze the efficiency of power
transmission at different gear stages. By considering factors such as gear meshing, bearing losses,
and friction, designers can optimize the gear train layout and select appropriate gear types to
minimize energy losses.
d. Noise and Vibration Analysis: The ray diagram aids in analyzing potential noise and vibration issues
within the gearbox. By visualizing the power transmission paths, designers can identify potential
sources of noise and vibration and take measures to minimize them through proper gear design,
shaft alignment, and bearing selection.
In summary, the structure diagram and ray diagram are essential tools in the design of a multi-speed
gearbox. They provide crucial visual representations of the internal structure, component
arrangement, power flow paths, and power transmission characteristics. These diagrams aid
designers in ensuring proper assembly, optimizing gear ratios, improving efficiency, analyzing noise
and vibration issues, and facilitating maintenance and serviceability.
Q-25 Evaluate different design criteria for machine tool structures.
Ans.
Design criteria for machine tool structures are crucial for ensuring their strength, rigidity, durability,
and performance. Here are different design criteria that need to be evaluated for machine tool
structures:
1. Static and Dynamic Stiffness: Machine tool structures should exhibit sufficient static and dynamic
stiffness to withstand cutting forces, vibrations, and other loads encountered during operation. High
stiffness helps maintain accuracy, minimize deflection, and ensure stable cutting performance.
2. Structural Integrity: The machine tool structure must possess structural integrity to withstand
various loads and stresses without experiencing deformation, fatigue, or failure. This involves
selecting appropriate materials, ensuring proper joint design, and conducting thorough structural
analysis to ensure sufficient factor of safety.
3. Damping Capability: Damping is essential to attenuate vibrations generated during machining
processes. Designing the machine tool structure with appropriate damping characteristics helps
absorb vibrations, reduces chatter, and improves surface finish. Damping can be achieved through
the selection of materials with inherent damping properties or through the use of damping
techniques such as viscoelastic materials or tuned mass dampers.
4. Thermal Stability: Machine tool structures should exhibit good thermal stability to minimize the
effects of temperature variations during operation. Thermal expansion, which can lead to
dimensional changes and loss of accuracy, should be carefully considered in the design. Thermal
isolation or thermal compensation techniques may be employed to minimize the impact of thermal
distortions.
5. Accessibility and Ergonomics: The design of machine tool structures should consider accessibility
for operators, maintenance personnel, and tooling. Ergonomic considerations, such as easy access
to workpieces, tool changes, and control interfaces, help enhance productivity, safety, and user
comfort.
6. Vibration Isolation: Machine tool structures should incorporate measures to isolate vibrations that
can adversely affect machining accuracy. This can include the use of vibration isolation mounts or
systems to minimize the transfer of vibrations from the machine structure to the workpiece or
surrounding environment.
7. Precision and Accuracy: Precision and accuracy are fundamental requirements for machine tools.
Design criteria should address factors such as dimensional stability, geometric accuracy, alignment,
and positioning accuracy to ensure the machine tool can consistently achieve the desired machining
tolerances.
8. Modularity and Flexibility: Designing machine tool structures with modularity and flexibility in
mind allows for customization and adaptation to varying machining requirements. Modular designs
enable the integration of additional components, tooling, or subsystems, facilitating versatility and
scalability.
9. Weight Optimization: Minimizing the weight of machine tool structures while maintaining
sufficient strength is beneficial for transportation, installation, and energy efficiency. Designers
should employ lightweight materials and structural optimization techniques to achieve weight
reduction without compromising structural integrity.
10. Serviceability and Maintainability: Considerations for easy servicing, maintenance, and repair
should be incorporated into the design. Access to critical components, provision for easy
replacement, and clear documentation contribute to efficient and cost-effective machine tool
maintenance.
11. Compliance with Standards: Machine tool structures should adhere to relevant industry
standards and regulations, such as ISO, ANSI, or specific machine tool standards. Compliance ensures
compatibility, safety, and facilitates interoperability with other machine tool components and
systems.
In conclusion, the design criteria for machine tool structures encompass static and dynamic stiffness,
structural integrity, damping capability, thermal stability, accessibility, ergonomics, vibration
isolation, precision and accuracy, modularity, weight optimization, serviceability, and compliance
with standards. Evaluating these criteria helps ensure the performance, reliability, and longevity of
machine tools in various industrial applications.
Q-26 How geometric progression is advantageous for the design of gear box?
Ans.
Geometric progression, also known as a logarithmic scale, is advantageous for the design of
gearboxes due to its ability to represent a wide range of values in a compact and visually intuitive
manner. Here are the advantages of using geometric progression in gear design:
1. Size Optimization: Geometric progression allows for the optimization of gear sizes and ratios
within a compact design. By using a logarithmic scale, a small change in the scale corresponds to a
significant change in the ratio, enabling designers to achieve a wide range of gear ratios with
relatively fewer gear sizes.
2. Smooth Transitions: Geometric progression ensures smooth transitions between gear ratios. As
the logarithmic scale represents the ratios with equal spacing, gear transitions can be made in
smaller increments, resulting in smoother gear shifting and reduced shock loads on the transmission
system.
3. Easy Visualization: Geometric progression provides an intuitive visual representation of gear ratios.
By using a logarithmic scale on gear ratio charts or drawings, engineers can easily identify and analyze
the distribution of gear ratios, allowing for efficient design and optimization.
4. Gear Compatibility: The use of geometric progression simplifies the selection and compatibility of
gears within a system. With a logarithmic scale, gears with different sizes and ratios can be chosen
to maintain a consistent and proportional progression, ensuring smooth power transmission
throughout the gearbox.
5. Manufacturing Efficiency: Geometric progression aids in manufacturing efficiency and cost
optimization. By reducing the number of unique gear sizes required, manufacturers can streamline
their production processes, minimize tooling and setup costs, and improve overall manufacturing
efficiency.
6. Performance Flexibility: Geometric progression offers flexibility in gear ratio selection, allowing
designers to tailor the performance characteristics of the gearbox to specific applications. By
adjusting the gear ratios along the logarithmic scale, desired torque, speed, and power outputs can
be achieved, optimizing the performance of the gearbox for different operating conditions.
7. Maintenance and Serviceability: Geometric progression simplifies maintenance and serviceability
of gearboxes. With a consistent logarithmic scale, replacement gears can be easily identified and
selected based on the existing gear ratios, ensuring compatibility and minimizing downtime during
maintenance or repairs.
It is important to note that while geometric progression provides advantages in gear design, other
factors such as torque capacity, gear tooth profiles, material selection, and manufacturing tolerances
also need to be considered to ensure the overall functionality and reliability of the gearbox.
In conclusion, geometric progression offers advantages in the design of gearboxes by optimizing size,
enabling smooth transitions, providing easy visualization, enhancing gear compatibility, improving
manufacturing efficiency, offering performance flexibility, and simplifying maintenance and
serviceability. These benefits contribute to the design of efficient, compact, and reliable gearboxes
for various industrial applications.
Q-27 Evaluate type and function of fixture.
Ans.
Fixtures are essential tools used in manufacturing and machining processes to hold workpieces
securely and accurately during various operations. They come in different types and serve specific
functions based on the requirements of the workpiece and the machining process. Here is an
evaluation of the types and functions of fixtures:
1. Vise Fixture:
- Function: Vise fixtures are commonly used in milling, drilling, and grinding operations. They
securely hold workpieces in place using adjustable jaws that clamp the workpiece from the sides.
Vise fixtures provide stability and allow for precise positioning and alignment of the workpiece.
2. Collet Fixture:
- Function: Collet fixtures are used to hold cylindrical workpieces, such as rods or tubes, during
machining operations. They utilize a collet—a specialized holding device—to grip the workpiece
firmly. Collet fixtures provide concentricity and accuracy, making them suitable for high-precision
operations like turning or machining small-diameter components.
3. Indexing Fixture:
- Function: Indexing fixtures are designed to facilitate the machining of multiple sides or angles of a
workpiece without the need for repositioning. They allow for precise rotational movement or
indexing of the workpiece at predetermined intervals. Indexing fixtures are commonly used in
milling, drilling, or machining operations where multiple operations can be performed sequentially.
4. Jig Fixture:
- Function: Jig fixtures are specialized tools used for guiding and supporting cutting tools during
drilling, boring, or tapping operations. They ensure accurate hole placement, depth, and alignment.
Jig fixtures often incorporate bushings or drill guides to guide the cutting tool and maintain precision.
5. Modular Fixture:
- Function: Modular fixtures provide flexibility and adaptability for holding various workpiece shapes
and sizes. They consist of standardized components, such as clamps, bases, and supports, which can
be rearranged or reconfigured to accommodate different workpieces. Modular fixtures are costeffective and versatile, making them suitable for production environments with frequent
changeovers.
6. Welding Fixture:
- Function: Welding fixtures are designed to securely hold and position workpieces during welding
operations. They provide stability, alignment, and accessibility for the welding process. Welding
fixtures ensure consistent joint quality, minimize distortion, and improve welding efficiency.
7. Assembly Fixture:
- Function: Assembly fixtures are used in assembly operations to hold and position components
during the assembly process. They provide support, alignment, and easy access for assembly tasks,
ensuring accurate component fitment and reducing assembly errors.
8. Inspection Fixture:
- Function: Inspection fixtures are designed to hold workpieces in a fixed position for quality control
and inspection purposes. They provide precise reference points, datum surfaces, and access for
measurement tools, allowing for accurate dimensional verification and quality assurance.
9. Specialized Fixtures:
- Function: Specialized fixtures are custom-designed fixtures tailored to specific workpiece shapes,
sizes, or machining requirements. They are often used for complex or unique workpieces that require
specialized support, clamping, or positioning. These fixtures are created to address specific
challenges and ensure optimal accuracy and productivity.
Each type of fixture serves a specific function, providing stability, accuracy, positioning, and
accessibility for machining, assembly, welding, or inspection operations. The selection of the
appropriate fixture type depends on the specific requirements of the workpiece, the machining
process, and the desired level of precision and efficiency.
Q-28 Describe any two Locating components for fixture.
Ans.
Here are descriptions of two commonly used locating components in fixtures:
1. Locating Pins:
Locating pins, also known as alignment pins or locating dowels, are cylindrical components used to
precisely position and locate workpieces within a fixture. They typically consist of a head and a shank
that is inserted into a pre-drilled hole in the workpiece or fixture plate. Here are some key features
and functions of locating pins:
- Precise Positioning: Locating pins ensure accurate alignment and positioning of the workpiece
within the fixture. They provide a fixed reference point for establishing the desired orientation and
location of the workpiece.
- Repeatability: Locating pins enable consistent and repeatable positioning of workpieces during
multiple operations. They allow for quick and reliable setup by providing a reliable reference point
for consistent alignment.
- Removability: Locating pins can be easily inserted or removed from the workpiece or fixture,
facilitating efficient changeover and repositioning of different workpieces. This enhances the
flexibility and versatility of the fixture.
- Various Designs: Locating pins come in different designs, such as cylindrical pins, diamond pins, or
conical pins, depending on the specific application requirements. The choice of pin design depends
on factors like the workpiece shape, accuracy requirements, and desired level of clamping force.
2. Locating Blocks:
Locating blocks, also known as fixture blocks or V-blocks, are solid or adjustable components used
to hold and position workpieces in a fixture. They provide stable support and precise location for the
workpiece. Here are some key features and functions of locating blocks:
- Stable Positioning: Locating blocks provide a stable and secure platform for holding the workpiece.
They ensure accurate and repeatable positioning by establishing contact with specific reference
surfaces or edges of the workpiece.
- Multiple Contact Points: Locating blocks typically have two or more contact surfaces designed to
match the contours or edges of the workpiece. These contact surfaces ensure proper alignment and
prevent unwanted movement or rotation during machining or assembly operations.
- Adjustability: Some locating blocks feature adjustable elements, such as sliding or swiveling jaws,
to accommodate different workpiece sizes or shapes. This allows for versatility in holding various
workpieces within the same fixture.
- Material Variety: Locating blocks are commonly made from hardened steel or other rigid materials
to provide stability and durability. They may also feature surface treatments or coatings to enhance
wear resistance and reduce friction between the block and the workpiece.
- Compatibility: Locating blocks are often designed to work in conjunction with other fixture
components, such as clamps, to provide a comprehensive and secure workholding solution. They
ensure proper alignment and support for the workpiece during machining or assembly processes.
Locating pins and locating blocks are essential components in fixtures, providing precise positioning,
stable support, and repeatable alignment for workpieces. These components play a crucial role in
achieving accuracy, minimizing setup time, and ensuring consistent results in machining, assembly,
or inspection operations.
Q-29 Can you justify need of an Assembly Fixture with a suitable example?
Ans.
Let's consider an example to justify the need for an assembly fixture:
Example: Automobile Engine Assembly
In the assembly process of an automobile engine, numerous components need to be accurately
positioned, aligned, and joined together. This process involves multiple steps, such as installing
pistons, connecting rods, cylinder heads, crankshafts, and various other parts.
Justification for Assembly Fixture:
1. Alignment and Positioning: An assembly fixture is crucial to ensure precise alignment and
positioning of the engine components. It provides dedicated locators, clamps, and support structures
that hold the components in their correct positions, allowing for accurate assembly.
2. Improved Efficiency: The use of an assembly fixture enhances efficiency by streamlining the
assembly process. With proper locators and guides, the fixture eliminates the need for manual
measurements and adjustments, reducing human error and saving valuable time during assembly.
3. Consistency and Quality: An assembly fixture ensures consistent and high-quality assembly. By
providing predefined positions and clear guidance for component placement, it helps maintain
uniformity in assembly, resulting in reliable and predictable engine performance.
4. Ergonomics and Safety: Assembly fixtures are designed with ergonomic considerations, providing
optimal accessibility and ease of assembly for operators. They reduce strain on assembly personnel,
enhance safety by securing heavy or complex components, and minimize the risk of accidents or
injuries.
5. Compatibility and Standardization: Assembly fixtures are often designed to be compatible with
standardized components, ensuring compatibility with different engine variants. This promotes
interchangeability and enables efficient assembly line setups, reducing costs associated with
specialized tooling for each engine configuration.
6. Error Detection and Prevention: An assembly fixture can incorporate features to detect and
prevent assembly errors. For example, it can include sensors or gauges that verify the correct seating
of components or the presence of required fasteners, preventing critical assembly mistakes.
7. Versatility and Adaptability: Assembly fixtures can be designed with modular or adjustable
features to accommodate variations in engine designs or options. This allows for flexibility in
assembly, facilitating the production of different engine models or configurations on the same
assembly line.
In conclusion, the assembly of complex products such as automobile engines require the use of
assembly fixtures. These fixtures provide precise alignment, positioning, and support for
components, improving efficiency, consistency, and quality of the assembly process. They enhance
ergonomics, promote safety, facilitate error detection and prevention, and offer versatility to
accommodate variations in product design. Overall, assembly fixtures play a vital role in achieving
accurate and efficient assembly operations, resulting in reliable and high-performance end products.
Q-30 What are the different methods of adjusting clearances in slide ways?
Ans.
There are several methods used to adjust clearances in slideways, which are essential for ensuring
smooth and precise movement of machine components. Here are some common methods:
1. Shimming:
Shimming involves inserting thin metal or composite shims between the slideway surfaces to adjust
the clearance. Shims are available in various thicknesses and can be stacked or removed as needed
to achieve the desired clearance. Shimming is a widely used method for adjusting clearances in
slideways and provides precise control over the clearance adjustment.
2. Gib Adjustment:
Gib adjustment is commonly used in dovetail slideways. It involves adjusting the position of the gib
strip, which is a thin metal plate placed between the sliding surfaces to control the clearance. By
loosening the gib screws, the gib strip can be moved to increase or decrease the clearance. Once the
desired clearance is achieved, the screws are tightened to secure the gib strip in place.
3. Wear Adjustment:
In some cases, the clearance in slideways can be adjusted by compensating for wear. As the slideways
are subjected to usage over time, wear can occur, resulting in increased clearance. This can be
addressed by selectively adding material or building up worn surfaces using techniques like welding
or thermal spraying. The built-up material helps reduce the clearance and restore the proper fit and
functionality of the slideways.
4. Preloading:
Preloading is a method used to reduce clearance in slideways by applying a controlled force or
tension. This is achieved by using springs, hydraulic systems, or other mechanisms to exert a constant
or adjustable force on the slideway components. Preloading helps minimize play or backlash in the
system, resulting in improved accuracy and responsiveness.
5. Slideway Replacement:
In cases where the clearance cannot be adjusted using the above methods or when the wear is
extensive, the ultimate solution may involve replacing the entire slideway. This typically requires
dismantling the machine and installing a new slideway with the appropriate dimensions and
clearances.
It is important to note that the specific method used to adjust clearances in slideways depends on
the design of the machine, the type of slideway system, and the level of precision required. Proper
adjustment of clearances is crucial for maintaining the performance and accuracy of the machine, as
excessive clearance can lead to decreased precision, increased wear, and reduced overall
functionality.
Q-31 Explain in brief about the modular structures used in machine tools.
Ans.
Modular structures in machine tools refer to a design approach where the machine is constructed
using standardized modules or components that can be easily interchanged or reconfigured. This
modular concept offers flexibility, adaptability, and scalability in machine tool design and
construction. Here are some key points about modular structures in machine tools:
1. Standardized Modules: Modular structures involve the use of standardized modules or building
blocks, such as frames, beds, columns, slides, and tooling interfaces. These modules are designed to
have consistent dimensions, interfaces, and mounting points, allowing for easy interchangeability.
2. Flexibility and Adaptability: Modular structures enable machine tool manufacturers to offer a
range of machine configurations and options using a common set of modules. By combining or
modifying the modules, different machine sizes, functionalities, and capabilities can be achieved to
meet specific customer requirements.
3. Easy Assembly and Integration: The use of standardized modules simplifies the assembly and
integration process of the machine tool. The modules can be pre-manufactured, tested, and stocked,
allowing for faster production and reduced lead times. They can also be easily replaced or upgraded
as needed, minimizing downtime during maintenance or upgrades.
4. Scalability and Expansion: Modular structures allow for scalability and expansion of the machine
tool. Additional modules can be added or removed to increase or decrease the machine's size,
capacity, or functionality. This adaptability makes modular structures suitable for accommodating
future growth or changes in manufacturing requirements.
5. Cost Efficiency: Modular structures offer cost efficiencies in machine tool manufacturing. The
standardized modules can be mass-produced, resulting in economies of scale. They also simplify the
design process and reduce engineering and development costs. Furthermore, modular structures
facilitate easier maintenance and repair, as modules can be individually serviced or replaced without
extensive disassembly of the entire machine.
6. Interchangeability and Interoperability: Modular structures promote interchangeability and
interoperability of components within a machine tool. This means that components such as spindles,
tooling, or automation systems designed for one modular machine can be utilized in other
compatible machines, enhancing flexibility and reducing costs.
7. Common Interfaces and Controls: Modular structures often incorporate common interfaces and
control systems, making it easier to integrate different modules and subsystems. This compatibility
simplifies communication and coordination between various components of the machine, facilitating
efficient operation and control.
In summary, modular structures in machine tools offer flexibility, adaptability, scalability, and cost
efficiencies. By using standardized modules, machine tool manufacturers can easily customize
machine configurations, streamline assembly and integration, and provide a versatile platform for
future expansion and upgrades. The modular approach enhances productivity, reduces
manufacturing costs, and enables efficient utilization of resources in the machine tool industry.
Q-32 Enlist various laws of stepped regulation of speed in speed box. Explain any one in detail.
Ans.
In a speed box or stepped speed regulation system, the speed of a machine or mechanism is
controlled by changing gears or transmission ratios. This allows for different speed settings or steps
to be achieved. The laws of stepped regulation define the relationship between the input speed and
the output speed of the system. Here are some common laws of stepped regulation:
1. Constant Speed Law:
According to the constant speed law, the output speed remains constant regardless of the input
speed. This means that the speed box provides a fixed speed reduction or increase ratio, maintaining
a consistent output speed relative to the input speed. This law is typically used in applications where
a specific output speed needs to be maintained regardless of changes in the input speed.
2. Geometric Progression Law:
The geometric progression law states that the ratio of the output speed to the input speed remains
constant for each step in the speed box. In other words, the change in speed between consecutive
steps follows a geometric progression. For example, if the speed box has four steps, the output
speeds may be in a geometric progression of 1:2:4:8, where each step doubles the output speed
compared to the previous step. This law allows for a systematic and predictable change in speed
across the speed box.
3. Arithmetic Progression Law:
In contrast to the geometric progression law, the arithmetic progression law states that the change
in speed between consecutive steps in the speed box follows an arithmetic progression. This means
that the difference in speed between each step remains constant. For example, if the speed box has
four steps, the output speeds may be in an arithmetic progression of 1000:1200:1400:1600, where
each step increases the output speed by a constant value of 200. This law provides a linear and
evenly distributed change in speed across the speed box.
4. Specific Application Laws:
In some cases, the laws of stepped regulation may be tailored to specific applications or
requirements. For example, in certain machines or mechanisms, there may be specific speed ratios
or relationships between input and output speeds that need to be maintained for optimal
performance. The laws of stepped regulation can be customized to achieve these specific speed
requirements, ensuring efficient operation and desired functionality.
It's important to note that the selection and design of the laws of stepped regulation depend on the
specific application, the desired speed ranges, and the functional requirements of the machine or
mechanism. The laws of stepped regulation allow for a controlled and adjustable change in speed,
enabling the machine or mechanism to operate at different speeds according to the specific needs
of the application.
Q-33 Explain in brief design procedure of speed gear box.
Ans.
The design procedure for a speed gearbox involves several steps to ensure that the gearbox meets
the desired requirements and performs efficiently. Here is a brief overview of the design procedure
for a speed gearbox:
1. Define Design Requirements:
Start by defining the specific requirements of the speed gearbox, including the input speed range,
output speed range, torque capacity, power requirements, and any other specifications specific to
the application. These requirements will guide the entire design process.
2. Determine Gear Arrangement:
Select the appropriate gear arrangement for the speed gearbox based on the requirements and
constraints. Common gear arrangements include spur gears, helical gears, bevel gears, and planetary
gears. Consider factors such as efficiency, compactness, noise level, and load distribution when
choosing the gear arrangement.
3. Calculate Gear Ratios:
Determine the required gear ratios to achieve the desired output speeds for each step of the speed
gearbox. Consider the desired speed steps and the speed reduction or increase required for each
step. Use gear ratio formulas to calculate the required gear tooth counts for each gear pair.
4. Sizing of Gears and Shafts:
Based on the calculated gear ratios, determine the sizes of the gears and shafts. Consider factors
such as torque capacity, bending and contact stresses, gear tooth strength, and deflection. Ensure
that the gears and shafts can handle the transmitted torque and meet the safety factors and design
criteria.
5. Bearing Selection:
Select suitable bearings for supporting the gears and shafts. Consider factors such as load capacity,
stiffness, alignment requirements, and operational conditions. Choose appropriate rolling element
or plain bearings to ensure smooth and reliable operation of the gearbox.
6. Design Housing and Mounting:
Design the gearbox housing or casing to provide structural support and proper alignment for the
gears and shafts. Consider factors such as rigidity, ease of assembly and disassembly, access for
maintenance, and provisions for lubrication and cooling.
7. Lubrication and Sealing:
Determine the lubrication requirements for the gearbox to ensure proper gear and bearing
performance. Select the appropriate lubricant type and determine the lubrication method, such as
splash lubrication or forced circulation. Also, incorporate effective sealing mechanisms to prevent
leakage and contamination.
8. Analysis and Validation:
Perform various analyses, such as stress analysis, gear mesh analysis, and efficiency calculations, to
verify the design and ensure that it meets the performance and durability requirements. Use
simulation tools and software to evaluate the gearbox's performance under different operating
conditions.
9. Prototype Development and Testing:
Build a prototype of the speed gearbox based on the finalized design. Conduct thorough testing to
validate the gearbox's performance, including load testing, endurance testing, and efficiency
measurement. Analyze the test results and make any necessary design modifications.
10. Production and Quality Control:
Once the design and prototype have been successfully tested, proceed to the production stage.
Implement proper quality control measures to ensure consistent manufacturing of the gearboxes,
adhering to design specifications and meeting the required standards.
The design procedure for a speed gearbox requires a comprehensive understanding of gear theory,
mechanical engineering principles, and manufacturing processes. It is important to consider factors
such as efficiency, reliability, durability, and ease of maintenance throughout the design process to
develop a high-performance and reliable speed gearbox.
Q-34 State the functions of spindle units and justify the same.
Ans.
The spindle unit is a critical component in machine tools and serves several important functions.
Here are the key functions of spindle units along with their justifications:
1. Rotational Power Transmission: The primary function of a spindle unit is to transmit rotational
power from the motor to the cutting tool or workpiece. The spindle converts the rotary motion from
the motor into axial rotation, allowing the cutting tool to perform operations such as drilling, milling,
or turning. This function is essential for the machining process as it enables the tool to remove
material and shape the workpiece.
Justification: The rotational power transmission function of the spindle unit is crucial for achieving
efficient and accurate machining operations. It enables the precise control of cutting forces, speeds,
and feeds, resulting in high-quality surface finish, dimensional accuracy, and productivity. Without a
properly functioning spindle unit, the machine tool would not be able to perform machining
operations effectively.
2. Speed Control: The spindle unit allows for speed control of the cutting tool or workpiece. By
adjusting the speed of the spindle, operators can optimize the cutting conditions for different
materials, tool sizes, and machining operations. Speed control is essential for achieving the desired
cutting speed, ensuring efficient material removal, minimizing tool wear, and maximizing
productivity.
Justification: Different materials and machining operations require specific cutting speeds to achieve
optimal results. By providing speed control, the spindle unit enables operators to adapt to varying
requirements, such as high-speed machining, precision machining, or heavy-duty cutting. This
flexibility enhances the versatility and performance of the machine tool, allowing for a wide range
of machining applications.
3. Accuracy and Precision: The spindle unit plays a crucial role in maintaining accuracy and precision
during machining operations. It ensures concentricity between the spindle axis and the cutting tool,
minimizing runout and eccentricity. This precision is essential for achieving tight tolerances, accurate
positioning, and consistent part quality.
Justification: Accuracy and precision are critical in machining applications, particularly in industries
such as aerospace, automotive, and medical manufacturing. The spindle unit's ability to maintain
concentricity and minimize runout ensures that the cutting tool follows the desired tool path
accurately, resulting in precise machined components. High levels of accuracy and precision are
essential for meeting strict quality requirements and minimizing rework or scrap.
4. Load Handling: Spindle units are designed to handle various loads encountered during machining
operations. They must be capable of withstanding both axial and radial forces generated by cutting
forces, tool engagement, and workpiece weight. The spindle unit should be rigid and robust to
maintain stability and prevent deflection or vibration during operation.
Justification: Machining operations involve significant cutting forces, especially when removing
material or performing heavy-duty cutting. The spindle unit's ability to handle these loads is crucial
for maintaining stability, preventing tool chatter, and achieving consistent cutting performance. A
robust and well-designed spindle unit enhances the machine tool's reliability and extends its
operational life.
In summary, the functions of spindle units, including rotational power transmission, speed control,
accuracy and precision, and load handling, are essential for the successful operation of machine
tools. These functions contribute to efficient material removal, precise machining, and high-quality
finished products. The design and performance of the spindle unit directly impact the overall
functionality and productivity of the machine tool.
Q-35 Why vessel openings require reinforcement? Explain the design of openings in pressure vessel
by area for area method for compensation.
Ans.
Vessel openings, such as nozzles or connections, require reinforcement in pressure vessels to ensure
the structural integrity and prevent failure at those points. The design of openings in pressure vessels
follows specific guidelines to ensure that the stress concentrations caused by the openings are
adequately compensated for. One method used for the design of vessel openings is the Area for Area
method, which involves compensating the reduced material area caused by the opening by adding
an equivalent reinforcement area.
The need for reinforcement in vessel openings can be explained as follows:
1. Stress Concentration: Openings in pressure vessels create stress concentrations around their
edges. The abrupt change in geometry and the presence of high-stress gradients can lead to localized
stress concentrations. These stress concentrations can result in premature failure or fatigue crack
initiation if not appropriately addressed.
2. Material Weakening: The material surrounding the opening is weakened due to the removal of
material for the opening itself. This reduction in material area reduces the overall structural capacity
of the vessel in the vicinity of the opening. The opening can act as a stress raiser, leading to stress
concentrations and potential failure.
To compensate for the reduction in material area and to maintain the required strength, the design
of vessel openings follows the Area for Area method. Here's how the design is carried out:
1. Determine Equivalent Reinforcement Area: The first step is to determine the equivalent
reinforcement area needed to compensate for the reduction in material area caused by the opening.
This is done by calculating the stress intensification factor (Kt) associated with the opening and then
finding the equivalent reinforcement area based on the allowable stress and the stress concentration
factor (Kf) for the material.
2. Determine Reinforcement Shape and Location: Based on the required equivalent reinforcement
area, the shape and location of the reinforcement are determined. The reinforcement can take the
form of a pad, a neck, or other configurations depending on the specific requirements of the vessel
and the opening. The reinforcement should be located in such a way that it effectively redistributes
the stress and provides structural support.
3. Welding or Attachment of Reinforcement: The reinforcement is typically attached to the vessel by
welding or other suitable methods. The welding procedure and techniques should comply with
relevant codes and standards to ensure proper bonding and strength.
4. Strength Analysis: Once the reinforcement is added, a strength analysis is performed to assess the
stress distribution and ensure that the stresses are within acceptable limits. Finite element analysis
(FEA) or other analytical methods can be used to evaluate the stress patterns and verify the
effectiveness of the reinforcement in reducing stress concentrations.
By applying the Area for Area method, the design of vessel openings in pressure vessels ensures that
the stress concentrations caused by the openings are adequately compensated for. The equivalent
reinforcement area adds strength and redistributes the stress, preventing localized failure and
maintaining the overall structural integrity of the pressure vessel.