POE – Review Sheet 3
Lesson 2.2 Material Properties - Overview
Preface
Material properties are an important piece of information that engineers rely on when selecting the best material for a
design solution. For instance in the 1988 Challenger space shuttle disaster, an o-ring seal failed, causing the death of
seven astronauts. A misunderstanding about the limits of a material led to this accident.
Engineers often deal with the design of useful products that require materials with certain characteristics or properties.
Complexity is increased when we consider that new materials are constantly being developed, and their application in
new products drives economic growth. Engineers, therefore, must know how to make sense of the multitude of different
materials available. When existing materials don’t provide the desired properties, engineers create new materials called
synthetics. Synthetic materials allow engineers to be extremely innovative when designing solutions to society’s needs.
Sometimes the focus isn’t on the creation of a new material, but on the creation of advanced recycling technology. Nike is
one of several corporations assisting engineers with innovative recycling technology. For instance, Nike has worked with
engineers to develop a method of recycling athletic shoes. The recycled shoes are ground up and used for the production
of basketball courts, tracks, playgrounds, etc.
This lesson is designed to provide students with an opportunity to investigate the basic categories and properties of
materials. Students will discover how products are made and how they are recycled once they are no longer useful.
Understandings
1. Materials are the substances in which all things are made.
2. Materials are composed of elements and area categorized by physical and chemical properties.
3. Materials consist on pure elements, compounds and mixtures and are typically classified as metallic, ceramic,
organic, polymeric, and composite.
4. Material properties including recyclability and cost are important considerations for engineers when choosing
appropriate materials for a design.
5. Material selection is based upon mechanical, thermal, electromagnetic, and chemical properties.
6. Raw materials undergo various manufacturing processes in the production of consumer goods.
Knowledge and Skills
It is expected that students will:

Investigate specific material properties related to a common household product.

Conduct investigative non-destructive material property tests on selected common household product including
testing for continuity, ferrous metal, hardness, and flexure.

Calculate weight, volume, mass, density, and surface area of selected common household product

Identify the manufacturing processes used to create the selected common household product.


Identify the recycling codes.
Promote recycle using current media trends.
Essential Questions
1. How does an engineer predict the performance and safety for a selected material?
2. What are the advantages and disadvantages of utilizing synthetic materials designed by engineers?
3. What ethical issues pertain to engineers designing synthetic materials?
4. What did you learn about the significance of selecting materials for product design?
5. How can an existing product be changed to incorporate different processes to make it less expensive and provide
better performance?
6. How does an engineer decide which manufacturing process to use for a given material?
7. How do the recycling codes and symbols differ from state to state?
Lesson 2.2 Material Properties - Key Terms
Term
Definition
Additive Process
The process of creating an object by adding small pieces or layers together to make
product.
Ceramic
Of or relating to the manufacture of any product (as earthenware, porcelain, or brick
essentially from a nonmetallic mineral (as clay) by firing at a high temperature.
Codes
A systemized body of laws; a set of principles, as of ethics.
Composite
Solid material which is composed of two or more substances having different physic
characteristics and in which each substance retains its identity while contributing de
properties to the whole; especially, a structural material made of plastic within which
fibrous material (as silicon carbide) is embedded.
Decision Matrix
A tool for systematically ranking alternatives according to a set of criteria.
Finishing
Machining a surface to size with a fine feed produced in a lathe, milling machine, or
Forming
A process that changes the size and shape of a material by a combination of force a
shaped form.
Liability
Anything for which a person is legally bound or responsible.
Manufacturing
To make into a product suitable for use; to make from raw materials by hand or by
machinery; to produce according to an organized plan and with division of labor.
Material
The elements, constituents, or substances of which something is composed or can
made; matter that has qualities which give it individuality and by which it may be
categorized.
Mechanical Properties
Those properties of a material that reveal the elastic and inelastic reaction when forc
applied, or that involve the relationship between stress and strain; for example, the m
of elasticity, tensile strength, and fatigue limit.
Metals
Any of various opaque, fusible, ductile, and typically lustrous substances that are go
conductors of electricity and heat.
Physical Properties
Properties other than mechanical properties that pertain to the physics of a material
usually be measured without the application of force.
Polymers
Any of numerous natural and synthetic compounds of usually high molecular weight
consisting of up to millions of repeated linked units, each a relatively light and simple
molecule.
Product Life Cycle
Stages a product goes through from concept and use to eventual withdrawal from th
marketplace.
Raw Material
Crude or processed material that can be converted by manufacture, processing, or
combination into a new and useful product; something with a potential for improvem
development, or elaboration.
Recycling
Returning to an original condition. The extraction and recovery of valuable materials
scrap or other discarded materials.
Subtractive
Processes that remove material to change the size, shape, or surface of a part. The
two groups of separating processes: machining and shearing.
Synthetic
Produced by the combining of parts or elements to form a whole, rather than of natu
origin; not real, artificial.
1. Structure
•
•
•
Crystal Lattice molecular structure
Caused by formation of metallic bonds
Easy flow of electrons throughout
2. Bonding
• Low number of valence electrons
• Shells overlap to form a “sea” of electrons
• Electrons are free moving between valence shells
• Movement of electrons holds molecules together
• Attraction in metallic bonds is between the positive metal ions in the lattice and the “sea” of electrons
3. General Information
•
Metals are pure elements which comprise about three-fourths of the periodic table
•
Few are used in their pure form because of:
a) Hardness; too hard or too soft
b) Cost; scarcity of element
c) Engineers need certain characteristics that can only be accomplished by a blending of basic
elements (synthetic materials). For example, exercise clothing.
• Metallic materials include alloys, which are combinations of metals and other elements.
Lesson 2.3 Material Testing - Overview
Preface
Material Testing is a critical process that determines whether a product is reliable, safe, and predictable in function.
Material testing is basically divided into two major categories: destructive testing and nondestructive testing. Destructive
testing is defined as a process where a material is subjected to a load in a manner that will ultimately cause the material
to fail. Machines have been developed specifically to conduct destructive testing. These machines exert force on the
sample and record information such as resulting deformation, the amount of stress that builds up inside the sample,
elastic behavior, strength, etc. When non-destructive testing is performed on a material, the part is not permanently
affected by the test. The part is usually still serviceable. The purpose of non-destructive testing is to determine whether
the material contains imperfections.
Over many years, tests have been developed for measuring the common properties of engineering materials, including
acoustical, electrical, magnetic, physical, optical, and thermal properties. But why is material testing so significant?
Understandings
1. Engineers utilize a design process and mathematical formulas to solve and document design problems.
2. Material testing aids in determining a product’s reliability, safety, and predictability in function.
3. Engineers perform destructive and non-destructive tests on material specimens for the purpose of identifying and
verifying the properties of various materials.
4. Material testing provides a reproducible evaluation of material properties.
5. Tensile testing data is used to create a test sample stress strain curve.
6. Stress strain data points are used to identify and calculate sample material properties including elastic range,
proportional limit, modulus of elasticity, elastic limit, resilience, yield point, plastic deformation, ultimate strength,
failure, and ductility.
Knowledge and Skills
It is expected that students will:

Utilize a five-step technique to solve word problems.

Obtain measurements of material samples.


Tensile test a material test sample.
Identify and calculate test sample material properties using a stress strain curve.
Essential Questions
1. Why is it critical for engineers to document all calculation steps when solving problems?
2. How is material testing data useful?
3. Stress strain curve date points are useful in determining what specific material properties?
4.
Lesson 2.3 Material Testing - Key Terms
Term
Definition
Axial Stress
A force with its resultant passing through the centroid of a particular section and being
perpendicular to the plane of the section.A force in a direction parallel to the long axis of
structure.
Breaking Stress
The stress required to fracture a material whether by compression, tension, or shear.
Compression
When a material is reduced in volume by the application of pressure; the reciprocal of th
modulus.
Deformation
Any alteration of shape or dimensions of a body caused by stresses, thermal expansion
contraction, chemical or metallurgical transformations, or shrinkage and expansions due
moisture change.
Destructive Testing
Test methods used to examine an object, material, or system causing permanent damag
usefulness.
Elastic Limit
Maximum stress that a material will withstand without permanent deformation.
Elongation
The fractional increase in a material’s length due to stress in tension or thermal expansio
Factor of Safety
The ratio of actual strength to required strength.
Failure Point
Condition caused by collapse, break, or bending, so that a structure or structural elemen
no longer fulfill its purpose.
Fatigue
The loss of the load-bearing ability of a material under repeated load application, as opp
a single load.
Hooke’s Law
The law stating that the stress of a solid is directly proportional to the strain applied to it.
Modulus of Elasticity
The ratio of the increment of some specified form of stress to the increment of some spe
form of strain, such as Young's modulus, the bulk modulus, or the shear modulus. Also k
as coefficient of elasticity, elasticity modulus, elastic modulus.
Nondestructive Testing
Test methods used to examine an object, material, or system without impairing its future
usefulness.
Problem Solving
The ability to get answers to questions through a conscious, organized process. The ans
are usually, but not necessarily, quantitative.
Proportional Limit
Point at which the deformation is no longer directly proportional to the applied force. Hoo
Law no longer applies.
Quality Control
Operational techniques necessary to satisfy all quality requirements; includes process
monitoring and the elimination of root causes of unsatisfactory product or service quality
performance.
Reliability
The probability that a component part, equipment, or system will satisfactorily perform its
intended function under given circumstances, such as environmental conditions, limitatio
to operating time, and frequency and thoroughness of maintenance for a specified perio
time.
Resilience
A mechanical property of a material that shows how effective the material is absorbing
mechanical energy without sustaining any permanent damage.
Rupture Strength
Nominal stress developed in a material at rupture. Not necessarily equal to ultimate stre
Since necking is not taken into account in determining rupture strength, seldom indicates
stress at rupture.
Shear Stress
A measure of how easily a material can be twisted.
Standard Deviation
A statistical measurement of variability.
Statistics
The collection and analysis of numerical data in large quantities.
Strain
Change in the length of an object in some direction per unit.
Stress
The force acting across a unit area in a solid material resisting the separation, compactin
sliding that tends to be induced by external forces.
Stress-Strain Curve
Graphical representation of a material’s mechanical properties.
Tension
The condition of a string, wire, or rod that is stretched between two points.
Toughness
Mechanical property of a material that indicates the ability of the material to handle overl
before it fractures.
Ultimate Stress
Sometimes referred to as tensile strength; determined by measuring the maximum load
material specimen can carry when in the shape of a rectangular bar or cylindrical can.
Variance
The average of the squared differences from the mean.
Lesson 2.4 Design Problem - Overview
Preface
Students have been exposed to the different types and properties of materials in previous lessons. They have also tested
and been made aware of the importance of choosing the right material in regards to safety and environmental impacts.
Students will now apply what they have learned to a design problem using the design process as their guide.
Problems exist everywhere, and they vary in their degree of complexity and importance. Regardless of how problems are
identified or from where they come, engineers use the design process to creatively and efficiently solve problems.
Problems are sometimes solved by teams. These teams work together, constantly communicating with each other, to
create the desired product. The team may receive a problem for which they are expected to create a solution with very
few constraints, with allows them to be quite creative.
In this lesson students will work in teams to solve a materials design problem. They will use their prior knowledge to solve
the problem. It is important for students to understand that an acceptable solution is one that fits the constraints and
specifications of the design brief.
Understandings
1. Design problems can be solved by individuals or in teams.
2. Engineers use a design process to create solutions to existing problems.
3. Design briefs are used to identify the problem specifications and establish project constraints.
4. Teamwork requires constant communication to achieve the desired goal.
5. Design teams conduct research to develop their knowledge base, stimulate creative ideas, and make informed
decisions.
Knowledge and Skills
It is expected that students will:

Brainstorm and sketch possible solutions to an existing design problem.

Create a decision making matrix for the design problem.

Select an approach that meets or satisfies the constraints given in a design brief.

Create a detailed pictorial sketch or use 3D modeling software to document the best choice, based upon your team’s

decision matrix.
Present a workable design solution.
Essential Questions
1. What is a design brief? What are design constraints?
2. Why is a design process so important to follow when creating a solution to a problem?
3. What is a decision matrix and why is it used?
4. What does consensus mean, and how do teams use consensus to make decisions?
5. How do the properties and types of materials affect the solution to a design problem?
6.
Lesson 2.4 Design Problem - Key Terms
Term
Definition
Accuracy
1. The condition or quality of being true, correct, or exact; precision; exactness. 2. The degre
correctness of a quantity or expression.
Assembly
A group of machined or handmade parts that fit together to form a self-contained unit.
Brainstorming
A group technique for solving problems, generating ideas, stimulating creative thinking, etc.,
unrestrained spontaneous participation in discussion.
Component
A part or element of a larger whole.
Consensus
A general agreement.
Constraint
1. A limit to a design process. Constraints may be such things as appearance, funding, spac
materials, and human capabilities. 2. A limitation or restriction.
Decision Matrix
A tool for systematically ranking alternatives according to a set of criteria.
Design Brief
A written plan that identifies a problem to be solved, its criteria, and its constraints. The desig
used to encourage thinking of all aspects of a problem before attempting a solution.
Design Modification
A major or minor change in the design of an item, effected in order to correct a deficiency, to
production, or to improve operational effectiveness.
Design Process
A systematic problem-solving strategy, with criteria and constraints, used to develop many p
solutions to solve a problem or satisfy human needs and wants and to winnow (narrow) dow
possible solutions to one final choice.
Design Statement
A part of a design brief that challenges the designer, describes what a design solution should
without describing how to solve the problem, and identifies the degree to which the solution m
executed.
Designer
A person who designs any of a variety of things. This usually implies the task of creating dra
in some way using visual cues to organize work.
Open-Ended
Not having fixed limits; unrestricted; broad.
Pictorial Sketch
A sketch that shows an object’s height, width, and depth in a single view.
Problem Statement
A part of a design brief that clearly and concisely identifies a client’s or target consumer’s pro
need, or want.
Purpose
The reason for which something is done or for which something exists.
Sketch
A rough drawing representing the main features of an object or scene and often made as a
preliminary study.
Solid Modeling
A type of 3D CAD modeling that represents the volume of an object, not just its lines and sur
This allows for analysis of the object’s mass properties.
Target Consumer
A person or group for which product or service design efforts are intended.
Team
A collection of individuals, each with his or her own expertise, brought together to benefit a c
goal.
Lesson 3.1 Machine Control (VEX) - Overview
Preface
From iPods to automobiles, we use computers every day. Computers are sometimes so small and hidden that we don’t
even realize we’re using a computer. Many of us never think about automobiles containing computers; however, today’s
vehicles are packed with tiny computers that regulate and monitor systems such as air bags and cruise control. How
much more control will computers take from drivers in the future? What will drivers be willing to let their cars do for them?
With GPS systems that provide routes and track speed, what are the barriers for autonomous cars?
In this lesson students will learn how to control mechanical processes using computer software and hardware. The
software communicates through a hardware interface with different inputs and outputs.
Understandings
1. Flowcharts provide a step by step schematic representation of an algorithm or process.
2. Control systems are designed to provide consistent process control and reliability.
3. Control system protocols are an established set of commands or functions typically created in a computer
programming language.
4. Closed loop systems use digital and analog sensor feedback to make operational and process decisions.
5. Open loop systems use programming constants such as time to make operational and process decisions.
Knowledge and Skills
It is expected that students will:

Create detailed flow charts that utilize a computer software application.

Create control system operating programs that utilize computer software.

Create system control programs that utilize flowchart logic.

Choose appropriate input and output devices based on the need of a technological system.

Differentiate between the characteristics of digital and analog devices.

Judge between open and closed loop systems in order to choose the most appropriate system for a given

technological problem.
Design and create a control system based on given needs and constraints.
Essential Questions
1. What are the advantages and disadvantages of using programmable logic to control machines versus monitoring and
adjusting processes manually?
2. What are some everyday seemingly simple devices that contain microprocessors, and what function do the devices
serve?
3. What questions must designers ask when solving problems in order to decide between digital or analog systems and
between open or closed loop systems?
4.
Lesson 3.1 Machine Control - Key Terms
Term
Definition
Algorithm
A step-by-step procedure for solving a problem or accomplishing some end, especially by
computer.
Analog Signal
A signal having the characteristic of being continuous and changing smoothly over a given
rather than switching suddenly between certain levels.
Analog to Digital
Conversion of an analog signal to a digital quantity such as binary.
Closed Loop System
A control system that considers the output of a system and makes adjustments based on t
output.
Data
Information encoded in a digital form, which is usually stored in an assigned address of a d
memory for later use by the processor.
Digital Signal
A system of discrete states: high or low, on or off, 1 or 0.
Digital to Analog
Conversion of a digital signal to its analog equivalent, such as a voltage.
Electromagnet
A conductor wrapped around an iron core. The two ends of the conductor are attached to
source. When current passes through the conductor, the iron core becomes magnetized.
Feedback
The return to the input of a part of the output of a machine, system, or process (as for prod
changes in an electronic circuit that improve performance or in an automatic control device
provide self-corrective action).
Flowchart
A diagram that shows step-by-step progression through a procedure or system especially
connecting lines and a set of conventional symbols.
Input
Information fed into a data processing system or computer.
Interface
The place at which independent and often unrelated systems meet and act on or commun
with each other.
Microprocessor
The central processing unit that is generally made from a single integrated circuit.
Normally Closed
The contact of a relay that is closed when the coil is de-energized.
Normally Open
The contact of a relay that is open when the coil is de-energized.
NTC Resistor
A negative temperature coefficient, also known as a thermistor, is a sensitive resistor who
primary function is to exhibit a change in electric resistance with a change in temperature.
Open Loop System
A control circuit in which the system output has no effect on the control.
Output
The information produced by a computer.
Photocell
A photo-sensitive resistor whose resistance decreases as the light striking the unit increas
Polarity
The type of charge an atomic particle has.
Potentiometer
A switch that can provide variable motion control. It can vary the resistance within the swit
which affects both the current and voltage flowing out of the switch.
Programmable Logic Controller
A specialized heavy-duty computer system used for process control in factories, chemical
and warehouses. Closely associated with traditional relay logic. Also called a programmab
controller (PC).
Reed Switch
An electromagnetically operated switching device.
Sensor
A device that responds to a physical stimulus (as heat, light, sound, pressure, magnetism,
particular motion) and transmits a resulting impulse (as for measurement or operating a co
Subroutine
A subordinate routine; specifically, a sequence of computer instructions for performing a s
task that can be used repeatedly.
Switch
A device for making, breaking, or changing the connections in an electrical circuit.
Transistor
A solid-state switching device.
The design process is iterative; that is, it may repeat steps, or it may backtrack several steps
Many devices function without ever knowing whether they are doing the job that they were programmed to do. They might
run for a specific amount of time or perform one function and then stop. For example if you set the clothes dryer to run for
45 minutes, your clothes might be dry or they might not be dry. A clothes dryer is an open loop system because the
process provides no feedback to the device. Newer clothes dryers possess moisture sensors. The moisture sensors
inform the machine when the clothes are dry, at which point the dryer can stop running. The feedback provided by the
sensor makes this a closed loop system.
Lesson 4.2 Kinematics - Overview
Preface
While statics is concerned with bodies at rest or moving at a constant acceleration, dynamics is concerned with the
accelerated motion of bodies. The study of dynamics developed much later than statics because of the need for accurate
measurement of time. Galileo Galilee was a major early contributor, performing experiments with pendulums and falling
bodies. Newton’s development of the three fundamental laws of motion was the springboard for increased understanding
and work by other scientists. The two major braches of dynamics are kinematics, which is concerned with the geometric
aspects of motion, and kinetics, which is concerned with the forces causing the motion.
In this lesson students will create a vehicle to learn important aspects of motion and freefall. Students will perform an
activity that will help them to understand the kinematics concepts involved in projectile motion.
Understandings
1. When working with bodies in motion, engineers must be able to differentiate and calculate distance, displacement,
speed, velocity, and acceleration.
2. When air resistance is not taken into account, released objects will experience acceleration due to gravity, also known
as freefall.
3. Projectile motion can be predicted and controlled using kinematics equations.
4. When a projectile is launched, velocity in the x direction remains constant; whereas, with time, the velocity in the Y
direction in magnitude and direction changes due to gravity.
Knowledge and Skills
It is expected that students will:
1. Calculate distance, displacement, speed, velocity, and acceleration from data.
2. Design, build, and test a vehicle that stores and releases potential energy for propulsion.
3. Calculate acceleration due to gravity given data from a free fall device.
4. Calculate the X and Y components of a projectile motion.
5. Determine the needed angle to launch a projectile a specific range given the projectile’s initial velocity.
Essential Questions
1. What are the relationships between distance, displacement, speed, velocity, and acceleration?
2. Why is it important to understand and be able to control the motion of a projectile?
3.
Lesson 4.2 Kinematics - Key Terms
Term
Definition
Acceleration
The rate of change of velocity with respect to time.
Free Fall
The condition of unrestrained motion in a gravitational field.
Distance
The total length of path over which the particle travels.
Displacement
A vector quantity giving the straight-line distance and direction from an initial position to
a final position.
Velocity
A vector quantity that includes the speed and direction of an object.
Speed
The magnitude of the total distance traveled divided by the time elapsed.
Mountain Pass:
Horizontal displacement (d) is also known as range (x).
Range x =
x  (x
x
2
x )1(y2  y 2)
1
2
Vi2 sin2θ
-g
Concept 2: If the firing angle and range are known, then the initial velocity may be predicted.
Initial velocity
Vi 
-gx
sin 2
Concept 3: If the range and initial velocity are known, then the firing angle may be predicted.
Firing angle
Acceleration due to gravity
 -gx 
2  sin1  2 
 Vi 
g  9.81
m
s2
Range formula
Substitute
Note: x-y axis is on a horizontal plane from tank to target
Solve. The final answer is the range or displacement from
tank to target.
Note: answers are rounded to the nearest hundredth.
Enter the range the answer blank.
Find the initial velocity (Vi) given the firing angle after solving for range.
Range (x) = 135.28m
Initial velocity formula
Substitute
Solve
Final answer
Note: answers are rounded to the nearest hundredth
Find the firing angle (  ) given the initial velocity after solving for range.
Range (x) = 166.09m
 -gx 
2  sin1  2 
 Vi 
Firing angle formula
Substitute
Solve. Final answer.
Firing Range:Simulation Tips and Example Problems
Find time given distance and rate.
Distance Formula
Rearrange the formula to solve for time by dividing
both sides of the equation by R
Substitute and solve
Final answer