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
product.
Ceramic
Of or relating to the manufacture of any product (as earthenware, porcelain
essentially from a nonmetallic mineral (as clay) by firing at a high temperatu
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 differen
characteristics and in which each substance retains its identity while contrib
properties to the whole; especially, a structural material made of plastic with
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 mac
Forming
A process that changes the size and shape of a material by a combination o
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 han
machinery; to produce according to an organized plan and with division of la
Material
The elements, constituents, or substances of which something is composed
made; matter that has qualities which give it individuality and by which it ma
categorized.
Mechanical Properties
Those properties of a material that reveal the elastic and inelastic reaction w
applied, or that involve the relationship between stress and strain; for exam
of elasticity, tensile strength, and fatigue limit.
Metals
Any of various opaque, fusible, ductile, and typically lustrous substances th
conductors of electricity and heat.
Physical Properties
Properties other than mechanical properties that pertain to the physics of a
usually be measured without the application of force.
Polymers
Any of numerous natural and synthetic compounds of usually high molecula
consisting of up to millions of repeated linked units, each a relatively light an
molecule.
Product Life Cycle
Stages a product goes through from concept and use to eventual withdrawa
marketplace.
Raw Material
Crude or processed material that can be converted by manufacture, proces
combination into a new and useful product; something with a potential for im
development, or elaboration.
Recycling
Returning to an original condition. The extraction and recovery of valuable m
scrap or other discarded materials.
Subtractive
Processes that remove material to change the size, shape, or surface of a p
two groups of separating processes: machining and shearing.
Synthetic
Produced by the combining of parts or elements to form a whole, rather tha
origin; not real, artificial.
Look up different types of ManufacturingProcesses.
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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
perpendicular to the plane of the section.A force in a direction parallel to the lon
structure.
Breaking Stress
The stress required to fracture a material whether by compression, tension, or s
Compression
When a material is reduced in volume by the application of pressure; the recipro
modulus.
Deformation
Any alteration of shape or dimensions of a body caused by stresses, thermal ex
contraction, chemical or metallurgical transformations, or shrinkage and expans
moisture change.
Destructive Testing
Test methods used to examine an object, material, or system causing permanen
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
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 structura
no longer fulfill its purpose.
Fatigue
The loss of the load-bearing ability of a material under repeated load application
a single load.
Hooke’s Law
The law stating that the stress of a solid is directly proportional to the strain appl
Modulus of Elasticity
The ratio of the increment of some specified form of stress to the increment of s
form of strain, such as Young's modulus, the bulk modulus, or the shear modulu
as coefficient of elasticity, elasticity modulus, elastic modulus.
Nondestructive Testing
Test methods used to examine an object, material, or system without impairing
usefulness.
Problem Solving
The ability to get answers to questions through a conscious, organized process.
are usually, but not necessarily, quantitative.
Proportional Limit
Point at which the deformation is no longer directly proportional to the applied fo
Law no longer applies.
Quality Control
Operational techniques necessary to satisfy all quality requirements; includes pr
monitoring and the elimination of root causes of unsatisfactory product or servic
performance.
Reliability
The probability that a component part, equipment, or system will satisfactorily pe
intended function under given circumstances, such as environmental conditions
to operating time, and frequency and thoroughness of maintenance for a specifi
time.
Resilience
A mechanical property of a material that shows how effective the material is abs
mechanical energy without sustaining any permanent damage.
Rupture Strength
Nominal stress developed in a material at rupture. Not necessarily equal to ultim
Since necking is not taken into account in determining rupture strength, seldom
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, c
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 han
before it fractures.
Ultimate Stress
Sometimes referred to as tensile strength; determined by measuring the maxim
material specimen can carry when in the shape of a rectangular bar or cylindrica
Variance
The average of the squared differences from the mean.
5.