Lesson 2.2 Material Properties - OverviewPrefaceMaterial 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 SkillsIt 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 TermsTerm Definition

Additive Process The process of creating an object by adding small pieces or layers together to make a final product.

Ceramic Of or relating to the manufacture of any product (as earthenware, porcelain, or brick) made 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 physical characteristics and in which each substance retains its identity while contributing desirable properties to the whole; especially, a structural material made of plastic within which a 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 grinder.

Forming A process that changes the size and shape of a material by a combination of force and 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 be 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 force is applied, or that involve the relationship between stress and strain; for example, the modulus of elasticity, tensile strength, and fatigue limit.

Metals Any of various opaque, fusible, ductile, and typically lustrous substances that are good conductors of electricity and heat.

Physical Properties Properties other than mechanical properties that pertain to the physics of a material and can 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 the 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 improvement, development, or elaboration.

Recycling Returning to an original condition. The extraction and recovery of valuable materials from scrap or other discarded materials.

Subtractive Processes that remove material to change the size, shape, or surface of a part. There are two groups of separating processes: machining and shearing.

Synthetic Produced by the combining of parts or elements to form a whole, rather than of natural origin; not real, artificial.

 

Look up different types of ManufacturingProcesses. https://pltw.instructure.com/courses/203679/assignments/3577946?module_item_id=7379811

Lesson 2.3 Material Testing - OverviewPreface

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 SkillsIt 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 the 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 the bulk modulus.

 

Deformation Any alteration of shape or dimensions of a body caused by stresses, thermal expansion or contraction, chemical or metallurgical transformations, or shrinkage and expansions due to moisture change.

 

Destructive Testing Test methods used to examine an object, material, or system causing permanent damage to its 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 expansion.

 

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 element can no longer fulfill its purpose.

 

Fatigue The loss of the load-bearing ability of a material under repeated load application, as opposed to 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 specified form of strain, such as Young's modulus, the bulk modulus, or the shear modulus. Also known 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 answers are usually, but not necessarily, quantitative.

 

Proportional Limit Point at which the deformation is no longer directly proportional to the applied force. Hooke’s 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, limitations as to operating time, and frequency and thoroughness of maintenance for a specified period of 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 strength. Since necking is not taken into account in determining rupture strength, seldom indicates true 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, compacting, or 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 overloading before it fractures.

 

Ultimate Stress Sometimes referred to as tensile strength; determined by measuring the maximum load a 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.

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