POE – Review Sheet 3

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.

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 softb) Cost; scarcity of elementc) 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 - OverviewPrefaceMaterial 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.

Lesson 2.4 Design Problem - OverviewPrefaceStudents 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 degree of 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., by 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, space, 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 design brief is 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 facilitate production, or to improve operational effectiveness.

Design Process A systematic problem-solving strategy, with criteria and constraints, used to develop many possible solutions to solve a problem or satisfy human needs and wants and to winnow (narrow) down the possible solutions to one final choice.

Design Statement A part of a design brief that challenges the designer, describes what a design solution should do without describing how to solve the problem, and identifies the degree to which the solution must be

executed.

Designer A person who designs any of a variety of things. This usually implies the task of creating drawings or 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 problem, 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 surfaces. 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 common goal.

Lesson 3.1 Machine Control (VEX) - OverviewPrefaceFrom 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 SkillsIt 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 a computer.

Analog Signal A signal having the characteristic of being continuous and changing smoothly over a given range, 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 that output.

Data Information encoded in a digital form, which is usually stored in an assigned address of a data 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 a power 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 producing changes in an electronic circuit that improve performance or in an automatic control device that provide self-corrective action).

Flowchart A diagram that shows step-by-step progression through a procedure or system especially using 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 communicate

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 whose 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 increases.

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 switch, 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 plants, and warehouses. Closely associated with traditional relay logic. Also called a programmable controller (PC).

Reed Switch An electromagnetically operated switching device.

Sensor A device that responds to a physical stimulus (as heat, light, sound, pressure, magnetism, or a particular motion) and transmits a resulting impulse (as for measurement or operating a control).

Subroutine A subordinate routine; specifically, a sequence of computer instructions for performing a specified 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 - OverviewPrefaceWhile 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 SkillsIt 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 =

Concept 2: If the firing angle and range are known, then the initial velocity may be predicted.

Initial velocity

Concept 3: If the range and initial velocity are known, then the firing angle may be predicted.

Firing angle

Acceleration due to gravity

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

-g12i

x2 sin V

Firing angle formula

Substitute

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

Solve. Final answer.