Lecture 1 Topics - Mars at UMHB | Department of …mars.umhb.edu/~wgt/engr1310/2007/Reading Assignment 3.pdf · American Heritage Dictionary Defining ... – Little significant research

Lecture 1 - Introduction to Engineering

© 2006 Baylor University

Lecture 1 Topics

Dr. Carolyn SkurlaSpeaking

•Outline–Introduction to Course–Definition of Engineering–Engineering at Baylor University


• Questions About Engineering– What is engineering?– What do engineers do in their profession?– What are the different types of engineering?– What is the difference between science and engineering?

• How?– Lectures, Hand-On Labs, Homework, Reading Assignments– Design Project!

Purpose of“Introduction to Engineering”

1



StaticsFluid Mechanics

Engineering Ethics

Digital Logic

Electric Circuits

Power Generation Plants

The Engineering Design Process

Materials and Manufacturing Methods

Energy and Work

Some Cool Subjects We Will Study


• If you are purchasing a calculator,

the TI-89 is strongly

recommended. If you already

have another calculator, it is not

necessary to purchase a TI-89 for

EGR 1301.

Calculator Usage

2



Knowledge of, and interest in, mathematics and the natural sciences

Interest in computers and/or technology

Practical problem solving

Design

Creativity

Common Engineering Key Words


• Interested in creating things

• Enjoy problem solving

• Good at math and science

• Want to know how things work

• Financial reasons

• Not sure yet

http://www.flickr.com/photos/bangfalse/422226927/

Why Do YOU Want To BeAn Engineer?

3



• Scientist seek

• Engineers apply _____________ in order to ____________

• Take time and consider why you would like to be an engineering major rather than a physics, math or biology, or chemistry major…

How Does Engineering Differ From Math & Science?


“The application of scientific and mathematical principles to practical

ends such as the design, construction, and operation of efficient and

economical structures, equipment, and systems.”

American Heritage Dictionary

Defining “Engineering”

4



• Accreditation Board of Engineering and Technology (ABET)

• “The profession in which knowledge of the mathematical and natural sciences, gained by study, experience, and practice, is applied with judgment to develop ways to use, economically, the materials and

forces of nature for the benefit of mankind.”

What Is Engineering?


• What is the difference between being a mechanical engineer and being a mechanic?

• How does engineering technology differ from engineering?

http://t3.pacific.edu/teams/B004205/mechanic.jpg

Mechanical Engineering (Structural Design)

http://www.vrac.iastate.edu/~jmvance/sen_opt/gifs/car_L.gif

Auto Mechanic

What Is Engineering?

5



• To be a professional engineer

• To be a lawyer

• To be a physician• To be a business consultant (e.g. McKinsey

Inc.)

• To be able to use my God-given gifts and talents to serve others in the best possible way

Why Study Engineering?


• Latin in generare– Engine– Ingenious

• 200 AD– Roman attack on Carthaginians

using an ingenious invention (ingenium)

• 1200s the ingeniator– Battering rams, assault towers,

etc.

The Origins of Engineering

6



• Civil Engineering

http://en.wikipedia.org/wiki/Image:Systems_engineering_application_projects_collage.jpg

• Electrical and Computer Engineering

• Mechanical Engineering

• Chemical Engineering

• Industrial Engineering

• Nuclear Engineering,

• Aerospace Engineering…

• Biomedical Engineering

The Engineering Disciplines


Work (American Heritage Dictionary)

• Physical or mental effort or activity directed toward the production or accomplishment of something.

• Employment; Job.

Job (American Heritage Dictionary)

• A regular activity performed in exchange for payment; especially a trade, occupation, or profession

• A position in which one is employed.

What Is The Difference Between “Job”/”Work” and “Vocation”?

7



Vocation (Houghton-Miflin Dictionary)

• A regular occupation, especially one for which a person is particularly suited or qualified.

• An inclination, as if in response to a summons, to undertake a certain kind of work, especially a religious career; a calling.

What Is The Difference Between “Job”/”Work” and “Vocation”?


The Mission of the engineering departments is to educate

students, within a caring Christian environment, in the

discipline of engineering, by combining a strong technical

foundation with an emphasis on professional, moral,

ethical and leadership development.

Mission Statement:

Engineering at Baylor

8



• Accreditation Board for Engineering and

Technology (ABET)

• _________ are accredited, not schools

• All three engineering programs at Baylor are

accredited

Accreditation


• Electrical & Computer Engineering

• Mechanical Engineering

• Engineering– Biomedical Option

– Flexible Option• Biomechanics

• Biomedical Signals

• Computer Systems

• Electronics

• Fluids and Thermal Energy

• Mechanical Design

• Signal Processing http://en.wikipedia.org/wiki/Image:FalkirkWheelSide_2004_SeanMcClean.jpg

The Falkirk Wheel in Scotland

Programs at Baylor

9



Humanities & Social Sciences 18-25 Sem Hrs

Math & Science 32 Sem Hrs

Engineering Topics 67 Sem Hrs

Other 19 Sem Hrs

Min Req Total 136 Sem Hrs

Curriculum Summary

10

Lecture 2 - Engineering Method, Team Building, Problem Solving, Plagiarism

Slide 3© 2006 Baylor University


•Outline–The Engineering Method–Team Building–Creative Problem Solving–Plagiarism

Lecture 2 Topics


• Engineers are not defined by their product

– Nano-robots– Airplanes– Embedded Computers

• Engineers are defined by their ______________

– Finding the best change using available resources in an environment of uncertainty

What is an Engineer?

11



• The clergy in Iran engineered the firing of the president.

• The chessmaster engineered a perfect countermove.

• The general engineered a coup d'état without the loss of life.

http://www.teamclouds.com/staff/dawboy/images/chess_set.png

“To Engineer”


• The Scientific Method

– Well-understood, even by the layperson.

– “Science is theory corrected by experiment.”

– All variables held constant except one.

– “Answer in the back of the book.”

– Extensively analyzed by philosophers

Why is Engineering Such a Mystery?

12



• The Engineering Method– Little significant research into the philosophical foundations of engineering.

– Can you name an engineer who is wise, well-known, well-read, and scholarly

in their role as an engineer?

• Contrast with law, economics, medicine, politics, religion, and science

– Can you name a public spokesperson in any of these fields?



• Few high school students take engineering courses• Liberal arts students are not required to study technology• Technology students are required to study liberal arts


13



• Change: the situation requires a change.

• Best: the best change is desired...

• Resources: using the ________________ resources

• Uncertainty: knowledge about the situation is ____________

and sometimes inconsistent

Four Key Elements of Engineering Problems


Time

Mea

sure

of C

hang

e

A

B

Change

14



• Four practical difficulties in getting from A to B:

– Engineer lacks complete knowledge of the world at A

– The exact final state, B, is unknown and cannot be anticipated

– There is no _______________ from A to B

– Engineering goals can change during the process

• The location of B ______________

Change


• Is all change caused by engineers good?

– What about unintended consequences?

• Aswan High Dam in Egypt

– Can you think of any engineering disasters?

• Tacoma Narrows Bridge

• Kansas City Hyatt Regency

• Chernobyl Nuclear Power Plant in U.S.S.R.

Change

15


Slide 13© 2006 Baylor University http://www.cia.gov/cia/publications/factbook/geos/eg.html

Unintended Consequences

Slide 14© 2006 Baylor Universityhttp://upload.wikimedia.org/wikipedia/nl/thumb/f/fa/280px-AswanHighDam_Egypt.jpg

16



• Increased salinity of the Nile by 10%

– Led to collapse of sardine industry

• Caused coastal erosion

• Displaced 100,000 Nubians

– Drastically altering their way of life

Unintended Consequences


• Tangible Resources– Money available for project

– Time to complete project– Raw materials (e.g., steel, concrete,

silicon)

– _______________________

– Number of engineers

• Intangible Resources– Engineering staff’s past experience

with similar projects

– Engineering staff’s _____________

http://newportbeachattorneys.org/gen02_clock.jpg

http://fullcircle.typepad.com/photos/uncategorized/free_money.jpg

Available Resources

17



• Problem : Estimate the number of ping-pong balls that can fill a room– 60 seconds– 2 days– Unlimited time

• Each time limit defines _______________________because the time resource is different

• Each solution would be correct from an engineering point of view.

Time As a Resource


• Best for whom?– Westerners are conditioned to accept Plato’s notion of the

ideal– A new concept of “best”

• Optimization theory– The Optimum __________________– Apollo Program

• Leapfrog learning• Political vs. Economic tradeoffs

Best

18



Consider a television with only one knob:Increased knob setting results in sharper picture,Increased knob setting also results in worse sound.

Best: Television Example


Assuming picture and sound are equally weighted


19



Picture is half as important as sound (for a person with hearing problems)



• Engineers are asked to find a solution to a problem while lacking complete information

• In Change: both the starting and ending points (A & B) are not fully known

• Resources: intangible resources cannot be quantified, yet they affect the outcome

• Best: the best design is not always clear, best for whom?

Uncertainty

20



• Your future employer requires __________________• Student-centered learning is encouraged

– Active learning– Collaborative learning– Cooperative learning

• Positive interdependence• Individual accountability• Face-to-face interaction• Appropriate use of interpersonal skills• Regular self-assessment of group functioning

Why Work in Teams?


• Improved– Student-faculty interaction– Student-student interaction– Grades & information retention– Teamwork & interpersonal skills– Communication skills– Training for the professional work environment

Benefits of Cooperative Learning

21



• Thinking Aloud Pairs Problem-Solving (TAPPS)– Students form pairs

• Problem-Solver (PS)– Talks through solution to the problem

• Listener (L)– Questions– Prompts PS to keep talking– Gives clues when necessary

– Short training exercise

Creative Problem Solving

22


THINKING ALOUD PAIRS PROBLEM SOLVING (TAPPS) The Problem Solver: 1. Adjust the chairs so that you and your partner are comfortably seated at a worktable. 2. Make sure that you have paper, pencil, a calculator, and anything else you may need to solve

the problem. 3. There may be hints or suggestions given about how to approach a particular problem.

Discuss these with your partner before you start. 4. Read the problem aloud. 5. Start to solve the problem on your own. You are solving the problem; your partner is only

listening to your and reacting to what you say, not collaborating in the solution. 6. Thinking aloud isn’t easy. At first you may have trouble finding the right words; don’t

search for them, say whatever comes to your mind. You and your partner are trying to help each other, and no one is evaluating you.

7. Go back over any part of a problem you wish. Use such words as, “I’m stuck. I’d better start over.” “No, that won’t work…let’s see…hmmm.”

8. Try to solve the problem even if you think it trivial, or if you don’t think you’re learning anything. Most people don’t realize the fantastic improvement that occurs when they engage in this process. When you complete a problem, record what you think you learned about the process so you can see your progress. Then have your partner add his/her ideas.

The Listener:

1. Establish as quickly as possible that you will be a questioner and not a critic, and that you are not criticizing when you ask questions like, “Please elaborate.” “What are you thinking now?” “Can you check that?”

2. Your role is to: a. Demand that PS keep talking, but don’t keep interrupting when PS is thinking. b. Make sure that PS follows the strategy and doesn’t skip any of the steps. c. Help PS improve his/her accuracy. d. Help reflect the mental process PS is following. e. Make sure that you understand each step that PS takes.

3. Do not turn away from PS and start to work the problem on your own. It may be better if you don’t even pick up a pencil. Track PS’ procedure actively.

4. Do not let PS continue if: a. You don’t understand what he/she is doing. Say “I don’t understand,” or “I can’t

follow that.” b. You think a mistake has been made. Ask him/her “to check that,” or “Does that

sound right?” 5. Do not give PS hints. If he/she continues to make an error in thinking or in computation,

then point out the error, but do not correct it. Source: J.E. Stice, National Effective Teaching Institute, 2003.

23


THINKING ALOUD PAIRS PROBLEM SOLVING (TAPPS) EXERCISE 1: TRAVELS OF A BOOKWORM A set of four volumes sits on a shelf in the library. Each of the covers of each book is 1/6-inch thick, and the text in each volume is 2 inches thick. A bookworm approaches the set of books and finds the work to his taste. He eats from page 1 of Volume I to the last page of Volume IV. How far did the bookworm’s lunch take him, in inches? Source: J.E. Stice, National Effective Teaching Institute, 2003.

24


THINKING ALOUD PAIRS PROBLEM SOLVING (TAPPS) EXERCISE 2: Boronoff, Carlisle, O’Brien, and Revitsky are four talented, creative artists. One is a singer, one is a dancer, one is a painter, and one is a writer, although not necessarily in the order named. Clues:

1. Boronoff and Revitsky were in the audience the night the singer made his debut.

2. Both Carlisle and the writer have sat for portraits by the painter.

3. The writer, whose biography of O’Brien was a best-seller, is planning to write a biography of Boronoff.

4. Boronoff has never seen Revitsky.

NOTE: In Clue 2, neither of the portraits was a self-portrait. In Clue 3, neither of the biographies was an autobiography. Adapted from C.R. Wylie, Jr., 101 Puzzles in Thought and Logic. New York: Dover Publishers, 1957.

25



• “Plagiarism is using others' ideas and words without clearly acknowledging the source of that information.”1

1Writing Tutorial Services, Indiana University, Bloomington, IN <http://www.indiana.edu/~wts/wts/plagiarism.html>

Plagiarism


• “To avoid plagiarism, you must give credit whenever you use– another person's idea, opinion, or theory; – any facts, statistics, graphs, drawings--any pieces of

information--that are not common knowledge; – quotations of another person's actual spoken or written

words; or – paraphrase of another person's spoken or written words.”1

1Writing Tutorial Services, Indiana University, Bloomington, IN <http://www.indiana.edu/~wts/wts/plagiarism.html>

How Students Can Avoid Plagiarism

26



• Go to the Indiana University’s website on plagiarism.– http://education.indiana.edu/%7Efrick/plagiarism/– Explore the links, examples, and quizzes until you

are ready to attempt the test.– Print the confirmation certificate, fill it out, sign it,

and:• Fax a copy to your instructor OR• Scan it and e-mail a copy to your instructor

How to Avoid Plagiarism


References

• Koen, Billy Vaughn, Discussion of The Method, Oxford University Press, 2003

• Egypt map from CIA website: http://www.cia.gov/cia/publications/factbook/geos/eg.html

• Aswan Dam photo: http://upload.wikimedia.org/wikipedia/nl/thumb/f/fa/280px-AswanHighDam_Egypt.jpg

27


Plagiarism Exercise Original Source Material:

The British Institution’s definition of structural engineering crowds into the same box the ideas of economy and elegance, for responsible engineering wastes neither physical nor mental resources. Economic constraints are often imposed by the demands of the marketplace, but the requirement for elegance is often self-imposed by the best in the profession in much the same way that artists and scientists alike see elegance in the sparest canvases and the most compact theories – or in the axiom of the minimalist aesthetics and design, “less is more.”

Quoted directly from pp. 40-41 of: Petroski, Henry. To Engineer is Human: The Role of Failure in Successful Design. Vintage Books, New York (1992). Sample #1: ___________________________________________________________________________

Responsible engineering wastes neither physical nor mental resources. Economic constraints are often imposed by the demands of the marketplace.

Sample #2: ___________________________________________________________________________

According to Petroski, “Responsible engineering wastes neither physical nor mental resources [1].” Marketplace demands often impose economic constraints. Bibliography: 1. Petroski, Henry. To Engineer is Human: The Role of Failure in Successful Design. Vintage Books,

New York (1992). Sample #3: ___________________________________________________________________________

According to Petroski, responsible engineering wastes neither physical nor mental resources [1]. Bibliography: 1. Petroski, Henry. To Engineer is Human: The Role of Failure in Successful Design. Vintage Books,

New York (1992). Sample #4: ___________________________________________________________________________

According to Petroski, “Responsible engineering wastes neither physical nor mental resources [1].” He also states that marketplace realities may necessitate fiscal limitations. Bibliography: 1. Petroski, Henry. To Engineer is Human: The Role of Failure in Successful Design. Vintage Books,

New York (1992).

28

Lecture 3 - Statics - Part 1


•Outline– Understand the definition of Mechanics– Learn the difference between static and

dynamic analysis– Understand the importance of

engineering analysis in structural design– Apply these concepts to a foot bridge

and discuss the design tradeoffs– Understand the concept of force as a

vector– Separate vector into x and y components.– Apply this concept to analyzing sums of

forces (ΣF=0 in statics).Prof. Dick CampbellSpeaking

Lecture 3 Topics


• Mechanics - the study of objects at rest or in motion, the effects of forces on a body, and the prediction motion.

• The fundamentals of Mechanics were formulated by Isaac Newton, using his three Laws:1. A body at rest or in constant

motion remains in that state until acted upon by an external unopposed force.

2. An unopposed force causes a mass to _____________.

3. Every force action has an __________________ reaction.

Mechanics

29



• Mechanics is divided into the study of Statics and Dynamics.

• Newton’s 2nd Law is expressed as:

Mechanics

∑ = maF


Static analysis

• Therefore...a = 0 • In Statics, nothing is accelerating!

•Newton’s 1st Law• Statics is the study of forces acting on a non-accelerating body,

and the reaction of that body

Dynamic Analysis• If an unopposed force acts:

• Acceleration is proportional to the mass of the body• Dynamics is the study of the motion of a body, both in translation and

rotation.

Statics vs. Dynamics

30



• Baylor Engineers in Africa, May 2005– 3 professors, 6 students– Kenya, Africa– Engineering services to Kenya’s

poor population• Foot Bridge Project

– 130 ft. wide river– Analyze for safety and possible

design improvements

An Example of Engineering Analysis


• Village was divided, far side had trouble:– Taking their farm produce

to market– Attending school– Getting medical care

• Situation– 5 miles to nearest bridge

(20 mile round trip)– Several drownings per year

Need For Bridge

31



• Estimates of approximately 400 crossings per day– Saving 1,460,000 miles of

walking per year• Approximate cost: $5000

– 1/3 ¢ per mile per year– Great impact at minimal

cost

Need For Bridge


• Cable used is rated to withstand a maximum load in tension of 16,000 lbs.– How much can the bridge support?– How is cable failure considered in the design?– If six people (est. 1000 lbs.) stand in the center, what is the cable

tension?– What is the “safety factor” (SF)?

How Does Engineering Analysis Help?

32



• The wood decking was built using 3-1”x 6” planks laid side by side.– The bridge span is 130 feet. – The wood’s density is 30 lbs/ft3.– The weight of the cable and

hangers is approx. 112 lbs. – Can you calculate the weight of

the decking? • What does this do to our safety

factor?

What About the Weight of the Bridge?

130 ft


• If we allow the bridge to have larger sag, what will happen to the tension in the cables?

• What will happen to the required anchors for the cables at the two ends of the bridge?

• What is the disadvantage of having larger sag in the bridge?• We will use the Principles of Statics Analysis to answer all of these

questions.

Engineering is an Exercisein Trade-Offs!

33



• How does a suspension bridge like the Golden Gate provide a way to achieve the goals of lower cost and convenience of use?

• What are the disadvantages in the suspension bridge design?

Suspension Bridges


Engineering Disasters:Tacoma Narrows Bridge

34



The importance of proper engineering analysis.

Engineering Disasters:Kansas City Hyatt Regency Hotel


• Scalar– Has magnitude only

• Vector – Has magnitude and direction– In an x-y coordinate system, force may be broken down into

“components”• X-component parallel to x-axis• Y-component parallel to y-axis

Θ

Force as a Vector

35



• Magnitude of the force vector– Can be calculated from the magnitude of its components using the

Pythagorean theorem

)cos(Θ∗= FFx

22yx FFF +=

v

)sin(Θ∗= FFy

⎟⎟⎠

⎞⎜⎜⎝

⎛=Θ −

x

y

FF1tan

Force as a Vector


• î and ĵ indicate direction of vector components– î has magnitude of 1 unit in the x-direction– ĵ has magnitude of 1 unit in the y-direction

• When a vector component is multiplied by î or ĵ– Magnitude of the vector component remains unchanged– The direction of the vector component is defined as parallel to

the x- or y-axis

Unit Vectors

36



• Draw a sketch of the forces as vectors• Write each force vector in terms of i and j components

– Components perpendicular to each other can be treated separately• Invoke Newton’s 1st Law

– Sum of i components=zero – Sum of j components = zero

• Solve the two equations with two unknowns

Setting Up the Analysis


• Simplifying assumptions– Loaded with six persons (approx. 1000 lbs) at the center – Cables are straight– Neglect the weight of the bridge

i

j

Force Vectors & Static Analysis ofFoot Bridge

lbs F 10003 =v

?1 =Fv ?2 =F

v

ft 130

ft 5

37



• Resolve the three forces into î, ĵ components• Identify our unknowns (i.e., F1 and F2)

• Set up summation equations in î, ĵ directions– Solve these two equations for the unknowns

i

j

Static Analysis of the Foot Bridge’s Cable

lbs F 10003 =v

?1 =Fv ?2 =F

v

ft 130

ft 5


i

j

?2 =Fv

lbs F 10003 =v

?1 =Fv

ft 130

ft 54.4˚4.4˚

jFiFF ˆsinˆcos 111 θθ +−=v jFiFF ˆsinˆcos 222 θθ +=

v

jlbsilbsF ˆ1000ˆ03 ⋅⋅−⋅⋅=v


38



Substituting in angles:

2121 ),4.4cos()4.4cos( FFFF ==lbsFF ⋅=+ 1000)4.4sin()4.4sin( 21

Safety Factor (Cable Strength = 16,000 lbs):


0ˆ0ˆcosˆcosˆ21 =⋅⋅++−=Σ ilbsiFiFiF θθ

0ˆ1000ˆsinˆsinˆ21 =⋅⋅−+=Σ jlbsjFjFjF θθ


Then: lbsF 1000)10sin(2 1 =

What happens to the Safety Factor if we increase thesag? Let : o10=θ


39



What happens to the Safety Factor if we include the weight of the bridge? Let:

Then:



What is the best way to hang a 40 lb mirror on a wall? How much tension is in the hanger wire in each case?

Picture Frame Sample Problem

Option 1: One Hanger in Wall Option 2: Two Hangers in Wall

48 in

12 in 12 in

12 in

40




Option 1: One Hanger in Wall

48 in

12 in i

j

3Fv

2Fv

1Fv

3Fv

ββ



i

j

2Fv

1Fv

3Fvβ

Option 2: Two Hangers in Wall

12 in

12 in

β

41



•Outline– Understand why structures are built with triangles– Understand truss bridges as an example of a structure built with triangles– Apply static analysis to truss bridges– Understand the simplifying assumptions for the truss analysis– Determine load in each member of truss bridge that is supporting a load using static

analysis

Prof. Dick CampbellSpeaking

Lecture 4 Topics


• Pinned triangles are naturally rigid• Joint strength becomes less critical• High stiffness can be achieved for small amount of material

used• Ease of construction

ForceForce

Why Structures Are Built With Triangles

42



The truss is a simple skeletal structure. In design theory, the individual members of a simple truss are only subject to tension (pulling) and compression (pushing) forces and not bending forces.

There are both simple and continuous trusses. The small size of individual parts of a truss make it the ideal bridge for places where large parts or sections cannot be shipped. Because the truss is a hollow skeletal structure, the roadway may pass over or even through the structure allowing for clearance below the bridge often not possible with other bridge types.


Trusses are constructed using triangles and are also classified by the basic design used.

The Warren truss is perhaps the most common truss for both simple and continuous trusses. For smaller spans, no vertical members are used lending the structure a simple look. For longer spans vertical members are added providing extra strength.

Warren trusses are typically used in spans of between 50-100m.

Truss Bridges

43



• Pratt - The Pratt truss is identified by its diagonal members which, except for the very end ones, all slant down and in toward the center of the span. Except for those diagonal members near the center, all the diagonal members are subject to tension forces only while the shorter vertical members handle the compressive forces. This allows for thinner diagonal members resulting in a more economic design.

• Howe - The Howe truss is the opposite of the Pratt truss. The diagonal members face in the opposite direction and handle compressive forces (requiring thicker elements. This makes it very uneconomic design for steel bridges and its use is rarely seen.

Truss Bridges


• This bridge was designated as an international historical monument by the Canadian Society for Civil Engineering and the American Society of Civil Engineers. The Pont de Québec is formed by a 549 m (1702’) suspended span located between two main pillars, which makes this bridge the longest cantilever bridge in the world. While the bridge was under construction, the suspended span collapsed on two occasions (in 1907 and 1916), killing many workers. Trains began using the bridge in 1917 while automobiles were only allowed on it in 1929.

World’s Longest Truss BridgePont de Quebec

44



• Sum of forces at each joint, or node, must equal zero• Each element is a “two-force” member (i.e., the direction of the force is along the

axis)– If an element is in tension, it will pull on both joints– If an element is in compression, it will push on both joints

• Joints are pinned and frictionless (i.e., pins will not support a moment)• A moment is a force that causes rotation and is explained in the next few slides • No deformation occurs to change dimensions• The external reactions are statically determinant, and the supports are frictionless:

R1R3

R2

Concepts & Assumptions for Static Analysis of Truss Bridges


• Moments occur at a given point and are caused by a force that causes rotation about a point or an axis.

• A moment is equal to the Force times the perpendicular distance from the force to the point that is being evaluated.

• Force F causes a clockwise rotation if unopposed about point A in the picture below.

• 4in is the perpendicular distance and 100lb is the force in the picture, so the Moment M caused by this force is: M=-(100lb x 4in) = -400 lb-in

• The moment is negative because it is clockwise.• Be careful with units, Moments can be measured in lb-in, lb- ft, N-m, or other units.

Moments

45



Summing Moments & External Forces in Truss Analysis

• Moments are summed to determine missing external forces in truss analysis.• There is no rotation in the truss (i.e., static equilibrium)• The sum of the moments about any joint in the truss equals 0

– Forces through a joint do not create a moment at that joint.– Moments are negative if the force applied would cause a clockwise motion if the truss

member could rotate.– Moments are positive if the force applied would cause a counter-clockwise motion if the

truss member could rotate.• The Sum of the Forces also equals 0• Three equations - Three unknowns


• Sum moments about Joint B

• Sum forces in the y-direction

• Sum forces in the x-direction

Summing Moments & External Forces in Truss Analysis

46



• Determine External Reactions using Newton’s 1st Law:

i

j

• The truss has three external reactions, and we can write three equations of static equilibrium.

A

BC

D

E

1R

3R

2R

lbs 500=P

ft 10ft 10

ft 10

ft 10 ft 66.8=h

θ

o60=θ

∑ =⋅+⋅−= 0)20()5500( 1 ftRftlbM D

∑ == 03RFx

∑ =−+= 050021 lbRRFy

Truss Analysis

+


x

y +

•Determine the forces at node D, by drawing a “free body” diagram:

•We assume that all unknown forces are in tension by drawing the arrow pulling on the node. Our sign convention will indicate if an element is in compression by a negative sign.

A

BC

E

lbs125

lbsR 03 =

lbs 500=P

ft 10ft 10

ft 10

ft 10 ft 66.8=h

lbs375

D

Truss Analysis

47



•Just as we used the equations of static equilibrium to determine the external reactions, we can apply the same method to each node:

x

y +

A

BC

Elbs125

lbsR 03 =

lbs 500=P

ft 10ft 10

ft 10

ft 10 ft 66.8=h

lbs375

D

D

375

DCF

DEF θ

NODE D Free Body Diagram

FCD at points C and D

Truss Analysis


D

375

DCF

DEF θ

NODE D Free Body Diagram

•FDC is in the opposite direction that is shown in the free body diagram.

•FDE is in the same direction that is shown in the free body diagram

tension

compression

DCF

DEF

375

NODE D with Corrected Arrow

Directions

Free Body Diagram

48



x

y +

A

BC

D

E

lbs 500=P

ft 10ft 10

ft 10

ft 10 ft 66.8=h

θo60=θ

ncompressio lbs 433=DCF

lbs 217=DEF

03 =R

3752 =R1251 =R

Truss Analysis Continued

C433=DCF

CEF θ

NODE C Free Body Diagram

4 Forces, but only two unknowns

BCF500=P


x

y +

A

BC

D

E

lbs 500=P

ft 10ft 10

ft 10

ft 10 ft 66.8=h

θo60=θ


lbs 217=DEF

03 =R

3752 =R1251 =R

Truss Analysis Continued

B 144=BCF

ABFθ

NODE B Free Body Diagram

3 Forces, but only two unknowns

BEF

49



x

y +

A

BC

D

E

lbs 500=P

ft 10ft 10

ft 10

ft 10 ft 66.8=h

θo60=θ


lbs 217=DEF

03 =R

3752 =R1251 =R

Truss Analysis Completed

A144=ABF

AEFθNODE A Free Body

Diagram

3 Forces, but only one unknown 1251 =R

Double check your work by analyzing Node E to see if you get the same results.

50

Lecture 5 - Materials Selection in Engineering



•Outline–Materials Science–Materials Selection in Engineering

Lecture 5 Topics


• Pace of technology– Space exploration– Aviation– Defense– Sports

http://www.centennialofflight.gov

http://www.wilson.com

http://www.pbs.org/wgbh/nova/lostempires/trebuchet/race.html

http://www.educationplanet.com

Why Study Materials Science?

51



• Selection of materials appropriate for design• Analysis of ________________

– Shuttle disasters

http://www.nasa.gov, http://www.noaa.gov

Columbia - Feb. 1, 2003

Challenger - Jan. 28, 1986

Why Study Materials Science?


Coffee Cup Examples

52



• Metals• Ceramics• Polymers (plastics)• Semi-conductors• Composites

Fig. C.1, Callister 7e.;

http://www.wilson.com

Classes of Materials


Function

•Transmit loads, heat•Contain pressure•Etc.

Material

•Material properties: general, mechanical, electrical, etc.

Shape

•Shape factors: characteristic values for bending and twisting, etc.

Process•Process Attributes: material, shape & size, tolerance, batch size, cost, etc.

Adapted from Materials Selection in Mechanical Design, Ashby.

So, How Do We Select a Material?

53



• Seek a specific combination of standard attributes, or material properties– General

• Price• Density

– Mechanical• Strength• Toughness• Fatigue endurance limit

– Wear resistance– Magnetic

– Thermal• Melting point• Thermal conductivity• Thermal expansion

– Electrical• Electrical conductivity

– Optical– Environmental resistance– Environmental impact

• Production energy• Recyclability

Materials Properties


• Atomic bonding, crystal structure, and microstructure dictates _____________

• ________________ can change microstructure structures and properties

Fig. 1.9, Askeland 3e.

Materials Properties

54



70,00010% Sn10,000Cu

60,0004% Cu5,000Al

60,0000.5% C6,000Fe

Strength (psi)

Alloying Element

Strength (psi)

Pure Metal

Mechanical Properties


• Space Shuttle Tiles:– Silica fiber insulation

• Low _________________• Low density• Low coefficient of thermal expansion

Fig. 19.0, Callister 7e. (Courtesy of Lockheed Missiles and Space Company, Inc.)

Thermal Properties

55



Adapted from Fig. 1.2,Callister 7e.(Specimen preparation,P.A. Lessing; photo by J. Telford.)

• Transmittance:– Aluminum oxide may be transparent, translucent, or

opaque depending on the ____________________.

Optical Properties


Adapted from Fig. 17.0, Callister 6e.(Fig. 17.0 is from Marine Corrosion, Causes, and Prevention, John Wiley and Sons, Inc., 1975.)

• Stress & Saltwater– Causes __________

Environmental Resistance

56



Materials Selection Tools

57


Materials Selection Sample Problems: Instructions: A table of candidate materials has been provided at the end of sample problem 2. The table lists some of the material properties that you will need to know in order to solve the following problems. Problem A will be solved by your instructor, and you will then be asked to solve problems 1 & 2. A. You have been asked to select a material that will be forged into a crescent wrench.

a. Which of the materials in the table meet this requirement?

b. The component needs to be strong and inexpensive. Which material would you select from the candidate materials in part (a)?

1. Congratulations! You graduated with an engineering degree, and you have landed a job at

General Motors. You first task is to select the material from which the new headlight and taillight covers will be made. The candidate materials are listed in the table at the end of this exam. Since the estimated output of the car model that you are working on is more than 500,000, management has decided that the headlight and taillight covers will be injection molded.

a. List the candidate materials.

b. Since headlights can be damaged by rocks and other road debris, you will want to select a material that is strong and tough. List your material selection.

c. Name another property of the selected material that is critically important for a headlight cover.

58

2. You decided that you didn’t like the automotive industry, and you now have a job with at a power plant. You have been asked to select the material for a heat exchanger that will be designed to cool superheated steam back to water. The steam temperature will be superheated to 300ºC. The heat exchanger’s design is quite complex with multiple vanes sticking out to assist in cooling the steam to water. You only need 5 of these components; so, management has chosen sand casting as the manufacturing method.

a. List the candidate materials.

b. Your power plant is operating with a very strict budget to minimize costs due in part to the increased cost of natural gas used to power the generators. You want to keep costs below $10,000 per m3. List the remaining candidate materials.

c. Since you are seeking a material that is good for heat exchanging, what material property is critically important for your heat exchanger.

d. What is your final material choice?

59

Lecture 5 - Materials Selection in Engineering Table of Material Properties

Material Class

Candidate Material

Price ($/kg)

Density (kg/m3)

Thermal Properties

Electrical Properties

Optical Properties

Fracture Toughness (Pa/m2)

Tensile Strength (Pa)

Max Service Temp (ºC)

Melting Temp (ºC)

Available Processes

Ceramic Alumina 4.92 3,980 Poor conductor

Good insulator

Opaque 4.80E+06 6.65E+08 1,841 2,096 Powder methods

Ceramic Borosilicate Glass

4.92 2,300 Poor insulator

Good insulator

Transparent 7.00E+05 3.20E+07 460 N/A Powder methods

Metal Aluminum 2.01 2,900 Good conductor

Good conductor

Opaque 3.50E+07 5.50E+08 207 677 Rolling, forging, die casting, sand casting, extrusion, powder methods

Metal Cast Iron 0.66 7,250 Poor conductor

Good conductor

Opaque 5.40E+07 1.00E+09 450 1,250 Die casting, sand casting

Metal Copper 4.92 8,940 Good conductor

Good conductor

Opaque 9.00E+07 5.50E+08 347 1,082 Rolling, forging, die casting, sand casting, extrusion, powder methods

Metal Low Alloy Steel

1.07 7,900 Good conductor

Good conductor


Metal Titanium 65.60 4,800 Poor conductor

Good conductor


Thermoplastic Acrylic 2.71 1,220 Good insulator

Good insulator

Transparent 1.60E+06 7.96E+07 57 N/A Blow molding, compression molding, injection molding

Thermoplastic Polycarbonate 4.92 1,210 Good insulator

Good insulator

Optical quality

4.60E+06 7.24E+07 144 N/A Blow molding, compression molding, injection molding

Thermoplastic Polyethylene 1.26 960 Good insulator

Good insulator

Translucent 1.72E+06 4.48E+07 127 N/A Blow molding, compression molding, injection molding

Thermoset Phenolics 2.21 1,320 Good insulator

Good insulator

Opaque 1.21E+06 6.21E+07 157 N/A Compression molding

Thermoset Polyester 1.72 1,400 Good insulator

Good insulator

Transparent 1.70E+06 8.96E+07 128 N/A Compression molding

60

Lecture 6 - Manufacturing in Engineering



•Outline–Manufacturing Process Selection–Manufacturing & Processing Methods

Lecture 6 Topics


• Choice depends on:– The material from which the component is to be

made.– The size, shape, and dimension tolerances for the

component.– The number of components to be manufactured.

Process Selection

61



• Each process is characterized by:– The materials it can handle.– The shapes it can make and the dimension

tolerances it can achieve.– The complexity and size of the shape it can make.– The effect the process has on the material’s

properties.

Process Selection


• Finding the ______________ between design requirements and process attributes– Iterative procedure– Interaction between function, material, shape, and

process are taken into account.

Process Selection

62



Raw Material

Casting Methods

Gravity,Pressure,

Die Casting

PressureMolding

PolymerMolding,

GlassMolding

DeformationProcessing

Roll,Forge,

Draw, Press

PowderMethods

Sinter, Slipcast,Hot Isostatic

Pressure

SpecialMethods

Lay-UpCVD,

Electroform

MachiningCut, Turn, Plane,

Drill, Grind

Heat TreatQuench, Temper Steels,

Age-Harden Al-Alloys

JoiningBolt, Rivet, Weld,Braze, Adhesive

FinishPolish, Plate,

Anodize, Paint

Class of Manufacturing Processes

63

Manufacturing Process

Relative Tooling Costs

Relative Equipment Costs

Relative Labor Costs Materials Shapes

Surface Finish

Economic Batch Sizes Examples Additional Comments

Sand Casting

Die Casting

Compression molding

Transfer molding

Blow molding

Injection molding

Rolling

Forging

Extrusion

Powder sintering

Machining

Joining

Fastening


64



• Sand casting

Sources: http://www.imp.mtu.edu/index.html

http://www.dansworkshop.com/Sand%20castings%20and%20patterns.shtml

Materials Science: A Multimedia Approach, John C. Russ

Casting Methods


• Die casting

Source: Materials Selection in Mechanical Design, Michael F Ashby

Casting Methods

65



• So, which one do we choose?– It depends

Source:Materials Selection in Mechanical Design, Michael F Ashby

Casting Methods


• Compression molding• Transfer molding


Pressure Molding

66



• Blow molding

Source: Materials Selection in Mechanical Design, Michael F Ashby

Materials Science: A Multimedia Approach, John C. Russ

Pressure Molding


• Injection molding– > 50% of polymer components

are manufactured by this method

Source: http://www-materials.eng.cam.ac.uk/mpsite/process_encyc/default.html

Materials Selection in Mechanical Design, Michael F Ashby

Pressure Molding

67



• Rolling– Cold rolling– Warm rolling– Hot rolling

Sources: Materials Science: A Multimedia Approach, John C. Russ

Deformation Processing


• Forging– Example Closed-die

forging• A heated blank is placed

between 2 halves of a die• A single compressive

stroke squeezes the blank into the die to form the part.

Sources: http://www-materials.eng.cam.ac.uk/mpsite/process_encyc/default.html



68



– Closed-die forging (cont)• Once the die halves have

separated, the part can be ejected immediately using an ejector pin.

• The waste material, called flash, is removed later.




• Extrusion

Source: http://www.aec.org/cyberg/process.html#a1



69



• Powder sintering• Hot isostatic pressing (HIPing)


Powder Methods


• Cutting• Turning• Drilling• Milling• Grinding


Machining

70





• Welding• Mechanical joining

Joining & Fastening

71

Lecture 6 – Manufacturing in Engineering

Manufacturing Method Sample Problem Based on your notes from lecture on manufacturing processes, match the following items to be manufactured with the appropriate manufacturing process. Note some methods may be used more than once and some possibly not at all!!

______ 500 items of steel; complex shape; rough surface finish acceptable

A. Die casting

______ Aluminum for window frames

B. Blow molding

______ 50,000 large gears of steel; simple shape; good surface finish required

C. Rolling

______ 25,000 items of aluminum; simple shape; good surface finish required

D. Sand casting

______ Structural I-beams of steel

E. Forging

______ 10,000 ceramic components

F. Injection molding

______ 100,000 plastic bottles

G. Extrusion

______ Copper pipes for household plumbing

H. Powder sintering

______ 100,000 small, plastic gears for a toy; good surface finish required, simple shape

72



•Outline–Biomedical Engineering Defined–Examples of Topical Areas in BME

Lecture 7 Topics


• “…the application of engineering science and technology to problems arising in medicine and biology. In principle, the intersection of each engineering discipline with each discipline in medicine or biology is a potential area of biomedical engineering application.”(Plonsey)

Definition of Biomedical Engineering

73


Biologic Effects of Electromagnetic

Fields

Clinical Engineering

Biotechnology

Medical Imaging

Medical Informatics

Prosthetic Devices & Artificial Organs

Rehabilitation Engineering

Medical & Biologic Analysis

Biomedical Instrumentation

Physiologic Modeling,

Simulation, & Control

Biosensors

Biomaterials

Biomechanics

Biomedical Engineering


•• Osteoporosis researchOsteoporosis research–– Collaborations with Biochemist, Radiologist, & Collaborations with Biochemist, Radiologist, & NephrologistNephrologist at UT at UT

Southwestern Medical Center, Dallas, TX Southwestern Medical Center, Dallas, TX •• Mouse or rat animal modelMouse or rat animal model•• Mechanical testing of femoraMechanical testing of femora

Biomechanics & Biomaterials at Baylor

74


•• Total Knee Replacement ResearchTotal Knee Replacement Research–– CCollaboration with orthopaedic surgeons at Scott & White ollaboration with orthopaedic surgeons at Scott & White

Hospital, Temple, TXHospital, Temple, TX•• Artificial human tibiaArtificial human tibia•• Mechanical testing for initial stability of tibial componentMechanical testing for initial stability of tibial component



•• Tissue welding of torn meniscusTissue welding of torn meniscus–– Collaboration with Dr. Kane, Dept of Chemistry & Collaboration with Dr. Kane, Dept of Chemistry &

BiochemistryBiochemistry•• Model in bovine meniscusModel in bovine meniscus

AF

=σ


75


• Dr. Brian Garner– Visible Human Male

Dataset• Musculoskeletal model

of the upper limb

Physiologic Modeling, Simulation, & Control at Baylor


• Lower limb prosthetics– Flex-Foot

• Returns 95% of the energy stored making it the highest energy storage and release prosthetic foot in the industry

– Real need worldwide is for low cost lower limb prosthetics for third world countries

• Land mines

http://www.ossur.com/template1.asp?PageID=1


76



Fields


Biotechnology

Medical Imaging

Medical Informatics







Biosensors

Biomaterials

Biomechanics



• Noninvasive Pulse Oximeter– A source of light originates from the

probe at two wavelengths (650nm and 805nm).

– The light is partly absorbed by hemoglobin, by amounts which differ depending on whether it is saturated or desaturated with oxygen.

– By calculating the absorption at the two wavelengths the processor can compute the proportion of hemoglobin which is oxygenated. http://www.nda.ox.ac.uk/wfsa/html/u05/u05_003.htm

http://www.dolphinmedical.com/products/pulse_oximeters/oximeters.html

Biosensors

77


• Implantable Cardiac Pacemakers – Medtronic

• 80% of the world market for pacemakers• Based in Minneapolis, MN

http://www.medtronic.com/



• Ultrasound– Obstetrics

• Diagnosis and assessment of early pregnancy

– Cardiology• Depicts blood flow• Visualizes heart structures

– Urology• Visualize kidney stones• Measure blood flow through kidneys

http://www.ob-ultrasound.net/

http://www.howstuffworks.com/ultrasound4.htm

Medical Imaging

78


• Prevention of electromagnetic interference (EMI) with medical telemetry systems.– Most wireless medical telemetry devices.

• Secondary users (must accept interference from and not interfere with primary users)

• Primary users are:– Commercial broadcast TV bands– Private land mobile radio service (PLMRS) bands.

– In 1998, Baylor Medical Center in Dallas and local digital TV (DTV).

– In 2000, FCC established wireless medical telemetry service (WMTS).




Fields


Biotechnology

Medical Imaging

Medical Informatics







Biosensors

Biomaterials

Biomechanics


79


• Vaccine Production – Finding and developing the vaccine is just the beginning!

• Engineers are necessary for mass production of vaccines (i.e., chemical engineers)

http://www.gatesfoundation.org/globalhealth/infectiousdiseases/vaccines/default1.htm

Biotechnology

80

Documents

Lecture 1 Topics - Mars at UMHB | Department of …mars.umhb.edu/~wgt/engr1310/2007/Reading Assignment 3.pdf · American Heritage Dictionary Defining ... – Little significant research