Engr 36 material

Problem 2 (8 Points)

The carrot pictured below was loaded in pure torsion to the point of failure. Based on the failure surface shown, would you characterize the carrot as (CIRCLE ONE):

a) BRITTLE b) DUCTILE

Problem 1 (12 Points)

Make a formula sheet for the topics of torsion and bending covered on this exam and append to the end.

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ENGIN 36 Exam #2

Take Home Exam

April 30, 2020

Laney College

Name ________________________________________________________

Read all of the instructions below before starting the exam

1. Turn in the exam on Canvas by 11:00 PM on Sunday, May 3. 2. Be sure to read the instructions for each problem carefully. Read the question

statement fully and be sure to answer all components of the question. 3. You may use your homework, the textbook, references posted to Canvas, and other

study references as work through the exam. You may not consult with classmates. 4. Show all of your work! It’s much easier for me to give you partial credit if you clearly

document all of your steps when solving a problem. 5. Remember to write your units in your answer! 6. Box your answers! 7. If you run into algebra or math problems, write how you would have continued to solve

the problem to receive partial credit. 8. Extra paper is available to show your work. Staple this paper to the back of your test.

Sign the honor statement below after finishing the exam (a digital “signature” is acceptable)

I have neither given nor received help on this work, nor am I aware of any infraction of the Honor Code.

Problem 3 (32 Points)

PART 1

a) What is the maximum shear stress at point C?

What is the angle of twist between points A & B? Between A & C?

If rod BC were made of brass instead (G = 39GPa), would the angle of twist from A to C be (CIRCLE ONE):

a) BIGGER b) SMALLER

Why?

400mm 625mm

36m m

60m m

The shaft shown is comprised of two solid aluminum rods (G = 27GPa) bonded together at point B. The shaft is fixed at point C and is subjected to the torsional forces shown. A

B

C TA=800N × m

TB=1,600N × m

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PART 2

If tall=70 MPa in shaft BC and fall=4 ° between B & C, what is the minimum allowable diameter of shaft BC (to the closest mm)?

a) 53 mm

b) 56 mm

c) 32 mm

d) 60mm

Problem 3 cont'd

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Problem 4 (18 Points)

For the following multiple choice questions, CIRCLE ONE answer.

1. Which of the following is the appropriate schematic depiction of the transformed section for the reinforced concrete cross-section shown?

2. Which of the following is the appropriate depiction of the transformed section for the composite cross-section shown, if Material 1 is chosen as the reference material and E2=2×E1 ?

a) b) c)

Explain your selection:

a) b) c)

Composite cross-section:

Composite cross-section:

Material 1 Material 2

Explain your selection:

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3. Which loading diagram matches the given shear and moment diagrams shown?

Note, the distributed load has a magnitude of w and the the point load has a magnitude of P= w× L

3 . A

reference line divided into 6 equal segments has been provided.

Problem 4 cont'd

V

M

a)

b)

c)

c)

L

w

w

w

P

P

w

P P

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Problem 5 (30 Points)

A sign is supported on a a steel post that is fully fixed at its base, as shown in the diagram. Considering only the weight of the sign, find the maximum compressive and tensile normal stresses at the base of the post.

Be sure to draw the free body diagram at the base of the post and any other diagrams you think would be useful.

A B

14

6 ft

A B y

x

A

B

y

x

X X

Section X-X

4"

6"

3 8

3 8

3 8" 3 8" W = 6,000 lbs

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Which grade of steel (a.k.a. allowable normal stress) would you use to design the post (CIRCLE ONE)?

a) 36 ksi

b) 42 ksi

c) 50 ksi

d) 60 ksi

If the steel post was replaced with a concrete post, which of the following two sections should be used (CIRCLE ONE)?

a) b)

Problem 5 cont'd

A B A B

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