materials

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MEE 312 02 Engineering Materials

Homework 5

Cold working and Annealing

Due: Friday 3/11/2016

Dear students,

This assignment is intended to refresh your memory on the different concepts we learned in this chapter.

You have four questions in this assignment. For all these questions, you can work together in groups but I

expect to see individual copy of the assignment. You can use this assignment sheet as a template to fill in

your answers and turn it in via Isidore.

The first two questions are conceptual.

You don’t have to go into detail on the third question. Just explain briefly what you understood from each

topics. This will help you when you prepare for the exam.

We discussed the fourth question in class so you should be able to do it without any problems.

If you have any questions, please let me know.

Question 1: (Annealing)

Fill in the table below as it relates to annealing:

Stage Recovery

Change in

microstructure New grains nucleate Grains Grow

Change in

properties

Further reduction in

strength, further

increase in ductility

Temperature Below Trc  Trc

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Question 2: (Cold working)

Some of the properties of AA 2024 (Matweb) are show below:

Properties

UTS 27000 psi

Yield strength 11000 psi

Modulus of Elasticity 10600 ksi

1. Draw a stress-strain diagram for AA 2024 (conceptual). Annotate the properties along with values

shown in the table above in the stress-strain diagram.

2. On the same stress-strain curve, using a dashed line, please construct the stress strain curve for the

AA 2024 material that had been subjected to the 50% cold work. Explain the following:

a. Why did you estimate the modulus to be as you drew it?

b. Would you estimate the hardness to be higher or lower for the cold worked material and

why?

c. Would you expect the % elongation to be higher or lower for the cold worked material and

why?

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Question 3: (Chapter refresher)

Briefly explain in a minimum of one sentence about what you understood from each of the topics shown

below.

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Question 4: (Finding crystalline structure)

Use the attached data file from the tensile test of a certain material to find its crystalline structure.

This to attach with this homework for this problem:

1. Screenshot of your excel sheet showing the columns you calculated

2. Graph from which you calculated the strain hardening exponent

3. Value of strain hardening exponent and the corresponding crystalline structure.