California State University, Sacramento
Department of Mechanical Engineering
E-45--Spring 2000                                                                                    Name:

Plastic Deformation and Stress-Strain Curves

Your report must be in the following order and include:

Title Page
Results--complete the tables. Include proper literature citations.
Questions
Stress-Strain Diagrams--Neatly hand plot your data on high-quality graph paper (no engineering/calculation paper). From the data graphs pick enough points so that you can reproduce that portion of the graph effectively and "dash in" the rest of the graph making sure that you have it fit with the UTS and breaking stress and strain. Make sure your plots are properly labeled, scaled, and mounted. Include construction lines for the 0.2% offset yield strength and the elastic modulus. Also include the calculation for the elastic modulus on either the stress-strain curve or your data graph.

Data sheets and graphs

Tensile Test Results
Construct the following table for each of the materials tested.

Questions:

How did your experimental results for each tensile test compare to the literature data?
 
 
 
 
 
 
 
 
 
 

Using the Rockwell hardness of the steel specimen, compare the ultimate tensile strength from the Hardness-UTS conversions chart to the experimentally measured tensile strength. Would you say that a hardness test is a useful predictor of UTS? (note: there are not reliable hardness-UTS conversions for aluminum alloys. Too bad.)
 
 
 
 
 
 
 
 
 
 

What was the total strain in each of your samples at the 0.2% offset yield strength?  Clearly explain how you arrived at your answer.
 
 
 

For each of your specimens when the sample had a total strain of 3% (total strain=0.03), how much of the strain was elastic and how much was plastic?
 
 
 
 
 
 
 

Calculate the true breaking stress for each of your specimens. Compare these with the engineering breaking strengths for your specimens and explain why they are different.
 
 
 
 
 
 
 
 

If you were asked to design a metal support bracket for a shelf, which of the strengths (yield strength, UTS, breaking strength) would you use for a design strength? Why might you use a safety factor? Explain.
 
 
 
 
 
 
 
 
 

Describe an engineering situation in which you would intentionally plastically deform a metal. For that situation which of the strengths would be important? Explain.