CE 592 Homework No. 2. Due: Feb. 3

CE 592 Homework No. 2. Due: Feb. 3.

I recently purchased A572 Gr. 50 plate with 0.75 in. thickness. I requested a local vendor to perform the ASTM E8 uniaxial tension test on standard coupons from the plate. Attached is one of the raw data files that he sent me. As expected, the data resolution in the elastic range is poor, but the range of the data in the inelastic range is quite good. I request you to do the following:

1. Check the data (values of stress and strain) to make sure that it makes sense. What was the gage length? What was the cross-section area?

2. Plot the stress-strain data and see if it makes sense to you. Can you analyze the data to establish the ultimate tensile strain (eu), the ultimate stress (su), the yield stress (sy), and the strain at onset of hardening (esh). It is evident that the data does not have adequate resolution to estimate E or ey. For steels, it makes sense to peg the value of E at 29000 ksi or 30,000 ksi, and use that to estimate the yield strain ey. Please provide all these key values.

3. It is evident that I don't want to use each and every data point as input to conduct the FEM plastic analysis. So, I need to somehow idealize the data while capturing its salient features. I want to particularly capture the data trends at the onset of hardening and after it. So, I propose a simple power-law hardening model shown below.

4. Can you idealize the stress-strain curve in the form of an elastic-plastic-power law hardening stress-strain curve. You might have to edit the value of the power law coefficient (n) till you get a good representative fit. Report the comparison of the idealized curve vs. the measured curve.

5. Is there any other idealization that you would like to propose or use? Please explain your choice, and show comparisons of the idealized vs. measured curve.

6. Please make a plot of the true stress-true strain curve, and also the true stress-plastic strain curve. We will use this further to conduct inelastic analysis.