Learning Forum

[Haiquan]

Hello

I am using Ansys General Non-linear Materials data source for copper alloy simulation. Yield stress is 280Mpa, yield strain should be 280Mpa/110000Mpa=0.0025 

When I check the Equivalent (von-Mises) Stress and Equivalent Total Strain, I find that only a small area exceeds the yield stress 280Mpa, but a large area exceeds the yield strain 0.0025.

In my understanding, if the material exceeds the yield strain, it should exceed the yield stress too. How to explain this result? I use second order solid element and put 6 elements through the thickness, all stress and strain are averaged display results, Ansys version 2020 R1. Thank you in advance!

[1shan]

Lets say you apply a force, yield the structure and then remove the load. After unloading the structure would be in a stress free state but with a permanent plastic strain right? Thus it would be incorrect to say that if the material exceeds the yield strain, it should exceed the yield stress too. Could you take a node and plot a curve of equivalent stress vs total strain for the entire loading history? Something like https://www.youtube.com/watch?v=ai-9bRyeoqA. Then compare the plot with your input material stress-strain data.
Regards Ishan.

[Haiquan]

Thank you very much for your comments and the video, very helpfull video! I take 2 nodes to plot the curve, node 2 matches the material stress strain curve well, but node 1(a node through the thickness as shown below) seems very strange. I don't know why. My case is bulb insertion simualtion into the copper alloy as shown in the attachment gif file, this is not an unloading process.