When I look at the code in Example 4.20, I see the TBPT command has two commas after TBPT and the first row has zero plastic strain and a yield stress.
TB,CAST,1,1,5,TENSION TBPT,,0.000E-00,0.813E+04 TBPT,, 1.13E-04,0.131E+05
When I look at your code, it doesn’t have two commas and the first row doesn’t have a yield stress to go with the zero plastic strain.
It is very important to pay attention to small details like this. I added a row for the zero plastic strain point and made up a number for the yield stress. Also, always use a decimal point on real numbers. I don’t know if APDL corrects this, but when I use NASTRAN, that is unforgivable.
I like to create a unit cube model to test out material models. In this case, I have made a 10 mm cube, so the area of the cube is 100 square mm. I mesh this cube with a single linear element, so my model has only 8 nodes.
One 3 faces, I set the normal displacement to 0. On one face, I apply a normal displacement. I applied a +/- 0.2 mm sawtooth profile.
I plot the Normal Stress and see the material going platstic at different levels of stress.
Below is the Accumulated Equiv. Plastic Strain (which is always positive).
Here is a link to my ANSYS 2021 R1 archive using a modified version of your code: https://jmp.sh/N9fJI5m