Hi Expert,

 I'm a newer of Abaqus. I was trying to compute a simple compression problem using Mohr-Coulomb model. I found the slope of stress-strain curve from the results is double of that defined in the input file. I don't know what's cause it or my understand of the slope is wrong.

Only one 8 node C3D8 element is involved. To simplify the question, let the friction angle be 0, it reduces to a Tresca model actually. The material is defined as:

*ELASTIC, TYPE=ISOTROPIC
 3.350000E+07, 2.000000E-01,
*MOHR COULOMB
 0.,0.
*MOHR COULOMB HARDENING
 10000.,0.
 3360000.,1.

The hardening slope defined above is 3.35E+6.

Checking the Abaqus results, I found the slope of equivalent_plastic_strain - compression_stress in the plastic stage is 6.7E+6, just double of that defined in the input file! But the initial yield is correct, i.e. 2*Cohesion_yield_stress=20000.

Only if I defined the hardening slope as 1.675E+6 in the input file, the slope of equivalent_plastic_strain - compression_stress gets the expected value.

So is it normal? Is my understand on the slope definition correct?

Thx a lot!