hi my friends,
i am using abaqus standard Mohr-Coloumb plasticity to model uniaxial compression test, so i have sample and (upper and lower platen) to represent the compression machine , i apply the load through the movement of the upper platen, the stress strain diagram of my material is strain softening.
the problem is that when i could not increase the displacement of the platen to apply load to the sample more than 0.8% of the sample height, if i increase the displacement more than 0.8 % the model does not converge, and i got many many many messages like the system has 10 negative eignvalues.
the initial time increment is very small = 0.00001
the element type is C3D20R
best regards,
Gamal
can any one tell me how can i increase the displacement and avoid the divergent problem.