Elastic behavior in cp model.

[Adam-S-Yanxuan]

Hello, Professor Dodds:

I simulated a simple stretch test on a cubic geometry with a very small load using cp model. The material definition code is shown in Appendix A.
Because the applying load is very small, I am sure that no plastic deformation should taken place in this cubic if yield condition is correctly defined.
However, the simulated results showed plastic deformation was accumulated since the start of the stretch simulation.
The maximum principle stress and accumulated plastic strain are shown in Appendix B. The geometry is shown in Appendix C.

Appendix A

---

crystal 1
properties slip_type fcc elastic_type isotropic,
e 231000 nu 0.3 harden_n 1,
hardening voce,
theta_0 0.0001 voce_m 1 tau_v 5000000 tau_y 700.0
material MAR_M_002
properties cp angle_convention kocks,
n_crystals 1 angle_type degrees,
crystal_input single crystal_type 1,
orientation_input file filename 'angle',
debug off tolerance 1.0E-10

---

Appendix B

Appendix C

[rhdodds]

Hi Adam,

Please see directory verification/test74. The is a CP analysis. I would suggest starting with the
input files for test74 and change them incrementally towards the boundary conditions and material properties of interest to you.

[Adam-S-Yanxuan]

Hi, Professor Dodds:
Thank for your help, I think I noticed my fault.
The exponent n of Power-Law Slip Rate n should be set bigger, so that the resolved shear stress below critical resolved shear stress will have few impact on the slip .
However, I am still confused if there is a criteria whether a plastic flow occurred. Or, the yield condition is totally defined by the slip-rate relation:

---

I have much to learn, I'll further learn the theories in the documentation, especially the section of kinematics and generalized implicit material update algorithm.
Thank you again for your help.