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Publication Number: FHWA-HRT-04-095
Date: November 2004
Manual for LS-DYNA Soil Material Model 147
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APPENDIX A. DETERMINATION OF PLASTICITY GRADIENTS
In the following, the gradient of the yield surface in stress space is determined. The yield function is:
J3= third invariant of the stress deviator
e= material parameter describing the ratio of triaxial extension strength to triaxial compression strength
We need to find . A convenient method is:
Here, si is the stress deviator. Now, we just need to determine the coefficients C1, C2, and C3.
Note that is not defined at e = 0.5 and .
For the hardening functions, see equations 40 and 41.
In comparison with Abbo and Sloan: