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[FAQ]

1) For polymers it can be difficult to separate the elastic strain from the plastic strain (as you would have to do to prepare the input curve for MAT_024 from a tensile test result) because the stress-vs-total strain curve at high strain values can be steeper than the initial elastic modulus. In those cases, it is easier to input the stress-vs-total strain curve as with MAT_089. 2) MAT_089’s ability to have failure strain as a function of strain rate is useful for polymers, some of which become more brittle at high strain rates. 3) Unlike MAT_024, the hardening slope of MAT_089 can be larger than the initial modulus. The unloading/reloading stiffness of MAT_089 is equal to the maximum tangent stiffness attained before the unloading occurs. On the other hand, MAT_024 unloads/reloads always with the initial modulus, therefore, the hardening slope in the MAT_024 should not exceed the initial modulus. 4) In years gone by, before *MAT_ADD_EROSION was added to the code, MAT_089’s basing failure on the maximum principal strain (rather than plastic strain) would have been a fourth point on the list. Additional information can be found in the remarks for *MAT_PLASTICITY_POLYMER in the LS-DYNA Manual Volume II.