We have an exciting announcement about badges coming in May 2025. Until then, we will temporarily stop issuing new badges for course completions and certifications. However, all completions will be recorded and fulfilled after May 2025.

Ansys Learning Forum › Forums › Discuss Simulation › LS Dyna › D3 failure parameter in *MAT_015 (JOHNSON_COOK) › Reply To: D3 failure parameter in *MAT_015 (JOHNSON_COOK)

January 26, 2024 at 9:29 pm
rji229
Subscriber

Thanks for the reply. What I would like to simulate is the AZ31B magnesium alloy. The material parameters are cited from the paper linked: A constitutive and fracture model for AZ31B magnesium alloy in the tensile state - ScienceDirect

The fracture material parameters are defined below:

which are very similar to the formula in LS-DYNA user manual. In real experiment, the parameters are calculated by fitting the data measured, and the result for the paper is shown:

So when using the negative D3 value, we can generate the correct stress-strain curve. However, in LS-DYNA manual, it indicates that D3 must be positive (if negative, use the absolute value). I don't know why we need to do that.

 

Besides, I also get the same result by using both positive and negative values for the material property for calculation (same absolute value, keeping all other JC parameters the same).