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Effect of Material Model on time required for simulation in FEA.

Altair Forum User

I had performed simulation of Incremental sheet forming process in Hyperworks 12.0. In this analysis I compared the two material law (Law52 and Law2) keeping all conditions same.

The Gurson (Law52) based model takes 26.3 hrs for simulation while J-C (Law2) based model takes 17.23 hrs for the same analysis. Why Gurson model takes more time for analysis?

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Altair Forum User

Hi Abhishek,

Every material law has different formulations and laws. Any good simulation of models depends on the inputs provided. Any unclear or illogical data provided during material characterization will lead to uncertain results. Choosing the right material and providing the reliable material data in performing a simulation is very important.

Johnson Cook material behaves as linear elastic when the equivalent stress is lower than the yield stress and when the maximum stress is reached during computation, the stress remains constant and material undergoes deformation until the maximum plastic strain. where as the Gurson constitutive law models progressive microrupture through void nucleation and growth. It is dedicated to high strain rate elasto-viscoplastic porous metals.

Altair Forum User

Thank you George for your reply.

What I understand from your reply is that, the difference in time for simulation is due the constitutive material law.

Gurson model calculate microvoid nucleation and growth at every step and the constitutive law of Gurson model depends on many factors such as mean stress, yield stress, equivalent stress and void volume fraction. Whereas in Johnson-Cook model I am taking only strain hardening effect for simplicity.

Altair Forum User

Hi Abhishek,

The effect of time step in an explicit simulation always affects the total run time of the simulation. Material parameters plays an important role in calculation the time step.

The solution time step is inversely proportional to the speed of sound. So, if the material is stiffer (higher modulus of elasticity), the speed of sound increases resulting in a lower solution time step.

Please refer the video below for timestep in Radioss Explicit.

https://altair-2.wistia.com/medias/o0bfml9ah5