Change in material model during fulll restart

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Wong Ming Hao

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Aug 16, 2025, 1:25:50 AMAug 16
to LS-DYNA2
Dear all,

I am conducting a blast simulation, followed by a full restart for a static test. May I know if it is possible to change the material model of the damaged part to a different material model in the restart analysis?

Thanks,
Ming Hao

James Kennedy

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Aug 16, 2025, 2:36:29 PMAug 16
to Wong Ming Hao, LS-DYNA2

Dear Ming,

 

Changing material models during a full restart in LS-DYNA

 

Yes, it is possible to change material models in LS-DYNA during a full restart. 

 

Here's how it generally works

 

Full Restart: You'll need to perform a full restart, as it offers the most flexibility for model modifications.

 

Restart Input Deck: In the full restart input deck, you'll need to re-define the parts for which you want to change the material model.

 

Specify the New Material: Within these re-defined parts, you can then specify the new material model and its properties.

 

*STRESS_INITIALIZATION: For pre-existing parts carried over into the full restart, you must include the *STRESS_INITIALIZATION command in the restart input deck. This ensures that the stress, strain, and displacement fields from the previous analysis are correctly initialized in the new restart run. 

 

Important considerations

 

Material History Variables: LS-DYNA carries over stress and strain information from the previous run. If the new material model uses different history variables, you might need to adjust or initialize them properly. Consult the LS-DYNA user manual for details on handling specific material models and their history variables during restarts.

 

Compatibility: Ensure that the new material model is compatible with the existing element types and simulation setup.

 

Limitations: While full restarts offer considerable flexibility, there are some restrictions. For example, you cannot change the element connectivity (mesh topology) of retained elements, and adaptive meshing is not supported in full restarts, even if present in the initial run. 

 

In summary

 

By utilizing the full restart feature and carefully defining the parts with the new material models in the restart input deck, you can successfully change material models in your LS-DYNA simulation. Remember to manage material history variables and consult the user manual for model-specific guidelines. 

 

Sincerely,

James M. Kennedy

KBS2 Inc.

August 16, 2025

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