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I am using userdefined material model UMAT for modelling of hypoplastice constitutive model in abaqus.

I need to run dynamic analysis, so how can convert UMAT to VUMAT (fortran) subroutine.

Please tell me the procedure to convert UMAT to VUMAT, it will be of great help.

Thanking You.



I have a problem with abaqus,i'm solving a project with abaqus but during of solve of project,abaqus give me a error that i write it there:

The ratio of deformation speed to wave speed exceeds 1.0000 in at least one element. This usually indicates an error with the model definition. Additional diagnostic information may be found in the message file.

i actived distortion control but i have same error,

can i delet destroyed element during solving process?if i can please tell me about it

i'm waiting for your suggestions

The difference between UMAT and VUMAT is: UMAT is a Implicit solver, material jacobian has to be updated at each time step. The deformation gradient has to be passed from abaqus to calculate global strain

VUMAT- Explicit solver , u don need to update the Material jacobian or stiffness matrix. But the deformation gradient has to be passed to F=R.U where R is a Rotation and U is a stretch at each time step.

To get a clear understanding plz read Prof Louie's notes on Non linear FE and difference between Implicit and Explicit solvers. Rolling problems which is a high strain rate application have been solved by writing UMAT. Read papers by Lalit anand and Suriya Kalindi 


Nanyang Technological University, Singapore

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