Is there a way to vary the elastic modulus with respect to the strain rate using field variable in ABAQUS/Explicit?
Abdulla Alhourani, Yes, it is possible to vary the elastic modulus with respect to the strain rate using field variables in ABAQUS/Explicit. One way to do this is by defining a user material subroutine (UMAT) that incorporates the desired variation. The UMAT can be used to define the material properties of the elements in the model. The elastic modulus can be defined as a function of the strain rate using the appropriate field variable.
Engr. Tufail Thank you for the answer, but can we avoid using a UMAT and do it by the input (INP) file instead? and what would the approproiate field variable be?
In ABAQUS/Explicit, it's possible to model the variation of the elastic modulus with respect to strain rate by defining a user-defined material subroutine (UMAT). A UMAT allows you to specify custom material behavior based on field variables such as strain rate. However, implementing this functionality requires some expertise in both the material model and the ABAQUS user subroutine interface.
Here's a general outline of how you might approach this:
1. **Define Material Behavior:** Develop a constitutive model that describes the variation of elastic modulus with strain rate. This could involve empirical data fitting or using a theoretically derived model such as a power law, exponential model, or another suitable equation.
2. **Implement the UMAT:** Write a user-defined material subroutine (UMAT) in a programming language supported by ABAQUS (such as Fortran or C). Within the UMAT, you'll define how the elastic modulus varies as a function of strain rate based on your chosen model.
3. **Compile and Link:** Compile the UMAT source code and link it with the ABAQUS analysis job.
4. **Specify Material Properties:** Assign the user-defined material (UMAT) to appropriate elements in your ABAQUS model, and specify any necessary material parameters.
5. **Run Analysis:** Run your ABAQUS/Explicit analysis as usual. During the analysis, ABAQUS will call the user-defined material subroutine (UMAT) to calculate the material response, including the variation of elastic modulus with strain rate.
Here's a simplified example of what the UMAT might look like in Fortran:
```fortran
SUBROUTINE UMAT (.....)
...
C Define material properties, strains, stress, etc.
C Calculate strain rate
STRAIN_RATE = ...
C Calculate elastic modulus as a function of strain rate
MODULUS = ...
C Update stress based on the calculated modulus
STRESS = MODULUS * STRAIN
...
END SUBROUTINE UMAT
```
Please note that the specific details of the UMAT implementation will depend on your chosen material model and the complexity of the strain rate dependency. Additionally, it's crucial to validate the accuracy of your user-defined material model against experimental data or other reliable sources.
If you're not familiar with programming or material modeling, you may need assistance from someone with expertise in these areas to successfully implement a strain rate-dependent elastic modulus model in ABAQUS/Explicit. Additionally, consulting the ABAQUS documentation and user forums can provide further guidance on using user-defined material subroutines.
Dzevad Hadzihafizovic Thank you very much for the detailed reply.
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