There are many types of subroutines in the Abaqus, but here I’m going to tell you the most important ten of them:
- UMAT and VUMAT subroutines: The UMAT is an acronym for “user-defined material” and it enables you to input material constants to create a custom mechanical model. It can also be used for creating user-defined thermal material models, known as UMATHT. This subroutine utilizes Cauchy stress components or true stress. While UMAT is used for the ABAQUS standard solver, the VUMAT subroutine is used for ABAQUS explicit solver. These subroutines are useful for defining a material’s mechanical constitutive behavior and can be called at all material calculation points of elements that include a user-defined material behavior in their definition. Additionally, these subroutines can define any procedure that involves mechanical behavior.
- USDFLD and VUSDFLD subroutines: The user-defined field (USDFLD) subroutine, which is used for the standard solver, and the VUSDFLD subroutine, which is used for the explicit solver, enable you to modify the values of field variables at a specific material point during an increment. Essentially, this means that you can create a time-dependent definition of field variables at any material point that is available.
- DLOAD and VDLOAD subroutines: The DLOAD and VDLOAD subroutines are utilized for creating user-defined distributed loads. DLOAD is specifically designed for the standard solver, while VDLOAD is used for the explicit solver. Both subroutines are capable of defining the variation in magnitude of the distributed load as a function of several parameters, including time, load integration point number, position, and element number.
- UHYPER subroutine: To establish a custom hyperelastic material behavior, the UHYPER subroutine can be applied. This subroutine can also be utilized to define the strain energy potential for isotropic hyperelastic material behavior.
- UEL and VUEL subroutines: If you need to define different element shape functions, the UEL subroutine can be utilized, which stands for user-defined element. Similarly, the VUEL version is used for the explicit solver, as in the previous examples. It’s important to note that this subroutine is geared towards advanced users only, as even the simplest applications require significant coding effort from the user. When the UEL subroutine is implemented, it will be invoked for each element of a user-defined element type in the analysis, as needed during the current activity.
- FRIC and VFRIC subroutines: If the extended versions of the classical Coulomb friction model offered in ABAQUS are insufficient for your situation, and you require a more intricate definition of shear transmission between contacting surfaces, two subroutines may be useful. Specifically, if you need contact with custom friction, you can utilize the FRIC subroutine for the standard solver or the VFRIC subroutine for the explicit solver.
- UMESHMOTION subroutine: To establish mesh node motion, it is necessary to use the UMESHMOTION subroutine. This subroutine enables the specification of mesh motion constraints during the process of adaptive meshing. Following adaptive meshing, this subroutine is called at the conclusion of each increment.
- HETVAL subroutine: The purpose of this subroutine is to generate internal heat during heat transfer analysis. It may be used to account for phase changes that occur during the solution, and it could be dependent on state variables such as the fraction of material that has undergone transformation.
- DFLUX subroutine: The purpose of this subroutine is to define flux that is non-uniformly distributed during a mass diffusion or heat transfer analysis. This can be achieved by defining it as a function of various parameters, such as time, position, temperature, integration point number, and element number.
- DISP and VDISP subroutines: We will now discuss the DISP and VDISP subroutines in ABAQUS, which are employed to specify prescribed boundary conditions. While DISP is utilized in the ABAQUS/Standard solver, VDISP is used for the ABAQUS/Explicit solver. These subroutines can be particularly helpful when attempting to define boundary conditions that are both time-dependent and location-dependent, which cannot be supported by the standard ABAQUS features.
You can find some applications of these subroutines in research articles and industries in the articles below, which will help you to understand the functionality and capability of these subroutines:
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