Understanding User Subroutines in ABAQUS: UMAT and VUMAT Explained

Engineers can individualize their work in ABAQUS with subroutines called UMAT and VUMAT. These tools allow users to describe advanced behavior of materials that is not included in the basic material libraries of ABAQUS. Knowing how to apply subroutines is crucial for engineers, and now many of them prefer to acquire this knowledge with a proper online Abaqus UMAT course.

What is the Meaning of UMAT and VUMAT?

• You can use the UMAT module in ABAQUS/Standard to design materials under static and low-speed dynamic situations.

• ABAQUS/Explicit makes use of VUMAT to solve very fast-paced simulations.

All the programs are written in Fortran, which is the usual language for coding finite element analysis applications. During every analysis step, ABAQUS uses these routines to find out how the materials will respond according to the user’s settings.

The way ABAQUS makes use of subroutines

At the beginning of every increment in ABAQUS/Standard, subroutines such as UMAT are used twice.

• At first, we build the initial stiffness matrix.

• Second, it is important to update the stiffness based on the updated components and joints.

Later on, the function is only needs to be called once. It is through VUMAT in ABAQUS/Explicit that simulation progress is tracked for high-speed simulations.

Including Subroutines in an Analysis

To include user subroutines in an analysis, specify the name of a file with the user parameter on the ABAQUS execution command. abaqus job=my_analysis user=my_subroutine The file should be either source code (my_subroutine.f) or an object file (my_analysis.o). The file extension can be included (user=my_analysis.f); otherwise, ABAQUS will determine automatically which type of file is specified.

Restarting Simulations

When restarting a simulation, the user subroutine must be specified again, since it is not saved in the restart file (.res).

Learning ABAQUS Subroutines

Subroutines should be a key skill for people who design with their own materials. For those who are unfamiliar with Abaqus, it makes sense to take an Abaqus training or a hands-on class about ABAQUS UMAT and VUMAT online. The courses are designed to show you how to use Fortran for subroutine integration, making you ready for simulation and modeling jobs.

Pigso Learning offers an ABAQUS Subroutines UMAT Training Course designed to help engineers master user material modeling with hands-on Fortran implementation.