9 Hidden Built-in Material Models (User Subroutines) in Abaqus

Did you know that Abaqus contains a secret library of highly advanced material models that are not accessible through the standard Abaqus/CAE graphical interface?
Many FEA engineers spend weeks writing complex Fortran codes to simulate advanced material behaviors. However, Abaqus has several hidden built-in material models in the form of pre-compiled Fortran user subroutines (such as UMAT, VUMAT, UVARM, and UDMGINI). The source codes exist in the Abaqus installation directory, but they are kept out of the standard UI, often reserved for advanced research or specific industrial applications.
In this guide, we will unveil 9 of the most practical built-in user subroutines in Abaqus that can save you months of coding and debugging.

Why Use Built-in Abaqus User Subroutines?

Writing a UMAT or VUMAT from scratch requires deep knowledge of continuum mechanics and Fortran programming. Even after writing the code, Verification and Validation (V&V) can take weeks. By utilizing these hidden built-in models, you are leveraging Dassault Systems’ rigorously tested algorithms.
(💡 Pro Tip: If you want to skip subroutines entirely and get instant access to over 1,400 calibrated materials, download our Abaqus Material Library (MatLib) plugin).

Top 9 Hidden Material Models in Abaqus

 1. Johnson-Holmquist (JH-1, JH-2, JHB) for Ceramics

To predict the extreme damage and fracture of brittle materials like ceramics or glass under ballistic impact, the Johnson-Holmquist models are integrated as a built-in VUMAT for Abaqus/Explicit. It supports element deletion and offers excellent solution speed. This model requires 23 material inputs and generates 8 output variables for accurate visualization. (🚀 Ready to use this model? Download our complete Abaqus VUMAT JHB and JH-2 Ceramic Model package, which includes the tutorial and verified simulation files).

2. Holmquist-Johnson-Cook (HJC) Concrete Model

Simulating the mechanical response of concrete subjected to high strain rates, large strains, and extreme pressures (like explosive detonations) is incredibly difficult. The HJC constitutive model is available as a built-in VUMAT. It takes 23 material property inputs and reliably captures concrete crushing and failure behavior.

3. LaRC05 Composite Failure Criteria

For laminated polymeric-matrix fiber-reinforced composites, the LaRC05 failure criteria is a game-changer. It is implemented in two ways for Abaqus/Standard:
UVARM: Evaluates the LaRC05 damage criterion and provides damage tolerance outputs for both 2D and 3D stress states.
UDMGINI: Used with XFEM-enriched elements to evaluate the exact onset of crack initiation and propagation in 3D structures. (🚀 Master this failure model: Get our comprehensive Abaqus Tutorial: LaRC05 Failure Criterion For Fiber-Reinforced Composites to learn the exact step-by-step implementation. Also, explore our guide on the Hashin Damage Abaqus Model).

 4. Multilinear Kinematic Hardening (UMAT) for Cyclic Plasticity

Based on the Bestselling Overlay model, this built-in UMAT allows engineers to simulate complex cyclic plasticity, multilinear hardening, and the Bauschinger effect. It is an absolute necessity for simulating fatigue and ratcheting in metallic aerospace and automotive components.

5. UMAT / VUMAT for Nitinol Super elasticity

Simulating shape memory alloys (SMAs) like Nitinol is critical in the medical industry. Abaqus includes a robust built-in material model to capture the reversible phase transformations between Austenite and Martensite. This allows for highly accurate analysis of Nitinol stents using Abaqus. (Struggling with SMA calibration? Download our free Calibrate Nitinol Material Plugin to automate the entire process).

 6. Molded Plastics (VUMAT)

For crash and drop-test applications, Abaqus/Explicit hides a constitutive model specifically for molded thermoplastics. It accounts for orientation-dependent plasticity and failure properties, making it applicable to both fiber-reinforced and non-reinforced molded plastics.

 7. VFABRIC for Woven Fabrics

From automobile airbags to parachute deployment and military protective vests, woven fabrics undergo massive deformations. The Abaqus FABRIC model is a VFABRIC user subroutine designed to precisely simulate the unique wrinkling and stretching behavior of woven materials in Abaqus/Explicit.

8. VUMAT for Fabric Reinforced Composites

This built-in VUMAT models fabric-reinforced plies as a homogeneous orthotropic elastic material capable of sustaining progressive stiffness degradation (due to fiber/matrix cracking) and plastic deformation under shear loading. It supports element deletion and provides 16 visualization output variables.

 9. Bergstrom-Boyce Hysteresis for Viscoelastic Rubber

Viscoelastic rubber-like materials (elastomers) exhibit significant hysteresis during cyclic loading due to frictional sliding of molecular chains. Based on the famous Bergstrom-Boyce equations, this Abaqus/Explicit VUMAT flawlessly captures the large-strain, time-dependent, and strain-rate-dependent hysteretic behavior of both filled and unfilled rubbers.

How to Implement These Models in Your Projects?

Since these models are hidden from the Abaqus/CAE graphical interface, they must be called using specific keyword edits in your .inp file, or activated through specialized Python scripts.
If you want to bypass the complexity of keyword editing entirely, you can integrate all these models flawlessly into your CAE environment using our custom add-ons and plugins.