Simcenter Nastran user-defined material models

The user-defined materials capability (also referred to as UMAT), lets you pass your own proprietary material models, such as elastic, plastic, and creep, to the Simcenter Nastran solver using a customization of the standard materials dialog box. You can also use the UMAT capability to enhance or override existing material models.

When you define a custom material model, the software writes the custom properties to the Simcenter Nastran solver deck. However, only your Simcenter Nastran UMAT subroutine performs the calculations for the custom properties. Your proprietary material calculations remain only in your subroutine.

In Pre/Post, your user-defined material model properties appear in the materials dialog boxes on a page named User Models - Simcenter Nastran.

The UMAT capability differs from the custom materials capability because material properties are proprietary in UMAT.

Material functions

When a material has UMAT properties, your users can still use the standard Material functions (create, edit, assign, override, export material to a material library file, delete, update, and so on) on the material. Additionally, users can modify the configurable properties on the loaded library material and specify State Variable Output Requests.

State Variable Output Requests

A state variable, such as displacement, stress, strain, and so on, describes the mathematical "state" of a system. A set of state variables describes enough about the system to predict its future behavior.

In Simcenter Nastran, the UMAT subroutine can compute standard state variables and user-defined state variables. You use the user-defined state variables to pass data in addition to the standard state variables between the solver and software. The definitions of the user-defined state variables are stored only in the subroutine's source code, which keeps your definitions proprietary.

The State Variable Output Requests in Pre/Post instruct Simcenter Nastran to write the computed state variable values to the Simcenter Nastran result file. After the Simcenter Nastran computation, Pre/Post reads and post-processes them as scalar quantities.

For example, you may want to compute and display quantities between time steps.

Supported solvers and analysis types

Solver	Analysis Type
Multiphysics	Structural
Coupled

Where do I find it?

Adding a material model to a material definition

Application	Pre/Post
Prerequisites	A FEM file, idealized part, or master model part as the work part and displayed partSupported solver and analysis typeXML file that describes the custom propertiesSimcenter Nastran UMAT subroutine
Command Finder	Manage Library Materials Manage Materials Assign Materials
Location in dialog box	Material Library Manager dialog box→right-click a material from your Site MatML Library→Edit Library Material(s)→User Models - Simcenter Nastran pageType list→Isotropic, Orthotropic, Anisotropic, or Damage Interface→Create →User Models - Simcenter Nastran page

Modifying a library material

Application	All
Prerequisite	A FEM file, idealized part, or master model part as the work part and displayed part
Command Finder	Material Library Manager
Location in dialog box	Right-click a material

Assigning or modifying a local material

Application	All
Prerequisite	A FEM file, idealized part, or master model part as the work part and displayed part
Command Finder	Assign Materials Manage Materials
Location in dialog box	Right-click a local material

Assigning or modifying a local material by using Physical Property Table Manager dialog box

Application	Pre/Post
Prerequisite	A FEM file as the work part and displayed part
Command Finder	Physical Properties
Location in dialog box	Type = Plane Property, Generalized Plane Strain Property, Chocking Property, or Solid→Create→Choose Material →Right-click a local material

Quick links

Command reference

Pre/Post video examples

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Simcenter Nastran user-defined material models, Simcenter 3D 2021.1 Series

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