User Defined Material Modeling in LS-DYNA

Objective

The user-defined subroutines in LS-DYNA allow the program to be customized for particular applications. The usermat allow constitutive models to be added to the program. This course explains and demonstrates when to consider the use of such user subroutines and how to go about their developments. Detailed descriptions are given of the data required for the usermat, the additional statements to be included, the variable that are available within the subroutine, and the freedom the user has in defining complex material models. Examples of various user subroutines and flow charts are used to illustrate the points made in the lectures.

Audience

This course is recommended for engineers with LS-DYNA and DYNA3D experience as well as knowledge in programming in FORTRAN or any other language and the finite element method.

Notes

The instructor for this course is Dr. Ala (Al) Tabiei. Please contact Al for a more detailed course description (atabiei@aol.com, 513-331-9139). Lectures begin daily at 9:00 a.m. and run until 5:30 p.m.

Contents

  • Introduction to Nonlinear Continuum Mechanics
  • The Nonlinear Finite Element Dynamic Equations
  • Introduction to Inelasticity and Plasticity
  • How to go about writing usermat and common practice
  • UMAT interface and UMAT variables
  • UMAT conventions
  • UMAT formulation aspects
  • UMAT subroutines
    • Isotropic Material
      • Elastic material (beam, shell, solid)
      • Elastic plastic-kinematic-isotropic (shell, solid)
      • Strain rate effect
    • Orthotropic Material
      • Damage modeling
      • Composite macromechanics and micromechanics with progressive damage
    • Hyperelastic material and rubber
    • Viscoelastic material
  • Available variables in UMAT
  • How to post process UMAT in LS-PrePost
  • Several examples will be demonstrated
  • User defined mat in Implicit LSDYNA

There will be several examples, which are designed to understand and reinforce the lectures and the concepts presented. The course will provide users with experience of running and trouble-shooting LSDYNA usermat analysis.