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Download Abaqus Analysis User`s Manual, vol3
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MECHANICAL USER MATERIAL Use of UMAT with other subroutines Various utility subroutines are also available in Abaqus/Standard for use with subroutine UMAT. These utility subroutines are discussed in “Obtaining stress invariants, principal stress/strain values and directions, and rotating tensors in an Abaqus/Standard analysis,” Section 2.1.11 of the Abaqus User Subroutines Reference Manual. User subroutine UMATHT can be used in conjunction with UMAT to define the constitutive thermal behavior of the material. The solution-dependent variables allocated in the material definition are accessible in both UMAT and UMATHT. In addition, user subroutines FRIC, GAPCON, and GAPELECTR are available for defining mechanical, thermal, and electrical interactions between surfaces. Use with other material models A number of material behaviors can be used in the definition of a material when its mechanical behavior is defined by user subroutine UMAT or VUMAT. These behaviors include density, thermal expansion, permeability, and heat transfer properties. Thermal expansion can alternatively be an integral part of the constitutive model implemented in UMAT or VUMAT. For a material defined by user subroutine UMAT or VUMAT, mass proportional damping can be included separately (see “Material damping,” Section 23.1.1), but stiffness proportional damping must be defined in the user subroutine by the Jacobian (Abaqus/Standard only) and stress definitions. Stiffness proportional damping cannot be specified if the user material is used in the direct steady-state dynamics procedure. Elements User subroutines UMAT and VUMAT can be used with all elements in Abaqus that include mechanical behavior (elements that have displacement degrees of freedom). 23.8.1–6 Abaqus Version 6.6 ID: Printed on:
