UMAT User subroutine to define a material's mechanical behavior. Product: Abaqus/Standard Warning: The use of this subroutine generally requires considerable expertise. You are cautioned that the implementation of any realistic constitutive model requires extensive development and testing. Initial testing on a single-element model with prescribed traction loading is strongly recommended. References “User-defined mechanical material behavior,” Section 25.7.1 of the Abaqus Analysis User's Manual “User-defined thermal material behavior, ” Section 25.7.2 of the Abaqus Analysis User's Manual *USER MATERIAL “SDVINI,” Section 4.1.11 of the Abaqus Verification Manual “UMAT and UHYPER,” Section 4.1.21 of the Abaqus Verification Manual Overview User subroutine UMAT: can be used to define the mechanical constitutive behavior of a material; will be called at all material calculation points of elements for which the material definition includes a user-defined material behavior; can be used with any procedure that includes mechanical behavior; can use solution-dependent state variables; must update the stresses and solution-dependent state variables to their values at the end of the increment for which it is called; must provide the material Jacobian matrix, , for the mechanical constitutive model; can be used in conjunction with user subroutine USDFLD to redefine any field variables before they are passed in; and is described further in “User-defined mechanical material behavior,” Section 25.7.1 of the Abaqus Analysis User's Manual . Storage of stress and strain components In the stress and strain arrays and in the matrices DDSDDE, DDSDDT, and DRPLDE, direct components are store...
