*USER MATERIAL

Optional parameters

EFFMOD

This parameter applies only to Abaqus/Explicit analyses.

Include this parameter if the effective bulk modulus and shear modulus are returned by user subroutine VUMAT. Abaqus/Explicit computes the stable time increment using the returned values.

HYBRID FORMULATION

This parameter applies only to Abaqus/Standard analyses and is relevant only for hybrid elements.

Set HYBRID FORMULATION=INCREMENTAL (default) to use an incremental Lagrange multiplier–based formulation.

Set HYBRID FORMULATION=TOTAL to use a total Lagrange multiplier–based formulation.

Set HYBRID FORMULATION=INCOMPRESSIBLE to define an incompressible material response.

TYPE

Set TYPE=MECHANICAL (default) if the constants are used in defining the mechanical behavior of the material.

Set TYPE=THERMAL if the constants are used in defining the thermal constitutive behavior of the material.

If both the user-defined mechanical and the user-defined thermal behavior of the material are being modeled, the USER MATERIAL option should be repeated in the material data block such that each value of the TYPE parameter is used.

UNSYMM

This parameter applies only to Abaqus/Standard analyses.

Include this parameter if the material stiffness matrix, $\partial \mathrm{\Delta }\mathit{\sigma }/\partial \mathrm{\Delta }\mathit{\epsilon }$, is not symmetric or when a thermal constitutive model is used and $\partial \mathbf{f}/\partial \left(\partial \theta /\partial \mathbf{x}\right)$ is not symmetric. This parameter causes Abaqus/Standard to use its unsymmetric equation solution procedures.