Writing User Subroutines with Abaqus Introduction The user subroutines in Abaqus allow the program to be customized for particular applications. For example user subroutine UMAT in Abaqus/Standard and user subroutine VUMAT in Abaqus/Explicit allow constitutive models to be added to the program, while user subroutine UEL in Abaqus/Standard allows the creation of user-defined elements. Damage and failure for ductile metals Introduction Some user subroutines: • DLOAD for specifying user-defined loading • UVARM for defining a user output variable • URDFIL for reading the results file during analyses • SIGINI for specifying initial stress fields • USDFLD for defining field variable dependence Abaqus/Standard subroutines CREEP: Define time-dependent, viscoplastic behavior (creep and swelling). DFLOW: Define nonuniform pore fluid velocity in a _newlineConsolidation analysis. DFLUX: Define nonuniform distributed flux in a heat transfer or mass diffusion analysis. DISP: Specify prescribed boundary conditions. DLOAD: Specify nonuniform distributed loads. FILM: Define nonuniform film coefficient and associated sink temperatures for heat transfer analysis. FLOW: Define nonuniform seepage coefficient and associated sink pore pressure for consolidation analysis. FRIC: Define frictional behavior for contact surfaces. GAPCON: Define conductance between contact surfaces or nodes in a fully coupled temperature-displacement analysis or pure heat transfer analysis. GAPELECTR: Define electrical conductance between surfaces in a coupled thermal-electrical analysis. Abaqus/Standard subroutines HARDINI: Define initial equivalent plastic strain and initial backstress tensor. HETVAL: Provide internal heat generation in heat transfer analysis. MPC: Define multi-point constraints. ORIENT: Provide an orientation for defining local material directions or local directions for kinematic coupling constraints or local rigid body directions for inertia relief. RSURFU: Define a rigid surface. SDVINI: Define initial solution-dependent state variable fields. SIGINI: Define an initial stress field. UAMP: Specify amplitudes. UANISOHYPER_INV: Define anisotropic hyperelastic material behavior using the invariant formulation. UANISOHYPER_STRAIN: Define anisotropic hyperelastic material behavior based on Green strain. UCORR: Define cross-correlation properties for random response loading. UEL: Define an element. UEXPAN: Define incremental thermal strains. Abaqus/Standard subroutines UEXTERNALDB: Manage user-defined external databases and calculate model-independent history information. UFIELD: Specify predefined field variables. UFLUID: Define fluid density and fluid compliance for _newlineHydrostatic fluid elements. UFLUIDLEAKOFF: Define the fluid leak-off coefficients for pore pressure cohesive elements. UGENS: Define the mechanical behavior of a shell section. UHARD: Define the yield surface size and hardening parameters for isotropic plasticity or combined hardening models. UHYPEL: Define a hypoelastic stress-strain relation. UHYPER: Define a hyperelastic material. UINTER: Define surface interaction behavior for contact surfaces. UMASFL: Specify prescribed mass flow rate conditions for a convection/diffusion heat transfer analysis. UMAT: Define a material’s mechanical behavior. UMATHT: Define a material’s thermal behavior. Abaqus/Standard subroutines UMAT: Define a material’s mechanical behavior. UMATHT: Define a material’s thermal behavior. UMESHMOTION: Specify mesh motion constraints during adaptive meshing. UMOTION: Specify motions during cavity radiation heat transfer analysis or steady-state transport analysis. UMULLINS: Define damage variable for the Mullins effect material model. UPOREP: Define initial fluid pore pressure. UPRESS: Specify prescribed equivalent pressure stress conditions. UPSD: Define the frequency dependence for random response loading. URDFIL: Read the results file. USDFLD: Redefine field variables at a material point. UTEMP: Specify prescribed temperatures. UTRACLOAD: Specify nonuniform traction loads. UTRS: Define a reduced time shift function for a viscoelastic material. UVARM: Generate element output. UWAVE: Define wave kinematics for an analysis. VOIDRI: Define initial void ratios. Abaqus/Explicit subroutines VDISP: Specify prescribed boundary conditions. VDLOAD: Specify nonuniform distributed loads. VFABRIC: Define fabric material behavior. VFRIC: Define frictional behavior for contact surfaces. VUAMP: Specify amplitudes. VUANISOHYPER_INV: Define anisotropic hyperelastic material behavior using the invariant formulation. VUANISOHYPER_STRAIN: Define anisotropic hyperelastic material behavior based on Green strain. VUEL: Define an element. VUFIELD: Specify predefined field variables. VUHARD: Define the yield surface size and hardening parameters for isotropic plasticity or combined hardening models. VUINTER: Define the interaction between contact surfaces. VUMAT: Define material behavior. VUSDFLD: Redefine field variables at a material point. VUTRS: Define a reduced time shift function for a viscoelastic material. Subroutines in Abaqus • Before you run a job with user subroutine you will need to install C++ and Intel Fortran. Subroutines in Abaqus In the ABAQUS CAE environment take the following steps: • Create a part. • In the property module, create a material. Use DEPVAR to define number of solution dependent state variables and variable controlling element deletion. Also define values of material properties that will be interred in the subroutine.