TY  - EJOU
AU  - Anding, D.K. 

TI  - Constitutive Equations in Finite Element Codes: The INTERATOM Model in ABAQUS
T2  - Structural Durability \& Health Monitoring

PY  - 2005
VL  - 1
IS  - 2
SN  - 1930-2991

AB  - The paper deals with the implementation of constitutive equations for isotropic viscoplastic material behaviour into modern Finite Element codes like ABAQUS. ABAQUS provides an user interface called UMAT (USER MATERIAL) for the definition of quite general material behaviour. The user can take advantage of the complete Finite Element code from ABAQUS and has to focus only on the solution of the constitutive equations. Key problems are accuracy and stability of this local solution procedure, which comes from the numerical stiffness of the governing equations (mostly first order ordinary differential equations). The numerical stiffness does not allow to use explicit integration methods for the governing equations (not even higher order methods); implicit integration methods have to be used instead. In this paper it is shown that in case of isotropic material behaviour the local solution procedure for the governing equations is reduced to the solution of a single (generally nonlinear) scalar equation which can be solved efficiently by means of Newtons method.
KW  - Constitutive Equations
KW  -  Viscoplasticity
KW  -  Finite Elements
KW  -  ABAQUS

DO  - 10.3970/sdhm.2005.001.095