Abstract

Very often computations on structural elements or machine components subjected to variable loading require using an advanced finite element model. This paper reports the numerical implementation of a model for multiaxial cyclic elasticplastic behaviour developed to extend the tools of the local deformation method under fatigue to multiaxial conditions. A basic computer code for axialtorsional loads was developed with the commercial software Matlab and a more sophisticated code based on the finite element model for general multiaxial loads was developed as a UMAT subroutine in Abaqus. Stress integration was introduced in the two usual forms: implicitly and explicitly. A comparison of the results obtained with the implicit and explicit formulations revealed that, under certain loading conditions, the outcome of the process depends on the particular integration scheme used.

Highlights

  • This paper reports the numerical implementation of a model for multiaxial cyclic elasticplastic behaviour developed to extend the tools of the local deformation method under fatigue to multiaxial conditions

  • A basic computer code for axialtorsional loads was developed with the commercial software Matlab and a more sophisticated code based on the finite element model for general multiaxial loads was developed as a UMAT subroutine in Abaqus

  • The cyclic plastic behaviour of some materials can be defined via so-called “cyclic stress-strain curves”, which are widely used in fatigue studies to introduce steady-state cyclic behaviour in computations of fatigue life at small numbers of cycles in the Local Strain Method [1,2,3]

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Summary

INTRODUCTION

The cyclic plastic behaviour of some materials can be defined via so-called “cyclic stress-strain curves”, which are widely used in fatigue studies to introduce steady-state cyclic behaviour in computations of fatigue life at small numbers of cycles in the Local Strain Method [1,2,3]. In previous work [4,5,6,7,8], we developed a plasticity model to simulate the behaviour of materials under multiaxial loads from cyclic stress-strain curves obtained in uniaxial loading tests with a view to extending the applicability of the Local Strain Method to multiaxial loading. This computational procedure for fatigue life is included in some commercial software packages. A more detailed description of the model can be found elsewhere [4,5,6,7,8]

MATRIX NOTATION
NUMERICAL IMPLEMENTATION
Explicit formulation
Implicit formulation
VALIDATION OF THE CODE
INFLUENCE OF THE INTEGRATION MODE

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