Abstract
The purpose of the present contribution is to predict the fatigue life of welded joints by using the effective cyclic J-integral as crack driving force. The plasticity induced crack closure effects and the effects of welding residual stresses are taken into consideration. Here, the fatigue life is regarded as period of short fatigue crack growth. The node release technique is used to perform finite element based crack growth analyses. For fatigue lives calculations, the effective cyclic J-integral is employed in a relation similar to the Paris (crack growth) equation. For this purpose, a specific code was written for the determination of the effective cyclic J-integral for various lifetime relevant crack lengths. The effects of welding residual stresses on the crack driving force and the calculated fatigue lives are investigated. Results reveal that the influence of residual stresses can be neglected only for large load amplitudes. Finally, the predicted fatigue lives are compared with experimental data: a good accordance between both results is achieved.
Highlights
Welding is one of the most important joining methods in technology, for metallic structures
The results show that the R-ratio has almost no influence on the ΔJ-integral as long as crack closure effects are not considered
Fatigue crack growth simulations have been performed by taking into consideration plasticity induced crack closure effects as well as the effects of welding residual stresses
Summary
Welding is one of the most important joining methods in technology, for metallic structures. ΔJ is an extension of the monotonic J-integral introduced by Rice [10] This parameter has successfully been applied as an appropriate crack driving force for the description of fatigue crack growth, when the elastic-plastic material exhibits Masing’s behaviour [11,12]. Closure effects were considered by defining contact boundary conditions between crack faces and by using the effective cyclic J-integral (ΔJeff) as crack tip parameter for the description of the crack propagation rate. The advantage of this approach (fracture mechanics concept) is that, residual stresses can be treated explicitly. IBESS is divided into 8 subprojects and the authors were working on the subproject titled: “Modelling of fatigue crack growth in welded joints under consideration of the transient plastic deformation behaviour.”
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