References of "Marmi, Abdeljalil"
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See detailAssessment of a multiscale fatigue damage model associated with stress gradient effects
Duchene, Laurent ULg; Marmi, Abdeljalil ULg; Habraken, Anne ULg

Poster (2014, September)

The aim of this research work is to develop a finite element numerical tool able to predict accurately the fatigue life of mechanical components. These components can have complex geometries, they can be ... [more ▼]

The aim of this research work is to develop a finite element numerical tool able to predict accurately the fatigue life of mechanical components. These components can have complex geometries, they can be submitted to a complex loading, leading to a specific stress field with possible stress concentration. Additionally, the successive cycles of loading are not necessarily identical. It is expected that the numerical tool can handle these demanding constraints. In this respect, a multiaxial fatigue damage model was implemented in our home-made finite element code Lagamine. The finite element method permits to account for the actual geometry of the mechanical part and the loading for the stress computation in the whole structure. The formulation of the multiaxial fatigue model is able to capture: - The non linear damage accumulation for multiblock and variable cyclic loading, - The effect of the mean (hydrostatic) stress, - The effect of the cycles below the fatigue limit if the damage was previously initiated. Finally, the occurrence of stress concentration will significantly reduce the life time of the studied piece. However, it is well-known that the subsequent local degradation of the material will be partly compensated by an enhanced load carrying contribution of the surrounding material, favourably leading to a reduction of the crack propagation. The stress gradients computed with different techniques are incorporated in the model so as to account for such beneficial influence. The physical roots of this model depart from the mesoscopic length scale, where the damage evolution is related to the mesoscopic accumulated plastic strain. Therefore, the variables of the model are defined at both macroscopic and mesoscopic scales and a specific scale transition method was implemented, based on the well-known simplified Zarka method but used at the multiscale level. The predictive capabilities of this multiscale multiaxial model are assessed by means of comparison with the classical Lemaitre-Chaboche model (implemented in the same FE code with stress gradient effects). For both models, the material parameters were identified from SN tests on smooth specimens of Ti-6Al-4V alloy, while the predictions of the models are validated thanks to comparison with experimental tests on notched samples, with stress gradient effects. [less ▲]

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See detailMultiaxial fatigue damage modeling of Ti6Al4V alloy
Marmi, Abdeljalil ULg; Habraken, Anne ULg; Duchene, Laurent ULg

in Proceedings of the ICMFF9 Conference (2010)

The aim of this study is to present a new multiaxial fatigue model based on phenomenological approach for the proportional loading. The model estimations are compared to the classical Lemaitre-Chaboche [1 ... [more ▼]

The aim of this study is to present a new multiaxial fatigue model based on phenomenological approach for the proportional loading. The model estimations are compared to the classical Lemaitre-Chaboche [1] fatigue model and experimental results. The comparison is done by simulation of SN curves of notched and un-notched forged TA6V samples. To take into account the effect of stress gradient near notch root, the applied loads such as stress amplitude and Von Mises stress are affected by the triaxialty function introduced by Lemaitre [2]. The models enhanced by triaxialty function give correct results for life estimation of notched samples. [less ▲]

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See detailMultiaxial fatigue damage modelling at Macro scale of Ti6AL4V alloy
Marmi, Abdeljalil ULg; Habraken, Anne ULg; Duchene, Laurent ULg

in International Journal of Fatigue (2009), 31

The Lemaitre and Chaboche fatigue model is investigated in order to predict the fatigue life of tensile samples with and without notches, defining different stress concentration fields. Elastoplastic FE ... [more ▼]

The Lemaitre and Chaboche fatigue model is investigated in order to predict the fatigue life of tensile samples with and without notches, defining different stress concentration fields. Elastoplastic FE simulations based on anisotropic yield locus description were carried out in order to obtain the stress and strain distributions near the notch root. The Lemaitre and Chaboche fatigue model was applied using the point method (local approach) and the gradient method (non-local approach). [less ▲]

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