Finite element based fatigue analysis of 6082 Aluminum alloy under random loading

Mechanical and structural components are subject in the most cases during their services to random loading. For this reason, it is necessary to reduce the complex history of these kinds of loading in a series of constant amplitude cycles. There are several counting methods that lead to different results. Among all these methods, it is recognized that the Rainflow Cycle Counting method provides the most conservative results. In this paper, a finite elements analysis technique is presented to predict the fatigue life using this method associate with the S-N method which is used for high cycle fatigue applications that makes no distinction between initiation or growing a crack, but rather, predicts the total life to failure. Comparison between numerical and experimental results is considering in this paper.

Finite element based fatigue analysis of 6082 Aluminum alloy under random loading

Mechanical and structural components are subject in the most cases during their services to random loading. For this reason, it is necessary to reduce the complex history of these kinds of loading in a series of constant amplitude cycles. There are several counting methods that lead to different results. Among all these methods, it is recognized that the Rainflow Cycle Counting method provides the most conservative results. In this paper, a finite elements analysis technique is presented to predict the fatigue life using this method associate with the S-N method which is used for high cycle fatigue applications that makes no distinction between initiation or growing a crack, but rather, predicts the total life to failure. Comparison between numerical and experimental results is considering in this paper.

Contribution à l'étude du cumul de dommage en fatigue multiaxiale

Ce travail constitue une contribution à l étude de l effet du cumul de dommage en fatigue multiaxiale polycyclique des matériaux métalliques (l alliage d aluminium 6082T6). Généralement, cet effet peut être interprété par différentes approches des lois de cumul d endommagement. En 2003, Mesmacque et Santos Garcia ont développé une nouvelle loi, damage stress model (DSM), en introduisant un nouvel indicateur non linéaire de dommage dans le cas de fatigue uniaxiale. Cet indicateur ne nécessite que la connaissance de la courbe de Wöhler et la résistance maximale du matériau. Le travail présenté ici constitue une extension du modèle DSM au cas de la fatigue multiaxiale. Cette extension est rendue possible par l utilisation de critères de fatigue multiaxiale de Sines, DangVan et Robert à durée de vie limitée et par la mise en œuvre d une méthode d itération programmée sous Matlab fournissant les indicateurs de dommage. Elle ne nécessite aucun paramètre supplémentaire mise à part la connaissance de la courbe de Wöhler uniaxiale. Les résultats des travaux expérimentaux en fatigue biaxiale, qui ont servi de support pour la validation de notre modèle ainsi que la comparaison avec le modèle de Miner, ont été obtenus grâce à la plateforme d essais multiaxiaux à quatre vérins à implantations modulaires. Une base de données expérimentale est disponible pour chargement biaxiale effectués sur des éprouvettes cruciformes amincies au centre. Par ailleurs, une simulation numérique sous Abaqus a permis d accéder au champ de déformation/contrainte au centre. Les résultats de cette simulation ont été corroborés à l aide d une éprouvette instrumentée par des jauges de déformation.This work is a contribution to the study of the effect of cumulative damage in multiaxial high cycle fatigue in metallic materials (the aluminum alloy 6082T6). Generally, this effect can be interpreted by different cumulative damage models. In 2003, Mesmacque and Santos Garcia have developed a new damage stress model (DSM), introducing a novel nonlinear damage indicator in the case of uniaxial fatigue. This indicator requires previous knowledge of the Wohler curve and the ultimate tensile strength of the material. The work presented here is an extension of the DSM model to the case of multiaxial fatigue. This extension is made possible with the assumption of multiaxial fatigue criteria: global type (Sines) and critical plane type (Dang Van and Robert) under finite life regime and the implementation of an iteration method in Matlab programming, which provides damage indicators. In particular, it requires no additional parameters besides the uniaxial Wöhler curve, which makes it easy to use. The results of experimental biaxial fatigue tests were obtained with the aid of the multiaxial test platform of our laboratory (four-cylinder modular-implementations platform) and an original test mode based on modal control , providing ground for the validation of our model and its comparison against other most current models. An experimental database is available for constant-level and block fatigue loadings using cruciform specimens thinned in the center. In addition, a numerical simulation in Abaqus allowed the analysis of the strain/stress field in the center of the specimen. The simulation results were corroborated using a specimen instrumented with strain gages.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Numerical investigation of mechanical behavior of cracked cruciform specimens in aluminum alloy 6082-T6 subjected to different biaxial loading conditions

Analysis of cracked cruciform specimens under biaxial loading conditions is very important and closer to reality in the study of behavior of marine, naval, aeronautical and railway structures. The aim of this work is to examine the evolution of fracture parameters in a combined mixed mode of an aluminum alloy A6082-T6 cruciform specimen as a function of the biaxial loading with different ratios. To this end, the effects of main parameters, such as load ratio, crack length, crack orientation and non-proportional loading coefficient have been analyzed and discussed in order to highlight fracture toughness of the studied material. The results show that the finite element method is a useful tool for calculation of crack characteristics in the mechanics of biaxial fracture. According to the obtained results, a non-proportional evolution of the fracture parameters, namely, the SIFs KI and KII , T-stress, and the biaxiality parameter was observed. Indeed, the latter depends considerably on the crack length, the angle of crack orientation and the applied biaxial loading. Detailed concluding remarks are presented at the end of this work

Relations statistiques d’estimation des caractéristiques de l’érosion de cavitation pour les aciers alliés

La prédiction de la résistance à l’érosion de cavitation des machines hydrauliques reste une préoccupation importante des concepteurs. Dans ce travail, nous proposons une fonction analytique représentative de l’érosion par cavitation. Cette fonction est obtenue par analyse statistique des résultats d’essais réalisés dans un appareil vibratoire magnétostrictif à tube de nickel. La fonction analytique proposée permet de décrire la variation du taux d’érosion v (mm3/s) en fonction du temps.Quatre aciers alliés sont utilisés pour l’étude: un acier à structure austénitique, un acier à structure mixte ferrite + perlite + bainite et deux aciers à structure mixte bainite + martensite. Les prévisions obtenues à partir du modèle analytique sont en accord avec les résultats expérimentaux. Ces prévisions permettent de classer les aciers en fonction de leur résistance à l’érosion

Finte element modeling of the behavior of polymethyl-methacrylate (PMMA) during high pressure torsion process.

High Pressure Torsion (HPT) is a highly effective super-plastic deformation process for obtaining nano-materials with high performance mechanical properties. In view of its optimization, it is of paramount importance to evaluate the relations between the behavior of the material under the effects of different processing parameters. In this context, this work aims to highlight the plastic strain distribution in the deformed material as a function of the hydrostatic pressure, the torsion angle and the temperature of the material applied during the process. A typical amorphous polymer (Polymethyl-Methacrylate: PMMA) has been tested. Firstly, in order to identify the material parameters of a phenomenological elasto-viscoplastic model compression tests at different temperatures and strain rates have been carried out. Then, the distributions of the effective plastic strain, the equivalent plastic strain rate and the hydrostatic stress were analyzed using finite elements method. Recommendations on process conditions were proclaimed at the end of this work according to the obtained numerical results

Fatigue Life Prediction and Damage Modelling of High-density Polyethylene under Constant and Two-block Loading ☆

International audienceAn experimental analysis for determining the fatigue strength of HDPE-100, under constant and variable amplitude loading is presented. Further, the cumulative fatigue damage behavior for HDPE-100 was experimentally investigated. First, The S–N curve was obtained to establish the fatigue life of The HDPE-100 subjected to constant stress amplitude. Secondly, the Cumulative fatigue damage was estimated by different cumulative model such as Miner rule, damage stress model and Energy model (Damage energy model). Comparison between predictions and experimental results showed different trends depending on the prediction model used

Finite element based fatigue analysis of 6082 Aluminum alloy under random loading

Mechanical and structural components are subject in the most cases during their services to random loading. For this reason, it is necessary to reduce the complex history of these kinds of loading in a series of constant amplitude cycles. There are several counting methods that lead to different results. Among all these methods, it is recognized that the Rainflow Cycle Counting method provides the most conservative results. In this paper, a finite elements analysis technique is presented to predict the fatigue life using this method associate with the S-N method which is used for high cycle fatigue applications that makes no distinction between initiation or growing a crack, but rather, predicts the total life to failure. Comparison between numerical and experimental results is considering in this paper

The Effect of corrosion on the quality repair of the aluminum alloy A 5083 H11 by bonded composites

In this paper, the effect of corrosion on the performance of the bonded composite patch repair in aluminum alloy A5083 marine structure was investigated using three dimensional finite element methods. To this end, two patches made in carbon/epoxy and boron/epoxy, bonded on corroded plates with and without crack, were tested under different applied loads. The effect of both corrosion and cracked materials on the damage of the adhesive FM73, was also highlighted. The obtained results show that, the corrosion has a significant effect on the quality repair performance. Indeed, it is proved that, the rate of damage increases with the increase of the applied load, and is more significant in the case of plates cracked and repaired by carbon/epoxy patch. Hence, the best performances were obtained using boron/epoxy patche