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The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sun, 20 Sep 2020 14:33:03 GMT2020-09-20T14:33:03ZCompetition between microstructure and defect in multiaxial high cycle fatigue
http://hdl.handle.net/10985/10058
Competition between microstructure and defect in multiaxial high cycle fatigue
MOREL, Franck; GUERCHAIS, Raphaël; SAINTIER, Nicolas
This study aims at providing a better understanding of the effects of both microstructure and defect on the high cycle fatigue behavior of metallic alloys using finite element simulations of polycrystalline aggregates. It is well known that the microstructure strongly affects the average fatigue strength and when the cyclic stress level is close to the fatigue limit, it is often seen as the main source of the huge scatter generally observed in this fatigue regime. The presence of geometrical defects in a material can also strongly alter the fatigue behavior. Nonetheless, when the defect size is small enough, i.e. under a critical value, the fatigue strength is no more affected by the defect. The so-called Kitagawa effect can be interpreted as a competition between the crack initiation mechanisms governed either by the microstructure or by the defect. Surprisingly, only few studies have been done to date to explain the Kitagawa effect from the point of view of this competition, even though this effect has been extensively investigated in the literature. The primary focus of this paper is hence on the use of both FE simulations and explicit descriptions of the microstructure to get insight into how the competition between defect and microstructure operates in HCF. In order to account for the variability of the microstructure in the predictions of the macroscopic fatigue limits, several configurations of crystalline orientations, crystal aggregates and defects are studied. The results of each individual FE simulation are used to assess the response at the macroscopic scale thanks to a probabilistic fatigue criterion proposed by the authors in previous works. The ability of this criterion to predict the influence of defects on the average and the scatter of macroscopic fatigue limits is evaluated. In this paper, particular emphasis is also placed on the effect of different loading modes (pure tension, pure torsion and combined tension and torsion) on the experimental and predicted fatigue strength of a 316 stainless steel containing artificial defect.
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Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/100582015-01-01T00:00:00ZMOREL, FranckGUERCHAIS, RaphaëlSAINTIER, NicolasThis study aims at providing a better understanding of the effects of both microstructure and defect on the high cycle fatigue behavior of metallic alloys using finite element simulations of polycrystalline aggregates. It is well known that the microstructure strongly affects the average fatigue strength and when the cyclic stress level is close to the fatigue limit, it is often seen as the main source of the huge scatter generally observed in this fatigue regime. The presence of geometrical defects in a material can also strongly alter the fatigue behavior. Nonetheless, when the defect size is small enough, i.e. under a critical value, the fatigue strength is no more affected by the defect. The so-called Kitagawa effect can be interpreted as a competition between the crack initiation mechanisms governed either by the microstructure or by the defect. Surprisingly, only few studies have been done to date to explain the Kitagawa effect from the point of view of this competition, even though this effect has been extensively investigated in the literature. The primary focus of this paper is hence on the use of both FE simulations and explicit descriptions of the microstructure to get insight into how the competition between defect and microstructure operates in HCF. In order to account for the variability of the microstructure in the predictions of the macroscopic fatigue limits, several configurations of crystalline orientations, crystal aggregates and defects are studied. The results of each individual FE simulation are used to assess the response at the macroscopic scale thanks to a probabilistic fatigue criterion proposed by the authors in previous works. The ability of this criterion to predict the influence of defects on the average and the scatter of macroscopic fatigue limits is evaluated. In this paper, particular emphasis is also placed on the effect of different loading modes (pure tension, pure torsion and combined tension and torsion) on the experimental and predicted fatigue strength of a 316 stainless steel containing artificial defect.Non-local energy based fatigue life calculation method under multiaxial variable amplitude loadings
http://hdl.handle.net/10985/7414
Non-local energy based fatigue life calculation method under multiaxial variable amplitude loadings
SAINTIER, Nicolas; PALIN-LUC, Thierry; BÉNABÈS, Jérôme; COCHETEUX, Francis
Reliable design of industrial components against high cycle multiaxial fatigue requires a model capable of predicting both stress gradient and load type effects. Indeed, taking into account gradient effects is of prior importance for the applicability of fatigue models to real structures. In this paper, a fatigue life assessment method is proposed for proportional and non-proportional multiaxial variable amplitude loadings in the range 104 –107 cycles. This method derives from the fatigue criterion initially proposed by Palin-Luc and Lasserre (1998) [2] and revisited by Banvillet et al. (2003) [16] for multiaxial constant amplitude loading. The new proposal consists of a complete reformulation and extension of the previ- ously cited energy based fatigue strength criteria. It includes two major improvements of the existing criteria. The first one consists in a fatigue criterion for multiaxial variable amplitude loadings while only constant amplitude loadings were considered in the above cited works. The second one is an extension to an incremental fatigue life assessment method for proportional and non-proportional multiaxial variable amplitude loadings. No cycle counting technique is needed whatever the variable amplitude load- ings type considered (uniaxial or multiaxial). The predictions of the method for constant and variable amplitude multiaxial loadings are compared with experimental results on specimens from literature and from new experiments on a ferrito-perlitic steel. The above mentioned method has been implemented as a post-processor of a finite element software. An application to a railway wheel is finally presented.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/74142013-01-01T00:00:00ZSAINTIER, NicolasPALIN-LUC, ThierryBÉNABÈS, JérômeCOCHETEUX, FrancisReliable design of industrial components against high cycle multiaxial fatigue requires a model capable of predicting both stress gradient and load type effects. Indeed, taking into account gradient effects is of prior importance for the applicability of fatigue models to real structures. In this paper, a fatigue life assessment method is proposed for proportional and non-proportional multiaxial variable amplitude loadings in the range 104 –107 cycles. This method derives from the fatigue criterion initially proposed by Palin-Luc and Lasserre (1998) [2] and revisited by Banvillet et al. (2003) [16] for multiaxial constant amplitude loading. The new proposal consists of a complete reformulation and extension of the previ- ously cited energy based fatigue strength criteria. It includes two major improvements of the existing criteria. The first one consists in a fatigue criterion for multiaxial variable amplitude loadings while only constant amplitude loadings were considered in the above cited works. The second one is an extension to an incremental fatigue life assessment method for proportional and non-proportional multiaxial variable amplitude loadings. No cycle counting technique is needed whatever the variable amplitude load- ings type considered (uniaxial or multiaxial). The predictions of the method for constant and variable amplitude multiaxial loadings are compared with experimental results on specimens from literature and from new experiments on a ferrito-perlitic steel. The above mentioned method has been implemented as a post-processor of a finite element software. An application to a railway wheel is finally presented.About the effect of plastic dissipation in heat at the crack tip on the stress intensity factor under cyclic loading
http://hdl.handle.net/10985/6994
About the effect of plastic dissipation in heat at the crack tip on the stress intensity factor under cyclic loading
RANC, Nicolas; PALIN-LUC, Thierry; PARIS, Paul C.; SAINTIER, Nicolas
Because of the reverse cyclic plastic zone at the crack tip, there is plastic dissipation in heat at the crack tip under cyclic loading. That creates a heterogeneous temperature field around the crack tip. A thermo-mechanical model is proposed in this paper for evaluating the consequence of this temperature field on the Mode I stress intensity factor. Two cases are studied: (i) the theoretical problem of an infinite plate with a semi-infinite through crack under Mode I cyclic loading, and (ii) a finite specimen with a central through crack. In the first case, the main hypothesis and results are presented from the literature but no heat loss is taken into account. In second case, heat loss by convection is taken into account with a finite element analysis, while an analytical solution exists in the literature for the first case. In both cases, it is assumed that the heat source is located in the reverse cyclic plastic zone. The heat source within the reverse cyclic plastic zone is quantified by experiments on a mild steel under R=0.1. It is shown that the crack tip is under compression due to thermal stresses coming from the heterogeneous temperature field around the crack tip. The effect of this stress field on the stress intensity factor (its maximum, minimum and its range) is calculated. This paper shows that experiments have to be carried out to determine the heat source within the reverse cyclic plastic zone. This is the key parameter to quantify the effect of dissipation at the crack tip on the stress intensity factor.
Please cite this article as: Ranc, N., Palin-Luc, T., Paris, P.C., Saintier, N., About the effect of plastic dissipation in heat at the crack tip on the stress intensity factor under cyclic loading, International Journal of Fatigue (2013).
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/69942013-01-01T00:00:00ZRANC, NicolasPALIN-LUC, ThierryPARIS, Paul C.SAINTIER, NicolasBecause of the reverse cyclic plastic zone at the crack tip, there is plastic dissipation in heat at the crack tip under cyclic loading. That creates a heterogeneous temperature field around the crack tip. A thermo-mechanical model is proposed in this paper for evaluating the consequence of this temperature field on the Mode I stress intensity factor. Two cases are studied: (i) the theoretical problem of an infinite plate with a semi-infinite through crack under Mode I cyclic loading, and (ii) a finite specimen with a central through crack. In the first case, the main hypothesis and results are presented from the literature but no heat loss is taken into account. In second case, heat loss by convection is taken into account with a finite element analysis, while an analytical solution exists in the literature for the first case. In both cases, it is assumed that the heat source is located in the reverse cyclic plastic zone. The heat source within the reverse cyclic plastic zone is quantified by experiments on a mild steel under R=0.1. It is shown that the crack tip is under compression due to thermal stresses coming from the heterogeneous temperature field around the crack tip. The effect of this stress field on the stress intensity factor (its maximum, minimum and its range) is calculated. This paper shows that experiments have to be carried out to determine the heat source within the reverse cyclic plastic zone. This is the key parameter to quantify the effect of dissipation at the crack tip on the stress intensity factor.Effet de surface libre dans les agrégats polycristallins en fatigue à grand nombre de cycles.
http://hdl.handle.net/10985/7383
Effet de surface libre dans les agrégats polycristallins en fatigue à grand nombre de cycles.
ROBERT, Camille; HOR, Anis; MOREL, Franck; SAINTIER, Nicolas; PALIN-LUC, Thierry
An analysis of high cycle fatigue behavior is done via the numerical simulation of polycrystalline aggregates. Different metallic materials with a FCC crystalline structure, but different cubic elastic coefficients, are investigated. Several statistical elementary volumes (SEV), consisting of 300 grains with isotropic texture and equiaxed geometries, are loaded at the median macroscopic fatigue limit for 107 cycles. Three different models are studied: 2D generalized plane strain, 3D periodic and 3D periodic with a free surface. Different mesoscopic variables are analyzed using extreme value statistics. The results show a detrimental e ect on the fatigue strength of the modeled aggregates with a free surface, if the crystalline elastic anisotropy is sufficient.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/73832013-01-01T00:00:00ZROBERT, CamilleHOR, AnisMOREL, FranckSAINTIER, NicolasPALIN-LUC, ThierryAn analysis of high cycle fatigue behavior is done via the numerical simulation of polycrystalline aggregates. Different metallic materials with a FCC crystalline structure, but different cubic elastic coefficients, are investigated. Several statistical elementary volumes (SEV), consisting of 300 grains with isotropic texture and equiaxed geometries, are loaded at the median macroscopic fatigue limit for 107 cycles. Three different models are studied: 2D generalized plane strain, 3D periodic and 3D periodic with a free surface. Different mesoscopic variables are analyzed using extreme value statistics. The results show a detrimental e ect on the fatigue strength of the modeled aggregates with a free surface, if the crystalline elastic anisotropy is sufficient.Simulation of the Kitagawa-Takahashi diagram using a probabilistic approach for cast Al-Si alloys under different multiaxial loads
http://hdl.handle.net/10985/11184
Simulation of the Kitagawa-Takahashi diagram using a probabilistic approach for cast Al-Si alloys under different multiaxial loads
LE, Viet Duc; MOREL, Franck; BELLETT, Daniel; SAINTIER, Nicolas; OSMOND, Pierre
This article describes a microstructural-based high cycle fatigue strength modelling approach applied to different cast Al-Si alloys used in an automotive context. Thank to different casting processes (gravity die casting and lost foam casting), associated with several heat treatment (T7 and Hot Isostatic Pressing-HIP), three alloys with very different microstructures have been obtained. In a vast experimental campaign undertaken to investigate the fatigue damage mechanisms governing these alloys under different multiaxial loading conditions, it was shown that the principal crack initiation mechanisms for the porosity-free alloy are either the formation of persistent slip bands (PSB) or the rupture and/or debonding of eutectic particles. For the porosity-containing alloys, the fatigue damage is always controlled by crack growth from pores. In order to take into account these fatigue damage mechanisms, a probabilistic model using a combination of the Dang Van and a modified LEFM criteria is proposed. The modified LEFM criterion is able to take into account the influence of the grain size on the threshold of the stress intensity factor. It is shown that for the porosity-free alloy, the predictions are good for combined tension-torsion loads with R = - 1. However, because the crack initiation mechanisms are not the same depending on the hydrostatic stress, the predictions are non-conservative for the uniaxial and equibiaxial tension oads with R = 0,1. For the porosity-containing alloys, the predictions are very good for the uniaxial, combined tension-torsion and equibiaxial tension loads with both R = - 1and R = 0,1. As observed experimentally, the proposed model can also predict a more pronounced effect of casting porosity for the uniaxial and combined tension-torsion loads, when compared to pure torsion loads.
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/10985/111842016-01-01T00:00:00ZLE, Viet DucMOREL, FranckBELLETT, DanielSAINTIER, NicolasOSMOND, PierreThis article describes a microstructural-based high cycle fatigue strength modelling approach applied to different cast Al-Si alloys used in an automotive context. Thank to different casting processes (gravity die casting and lost foam casting), associated with several heat treatment (T7 and Hot Isostatic Pressing-HIP), three alloys with very different microstructures have been obtained. In a vast experimental campaign undertaken to investigate the fatigue damage mechanisms governing these alloys under different multiaxial loading conditions, it was shown that the principal crack initiation mechanisms for the porosity-free alloy are either the formation of persistent slip bands (PSB) or the rupture and/or debonding of eutectic particles. For the porosity-containing alloys, the fatigue damage is always controlled by crack growth from pores. In order to take into account these fatigue damage mechanisms, a probabilistic model using a combination of the Dang Van and a modified LEFM criteria is proposed. The modified LEFM criterion is able to take into account the influence of the grain size on the threshold of the stress intensity factor. It is shown that for the porosity-free alloy, the predictions are good for combined tension-torsion loads with R = - 1. However, because the crack initiation mechanisms are not the same depending on the hydrostatic stress, the predictions are non-conservative for the uniaxial and equibiaxial tension oads with R = 0,1. For the porosity-containing alloys, the predictions are very good for the uniaxial, combined tension-torsion and equibiaxial tension loads with both R = - 1and R = 0,1. As observed experimentally, the proposed model can also predict a more pronounced effect of casting porosity for the uniaxial and combined tension-torsion loads, when compared to pure torsion loads.Modelling of corrosion fatigue crack initiation on martensitic stainless steel in high cycle fatigue regime
http://hdl.handle.net/10985/13235
Modelling of corrosion fatigue crack initiation on martensitic stainless steel in high cycle fatigue regime
EL MAY, Mohamed; SAINTIER, Nicolas; PALIN-LUC, Thierry; DEVOS, Olivier; BRUCELLE, Olivier
This paper presents an analytical model for assessing the corrosion fatigue crack initiation life on a martensitic stainless steel X12CrNiMoV12-3 in high cycle fatigue regime (between 105 and 107 cycles). Based on in-situ electrochemical measurements during corrosion fatigue tests in NaCl aqueous solution, the corrosion fatigue crack initiation mechanism was identified. Two main stages were investigated: (i) the fracture of the passive film by slip bands and (ii) the free dissolution of the metal developing fatigue crack initiation from a critical corrosion defect. The depassivation stress threshold corresponds to the median fatigue strength at 107 cycles for fatigue corrosion tests. For an applied stress range less than this threshold, the depassivation phenomenon was not observed at 107 cycles and no crack initiation occurred. The proposed model takes into account the depassivation process induced by the slip bands emergence at the specimen surface and the corrosion rate under cyclic loading. The experimental results are compared to the proposed model taking into account mechanical and electrochemical material parameters.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/10985/132352018-01-01T00:00:00ZEL MAY, MohamedSAINTIER, NicolasPALIN-LUC, ThierryDEVOS, OlivierBRUCELLE, OlivierThis paper presents an analytical model for assessing the corrosion fatigue crack initiation life on a martensitic stainless steel X12CrNiMoV12-3 in high cycle fatigue regime (between 105 and 107 cycles). Based on in-situ electrochemical measurements during corrosion fatigue tests in NaCl aqueous solution, the corrosion fatigue crack initiation mechanism was identified. Two main stages were investigated: (i) the fracture of the passive film by slip bands and (ii) the free dissolution of the metal developing fatigue crack initiation from a critical corrosion defect. The depassivation stress threshold corresponds to the median fatigue strength at 107 cycles for fatigue corrosion tests. For an applied stress range less than this threshold, the depassivation phenomenon was not observed at 107 cycles and no crack initiation occurred. The proposed model takes into account the depassivation process induced by the slip bands emergence at the specimen surface and the corrosion rate under cyclic loading. The experimental results are compared to the proposed model taking into account mechanical and electrochemical material parameters.Non-local high cycle fatigue strength criterion for metallic materials with corrosion defects
http://hdl.handle.net/10985/10018
Non-local high cycle fatigue strength criterion for metallic materials with corrosion defects
EL MAY, Mohamed; SAINTIER, Nicolas; PALIN-LUC, Thierry; DEVOS, Olivier
This paper proposes a volumetric high cycle fatigue (HCF) strength criterion able to quantify the influence of natural corrosion pits on the fatigue limit of a martensitic stainless steel with high mechanical strength. Elastic–plastic numerical simulations were performed for real pits geometry, identified by X-ray microtomography, to determine the local stress distribution. The analysis revealed that calculation of the fatigue strength for material with real (irregular) pit geometry required a non-local HCF strength criterion. Such model was proposed based on the Crossland equivalent stress averaged within a volume limited by a critical distance. This criterion was validated with HCF tests on specimens with natural corrosion defects of different sizes.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/100182015-01-01T00:00:00ZEL MAY, MohamedSAINTIER, NicolasPALIN-LUC, ThierryDEVOS, OlivierThis paper proposes a volumetric high cycle fatigue (HCF) strength criterion able to quantify the influence of natural corrosion pits on the fatigue limit of a martensitic stainless steel with high mechanical strength. Elastic–plastic numerical simulations were performed for real pits geometry, identified by X-ray microtomography, to determine the local stress distribution. The analysis revealed that calculation of the fatigue strength for material with real (irregular) pit geometry required a non-local HCF strength criterion. Such model was proposed based on the Crossland equivalent stress averaged within a volume limited by a critical distance. This criterion was validated with HCF tests on specimens with natural corrosion defects of different sizes.Mechanical behavior of periodical microstructure induced by friction stir welding on Al–Cu–Li 2050 alloy
http://hdl.handle.net/10985/10494
Mechanical behavior of periodical microstructure induced by friction stir welding on Al–Cu–Li 2050 alloy
DHONDT, Matthieu; AUBERT, Isabelle; SAINTIER, Nicolas; OLIVE, Jean-Marc
Mechanical behavior analysis of the friction stir weld nugget of an aluminum alloy 2050 reveals a major role of the microstructure which varies with the distance to the weld surface. Three types of microstructure heterogeneities are considered namely grain size, precipitation state and textured bands. The grain size and the T1 precipitates density decrease with the distance from the weld surface. The density of T1 precipitates has a first order effect on micro-hardness variations and makes the Hall–Petch rule not valid in this case. Tensile tests combined with strain field identification done by digital image correlation measurements demonstrate the good correlation between textured bands and strain field heterogeneities. Crystal plasticity simulations by finite element method well account for the macroscopic mechanical behavior as well as strain field in textured bands.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/104942015-01-01T00:00:00ZDHONDT, MatthieuAUBERT, IsabelleSAINTIER, NicolasOLIVE, Jean-MarcMechanical behavior analysis of the friction stir weld nugget of an aluminum alloy 2050 reveals a major role of the microstructure which varies with the distance to the weld surface. Three types of microstructure heterogeneities are considered namely grain size, precipitation state and textured bands. The grain size and the T1 precipitates density decrease with the distance from the weld surface. The density of T1 precipitates has a first order effect on micro-hardness variations and makes the Hall–Petch rule not valid in this case. Tensile tests combined with strain field identification done by digital image correlation measurements demonstrate the good correlation between textured bands and strain field heterogeneities. Crystal plasticity simulations by finite element method well account for the macroscopic mechanical behavior as well as strain field in textured bands.Creep-fatigue interactions in pure Tantalum under constant and variable amplitude
http://hdl.handle.net/10985/9596
Creep-fatigue interactions in pure Tantalum under constant and variable amplitude
MARÉCHAL, David; SAINTIER, Nicolas; PALIN-LUC, Thierry; NADAL, François
Due to its specific mechanical properties, tantalum is often used in strength-demanding military applications. High cycle fatigue (HCF) behaviour of pure tantalum, however, has been rarely reported and the mechanisms at stake to account for deformation under cyclic loadings are still badly understood [1-2]. This presentation aims at better understanding the HCF damage mechanisms encountered in pure tantalum under such loadings. HCF loadings at various frequencies were performed in tension at room temperature on commercially-pure tantalum. Mean stress effects and frequency effects were investigated in the aim of clarifying the interaction between fatigue and creep. For symmetrical loadings (R=-1, i.e. under zero mean stress), fracture mechanisms were observed to vary from intergranular to transgranular when the maximum stress was decreased. For non-symmetrical loadings (R>0, with sufficiently large mean stress), a transition was also observed from extensive necking to intergranular initiation. Important creep activation was deduced from the presence of necking. This prevalence of creep at room temperature was actually confirmed by two other phenomena: a) The large influence of the frequency on fatigue life, indicating time-dependent damage. b) Important creep deformation during room-temperature creep tests. Finally, complex sequential loadings, representative of in-service loadings, were applied to pure tantalum specimens. The contribution of each loading sequence to the overall damage was quantified. It was shown that linear cumulative damage rules (analogous to Miner’s law to account for fatigue damage and for creep damage) failed to predict life duration of pure tantalum. The ONERA model [3-4], which specifically accounts for creep-fatigue interactions, granted better results. However, it is important to notice that this model uses engineering stresses as input, assuming that the specimen cross-section does not evolve drastically during fatigue/creep deformation. Such hypothesis needs to be revisited as the true stress seems a more realistic input to account for creep damage.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/95962015-01-01T00:00:00ZMARÉCHAL, DavidSAINTIER, NicolasPALIN-LUC, ThierryNADAL, FrançoisDue to its specific mechanical properties, tantalum is often used in strength-demanding military applications. High cycle fatigue (HCF) behaviour of pure tantalum, however, has been rarely reported and the mechanisms at stake to account for deformation under cyclic loadings are still badly understood [1-2]. This presentation aims at better understanding the HCF damage mechanisms encountered in pure tantalum under such loadings. HCF loadings at various frequencies were performed in tension at room temperature on commercially-pure tantalum. Mean stress effects and frequency effects were investigated in the aim of clarifying the interaction between fatigue and creep. For symmetrical loadings (R=-1, i.e. under zero mean stress), fracture mechanisms were observed to vary from intergranular to transgranular when the maximum stress was decreased. For non-symmetrical loadings (R>0, with sufficiently large mean stress), a transition was also observed from extensive necking to intergranular initiation. Important creep activation was deduced from the presence of necking. This prevalence of creep at room temperature was actually confirmed by two other phenomena: a) The large influence of the frequency on fatigue life, indicating time-dependent damage. b) Important creep deformation during room-temperature creep tests. Finally, complex sequential loadings, representative of in-service loadings, were applied to pure tantalum specimens. The contribution of each loading sequence to the overall damage was quantified. It was shown that linear cumulative damage rules (analogous to Miner’s law to account for fatigue damage and for creep damage) failed to predict life duration of pure tantalum. The ONERA model [3-4], which specifically accounts for creep-fatigue interactions, granted better results. However, it is important to notice that this model uses engineering stresses as input, assuming that the specimen cross-section does not evolve drastically during fatigue/creep deformation. Such hypothesis needs to be revisited as the true stress seems a more realistic input to account for creep damage.Microstructure-dependent predictions of the effect of defect size and shape on the high-cycle fatigue strength
http://hdl.handle.net/10985/10764
Microstructure-dependent predictions of the effect of defect size and shape on the high-cycle fatigue strength
GUERCHAIS, Raphaël; MOREL, Franck; SAINTIER, Nicolas
This study aims to investigate the effects of both the microstructure and void on the high-cycle fatigue behavior of metallic materials. To deal with this matter, finite element analyses of polycrystalline aggregates are carried out, for different configurations of crystalline orientations, in order to estimate the mechanical state, at the grain scale, in the vicinity of a small elliptical hole. Fatigue criteria are then applied to predict the average fatigue limit in fully reversed tension, for different defect sizes and ellipse aspect ratios. The constitutive models and the fatigue criteria are calibrated using experimental data obtained from specimens made of 316L austenitic steel . The predictions are then confronted to experimental trends .
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/10985/107642016-01-01T00:00:00ZGUERCHAIS, RaphaëlMOREL, FranckSAINTIER, NicolasThis study aims to investigate the effects of both the microstructure and void on the high-cycle fatigue behavior of metallic materials. To deal with this matter, finite element analyses of polycrystalline aggregates are carried out, for different configurations of crystalline orientations, in order to estimate the mechanical state, at the grain scale, in the vicinity of a small elliptical hole. Fatigue criteria are then applied to predict the average fatigue limit in fully reversed tension, for different defect sizes and ellipse aspect ratios. The constitutive models and the fatigue criteria are calibrated using experimental data obtained from specimens made of 316L austenitic steel . The predictions are then confronted to experimental trends .