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http://hdl.handle.net/10985/8395
MODELLING OF STRESS GRADIENT EFFECT ON FATIGUE LIFE USING WEIBULL BASED DISTRIBUTION FUNCTION
KAROLCZUK, Aleksander; PALIN-LUC, Thierry
In the present paper, a new approach is developed in order to take into account the stress gradient effect on fatigue life of structural components. The proposed approach is based on the weakest link concept in which the shape coefficient of the Weibull distribution becomes a function of a local damage parameter. The function simulates the experimentally observed relationship between the shape of the fatigue life distribution and the stress level. Such an approach allows one to calculate the global probability distribution of the fatigue life for notched structural components in a wide range of fatigue life regime: 104-107 cycles typically. For comparison purposes, the approach is applied to calculate the number of cycles to crack initiation of structural elements under three probability levels: 5%, 63% and 95%. The calculated lifetimes are compared with the lifetimes obtained from experiments performed on notched cruciform specimens and notched round specimens subjected to constant amplitude loading.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/83952013-01-01T00:00:00ZKAROLCZUK, AleksanderPALIN-LUC, ThierryIn the present paper, a new approach is developed in order to take into account the stress gradient effect on fatigue life of structural components. The proposed approach is based on the weakest link concept in which the shape coefficient of the Weibull distribution becomes a function of a local damage parameter. The function simulates the experimentally observed relationship between the shape of the fatigue life distribution and the stress level. Such an approach allows one to calculate the global probability distribution of the fatigue life for notched structural components in a wide range of fatigue life regime: 104-107 cycles typically. For comparison purposes, the approach is applied to calculate the number of cycles to crack initiation of structural elements under three probability levels: 5%, 63% and 95%. The calculated lifetimes are compared with the lifetimes obtained from experiments performed on notched cruciform specimens and notched round specimens subjected to constant amplitude loading.Overload effects on a ferritic-baintic steel and a cast aluminium alloy: two very different behaviours
http://hdl.handle.net/10985/8814
Overload effects on a ferritic-baintic steel and a cast aluminium alloy: two very different behaviours
SAINTIER, Nicolas; PALIN-LUC, Thierry; EL DSOKI, Chalid; BIDOUARD, Hadrien; KAUFMANN, Heinz; DUMAS, C.; VÖLLMECKE, F.J.; SONSINO, Cetin Morris
Load controlled fatigue tests were performed up to 107 cycles on flat notched specimens (Kt =2.5) under constant amplitude and variable amplitude loadings with and without periodical overloads. Two materials are studied: a ferritic-bainitic steel and a cast aluminium alloy. These materials have a very different cyclic behaviour: the steel exhibits cyclic strain oftening whereas the Al alloy shows cyclic strain hardening. The fatigue tests show that, for the steel, periodical overload applications reduce significantly the fatigue life for fully reversed load ratio (Rr = – 1), while they have no influence under pulsating loading (Rr = 0). For the Al alloy over-loads have an effect (fatigue life decreasing) only for variable amplitude loadings. The detrimental effect of overloads on the steel is due to ratcheting at the notch root which evolution is overload's dependent.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/10985/88142011-01-01T00:00:00ZSAINTIER, NicolasPALIN-LUC, ThierryEL DSOKI, ChalidBIDOUARD, HadrienKAUFMANN, HeinzDUMAS, C.VÖLLMECKE, F.J.SONSINO, Cetin MorrisLoad controlled fatigue tests were performed up to 107 cycles on flat notched specimens (Kt =2.5) under constant amplitude and variable amplitude loadings with and without periodical overloads. Two materials are studied: a ferritic-bainitic steel and a cast aluminium alloy. These materials have a very different cyclic behaviour: the steel exhibits cyclic strain oftening whereas the Al alloy shows cyclic strain hardening. The fatigue tests show that, for the steel, periodical overload applications reduce significantly the fatigue life for fully reversed load ratio (Rr = – 1), while they have no influence under pulsating loading (Rr = 0). For the Al alloy over-loads have an effect (fatigue life decreasing) only for variable amplitude loadings. The detrimental effect of overloads on the steel is due to ratcheting at the notch root which evolution is overload's dependent.The behavior of statically-indeterminate structural members and frames with cracks present
http://hdl.handle.net/10985/8817
The behavior of statically-indeterminate structural members and frames with cracks present
PARIS, Paul C.; PALIN-LUC, Thierry
Crack stability is discussed as affected by their presence in statically-indeterminate beams, frames, rings, etc. loaded into the plastic range. The stability of a crack in a section, which has become plastic, is analyzed with the remainder of the structure elastic and with subsequent additional plastic hinges occurring. The reduction of energy absorption characteristics for large deformations is also discussed. The methods of elastic–plastic tearing instability are incorporated to show that in many cases the fully plastic collapse mechanism must occur for complete failure.
Arts et Métiers ParisTech, invitation en tant que professeur invité de Paul C. Paris au LAMEFIP
Thu, 01 Jan 2009 00:00:00 GMThttp://hdl.handle.net/10985/88172009-01-01T00:00:00ZPARIS, Paul C.PALIN-LUC, ThierryCrack stability is discussed as affected by their presence in statically-indeterminate beams, frames, rings, etc. loaded into the plastic range. The stability of a crack in a section, which has become plastic, is analyzed with the remainder of the structure elastic and with subsequent additional plastic hinges occurring. The reduction of energy absorption characteristics for large deformations is also discussed. The methods of elastic–plastic tearing instability are incorporated to show that in many cases the fully plastic collapse mechanism must occur for complete failure.Simulation of multiaxial fatigue strength of steel component treated by surface induction hardening and comparison with experimental results
http://hdl.handle.net/10985/10521
Simulation of multiaxial fatigue strength of steel component treated by surface induction hardening and comparison with experimental results
PALIN-LUC, Thierry; COUPARD, Dominique; DUMAS, Christian; BRISTIEL, Philippe
This paper proposes a method to assess the high-cycle multiaxial fatigue strength of components treated by surface induction hardening (SIH). Surface quenching following surface induction heating is simulated, taking into account the following features of the process: (i) electromagnetic and thermal fields, (ii) phase transformation, and (iii) the residual stress field resulting from the entire process. The fatigue strength of the specimens was simulated using Crossland and Dang-Van criteria; the field of the residual stresses and the fatigue characteristics of both the untreated material and the treated layer (martensite) are considered. Fatigue tests on smooth specimens were carried out to compare simulated results with experimental data. These tests yield information regarding the influence of the thermal treatment on material behaviour and strength, including microstructure evolution and mechanical characteristics, especially in fatigue. For this purpose, residual stresses were analyzed by X-ray diffraction before and after the fatigue tests. Fatigue crack initiation areas (at the specimen’s surface or below) are predicted depending on the depth of the hardened material layer. The simulation of the fatigue strength at 2E6 cycles is in good agreement with experimental results.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/10985/105212011-01-01T00:00:00ZPALIN-LUC, ThierryCOUPARD, DominiqueDUMAS, ChristianBRISTIEL, PhilippeThis paper proposes a method to assess the high-cycle multiaxial fatigue strength of components treated by surface induction hardening (SIH). Surface quenching following surface induction heating is simulated, taking into account the following features of the process: (i) electromagnetic and thermal fields, (ii) phase transformation, and (iii) the residual stress field resulting from the entire process. The fatigue strength of the specimens was simulated using Crossland and Dang-Van criteria; the field of the residual stresses and the fatigue characteristics of both the untreated material and the treated layer (martensite) are considered. Fatigue tests on smooth specimens were carried out to compare simulated results with experimental data. These tests yield information regarding the influence of the thermal treatment on material behaviour and strength, including microstructure evolution and mechanical characteristics, especially in fatigue. For this purpose, residual stresses were analyzed by X-ray diffraction before and after the fatigue tests. Fatigue crack initiation areas (at the specimen’s surface or below) are predicted depending on the depth of the hardened material layer. The simulation of the fatigue strength at 2E6 cycles is in good agreement with experimental results.Scaling invariance of fatigue crack growth in gigacycle loading regime
http://hdl.handle.net/10985/10516
Scaling invariance of fatigue crack growth in gigacycle loading regime
OBORIN, V.; BANNIKOV, M.V.; NAIMARK, O.B; PALIN-LUC, Thierry
The role of the collective behavior of defect ensembles at the crack tip and the laws of fatigue crack propagation in R4 high-strength steel have been studied under conditions of symmetric tension-compression gigacycle loading at 20 kHz. At every stage of the fatigue crack growth, replicas from the sample side surface were taken and studied by the method of three-dimensional relief profilometry (using NewView interferometer profilometer) so as to study the scaling-invariant laws of defect-related structure evolution.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10985/105162010-01-01T00:00:00ZOBORIN, V.BANNIKOV, M.V.NAIMARK, O.BPALIN-LUC, ThierryThe role of the collective behavior of defect ensembles at the crack tip and the laws of fatigue crack propagation in R4 high-strength steel have been studied under conditions of symmetric tension-compression gigacycle loading at 20 kHz. At every stage of the fatigue crack growth, replicas from the sample side surface were taken and studied by the method of three-dimensional relief profilometry (using NewView interferometer profilometer) so as to study the scaling-invariant laws of defect-related structure evolution.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.A volumetric energy based high cycle multiaxial fatigue citerion
http://hdl.handle.net/10985/11218
A volumetric energy based high cycle multiaxial fatigue citerion
BANVILLET, ALexis; PALIN-LUC, Thierry; LASSERRE, Serge
A reliable design of industrial parts against high-cycle multiaxial fatigue requires a fatigue criterion capable of predicting both the stress gradient and the load-type effects. These effects are very important in the transfer of fatigue data from specimen to component. By using the concept of volume influencing fatigue crack initiation proposed by Palin-Luc and Lasserre with an energy based approach, a new criterion is presented. Based on the strain-work density given to the material, this proposal is usable whatever the constant amplitude loading is: in and out-of-phase combined loadings, with or without mean stress. Its predictions are compared both with a total of 38 experiments on four materials (a mild steel, two high strength steels and a spheroidal graphite cast iron) and with the predictions of local criteria (Crossland, Dang Van, Papadopoulos and Morel). The comparison shows that the predictions of the volumetric proposal are very good and less scattered than those of the local approaches, especially for loadings with mean stresses or under non-proportional loadings.
Wed, 01 Jan 2003 00:00:00 GMThttp://hdl.handle.net/10985/112182003-01-01T00:00:00ZBANVILLET, ALexisPALIN-LUC, ThierryLASSERRE, SergeA reliable design of industrial parts against high-cycle multiaxial fatigue requires a fatigue criterion capable of predicting both the stress gradient and the load-type effects. These effects are very important in the transfer of fatigue data from specimen to component. By using the concept of volume influencing fatigue crack initiation proposed by Palin-Luc and Lasserre with an energy based approach, a new criterion is presented. Based on the strain-work density given to the material, this proposal is usable whatever the constant amplitude loading is: in and out-of-phase combined loadings, with or without mean stress. Its predictions are compared both with a total of 38 experiments on four materials (a mild steel, two high strength steels and a spheroidal graphite cast iron) and with the predictions of local criteria (Crossland, Dang Van, Papadopoulos and Morel). The comparison shows that the predictions of the volumetric proposal are very good and less scattered than those of the local approaches, especially for loadings with mean stresses or under non-proportional loadings.How to reduce the duration of multiaxial fatigue tests under proportional service loadings
http://hdl.handle.net/10985/11226
How to reduce the duration of multiaxial fatigue tests under proportional service loadings
PALIN-LUC, Thierry; BANVILLET, Alexis; VITTORI, Jean-François
This paper deals with a technique to transform a multiaxial stress and strain-time sequence (in service recorded) in a simplified sequence. This simplified sequence is shorter than the original one and equivalent in terms of damage and lifetime: the number of simplified sequences to crack initiation is equal to the number of original sequences. The proposal is based on an energy threshold, below which no micro-crack can initiate or grow in the material. This technique was validated with real loading sequences recorded by strain gauges pasted on a car suspension arm. Fatigue tests were carried out on smooth specimens made of spheroidal graphite cast iron loaded in bending, in torsion and in combined bending and torsion. Experimental fatigue lives under the original sequence and under the simplified one are in very good correlation. Fatigue test duration is reduced up to a factor of 10 for the severe stress–strain sequences tested in this study.
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/10985/112262006-01-01T00:00:00ZPALIN-LUC, ThierryBANVILLET, AlexisVITTORI, Jean-FrançoisThis paper deals with a technique to transform a multiaxial stress and strain-time sequence (in service recorded) in a simplified sequence. This simplified sequence is shorter than the original one and equivalent in terms of damage and lifetime: the number of simplified sequences to crack initiation is equal to the number of original sequences. The proposal is based on an energy threshold, below which no micro-crack can initiate or grow in the material. This technique was validated with real loading sequences recorded by strain gauges pasted on a car suspension arm. Fatigue tests were carried out on smooth specimens made of spheroidal graphite cast iron loaded in bending, in torsion and in combined bending and torsion. Experimental fatigue lives under the original sequence and under the simplified one are in very good correlation. Fatigue test duration is reduced up to a factor of 10 for the severe stress–strain sequences tested in this study.Elastomer and resin replicas for sem observation of metallic materials
http://hdl.handle.net/10985/11219
Elastomer and resin replicas for sem observation of metallic materials
PALIN-LUC, Thierry; SELLIER, E.; D'ERRICO, F.; VANHAEREN, M.
The replica technique is often used to study damage evolution at the surface of specimens or industrial components and understand the physicial phenomena responsible for fatigue crack initiation before failure. Replicas are usually made from acetate cellulose film. This paper presents an alternative technique generally used by archaeologists to study lithic use-wear and bone modification. A mold is made from a dental elastomer (silicon based impression material) and a positive replica is made by casting epoxy resin in the mold. Comparative SEM analysis of damaged metallic specimens and their resin replicas show that this technique provides a good resolution and preserves details up to 0.5 micrometer. This easy and low cost method allows a systematic study of micro-crack growth.
Tue, 01 Jan 2002 00:00:00 GMThttp://hdl.handle.net/10985/112192002-01-01T00:00:00ZPALIN-LUC, ThierrySELLIER, E.D'ERRICO, F.VANHAEREN, M.The replica technique is often used to study damage evolution at the surface of specimens or industrial components and understand the physicial phenomena responsible for fatigue crack initiation before failure. Replicas are usually made from acetate cellulose film. This paper presents an alternative technique generally used by archaeologists to study lithic use-wear and bone modification. A mold is made from a dental elastomer (silicon based impression material) and a positive replica is made by casting epoxy resin in the mold. Comparative SEM analysis of damaged metallic specimens and their resin replicas show that this technique provides a good resolution and preserves details up to 0.5 micrometer. This easy and low cost method allows a systematic study of micro-crack growth.Comparative study and link between mesoscopic and energetic approaches in high cycle multiaxial fatigue
http://hdl.handle.net/10985/11221
Comparative study and link between mesoscopic and energetic approaches in high cycle multiaxial fatigue
MOREL, Franck; PALIN-LUC, Thierry; FROUSTEY, Catherine
Multiaxial fatigue analysis can be categorized into several viewpoints, i.e. empirical formulae, methods based on stress invariants, critical plane approaches, models using averages of stress quantities and energetic considerations. The aim of this paper is not to survey the current state of knowledge concerning multiaxial fatigue but to critically examine two endurance criteria so as to prove that a direct link can be established between them. The first of the two methods, proposed by Papadopoulos, has been built by exploring the fatigue of metals from the mesoscopic scale, that is from the scale of the metal grains of a metallic aggregate. The localized plastic strains developping in some less favourably oriented crystals is considered to be the main cause of fatigue crack nucleation. According to relationships between macroscopic and mesoscopic quantities, this model is finally expressed in terms of the usual macroscopic stresses relative to an elementary material volume. The second approach proposed by Froustey and Lasserre is an energetic based criterion. It has been deduced from experimental observations concerning multiaxial endurance limit and states that crack initiation occurs as soon as the total strain energy density exceeds a critical value. This paper shows that the critical value of the accumulated mesoscopic plastic strain used by Papadopoulos to characterize the endurance limit can be estimated with the global strain energy density at the macroscopic scale. Indeed, it is demonstrated that when dealing with in-phase or out-of-phase synchronous sinusoidal constant amplitude loadings, a single analytical formulation of these criteria can be written either with stress quantities or with energetic ones describing thus the same physical phenomenon. The mean stress influence is discussed; the predictions of the two approaches are similar when the material remains quasi elastic. Another important result concerns the phase difference of the stress tensor components. Very few approaches are able to predict the independence of the fatigue strength on the phase difference between normal and shear stresses. The two proposed criteria reflect this phenomenon which has been experimentally observed for many metals subjected to combined bending-torsion loading. Nevertheless, this independence with regard to the phase shift is no more effective when dealing with some biaxial stress systems with two normal stresses. In this case the two models are consistent with the experimental results since they show a marked influence of the phase difference.
Mon, 01 Jan 2001 00:00:00 GMThttp://hdl.handle.net/10985/112212001-01-01T00:00:00ZMOREL, FranckPALIN-LUC, ThierryFROUSTEY, CatherineMultiaxial fatigue analysis can be categorized into several viewpoints, i.e. empirical formulae, methods based on stress invariants, critical plane approaches, models using averages of stress quantities and energetic considerations. The aim of this paper is not to survey the current state of knowledge concerning multiaxial fatigue but to critically examine two endurance criteria so as to prove that a direct link can be established between them. The first of the two methods, proposed by Papadopoulos, has been built by exploring the fatigue of metals from the mesoscopic scale, that is from the scale of the metal grains of a metallic aggregate. The localized plastic strains developping in some less favourably oriented crystals is considered to be the main cause of fatigue crack nucleation. According to relationships between macroscopic and mesoscopic quantities, this model is finally expressed in terms of the usual macroscopic stresses relative to an elementary material volume. The second approach proposed by Froustey and Lasserre is an energetic based criterion. It has been deduced from experimental observations concerning multiaxial endurance limit and states that crack initiation occurs as soon as the total strain energy density exceeds a critical value. This paper shows that the critical value of the accumulated mesoscopic plastic strain used by Papadopoulos to characterize the endurance limit can be estimated with the global strain energy density at the macroscopic scale. Indeed, it is demonstrated that when dealing with in-phase or out-of-phase synchronous sinusoidal constant amplitude loadings, a single analytical formulation of these criteria can be written either with stress quantities or with energetic ones describing thus the same physical phenomenon. The mean stress influence is discussed; the predictions of the two approaches are similar when the material remains quasi elastic. Another important result concerns the phase difference of the stress tensor components. Very few approaches are able to predict the independence of the fatigue strength on the phase difference between normal and shear stresses. The two proposed criteria reflect this phenomenon which has been experimentally observed for many metals subjected to combined bending-torsion loading. Nevertheless, this independence with regard to the phase shift is no more effective when dealing with some biaxial stress systems with two normal stresses. In this case the two models are consistent with the experimental results since they show a marked influence of the phase difference.