Gerard Mauvoisin - Academia.edu (original) (raw)

Papers by Gerard Mauvoisin

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2009

Experimental applications of the methodology developed for spherical indentation are proposed in ... more Experimental applications of the methodology developed for spherical indentation are proposed in this paper. Two quasi-spherical indenters with different shapes were used in order to evaluate the stress-strain curve of five steels. Although the shape of the indenter was not perfectly spherical, it was shown that models developed for spherical indentation can be used with an adequate correction. The results are in good agreement with those obtained by tensile tests. Moreover, the case of the austenitic alloy (AISI 316L) revealed the importance of sample preparation for the experimental results.

Computational Materials Science, 2009

We proposed an application of inverse approach to experimental indentation data in order to deter... more We proposed an application of inverse approach to experimental indentation data in order to determine combined hardening models parameters. It was shown that the use of a model combining isotropic and kinematic hardening allows a better description of cyclic indentation than isotropic hardening models. It was also shown that inverse analysis applied to experimental cyclic indentation curves can give a quite good approximation of the monotonic stress-strain curve and the beginning of cyclic tensile test. However, it appeared that the combined hardening model, used in this paper, is not sufficient to take into account all phenomenons coming in the steels behaviour under cyclic indentation.

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008

An interpretation of spherical indentation experiments and the determination of hardening law par... more An interpretation of spherical indentation experiments and the determination of hardening law parameters is the challenge in this paper. A new protocol based on multiple cyclic loading allowed models describing the indentation data changes to be determined from a numerical study. Inversion of these models, determined for two constitutive equations with isotropic hardening, combined with a sensitivity study enabled the study of the uniqueness of the solution. It is shown that although the new protocol is not necessary to determine the two Hollomon equation parameters, it is necessary to determine accurate values of the three Ludwig equation parameters.

Materials & Design, 2010

Experimental applications of two different approaches for interpretation of instrumented indentat... more Experimental applications of two different approaches for interpretation of instrumented indentation experiments are proposed in this paper. The first approach is the application of methodology developed for spherical indentation based on models. The second approach is the application of inverse algorithm based on the minimization between experiments and simulated data. It was shown that inverse approach lead to a good prediction of elastic modulus for metals with a face-centred cubic crystal structure. However, for metals with a body-centred cubic crystal structure identified elastic modulus was 10% under values obtained by ultra-sound method. It was then shown that models developed for spherical indentation give more accurate results than inverse approach. Moreover, a sensitivity study of mesh density in inverse identification shows that the more the mesh density the more accurate the results.

Mecanique & Industries, 2003

Résumé La méthode de détermination du profil de dureté par perçage des aciers traités en surface ... more Résumé La méthode de détermination du profil de dureté par perçage des aciers traités en surface repose sur la proportionnalité entre les efforts de perçage et la dureté du matériau percé. Les exemples d'application présentés montrent que la méthode peut être appliquée avec succès sur les aciers traités en surface. Cependant, si la surface traitée est très mince, inférieure à 0,2 mm, les résultats sont imprécis. De même, si la surface est très cassante comme dans le cas de certaines pièces nitrurées la technique du perçage est sans succès. Enfin, pour des conditions expérimentales fixées, les tests sur des aciers homogènes montrent que le rapport effort de perçage sur dureté (R/HV) dépend de la ductilité du matériau. En conséquence, les résultats sont assez imprécis lorsque la méthode est employée sur des pièces traitées dont le coeur est beaucoup plus ductile que la surface, ce qui est le cas de certains aciers nitrurés.  2003 Publié par Éditions scientifiques et médicales Elsevier SAS.

Measurement, 1999

ABSTRACT

Mechanics of Materials, 2010

The study of analytical models for the determination of the contact radius between a spherical in... more The study of analytical models for the determination of the contact radius between a spherical indenter and an elastic–plastic material is presented in this paper. Experimental results obtained for different spheroidized steels are compared to those obtained ...

Comptes Rendus De L Academie Des Sciences Serie Ii Fascicule B-mecanique Physique Astronomie, 1999

De I'analyse de la r sistance interne par per zage la d termination du profil de duret des aciers... more De I'analyse de la r sistance interne par per zage la d termination du profil de duret des aciers trait s en surface

Phase shifting technique is more and more employed in photomechanic even on optical methods which... more Phase shifting technique is more and more employed in photomechanic even on optical methods which are not well-adapted for it, particularly for shadow moire method where the phase shift is realized by translating the object. In such case, good results are obtained only if translation is executed with high accuracy. We present the effect of unaccuracy phase shift evaluation on the form and amplitude of calculated phase error. In this article, we propose a new automated procedure based on the use of a 2.D. F.F.T. algorithm to determine precisely the phase shift value introduced by a coarse object translation. WE finally present an application on the out-of-plane displacement measurement on bended plate in corrugated paper. An order of largeness is given for await precision on such measurement.

The shadow moire is one of the optical techniques which is able to give level lines of an object ... more The shadow moire is one of the optical techniques which is able to give level lines of an object with respect to a master grating plane. Level lines result from the interferences between the lines of the master grid and their shadow projected by a ponctual source light. The sensitivity of this procedure is a few tenths of millimeters in best cases. A complete study is presented showing the influence of the different parameters. It is shown that only one possibility is available. We then propose an automated procedure based on a 2D FFT algorithm to determine precisely the phase shift value introduced by a coarse object translation. Finally, the presented applications on 3D shape reconstruction and out-of-plane displacement field measurement show the potentiality of shadow moire is greatly improved with an accuracy of 0.02 mm.

Applied Optics, 1994

Shadow moiré shows contour lines of an object with respect to a master grating plane; they result... more Shadow moiré shows contour lines of an object with respect to a master grating plane; they result from the interference between the lines of the master grid and their shadow projected by a point source of light. In best cases the sensitivity of this procedure is a few tenths of a millimeter. The introduction of a phase-shifting procedure gives a better resolution, but the problem in practice is how can we shift the phase of the interferogram into shadow moiré? A complete study is presented showing the influence of different parameters. It is shown that only one possibility is available. Some applications to threedimensional shape reconstructions are presented with an accuracy of 0.01 mm, showing that the potentiality of shadow moiré is greatly improved.

International Journal of Solids and Structures, 2006

Knowledge of the relationship between the penetration depth and the contact radius is required in... more Knowledge of the relationship between the penetration depth and the contact radius is required in order to determine the mechanical properties of a material starting from an instrumented indentation test. The aim of this work is to propose a new penetration depth-contact radius relationship valid for most metals which are deformed plastically by parabolic and spherical indenters. Numerical simulation results of the indentation of an elastic-plastic half-space by a frictionless rigid paraboloïd of revolution show that the contact radius-indentation depth relationship can be represented by a power law, which depends on the reduced YoungÕs modulus of the contact, on the strain hardening exponent and on the yield stress of the indented material. In order to use the proposed formulation for experimental spherical indentations, adaptation of the model is performed in the case of a rigid spherical indenter. Compared to the previous formulations, the model proposed in the present study for spherical indentation has the advantage of being accurate in the plastic regime for a large range of contact radii and for materials of well-developed yield stress. Lastly, a simple criterion, depending on the material mechanical properties, is proposed in order to know when piling-up appears for the spherical indentation.

Journal of Materials Processing Technology, 2003

The present paper uses the indentation of materials with a yield strength gradient, by spherical ... more The present paper uses the indentation of materials with a yield strength gradient, by spherical indenters in order to obtain Vickers hardness profile.Using finite element modelling, a simulation of elasto-plastic spherical indentation of materials with a yield stress was carried out. A theoretical model for effective mean pressure evolution of the spherical indentation on the surface of heat treated steels

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2002

An elasto-plastic indentation study on materials with a yield strength gradient like steels which... more An elasto-plastic indentation study on materials with a yield strength gradient like steels which have undergone thermal hardening such as nitriding, is carried out using experimental and finite element methods. The analysis of the normalized mean contact pressure as a function of a dimensionless strain parameter for graded materials shows that the mean contact pressure presents the same tendency as equivalent homogeneous materials. A simple model for the average plastic zone radius of graded materials is given. A relation is developed to predict the hardness variation as a function of the indentation depth. Lastly, a theory based on the effective evolution of hardness is proposed to determine the yield stress and hardness profile for materials with a decreasing yield stress with depth. Results for carbo-nitriding steels obtained by the standard Vickers micro hardness techniques are compared with those obtained by the proposed method.

Mechanics of Materials, 2008

An experimental method to determine contact radius changes during a spherical instrumented indent... more An experimental method to determine contact radius changes during a spherical instrumented indentation test is proposed in this paper. This method is based on the Hertz theory and only depends on the elastic properties of both the indenter and the sample. The programming of several loading, unloading and reloading cycles has allowed the determination of the unloading stiffness changes and consequently the contact radius changes. Numerical results have shown that the proposed method is sensitive to the piling-up or sinking-in. From the contact radius changes we have proposed a new procedure in order to obtain the real indentation load-depth curve from the measured curve. An experimental study has allowed us to validate our procedure during the beginning of the unloading cycle.

International Journal of Mechanical Sciences, 2001

A new numerical approach to indentation problems is developed for hardened materials. A relations... more A new numerical approach to indentation problems is developed for hardened materials. A relationship between load, displacement, flow stress and strain hardening exponent of heat treated materials with a hard film, is given.This method is based on the minimisation of the error between the experimental curve (load–displacement of the indenter) and the theoretical curve, function of the mechanical and geometrical

International Journal of Machine Tools & Manufacture, 2003

A drilling method developed by the authors for the measurement of the hardness profile for surfac... more A drilling method developed by the authors for the measurement of the hardness profile for surface heat treated steels is based on the proportionality between drilling thrust and material hardness. However, parameters other than hardness related to the material can modify the cutting thrust level. In order to study the influence of the microstructure, the ductility, the toughness and the work hardening of material on the drilling thrust, a few tests were carried out in this work. Tensile and impact tests were carried out on different materials. Moreover, micrographic observations and Vickers micro-hardness were performed on the chips. The study allowed two groups of materials to be distinguished according to the drilling thrust to hardness ratio (R/HV). The first includes not very ductile materials presenting an about constant and low value of R/HV, short, thin and not very work hardened chips. The second includes ductile materials presenting a non constant and high value of R/HV, long, thick and very work hardened chips. As a consequence, the hardness profile determination by drilling method is reliable only if the R/HV ratio is about the same for the treated layer and for the substrate, i.e. if the difference in ductility between the treated layer and the substrate is not very high. 

Journal of Materials Processing Technology, 2008

Temperature Thermo-viscoplastic model a b s t r a c t

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2009

Experimental applications of the methodology developed for spherical indentation are proposed in ... more Experimental applications of the methodology developed for spherical indentation are proposed in this paper. Two quasi-spherical indenters with different shapes were used in order to evaluate the stress-strain curve of five steels. Although the shape of the indenter was not perfectly spherical, it was shown that models developed for spherical indentation can be used with an adequate correction. The results are in good agreement with those obtained by tensile tests. Moreover, the case of the austenitic alloy (AISI 316L) revealed the importance of sample preparation for the experimental results.

Computational Materials Science, 2009

We proposed an application of inverse approach to experimental indentation data in order to deter... more We proposed an application of inverse approach to experimental indentation data in order to determine combined hardening models parameters. It was shown that the use of a model combining isotropic and kinematic hardening allows a better description of cyclic indentation than isotropic hardening models. It was also shown that inverse analysis applied to experimental cyclic indentation curves can give a quite good approximation of the monotonic stress-strain curve and the beginning of cyclic tensile test. However, it appeared that the combined hardening model, used in this paper, is not sufficient to take into account all phenomenons coming in the steels behaviour under cyclic indentation.

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008

An interpretation of spherical indentation experiments and the determination of hardening law par... more An interpretation of spherical indentation experiments and the determination of hardening law parameters is the challenge in this paper. A new protocol based on multiple cyclic loading allowed models describing the indentation data changes to be determined from a numerical study. Inversion of these models, determined for two constitutive equations with isotropic hardening, combined with a sensitivity study enabled the study of the uniqueness of the solution. It is shown that although the new protocol is not necessary to determine the two Hollomon equation parameters, it is necessary to determine accurate values of the three Ludwig equation parameters.

Materials & Design, 2010

Experimental applications of two different approaches for interpretation of instrumented indentat... more Experimental applications of two different approaches for interpretation of instrumented indentation experiments are proposed in this paper. The first approach is the application of methodology developed for spherical indentation based on models. The second approach is the application of inverse algorithm based on the minimization between experiments and simulated data. It was shown that inverse approach lead to a good prediction of elastic modulus for metals with a face-centred cubic crystal structure. However, for metals with a body-centred cubic crystal structure identified elastic modulus was 10% under values obtained by ultra-sound method. It was then shown that models developed for spherical indentation give more accurate results than inverse approach. Moreover, a sensitivity study of mesh density in inverse identification shows that the more the mesh density the more accurate the results.

Mecanique & Industries, 2003

Résumé La méthode de détermination du profil de dureté par perçage des aciers traités en surface ... more Résumé La méthode de détermination du profil de dureté par perçage des aciers traités en surface repose sur la proportionnalité entre les efforts de perçage et la dureté du matériau percé. Les exemples d'application présentés montrent que la méthode peut être appliquée avec succès sur les aciers traités en surface. Cependant, si la surface traitée est très mince, inférieure à 0,2 mm, les résultats sont imprécis. De même, si la surface est très cassante comme dans le cas de certaines pièces nitrurées la technique du perçage est sans succès. Enfin, pour des conditions expérimentales fixées, les tests sur des aciers homogènes montrent que le rapport effort de perçage sur dureté (R/HV) dépend de la ductilité du matériau. En conséquence, les résultats sont assez imprécis lorsque la méthode est employée sur des pièces traitées dont le coeur est beaucoup plus ductile que la surface, ce qui est le cas de certains aciers nitrurés.  2003 Publié par Éditions scientifiques et médicales Elsevier SAS.

Measurement, 1999

ABSTRACT

Mechanics of Materials, 2010

The study of analytical models for the determination of the contact radius between a spherical in... more The study of analytical models for the determination of the contact radius between a spherical indenter and an elastic–plastic material is presented in this paper. Experimental results obtained for different spheroidized steels are compared to those obtained ...

Comptes Rendus De L Academie Des Sciences Serie Ii Fascicule B-mecanique Physique Astronomie, 1999

De I'analyse de la r sistance interne par per zage la d termination du profil de duret des aciers... more De I'analyse de la r sistance interne par per zage la d termination du profil de duret des aciers trait s en surface

Phase shifting technique is more and more employed in photomechanic even on optical methods which... more Phase shifting technique is more and more employed in photomechanic even on optical methods which are not well-adapted for it, particularly for shadow moire method where the phase shift is realized by translating the object. In such case, good results are obtained only if translation is executed with high accuracy. We present the effect of unaccuracy phase shift evaluation on the form and amplitude of calculated phase error. In this article, we propose a new automated procedure based on the use of a 2.D. F.F.T. algorithm to determine precisely the phase shift value introduced by a coarse object translation. WE finally present an application on the out-of-plane displacement measurement on bended plate in corrugated paper. An order of largeness is given for await precision on such measurement.

The shadow moire is one of the optical techniques which is able to give level lines of an object ... more The shadow moire is one of the optical techniques which is able to give level lines of an object with respect to a master grating plane. Level lines result from the interferences between the lines of the master grid and their shadow projected by a ponctual source light. The sensitivity of this procedure is a few tenths of millimeters in best cases. A complete study is presented showing the influence of the different parameters. It is shown that only one possibility is available. We then propose an automated procedure based on a 2D FFT algorithm to determine precisely the phase shift value introduced by a coarse object translation. Finally, the presented applications on 3D shape reconstruction and out-of-plane displacement field measurement show the potentiality of shadow moire is greatly improved with an accuracy of 0.02 mm.

Applied Optics, 1994

Shadow moiré shows contour lines of an object with respect to a master grating plane; they result... more Shadow moiré shows contour lines of an object with respect to a master grating plane; they result from the interference between the lines of the master grid and their shadow projected by a point source of light. In best cases the sensitivity of this procedure is a few tenths of a millimeter. The introduction of a phase-shifting procedure gives a better resolution, but the problem in practice is how can we shift the phase of the interferogram into shadow moiré? A complete study is presented showing the influence of different parameters. It is shown that only one possibility is available. Some applications to threedimensional shape reconstructions are presented with an accuracy of 0.01 mm, showing that the potentiality of shadow moiré is greatly improved.

International Journal of Solids and Structures, 2006

Knowledge of the relationship between the penetration depth and the contact radius is required in... more Knowledge of the relationship between the penetration depth and the contact radius is required in order to determine the mechanical properties of a material starting from an instrumented indentation test. The aim of this work is to propose a new penetration depth-contact radius relationship valid for most metals which are deformed plastically by parabolic and spherical indenters. Numerical simulation results of the indentation of an elastic-plastic half-space by a frictionless rigid paraboloïd of revolution show that the contact radius-indentation depth relationship can be represented by a power law, which depends on the reduced YoungÕs modulus of the contact, on the strain hardening exponent and on the yield stress of the indented material. In order to use the proposed formulation for experimental spherical indentations, adaptation of the model is performed in the case of a rigid spherical indenter. Compared to the previous formulations, the model proposed in the present study for spherical indentation has the advantage of being accurate in the plastic regime for a large range of contact radii and for materials of well-developed yield stress. Lastly, a simple criterion, depending on the material mechanical properties, is proposed in order to know when piling-up appears for the spherical indentation.

Journal of Materials Processing Technology, 2003

The present paper uses the indentation of materials with a yield strength gradient, by spherical ... more The present paper uses the indentation of materials with a yield strength gradient, by spherical indenters in order to obtain Vickers hardness profile.Using finite element modelling, a simulation of elasto-plastic spherical indentation of materials with a yield stress was carried out. A theoretical model for effective mean pressure evolution of the spherical indentation on the surface of heat treated steels

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2002

An elasto-plastic indentation study on materials with a yield strength gradient like steels which... more An elasto-plastic indentation study on materials with a yield strength gradient like steels which have undergone thermal hardening such as nitriding, is carried out using experimental and finite element methods. The analysis of the normalized mean contact pressure as a function of a dimensionless strain parameter for graded materials shows that the mean contact pressure presents the same tendency as equivalent homogeneous materials. A simple model for the average plastic zone radius of graded materials is given. A relation is developed to predict the hardness variation as a function of the indentation depth. Lastly, a theory based on the effective evolution of hardness is proposed to determine the yield stress and hardness profile for materials with a decreasing yield stress with depth. Results for carbo-nitriding steels obtained by the standard Vickers micro hardness techniques are compared with those obtained by the proposed method.

Mechanics of Materials, 2008

An experimental method to determine contact radius changes during a spherical instrumented indent... more An experimental method to determine contact radius changes during a spherical instrumented indentation test is proposed in this paper. This method is based on the Hertz theory and only depends on the elastic properties of both the indenter and the sample. The programming of several loading, unloading and reloading cycles has allowed the determination of the unloading stiffness changes and consequently the contact radius changes. Numerical results have shown that the proposed method is sensitive to the piling-up or sinking-in. From the contact radius changes we have proposed a new procedure in order to obtain the real indentation load-depth curve from the measured curve. An experimental study has allowed us to validate our procedure during the beginning of the unloading cycle.

International Journal of Mechanical Sciences, 2001

A new numerical approach to indentation problems is developed for hardened materials. A relations... more A new numerical approach to indentation problems is developed for hardened materials. A relationship between load, displacement, flow stress and strain hardening exponent of heat treated materials with a hard film, is given.This method is based on the minimisation of the error between the experimental curve (load–displacement of the indenter) and the theoretical curve, function of the mechanical and geometrical

International Journal of Machine Tools & Manufacture, 2003

A drilling method developed by the authors for the measurement of the hardness profile for surfac... more A drilling method developed by the authors for the measurement of the hardness profile for surface heat treated steels is based on the proportionality between drilling thrust and material hardness. However, parameters other than hardness related to the material can modify the cutting thrust level. In order to study the influence of the microstructure, the ductility, the toughness and the work hardening of material on the drilling thrust, a few tests were carried out in this work. Tensile and impact tests were carried out on different materials. Moreover, micrographic observations and Vickers micro-hardness were performed on the chips. The study allowed two groups of materials to be distinguished according to the drilling thrust to hardness ratio (R/HV). The first includes not very ductile materials presenting an about constant and low value of R/HV, short, thin and not very work hardened chips. The second includes ductile materials presenting a non constant and high value of R/HV, long, thick and very work hardened chips. As a consequence, the hardness profile determination by drilling method is reliable only if the R/HV ratio is about the same for the treated layer and for the substrate, i.e. if the difference in ductility between the treated layer and the substrate is not very high. 

Journal of Materials Processing Technology, 2008

Temperature Thermo-viscoplastic model a b s t r a c t