B. Guelorget - Academia.edu (original) (raw)
Papers by B. Guelorget
The main objective of this work is to compare numerically simulated load– indentation depth curve... more The main objective of this work is to compare numerically simulated load– indentation depth curves together with deformation and stress fields underneath a sharp indenter for a set of mystical materials. Firstly, a numerical simulation and experimental validation of the microindentation test applied to three different bulk elastoplastic materials (copper, stainless steel and pure aluminium) using two indenters (Berkovich and spherical) are presented. The simulation of these microindentation tests is carried out using the finite element large strain elastoplastic and contact models. The corresponding results are particularly aimed at addressing the following aspects: the influence of the indenter geometry on both the load–indentation depth curve and range of plastic strains involved in the test, the comparison of the 3D results for the sharp indenter with those of the 2D approximation, the capabilities of the modelling through experimental validation of the numerical predictions and, in addition, an assessment of the indentation size effect. Secondly, the numerical results of Berkovich indentation applied to a set of mystical materials are exhaustively discussed. Although it is effectively shown that these mystical materials exhibit indistinguishable load–penetration depth curves during the loading phase, an important aspect that has not been previously addressed is that some clear differences in their responses are obtained for the unloading stage. Finally, the deformation and stress contours at the maximum indentation force and after unloading are particularly analysed.
Experimental Analysis of Nano and Engineering Materials and Structures, 2007
ABSTRACT The excellent corrosion properties of copper justify its use in a large number of indust... more ABSTRACT The excellent corrosion properties of copper justify its use in a large number of industrial applications, in spite of its low strength in the traditional state. To overcome this problem and to enhance the mechanical behavior of this material, the Surface Mechanical Attrition Treatment (SMAT) seems to be well-adapted [1]. As shown in several previous works, SMA-Treatment induces a grain refinement up to the nanometer scale in the top surface layer of the treated sample, through severe plastic deformation performed at high strain rate. While the grain size of the untreated material is in the micrometer scale, nanograins are generated beneath the treated surface. Between this nanocrystallised layer and the bulk of the sample, a transition layer is also present which is characterised by a grain size gradient: the grain size grows from the nanometer to the micrometer scale as the depth below the treated surface increases. The treated metal can thus be seen as a multilayered material. All these microstructural changes lead to strong modifications of the plastic properties of the samples subjected to SMAT [2] [3]. In the last years, several methods have been proposed to determine the Young’s modulus, the yield stress and the strain hardening coefficient using microindentation tests. More recently, Cao and Lu [4] [5] developed a new inverse method to extract plastic properties of metallic materials based on instrumented spherical indentation.
Materials Science Forum, 2002
Matériaux & Techniques, 2015
Micro-pillar compression tests were used to study the mechanical behavior of a stainless steel tr... more Micro-pillar compression tests were used to study the mechanical behavior of a stainless steel treated by SMAT (Surface Mechanical Attrition Treatment), particularly the induced nanocrystalline surface layer. Micro-pillars were first machined using a Focused Ion Beam (FIB) on the cross-section of the SMATed specimen. They were then deformed with a flat head mounted on a nanoindenter. Stress-strain curves were obtained for various micro-pillars machined at different distances from the SMATed surface. Deformed micro-pillars after compression tests were examined using FEG SEM to analyze deformation mechanisms. According to the obtained stress-strain curves, the mechanical strength of the stainless steel is significantly improved after SMAT, and the deformation mechanisms of the material appear to be different according to the distance from the treated surface.
Scripta Materialia, 2009
In this paper, electronic speckle pattern interferometry strain rate measurements are used to qua... more In this paper, electronic speckle pattern interferometry strain rate measurements are used to quantify the width of the strain localization band, which occurs when a sheet specimen is submitted to tension. It is shown that the width of this band decreases with increasing strain. Just before fracture, this measured width is about five times wider than the shear band and the initial sheet thickness.
Speckle06: Speckles, From Grains to Flowers, 2006
ABSTRACT Localization of plastic strain has been studied by measuring strain and strain rate duri... more ABSTRACT Localization of plastic strain has been studied by measuring strain and strain rate during tensile test1. Pictures were continuously recorded during the experiment and in-plane Electronic Speckle Pattern Interferometry (ESPI) pictures were generated afterwards, by subtracting couples of images. A square grid of 3 mm separation was drawn on the specimen to determine the true stress-true strain curve, while fringe patterns gave an access to relative displacements. Strain, average strain and strain rate were deduced. An uncertainty evaluation on these parameters was carried out applying the so-called law of propagation of uncertainties (ISO 07-0202).
Materials Letters, 2007
Microindentation (depth of indents = 500 nm) is performed on a longitudinal section of a semi-har... more Microindentation (depth of indents = 500 nm) is performed on a longitudinal section of a semi-hard copper sheet, which was broken in a tensile machine [B. Guelorget, M. François, C. Vial-Edwards, G. Montay, L. Daniel, J. Lu, Mater. Sci. Eng., A Struct. Mater.: Prop. Microstruct. Process. 415 ]. As expected, the shorter the distance between the measured point and the fracture, the higher the hardness, due to the work hardening. However, the main goal of our investigation was to observe the variation of Young's modulus, that could be induced by damage evolution. It was found, indeed, that Young's modulus decreases by 36% within a distance of 300 μm from the fracture and is constant beyond. The corresponding evaluated damage is 0.36, with an accuracy better than 0.02. Thus, the measurement of the local variation of Young's modulus through microindentation can be used as a new way of determination of local damage.
International Journal of Solids and Structures, 2014
Experimental Analysis of Nano and Engineering Materials and Structures, 2007
ABSTRACT Local determination of Young’s modulus and hardness is performed through microindentatio... more ABSTRACT Local determination of Young’s modulus and hardness is performed through microindentation on a longitudinal section of a semi-hard copper sheet, which was broken in a tensile machine. (i) the shorter the distance between the measured point and the fracture, the higher the hardness; (ii) local variations of Young’s modulus in the neighbouring of the fracture gives access to local damage variations. Using an inverse method, yield stress and strain hardening coefficient are evaluated in the localized neck.
Experimental Analysis of Nano and Engineering Materials and Structures, 2007
ABSTRACT In-plane ESPI strain rate measurement during a tensile test is used to determine plastic... more ABSTRACT In-plane ESPI strain rate measurement during a tensile test is used to determine plastic strain in a semi-hard copper sheet specimen during the localization process in the neck. The width of the localization zone is deduced at several steps of the experiment.
Journal of Metastable and Nanocrystalline Materials, 2005
International Journal of Forming Processes, 2005
We report extensive x-ray diffractometric measurements as well as conventional metallurgical and ... more We report extensive x-ray diffractometric measurements as well as conventional metallurgical and mechanical tests on thin steel sheets of FeP04 for deep drawability in order to identify key microscopic parameters that govern both texture evolution and mechanical response as function of the type of loading path. While Microhardness measurements, as expected show an evolution as function of material work hardening, the distribution of grain size seems to be unaffected by the different type of loading path. Quantitative texture measurements demonstrates a development of different texture components depending on the type of loading path used to achieve the plastic deformation. Indeed, when compared to as received samples significant variation was found on Poles density and orientation distribution unction versus the type of applied stress states. f
We investigate the effects of roughness and fractality on the normal contact stiffness of rough s... more We investigate the effects of roughness and fractality on the normal contact stiffness of rough surfaces. Samples of isotropically roughened aluminium surfaces are considered. The roughness and fractal dimension were altered through blasting using different sized particles. Subsequently, surface mechanical attrition treatment (SMAT) was applied to the surfaces in order to modify the surface at the micro-scale. The surface topology was characterised by interferometry-based profilometry. The normal contact stiffness was measured through nano-indentation with a flat tip utilising the partial unloading method. We focus on establishing the relationships between surface stiffness and roughness, combined with the effects of fractal dimension. The experimental results, for a wide range of surfaces, showed that the measured contact stiffness depended very closely on surfaces' root mean squared (RMS) slope and their fractal dimension, with correlation coefficients of around 90%, whilst a relatively weak correlation coefficient of 57% was found between the contact stiffness and RMS roughness.
Eighth International Symposium on Laser Metrology, 2005
Forming Limit Diagrams (FLD"s) can be defined by the criteria of either diffuse or local... more Forming Limit Diagrams (FLD"s) can be defined by the criteria of either diffuse or localized necks. We used Electronic Speckle Pattern Interferometry (ESPI) in commercial 1100 aluminum sheet metals annealed at 400°C to determine the strains at which both types of neck started in uniaxial tension (U) and in quasi plane strain tension (PS) tests. In biaxial (B) loading we
Journal of Metastable and Nanocrystalline Materials, 2004
X-ray diffraction using synchrotron radiation and instrumented indentation experiments has been c... more X-ray diffraction using synchrotron radiation and instrumented indentation experiments has been carried out to track free volume changes and local reodering following plastic straining by indentation below the glass transition temperature Tg in the Zr 60 Ni 10 Cu 20 Al 10 , Zr 65 Ni 10 Cu 15 Al 10 and Zr 65 Ni 10 Cu 7.5 Al 7.5 Pd 10 metallic glass forming systems. A quantitative diffraction l ine profiles modifications are observed during scanning strained and unstrained zones of the same specimen. We have found that the first diffractogram maximum intensity in transmission and the average inter-atomic spacing position are significantly affected in the overlapping shear bands around impressions. The surface uplift of the pile-up around indents has been assessed using a profilometer. It is shown that the inhomogeneous deformation results in an inhomogeneous distribution of free volume concentration. Substantial plastic deformation is determined form hysteresis loops recorded during nanoindentation experiments. While the ratio of the dissipated energy to total indentation work is quite similar for Zr-based metallic glasses, continuous stiffness measurements showed an appreciable difference in the evolution of the elastic modulus and hardness as function of penetration depth.
Experimental Analysis of Nano and Engineering Materials and Structures, 2007
... Guillaume Montay1, Bruno Guelorget1, Ignacio Lira2, Marie Tourneix1, Manuel François1 and Cri... more ... Guillaume Montay1, Bruno Guelorget1, Ignacio Lira2, Marie Tourneix1, Manuel François1 and Cristián Vial-Edwards2 1Université de Technologie de Troyes, Laboratoire des ... In it, an initially flat specimen is placed between a matrix and a blank holder, and hydraulic pressure is ...
Fringe 2005, 2006
ABSTRACT In this paper, an original application of ESPI in materials engineering has been describ... more ABSTRACT In this paper, an original application of ESPI in materials engineering has been described. The technique was used to analyze a bulge test in order to study strain localization by following the strain rate progress. Results show that ESPI allows detecting clearly the two stages of localization, namely, the diffuse and localized necks. Using this technique, forming limit diagrams can thus be established accurately.
WAGNER:SHOT PEENING O-BK, 2003
Experimental conditions on shot peening and residual stress measurement are shown on and respecti... more Experimental conditions on shot peening and residual stress measurement are shown on and respectively.
This paper describes influence of factors such as particle size (0.55-2.2 mm), particle velocity ... more This paper describes influence of factors such as particle size (0.55-2.2 mm), particle velocity (15-35 mls) and work hardness on surface integrity. Hardness, residual stress and crystal transformation of areas affected by shot peening or grit blasting are examined. In order to clarify the influences of those factors on the surface integrity, a medium carbon steel (C:0.45%, 180HV) and an austenitic stainless steel (SUS304, 210HV) were peened by a centrifugal type peening machine using cast steel particles (650-800HV). The following results were obtained: (1) Shot peening maximum hardness is lower while depth of work-hardened layer is thicker. (2) Compressive residual stresses on the peened surface are larger than that of grit blasting. (3) Critical thickness of shot peening is about 50% thicker than that of grit blasting. (4)Strain-induced transformation happens with shot peening and grit blasting.
The main objective of this work is to compare numerically simulated load– indentation depth curve... more The main objective of this work is to compare numerically simulated load– indentation depth curves together with deformation and stress fields underneath a sharp indenter for a set of mystical materials. Firstly, a numerical simulation and experimental validation of the microindentation test applied to three different bulk elastoplastic materials (copper, stainless steel and pure aluminium) using two indenters (Berkovich and spherical) are presented. The simulation of these microindentation tests is carried out using the finite element large strain elastoplastic and contact models. The corresponding results are particularly aimed at addressing the following aspects: the influence of the indenter geometry on both the load–indentation depth curve and range of plastic strains involved in the test, the comparison of the 3D results for the sharp indenter with those of the 2D approximation, the capabilities of the modelling through experimental validation of the numerical predictions and, in addition, an assessment of the indentation size effect. Secondly, the numerical results of Berkovich indentation applied to a set of mystical materials are exhaustively discussed. Although it is effectively shown that these mystical materials exhibit indistinguishable load–penetration depth curves during the loading phase, an important aspect that has not been previously addressed is that some clear differences in their responses are obtained for the unloading stage. Finally, the deformation and stress contours at the maximum indentation force and after unloading are particularly analysed.
Experimental Analysis of Nano and Engineering Materials and Structures, 2007
ABSTRACT The excellent corrosion properties of copper justify its use in a large number of indust... more ABSTRACT The excellent corrosion properties of copper justify its use in a large number of industrial applications, in spite of its low strength in the traditional state. To overcome this problem and to enhance the mechanical behavior of this material, the Surface Mechanical Attrition Treatment (SMAT) seems to be well-adapted [1]. As shown in several previous works, SMA-Treatment induces a grain refinement up to the nanometer scale in the top surface layer of the treated sample, through severe plastic deformation performed at high strain rate. While the grain size of the untreated material is in the micrometer scale, nanograins are generated beneath the treated surface. Between this nanocrystallised layer and the bulk of the sample, a transition layer is also present which is characterised by a grain size gradient: the grain size grows from the nanometer to the micrometer scale as the depth below the treated surface increases. The treated metal can thus be seen as a multilayered material. All these microstructural changes lead to strong modifications of the plastic properties of the samples subjected to SMAT [2] [3]. In the last years, several methods have been proposed to determine the Young’s modulus, the yield stress and the strain hardening coefficient using microindentation tests. More recently, Cao and Lu [4] [5] developed a new inverse method to extract plastic properties of metallic materials based on instrumented spherical indentation.
Materials Science Forum, 2002
Matériaux & Techniques, 2015
Micro-pillar compression tests were used to study the mechanical behavior of a stainless steel tr... more Micro-pillar compression tests were used to study the mechanical behavior of a stainless steel treated by SMAT (Surface Mechanical Attrition Treatment), particularly the induced nanocrystalline surface layer. Micro-pillars were first machined using a Focused Ion Beam (FIB) on the cross-section of the SMATed specimen. They were then deformed with a flat head mounted on a nanoindenter. Stress-strain curves were obtained for various micro-pillars machined at different distances from the SMATed surface. Deformed micro-pillars after compression tests were examined using FEG SEM to analyze deformation mechanisms. According to the obtained stress-strain curves, the mechanical strength of the stainless steel is significantly improved after SMAT, and the deformation mechanisms of the material appear to be different according to the distance from the treated surface.
Scripta Materialia, 2009
In this paper, electronic speckle pattern interferometry strain rate measurements are used to qua... more In this paper, electronic speckle pattern interferometry strain rate measurements are used to quantify the width of the strain localization band, which occurs when a sheet specimen is submitted to tension. It is shown that the width of this band decreases with increasing strain. Just before fracture, this measured width is about five times wider than the shear band and the initial sheet thickness.
Speckle06: Speckles, From Grains to Flowers, 2006
ABSTRACT Localization of plastic strain has been studied by measuring strain and strain rate duri... more ABSTRACT Localization of plastic strain has been studied by measuring strain and strain rate during tensile test1. Pictures were continuously recorded during the experiment and in-plane Electronic Speckle Pattern Interferometry (ESPI) pictures were generated afterwards, by subtracting couples of images. A square grid of 3 mm separation was drawn on the specimen to determine the true stress-true strain curve, while fringe patterns gave an access to relative displacements. Strain, average strain and strain rate were deduced. An uncertainty evaluation on these parameters was carried out applying the so-called law of propagation of uncertainties (ISO 07-0202).
Materials Letters, 2007
Microindentation (depth of indents = 500 nm) is performed on a longitudinal section of a semi-har... more Microindentation (depth of indents = 500 nm) is performed on a longitudinal section of a semi-hard copper sheet, which was broken in a tensile machine [B. Guelorget, M. François, C. Vial-Edwards, G. Montay, L. Daniel, J. Lu, Mater. Sci. Eng., A Struct. Mater.: Prop. Microstruct. Process. 415 ]. As expected, the shorter the distance between the measured point and the fracture, the higher the hardness, due to the work hardening. However, the main goal of our investigation was to observe the variation of Young's modulus, that could be induced by damage evolution. It was found, indeed, that Young's modulus decreases by 36% within a distance of 300 μm from the fracture and is constant beyond. The corresponding evaluated damage is 0.36, with an accuracy better than 0.02. Thus, the measurement of the local variation of Young's modulus through microindentation can be used as a new way of determination of local damage.
International Journal of Solids and Structures, 2014
Experimental Analysis of Nano and Engineering Materials and Structures, 2007
ABSTRACT Local determination of Young’s modulus and hardness is performed through microindentatio... more ABSTRACT Local determination of Young’s modulus and hardness is performed through microindentation on a longitudinal section of a semi-hard copper sheet, which was broken in a tensile machine. (i) the shorter the distance between the measured point and the fracture, the higher the hardness; (ii) local variations of Young’s modulus in the neighbouring of the fracture gives access to local damage variations. Using an inverse method, yield stress and strain hardening coefficient are evaluated in the localized neck.
Experimental Analysis of Nano and Engineering Materials and Structures, 2007
ABSTRACT In-plane ESPI strain rate measurement during a tensile test is used to determine plastic... more ABSTRACT In-plane ESPI strain rate measurement during a tensile test is used to determine plastic strain in a semi-hard copper sheet specimen during the localization process in the neck. The width of the localization zone is deduced at several steps of the experiment.
Journal of Metastable and Nanocrystalline Materials, 2005
International Journal of Forming Processes, 2005
We report extensive x-ray diffractometric measurements as well as conventional metallurgical and ... more We report extensive x-ray diffractometric measurements as well as conventional metallurgical and mechanical tests on thin steel sheets of FeP04 for deep drawability in order to identify key microscopic parameters that govern both texture evolution and mechanical response as function of the type of loading path. While Microhardness measurements, as expected show an evolution as function of material work hardening, the distribution of grain size seems to be unaffected by the different type of loading path. Quantitative texture measurements demonstrates a development of different texture components depending on the type of loading path used to achieve the plastic deformation. Indeed, when compared to as received samples significant variation was found on Poles density and orientation distribution unction versus the type of applied stress states. f
We investigate the effects of roughness and fractality on the normal contact stiffness of rough s... more We investigate the effects of roughness and fractality on the normal contact stiffness of rough surfaces. Samples of isotropically roughened aluminium surfaces are considered. The roughness and fractal dimension were altered through blasting using different sized particles. Subsequently, surface mechanical attrition treatment (SMAT) was applied to the surfaces in order to modify the surface at the micro-scale. The surface topology was characterised by interferometry-based profilometry. The normal contact stiffness was measured through nano-indentation with a flat tip utilising the partial unloading method. We focus on establishing the relationships between surface stiffness and roughness, combined with the effects of fractal dimension. The experimental results, for a wide range of surfaces, showed that the measured contact stiffness depended very closely on surfaces' root mean squared (RMS) slope and their fractal dimension, with correlation coefficients of around 90%, whilst a relatively weak correlation coefficient of 57% was found between the contact stiffness and RMS roughness.
Eighth International Symposium on Laser Metrology, 2005
Forming Limit Diagrams (FLD"s) can be defined by the criteria of either diffuse or local... more Forming Limit Diagrams (FLD"s) can be defined by the criteria of either diffuse or localized necks. We used Electronic Speckle Pattern Interferometry (ESPI) in commercial 1100 aluminum sheet metals annealed at 400°C to determine the strains at which both types of neck started in uniaxial tension (U) and in quasi plane strain tension (PS) tests. In biaxial (B) loading we
Journal of Metastable and Nanocrystalline Materials, 2004
X-ray diffraction using synchrotron radiation and instrumented indentation experiments has been c... more X-ray diffraction using synchrotron radiation and instrumented indentation experiments has been carried out to track free volume changes and local reodering following plastic straining by indentation below the glass transition temperature Tg in the Zr 60 Ni 10 Cu 20 Al 10 , Zr 65 Ni 10 Cu 15 Al 10 and Zr 65 Ni 10 Cu 7.5 Al 7.5 Pd 10 metallic glass forming systems. A quantitative diffraction l ine profiles modifications are observed during scanning strained and unstrained zones of the same specimen. We have found that the first diffractogram maximum intensity in transmission and the average inter-atomic spacing position are significantly affected in the overlapping shear bands around impressions. The surface uplift of the pile-up around indents has been assessed using a profilometer. It is shown that the inhomogeneous deformation results in an inhomogeneous distribution of free volume concentration. Substantial plastic deformation is determined form hysteresis loops recorded during nanoindentation experiments. While the ratio of the dissipated energy to total indentation work is quite similar for Zr-based metallic glasses, continuous stiffness measurements showed an appreciable difference in the evolution of the elastic modulus and hardness as function of penetration depth.
Experimental Analysis of Nano and Engineering Materials and Structures, 2007
... Guillaume Montay1, Bruno Guelorget1, Ignacio Lira2, Marie Tourneix1, Manuel François1 and Cri... more ... Guillaume Montay1, Bruno Guelorget1, Ignacio Lira2, Marie Tourneix1, Manuel François1 and Cristián Vial-Edwards2 1Université de Technologie de Troyes, Laboratoire des ... In it, an initially flat specimen is placed between a matrix and a blank holder, and hydraulic pressure is ...
Fringe 2005, 2006
ABSTRACT In this paper, an original application of ESPI in materials engineering has been describ... more ABSTRACT In this paper, an original application of ESPI in materials engineering has been described. The technique was used to analyze a bulge test in order to study strain localization by following the strain rate progress. Results show that ESPI allows detecting clearly the two stages of localization, namely, the diffuse and localized necks. Using this technique, forming limit diagrams can thus be established accurately.
WAGNER:SHOT PEENING O-BK, 2003
Experimental conditions on shot peening and residual stress measurement are shown on and respecti... more Experimental conditions on shot peening and residual stress measurement are shown on and respectively.
This paper describes influence of factors such as particle size (0.55-2.2 mm), particle velocity ... more This paper describes influence of factors such as particle size (0.55-2.2 mm), particle velocity (15-35 mls) and work hardness on surface integrity. Hardness, residual stress and crystal transformation of areas affected by shot peening or grit blasting are examined. In order to clarify the influences of those factors on the surface integrity, a medium carbon steel (C:0.45%, 180HV) and an austenitic stainless steel (SUS304, 210HV) were peened by a centrifugal type peening machine using cast steel particles (650-800HV). The following results were obtained: (1) Shot peening maximum hardness is lower while depth of work-hardened layer is thicker. (2) Compressive residual stresses on the peened surface are larger than that of grit blasting. (3) Critical thickness of shot peening is about 50% thicker than that of grit blasting. (4)Strain-induced transformation happens with shot peening and grit blasting.