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Papers by Henry Proudhon
This paper presents an experimental study of the fretting crack nucleation threshold, expressed i... more This paper presents an experimental study of the fretting crack nucleation threshold, expressed in terms of loading conditions, with a cylinder/plane contact. The studied material is a damage tolerant aluminium alloy widely used in the aerospace application. Since in industrial problems, the surface quality is often variable, the impact of a unidirectional roughness is investigated via varying the roughness of
Conference Proceedings of the Society for Experimental Mechanics Series, 2011
Synchrotron-radiation computed laminography (SRCL) allows for imaging at high resolution (~ 1 µm)... more Synchrotron-radiation computed laminography (SRCL) allows for imaging at high resolution (~ 1 µm) and in three dimensions objects that are thin (~ 1 mm) but extended laterally in two dimensions. This represents a major advantage over computed tomography in terms of loading conditions that can typically only investigate samples elongated in one direction. Here SRCL is used to observe ductile
Conference Proceedings of the Society for Experimental Mechanics Series, 2011
Cavitation in the semicrystalline polymer polyamide 6 has been studied in terms of 3D void morpho... more Cavitation in the semicrystalline polymer polyamide 6 has been studied in terms of 3D void morphology and distribution in the notched region of axisymmetric specimens using synchrotron radiation tomography at submicrometer resolution. Ex-situ (interrupted and unloaded) tests at different stages of straining reveal damage initiation in form of penny-shaped crazes at maximum load. An in-situ (under load) test confirms the damage morphology at maximum load. When a neck appears and extends within the notch, the penny-shaped crazes extend in height, resulting in a volume change. Final failure is seen to occur from the specimen interior via coalescence of several voids resulting in large cavities. The multiaxial stress state generated by the axisymmetric notch causes crazes/cracks that are larger in diameter than those occurring during necking of an initially smooth specimen. The distribution void volume fraction as a function of the radius is measured via image analysis, showing a damage maximum at the specimen center that decreases toward the specimen border. This distribution was found to be consistent with that of the stress triaxiality ratio.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
This paper presents recent results showing the ability of high resolution synchrotron X-ray micro... more This paper presents recent results showing the ability of high resolution synchrotron X-ray micro-tomography to image damage initiation and development during mechanical loading of structural metallic materials. First, the initiation, growth and coalescence of porosities in the bulk of two metal matrix composites have been imaged at different stages of a tensile test. Quantitative data on damage development has been obtained and related to the nature of the composite matrix. Second, three dimensional images of fatigue crack have been obtained in situ for two different Al alloys submitted to fretting and/or uniaxial in situ fatigue. The analysis of those images shows the strong interaction of the cracks with the local microstructure and provides unique experimental data for modelling the behaviour of such short cracks.
Proceedings of 10th World Congress on Computational Mechanics, 2014
Matériaux & Techniques, 2013
Polymer, 2014
ABSTRACT The individual morphology and size distribution of nano-cavities in a necked tensile spe... more ABSTRACT The individual morphology and size distribution of nano-cavities in a necked tensile specimen made of semicrystalline high-density polyethylene (HOPE) have been observed and quantified in three dimensions using magnified synchrotron radiation holotomography. Here, using a voxel size of 59.7 nm, permanent voids in the unloaded state after yielding are observed that can only be assessed in averaged manner at finer length scales using small angle X-ray scattering (SAXS) techniques. Observation of the same sample using typical synchrotron radiation tomography with micron resolution is also given highlighting the novel opportunities arising with magnified synchrotron radiation holotomography in comparison. Two populations of voids elongated in loading direction are observed: A population of large cavities that has nucleated around inclusions and a population of small cavities. All cavities are equiaxed in radial directions and elongated in loading direction which is consistent with SAXS findings of other studies. Void volume fraction, void size distributions and characteristic dimensions of the voids are assessed using 3D image analysis.
Materials Science Forum, 2007
Combining the principles of x-ray imaging and diffraction techniques, it has recently become poss... more Combining the principles of x-ray imaging and diffraction techniques, it has recently become possible to map the 3D grain microstructure in a range of polycrystalline materials. Associating this 3D orientation mapping with conventional attenuation and/or phase contrast tomography yields a non-destructive characterization technique, enabling time-lapse observation of dynamic processes in the bulk of structural materials. The capabilities and limitations., as well as future perspectives of this new characterization approach will be discussed and illustrated on selected application examples.
This paper presents an experimental study of the fretting crack nucleation threshold, expressed i... more This paper presents an experimental study of the fretting crack nucleation threshold, expressed in terms of loading conditions, with a cylinder/plane contact. The studied material is a damage tolerant aluminium alloy widely used in the aerospace application. Since in industrial problems, the surface quality is often variable, the impact of a unidirectional roughness is investigated via varying the roughness of
Conference Proceedings of the Society for Experimental Mechanics Series, 2011
Synchrotron-radiation computed laminography (SRCL) allows for imaging at high resolution (~ 1 µm)... more Synchrotron-radiation computed laminography (SRCL) allows for imaging at high resolution (~ 1 µm) and in three dimensions objects that are thin (~ 1 mm) but extended laterally in two dimensions. This represents a major advantage over computed tomography in terms of loading conditions that can typically only investigate samples elongated in one direction. Here SRCL is used to observe ductile
Conference Proceedings of the Society for Experimental Mechanics Series, 2011
Cavitation in the semicrystalline polymer polyamide 6 has been studied in terms of 3D void morpho... more Cavitation in the semicrystalline polymer polyamide 6 has been studied in terms of 3D void morphology and distribution in the notched region of axisymmetric specimens using synchrotron radiation tomography at submicrometer resolution. Ex-situ (interrupted and unloaded) tests at different stages of straining reveal damage initiation in form of penny-shaped crazes at maximum load. An in-situ (under load) test confirms the damage morphology at maximum load. When a neck appears and extends within the notch, the penny-shaped crazes extend in height, resulting in a volume change. Final failure is seen to occur from the specimen interior via coalescence of several voids resulting in large cavities. The multiaxial stress state generated by the axisymmetric notch causes crazes/cracks that are larger in diameter than those occurring during necking of an initially smooth specimen. The distribution void volume fraction as a function of the radius is measured via image analysis, showing a damage maximum at the specimen center that decreases toward the specimen border. This distribution was found to be consistent with that of the stress triaxiality ratio.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms
This paper presents recent results showing the ability of high resolution synchrotron X-ray micro... more This paper presents recent results showing the ability of high resolution synchrotron X-ray micro-tomography to image damage initiation and development during mechanical loading of structural metallic materials. First, the initiation, growth and coalescence of porosities in the bulk of two metal matrix composites have been imaged at different stages of a tensile test. Quantitative data on damage development has been obtained and related to the nature of the composite matrix. Second, three dimensional images of fatigue crack have been obtained in situ for two different Al alloys submitted to fretting and/or uniaxial in situ fatigue. The analysis of those images shows the strong interaction of the cracks with the local microstructure and provides unique experimental data for modelling the behaviour of such short cracks.
Proceedings of 10th World Congress on Computational Mechanics, 2014
Matériaux & Techniques, 2013
Polymer, 2014
ABSTRACT The individual morphology and size distribution of nano-cavities in a necked tensile spe... more ABSTRACT The individual morphology and size distribution of nano-cavities in a necked tensile specimen made of semicrystalline high-density polyethylene (HOPE) have been observed and quantified in three dimensions using magnified synchrotron radiation holotomography. Here, using a voxel size of 59.7 nm, permanent voids in the unloaded state after yielding are observed that can only be assessed in averaged manner at finer length scales using small angle X-ray scattering (SAXS) techniques. Observation of the same sample using typical synchrotron radiation tomography with micron resolution is also given highlighting the novel opportunities arising with magnified synchrotron radiation holotomography in comparison. Two populations of voids elongated in loading direction are observed: A population of large cavities that has nucleated around inclusions and a population of small cavities. All cavities are equiaxed in radial directions and elongated in loading direction which is consistent with SAXS findings of other studies. Void volume fraction, void size distributions and characteristic dimensions of the voids are assessed using 3D image analysis.
Materials Science Forum, 2007
Combining the principles of x-ray imaging and diffraction techniques, it has recently become poss... more Combining the principles of x-ray imaging and diffraction techniques, it has recently become possible to map the 3D grain microstructure in a range of polycrystalline materials. Associating this 3D orientation mapping with conventional attenuation and/or phase contrast tomography yields a non-destructive characterization technique, enabling time-lapse observation of dynamic processes in the bulk of structural materials. The capabilities and limitations., as well as future perspectives of this new characterization approach will be discussed and illustrated on selected application examples.