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Introduction
Publications
Publications (40)
The conventional air pressure shot peening process consists of multiple impacts of particles propelled with pressurized air through a nozzle at the surface of mechanical components. An experimental study of the flow of particles exiting the nozzle was conducted. A high speed camera was used for image acquisition of the particle flow. This particle...
Cette étude propose une méthodologie expérimentale afin d’identifier les propriétés mécanique élastiques d’anneaux supraconducteurs. Des essais de traction diamétrale associés à une technique de mesure champs de déplacements ont été effectués sur des échantillons. Les champs de déformations ont ensuite été obtenus à partir des champs de déplacement...
Ce travail propose d’étudier une procédure alternative pour lisser puis dériver des mesures de champs de déplacement expérimentaux pour obtenir des champs de déformations. Celle-ci, la méthode des moindres carrés pénalisés, repose sur le calcul d’un compromis entre la fidélité aux données brutes et la nature lisse des données reconstruites. Pour ca...
This work proposes an alternative procedure to smooth and differentiate experimental full-field displacement measurements to get strain fields. This one, the penalized least squares method, relies on the balance between the fidelity to original raw data and the smoothness of the reconstructed ones. To characterize its performance, a comparative stu...
This study deals with an experimental methodology developed in order to identify the elastic properties of superconducting ring-shaped windings, constituents of the main coil winding of a magnetic resonance imaging magnet (MRI).Mechanical tensile tests were conducted on real scale specimens associated to an optical full-field displacement measureme...
This work is aimed at exploring the performances of an alternative procedure to smooth and differentiate full-field displacement measurements. After recalling the strategies currently used by the experimental mechanics community, a short overview of the available smoothing algorithms is drawn up and the requirements that such an algorithm has to fu...
We report on the main results of a collaborative work devoted to the study of the uncertainties associated with Digital image correlation techniques (DIC). More specifically, the dependence of displacement measurement uncertainties with both image characteristics and DIC parameters is emphasised. A previous work [Bornert et al. (2009) Assessment of...
Optical full-field techniques have a great importance in modern experimental
mechanics. Even if they are reasonably spread among the university
laboratories, their diffusion in industrial companies remains very narrow for
several reasons, especially a lack of metrological performance assessment. A
full-field measurement can be characterized by its...
Friction stir welding induces a microstructural evolution and residual stresses that will influence the resulting mechanical properties. Friction stir welds produced from magnesium alloy hot rolled plates were studied. Electron back scattered diffraction was used to determine the texture evolution, residual stresses were analysed using X ray diffra...
AZ31 hot rolled magnesium alloy presents a strong basal texture. Using laser beam welding (LBW) as a joining process induces high temperature gradients leading to major texture changes.Electron back scattered diffraction (EBSD) was used to study the texture evolution, and tensile tests coupled with speckle interferometry were performed to understan...
One of the main problems in welding is the microstructural transformation within the area affected by the thermal history. The resulting heterogeneous microstructure within the weld nugget and the heat affected zones is often associated with changes in local material properties. The present work deals with the identification of material parameters...
Optical full-field techniques have a great importance in modern experimental mechanics. Even if they are reasonably spread among the university laboratories, their diffusion in industrial companies remains very weak for several reasons, especially a lack of metrological performance assessment. A full-field measurement can be characterized by its re...
This work deals with the study of the local onset of microplasticity in a steel specimen under tensile test through the use of a full-field strain measurement method at the micrometric scale. The kinematic measurements were performed by the so called grid method. In order to produce the gratings, direct interferential photolithography was used. The...
The microstructural study of hot rolled magnesium friction stir and laser beam welds revealed the presence of shear band features starting from the weld edge and propagating in the base metal. These shear bands present a highly twinned microstructure and strain localisation occurs preferentially in this region. This influences the resulting mechani...
This paper presents a methodology aimed at the identification of the mechanical behaviour of hyperelastic low density polymeric foams using digital image correlation and the Virtual Fields Method. First, a simple bending/shear test enables the identification of the elastic parameters at low strain levels. Then, a uniaxial compression test is perfor...
This paper deals with the identification of the mechanical behavior of low density polyurethane foam using digital image correlation (DIC) and the virtual fields method (VFM). First the so-called Iosipescu like bending/flexion tests in range of elastic deformation are presented, the elastic parameters will be extracted by a matlab toolbox called CA...
This paper deals with the identification of the mechanical behavior of low density polyurethane foam using digital image correlation (DIC) and the virtual fields method (VFM). First the so-called Iosipescu like bending/flexion tests in range of elastic deformation are presented, the elastic parameters will be extracted by a matlab toolbox called CA...
Optical methods have been developed to measure large strains. Two alternatives are presented: the first one uses a cross grating, obtained by an innovative manufacturing process and the second one uses a mark-tracking technique. The production of the grating is based on the deposit of a thin film through a master grid under vacuum. This creates sma...
This paper deals with the identification of elasto-plastic constitutive parameters from deformation fields measured over the
surface of thin flat specimens with the grid method. The approach for recovering the constitutive parameters is the virtual
fields method. A dedicated algorithm is used for deriving the distribution of the 2D stress component...
In order to extend the application range of the so-called “grid method” to the micron scale and thus quantitatively characterize the micromechanical behavior of metallic alloys, we report in this paper on the optimization of microscopic 2D gratings with pitches ranging from 1 to . After an overview of the state of the art on full-field kinematic me...
This work deals with the development of a full-field extensometric method at a micrometric scale in order to precisely identify the local features of a metallic alloy at the scale of the grain. The full-field method that has been chosen is the grid method that applies a spatial phase-shifting algorithm to a periodic pattern. To mark the sample, the...
This work deals with the development of a full-field extensometric method at a micro-metric scale in order to precisely identify the local features of a metallic alloy at the scale of the grains. The full-field method that has been chosen is the grid method that applies a spatial phase-shifting algorithm to a periodic pattern. To mark the sample, d...
This paper presents the use of a sensitivity study to find the best combinations of free length and fibre angle in an unnotched Iosipescu test processed with the virtual fields method. The sensitivity to noise coefficients arising from the special virtual fields procedure are used to build up a cost function. This function is aimed at balancing out...
This paper presents an experimental validation of the use of the virtual fields method to identify the elasto-plastic behaviour
of an iron specimen from full-field measurements with the grid method and a simple heterogeneous test configuration. The experimental
procedure is carefully detailed since it is of primary importance to obtain good identif...
The paper presents the use of an optimization routine in order to find the best combination of free length and fibre angle in an unnotched losipescu test processed with the virtual fields method. The sensitivity to noise coefficients arising from the special virtual fields procedure are used to build up a cost function aiming at balancing out the d...
In this work, a new micro-extensometric technique to study the local heterogeneities of strain fields in metallic alloys is introduced. It is based on the optical full-field measurement method called the grid method adapted to the micrometric scale. In the first part of the paper, the making of a periodic grating at the surface of the sample by dir...
This paper deals with the use of the virtual fields method to identify the elasto-plastic behaviour of a mild steel specimen from full-field measurements obtained with the grid method. Very convincing and encouraging results were obtained in a previous study using a dog-bone shaped specimen. This paper presents another study with a double-notched s...
Publié suite au congrès Advances in Experimental Mechanics IV
The mechanical behaviour of dry woven fabrics as composite reinforcements is investigated using optical strain measurements during pure shear tests performed on a picture frame device. This optical measurement technique has many advantages, including the absence of contact with the sample. A change in lens allows measurements at different scales, f...
This paper introduces a two-dimensional model for the response of the ground surface due to vibrations generated by a railway traffic. A semi-analytical wave propagation model is introduced which is subjected to a set of harmonic moving loads and based on a calculation method of the dynamic stiffness matrix of the ground. In order to model a comple...
A new development of holographic recording for strain field evaluation during a transient event is proposed. The suggested metrology is a method associating holographic recording with numerical analysis of grating deposed on the specimen surface. An holographic camera allowing the storage of 6 grating images is presented. This process is based on t...
This paper presents the study of the deformation of magnesium friction stir welds (FSW) and laser beam welds (LBW) using speckle interferometry (SI). A small in-house developed tensile stage is used in conjunction with a commercial SI system. The spatial resolution of displacement is about 16 microns. About 80 images were recorded to grasp the plas...
