Regis Kubler

Regis Kubler
Ecole Nationale Supérieure d'Arts et Métiers | ENSAM

PhD

About

46
Publications
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402
Citations

Publications

Publications (46)
Article
Shot-peening is a mechanical surface treatment widely employed to enhance the fatigue life of metallic components by generating compressive residual stress fields below the surface. These fields are mainly impacted by the selection of the process parameters. The aim of this work is to propose a hybrid approach to conduct two predictive models: seco...
Article
Full-text available
In materials science, the microstructures of materials are generally characterized by 2D observation (e.g. electron microscopy). For polycrystalline materials, such as crystalline rocks or ceramics, those observations can be used to measure the grain size distribution. However, the fact that grain sizes are measured in planar cuts introduces a stat...
Chapter
In this study, the residual stresses in the laminated polymer-matrix composite sample with a configuration of [04/904]s were measured and investigated using the incremental hole-drilling and slitting methods combined with the digital image correlation (DIC) technique. By averaging the values of strain obtained by the DIC technique in the location o...
Article
Full-text available
In order to perform Finite Element Analysis (FEA) on a polycrystal, one needs to first generate a mesh based on either EBSD or reconstructed grains. In this mesh, the Grain Boundaries (GBs) must be accurately described since they play an important role in the overall behaviour of aggregates. The proposed software, named MTEX2Gmsh, works regardless...
Article
Background The slitting method is a widely used destructive technique for the determination of residual stresses. Because of the rich data content of the full-field methods, optical techniques such as digital image correlation (DIC) are replacing strain gages for surface measurements.Objective The objective of the current paper is to overcome the d...
Article
Full-text available
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...
Article
Full-text available
The estimation of the grain size in granular materials is usually performed by 2Dobservations. Unfolding the grain size distribution from apparent 2D sizes is commonly referred as the corpuscle problem. For spherical particles, the distribution of the apparent size can be related to that of the actual size thanks to the Wicksell’s equation. The Sal...
Conference Paper
Full-text available
Afin d'étudier le comportement d'un matériau cristallin à l'échelle de ses grains, des simulations Elé-ments Finis (EF) tenant compte des propriétés physiques de chacun d'eux peuvent être effectuées. Ces simulations doivent alors tenir compte des hétérogénéités entre phases, des anisotropies locales ainsi que des orientations cristallines locales....
Article
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This paper investigates the relevance of the representation of polycrystalline aggregates using Radical Voronoï Voronoï (RV) tessellation, computed from Random Close Packs (RCP) of spheres with radius distribution following a lognormal distribution. A continuous relationship between the distribution of sphere radii with that of RV cell volumes is p...
Article
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This study aims at the experimental and numerical analysis of TRIP780 steel after conventional shot peening. TRIP steels exhibit a multiphase microstructure with martensitic transformation of the retained austenite during shot peening. In-depth experimental analysis are carried out with microhardness and X-ray diffraction. Residual stresses profile...
Article
Full-text available
During conventional shot peening on metastable austenitic steels, martensitic transformation occurs in addition to plastic straining. In this work, the impact of a single spherical steel shot on a AISI 301LN steel was studied. The volume fraction of martensite, residual stresses in both phases were determined in the vicinity of the dent as a functi...
Conference Paper
Full-text available
Shot-peening is a common mechanical surface treatment used in automotive and aeronautical industries to enhance life duration of mechanical parts by introducing compressive residual stresses. TRIP 780 steel fatigue type specimens are shot-peened and loaded under cyclic bending. The martensite phase transformation and the evolution of residual stres...
Article
Full-text available
Manufacturing industries perform mechanical surface treatments like shot peening at the end of the manufacturing chain to protect important working parts. This treatment modifies the near surface of the treated part with the introduction of compressive residual stresses due to the repeated impacts of the shot. Then, the treated part exhibits, not o...
Conference Paper
Full-text available
Shot peening is a process commonly used in industry to increase the life duration of mechanical and structural parts. This study presents the development of a constitutive law for steels with austenite-martensite phase transformation under thermomechanical loading and applied to shot peening. An elastoplastic material constitutive law with kinemati...
Conference Paper
Full-text available
Shot peening is a process commonly used in industry to increase the life duration of mechanical and structural parts. This study presents the development of a constitutive law for steels with austenite-martensite phase transformation under thermomechanical loading and applied to shot peening. An elastoplastic material constitutive law with kinemati...
Article
Full-text available
Le grenaillage de précontrainte a pour but d’augmenter la durée de vie des matériaux traités en introduisant des contraintes résiduelles de compression. Cette étude porte sur la modélisation de la tenue en fatigue d’aciers grenaillés et plus particulièrement d’aciers à transformation austénite-martensite sous sollicitation. L’approche utilise la de...
Article
A model reproducing strain softening behavior in ceramic materials is proposed. This model is base on a critical treatment of previous mechanical experimental results, mainly on uranium dioxide. The main hypothesis is that the strain softening phenomenon is related to an ageing process, where some point defects move towards the dislocations and mod...
Article
Low velocity perforation of aeronautical aluminium alloy sheets 2024 T3 is studied in this paper. After a literature review on recent experiments and models of plate’s perforation, experimental results for 2 thicknesses (2 mm and 4 mm) of plates are presented. Perforation tests are performed with an instrumented drop test. The striker has a large d...
Article
Full-text available
Low velocity perforation of an aeronautical aluminum alloy sheet 2024 T3 subjected to impact is studied in this paper. The main objective is to compare experimental results and simulations by analysis of the failure. The perforation test is made with an instrumented 3 meter drop test. The striker has a large diameter (45 mm) and a conical shape. Sh...
Article
Full-text available
During a manufacturing process, the ultrasonic shot peening (USP) technique can be used as the final surface treatment. The aim of this operation is to introduce surface compressive residual stresses in order to prevent crack propagation advancement. Although the numerical simulation method is able to predict the level of residual stresses in a pee...
Article
Full-text available
Development and evolution of compressive residual stress during nitriding treatment are studied. A model carbon iron-based alloy Fe-3wt.%Cr-0.35wt.%C was nitrided in gas at 550 °C for different times. Microstructural investigation indicated an influence of the transformation and the associated carbon diffusion on the in-situ relaxation of residual...
Article
Full-text available
A new semi-phenomenological model is developed based on a mean-field description of the TRIP behavior for the simulation of multiaxial loads. This model intends to reduce the number of internal variables of crystalline models that cannot be used for the moment in metal forming simulations. Starting from local and crystallographic approaches, the me...
Article
Full-text available
Nitriding is a well-established thermochemical surface treatment of carbon micro-alloyed steels aiming enhancing surface properties such as fatigue, wear and corrosion resistances. The idea is taking benefits from the high hardening level due to a fine nitride precipitation and also the compressive residual stress state. Due to some complex interac...
Article
Full-text available
This experimental study focuses on the influence of shot peening on parts initially treated by carburizing or carbonitriding. Experimental investigations have been carried out: optical observations of the microstructures, in-depth hardness measurement, X-ray diffraction analysis of residual stresses. A comparison is made between the carburizing ana...
Article
Full-text available
The main purpose of car manufacturers is to design parts which are light and at the same time very resistant to fatigue efforts. Surface treatments are effective means to deal with this compromise. They bring surface hardness and introduce compressive residual stresses. This experimental study focuses on the influence of shot peening on parts initi...
Article
This study presents 3D finite element (FE) simulations of the representative geometry of the shot peening process. As a preamble, a single shot simulation of a spherical particle is extensively analyzed in order to capture the effect of process parameters (velocity, size, shooting angle) on the plastic strain, residual stress profile and surface...
Article
Full-text available
Cette étude présente les capacités d’une modélisation de la nitruration, procédé thermochimique destiné à améliorer la tenue en service des pièces mécaniques. La formation d’un gradient de microstructure accompagné d’une variation de volume génère un gradient de contraintes résiduelles. Le modèle se base sur une étape de diffusion / précipitation d...
Article
Full-text available
UMo-Al specimens are analyzed using X-ray diffraction techniques. One specimen was partially irradiated using a heavy ion beam I-127. Another specimen was thermally annealed 2h at 400 degrees C. Those treatments result in the formation of an interaction layer between UMo particles and Al matrix. UMo, Al and UAl3 phases are identified in the treated...
Article
Phase transformations during nitriding of a ternary carbon iron-based alloy Fe–3%Cr–0.345%C were studied, aiming for a better understanding of residual stresses generation and evolution. The relationship between the precipitation of Cr7C3 carbides and CrN nitrides, the induced volume change and the mechanical properties were investigated at three d...
Article
A semi-phenomenological model is developed based on a mean-field description of the TRIP behaviour for the simulation of metal forming processes [1]. Within the metastable austenitic phase exhibiting martensitic transformation, a mean field approach is introduced at the phase level with the concept of Mean Instantaneous Transformation Strain (MITS)...
Article
Full-text available
This work deals with the development of residual stresses during nitriding of steels. The main features of a chemico-thermo-mechanical model of nitriding are presented. A micro-macro approach is applied based on volume change computation in agreements with thermochemical modifications. Results are correlated with the characterization of a ternary F...
Conference Paper
Nitriding is a well-established thermo-chemical surface treatment of carbon micro-alloyed steels aiming better surface properties such as fatigue, wear and corrosion resistances. The idea is taking benefits from the high hardening level due to the fine nitride precipitation and also the compressive residual stress state. Relaxation of residual stre...
Article
Several materials exhibit a transformation from austenite to martensite during a thermomechanical loading. This phase transformation is responsible for remarkable mechanical properties such as the superelasticity in shape memory alloys (SMA) or the excellent compromise strength/ductility in TRIP-steels (TRansformation Induced Plasticity). To optimi...
Article
The mechanical behaviour of TRIP assisted steels is investigated through two modelling approaches (micromechanical and more phenomenological). Main results are given for different steel grades and loading paths. A description of the deformation mechanisms per phase is used to analyse the stress partitioning. For the semi phenomenological model, the...
Article
A modeling of the evolution of austenite texture is presented in case of phase transformation in 304 AISI steel occurring during a tensile test at – 6°C. The computed textures agree well with those measured experimentally by X-ray diffraction. X-ray diffraction also enables to analyze stress distribution in both phases of this steel. First trend sh...
Article
During the martensitic transformation in elastic-plastic materials, the local transformation strain as well as the plastic flow inside austenite are strongly related with the crystallographic orientation of the austenitic lattice. Two mechanisms involved in these materials, i.e., plasticity by dislocation motion and martensitic phase formation are...
Article
Tensile tests performed on unstable austenitic material lead to formation of martensite. Therefore, plasticity and transformation occur at the same time leading to inelastic strain and consequently internal stresses. The present work focuses on the stress distribution in each phase of a two-phase material with an evolving microstructure. Experiment...
Article
L’opération de grenaillage de précontrainte est un traitement mécanique de surface destiné à améliorer la tenue mécanique d’une pièce métallique : par durcissement superficiel et par introduction des contraintes résiduelles de compression en sous-couche. Cette étude numérique a pour but de mieux comprendre le procédé par le développement d’un modèl...

Projects

Projects (4)
Project
Matlab toolbox for generating mesh from EBSD data. It converts data from the well-known MTEX toolbox into Gmsh-readable files. See the dedicated website for examples and details : https://doriandepriester.github.io/MTEX2Gmsh/
Project
This projects aims at characterizing and predicting the residual mechanical fields due to the accommodation of an incompatble source.
Project
We aim at modeling the behavior of materials and structures at different length scales.