Guillaume Kermouche

Guillaume Kermouche
Mines Saint-Etienne | ENSM-SE · Materials Sciences and Structures

PhD

About

188
Publications
51,018
Reads
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1,869
Citations
Citations since 2016
83 Research Items
1308 Citations
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2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300
Introduction
My work deals with the analysis of the mechanical response of surfaces under contact loadings and the consequences of Surface Mechanical Treatments on surface integrity (residual stress, microstructure evolution). I develop methods to extract the mechanical properties at small scales with the help of nano or micromechanical experiments. I also investigate the fragmentation/recristallisation phenomena in relation with SMT (peening, burnishing, attrition).
Additional affiliations
January 2015 - present
Mines Saint-Etienne
Position
  • Head of Department
September 2012 - January 2015
Mines Saint-Etienne
Position
  • Professor (Full)

Publications

Publications (188)
Article
In new high definition lighting modules, assembling more than thousand elements (pixels) with a single mm-sized motherboard is achieved by reflow soldering. Lead-free solders may constitute a weak part of electronic components and LED assemblies. During reflow, the distance between pixels and motherboard controls the solder heights (10 μm). After a...
Article
Slow strain rate tensile tests under hydrogen cathodic charging are conducted on 17-4 PH steel with two surface conditions: mirror polished and ball-burnished. In both cases, significant subcritical cracking initiating at the surface is observed leading to considerable reduction in elongation to fracture. However, ball-burnished specimens show bett...
Article
One of the R&D focus in the European fusion energy program is to establish a physical and technological basis for reliable power exhaust during entire operational situations of a DEMOstrational power plant. Following the design adopted for ITER, the baseline Plasma Facing Component for DEMO divertor is made of tungsten as armor material. The tungst...
Conference Paper
Most of ductile metals can be deposited by cold spray (CS). For brittle ceramic, such solid-state deposition process is still questionable, but some recent work on Ti02 or hydroxyapatite powders have shown that micrometric ceramic powder could be deposited by CS. In this work, it is claimed that the nature and the porous architecture of a ceramic p...
Article
Full-text available
In thermonuclear fusion devices, tungsten, implemented as armour material of plasma facing components, is in direct contact with the plasma. Due to high heat flux (20 MW/m\(^{2}\) ), a premature cracking can be observed in relation with the loss of tungsten mechanical properties. It is usually attributed to two competing restoration processes: reco...
Article
Full-text available
The ability to predict the micro-scale strength and plasticity of fused-silica micro-components is crucial as their miniaturization and applications in harsh environments advance. This study focusses on the micro-mechanical behavior of fused silica micropillars at high temperatures and variable strain rates. 160 micropillars with a diameter of 1.6...
Article
A new measurement technique based on microshear has been developed. This technique, inspired from a macroscopic test called the Shear Compression Specimen, was developed at the micron scale by making the specimen using FIB technology, and by compressing it using an in situ SEM nano-indenter. The experimental tests applied on the fused silica show a...
Article
New LED technologies & modules allow glare-free automotive lighting. Valeo solutions include the first high-definition LED lighting system. These LEDs technology endure extreme tests conditions in form of thermal shocks or mechanical vibrations to insure reliability under the lifetime of automotive usage. Strict regulations require lead-free solder...
Article
Full-text available
During H-mode plasma in ITER, type-I Edge Localized Modes can occur naturally leading to transient heat load (<10 GW m⁻²) on the tungsten divertor. Such high heat fluxes might therefore induce annealing effects, such as recovery and recrystallization, or even lead to surface melting and deterioration (e.g. cracks) of the plasma-facing components. T...
Article
In this work, the interest was focused on the study of clogging and durability of soils clogged using the Biosealing® process. During this process, bacteria initially present in the soil are fed with an appropriate nutritive solution. The aim is to provoke phenomena resulting in a sharp permeability drop. The durability tests objective was to measu...
Article
This work reports the use of a new high-temperature scanning indentation (HTSI) technique to monitor the physical changes occurring in thin-film metallic glasses (TFMGs) in situ during heat treatment at the local scale. Using this technique, based on high-speed nanoindentation performed during thermal cycles, the entire mechanical evolution with te...
Article
Full-text available
Instrumented single-shot experiments provide crucial information of a material's response to impact events that can be used in shot-peening modelling. However, no authors successfully used such test for constitutive model identification and validation as existing test rig generally cannot provide an accurate determination of the shot trajectory in...
Article
Turning is a machining process extensively applied to produce revolution parts. Durability of these parts are known to depend on the turning process signature that is often referred as surface integrity. The surface integrity generated in a fillet radius has been barely studied in the literature so far, despite the well-known geometrical stress con...
Article
Full-text available
Ultrafast laser was recently used to modify the surface integrity and peen the surface region of aluminum based alloy 2024-T351 without a sacrificial layer prior to the process. We show that controllable laser parameters such as fluence and pulse duration have a significant influence on peening qualities, such as the compressive residual stress, ha...
Article
Full-text available
The thermonuclear fusion reaction between deuterium and tritium could become an alternative, sustainable and safe way to generate electricity in demand. Plasma facing components will ensure the mechanical integrity of the reactor internal walls and the heat extraction and must be compatible with the plasma operation to not compromise its exploitati...
Article
Full-text available
Shot peening of complex geometries can generate rolled edges which mechanical properties, compared to a flat shot peened specimen, are not well known. Electron BackScattered Diffraction (EBSD) analyses and nanoindentation tests were conducted to characterize the microstructural changes and hardening induced in the rolled edge compared to a referenc...
Article
Nowadays, fatigue life of engineering components is a major topic. In the literature, extensive works have been reported in order to assess the machining-induced surface integrity which is known to be a first-order parameter for the fatigue resistance. This paper lies in the framework of turning-induced residual stress prediction by presenting an u...
Article
A new technique, High-Temperature Scanning Indentation (HTSI), is proposed to investigate metallurgical evolution occurring during anisothermal heat treatments. This technique is based on the use of high-speed nanohardness measurements carried out during linear thermal ramping of the system with appropriate settings. A specific high-speed loading p...
Article
Full-text available
Measurement of recovery and recrystallization kinetics of tungsten at high temperature is a key issue for many applications, such as plasma facing units in the framework of thermonuclear fusion. These kinetics are mostly derived from Vickers hardness and EBSD measurements, which can lead to some inaccuracies due to the competition between recovery...
Article
The development of a divertor target for DEMO is of great importance, being able to sustain the harsh environment that is imposed on this component. To fulfill the loading requirements, different concepts were developed within the EUROfusion WPDIV project. The baseline concept is based on the ITER divertor target W-monoblock design. It is made of t...
Article
Estimating the lifetime of W-armoured divertor components is of great importance for ITER. During heat loading, one of the mechanisms inducing tungsten microstructure modification is recrystallization. As tungsten recrystallization induces a decrease of the mechanical properties, the knowledge of the recrystallization kinetics of the ITER tungsten...
Article
A Fe-0.02 wt%C, containing cementite particles, and a pure α-iron were subjected to unconstrained high-pressure torsion and their microstructural refinement with strain are examined by electron backscatter diffraction (EBSD) and transmission Kikuchi diffraction EBSD (TKD-EBSD), based on which the influence of second-phase particles on grain refinem...
Article
Full-text available
Microcompression tests were performed on single crystal copper micropillars at 10⁻² s⁻¹ and 10² s⁻¹ in the [100], [110] and [111] orientations, to provide inputs for crystal plasticity strain rate sensitive parameters inverse identification. The identification procedure used full pillar geometry finite element simulations. An identifiability indica...
Article
Full-text available
Over the past decades, constitutive relations have been developed to compute the mechanical response of silicate glasses at the continuum length scale. They are now reliable enough that we can calculate indentation induced stress and strain fields and examine the impact of material parameters on indentation response, and especially hardness, pile-u...
Article
SiO2 glass structure has been permanently modified by uniaxial compression. Within such a loading, the structure is supposed to be affected both by densification and shear flow. We propose to compare recovered silica samples with similar densities, initially deformed plastically under a hydrostatic compression or under a uniaxial compression. From...
Article
Full-text available
During the ferrite-to-austenite transformation, the accommodation of the volume misfit between ferrite and austenite induces strain localization in both phases. A detailed understanding of this mechanism is a necessary step towards the improvement of thermomechanical treatments of iron alloys. Full-field measurements of displacement during heating...
Article
The knowledge of material properties and their behavior at high temperatures is of crucial importance in many fields. For instance, annealing phenomena occurring during the thermomechanical processing of materials, such as recrystallization, have long been recognized as being both of scientific interest and technological importance. Different metho...
Article
An extensive study of the different methods able to measure material creep properties in indentation is proposed. A systematic comparison of the fast creep, long-term creep, constant strain rate and long-term relaxation tests is performed on amorphous selenium. Even though measured apparent activation energy and strain rate sensitivities are very s...
Article
A novel extrinsic measurement of the particle surface distribution in a carbon black filled elastomer via nanoindentation is developed. This method is based on the measurement of the contact stiffness obtained from the Continuous Stiffness Measurement (CSM) mode. The proposed tip-particle model is held by two main hypotheses: the particles do not d...
Article
Full-text available
Surface integrity induced by longitudinal turning has been widely investigated in the literature. On the contrary, few works have aimed at investigating the surface integrity induced during turning of geometric singularities such as fillet radii. This paper investigates the surface integrity generated while turning a fillet radius in a martensitic...
Article
Full-text available
Microstructure evolution and microindentation properties of dissimilar weld between Inconel 625 nickel based alloy and UNS S32205 Duplex Stainless Steel have been investigated in the current study. Samples in cross-section areas were prepared to investigate microstructure and micromechanical properties in different regions of weld using optical mic...
Poster
Full-text available
Shot-Peening (SP) is a surface mechanical treatment that consists in propelling hard particles, called shot, onto a ductile metallic surface at high velocity to induce subsurface residual compressive stresses. It is widely used in the industry to increase fatigue life and wear resistance of treated parts. Shot-peening induced macroscopic residual s...
Presentation
Full-text available
Shot-Peening (SP) is a surface mechanical treatment that consists in propelling hard particles, called shot, onto a ductile metallic surface at high velocity to induce subsurface residual compressive stresses. It is widely used in the industry to increase fatigue life and wear resistance of treated parts. Shot-peening induced macroscopic residual s...
Article
An experimental study is performed to assess the surface integrity of cold sprayed and laser cladded 17-4PH stainless steel deposits after turning and ball-burnishing. A special emphasis is given to near surface microstructure and residual stress distribution. It is shown that both cold spray and cladding deposits could be machined under cutting co...
Article
Full-text available
The allotropic phase change from ferrite to austenite represents a moment of massive interplay between the microstructural and mechanical states of iron. The difference of compacity between the two phases induces a microplastic accommodation in the material at grain scale. However, mechanical heterogeneities resulting from the transformation proces...
Article
In this work an influence of cold spray nozzle displacement parameters on the properties of copper-silicon carbide cold spray deposits is considered. In particular the influence of nozzle traverse speed and distance between deposited tracks on the coating porosity and behavior during compressive tests was analyzed. It was shown that cold spraying a...
Article
A new procedure is developed to measure strain rate sensitivity m and apparent activation volume V* using nanoindentation relaxation experiments. This procedure is based on the control of the dynamic contact stiffness as measured by the continuous stiffness measurement module (CSM). Load decrease is monitored while maintaining the contact stiffness...
Article
Understanding of recrystallization phenomenon is essential to apprehend damage process of tungsten armored plasma facing components and to optimize their use in tokamak environment. In ITER, plasma facing components will reach extreme surface temperature value up to 2000 °C. Up to now, recrystallization kinetics of ITER tungsten grade were investig...
Article
A comparison of the long-term evolution of a femtosecond laser and the mechanical knurling texturing of aluminum surfaces is performed. Both the femtosecond laser and knurling textured surfaces present similar topographical parameters in the micrometer range. To compare both texturing approaches, long-term physico-chemical characterizations are per...
Article
For the development of a divertor for DEMO, the European WPDIV project is underway since 2014. The first phase of the project (2014–2016) aims to provide mock-ups adapted to DEMO operation requirements and the second phase aims to furnish mock-ups, with standardized geometry, which fulfill phase 1 requirements. Within the WPDIV project, several opt...
Article
Full-text available
Experimental determination of local residual stress fields beneath a spherical indent on a <001> copper single crystal revealed the presence of a significant tensile residual stress zone. This finding was adequately reproduced by Crystal Plasticity Finite Element simulations. Further simulations of one spherical indent on many other crystal orienta...
Article
For ITER divertor, plasma facing components are made with tungsten as armor material. In previous papers, it has been shown that plasma facing components are prone to crack, appearing in tungsten block during thermal cyclic heat loading. In order to predict component lifetime, a numerical simulation is proposed in this paper. With regard to previou...
Conference Paper
Full-text available
Ultrasonic wave propagation is widely used in non-destructive techniques or medical imaging to inspect solid structures, materials or human body. Ultrasonic arrays are mostly employed and consist in a single transducer that contains a number of individually connected elements. They can be efficiently combined to specific data acquisition processes...
Article
The trends in automotive industry are towards higher performance, improved reliability, reduced tolerances and more environmental friendly products. Wear resistance enhanced mechanical components exhibiting lower friction help achieving this major challenge. Diamond-Like Carbon (DLC) deposited on mechanical components operating under lubricated con...
Conference Paper
An ultrasonic array is a group of transducers excited with a delay to non-destructively evaluate or detect small cracks and imperfections in a body or in and on the surface. Non-destructive testing using array transducer has become very popular due to its large scale industrial applications in crack, flaw detection. Although, not much work has been...
Article
Full-text available
Some mean-field models are currently available for discontinuous dynamic recrystallization (DDRX). They offer an affordable way to predict the variation of averages altered by DDRX as flow stress, grain size and recrystallized fraction. They predict also a grain-size distribution, but it appears unrealistic, at least if a deterministic equation gov...
Article
Full-text available
Static recrystallization kinetics, at 300 °C, of a hot rolled commercial purity aluminum alloy AA1050 has been investigated using high temperature nanoindentation. Annealing treatments were achieved inside a nanoindentation device to measure corresponding hot nanohardness versus time. Clear evidences of recrystallization phenomenon were deduced fro...
Article
Mechanical surface treatments based on repeated impacts are known to create a graded strengthening in-depth by the means of severe plastic deformation. However microstructural evolution mechanisms leading local progressive grain refinement and the resulting surface mechanical hardening are not yet fully understood. It is shown in this paper that mi...
Article
Full-text available
Tribofinishing is an ancient and widely used process in industry. However the preparation to reach this steady state is long and costly and the know-how is mainly based on the long experience of the providers (machine builder and abrasive media producer), whereas the literature to help end-users is very limited. Moreover is difficult to understand...
Article
Full-text available
The future DEMO divertor is currently under conceptual design within the European Consortium. In this regard, several concepts have been proposed and mock-ups have been fabricated to investigate their thermo-mechanical behaviour. Indeed, as a key plasma facing component, the divertor will have to withstand extreme thermal loads (up to 20 MW m⁻² dur...
Article
Full-text available
The divertor is the key in-vessel plasma-facing component being in charge of power exhaust and removal of impurity particles. In DEMO, divertor targets must survive an environment of high heat fluxes (~up to 20 MW m⁻² during slow transients) and neutron irradiation. One advanced concept for components in monoblock configuration concerns the inserti...
Article
The continuum scale description of the plasticity of silicate glasses is a difficult task. In addition to significant amount of densification, it has been shown that, depending upon composition, there is a more or less pronounced coupling of yield stress with pressure. Moreover, the scant experimental results make it difficult it build up reliable,...
Conference Paper
Full-text available
Cet article a pour objet de présenter une méthodologie permettant de discriminer les effets des traitements mécaniques de surfaces en termes de gradients de microstructure et de propriétés mécaniques. Celle-ci repose sur l’utilisation combinée de mesures EBSD et d’essais de compression de nano-piliers permettant de mesurer très localement les courb...