Philippe Bocher

• Doctor of Philosophy
• Professor (Full) at École de Technologie Supérieure

This paper aims to investigate the effectiveness of cutting fluid during the high-speed face-turning of superalloy Inconel 718 using chamfered whisker-reinforced ceramic inserts. It addresses this topic by providing a comprehensive understanding of the machinability of Inconel 718 under both dry and wet conditions through analytical friction modeli...

A numerical investigation on uniaxial compression tests is performed to highlight the heterogeneous nature of the deformation process. Resulting errors on the material behaviors are deduced from the obtained force versus displacement data with the assumption of homogeneous deformation. The numerical study considers a range of strain rates (from 0.0...

The heterogeneous nature of the uniaxial compression process is studied through a numerical investigation. It is known that friction causes a barrelling effect on the sample, resulting in a heterogeneous shape. This barrelling effect leads to a deviation between the actual stress/strain curve and the experimental stress/strain curve observed experi...

This research investigates the effect of various intercritical tempering in a 13Cr-4Ni stainless steel on the morphology, size, and γ-stabilizer elements enrichment of the retained austenite, i.e. the austenite retained at room temperature after intercritical heat treatments. A comparative microstructural and chemical composition study was conducte...

Free access ==> https://authors.elsevier.com/a/1f1wywevWJbrA ******************************************** The paper demonstrates how defects inherited from the deposition processes can severely impair the lifetime of MCrAlY coatings in service. The oxidation behavior of two NiCoCrAlY coatings was investigated at 1150 °C up to 500 h. The coatings h...

The purpose of this study is to expose data analysis techniques based on X-ray computed microtomography (XCT) for measuring the complex geometric characteristics of millimeter-sized specimens fabricated by additive manufacturing, and their modification induced by surface treatment. A set of Ti-6Al-4V struts was produced by Electron Beam Melting (EB...

In this work, the feasibility test of friction stir processing (FSP) of 1.5-mm-thick austenitic stainless steel cold spray coating deposited on 304L stainless steel substrate was performed using tungsten carbide tool. Applied FSP parameters (advance speed 50 mm/min, rotation speed 300 rpm, axial force 20 kN, tilt angle 1.5°) allowed to perform FSP...

Fracture behavior of the welded joints of 13% Cr‐4% Ni stainless steels deposited using multipass flux‐cored arc welding process was examined in both as‐welded and heat‐treated conditions, and JIc tests were performed. A crack starter notch was placed one millimeter far from the fusion line to evaluate the heat‐affected zone (HAZ). Unstable crack p...

The 3rd generation of aluminum–lithium (Al–Li) alloys provides a desirable combination of high mechanical properties and low density compared to their traditional counterparts, exempt of lithium. Therefore, providing a reliable joint between new and conventional aluminum alloys is crucial for making hybrid structures. The present study focuses on i...

In this work the feasibility test of friction stir processing (FSP) of 1.5 mm thick austenitic stainless steel cold spray coating deposited on 304L stainless steel substrate was performed using tungsten carbide tool. Applied FSP parameters (advance speed 50 mm/min, rotation speed 300 rpm, axial force 20 kN, tilt angle 1.5°) allowed to perform FSP t...

Synthèse des textures cristallines rencontrées dans les alliages d'aluminium. Collaboration entre l'École de technologie supérieure, le REGAL, AluQuébec et le CeAl.

Ductile rupture of 13% Cr-4% Ni martensitic stainless steels was examined during tension testing in order to better understand the role of second phase particles in these materials. SEM fracture surface examinations revealed that micro-voids were initiated from inclusions, and these inclusions were characterized from metallographic polished section...

This paper proposes representing and detecting manufacturing defects at the micrometre scale using deep convolutional neural networks. The information theoretic notion of entropy is used to quantify the information gain or mutual information of filters throughout the network, where the deepest network layers are generally shown to exhibit the highe...

Having environmental and economic advantages, flax fibers have been recognized as a potential replacement for glass fibers as reinforcement in epoxy composites for various applications. Its widening applications require employing failure criteria and analysis methods for engineering design, analysis, and optimization of this material. Among differe...

In this work, the microstructure and mechanical properties of an additively manufactured X3NiCoMoTi18-9-5 maraging steel were determined. Optical and electron microscopies revealed the formation of melt pool boundaries and epitaxial grain growth with cellular dendritic structures after the laser powder bed fusion (LPBF) process. The cooling rate is...

By comparing the behavior of 13%Cr–4Ni and 13%Cr–6Ni alloys, this paper investigated the effect of Ni and Mn enrichment on the amount, mechanical stability, and microstructure of reformed austenite. 4%Ni and 6%Ni–1.5%Mn weld multilayer deposits were made and heat treated to stabilize various amounts of austenite content at room temperature. The max...

This paper proposes representing and detecting manufacturing defects at the micrometer scale using deep convolutional neural networks. The information theoretic notion of entropy is used to quantify the information gain or mutual information of filters throughout the network, where the deepest network layers are generally shown to exhibit the highe...

Conventional machining especially hard turning is commonly used in aerospace industry to produce the final shape of cylindrical parts. However, the process generates damages and microstructural alterations on the surface and at the subsurface layer, in particular the cracking of hard carbides particles. The present paper focuses on investigating th...

In the aeronautical industry, many critical components are made of high-strength steels. These steels have high tensile strength but are sensitive to corrosion and to the hydrogen embrittlement phenomenon. This study examines how acoustic emission could be used to detect hydrogen embrittlement of high-strength steels and reduce the duration of the...

Although the effects of hard turning on surface integrity have been extensively studied over the past decades, the fatigue behavior of hard turned ultra-high strength steels is still not completely understood. This study investigated the influence of surface integrity characteristics generated by hard turning on the rotating bending fatigue life of...

This research is performed by 2D axis-symmetric finite element simulation based on the coupling of electromagnetic fields and heat transfer applied on 4340 Steel Specimen with flux concentrators heated by Induction Process. The model is built using COMSOL software based on an adequate formulation and taking into account the material properties an...

A method for simulating the distortions in friction stir welding induced by thermal deformation is proposed. It consist of a coupling between a transitional Rigid-ALE finite element approach, to calculate the transitional heat transfer directly from the kinematic parameters of the process, and a simple distortion model where calculated heat transfe...

The aim of the study is to determine the effect of each parameter involved in the induction heating process on the final temperature distribution and case depth dispersion of a spur gear placed between two other gears having identical shapes and acting as a flux concentrator using two different approaches. The purpose of flux concentrators is to ad...

Hard turning technology was proven effective in enhancing the surface finish and dimensional accuracy of hardened steel. For this reason, it is used for finishing operations in the manufacturing of some critical aircraft landing gear components where bulk material hardness exceeds 45 HRC such as 300M ultra-high-strength steel. Nonetheless, the sele...

The axial fatigue life of 300 M steel subjected to a high stress amplitude was investigated for 3 peening conditions. Peening-induced roughness, residual stresses and their relaxation during cyclic loading were quantified. B-basis analysis was employed to compare the peened and unpeened specimens' fatigue lives. It was observed that a competition b...

Ultrafine austenite-ferrite duplex medium Mn steels often show a discontinuous yielding phenomenon, which is not commonly observed in other composite-like multiphase materials. The underlying dislocation-based mechanisms are not understood. Here we show that medium Mn steels with an austenite matrix (austenite fraction ∼65 vol.%) can exhibit pronou...

Ultrafine austenite-ferrite duplex medium Mn steels often show a discontinuous yielding phenomenon, which is not commonly observed in other composite-like multiphase materials. The underlying dislocation-based mechanisms are not understood. Here we show that medium Mn steels with an austenite matrix (austenite fraction ~65 vol%) can exhibit pronoun...

X-ray diffraction (XRD) is a widely used technique to evaluate residual stresses in crystalline materials. Several XRD measurement methods are available. (i) The sin²ψ method, a multiple-exposure technique, uses linear detectors to capture intercepts of the Debye–Scherrer rings, losing the major portion of the diffracting signal. (ii) The cosα meth...

An original approach is introduced to discriminate the effects of residual stress and surface roughness on turned Inconel 718 alloy parts. This could be used for assessing or studying the performance of these specimens during fatigue tests. This method consists of building surface integrity maps in terms of surface roughness parameters and residual...

An adequate induction heat treatment operation should always identify, previously, the probable temperature distribution and hardness profile behavior in specific regions of the treated component according to heating process parameters. This paper presents an analysis of the effects of some geometrical factor related to the component and the coil a...

A new figures has been provided which are necessary to increase the coherence and the quality of the illustrations. The original article has been corrected.

Free access ==> https://authors.elsevier.com/a/1Yne3_UwYsEKgM ********************************************************************* High-resolution digital image correlation (HR-DIC) techniques have become essential in material mechanics to assess strain measurements at the scale of the elementary mechanisms responsible of the deformation in polyc...

Comparable microstructures and mechanical properties are obtained for the different AA2139-T8/AA7020-T651 joints welded in the range 600–1000 rev. min⁠−1 / 250–550 mm.min⁠−1 as rotation and advance speeds. Joints exhibit tensile properties as good as 77%–79% of the yield strength and 88%–96% of the ultimate tensile strength of the AA7020 base mater...

A superalloy component heat treatment method using controlled induction heat treatment. The method being adapted to controllably generate a coarse grain microstructure region within the component from a fine grain microstructure metallic component. The method further being adapted to controllably form precipitates within the desired region in order...

The role of twin boundaries (TBs) in the dynamic recrystallization (DRX) of Ni-30Cu (Monel400) was investigated through hot compression tests in the temperature interval of 750–1150 °C and strain rate of 0.01 s⁻¹. Electron Back Scattered Diffraction (EBSD) analysis showed that DRX at 750 and 950 °C was limited to bulging and sparse nucleation on ra...

In order to fully exploit the benefits of shot peening process in terms of fatigue performance, the proper choice of peening conditions is indispensable, which is largely material specific. In this study, the influence of 3 different peening conditions on the axial fatigue life of high strength 300M steel (modified AISI 4340) was investigated in th...

The fast evolving temperature fields at the surface of induction-heated parts were measured by a contactless, optical method based on temperature-sensitive lacquers recorded with a high-speed imaging system. The positions of specific isotherms over time were precisely measured by image analysis. A 4340 steel cylinder and two spur gears of the same...

******* Free Download: https://authors.elsevier.com/c/1XtgaWK0QG2hP ******* Fatigue lives of as-polished and shot peened specimens were predicted using the original Navarro-Rios model (monotonic damage model) and a more recent version of the same model (cyclic damage model). Crack closure, residual stress relaxation, cold work and cyclic yield stre...

Free download ==> https://authors.elsevier.com/a/1XGlnWK0QG2a5 ********************************************************* The fatigue properties of gas metal arc welded and friction stir welded assemblies made of aluminum alloy AA6061-T6 structural extrusions were examined. The mechanical performances of welded joints were obtained using uniaxial t...

Different tool geometries were used to investigate the joining of aluminum alloys (AA2198 to AA2024) by friction stir welding (FSW). Three shoulder profiles (flat, raised spiral, and raised fan) and five different pin profiles (cone, half threaded cylindrical, straight cylindrical, tapered cylindrical and square) were selected. Preliminary investig...

The high-cycle fatigue performance and crack growth pattern of transient liquid phase-brazed joints in a nickel-based superalloy Inconel 625 were studied. Assemblies with different geometries and types of overlaps were vacuum-brazed using the brazing paste Palnicro-36M in conditions such as to generate eutectic-free joints. This optimal microstruct...

Shot peening is commonly used in the aerospace industry to improve mechanical components fatigue life. It introduces compressive residual stresses and cold work at the surface which tend to close short fatigue cracks and delay their propagation, respectively. However, shot peening also creates surface irregularities that can be detrimental to fatig...

The effects of surface roughness parameters and residual stresses induced by finish turning on fatigue life and crack propagation behavior of Inconel 718 super-alloy are investigated. A criterion serving as a good indicator of surface quality is also discovered. This is carried out for some specific turning conditions in order to control surface ch...

In metal cutting processes, the work materials undergo intense deformation process, involving large strain (up to 10 and more), high strain rate (up to 10^6 s–1), high stress (ultimate stress), and elevated temperature (up to 90% the melting temperature). However, there is no devoted experimental setup for describing the flow stress relevant to pra...

The machining of nickel-based superalloys used for aeronautical applications generates damage, deformation, and carbide cracking in machined surface and subsurface layers as a result of microstructural heterogeneities which reduce the fatigue life of aeronautic machined components. In this study, Inconel 718 was hard turned with a carbide tool usin...

Friction stir welding of dissimilar heat treatable 2139-T8 and 7020-T651 aluminum alloys was investigated in a large operating window of industrials welding parameters. Detailed microstructural and local mechanical characterizations have shown that despite consistency in the macroscopic tensile behavior of the different processed joints, local disc...

Efforts to better understand hydraulic turbine fatigue have recently been undertaken to improve their long-term reliability. Part of these efforts has been focused on modelling the physical phenomenon. In this context, an approach based on the Kitagawa-Takahashi diagram has been developed and is now used to determine a fatigue cracking risk index f...

In order to quantify the effects of shot peening on the processed part, surface and in-depth residual stresses are measured. The X-ray diffraction technique is widely used in industries and laboratories. For this purpose, X-ray Elastic Constants (XEC) extracted from the literature are frequently used; or they are calculated from the known macroscop...

Independent research studies have shown notable dissimilarity in the machining behaviour of aluminum alloys AA6061−T6 and AA7075−T651 commonly used in automotive and aeronautical applications. The present work attempts to investigate this dissimilarity based on experimental and numerical data with a focus on chip formation and generated residual st...

Dry machining is one of the reliable eco-friendly techniques since it enables avoiding the use of harmful/expensive cutting fluids, reducing part costs, and increasing productivity. This study attempts to optimize the dry peripheral milling conditions with regard to the surface finish and residual stress (RS) of machined aeronautical Al–Zn–Mg–Cu al...

A methodology is presented for the use of the oxide scale that develops in polycrystalline Ni-base superalloys at service temperature, as a speckle pattern for μm-scale resolution strain measurements. Quantitative assessment of the heterogeneous strain field at the grain scale is performed by high-resolution SEM digital image correlation under mono...

The correlation between the strain-induced martensite transformation (SIMT) and the Portevin-Le Chatelier (PLC) effect during tensile testing of a ferrite-austenite duplex medium manganese (Mn) steel was investigated in this study. A discontinuous SIMT phenomenon (D-SIMT) was observed in the steel by in situ magnetic induction measurements compleme...

High–speed machining (HSM) is widely used in the manufacturing of monolithic aluminum components for automotive and aeronautical industries. However, previous research studies on HSM of high strength aluminum alloys have shown that serrated and/or elemental chips can form at critical cutting conditions, impacting the machining stability and final p...

This paper proposes an analytical cutting forces model based on an extension of the Oxley's machining theory (OMT) to high-speed machining of ductile and hard metals. In this model, the materials' behavior was modeled using the Marusich's constitutive equation (MCE). Furthermore, The OMT was modified to be able to capture the effects of the cutting...

Shot peening is a cold-working process widely used to form and enhance the fatigue life of metallic components. The process consists of projecting high-velocity particles onto a metallic surface. This study introduces a new, and experimentally validated, sequentially coupled Discrete Element Model (DEM) - Finite Element Model (FEM) to predict the p...

In industry, the sliding mechanical systems are subject to friction and wear phenomena. These phenomena can be the origin of a reduction of the efficiency of the mechanical system even to be responsible for its incapacity. Generally, the materials of the parts which are moving relative (tribological couple) of these systems are low alloy steels and...

The purpose of this work was to investigate tensile and fatigue behaviors of Inconel 625 superalloy brazed joints after transient liquid-phase bonding process. Brazing was performed in a vacuum furnace using a nickel-based filler metal in a form of paste to join wrought Inconel 625 plates. Mechanical tests were carried out on single-lap joints unde...

In the present research an appropriate tool design is developed for joining of AA2198-T3 and AA2024-T3, subsequently the influence of rotational and traverse speed for the selected tool on the joint tensile properties is evaluated. Three shoulder profiles (flat, spiral, and fan) and five different pin profiles (tapered cylindrical, straight cylindr...

Surface finish of machined components plays a key role in their life performance. The aim of this research is to investigate the effect of different roughness parameters on high cycle fatigue behavior of Inconel718. Rotating bending fatigue tests have been performed on Inconel718 specimens with various surface roughnesses produced by turning. Heigh...

Cast low carbon CA-6NM (13%Cr-4%Ni) martensitic stainless steel has been used for hydraulic turbine runners manufacturing since the 60's owing to its high strength, toughness, corrosion, and cavitation-erosion resistance. These castings contain several types of defects which may have detrimental effects on the performance of the produced parts. Sev...

The tool geometry in friction stir welding (FSW) is a critical parameter to produce reliable and consistent joints, especially when it comes to joining dissimilar alloys with different mechanical and thermal properties. The aim of the present work is to investigate the effect of FSW tool design on the mechanical characteristic of as-welded AA2198(T...

Microstructures generated by δ phase precipitation in Inconel 718 (IN718) and related mechanical properties were investigated in this paper. Several heat treatments enabling the precipitation of the δ phase in various proportions and morphologies were conducted. Heat treatments were performed in a temperature range between 875 °C and 975 °C with ti...

This paper summarizes five years of joint efforts by Aubert & Duval, Ecole de Technologie Supérieure, and ISAE-ENSMA/Institut Pprime in developing microstructure graded turbine disks. It is mainly focused on the characterization of the mechanical properties of cast & wrought hybrid disks made of UDIMET TM 720Li and the newly developed AD730 TM allo...

The effect of cryogenic temperature (CT) on the graded microstructures obtained by severe shot peening using surface mechanical attrition treatment (SMAT) was investigated for two austenitic steels that used different mechanisms for assisting plastic deformation. For the metastable 304L steel, the depth of the hardened region increases because CT p...

The machining of high strength materials used in aeronautical applications generates damage on the subsurface layer, which can significantly affect the fatigue life of the machined components. It is then important to distinguish between the damages due to machining from those caused by mechanical polishing operations used for sample observation. In...

This work deals with the FSW joints composed of 2 hardened alloys AA7020-T651 and AA6060-T6. First of all, an experimental study has been carried out to obtain satisfactory joints in an industrial context with welding speeds up to 1100 mm/min. A microstructural analysis has been done for each joint. The mechanical properties have been also studied...

Induction hardening is a surface heat treatment that offers many advantages compared to thermo-chemical processes such as carbonizing and nitriding treatments. It is an attractive combination of speed, consistency, and control. However, physics interaction between electromagnetic fields and heat transfer makes this process challenging for developer...

The aerospace industry has been investigating the use of brazing for structural joints, as a mean of reducing cost and weight. There therefore is a need for a rapid, robust, and cost-effective non-destructive testing method for evaluating the structural integrity of the joints. The mechanical strength of brazed joints depends mainly on the amount o...

In recent years, there has been growing interest for the identification of material constitutive equations using machining tests (inverse method). However, the inverse method has shown some drawbacks that could affect the accuracy of the identified material constants. On one hand, this approach requires the use of analytical model to estimate the c...

Multipass welding procedures are common methods for 13Cr4Ni steels' fabrication and repairs. Compared to a single-pass weld procedure, the weld microstructure in a multipass weld is more heterogeneous due to the complex local thermal cycles imposed by adjacent weld passes. Furthermore, the final microstructure and mechanical properties of these ste...

This paper examines the metallurgical evolution of AISI Stainless Steel 321 (SS 321) during multi-step forming, a process that involves cycles of deformation with intermediate heat treatment steps. The multi-step forming process was simulated by implementing interrupted uniaxial tensile testing experiments. Evolution of the mechanical properties as...

Damage during loading of polycrystalline metallic alloys is localized at or below the scale of individual grains. Quantitative assessment of the heterogeneous strain fields at the grain scale is necessary to understand the relationship between microstructure and elastic and plastic deformation. In the present study, digital image correlation (DIC)...

The elastoviscoplastic behavior of α Ti-alloys microstructures is simulated under dwell-fatigue loading in order to identify the favorable crack initiation sites. To aim this goal, a mathematical model is developed using Cellular Automata (CA) approach. Each α Ti-alloy microstructure is presented with a Cellular Automaton formed of 900 and 10,000 c...

This paper proposes an experimental methodology to characterize complex parts presenting various gradients using aeronautical induction surface hardened spur gears. A 3D fatigue model taking into account residual stresses, microstructure variations, and surface roughness is then proposed for the prediction of the bending endurance limit. The model...

Cold spraying process was employed as a novel method to prepare electrocatalysts for hydrogen evolution by the water electrolysis process. Three electrode coatings were developed by cold spraying of nickel powder on aluminum substrates employing different coating parameters. The effect of the electrodes surface topography, microstructure, residual...

Damage during cycling loading of polycrystalline metallic alloys involves localized plastic straining at the scale of individual grains. To better understand damage accumulation processes and to build models for material behavior there is a need for quantitative assessment of the heterogeneous strain fields at the grain and even more microscopic sc...