Myriam Brochu

• Professor
• Professor (Full) at Polytechnique Montréal

The existence of cracks within ductile materials such as stainless steel induces local plasticity around the crack tip that may cause local changes in the microstructure. Although the plastic deformation and microstructural heterogeneities are expected to influence the electrochemistry of the area around the crack tip, few are the studies that corr...

Hydraulic turbine blades are exposed to cyclic loading which favors formation and propagation of fatigue cracks. Due to different in-service loading regimes, the crack tip is subjected to a range of strain rates. The present study proposes an experimental investigation of the mechanical properties of a 13%Cr-4%Ni martensitic stainless steel at stra...

Corrosion is one of the most destructive on the environment and also on our safety. Not only does the microstructure influence the severity of corrosion, but also does many other chemical and mechanical factors such as fatigue. For this reason, the ability to evaluate and further predict localized corrosion on materials subjected to stress has been...

Aerospace parts made of high strength steels, such as landing gears and helicopter transmissions, are often electroplated to satisfy various engineering specifications. However, plated parts are occasionnaly rejected because of hydrogen embrittlement, and the industry has few means of evaluating quantitatively the actual damage caused by hydrogen....

The effect of platform temperature combined with a T5 heat treatment on the fatigue life of additively manufactured aluminum alloy AlSi7Mg was characterized and understood. High-cycle fatigue tests were carried out on samples built with four platform temperatures (35 °C, 60 °C, 80 °C and 200 °C) and post-processing heat treatment strategies (F and...

This work is focused on the effect of natural defect on the fatigue resistance of a laser powder bed fusion additively manufactured Ti-6Al-4V titanium. To reveal the fatigue strength variability and its sensitivity to the defect size, push-pull fatigue tests have been undertaken on specimens with different sizes of highly loaded volume of material....

The effect of removing oxides prior to friction stir welding (FSW) by brushing the mating surfaces of 2024-T3 AlClad plates in lap joint assemblies was studied. Two types of surface preparation were selected: light brushing with a stainless steel brush (“brushed”) and simple cleaning with acetone (“as-clad”). Macroscopic discontinuities and geometr...

The effect of shielding gas on the mechanical and microstructural characteristics of ER410NiMo martensitic stainless steel weldments was investigated. Three weldments with various inclusion contents were manufactured using different shielding gas compositions and welding processes: gas metal arc welding (GMAW) with 100% argon (Ar), GMAW 85% Ar/15%...

The aerospace industry uses 200-h sustained-load test (SLT), described in ASTM F-519, to evaluate hydrogen embrittlement (HE) of their 4340 steel electroplated parts. The cadmium plating used in ASTM F-519 suggest that the coating density may affect HE in an important manner. Therefore, in this work, 4340 steel notched bars were plated with five di...

Multi-criteria decision-making methods are commonly used to rank manufacturing processes based on weighted economic and environmental criteria. The weighting process can be challenging, especially at early design stages where costs and environmental data are not precisely defined. In addition, for weights resulting in equivalent alternatives, no co...

Electroplating of aerospace parts generates hydrogen embrittlement, which is controlled by 200-hour sustained-load tests performed on cylindrical notched samples. Those tests are costly and offer only a pass-or-fail assessment, with limited interpretability. In this article, a new fractographic method is proposed to obtain a quantitative indication...

Disbonding and delamination of Stellite-hardfaced coating from high-temperature valves have presented a major challenge to the power generation industry. In order to study how the interfacial microstructure of Stellite-hardfaced coating might damage valve integrity during service, a series of aging experiments were conducted at temperatures ranging...

Thermal desorption spectroscopy (TDS) and sustained-load tests were used to investigate hydrogen embrittlement (HE), hydrogen profiles and the impact of the baking delay of cadmium-plated 4340 steel-notched bars. The results show a tremendous concentration of hydrogen in the cadmium coatings (200 to 1500 ppma) that does not contribute to HE. Hydrog...

In recent years, a major challenge facing the power generation industry is delamination of Stellite-hardfaced coatings from high-temperature valves. In order to meet this challenge, IN82 buffer layer was evaluated to replace the problematic S21 buffer layer. S6 and either S21 or IN82 hardfacing alloys were deposited onto F91 steel substrates using...

Cadmium-plated high-strength steel parts in aerospace are subject to hydrogen embrittlement (HE). Standard 200-h sustained-load tests (SLT) detect embrittlement on plated parts; however tests relying on fracture mechanics can improve interpretability and reduce testing times. We measured the invariant threshold for the onset of HE on compact tensio...

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...

The short crack growth behaviour of high strength martensitic 300M steel was studied for as-machined, polished and 2 peening conditions subjected to axial fatigue at 2 stress amplitudes. It was observed that prior austenite grain boundaries acted as barriers to short crack propagation in peened specimens within the peening induced compressive resid...

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...

Machining of aircraft structural components can waste up to 90% of the raw material. Therefore, evaluation of alternative manufacturing processes for those components is crucial for reducing the economic and environmental impacts of manufacturing. As the shape and material of a component must match the manufacturing process used, it is necessary to...

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...

Disbonding and delamination of Stellite hardfacing used in high-temperature valves have caused serious challenges in the power generation industry in recent years. To determine the microstructural factors that may contribute to the failures, Stellite 21 and Stellite 6 hardfacing alloys were deposited onto an F91 steel substrate using plasma-transfe...

Introduction When designing and installing implants, stress analyses should be performed in conditions close to those of everyday use. Specifically, for femoral implants, cyclic loading during gait has been demonstrated to produce fatigue failure. However, there is still no consensus in the literature regarding which modelling procedure is the most...

Fatigue crack growth behaviors of small and long cracks are compared in terms of crack closure, from near-threshold to final fracture, in over-aged aluminum alloy AA 7050-T7451. This is done experimentally to quantify inputs for crack propagation models such as the Navarro-Rios model. Growth rate of small cracks are determined as a function of stre...

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...

Shot peening on part edges is a critical operation in aerospace manufacturing. Edges are plastically deformed by the shot peening media, which can create stress concentration features known as “rolled edges”. The detrimental impact of rolled edges on fatigue life has already been observed in the literature. However, the effects of the geometries of...

******* 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...

Predicting the fretting fatigue crack propagation is complex and uncertain. It implies to consider stress gradient and short crack behavior. To address this challenge former in situ synchrotron X-ray imaging of micro-fretting fatigue experiments are simulated. First a Pugno et al./Fleury et al. short crack correction (SCC) approach is considered. T...

Fatigue tests and probabilistic analysis were carried out on aluminum alloy 7050-T7451 samples having surface conditions of as-polished, as-machined, and shot peened. Different combinations of media and intensity were studied. Fatigue tests were carried out in the high and low cycles fatigue regimes. Fatigue life dispersion was analyzed and toleran...

High and low cycle fatigue tests performed on shot peened Inconel 718 can result in different crack initiation locations and mechanisms as well as in a wide range of fatigue lives depending on shot peening parameters. A model coupling Navarro and de los Rios crack propagation with Chan's crack initiation models is developed and successfully used to...

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...

Introduction Fatigue failure is due to the initiation of cracks within the structure, followed by their growth until fracture. Shot peening is a well-known means of improving fatigue life since it induces beneficial compressive residual stresses and local hardening (Gao 2011, Oh, Kim et al. 2015). However, surface deterioration induced by the peeni...

This paper presents a study on the influence of welding residual stresses (RS) on fatigue crack propagation rate (FCPR) in mode I. The objective of this work is to develop a novel methodology that allows a variation of a RS field in the studied specimen while keeping constant all other variables influencing FCPR. This led to the development of a no...

At room temperature, nickel-based superalloy Inconel 718 softens under fully reversed plastic deformation cycles. Chaboche’s unified constitutive equations have been previously used in the literature to predict nickel-based superalloy cyclic softening behavior. To better fit our results, the constitutive equations were modified to account for conti...

Wire Beam Deposition (WBD) is an Additive Manufacturing (AM) technique used in creating thick or thin geometries from wire stock. This technique has recently generated interest in the aerospace field for its potential to fabricate high performance, defect-free materials while minimizing post-processing and achieving high buy-to-fly ratios. Also, vi...

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...

High strength steel samples were analysed by N-15 nuclear reaction analysis in order to detect hydrogen that may have been introduced by electroplating process. The NRA signal decreased during exposure of the ion beam and residual gas analysis showed that the gas was desorbed by the beam interaction. The variable hydrogen signal could be well descr...

Additive Manufacturing (AM) is a novel process that promises an increased efficiency in material use, while allowing the production of advanced topologies and the seamless integration of inner cavities and pathways without the use of complex tooling. As of now, little work has been done on the fatigue performance of these materials. Concurrently, a...

This paper presents a study on the influence of welding residual stresses (RS) on fatigue crack propagation rate (FCPR). The objective of this work is to develop a novel methodology that allows a variation of a RS field in the studied specimen while keeping constant all other variables influencing FCPR. This led to the development of a novel specim...

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...

The temperature effect on the tensile behavior of a triaxially braided composite was investigated in two different loading directions. The damage evolution was monitored and the results were explained with the help of experimental, analytical and numerical methods. The evolution in the constituent elastic properties was responsible for stress redis...

This study presents a failure analysis of a femoral orthopaedic implant. This implant is a locking compression plate that was fixed to a broken femur using two types of screws: locking and compression screws. The study elucidates the causes of an in situ premature failure of the plate and screws. Chemical analysis, hardness tests, and microstructur...

The service life of Polymer Matrix Composite Materials can be severely affected by long exposures to elevated temperatures. This study investigated the high temperature durability of a carbon/MVK10 triaxially braided textile composite. The goal was to monitor, analyze and quantify the evolution of physical and chemical aging processes to verify if...

The aim of the study is to demonstrate the similar behaviour of crack arrest condition in mode I for partial slip simple fretting, prestressed fretting loadings, and conventional fatigue crack growth experiments. The stress intensity factor range ΔKth threshold of long crack is estimated based on crack arrest condition for partial slip fretting and...

Cast martensitic stainless steels, 13%Cr–4%Ni, having carbon contents between 0.018 wt% and 0.067 wt% were normalized, air quenched, and tempered at two different temperatures (550°C and 610°C). Their microstructures were characterized by optical microscopy and X-ray diffraction (XRD). Macro and microhardness, tensile strengths, and impact resistan...

Two objectives were targeted: 1) compare the high cycle fatigue behavior of rheocast aluminum alloy 357 prepared by the swirl enthalpy equilibration device (SEED) and by the Council for Scientific and Industrial Research (CSIR) process, and 2) study the effect of surface liquid segregation (SLS) on the fatigue behavior of the CSIR material. Rectang...

The fatigue crack growth behavior of a CA6NM weld heat affected zone (HAZ) was investigated. Fatigue crack growth tests in river water environment were conducted on as-welded and post-weld heat treated specimens at load ratios R = 0.1 and R = 0.7. For a fully open crack, i.e. at R = 0.7, the HAZ fatigue behavior was similar to that of the base meta...

The fatigue crack growth behavior in an automatic flux core arc weld was investigated for stainless steel alloy CA6NM. As-welded and heat treated compact tension specimens were prepared with the crack propagation plane perpendicular to the weld. Constant stress intensity factor range tests were performed at a load ratio R = 0.1 to reveal intra-spec...

Solidification cracking was observed during a tungsten-inert gas (TIG) welding process used to join two thin sheets of nickel-based superalloy IN718. Microstructural analysis of cracked specimens showed a centerline grain boundary (CLGB) susceptible to limit the hot ductility of the welds. Different welding parameters were modified to avoid the for...

The fatigue crack growth behavior of a martensitic stainless steel CA6NM hydraulic turbine runner weld was investigated to unveil microstructural effects in the filler metal, heat affected zone and base metal. Knowledge of such effects is paramount for engineers who design these components for long fatigue lifetimes. Constant stress intensity facto...

The high cycle fatigue strengths of aluminum–silicon–magnesium 357 alloy prepared by permanent molding and semi-solid molding are measured. Results show that precipitation hardened permanent mold (PM) and semi-solid mold (SSM) materials have fatigue strengths at 107 cycles of 82 MPa and 113 MPa respectively at R = −1, and of 47 MPa and 78 MPa respe...

The high cycle fatigue resistances of aluminum-silicium-magnesium 357 alloy prepared by semi-solid forming (SSM) and conventional permanent mold casting (PM) are compared under fully reversed loading. Results, reported in S-N diagrams, show that rheocasting improves the as-cast alloy mean fatigue strength, by 36% at 10(7) cycles. Part of this impro...

The primary objective of this work is to explain the fatigue strength difference between a permanent mold and a rheomolded material on the basis of the microstructural differences. The experimental work has been carried out using aluminum 357 alloy which was produced in six specimens characterized by different microstructures. This alloy was chosen...

This paper presents a description of the experimental conditions developed to measure high cycle fatigue resistance as well as to monitor small crack growth in cast aluminum alloys. Experiments and finite element analysis were carried out to justify the choice of a specimen geometry that facilitates small crack monitoring. Three different specimen...

Aluminum alloys are increasingly used in automotive and aeronautic applications to produce high performance, lightweight parts. Among the reasons for this, is the emergence of high integrity processes (HIP), which widens the field of application for cast aluminum alloys. In fact, metallurgical quality and consistency that characterize components pr...

The research effort oriented towards the modelling of metal powder compaction necessitates laborious experimental work to validate theoretical assumptions. Many interesting experimental setups have been reported in the literature. However, results obtained from a setup can be significantly different from others leading to divergent efforts and conc...

This method is based on data collected during previous expertise done on similar products. The objective is to predict reservoir and tube useful life and wall thickness using a minimum of field measurements. The method was initially developed for non-destructive inspection such as radiography and ultrasound. It can be described in eight steps: 1) A...

Ridging is a serious problem which occurs in ferritic stainless steel after tensile deformation in the rolling direction, and steel makers are attempting to respond to the surface deterioration caused by this phenomenon. Many authors have suggested that a long distance order in the lattice orientation of a sheet could be responsible for ridging. In...

This paper gives a general overview of a method developed to optimised NDT inspection planning and results analysis. This computerized tool offers sample size calculation, statistical analysis of thickness measurements and life prediction modules. In each step and module, calculations are driven by equations developed using data gathered from previ...