Papers by Jacques Lanteigne
Scripta Metallurgica, 1978
Modeling and Numerical Simulation of Material Science, 2019
The intent of this paper is to propose an engineering approach to estimate the stress intensity f... more The intent of this paper is to propose an engineering approach to estimate the stress intensity factor of a micro crack emerging from an inclusion in relation with the morphology of the inclusion and its relative stiffness with the matrix. A micromechanical model, based on the FEA (finite element analysis) of the behavior of cracks initiated at micro structural features such as inclusions, has been developed using LEFM (Linear Elastic Fracture Mechanics) to predict the stress intensity factor of a micro crack emerging from an inclusion. Morphology of inclusions has important connotations in the development of the analysis. Stress intensity factor has been estimated from the FEA model for different crack geometries. Metallographic analysis of inclusions has been carried out to evaluate the typical inclusion geometry. It also suggests that micro cracks less than 1 µm behave differently than larger cracks.
Acta Mechanica Solida Sinica, 2017
International Journal of Fatigue, 2017
Austenitic stainless steel E309L is frequently used for welded repairs on 13%Cr-4%Ni martensitic ... more Austenitic stainless steel E309L is frequently used for welded repairs on 13%Cr-4%Ni martensitic stainless steel blade runners. However, very high tensile residual stresses are found in the upper layers of these repairs, thus reducing the fatigue resistance of the repaired area in comparison with the free of residual stress base material. The use of hammer peening to increase the fatigue life of E309L welded on UNS-S41500 base metal plates has been investigated using welded samples replicating in situ blade runner repairs. Residual stress measurements using the contour method on these samples have confirmed the high stresses caused by flux cored arc welding (FCAW) of E309L, leaving stress magnitudes close to the ultimate tensile strength of the base material. Hammer peening of the surface beads effectively creates high compressive stresses at the weld's surface up to 3 mm depth. Alternating bending fatigue tests conducted on hammer peened samples have shown an average life increase of 5.8 times at S a = 330 MPa over unpeened samples. Fatigue tests have however shown diminishing returns when overpeening the samples.
Journal of Reinforced Plastics and Composites, 1996
This paper addresses the problem of stress calculation and optimization in a FRP (Fibre-glass Rei... more This paper addresses the problem of stress calculation and optimization in a FRP (Fibre-glass Reinforced Plastic) pultruded rod crimped into a metal end-fitting. This type of assembly is used mainly for suspension and line post insulators. We discuss herein some aspects that merit consideration in any given design approach. In many respects FRP pultruded materials are anisotropic. The anisotropy of their elastic constants influences the distribution of stresses while the anisotropy of their mechanical properties (ultimate strengths) limits their load carrying capacity. Finally, the anisotropy of their failure modes governs the progression and the spread of the damage. Each level of anisotropy will be discussed distinctly. Geometrical considerations are also necessary to arrive at an efficient design. Namely, we will consider the frictional interactions between the end-fitting inner wall and the rod, then we will present our approach in selecting the appropriate LID ratio (i.e., the ratio of the end-fitting length over the rod diameter), and finally we will discuss the influence of the compression profile, i.e., the permanent radial displacement imparted to the rod due to the action of the crimping force.
Materials Science and Engineering: A, 2016
The austenitic stainless steel E309L filler is a commonly used material for in-situ crack repairs... more The austenitic stainless steel E309L filler is a commonly used material for in-situ crack repairs of hydro-turbines due to its high weldability, mechanical and chemical compatibility with the turbine's base material. However, experimental data for the as-welded E309L filler is scarce. In this paper, the mechanical properties of asdeposited 75% Ar/25% CO 2 flux-cored arc welding E309L austenitic stainless steel are investigated. The material is shown to be rate-and temperature-sensitive. Furthermore, although the directional nature of the welding/repair process might suggests otherwise, the response is found to be isotropic. Finally, a classic threedimension Johnson-Cook plasticity theory is implemented and reproduces the experimental results with good accuracy.
Structural and Multidisciplinary Optimization, 2016
In this paper, the industrial hammer peening process is optimized using multi-objective, sequenti... more In this paper, the industrial hammer peening process is optimized using multi-objective, sequential approximate optimization, which is a mathematics-plus finite element-based algorithm. Since the number of design and objective variables is significant, the global optimization problem is split into two, more manageable multi-objective subproblems. The use of surrogate modelling together with an intensification and diversification strategy for solving the optimization subproblems allows for significant computational cost savings without loss of accuracy. Additionally, we propose a Bayesian inference criterion-based sensitivity approach for "filtering-out" design variables which do not significantly affect objectives variables. Finally, guidelines for selecting appropriate Pareto optima are given using N − 1 Pareto diagrams, where N is the number of objective variables.
This article presents the Finite Element (FE) modeling of a two-seam welding process for a T join... more This article presents the Finite Element (FE) modeling of a two-seam welding process for a T joint with a V chamfer preparation. The "birth and death" method is used in ANSYS© to simulate the filler metal deposition and the heat source. The weld pool is simulated according to the double ellipsoid configuration proposed by Goldak et al. The analysis takes into consideration the temperature dependent non-linear material properties and uses a new method introduced to compute the temperature dependent radiation and convection combined coefficient of heat dissipation. Improvements in the calculation are achieved by combining two types of meshing and using a relationship between the time increment and the size of the elements. Time step is calculated as a function of the torch position which is determined according to the finite element meshing. The FE simulation is divided into two consecutive parts: the thermal simulation and the structural simulation.
Proceedings of First International Conference on Conduction and Breakdown in Solid Dielectrics, 1983
Gas bubbles can be grown in XLPE without an electric field, just requiring water and soluble impu... more Gas bubbles can be grown in XLPE without an electric field, just requiring water and soluble impurities. The pressure can be high enough to fracture the polymer, thus providing the initiation step of treeing. The roles of ΔGh and oxidation are still ambiguous.
International Journal of Fatigue, 2016
Abstract The aim of the present work is to study the interaction between two loading cycles in hy... more Abstract The aim of the present work is to study the interaction between two loading cycles in hydraulic turbine runners, i.e. baseline cycles which are the result of power output variations and periodic underloads which correspond to runner start/stop sequences. In order to make better evaluations of fatigue lives, there is a need to determine the real crack growth as compared to those predicted by linear damage summation. This comparison is made for three wrought steels, AISI 415, ASTM A516 , and AISI 304L. Fatigue tests were run under both constant amplitude loading and periodic underloads at two constant values of maximum stress intensity factor, K max . The crack growth under periodic underloads was faster than that predicted by linear damage summation for the A516 and 304L steels, while almost no acceleration was found for the 415 steel. The acceleration factors reached the highest values under low K max and high load ratio of baseline cycles. High tensile residual stresses and strain hardening at the crack tip caused by underloads contribute to crack growth acceleration during the subsequent baseline cycles.
Proceedings of SPIE - The International Society for Optical Engineering
This study is based on cracked metal beams obtained under controlled fatigue-crack propagation. T... more This study is based on cracked metal beams obtained under controlled fatigue-crack propagation. The beams were clamped in a heavy vise and struck in order to obtain a clean impulse modal response. Spectrograms of the free-decay responses showed a time-variant frequency and damping behavior: the usual hypothesis of constant modal parameters is no longer appropriate since they are revealed to be a function of the amplitude. Signal-processing methods have been developed such as the worm transform and phase spectrogram with enough accuracy to display the behavior of an uncracked beam where a slight nonlinear stiffness is generated by the clamping. Moreover, extracted worms show that the second mode of a beam with a deep crack is modulated in frequency by the first mode. In fact, the dominant mode opens and closes the crack, thereby modulating the beam stiffness, which affects higher modal frequencies. With deep cracks, three vibration states are observed: one where the crack is alternately fully open and fully closed, a second with a crack partially opened, and a third with an alternating force acting on a closed crack. In the latter case, the peak force is smaller than the intrinsic closure load of the crack.
IEEE Transactions on Electrical Insulation, 1984
It is shown that the relatively large concentration of impurities in cables is even higher in wat... more It is shown that the relatively large concentration of impurities in cables is even higher in water trees. Gas bubbles observed in cavities filled with different salt solutions generate very high pressures able to fracture XLPE samples. It was also observed that fracture in XLPE under a cyclic mechanical load is frequency-depei.dent. The influence of oxidation on dielectric properties is also discussed.
ABSTRACT In this study, the viability of thick-gauge section assembly for hydroelectric turbine m... more ABSTRACT In this study, the viability of thick-gauge section assembly for hydroelectric turbine manufacture was considered by electron beam welding (EBW) of CA6NM martensitic stainless steel, a widely utilized hydro-turbine cast material. Particularly, bead-on-plate (BOP) trials on 60 mm-thick CA6NM plates were carried out using a 42 kW high vacuum EBW system. The influence of the heat input, beam focus (BF) position, beam defocusing, and in-situ pre-heating conditions on the characteristics of the weldments, such as the bead geometry, weld integrity, fusion zone (FZ) and heat affected zone (HAZ) microstructures and hardness were evaluated. A relationship between the welding parameters and the resulting depth of penetration was established. A methodology for in-situ heating of the thick-gauge section prior to welding was developed and evaluated for reducing welding defects in CA6NM.
Modeling and Numerical Simulation of Material Science, 2013
A micromechanical model, based on the FEA (finite element analysis), was developed to estimate th... more A micromechanical model, based on the FEA (finite element analysis), was developed to estimate the influence of hydrogen pressure on short crack behaviour. Morphology of voids has important connotations in the development of the model. Stress intensity factor was calculated for different crack geometries under hydrogen pressure. The analysis indicates that the form factor of a crack emerging from a round void will be less affected by trapped hydrogen pressurecompared to an elongated void. This analysis reinforces the beneficial effect of inclusion shape control in reducing significantly the detrimental effect of hydrogen.
Ultrasonics International 83, 1983
Non-ceramic or composite insulators are increasingly used for distribution lines, high-and ultra-... more Non-ceramic or composite insulators are increasingly used for distribution lines, high-and ultra-high voltage transmission lines. Acoustic emission technique is potentially useful to reconstitute the stress-history of in-line insulators, to characterize damage accumulation and to study failure mechanisms of such insulators for purposes of design improvement and manufacturer's selection.
Flaw Growth and Fracture, 1977
Application of the relation J 1 c = K 1 c 2 /E yields values of J 1 c which are different from th... more Application of the relation J 1 c = K 1 c 2 /E yields values of J 1 c which are different from those measured directly. This difference is attributed to the plasticity of the crack tip. A more accurate relation for evaluation of J 1 c which takes into consideration the mechanical properties of the material such as the yield stress and Young's modulus, and based on compliance tests, is formulated. Experimental tests which demonstrate the validity of this equation are presented.
Materials Science Forum, 2005
The strains induced by hammer-peening were measured by strain gauges on a mild steel plate during... more The strains induced by hammer-peening were measured by strain gauges on a mild steel plate during the hammer-peening operation. This process has recently been robotized by the research institute of Hydro-Québec (IREQ), so the hammer-peening performed for this study was done with the help of a Scompi robot. The resulting stresses calculated from the strain measurements were compared with residual stress measurements made with the hole drilling technique. The comparison shows a very good correlation of the two sets of measurements. Residual stress measurements were also made in the hammer-peened zone: as expected we found a highly biaxial compressive state of stress in this zone. An unexpected region of transverse tension was found at the end of the hammerpeened zone. This region can be very critical if hammer-peening is made with the objective of improving fatigue behaviour.
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Papers by Jacques Lanteigne