Jean-Paul Baïlon | École Polytechnique de Montréal (original) (raw)
Papers by Jean-Paul Baïlon
Engineering Fracture Mechanics, 1987
... From this result and a generalization of Irwin's principle to V-notch singularities, a g... more ... From this result and a generalization of Irwin's principle to V-notch singularities, a general formulation of the endurance limit of V-notched members was derived. ... Int. S. Mech. Sci. 20, 201-206 (1978). [2] MH El Haddad, KN Smith and TH Topper, A strain-based intensity factor ...
Fatigue & Fracture of Engineering Materials and Structures, 1987
Fatigue life prediction of welded joints needs an accurate and exhaustive theoretical Fracture Me... more Fatigue life prediction of welded joints needs an accurate and exhaustive theoretical Fracture Mechanics characterization of weld toe crack propagation. The method proposed by Albrecht et al. leads rapidly to accurate solutions of the LEFM AK-parameter. However, non-LEFM short crack behavior within the notch (weld toe) plastic zone must be taken into account. Available information on notch fatigue is surveyed, and practical cases where short crack growth is likely to occur are identified. Based on an elastoplastic finite element analysis, the LEFM validity limits and errors resulting from the misuse of LEFM in fatigue life prediction are quantified.
… of Metals and Alloys(ICSMA 7) …, 1985
Formation of Extrusions and Intrusions in Copper and in a Mild Steel. JI Dickson, S Turenne, JB V... more Formation of Extrusions and Intrusions in Copper and in a Mild Steel. JI Dickson, S Turenne, JB Vogt, JP Bailon Strength of Metals and Alloys(ICSMA 7). 2, 1237-1242, 1985. The study of the characteristics of short extrusions ...
S UMMA R Y S&ce the simple equations proposed by Ludwik and Hollomon do not 9ire an adequate desc... more S UMMA R Y S&ce the simple equations proposed by Ludwik and Hollomon do not 9ire an adequate description of the stress-strain curves for Armco iron at room temperature, a new equation has been developed to fit the experimental data. In this new equation, there are parameters whose variation with grain size parallels that of similar parameters in the Hall-Petch relation for the lower yieM stress. Furnace cooled specimens and specimens quenched from 72f C show the same work-hardenin9 behavi-our. This result implies the same mechanisms in both cases and experiments on the stress-dependence of dislocation density support this conclusion. Makin9 use of the dislocation density data in the analyses of the stress-strain curves and the Hall-Petch relation the authors show that in furnace cooled specimens the Liiders band propagates by the nucleation qf fresh dislocations from sources at the 9rain boundaries. RESUME A tempkrature ambiante, la courbe de traction dufer Armco ne peut Ytre dOcrite par une Oquation unique telle que celles propos&s par Ludwik et Hollomon. A partir des rksultats exp&imentaux, les auteurs ont donc dOvelopp~ une nouvelle Oquation qui lie la contrainte plastique et la dkformation plastique et qui est unique pour le domaine de dfformation OtudiO.
Materials Science and Engineering, 1983
Variations in stress corrosion cracking (SCC) velocities after the introduction of several drops ... more Variations in stress corrosion cracking (SCC) velocities after the introduction of several drops of 3.5% NaCl solution into the crack mouth were followed using acoustic emission. It is suggested that studies of the factors influencing this variation may prove a useful method of studying the processes which control SCC kinetics.
Cyclic stress-strain curves for the saturated or quasi-saturated state during tests on polycrysta... more Cyclic stress-strain curves for the saturated or quasi-saturated state during tests on polycrystalline 70Cu-3OZn ~ brass showed a grainsize-dependent plateau for intermediate plastic strain amplitudes. This plateau was associated with the spread of pronounced slip bands (in which relatively strong recovery had occurred) across grain boundaries.
ABSTRACT Silver and Ag-W (10 weight percent W) were operated in a 5.I-A (peak) 308-V (peak) full-... more ABSTRACT Silver and Ag-W (10 weight percent W) were operated in a 5.I-A (peak) 308-V (peak) full-wave rectified dc circuit. The experimental switching system was operated 1.5 times per minute; the opening and closing velocities were 4 x 10-2 and 3 x 10-4 cm/s, respectively; the fully open contact spacing was 200 µm; and the contacts were closed for 3 s. The opening and closing of the contacts were controlled by a heater-bimetal combination attached to the moving contact. The following contact pairs were used: Ag versus Ag, Ag-W versus Ag-W and Ag versus Ag-W. All combinations of contact material and contact polarity were used. The experimental results showed that there was always a net transfer of contact material from the cathode to the anode. The volume of material transferred was strongly dependent upon whether the anode was the moving (hotter) or the fixed (cooler) contact: the greater erosion occurring when the anode was the hotter contact. For Ag versus Ag contacts thc erosion pattern resulted inone pip on the anode and one crater on the cathode. For Ag-W versus AgW contacts the presence of the small percentage of W resulted in multiple pip and crater formations. The experiments with the Ag versus Ag-W showed that the cathode electrode material determined the erosion pattern observed, i.e., when the Ag-W was the cathode, multiple pip and crater'formations occurred, but when Ag was the cathode, only a single pip and crater structure was observed. The presence of the W either in the cathode or in the anode decreased the observed erosion. These experimental results are discussed in terms of how the presence of W affects the emission characteristics of the cathode region and also affects the movement of the arc roots.
Engineering Fracture Mechanics, 1989
ABSTRACT Experiments were carried out on an AISI-SAE 1005 mild steel at 298, 233 and 173 K with R... more ABSTRACT Experiments were carried out on an AISI-SAE 1005 mild steel at 298, 233 and 173 K with R-ratios of 0.1, 0.3 and 0.5 to verify the influence of cleavage or cyclic cleavage on the macroscopic fatigue crack growth rate, . Cleavage during fatigue occurred at 233 and 173 K as quite uniformly distributed patches within a ductile (striated) fracture surface. The amount of cleavage during fatigue propagation increased as the temperature and as the R-ratio decreased and, at a given temperature, was determined primarily by the ΔK value. The influence of this cleavage on the macroscopic value of was analysed through its influence on the crack tip opening displacement, employing the model of the semi-cohesive plastic zone developed in part I. This model was shown to explain satisfactorily the behavior observed.
Materials Science and Engineering: A, 1994
Fatigue crack growth tests under constant-amplitude loading conditions in air and in vacuum have ... more Fatigue crack growth tests under constant-amplitude loading conditions in air and in vacuum have been carried out in the moderate growth rate regime. The fracture surfaces were examined at low and high magnifications in a scanning electron microscope to identify the different fractographic features. An etchant that attacks the basal crystallographic planes preferentially was used to elucidate the cracking crystallography. The results obtained show that large facets lying in or close to { 111} planes are found in air at low R ratio and in vacuum at both the R ratios studied. These facets are formed by micro-void coalescence as shown by the presence of dimples. The other fractographic features identified are pseudointergranular facets, the formation of herringbone patterns and the formation of pseudo-striations. These features are found only in air. Different mechanisms are proposed to explain the observed cracking modes.
Engineering Fracture Mechanics, 1981
ABSTRACT Acoustic emission was obtained during fatigue crack propagation in a D6 tool steel and a... more ABSTRACT Acoustic emission was obtained during fatigue crack propagation in a D6 tool steel and a 1015 mild steel using two different load ratios, R. It was found that the slope of the acoustic emission count rate vs stress intensity factor was higher when R = 0.2 than when R = 0.4. These results are described in terms of several models of acoustic emission mechanisms available in the literature as well as by a proposed new model. It is concluded that the observed R dependence can be explained by the combination of the contribution of two different models. These two models are the new plastic yielding as well as the crack tip fracture processes.
Acta Metallurgica, 1971
Les boulets de broyage utilisés dans l'industrie minière pour la transformation de la roche en fi... more Les boulets de broyage utilisés dans l'industrie minière pour la transformation de la roche en fine sont soumis à des conditions très sévères et complexes. L'usure abrasive et les chocs répétés sont les causes essentielles de leurs dégradations. Pour répondre aux exigences mécaniques et technologiques, ces boulets sont fabriqués en fonte fortement alliée au chrome (10 à 13% de chrome). En effet, le secteur du ciment utilise des boulets de broyage fabriqués par la fonderie de Tiaret. Durant leur utilisation, ces boulets ont montré des performances inférieures; notamment, ils présentent un taux élevé de casse lié à une mauvaise résistance aux chocs et à l'usure. Dans l'objectif d'identifier les causes de ce problème et d'optimiser le traitement thermique adéquat pour réduire la fragilité de ces boulets en vue de parvenir à une amélioration des propriétés mécaniques, on se propose d'effectuer une série de traitements thermiques d'austénitisation à la température de 1050°C avec un temps de maintien de 5 heures, refroidis à l'eau et suivis de revenus à différentes températures de 500°C, 525°C, 550°C et 575°C pendant un temps de maintien de 5 heures. Pour ce faire, une fonte fortement alliée au chrome à l'état brut de coulé fournie par la fonderie de Tiaret, utilisée dans la fabrication des boulets de broyage, a été étudiée en effectuant une caractérisation structurale, microstructurale obtenue par MEB, microanalyse EDAX, DRX et mécanique basée sur les tests d'usure et de résilience. Les résultats obtenus ont montré la présence des carbures de type M 7 C 3 pour tous les traitements thermiques réalisés. Le traitement d'austénitisation à 1050°C offre des duretés élevées de l'ordre de 966 HV et les spectres de diffraction ont révélé que les intensités des pics correspondant à l'austénite résiduelle sont nettement inférieures à ceux de la martensite. En outre, le spectre révèle la présence d'un autre carbure de type M 2 C. La diminution de la dureté après revenu pour l'ensemble des échantillons traités pourrait s'expliquer par la précipitation de carbures de type M 2 C qui entraîne un appauvrissement en carbone de la solution solide tout en relaxant les contraintes résiduelles. Par ailleurs, ces carbures M 2 C renforcent la dureté superficielle tout en maintenant le coeur de la pièce malléable ce qui favorise ainsi la résistance aux chocs. L'échantillon, ayant subi un revenu à 525°C pendant 5 heures, présente une meilleure résistance à l'usure et aux chocs.
Engineering Fracture Mechanics, 1987
... From this result and a generalization of Irwin's principle to V-notch singularities, a g... more ... From this result and a generalization of Irwin's principle to V-notch singularities, a general formulation of the endurance limit of V-notched members was derived. ... Int. S. Mech. Sci. 20, 201-206 (1978). [2] MH El Haddad, KN Smith and TH Topper, A strain-based intensity factor ...
Materials Science and Engineering: A, 1989
The fractography of transgranular stress corrosion cracking (TSCC) of annealed 316 stainless stee... more The fractography of transgranular stress corrosion cracking (TSCC) of annealed 316 stainless steel (s.s.) tested in boiling MgCL solution at 154 °C was studied, with particular attention paid to the crystallography of cracking and to the influence of the stress intensity factor K. Etch-pitting and stereographic observations were employed in order to determine the cracking crystallography. At low K values, cracking occurred predominantly on {100} planes with preferential propagation in a (110) direction. This crystallography and the fractographic features observed are consistent with the crack path alternating microscopically between two sets of {111} planes. Regions of {100}(100) crack propagation were also observed and were consistent with cracking occurring microscopically on four sets of {111} planes. This latter cracking crystallography was often associated with herringbone and fan-shaped patterns of river lines. The latter patterns occurred especially at intermediate K values and were related to the relative ease of crack propagation within grains and across grain boundaries. At high K values, feather-like and sheet-like microfractographic features were generally observed and were shown to result from quite large decohesion steps on different sets of {111} planes. The variation in fractographic details with K was consistent with the number of {111} planes on which cracking occurred and with the size of the decohesion steps on the individual planes. The observations also indicated that the microscopic crack path followed planes on which localized slip had occurred," however, these observations did not permit complete identification of the crack propagation mechanism. The strong similarity between the fractography of TSCC of 316 s.s. and of near-threshold fatigue cracking is discussed, as is the role of the fracture of river lines in influencing the fractographic features.
Canadian Metallurgical Quarterly, 1980
Materials Science and Engineering, 1985
The presence of fine striations (0.2-0.4 pm spacing) on fracture surfaces of aluminium alloy 7075... more The presence of fine striations (0.2-0.4 pm spacing) on fracture surfaces of aluminium alloy 7075-T651 produced by stress corrosion cracking in air as well as the characteristics of the acoustic emission during stress corrosion cracking in air and in 3.5% NaCl solution indicate that the stress corrosion crack advances by small discrete crack jumps.
Canadian Metallurgical Quarterly, 1984
ABSTRACT The corrosion-fatigue behaviour, as typified by the crack propagation rate-cyclic stress... more ABSTRACT The corrosion-fatigue behaviour, as typified by the crack propagation rate-cyclic stress intensity factor relationship, was studied for KCR 171 austenitic - ferritic stainless steel in simulated white water (pH = 4.5) under different conditions and compared to result s obtained in air at 25°C. In white water, increasing the temperature from 20 to 90°C (at a frequency of 1Hz) or decreasing the frequency from 5 to 0.1 Hz (a t 50°C) results in a significant increase in the crack propagation rate for ΔK values between 10 and 40 MPa.m 1/2. This increase in the crack velocity during this corrosion-fatigue is associated with an embrittlement of the ferritic phase, which different fractographic aspects suggest is caused by hydrogen embrittlement. Résumé Le comportement en fatigue- corrosion de l'acier austéno-ferritique KCR 171, a été étudié par mesure de la vitesse de propagat ion da/dN en fonction du facteur d'inte nsité de contrainte ΔK sous diverses conditions expérirnentales. L'état de référence est celui du comportement dan s l'air à 25°C. Dan s l'eau blanche (pH = 4,5) une augmentation de la température de 20 à 90°C (à fréquence constante égale à 1 Hz) ou une diminution de la fréquence de 5 à 0,1Hz (à température constante égale à 50°C) on t pour conséquence, une augmentation notable de la vitesse de fissuration pour des valeurs de ΔK comprises entre 10 et 40 MPa. m 1/2. Cette augmentation de la vitesse de fissuration est due à une fragilisation de la phase ferritique. Les aspects par ticuliers de l'étude fractographique permettent de conclure que la fragilisation de la phase ferritique est probablement due à une fragilisation par l'hydrogène.
Revue de chirurgie orthopédique et réparatrice de l'appareil moteur, 1979
Recent clinical and experimental results in the prosthetic replacement of the anterior cruciate l... more Recent clinical and experimental results in the prosthetic replacement of the anterior cruciate ligament are minimal and this fact has incited us to search for additional fundamental characteristics of natural and synthetic ligaments. The dissection of over 30 human knees (5 fresh and 27 embalmed specimens), of 50 dog knees and of 20 cat knees showed that the posterior cruciate ligament was longer and of bigger size than the anterior cruciate ligament. In dogs, the anatomo-radiological study showed a lenghtening of 14,4 p. 100 for the anterior cruciate and of 10,5 p. 1u0 for the posterior cruciate ligament in the various goniometric positions. Traction with the Instron apparatus using whole knee with preserved bony attachments revealed an elastic resistance (yield point) of the ligament of about 50 kg, 60 kg and 30 kg (for human, dog and cat respectively) with elastic elongation (at the yield stress) of 25 p. 100, 35 p. 100 and 45 p. 100 (respectively). Trials on the polyethylene pr...
Scripta Metallurgica, 1975
In fatigue studies one of the most important parameters ls the threshold stress intensity factor ... more In fatigue studies one of the most important parameters ls the threshold stress intensity factor AK_ below which a crack cannot propagate. A~ may be compared to the endurance limit in ~hler's experiments and allows prediction of whether the propagation of a crack, characterlsed by its length "a" and submitted to a given cyclic stress, can occur. The cycllc stress is characterised by the stress range (Oma x -Omln) , the absolute values oma x and Omi n or by the cyclic stress ratio R=°mln Many authors (1,2,3) have introduced AK T in the emplrleal relationships giving the dependence of the propagation rate da~n of the crack on the stress intensity factor AK~na x -Kml n . In recent years, some authors (4) have paid spealal attention to the dependance of AK on R and on the microstructural parameters of material. T Klesnil and Lukas (3) have prevlously proposed an empirical relatlonshlp:
While the influence of strain-aging on the endurance limit and on the dislocation behaviour durin... more While the influence of strain-aging on the endurance limit and on the dislocation behaviour during cyclic deformation has received some attention in the literature, almost no attention appears to have been paid to the influence of strain aging on fatigue crack propagation. An influence of strain aging on fatigue propagation can be expected to manifest itself most clearly at the
Engineering Fracture Mechanics, 1987
... From this result and a generalization of Irwin's principle to V-notch singularities, a g... more ... From this result and a generalization of Irwin's principle to V-notch singularities, a general formulation of the endurance limit of V-notched members was derived. ... Int. S. Mech. Sci. 20, 201-206 (1978). [2] MH El Haddad, KN Smith and TH Topper, A strain-based intensity factor ...
Fatigue & Fracture of Engineering Materials and Structures, 1987
Fatigue life prediction of welded joints needs an accurate and exhaustive theoretical Fracture Me... more Fatigue life prediction of welded joints needs an accurate and exhaustive theoretical Fracture Mechanics characterization of weld toe crack propagation. The method proposed by Albrecht et al. leads rapidly to accurate solutions of the LEFM AK-parameter. However, non-LEFM short crack behavior within the notch (weld toe) plastic zone must be taken into account. Available information on notch fatigue is surveyed, and practical cases where short crack growth is likely to occur are identified. Based on an elastoplastic finite element analysis, the LEFM validity limits and errors resulting from the misuse of LEFM in fatigue life prediction are quantified.
… of Metals and Alloys(ICSMA 7) …, 1985
Formation of Extrusions and Intrusions in Copper and in a Mild Steel. JI Dickson, S Turenne, JB V... more Formation of Extrusions and Intrusions in Copper and in a Mild Steel. JI Dickson, S Turenne, JB Vogt, JP Bailon Strength of Metals and Alloys(ICSMA 7). 2, 1237-1242, 1985. The study of the characteristics of short extrusions ...
S UMMA R Y S&ce the simple equations proposed by Ludwik and Hollomon do not 9ire an adequate desc... more S UMMA R Y S&ce the simple equations proposed by Ludwik and Hollomon do not 9ire an adequate description of the stress-strain curves for Armco iron at room temperature, a new equation has been developed to fit the experimental data. In this new equation, there are parameters whose variation with grain size parallels that of similar parameters in the Hall-Petch relation for the lower yieM stress. Furnace cooled specimens and specimens quenched from 72f C show the same work-hardenin9 behavi-our. This result implies the same mechanisms in both cases and experiments on the stress-dependence of dislocation density support this conclusion. Makin9 use of the dislocation density data in the analyses of the stress-strain curves and the Hall-Petch relation the authors show that in furnace cooled specimens the Liiders band propagates by the nucleation qf fresh dislocations from sources at the 9rain boundaries. RESUME A tempkrature ambiante, la courbe de traction dufer Armco ne peut Ytre dOcrite par une Oquation unique telle que celles propos&s par Ludwik et Hollomon. A partir des rksultats exp&imentaux, les auteurs ont donc dOvelopp~ une nouvelle Oquation qui lie la contrainte plastique et la dkformation plastique et qui est unique pour le domaine de dfformation OtudiO.
Materials Science and Engineering, 1983
Variations in stress corrosion cracking (SCC) velocities after the introduction of several drops ... more Variations in stress corrosion cracking (SCC) velocities after the introduction of several drops of 3.5% NaCl solution into the crack mouth were followed using acoustic emission. It is suggested that studies of the factors influencing this variation may prove a useful method of studying the processes which control SCC kinetics.
Cyclic stress-strain curves for the saturated or quasi-saturated state during tests on polycrysta... more Cyclic stress-strain curves for the saturated or quasi-saturated state during tests on polycrystalline 70Cu-3OZn ~ brass showed a grainsize-dependent plateau for intermediate plastic strain amplitudes. This plateau was associated with the spread of pronounced slip bands (in which relatively strong recovery had occurred) across grain boundaries.
ABSTRACT Silver and Ag-W (10 weight percent W) were operated in a 5.I-A (peak) 308-V (peak) full-... more ABSTRACT Silver and Ag-W (10 weight percent W) were operated in a 5.I-A (peak) 308-V (peak) full-wave rectified dc circuit. The experimental switching system was operated 1.5 times per minute; the opening and closing velocities were 4 x 10-2 and 3 x 10-4 cm/s, respectively; the fully open contact spacing was 200 µm; and the contacts were closed for 3 s. The opening and closing of the contacts were controlled by a heater-bimetal combination attached to the moving contact. The following contact pairs were used: Ag versus Ag, Ag-W versus Ag-W and Ag versus Ag-W. All combinations of contact material and contact polarity were used. The experimental results showed that there was always a net transfer of contact material from the cathode to the anode. The volume of material transferred was strongly dependent upon whether the anode was the moving (hotter) or the fixed (cooler) contact: the greater erosion occurring when the anode was the hotter contact. For Ag versus Ag contacts thc erosion pattern resulted inone pip on the anode and one crater on the cathode. For Ag-W versus AgW contacts the presence of the small percentage of W resulted in multiple pip and crater formations. The experiments with the Ag versus Ag-W showed that the cathode electrode material determined the erosion pattern observed, i.e., when the Ag-W was the cathode, multiple pip and crater'formations occurred, but when Ag was the cathode, only a single pip and crater structure was observed. The presence of the W either in the cathode or in the anode decreased the observed erosion. These experimental results are discussed in terms of how the presence of W affects the emission characteristics of the cathode region and also affects the movement of the arc roots.
Engineering Fracture Mechanics, 1989
ABSTRACT Experiments were carried out on an AISI-SAE 1005 mild steel at 298, 233 and 173 K with R... more ABSTRACT Experiments were carried out on an AISI-SAE 1005 mild steel at 298, 233 and 173 K with R-ratios of 0.1, 0.3 and 0.5 to verify the influence of cleavage or cyclic cleavage on the macroscopic fatigue crack growth rate, . Cleavage during fatigue occurred at 233 and 173 K as quite uniformly distributed patches within a ductile (striated) fracture surface. The amount of cleavage during fatigue propagation increased as the temperature and as the R-ratio decreased and, at a given temperature, was determined primarily by the ΔK value. The influence of this cleavage on the macroscopic value of was analysed through its influence on the crack tip opening displacement, employing the model of the semi-cohesive plastic zone developed in part I. This model was shown to explain satisfactorily the behavior observed.
Materials Science and Engineering: A, 1994
Fatigue crack growth tests under constant-amplitude loading conditions in air and in vacuum have ... more Fatigue crack growth tests under constant-amplitude loading conditions in air and in vacuum have been carried out in the moderate growth rate regime. The fracture surfaces were examined at low and high magnifications in a scanning electron microscope to identify the different fractographic features. An etchant that attacks the basal crystallographic planes preferentially was used to elucidate the cracking crystallography. The results obtained show that large facets lying in or close to { 111} planes are found in air at low R ratio and in vacuum at both the R ratios studied. These facets are formed by micro-void coalescence as shown by the presence of dimples. The other fractographic features identified are pseudointergranular facets, the formation of herringbone patterns and the formation of pseudo-striations. These features are found only in air. Different mechanisms are proposed to explain the observed cracking modes.
Engineering Fracture Mechanics, 1981
ABSTRACT Acoustic emission was obtained during fatigue crack propagation in a D6 tool steel and a... more ABSTRACT Acoustic emission was obtained during fatigue crack propagation in a D6 tool steel and a 1015 mild steel using two different load ratios, R. It was found that the slope of the acoustic emission count rate vs stress intensity factor was higher when R = 0.2 than when R = 0.4. These results are described in terms of several models of acoustic emission mechanisms available in the literature as well as by a proposed new model. It is concluded that the observed R dependence can be explained by the combination of the contribution of two different models. These two models are the new plastic yielding as well as the crack tip fracture processes.
Acta Metallurgica, 1971
Les boulets de broyage utilisés dans l'industrie minière pour la transformation de la roche en fi... more Les boulets de broyage utilisés dans l'industrie minière pour la transformation de la roche en fine sont soumis à des conditions très sévères et complexes. L'usure abrasive et les chocs répétés sont les causes essentielles de leurs dégradations. Pour répondre aux exigences mécaniques et technologiques, ces boulets sont fabriqués en fonte fortement alliée au chrome (10 à 13% de chrome). En effet, le secteur du ciment utilise des boulets de broyage fabriqués par la fonderie de Tiaret. Durant leur utilisation, ces boulets ont montré des performances inférieures; notamment, ils présentent un taux élevé de casse lié à une mauvaise résistance aux chocs et à l'usure. Dans l'objectif d'identifier les causes de ce problème et d'optimiser le traitement thermique adéquat pour réduire la fragilité de ces boulets en vue de parvenir à une amélioration des propriétés mécaniques, on se propose d'effectuer une série de traitements thermiques d'austénitisation à la température de 1050°C avec un temps de maintien de 5 heures, refroidis à l'eau et suivis de revenus à différentes températures de 500°C, 525°C, 550°C et 575°C pendant un temps de maintien de 5 heures. Pour ce faire, une fonte fortement alliée au chrome à l'état brut de coulé fournie par la fonderie de Tiaret, utilisée dans la fabrication des boulets de broyage, a été étudiée en effectuant une caractérisation structurale, microstructurale obtenue par MEB, microanalyse EDAX, DRX et mécanique basée sur les tests d'usure et de résilience. Les résultats obtenus ont montré la présence des carbures de type M 7 C 3 pour tous les traitements thermiques réalisés. Le traitement d'austénitisation à 1050°C offre des duretés élevées de l'ordre de 966 HV et les spectres de diffraction ont révélé que les intensités des pics correspondant à l'austénite résiduelle sont nettement inférieures à ceux de la martensite. En outre, le spectre révèle la présence d'un autre carbure de type M 2 C. La diminution de la dureté après revenu pour l'ensemble des échantillons traités pourrait s'expliquer par la précipitation de carbures de type M 2 C qui entraîne un appauvrissement en carbone de la solution solide tout en relaxant les contraintes résiduelles. Par ailleurs, ces carbures M 2 C renforcent la dureté superficielle tout en maintenant le coeur de la pièce malléable ce qui favorise ainsi la résistance aux chocs. L'échantillon, ayant subi un revenu à 525°C pendant 5 heures, présente une meilleure résistance à l'usure et aux chocs.
Engineering Fracture Mechanics, 1987
... From this result and a generalization of Irwin's principle to V-notch singularities, a g... more ... From this result and a generalization of Irwin's principle to V-notch singularities, a general formulation of the endurance limit of V-notched members was derived. ... Int. S. Mech. Sci. 20, 201-206 (1978). [2] MH El Haddad, KN Smith and TH Topper, A strain-based intensity factor ...
Materials Science and Engineering: A, 1989
The fractography of transgranular stress corrosion cracking (TSCC) of annealed 316 stainless stee... more The fractography of transgranular stress corrosion cracking (TSCC) of annealed 316 stainless steel (s.s.) tested in boiling MgCL solution at 154 °C was studied, with particular attention paid to the crystallography of cracking and to the influence of the stress intensity factor K. Etch-pitting and stereographic observations were employed in order to determine the cracking crystallography. At low K values, cracking occurred predominantly on {100} planes with preferential propagation in a (110) direction. This crystallography and the fractographic features observed are consistent with the crack path alternating microscopically between two sets of {111} planes. Regions of {100}(100) crack propagation were also observed and were consistent with cracking occurring microscopically on four sets of {111} planes. This latter cracking crystallography was often associated with herringbone and fan-shaped patterns of river lines. The latter patterns occurred especially at intermediate K values and were related to the relative ease of crack propagation within grains and across grain boundaries. At high K values, feather-like and sheet-like microfractographic features were generally observed and were shown to result from quite large decohesion steps on different sets of {111} planes. The variation in fractographic details with K was consistent with the number of {111} planes on which cracking occurred and with the size of the decohesion steps on the individual planes. The observations also indicated that the microscopic crack path followed planes on which localized slip had occurred," however, these observations did not permit complete identification of the crack propagation mechanism. The strong similarity between the fractography of TSCC of 316 s.s. and of near-threshold fatigue cracking is discussed, as is the role of the fracture of river lines in influencing the fractographic features.
Canadian Metallurgical Quarterly, 1980
Materials Science and Engineering, 1985
The presence of fine striations (0.2-0.4 pm spacing) on fracture surfaces of aluminium alloy 7075... more The presence of fine striations (0.2-0.4 pm spacing) on fracture surfaces of aluminium alloy 7075-T651 produced by stress corrosion cracking in air as well as the characteristics of the acoustic emission during stress corrosion cracking in air and in 3.5% NaCl solution indicate that the stress corrosion crack advances by small discrete crack jumps.
Canadian Metallurgical Quarterly, 1984
ABSTRACT The corrosion-fatigue behaviour, as typified by the crack propagation rate-cyclic stress... more ABSTRACT The corrosion-fatigue behaviour, as typified by the crack propagation rate-cyclic stress intensity factor relationship, was studied for KCR 171 austenitic - ferritic stainless steel in simulated white water (pH = 4.5) under different conditions and compared to result s obtained in air at 25°C. In white water, increasing the temperature from 20 to 90°C (at a frequency of 1Hz) or decreasing the frequency from 5 to 0.1 Hz (a t 50°C) results in a significant increase in the crack propagation rate for ΔK values between 10 and 40 MPa.m 1/2. This increase in the crack velocity during this corrosion-fatigue is associated with an embrittlement of the ferritic phase, which different fractographic aspects suggest is caused by hydrogen embrittlement. Résumé Le comportement en fatigue- corrosion de l'acier austéno-ferritique KCR 171, a été étudié par mesure de la vitesse de propagat ion da/dN en fonction du facteur d'inte nsité de contrainte ΔK sous diverses conditions expérirnentales. L'état de référence est celui du comportement dan s l'air à 25°C. Dan s l'eau blanche (pH = 4,5) une augmentation de la température de 20 à 90°C (à fréquence constante égale à 1 Hz) ou une diminution de la fréquence de 5 à 0,1Hz (à température constante égale à 50°C) on t pour conséquence, une augmentation notable de la vitesse de fissuration pour des valeurs de ΔK comprises entre 10 et 40 MPa. m 1/2. Cette augmentation de la vitesse de fissuration est due à une fragilisation de la phase ferritique. Les aspects par ticuliers de l'étude fractographique permettent de conclure que la fragilisation de la phase ferritique est probablement due à une fragilisation par l'hydrogène.
Revue de chirurgie orthopédique et réparatrice de l'appareil moteur, 1979
Recent clinical and experimental results in the prosthetic replacement of the anterior cruciate l... more Recent clinical and experimental results in the prosthetic replacement of the anterior cruciate ligament are minimal and this fact has incited us to search for additional fundamental characteristics of natural and synthetic ligaments. The dissection of over 30 human knees (5 fresh and 27 embalmed specimens), of 50 dog knees and of 20 cat knees showed that the posterior cruciate ligament was longer and of bigger size than the anterior cruciate ligament. In dogs, the anatomo-radiological study showed a lenghtening of 14,4 p. 100 for the anterior cruciate and of 10,5 p. 1u0 for the posterior cruciate ligament in the various goniometric positions. Traction with the Instron apparatus using whole knee with preserved bony attachments revealed an elastic resistance (yield point) of the ligament of about 50 kg, 60 kg and 30 kg (for human, dog and cat respectively) with elastic elongation (at the yield stress) of 25 p. 100, 35 p. 100 and 45 p. 100 (respectively). Trials on the polyethylene pr...
Scripta Metallurgica, 1975
In fatigue studies one of the most important parameters ls the threshold stress intensity factor ... more In fatigue studies one of the most important parameters ls the threshold stress intensity factor AK_ below which a crack cannot propagate. A~ may be compared to the endurance limit in ~hler's experiments and allows prediction of whether the propagation of a crack, characterlsed by its length "a" and submitted to a given cyclic stress, can occur. The cycllc stress is characterised by the stress range (Oma x -Omln) , the absolute values oma x and Omi n or by the cyclic stress ratio R=°mln Many authors (1,2,3) have introduced AK T in the emplrleal relationships giving the dependence of the propagation rate da~n of the crack on the stress intensity factor AK~na x -Kml n . In recent years, some authors (4) have paid spealal attention to the dependance of AK on R and on the microstructural parameters of material. T Klesnil and Lukas (3) have prevlously proposed an empirical relatlonshlp:
While the influence of strain-aging on the endurance limit and on the dislocation behaviour durin... more While the influence of strain-aging on the endurance limit and on the dislocation behaviour during cyclic deformation has received some attention in the literature, almost no attention appears to have been paid to the influence of strain aging on fatigue crack propagation. An influence of strain aging on fatigue propagation can be expected to manifest itself most clearly at the