https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Fri, 10 Apr 2026 09:25:52 GMT 2026-04-10T09:25:52Z http://hdl.handle.net/10985/7883 Performance impact of honing dynamics on surface finish of precoated cylinder bores GOELDEL, Benoit; SABRI, Leila; EL MANSORI, Mohamed The surface modification of engine cylinder bores with improved sliding properties is often produced by the honing process. This multi-stage process is performed using abrasive stones loaded against the bore with simultaneous rotation and oscillation. To guarantee this process robustness with acceptable dimensional accuracy and surface quality, the stone dynamic effects in continuous balanced contact with the workpiece have to studied deeply. This paper highlights these effects on honed surface textures. The stone dynamic behavior was studied at conventional regime ranged from 0,5g to 1,5g as often used in mass production. In this range, the dimensional accuracy is ensured by opposition to the surface appearance. However, higher accelerations up to 2,5g improve simultaneously the form quality (especially straightness) and reduces the cycle time. This work shows, at least, that the bore surface finish can be dynamically controlled while honing. This technology is enabled by a micro scale regeneration mechanism of abrasive stones. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/7883 2013-01-01T00:00:00Z GOELDEL, Benoit SABRI, Leila EL MANSORI, Mohamed The surface modification of engine cylinder bores with improved sliding properties is often produced by the honing process. This multi-stage process is performed using abrasive stones loaded against the bore with simultaneous rotation and oscillation. To guarantee this process robustness with acceptable dimensional accuracy and surface quality, the stone dynamic effects in continuous balanced contact with the workpiece have to studied deeply. This paper highlights these effects on honed surface textures. The stone dynamic behavior was studied at conventional regime ranged from 0,5g to 1,5g as often used in mass production. In this range, the dimensional accuracy is ensured by opposition to the surface appearance. However, higher accelerations up to 2,5g improve simultaneously the form quality (especially straightness) and reduces the cycle time. This work shows, at least, that the bore surface finish can be dynamically controlled while honing. This technology is enabled by a micro scale regeneration mechanism of abrasive stones. http://hdl.handle.net/10985/8628 Influence de l'échelle de rugosité sur le frottement dans les contacts lubrifiés. MEZGHANI, Sabeur; YOUSFI, Mohammed; ZAHOUANI, Hassan; EL MANSORI, Mohamed; DEMIRCI, Ibrahim The reduction of friction and the limitation of emissions of greenhouse gases are the main objectives of the automotive industry. This energy e ciency is related to functionalization of the surface of ringpack tribo-system. Multi-stage abrasive nishing process are commonly used to produce the geometrical properties of a surface. This confers technical some functionalities in the operating characteristics relating to their durability and reliability. The texture generated signi cantly a ects the performance of the ring-pack system. In this paper, a numerical model of elasto-hydrodynamic (EHD) contact coupled to a multiscale surface texture modeling was developed. This permtis to to study the scale e ect of surface features and theirs interactions on friction performance and lubricant ow under hydrodynamic lubrication condition. Surface topography can be decomposed in two principal components : super cial roughness modeled using fractal model and valleys modeled by scaling factor. Results show Relationship between friction and surface scales. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/8628 2013-01-01T00:00:00Z MEZGHANI, Sabeur YOUSFI, Mohammed ZAHOUANI, Hassan EL MANSORI, Mohamed DEMIRCI, Ibrahim The reduction of friction and the limitation of emissions of greenhouse gases are the main objectives of the automotive industry. This energy e ciency is related to functionalization of the surface of ringpack tribo-system. Multi-stage abrasive nishing process are commonly used to produce the geometrical properties of a surface. This confers technical some functionalities in the operating characteristics relating to their durability and reliability. The texture generated signi cantly a ects the performance of the ring-pack system. In this paper, a numerical model of elasto-hydrodynamic (EHD) contact coupled to a multiscale surface texture modeling was developed. This permtis to to study the scale e ect of surface features and theirs interactions on friction performance and lubricant ow under hydrodynamic lubrication condition. Surface topography can be decomposed in two principal components : super cial roughness modeled using fractal model and valleys modeled by scaling factor. Results show Relationship between friction and surface scales. http://hdl.handle.net/10985/9879 Modélisation du Procédé de Superfinition par Abrasion BIGERELLE, Maxence; GUILLEMOT, Gildas; HAGEGE, Benjamin; SABER, Oufae; IOST, Alain; EL MANSORI, Mohamed Le papier actuel présente une tentative de technologie pour modéliser rigoureusement une surface fonctionnelle (surface de cône de pignon intermédiaire) selon ses caractéristiques de finition. La surface virtuelle d'entrée est produite par une fonction originale fractale qui reproduit la « signature » extérieure due au processus de meulage. Pour modeler l'opération de superfinition un algorithme simulant les conditions de polissage abrasives est développé et appliqué pour modifier la surface initiale fractale. L'idée fondamentale de ce modèle est que plus la taille d'une crête du profil est haute, moins est importante sa probabilité de résistance pendant un cycle d'abrasion. Le procédé de finissage de ceinture est par conséquent modélisé par cinq paramètres : deux paramètres qui caractérisent l'extérieur initial (dimension fractale et amplitude) et trois paramètres décrivant le processus de polissage d'abrasion (probabilité de résistance, volume d'usure et nombre des cycles d'abrasion). Afin de s'assurer que le composant sera fabriqué selon les caractéristiques exigées, les paramètres du modèle doivent être déterminés. À cet effet, une fonctionnelle avec une méthode d'optimisation est créée. Cette simulation fournit la morphologie de la surface initiale et comment régler le processus de superfinition pour obtenir la fonctionnalité de la surface. On exige une rugosité initiale élevée dont l'érosion soit lente pour conserver quelques vallées du profil initial (réservoirs de lubrifiant). Mon, 01 Jan 2007 00:00:00 GMT http://hdl.handle.net/10985/9879 2007-01-01T00:00:00Z BIGERELLE, Maxence GUILLEMOT, Gildas HAGEGE, Benjamin SABER, Oufae IOST, Alain EL MANSORI, Mohamed Le papier actuel présente une tentative de technologie pour modéliser rigoureusement une surface fonctionnelle (surface de cône de pignon intermédiaire) selon ses caractéristiques de finition. La surface virtuelle d'entrée est produite par une fonction originale fractale qui reproduit la « signature » extérieure due au processus de meulage. Pour modeler l'opération de superfinition un algorithme simulant les conditions de polissage abrasives est développé et appliqué pour modifier la surface initiale fractale. L'idée fondamentale de ce modèle est que plus la taille d'une crête du profil est haute, moins est importante sa probabilité de résistance pendant un cycle d'abrasion. Le procédé de finissage de ceinture est par conséquent modélisé par cinq paramètres : deux paramètres qui caractérisent l'extérieur initial (dimension fractale et amplitude) et trois paramètres décrivant le processus de polissage d'abrasion (probabilité de résistance, volume d'usure et nombre des cycles d'abrasion). Afin de s'assurer que le composant sera fabriqué selon les caractéristiques exigées, les paramètres du modèle doivent être déterminés. À cet effet, une fonctionnelle avec une méthode d'optimisation est créée. Cette simulation fournit la morphologie de la surface initiale et comment régler le processus de superfinition pour obtenir la fonctionnalité de la surface. On exige une rugosité initiale élevée dont l'érosion soit lente pour conserver quelques vallées du profil initial (réservoirs de lubrifiant). http://hdl.handle.net/10985/10168 Mesure de la Pertinence de la Physique Multi-échelle Génie Logiciel et Mesures Statistiques Projet CETIM IOST, Alain; ZAHOUANI, Hassan; ANSELME, Karine; NAJJAR, Denis; GUILLEMOT, Gildas; HAGEGE, Benjamin; JOURANI, Abdeljalil; REVEL, Phllippe; MAZERAN, Pierre-Emmanuel; BIGERELLE, Maxence; EL MANSORI, Mohamed; COOREVITS, Thierry L'objet principal des études en morphologie des surfaces consiste à résumer l'information de manière optimale. Dans nos études, nous étudions plus particulièrement la signification physique, les méthodes numériques et les artefacts numériques du calcul de la dimension fractale. Le problème fondamental est de répondre à la question suivante "La dimension fractale est-elle un paramètre pertinent et à quelle échelle ?" Cette question n'a aucun sens s’il n’est pas précisé « pertinent vis à vis de quels processus physiques ». Illustrons ce propos par un exemple de caractérisation de surface par mesure de rugosité : p échantillons d'un matériau ont subi différents mécanismes d'usure. n mesures de rugosité sont effectuées sur chaque échantillon (un raisonnement analogue serait applicable à la caractérisation de surface par analyse d'images). Disposant alors des mesures de rugosité, l'usage courant est d’en déduire quelques paramètres (par exemple, le Ra, Rt, Rq, etc...). Nous recherchons une corrélation entre ces quelques paramètres et les différents mécanismes d'usure. Par exemple, il peut être d'usage dans une catégorie professionnelle d'utiliser un paramètre particulier de rugosité (souvent le Ra ou le Rt) et d’analyser les relations de ce paramètre avec le phénomène d’usure puis de déduire éventuellement des caractéristiques tribologiques du matériau. Cependant, si un autre paramètre permet de mieux caractériser la surface vis à vis du phénomène d’usure, les conclusions de l’analyse doivent être nuancées, voire même différentes. De même, il est d'usage très fréquent, dans la communauté scientifique, de retenir le paramètre de morphologie de surface qui possède une interprétation physique connue (le Rq d'unesurface caractérise les phénomènes de brillance). Cependant s’il est montré expérimentalement qu'un autre paramètre de rugosité caractérise mieux le phénomène physique, alors son caractère discriminant doit être justifié. Mon, 01 Jan 2007 00:00:00 GMT http://hdl.handle.net/10985/10168 2007-01-01T00:00:00Z IOST, Alain ZAHOUANI, Hassan ANSELME, Karine NAJJAR, Denis GUILLEMOT, Gildas HAGEGE, Benjamin JOURANI, Abdeljalil REVEL, Phllippe MAZERAN, Pierre-Emmanuel BIGERELLE, Maxence EL MANSORI, Mohamed COOREVITS, Thierry L'objet principal des études en morphologie des surfaces consiste à résumer l'information de manière optimale. Dans nos études, nous étudions plus particulièrement la signification physique, les méthodes numériques et les artefacts numériques du calcul de la dimension fractale. Le problème fondamental est de répondre à la question suivante "La dimension fractale est-elle un paramètre pertinent et à quelle échelle ?" Cette question n'a aucun sens s’il n’est pas précisé « pertinent vis à vis de quels processus physiques ». Illustrons ce propos par un exemple de caractérisation de surface par mesure de rugosité : p échantillons d'un matériau ont subi différents mécanismes d'usure. n mesures de rugosité sont effectuées sur chaque échantillon (un raisonnement analogue serait applicable à la caractérisation de surface par analyse d'images). Disposant alors des mesures de rugosité, l'usage courant est d’en déduire quelques paramètres (par exemple, le Ra, Rt, Rq, etc...). Nous recherchons une corrélation entre ces quelques paramètres et les différents mécanismes d'usure. Par exemple, il peut être d'usage dans une catégorie professionnelle d'utiliser un paramètre particulier de rugosité (souvent le Ra ou le Rt) et d’analyser les relations de ce paramètre avec le phénomène d’usure puis de déduire éventuellement des caractéristiques tribologiques du matériau. Cependant, si un autre paramètre permet de mieux caractériser la surface vis à vis du phénomène d’usure, les conclusions de l’analyse doivent être nuancées, voire même différentes. De même, il est d'usage très fréquent, dans la communauté scientifique, de retenir le paramètre de morphologie de surface qui possède une interprétation physique connue (le Rq d'unesurface caractérise les phénomènes de brillance). Cependant s’il est montré expérimentalement qu'un autre paramètre de rugosité caractérise mieux le phénomène physique, alors son caractère discriminant doit être justifié. http://hdl.handle.net/10985/7476 On Material Removal Regimes for the Shaping of Glass Edges: Force Analysis, Surface Topography and Damage Mechanisms MEZGHANI, Sabeur; EL MANSORI, Mohamed; DEMIRCI, Ibrahim Glass shaping, which corresponds to the removal of the edges of a specimen, is the last finishing operation in glass manufacturing. This process has several functions on the final shaped glass including removing sharp edges, improving mechanical resistance, decreasing surface damage and giving it an aesthetical aspect. This article addresses the effects of working parameters, including grinding forces and consumed power, on surface edge finishing and damage mechanism induced during glass grinding. Microscopic observations and multi-scale analysis have also been conducted to investigate the surface edge characteristics. Experimental results show three damage regimes. The first (regime I) is a partial ductile regime with cutting action accompanied by chip formation. The second (regime II) is a crushing (or fragmentation) regime. The last (regime III) is also a partial ductile regime but by ploughing action with displaced material. The shaped surface obtained in the regime II has a better roughness than that obtained in regime I and III. However, regimes I and III include streaks and form defects which are not present in regime II. Similar to metallic materials, the evolution of force components show a linear relationship between normal and tangential forces. This implicates a constant average contact pressure and friction coefficient (l) between the flat grains and the workpiece. Tue, 01 Jan 2008 00:00:00 GMT http://hdl.handle.net/10985/7476 2008-01-01T00:00:00Z MEZGHANI, Sabeur EL MANSORI, Mohamed DEMIRCI, Ibrahim Glass shaping, which corresponds to the removal of the edges of a specimen, is the last finishing operation in glass manufacturing. This process has several functions on the final shaped glass including removing sharp edges, improving mechanical resistance, decreasing surface damage and giving it an aesthetical aspect. This article addresses the effects of working parameters, including grinding forces and consumed power, on surface edge finishing and damage mechanism induced during glass grinding. Microscopic observations and multi-scale analysis have also been conducted to investigate the surface edge characteristics. Experimental results show three damage regimes. The first (regime I) is a partial ductile regime with cutting action accompanied by chip formation. The second (regime II) is a crushing (or fragmentation) regime. The last (regime III) is also a partial ductile regime but by ploughing action with displaced material. The shaped surface obtained in the regime II has a better roughness than that obtained in regime I and III. However, regimes I and III include streaks and form defects which are not present in regime II. Similar to metallic materials, the evolution of force components show a linear relationship between normal and tangential forces. This implicates a constant average contact pressure and friction coefficient (l) between the flat grains and the workpiece. http://hdl.handle.net/10985/7621 Running-in wear modeling of honed surface for combustion engine cylinder liners MEZGHANI, Sabeur; YOUSFI, Mohammed; EL MANSORI, Mohamed; DEMIRCI, Ibrahim The texture change during running-in alters the performance and efficiency of a tribo-mechanical system. During mass production of cylinder liners, a final finishing stage known as ‘‘plateau honing’’ is commonly added to reduce the running-in wear process of the liner surface. The majority of researchers think that this operation improves the engine efficiency and decreases oil consumption. It was believed that there are close links between the surface topography of honed cylinders change and their wear resistance during running-in. However, these interactions have not yet been established. Some running-in wear models were developed in the open literature to predict topographical surface changes without considering the running-in conditions. The present paper thus investigates the various aspects of the wear modeling that caused running- in problems in honed surfaces and its implications on ring-pack friction performance. To illustrate this, plateau honing experiments under different conditions were first carried out on an instrumented vertical honing machine. The plateau honing experiments characterize the surface modifications during running-in wear of cast-iron engine bores using advanced characterization method. Based on the experimental evidence, a running-in wear model was developed. Finally, a numerical extension of the developed model was applied to solve the Reynolds equation by taking into account the real surface topographies of the engine bore. This enables us to predict realistic friction performance within the cylinder ring-pack tribosystem. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/7621 2013-01-01T00:00:00Z MEZGHANI, Sabeur YOUSFI, Mohammed EL MANSORI, Mohamed DEMIRCI, Ibrahim The texture change during running-in alters the performance and efficiency of a tribo-mechanical system. During mass production of cylinder liners, a final finishing stage known as ‘‘plateau honing’’ is commonly added to reduce the running-in wear process of the liner surface. The majority of researchers think that this operation improves the engine efficiency and decreases oil consumption. It was believed that there are close links between the surface topography of honed cylinders change and their wear resistance during running-in. However, these interactions have not yet been established. Some running-in wear models were developed in the open literature to predict topographical surface changes without considering the running-in conditions. The present paper thus investigates the various aspects of the wear modeling that caused running- in problems in honed surfaces and its implications on ring-pack friction performance. To illustrate this, plateau honing experiments under different conditions were first carried out on an instrumented vertical honing machine. The plateau honing experiments characterize the surface modifications during running-in wear of cast-iron engine bores using advanced characterization method. Based on the experimental evidence, a running-in wear model was developed. Finally, a numerical extension of the developed model was applied to solve the Reynolds equation by taking into account the real surface topographies of the engine bore. This enables us to predict realistic friction performance within the cylinder ring-pack tribosystem. http://hdl.handle.net/10985/7575 Mutual influence of cross hatch angle and superficial roughness of honed surfaces on friction in ring-pack tribo-system MEZGHANI, Sabeur; YOUSFI, Mohammed; EL MANSORI, Mohamed; DEMIRCI, Ibrahim The cylinder bore surface texture, widely produced by the honing technique, is an essential factor for a good engine performance (friction, oil consumption, running-in, wear etc.). This explains the improvement and development of various new honing techniques. These different honing processes generate surfaces with various texture features characteristics (roughness, valleys depth, cross hatch angle, etc.). This paper addresses a comparison of ring-pack friction for cylinder surfaces produced by plateau honing and helical slide honing. It takes in consideration the mutual effect of superficial plateau roughness amplitude and honing angle. A numerical model is developed to predict friction within the cylinder ring-pack system in mixed lubrication regime. The results show the effectiveness of helical slide honed surface texture in comparison to plateau honed bore surfaces Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/7575 2013-01-01T00:00:00Z MEZGHANI, Sabeur YOUSFI, Mohammed EL MANSORI, Mohamed DEMIRCI, Ibrahim The cylinder bore surface texture, widely produced by the honing technique, is an essential factor for a good engine performance (friction, oil consumption, running-in, wear etc.). This explains the improvement and development of various new honing techniques. These different honing processes generate surfaces with various texture features characteristics (roughness, valleys depth, cross hatch angle, etc.). This paper addresses a comparison of ring-pack friction for cylinder surfaces produced by plateau honing and helical slide honing. It takes in consideration the mutual effect of superficial plateau roughness amplitude and honing angle. A numerical model is developed to predict friction within the cylinder ring-pack system in mixed lubrication regime. The results show the effectiveness of helical slide honed surface texture in comparison to plateau honed bore surfaces http://hdl.handle.net/10985/9731 Effects of working parameters on the surface roughness in belt grinding process: the size-scale estimation influence VAN GORP, Adrien; BIGERELLE, Maxence; GHIDOSSI, Patrick; IOST, Alain; EL MANSORI, Mohamed This paper outlines a new method to evaluate roughness parameters considering the scale used for their evaluation. Application is performed for grinding hardened steel with abrasive belts. Seven working variables are considered through a two-level experimental design. For all configurations, 30 surface profiles were recorded by tactile profilometry and rectified by a first degree B-spline fitting before calculating a set of current roughness parameters. The relevancy of each roughness parameter, to highlight process parameters influence, is then estimated for each scale by variance analysis. The results show that each influent input parameter is characterised by a related relevant evaluation length. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/10985/9731 2010-01-01T00:00:00Z VAN GORP, Adrien BIGERELLE, Maxence GHIDOSSI, Patrick IOST, Alain EL MANSORI, Mohamed This paper outlines a new method to evaluate roughness parameters considering the scale used for their evaluation. Application is performed for grinding hardened steel with abrasive belts. Seven working variables are considered through a two-level experimental design. For all configurations, 30 surface profiles were recorded by tactile profilometry and rectified by a first degree B-spline fitting before calculating a set of current roughness parameters. The relevancy of each roughness parameter, to highlight process parameters influence, is then estimated for each scale by variance analysis. The results show that each influent input parameter is characterised by a related relevant evaluation length. http://hdl.handle.net/10985/9719 Fiber type effect on tribological behavior when cutting natural fiber reinforced plastics MEZGHANI, Sabeur; EL MANSORI, Mohamed; CHEGDANI, Faissal Recently, natural fiber reinforced plastic (NFRP) materials are becoming a viable alternative to synthetic fiber in many industrial applications which not require high structural performances. However, machining of NFRP such as milling process is almost unavoidable operation to facilitate the parts assembly in addition to the finishing of final products. The present study thus focused on the influence of natural fiber types on tribological behavior during profile milling process. Three types of short natural fibers (bamboo, sisal and miscanthus) reinforced polypropylene (PP) composites are investigated. The quality of NFRP machined surface is quantified using a multiscale analysis based on wavelets decomposition. The natural fiber effect related to the machined surface quality is hence identified at all scales from roughness to waviness. The bamboo fibers reinforced plastics which exhibit high contact stiffness shows the smoother surface finish after machining. Therefore, the multiscale surface roughness is used as descriptor of natural fiber influence on the machining mechanisms and to establish the cutting signature of NFRP materials. The authors acknowledge the urban community of Châlonsen Champagne(Cités en Champagne) for their financial support. The authors also wish to thank “AD majoris SAS France” for providing the NFRP samples used in this research. Thu, 01 Jan 2015 00:00:00 GMT http://hdl.handle.net/10985/9719 2015-01-01T00:00:00Z MEZGHANI, Sabeur EL MANSORI, Mohamed CHEGDANI, Faissal Recently, natural fiber reinforced plastic (NFRP) materials are becoming a viable alternative to synthetic fiber in many industrial applications which not require high structural performances. However, machining of NFRP such as milling process is almost unavoidable operation to facilitate the parts assembly in addition to the finishing of final products. The present study thus focused on the influence of natural fiber types on tribological behavior during profile milling process. Three types of short natural fibers (bamboo, sisal and miscanthus) reinforced polypropylene (PP) composites are investigated. The quality of NFRP machined surface is quantified using a multiscale analysis based on wavelets decomposition. The natural fiber effect related to the machined surface quality is hence identified at all scales from roughness to waviness. The bamboo fibers reinforced plastics which exhibit high contact stiffness shows the smoother surface finish after machining. Therefore, the multiscale surface roughness is used as descriptor of natural fiber influence on the machining mechanisms and to establish the cutting signature of NFRP materials. http://hdl.handle.net/10985/8634 Experimental study of the brittle–ductile transition in hot cutting of SG iron specimens FOUILLAND-PAILLE, Laurence; EL MANSORI, Mohamed The present paper investigates the brittle-ductile transition (BDT) of the primary shear zone during cutting of spheroidal graphite (SG) iron in the austenitization temperature range (around 1000 °C). The experimental tests were performed using a cutting test bench in the cutting speed range of 0.8 to 1.6m.s-1. The cut surfaces were studied using optical microscopy and Scanning Electron Microscope (SEM) analysis techniques. The obtained results revealed either consequent deep fractured regions governed by a brittle-cracking regime (BCR) or a crack-free cut surface governed by a ductile-shear regime (DSR) with large plastic deformations. When cutting data were discussed with respect to the influences of cutting parameters and obtained cut surface, the correlation is significantly rich. Both cut surface integrity, cutting force curves and metallographic results show a BDT indicating a change in the dominating hot cutting process mechanism. Such a transition is associated with the dynamic recrystallization promoting strain softening and hot cutting by ductile shearing. http://www.sciencedirect.com/science/article/pii/S0924013612002579 Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/8634 2013-01-01T00:00:00Z FOUILLAND-PAILLE, Laurence EL MANSORI, Mohamed The present paper investigates the brittle-ductile transition (BDT) of the primary shear zone during cutting of spheroidal graphite (SG) iron in the austenitization temperature range (around 1000 °C). The experimental tests were performed using a cutting test bench in the cutting speed range of 0.8 to 1.6m.s-1. The cut surfaces were studied using optical microscopy and Scanning Electron Microscope (SEM) analysis techniques. The obtained results revealed either consequent deep fractured regions governed by a brittle-cracking regime (BCR) or a crack-free cut surface governed by a ductile-shear regime (DSR) with large plastic deformations. When cutting data were discussed with respect to the influences of cutting parameters and obtained cut surface, the correlation is significantly rich. Both cut surface integrity, cutting force curves and metallographic results show a BDT indicating a change in the dominating hot cutting process mechanism. Such a transition is associated with the dynamic recrystallization promoting strain softening and hot cutting by ductile shearing.