Artificial intelligence modeling of induction contour hardening of 300M steel bar and C45 steel spur-gear

Induction hardening is a heat surface treatment technique widely employed for steel components in order to improve their fatigue life without affecting the metallurgy of the bulk material. The control of the treated components goes through the prediction and the optimization of the induction hardening process parameters. The aim of this work is to propose an approach based on artificial intelligence technique to predict the in-depth hardness profile. For this purpose, experimental tests were first carried out on 300M steel bar and C45 steel spur-gear under single and double frequencies, respectively. Intermediate variables were then generated to be used as input data. Data-driven model based on XGBoost library was finally developed. It was found that the proposed approach predicts with good agreement the hardness profiles and can be used in induction treatment process optimization

Data-Driven Modeling for Multiphysics Parametrized Problems-Application to Induction Hardening Process

Data-driven modeling provides an efficient approach to compute approximate solutions for complex multiphysics parametrized problems such as induction hardening (IH) process. Basically, some physical quantities of interest (QoI) related to the IH process will be evaluated under real-time constraint, without any explicit knowledge of the physical behavior of the system. Hence, computationally expensive finite element models will be replaced by a parametric solution, called metamodel. Two data-driven models for temporal evolution of temperature and austenite phase transformation, during induction heating, were first developed by using the proper orthogonal decomposition based reduced-order model followed by a nonlinear regression method for temperature field and a classification combined with regression for austenite evolution. Then, data-driven and hybrid models were created to predict hardness, after quenching. It is shown that the results of artificial intelligence models are promising and provide good approximations in the low-data limit case

Thermomechanical behavior of C38LTT in the semi-solid state

Semisolid thixoforming is an intermediate process between casting and forging. This process presents several advantages, such as energy efficiency, production rates, smooth die filling, low shrinkage porosity, which together lead to near net shape capability and thus to fewer manufacturing steps than with classical methods. So far, there are only few applications of semisolid processing of higher melting point alloys. Steel is a particularly challenging material to semi-solid process because of the high temperatures involved (about 1410°C). At present, the ability to form steel components in semi-solid state depends on the control of the flow of material during the forming and defects conditions. Semi-solid alloys display thixotropy, which is characterized by time-dependent behavior which drastically changes from a solid like behavior at rest to a liquid like flow when submitted to shear. However, characterizing and modelling such a behaviour for steels is still challenging.   Ascometal has developed the C38LTT (Low Thixoforging Temperature) that is compatible with identified parameters [1] to be suitable for thixoforming: the solidus and liquidus temperatures (TS and TL) have to be as low as possible; the temperature at 50% liquid fraction (T50%) has to be as low as possible; the melting interval (TL-TS) has to be as large as possible; and the slope at 10% and 50% liquid fraction must be as low as possible to ensure a small sensitivity of liquid fraction to temperature.   The aim of the research work was to study the rheological properties of C38LTT. The high temperature range for semi-solid state makes the experiments particularly challenging. An experimental protocol was determined, geometries of specimens, minimize thermal gradients and optical system to improve the precision of measuring temperature (figure1) with a Gleeble simulator to characterize the thermomechanical behaviors.   Uniaxial tensile and compressive tests were carried out on semi-solid specimen having >0.8 solid fraction for different ram speeds and temperatures. The constitutive behavior appears greatly dependent on both fraction solid and strain rate. Furthermore, while the behavior is dominated by the solid phase, the variation in both ductility and stress with temperature has been identified to propose a brittle temperature range and the influence of the temperature on the thermomechanical behavior. Specifically, in tension, a drastic change in ductility with fraction solid/temperature was found in good agreement with some results for aluminum brittle temperature range in literature [2].

Caractérisation et modélisation micromécanique du comportement des alliages métalliques à l’état semi-solide pour la simulation du thixoforgeage des aciers

Semi-solid metals and alloys exhibit a shear thinning behavior characterized by a sharp drop in viscosity with increasing strain rate. This property promotes a smooth die filling during forming. To exploit this advantage, several semi-solid forming process have been developed. Among these processes, we find the thixoforging when the semi-solid state is obtained by a partial remelting from solid state. The solid fraction is above 0.8. Thixoforging of high melting point alloys such as steels is particularly challenging because of about 1400°C temperatures involved. However, previous works showed that this process reveals high potential to reduce material as well as energy consumption. The present PhD thesis is part of a French research project named TACA «Thixoforging of steels for fabrication of automative parts» leaded by IRT-M2P. It aims at industrial development of steel thixoforging for manufacturing automotive components. The mastery and the development of steel thixoforging require a good knowledge of the mechanical behavior of semi-solid steels and appropriate numerical tools to simulate the process. The PhD work aims to (1) characterize the thermomechanical behavior of semi-solid steels and (2) develop constitutive equations that have to be implemented into the commercial code FORGE® to simulate thixoforging. A special attention was paid to the tensile behavior to investigate the temperature range in which the material is very sensitive to hot cracking. Tensile tests provided the temperature from which the material lost its tensile strength and its ductility. Mechanisms leading to the drop of these two properties were identified and were found to be consistent with mechanisms described in literature. A model based on homogenization approach, namely taking explicitly into account the mechanical role of the liquid and solid phases was developed. This model is based on a viscoplastic approach previously developed that was enhanced to (1) include the elastic response of the solid skeleton saturated with liquid and to (2) distinguish the evolution of the spatial liquid/solid distribution according to the tensile or compressive loading path. It successfully describes the three stages of the response in tension: increase, stabilization and decrease of the stress with increasing displacement. The model was implemented in the FORGE® finite element code. The experimental tensile tests were simulated to provide identification of the model parameters. The simulation results showed that strong deformation localization zones were predicted consistently with experiments. Simulations of thixoforging industrial processes such as forging U were studied and compared with experimental results achieved on the Vulcan platform (ENSAM Metz). In addition, a criterion determining the zones without any tensile strength and so sensitive to hot cracking was proposed. Comparison with experimental observations showed that this criterion is an encouraging first approach to predict the brittle zones of thixoforging parts.Les métaux à l’état semi-solide présentent un comportement rhéofluidifiant caractérisé par une forte chute de la viscosité avec la vitesse de déformation facilitant le remplissage des matrices lors de la mise en forme. L’exploitation de ce comportement donne lieu à un procédé de mise en forme appelé « thixoforgeage ». L’état semi-solide est obtenu en refusion partielle à partir de l’état solide et la fraction de solide est supérieure à 0.8. Les plus hautes températures mises en jeu dans le cas des matériaux à haut point de fusion comme les aciers rendent la maîtrise du procédé plus complexe. Cependant, les travaux antérieurs sur le thixoforgeage d’aciers ont montré le potentiel de ce procédé pour réduire la consommation en matière première et en énergie. La thèse s’inscrit dans le cadre du projet TACA «Thixoforgeage d’Aciers pour la fabrication de Composants Automobiles» piloté par l’IRT-M2P. Il ambitionne le développement industriel du thixoforgeage des aciers pour la fabrication de pièces automobiles. La maîtrise et le développement du thixoforgeage nécessite une bonne connaissance du comportement mécanique du matériau à l’état semi-solide et le développement d’outils de simulation numérique adaptés. Ce travail de thèse a pour objectifs de (i) caractériser expérimentalement le comportement thermomécanique des aciers à l’état semi-solide, (ii) développer un modèle de comportement destiné à être implanté dans le logiciel FORGE® pour simuler le thixoforgeage. Une attention particulière a été portée sur le comportement en traction pour caractériser l’intervalle de température dans lequel le matériau devient très sensible à la fissuration à chaud. Des essais en traction menés à différentes températures ont permis de déterminer la température à partir de laquelle la résistance et la ductilité du matériau chutent drastiquement. Les mécanismes conduisant à ces chutes ont été identifiés et sont conformes à ceux décrits dans la littérature. Un modèle basé sur une approche d’homogénéisation qui prend en compte explicitement le rôle mécanique des phases liquide et solide a été développé. Ce modèle repose sur une approche viscoplastique établie antérieurement puis enrichie afin (i) d’intégrer le comportement élastique du squelette solide saturé en liquide et (ii) distinguer les évolutions de distribution spatiale des phases liquide et solide selon le trajet de chargement en traction ou en compression. Il permet de décrire avec succès, pour la première fois, les trois stades de la réponse mécanique en traction (augmentation, stabilisation puis chute de la contrainte en fonction du déplacement). Le modèle a ensuite été implanté dans le code éléments finis FORGE®. Les simulations des essais de traction GLEBBLE ont permis d’identifier les paramètres du modèle. Des comparaisons des résultats expérimentaux et numériques ont permis de reproduire des phénomènes de localisation de la déformation réelle. Après la validation sur des essais de traction, des simulations de procédés de thixoforgeage industriel, tels que le forgeage de U, ont été étudiées et comparées aux résultats expérimentaux réalisés sur la plateforme Vulcain de l'ENSAM de Metz. Un critère permettant de définir des zones sensibles à la fissuration à chaud a été proposé. La comparaison avec des observations expérimentales a montré que ce critère constitue une première approche encourageante pour prédire les zones de fragilité de la pièce en thixoforgeage

Characterizing and micromechanical modelling of metals and alloys in the semi-solid state for thixoforging of steels

Les métaux à l’état semi-solide présentent un comportement rhéofluidifiant caractérisé par une forte chute de la viscosité avec la vitesse de déformation facilitant le remplissage des matrices lors de la mise en forme. L’exploitation de ce comportement donne lieu à un procédé de mise en forme appelé « thixoforgeage ». L’état semi-solide est obtenu en refusion partielle à partir de l’état solide et la fraction de solide est supérieure à 0.8. Les plus hautes températures mises en jeu dans le cas des matériaux à haut point de fusion comme les aciers rendent la maîtrise du procédé plus complexe. Cependant, les travaux antérieurs sur le thixoforgeage d’aciers ont montré le potentiel de ce procédé pour réduire la consommation en matière première et en énergie. La thèse s’inscrit dans le cadre du projet TACA «Thixoforgeage d’Aciers pour la fabrication de Composants Automobiles» piloté par l’IRT-M2P. Il ambitionne le développement industriel du thixoforgeage des aciers pour la fabrication de pièces automobiles. La maîtrise et le développement du thixoforgeage nécessite une bonne connaissance du comportement mécanique du matériau à l’état semi-solide et le développement d’outils de simulation numérique adaptés. Ce travail de thèse a pour objectifs de (i) caractériser expérimentalement le comportement thermomécanique des aciers à l’état semi-solide, (ii) développer un modèle de comportement destiné à être implanté dans le logiciel FORGE® pour simuler le thixoforgeage. Une attention particulière a été portée sur le comportement en traction pour caractériser l’intervalle de température dans lequel le matériau devient très sensible à la fissuration à chaud. Des essais en traction menés à différentes températures ont permis de déterminer la température à partir de laquelle la résistance et la ductilité du matériau chutent drastiquement. Les mécanismes conduisant à ces chutes ont été identifiés et sont conformes à ceux décrits dans la littérature. Un modèle basé sur une approche d’homogénéisation qui prend en compte explicitement le rôle mécanique des phases liquide et solide a été développé. Ce modèle repose sur une approche viscoplastique établie antérieurement puis enrichie afin (i) d’intégrer le comportement élastique du squelette solide saturé en liquide et (ii) distinguer les évolutions de distribution spatiale des phases liquide et solide selon le trajet de chargement en traction ou en compression. Il permet de décrire avec succès, pour la première fois, les trois stades de la réponse mécanique en traction (augmentation, stabilisation puis chute de la contrainte en fonction du déplacement). Le modèle a ensuite été implanté dans le code éléments finis FORGE®. Les simulations des essais de traction GLEBBLE ont permis d’identifier les paramètres du modèle. Des comparaisons des résultats expérimentaux et numériques ont permis de reproduire des phénomènes de localisation de la déformation réelle. Après la validation sur des essais de traction, des simulations de procédés de thixoforgeage industriel, tels que le forgeage de U, ont été étudiées et comparées aux résultats expérimentaux réalisés sur la plateforme Vulcain de l'ENSAM de Metz. Un critère permettant de définir des zones sensibles à la fissuration à chaud a été proposé. La comparaison avec des observations expérimentales a montré que ce critère constitue une première approche encourageante pour prédire les zones de fragilité de la pièce en thixoforgeage.Semi-solid metals and alloys exhibit a shear thinning behavior characterized by a sharp drop in viscosity with increasing strain rate. This property promotes a smooth die filling during forming. To exploit this advantage, several semi-solid forming process have been developed. Among these processes, we find the thixoforging when the semi-solid state is obtained by a partial remelting from solid state. The solid fraction is above 0.8. Thixoforging of high melting point alloys such as steels is particularly challenging because of about 1400°C temperatures involved. However, previous works showed that this process reveals high potential to reduce material as well as energy consumption. The present PhD thesis is part of a French research project named TACA «Thixoforging of steels for fabrication of automative parts» leaded by IRT-M2P. It aims at industrial development of steel thixoforging for manufacturing automotive components. The mastery and the development of steel thixoforging require a good knowledge of the mechanical behavior of semi-solid steels and appropriate numerical tools to simulate the process. The PhD work aims to (1) characterize the thermomechanical behavior of semi-solid steels and (2) develop constitutive equations that have to be implemented into the commercial code FORGE® to simulate thixoforging. A special attention was paid to the tensile behavior to investigate the temperature range in which the material is very sensitive to hot cracking. Tensile tests provided the temperature from which the material lost its tensile strength and its ductility. Mechanisms leading to the drop of these two properties were identified and were found to be consistent with mechanisms described in literature. A model based on homogenization approach, namely taking explicitly into account the mechanical role of the liquid and solid phases was developed. This model is based on a viscoplastic approach previously developed that was enhanced to (1) include the elastic response of the solid skeleton saturated with liquid and to (2) distinguish the evolution of the spatial liquid/solid distribution according to the tensile or compressive loading path. It successfully describes the three stages of the response in tension: increase, stabilization and decrease of the stress with increasing displacement. The model was implemented in the FORGE® finite element code. The experimental tensile tests were simulated to provide identification of the model parameters. The simulation results showed that strong deformation localization zones were predicted consistently with experiments. Simulations of thixoforging industrial processes such as forging U were studied and compared with experimental results achieved on the Vulcan platform (ENSAM Metz). In addition, a criterion determining the zones without any tensile strength and so sensitive to hot cracking was proposed. Comparison with experimental observations showed that this criterion is an encouraging first approach to predict the brittle zones of thixoforging parts

Real-time prediction by data-driven models applied to induction heating process

Data-driven modeling approach constitutes an appealing alternative to the finite element method for optimizing complex multiphysics parametrized problems. In this context, this paper aims at proposing a parametric solution for the temperature-time evolution during the multiphysics induction heating process by using a data-driven non-intrusive modeling approach. To achieve this goal, firstly, a set of synthetic solutions was collected, at some sparse sensors in the space domain and for properly selected process parameters, by solving the full-order finite element models using FORGE® software. Then, the gappy proper orthogonal decomposition method was used to complete the missing data. Next, the proper orthogonal decomposition method coupled with the nonlinear sparse proper generalized decomposition regression method was applied to find a low-dimensional space onto which the original solutions were projected and a model for the low-dimensional representations was, therefore, created. Hence, a real-time prediction of the temperature-time evolution and for any new process parameters could be efficiently computed at the predefined positions (sensors) in the space domain. Finally, spatial interpolation was carried out to extend the solutions everywhere in the spatial domain by applying a strategy based on the nonlinear dimensionality reduction by locally linear embedding method and the proper orthogonal decomposition method with radial basis functions interpolation. It was shown that the results are promising and the applied approaches provide good approximations in the low-data limit case.This research was carried out as part of a project TRANS-FUGE sponsored by the french institute of research and technology in materials, metallurgy and processes (IRT-M2P), France. The project benefited from funding from a consortium of industrial partners and the French PIA (Plan d’Investissement d’Avenir) granted the French National Agency for Research (ANR)