51 research outputs found

    Consideration of residual stress and geometry during heat treatment to decrease shaft bending

    Get PDF
    In automotive industry, heat treatment of components is implicitly related to distortion. This phenomenon is particularly obvious in the case of gearbox parts because of their typical geometry and precise requirements. Even if distortion can be anticipated to an extent by experience, it remains complex to comprehend. Scientific literature and industrial experience show that the whole manufacturing process chain has an influence on final heat treatment distortions. This paper presents an approach to estimate the influence of some factors on the distortion, based on the idea of a distortion potential taking into account not only geometry but also the manufacturing process history. Then the idea is developed through experiments on an industrial manufacturing process to understand the impact of residual stress due to machining on shaft bending and teeth distortion during heat treatment. Instead of being measured, residual stress is being neutralized. By comparing lots between each other, connections between gear teeth geometry and manufacturing steps before heat treatment are obtained. As a consequence, geometrical nonconformities roots can be determined more easily thanks to this diagnosis tool, and corrective actions can be applied. Secondly, the influence of product geometry on bending is experimentally considered. Moreover, metallurgical observations enable to explain the influence of workpieces geometry on shaft bending. Thanks to the obtained results, process and product recommendations to decrease shafts bending are proposed

    Forging process control: Influence of key parameters variation on product specifications deviations

    Get PDF
    Process control in forging industry is essential to ensure a better quality of the product with a lower cost at the end of the manufacturing process. To control the process, a number of key parameters must be monitored to prevent product or forging plan deviations. This paper will illustrate how a variation in a process parameter can create product specifications deviations and how key parameters influence product final state. The illustration work is done on a part obtained via hot forging. An analysis is made on product parameters such as geometry, by varying the key process parameter values previously determined from a created methodology. This later is represented as a decision support system that connects product specifications (geometry, absence of defects…) or other forging specifications (tool wear, involved energy...) to the process parameters

    Evaluation of process causes and influences of residual stress on gear distortion

    Get PDF
    In the automotive industry, heat treatment of components is implicitly related to distortion. This phenomenon is particularly obvious in the case of gears because of their typical and precise geometry. Even if distortion can be anticipated to an extent by experience, it remains complex to comprehend. This paper presents an approach to estimate the distortion based on the idea of a distortion potential taking into account not only geometry but also the manufacturing process history. Then the idea is developed through simulation and experiments including annealing to understand the impact of residual stress on gear distortion in an industrial case study

    A generic methodology to improve the control of forging process parameters

    Get PDF
    One of the common problems in forging processes is the lack of key process parameters control, as well as their identification. Certain controlled parameters exist, such as temperature or stroke length, which are usually identified and controlled through a systematic approach. Their selection depends particularly on the part to produce or on customer’s constraints, rather than a rational approach. In this paper, a methodology is proposed to select the key process parameters. There are some methodologies which already exist, such as the DMAIC, which are used to determine the control parameters and their influences on the desired specifications. However, this approach has certain drawbacks. For example, the key parameters are selected by experts, which makes each case study time consuming. The aim is to develop a generic methodology to improve the manufacturing process in the forging industry. The methodology is represented as a decision support system that connects product specifications (geometry, absence of defects…) or other forging specifications (tool wear, involved energy...) to the process parameters. The latter will be able to define the key parameters, their values and their appropriate way of control. These links will be setup using the empirical rules and physical laws

    Effect of the plasticity model on the yield surface evolution after abrupt strain-path changes

    Get PDF
    Abrupt strain path changes without elastic unloading have been used in the literature to investigate the yield surface of sheet metals, both experimentally and theoretically. Such pioneering studies emphasized an apparent non-normality of the plastic strain rate tensor with respect to the trace of the yield surface in stress space, following such a strain-path change. They inspired numerous subsequent developments of plasticity models including non-associated flow rules. In this paper, this type of abrupt strain-path changes is investigated using state-of-the-art plasticity models. The aim is to emphasize the respective contributions of elasticity, isotropic-kinematic hardening, and rate sensitivity, to the apparent violation of the normality condition. The results show that these classical ingredients of plasticity models significantly contribute to the apparent vertex and loss of normality. These effects are quantified for typical sheet metals subject to biaxial-to-shear orthogonal strain path change.Bourse CS

    Contribution à la caractérisation des moyens de mise en forme : application aux presses à vis

    Get PDF
    The metal forming industry uses more and more numerical simulation, and especially the Finite Element software Forge®, with the aim to fulfill 3 main objectives: predict tooling lifetime, predict the amount of energy required to obtain the part desired and predict the thermomechanical path leading to the optimal final microstructure. Currently, numerical simulations allow good predictions regarding forging operations with currently used material, like steel. But to remain competitive forging industries cannot work only with steel, and have to innovate by developing new forging process for high performance material. But concerning the forging operations of these new high performing material, significant difference are observed between numerical and experimental results. In particular regarding the prediction of energy required to correctly forge a part. This study aims at understanding this disparity between numerical and experimental results, in the special case of screw presses. For that, the first step describes the functioning of screw presses but also the screw presses model implemented into the Forge software. Experimental results of upsetting tests in 2 different conditions have then been compared to results obtained numerically by simulating the corresponding forging tests. Significant differences are observed, and the necessity to define a stiffness coefficient for the press is highlighted. Two methods have been carried out to determine the stiffness of the press, a theoretical one and an experimental one. Concerning the experimental one, external tools of acquisition like a rapid camera and a 3D tracking points system have been used to analyze the press behavior during blows. Finally, stiffness values obtained with the two different methods are compared

    Contribution to characterization of metal forming machines: application to screw presses

    Get PDF
    Finite Element analyses are established in the metal forming industry, with the aim to fulfill three objectives: predict tooling lifetime, predict the energy required to obtain the desired part and predict the thermomechanical path leading to the optimal microstructure. Currently, simulations allow good predictions regarding forging operations with currently used material, like steel, but concerning high performing materials, significant difference are observed between numerical and experimental results. This study aims at understanding this disparity between numerical and experimental results, for screw presses. Different methods have been employed to determine the press stiffness, using fast cameras and 3D tracking points systems

    Experimental identification of the process influences on gear distortion during heat treatment

    Get PDF
    Le traitement thermique est utilisé dans l'industrie automobile afin d'améliorer les propriétés mécaniques des pièces fabriquées. Ainsi appliqué après usinage, il augmente la dureté en surface des pièces mais a pour effet secondaire de conduire à des déformations géométriques. Dans le cas des dentures de boîtes de vitesses où les précisions géométriques exigées sont fortes, de telles déformations peuvent conduire à des non-conformités des pièces après traitement thermique. La littérature scientifique et les retours d'expérience industriels montrent que les paramètres du traitement thermique influent sur ces déformations, mais pas seulement. En effet, l'ensemble de la gamme de fabrication en amont du traitement thermique joue un rôle dans l’apparition des défauts. L'objectif des travaux engagés sur une ligne de fabrication industrielle Renault vise à déterminer expérimentalement l'influence de chaque étape de fabrication en amont du traitement thermique sur les déformations des dentures. Pour cela, une méthode est proposée sur les principes de neutralisation des contraintes résiduelles et de comparaison entre différents lots expérimentaux ayant une histoire mécanique différente. Les résultats permettent ainsi de relier chaque type de déformation sur les paramètres géométriques de la denture à une ou plusieurs étapes de fabrication en particulier. En conséquence, lorsqu'une dérive sur le procédé de fabrication est détectée sur un critère denture spécifique, la méthode ainsi développée permet de diagnostiquer l'origine d'un tel défaut au sein de la gamme de fabrication en amont. De cette façon, les actions curatives peuvent être mises en place plus rapidement et plus efficacement

    Vers l’asservissement du pilotage en énergie d'une opération de forgeage : développement d'un métamodèle prédictif pour un jumeau numérique

    Get PDF
    In the aeronautical sector, because parts are mainly of large dimensions and in high performance materials, products are forged in small batches. Forming these complex parts requires energy-controlled production means, such as screw presses or, more generally, forging hammer. With these machines, several successive strokes are necessary to obtain the parts desired geometry and mechanical characteristics. However, for these small quantities, the automation of the manufacturing process is not necessarily possible or profitable and consequently, the control of the machine remains dependent on the know-how of the operators, in particular with regard to the quantity of energy to be delivered blow after blow, the temperature, the lubrication conditions, etc. The main challenge is to provide flexibility and robustness particularly adapted to small batches, thus limiting the impact of process parameters variability on the part final quality. To reach that goal, the implementation of a digital twin is proposed. The objective of the project is to develop a digital twin in the context of forming materials on an energy-controlled screw press. The scientific challenge is to obtain an accurate, predictive and reactive twin that will allow real-time control of the process as well as access to information that cannot be measured during the manufacturing process. A methodology for the creation of a predictive meta-model based on a calibrated numerical simulation and updated by machine learning is proposed. This meta-model will compose the digital twin. Our approach is validated on a case study: the uni-axial compression of a copper cylinder. Finally, the following development phases of the digital twin are presented
    • …
    corecore