Fatigue analysis-based numerical design of stamping tools made of cast iron

This work concerns stress and fatigue analysis of stamping tools made of cast iron with an essentially pearlitic matrix and containing foundry defects. Our approach consists at first, in coupling the stamping numerical processing simulations and structure analysis in order to improve the tool stiffness geometry for minimizing the stress state and optimizing their fatigue lifetime. The method consists in simulating the stamping process by considering the tool as a perfect rigid body. The estimated contact pressure is then used as boundary condition for FEM structure loading analysis of the tool. The result of this analysis is compared with the critical stress limit depending on the automotive model. The acceptance of this test allows calculating the fatigue lifetime of the critical zone by using the S–N curve of corresponding load ratio. If the prescribed tool life requirements are not satisfied, then the critical region of the tool is redesigned and the whole simulation procedures are reactivated. This method is applied for a cast iron EN-GJS-600-3. The stress-failure (S–N) curves for this material is determined at room temperature under push pull loading with different load ratios R0σmin/σmax0−2, R0−1 and R00.1. The effects of the foundry defects are determined by SEM observations of crack initiation sites. Their presence in tested specimens is associated with a reduction of fatigue lifetime by a factor of 2. However, the effect of the load ratio is more important

Automatic optimization of the cooling of injection mold based on the boundary element method

8th International Conference on Numerical Methods in Industrial Forming Processes, Columbus, OH, JUN 13-17, 2004International audiencePart cooling during injection molding is the critical step as it is the most time consuming. An inefficient mold cooling may have dramatic consequences on cycle time and part quality and may require expensive mold rectification. In order to reduce mold and production costs, an automatic optimization of cooling device geometry and processing parameters (temperature, flow rate...) has been developed. The first step of the optimization is to choose parameters describing the geometry of the cooling device (which may be complex in case of molds obtained by prototyping process). Then numerical simulation of the heat transfer during cooling stage is coupled to a non linear constraint optimization method (sequential quadratic programming). The objective is to find the best set of parameters according to a cost function representing cooling uniformity and/or cooling speed. At each step of the optimization, the boundary element method is used to solve the heat transfer equation (the dual reciprocity method is used for transient problems) and to determine the effect of the parameters on the cost function. The main advantage of the BEM is that remeshing procedure is easier. As a validation, the method is applied to 2D mold geometries representative of difficulties arising during cooling of real industrial parts (with thickness changes or angles). The first computations show fair results

Effet des défauts de fonderie sur la tenue en fatigue des pièces en fonte à graphite sphéroïdal : application au dimensionnement des outils d’emboutissage de tôles de véhicules automobiles

International audienceno abstrac

Automatic optimization of the cooling of injection mold based on the boundary element method

8th International Conference on Numerical Methods in Industrial Forming Processes, Columbus, OH, JUN 13-17, 2004International audiencePart cooling during injection molding is the critical step as it is the most time consuming. An inefficient mold cooling may have dramatic consequences on cycle time and part quality and may require expensive mold rectification. In order to reduce mold and production costs, an automatic optimization of cooling device geometry and processing parameters (temperature, flow rate...) has been developed. The first step of the optimization is to choose parameters describing the geometry of the cooling device (which may be complex in case of molds obtained by prototyping process). Then numerical simulation of the heat transfer during cooling stage is coupled to a non linear constraint optimization method (sequential quadratic programming). The objective is to find the best set of parameters according to a cost function representing cooling uniformity and/or cooling speed. At each step of the optimization, the boundary element method is used to solve the heat transfer equation (the dual reciprocity method is used for transient problems) and to determine the effect of the parameters on the cost function. The main advantage of the BEM is that remeshing procedure is easier. As a validation, the method is applied to 2D mold geometries representative of difficulties arising during cooling of real industrial parts (with thickness changes or angles). The first computations show fair results

Effet des défauts de fonderie sur la tenue en fatigue des pièces en fonte à graphite sphéroïdal : application au dimensionnement des outils d’emboutissage de tôles de véhicules automobiles

International audienceno abstrac

Effet de déformation de lames de cisaillage : comparaison des résultats d'essais et de simulation numérique

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Effet de déformation de lames de cisaillage : comparaison des résultats d'essais et de simulation numérique

International audienceno abstrac

De l'pération d'emboutissage à celle de poinçonnage en suivant le comportement de la tôle

International audienceno abstrac