Alain Potiron

Finite element modeling of sheet-metal blanking operations with experimental verification

Abstract In order to accurately simulate sheet-metal cutting processes by material shearing mechanisms, such as blanking and punching processes, a finite element model valid for the numerical description of such processes has been developed. Damage and crack propagation have been taken into account by means of an elastoplastic constitutive law. To study the effects of variation of processes parameters on the geometry of sheared edges and the force-punch penetration evolution, we have implemented the algorithm of calculation by means of users routine (UMAT) of ABAQUS/Standard finite element code. Final results of the FEM simulation agree with the experimental ones.

Numerical pressure prediction algorithm of superplastic forming processes using 2D and 3D models

The paper describes a finite element model allowing for the prediction in a rapid way the optimum pressure cycle law, the deformed shapes, the distributions of the strain rate and the evolution of the thickness during superplastic forming processes. During the calculation, a pressure-cycle control algorithm is used in the analysis which keeps track of the maximum strain rate sensitivity index m, and adapts the pressure law applied in order to approach as nearly as possible the optimal pressure time history law. The purpose is not to follow the target exactly but obtain a practical pressure time history in a low computation cost time. To compare the performance of 2D and 3D approaches, two analyses have been performed using 2D and 3D finite element modeling. The numerical results are compared with the experimental ones to verify the validity of the pressure algorithm control.

Finite element damage modeling in bending processes

Abstract The paper describes a 3D finite element modeling of air-bending process allowing for the prediction of the damage evolution during the forming operation. The numerical simulation of the damage evolution has been modeled by means of continuum damage approach. A damage model accumulation based on the Rice and Tracey ductile fracture criterion allowing for the description of the exponential dependence on triaxiality has been implemented into a finite element code. The mechanical state of the workpiece determined by the material properties variation in the domain of the bending arc such as the hardening and damage states as a result of the increase in strain toward the inner and outer surfaces in the bending arc.

Comparison between 2D and 3D numerical modeling of superplastic forming processes

In this paper, the numerical results obtained by a finite element analysis in the case of superplastic sheet forming simulation are compared with the experimental ones to verify the validity of the finite element model (FEM) developed to predict the optimum pressure cycle, the deformed shapes, the distributions of the strain rate and the evolution of the thickness during the forming process. To compare the performance of 2D and 3D approaches, two analyses have been performed using a 2D model with 2D fully integrated continuum axisymmetric elements, and a 3D model with 3D fully integrated shell elements. Final results of the finite element modeling agree with the experimental ones.

Application of design of experiment technique for metal blanking processes optimization

The blanking of metal parts is subjected to a variety of process parameters. In this paper, an experimental investigation of the blanking process was carried out using tools with four different wear states and four different clearances. The aim was to study the effects of the interaction between the clearance, the wear state of the tool and the sheet metal thickness on the evolution of the blanking force and the geometry of the sheared profile. Designed experiments are an efficient and cost-effective way to model and analyze the relationships that describe process variations. The results of the proposed experimental investigation show that there is no universal optimal clearance value. Whether clearance should be set at 5% or 10% ultimately depends on the priorities of the practitioners. In the present investigation, mathematical relationship describing the fracture zone depth, the fracture angle and the blanking force are proposed.

Application of response surface method for FEM bending analysis

The bending of metal parts is subjected to a variety of process parameters. In this paper, a numerical investigation into the bending process was carried out. The aim was to study the effects of the interaction between the clearance and the die corner radius on the evolution of the bending force, the maximum damage within the part, the springback and the Mises stress. Designed experiments are an efficient and cost-effective way to model and analyse the relationships that describe process variations. The numerical simulation of the damage evolution has been modelled by means of continuum damage approach. The Lemaitre damage model, taking into account the influence of triaxiality, has been implemented into ABAQUS/Standard code, in order to predict the risk to external fibres during the process and the changes in material characteristics after bending. The results of the proposed investigation show the strong dependence between the inputs and the responses.

Étude bidimensionnelle du positionnement relatif des éléments de mécanismes avec jeu dans les liaisons par une méthode d'optimisation

One of the main objectives of engineers is the improvement of the performances of mechanisms and their reliability. The goal of this study is to propose a new method of static analysis in order to determine the arrangement of the various components of planar mechanisms subjected to mechanical loadings. The study takes into account the presence of linkage clearance and allows for the computation of the small variations of the parts position compared to the large amplitude of the movements useful for the power transmission. The method is based on the minimization of the potential energy of the whole mechanism. The results obtained from several simulations show the effectiveness of the method. The applications can deal with the numerical simulation of contacts between solids in finite element codes.

Fracture prediction of sheet-metal blanking process

Publisher Summary This chapter provides a finite element model allowing for the numerical studies of structures, subjected to damage and ductile fracture. To meet this goal, the best suited models describing the whole blanking process have been used in the chapter. Making of thin mechanical parts that requires costly tools and machines is widely used. A modern way to decrease the developments costs is to implement a numerical simulation. In the case of sheet-metal forming, the process involves complex solicitations of the material and many physical phenomena, such as hardening and damaging, may occur leading to modifications of the materials behavior. In some processes as blanking, shearing and punching, the rupture of the sheet is wanted. Consequently, during the numerical simulation, a mechanical behaviour model will necessarily account for damaging and will include several failure criteria. This allows for a more realistic outlining of the industrial process from its starting point up to the final breaking of the part.

Experimental and Numerical Studies of Edge Rounding Process in HSLA Steels Sheet Metal

Blanking of sheet-metal is an important forming process in the automotive industry for the manufacture of mechanical components. The final component shape, obtained at the end of bending or deep-drawing processes, often has sharp edges due to the blanking operation. Edge Rounding by Punching (E.R.P.) of safety components is necessary to avoid cutting the belt material. In addition to removing the sharp edges, the punching results in work hardening of the material in the rounded zones which results in an increase in the local resistance of the material. In this study, a High Strength Low Alloy steel (HSLA S500MC) is tested with the aim of analysing the residuals fields in the chaining of blanking and edge rounding processes. The mechanical behaviour of the sheet material is investigated by means of tensile tests and Vickers micro-hardness measurements. Numerical simulations are performed using a ductile damage criterion. The experimental residual stress fields are characterised and compared to numerical results, in view of predicting the in-service behaviour of the component. Specimens with rounded edges are compared to specimens that were not submitted to the rounding operation. It is shown that (E.R.P.) improves the component resistance, therefore justifying the use of this process in the manufacture of automotive safety components.

Optimisation of Shape Parameters and Process Manufacturing for an Automotive Safety Part

In recent years, the weight and the cost of automotive vehicles have considerably increased due to the importance devoted to safety systems. It is therefore necessary to reduce the weight and the production cost of components by improving their shape and manufacturing process. This work deals with a numerical approach for optimizing the manufacturing process parameters of a safety belt anchor using a genetic algorithm (NSGA II). This type of component is typically manufactured in three stages: blanking, rounding of the edges by punching and finally, bending with a 90° angle. In this study, only the rounding and the bending will be treated. The numerical model is linked to the genetic algorithm in order to optimize the process parameters. This is implemented by using ABAQUS© script files developed in the Python programming language. The algorithm modifies the script files and restarts the FEM analysis automatically. Lemaitre’s damage model is introduced in the material behaviour laws and implemented in the...