Publisher Summary A simplified method called “inverse approach” (IA) has been developed for sheet... more Publisher Summary A simplified method called “inverse approach” (IA) has been developed for sheet forming modeling. The IA is based on the knowledge of the final workpiece shape. Starting with the element mesh on the workpiece, an iterative resolution allows finding the original node positions on the initial flat blank satisfying the equilibrium in the final workpiece and then the strains and stresses are calculated. The assumptions of proportional loading and simplified tool actions lead to a “one-step” algorithm. This IA is less accurate but much faster than classical incremental approaches; it is widely used in the preliminary design of forming tools. Numerous tests have proved that the IA gave good strain estimation but poor stress prediction. The recent pseudo IA largely improves the stress evaluation by using deformation history, which allows the damage consideration in the sheet forming modeling by simplified methods.
Integrated Design and Manufacturing in Mechanical Engineering, 2002
The aim of this investigation is to present a numerical procedure combining a simplified finite e... more The aim of this investigation is to present a numerical procedure combining a simplified finite element inverse approach (I.A.) for the rapid simulation of the stamping process with mathematical programming technique (BFGS method) to optimize the stamping process design. Our objective is to optimize the quality of the final workpiece, by minimizing the risk of rupture and wrinkles. The design variables of this problem are the drawbead restraining forces, and the material parameters such as the strain hardening exponent n (Hollomon law) and the Lankford anisotropy coefficient in relation with the Forming Limit Diagram (FLD). The optimization procedure developed has been applied for the square cup of Numisheet’93 and the Renault/Twingo dashpot cup. The satisfactory results demonstrate the usefulness of this automatic optimization procedure in the preliminary design of deep-drawing process.
Integrated Design and Manufacturing in Mechanical Engineering ’98, 1999
In this paper a general methodology to perform shape op- timization of geometrically non-linear s... more In this paper a general methodology to perform shape op- timization of geometrically non-linear shells of revolution including automatic mesh generation, error estimation technique and adaptivity, is proposed. The optimization process is carried out by coupling non-linear FE analysis, B-Spline shape parametrization, sensitivity analysis, mathematical programming and automatic adaptive mesh refinement. An efficient sensitivity analysis is used to determine the gradients of the objective function and constraints. An example of shell optimization is considered to illustrate the application of the proposed approach
... Two important issues when applying RSM to a particular problem concern the design of experime... more ... Two important issues when applying RSM to a particular problem concern the design of experiments and ... variants lies in the interpretation of the step 2. For a symmetric pattern, new data points ... 5. The fast inverse approach (one-step method) has been used to carry out the deep ...
International Journal of Computational Engineering Science, 2002
With the development of finite element method and computer technology, the complete modeling of t... more With the development of finite element method and computer technology, the complete modeling of the forming of a 3D sheet metal part using incremental approaches is becoming realistic. However, an accurate 3D simulation is usually too time-consuming to be used in the early design stage. One solution is to use simplified Inverse or One Step approaches for the sheet forming modeling. Unfortunately, these methods often based on implicit static algorithms, suffer from convergence problems because of strong non-linearities. In this paper we firstly present several initial guess methods to speed up the convergence of the implicit static solver used in the Inverse Approach, then we present some new techniques for the treatment of vertical walls (balancing, opening, matrix condensing,) which has proven to be essential when dealing with complicated parts. All these improvements have been introduced into our in-house F.E. software REFORM and applied to the drawing of industrial automobile parts. The obtained rapid convergence enables the easy determination of various process parameters for the design of sheet forming process. It is concluded that a good initial solution and the treatment of vertical walls play an important role to speed up the Inverse Approach modeling of autobody stamping processes.
ABSTRACT The present paper deals with the blank shape design of high precision thin metallic part... more ABSTRACT The present paper deals with the blank shape design of high precision thin metallic parts obtained by a particular stamping process. The main objective is to optimize the blank shape in order to produce a desired 3D final part within severe fixed tolerances (). Presently, to overcome this issue, a very expensive and time consuming trial and error method is used. Here an attempt is made to develop an automatic numerical procedure based on commercial finite element modeling (FEM) code and Heuristic Optimization Algorithms (HOA). This procedure is composed of two stages: first, an initial guess of the blank shape is performed using the inverse approach (IA), then an update of the blank shape is obtained iteratively combining HOA and incremental FEM code (ABAQUS® or STAMPACK®). The proposed approach is validated on industrial case where the part is stamped in two stages by the mean of manual press, without blank-holder and using tools characterized by complex 3D geometry. This approach has demonstrated its effectiveness and simplicity to provide with a reasonable number of iterations an optimal solution which is in a very good agreement with the experimental results.
... recent developments introduced by the authors on the IA to improve its efficiency in the anal... more ... recent developments introduced by the authors on the IA to improve its efficiency in the analysis and optimum ... In this paper, we present several recent developments: (1) The bending effects are taken into account using a simple triangular shell element without increasing ...
L'objectif de ce travail porte sur le développement et la validation d'une approche num... more L'objectif de ce travail porte sur le développement et la validation d'une approche numérique pour la modélisation du formage de tôles multi-matériaux (acier/polymère/acier), identification de leur comportement lors de la mise en forme et tenue au crash. L'intérêt ici est: ...
Publisher Summary A simplified method called “inverse approach” (IA) has been developed for sheet... more Publisher Summary A simplified method called “inverse approach” (IA) has been developed for sheet forming modeling. The IA is based on the knowledge of the final workpiece shape. Starting with the element mesh on the workpiece, an iterative resolution allows finding the original node positions on the initial flat blank satisfying the equilibrium in the final workpiece and then the strains and stresses are calculated. The assumptions of proportional loading and simplified tool actions lead to a “one-step” algorithm. This IA is less accurate but much faster than classical incremental approaches; it is widely used in the preliminary design of forming tools. Numerous tests have proved that the IA gave good strain estimation but poor stress prediction. The recent pseudo IA largely improves the stress evaluation by using deformation history, which allows the damage consideration in the sheet forming modeling by simplified methods.
Integrated Design and Manufacturing in Mechanical Engineering, 2002
The aim of this investigation is to present a numerical procedure combining a simplified finite e... more The aim of this investigation is to present a numerical procedure combining a simplified finite element inverse approach (I.A.) for the rapid simulation of the stamping process with mathematical programming technique (BFGS method) to optimize the stamping process design. Our objective is to optimize the quality of the final workpiece, by minimizing the risk of rupture and wrinkles. The design variables of this problem are the drawbead restraining forces, and the material parameters such as the strain hardening exponent n (Hollomon law) and the Lankford anisotropy coefficient in relation with the Forming Limit Diagram (FLD). The optimization procedure developed has been applied for the square cup of Numisheet’93 and the Renault/Twingo dashpot cup. The satisfactory results demonstrate the usefulness of this automatic optimization procedure in the preliminary design of deep-drawing process.
Integrated Design and Manufacturing in Mechanical Engineering ’98, 1999
In this paper a general methodology to perform shape op- timization of geometrically non-linear s... more In this paper a general methodology to perform shape op- timization of geometrically non-linear shells of revolution including automatic mesh generation, error estimation technique and adaptivity, is proposed. The optimization process is carried out by coupling non-linear FE analysis, B-Spline shape parametrization, sensitivity analysis, mathematical programming and automatic adaptive mesh refinement. An efficient sensitivity analysis is used to determine the gradients of the objective function and constraints. An example of shell optimization is considered to illustrate the application of the proposed approach
... Two important issues when applying RSM to a particular problem concern the design of experime... more ... Two important issues when applying RSM to a particular problem concern the design of experiments and ... variants lies in the interpretation of the step 2. For a symmetric pattern, new data points ... 5. The fast inverse approach (one-step method) has been used to carry out the deep ...
International Journal of Computational Engineering Science, 2002
With the development of finite element method and computer technology, the complete modeling of t... more With the development of finite element method and computer technology, the complete modeling of the forming of a 3D sheet metal part using incremental approaches is becoming realistic. However, an accurate 3D simulation is usually too time-consuming to be used in the early design stage. One solution is to use simplified Inverse or One Step approaches for the sheet forming modeling. Unfortunately, these methods often based on implicit static algorithms, suffer from convergence problems because of strong non-linearities. In this paper we firstly present several initial guess methods to speed up the convergence of the implicit static solver used in the Inverse Approach, then we present some new techniques for the treatment of vertical walls (balancing, opening, matrix condensing,) which has proven to be essential when dealing with complicated parts. All these improvements have been introduced into our in-house F.E. software REFORM and applied to the drawing of industrial automobile parts. The obtained rapid convergence enables the easy determination of various process parameters for the design of sheet forming process. It is concluded that a good initial solution and the treatment of vertical walls play an important role to speed up the Inverse Approach modeling of autobody stamping processes.
ABSTRACT The present paper deals with the blank shape design of high precision thin metallic part... more ABSTRACT The present paper deals with the blank shape design of high precision thin metallic parts obtained by a particular stamping process. The main objective is to optimize the blank shape in order to produce a desired 3D final part within severe fixed tolerances (). Presently, to overcome this issue, a very expensive and time consuming trial and error method is used. Here an attempt is made to develop an automatic numerical procedure based on commercial finite element modeling (FEM) code and Heuristic Optimization Algorithms (HOA). This procedure is composed of two stages: first, an initial guess of the blank shape is performed using the inverse approach (IA), then an update of the blank shape is obtained iteratively combining HOA and incremental FEM code (ABAQUS® or STAMPACK®). The proposed approach is validated on industrial case where the part is stamped in two stages by the mean of manual press, without blank-holder and using tools characterized by complex 3D geometry. This approach has demonstrated its effectiveness and simplicity to provide with a reasonable number of iterations an optimal solution which is in a very good agreement with the experimental results.
... recent developments introduced by the authors on the IA to improve its efficiency in the anal... more ... recent developments introduced by the authors on the IA to improve its efficiency in the analysis and optimum ... In this paper, we present several recent developments: (1) The bending effects are taken into account using a simple triangular shell element without increasing ...
L'objectif de ce travail porte sur le développement et la validation d'une approche num... more L'objectif de ce travail porte sur le développement et la validation d'une approche numérique pour la modélisation du formage de tôles multi-matériaux (acier/polymère/acier), identification de leur comportement lors de la mise en forme et tenue au crash. L'intérêt ici est: ...
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