Ridha Hambli

Fracture criteria identification using an inverse technique method and blanking experiment

Abstract In order to optimize the blanking processes, it is important to identify the conditions within the deforming workpiece which may lead to fracture initiation and propagation. Within this framework, numerical simulations are widely used in industries to optimize sheet metal forming processes. However, in order to have a confidence in the results of such simulations, an accurate material model is required. The accuracy of a material model is affected by the constitutive equations and the values of the material parameters. In order to reduce the danger of fracture of metal parts during manufacturing processes, advanced optimal design requires knowledge of critical values of some fracture criteria of the material used. Experimental identification of fracture criteria are currently obtained by performing several complicated tests and long duration of experiments. This study presents a computation methodology allowing for the identification of critical values of fracture criteria in order to simulate crack initiation and propagation generated by shearing mechanisms, which are needed for metal blanking processes simulation. The approach is based on inverse technique using circular blanking experiments and finite element calibration model. The critical values of fracture criteria are obtained in such a way that the finite element force–penetration predicted curve fit the experimental plot deduced from blanking tests. The numerical results obtained by the simulation were compared with experimental ones to verify the validity of the proposed technique for fracture criteria identification.

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.

Finite element model fracture prediction during sheet-metal blanking processes

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

Prediction of burr height formation in blanking processes using neural network

Abstract Productivity and quality in sheet metal blanking processes part can be assessed by the burr height of the sheared edge after blanking. This paper combines predictive finite element approach with neural network modelling of the leading blanking parameters in order to predict the burr height of the parts for a variety of blanking conditions. Experiments on circular blanking operation has been performed to verify the validity of the proposed approach. The numerical results obtained by finite element computation including damage and fracture modelling and tool wear effects were utilized to train the developed simulation environment based on back propagation neural network modelling. A trained neural network system was used in predicting burr height of the blanked parts versus tool wear state and punch-die clearance. The comparative study between the results obtained by neural network computation and the experimental ones gives good results.

Damage and fracture simulation during the extrusion processes

Abstract In order to accurately predict the damage and failure evolution in the case of metal forming processes, such as stamping and extrusion, a finite element model valid for numerically describing of such processes has been developed. Damage and crack propagation have been taken into account by means of continuum damage mechanics concepts. To study the effects of variation of processes parameters on the geometry of the workpiece, we have implemented a calculation algorithm by means of the user routine (UMAT) of ABAQUS/Standard finite element code. This model enables deformation and fracture initiation to be examined under several different loading conditions. An example is also given to illustrate the potential applicability of the model. The numerical results obtained by the simulation were compared with experimental ones in order to verify the validity of the proposed finite element model.

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.

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.

Identification of Constitutive Parameters Using Inverse Strategy Coupled to an ANN Model

This paper deals with the identification of material parameters using an inverse strategy. In the classical methods, the inverse technique is generally coupled with a finite element code which leads to a long computing time. In this work an inverse strategy coupled with an ANN procedure is proposed. This method has the advantage of being faster than the classical one. To validate this approach an experimental plane tensile and bulge tests are used in order to identify material behavior. The ANN model is trained from finite element simulations of the two tests. In order to reduce the gap between the experimental responses and the numerical ones, the proposed method is coupled with an optimization procedure to identify material parameters for the AISI304. The identified material parameters are the hardening curve and the anisotropic coefficients.