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Parametric Finite Element Analysis for a square cup deep drawing process

Ayari F., Bayraktar E.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 48, nr 1

64--86

EN

Purpose: This manuscript deals with the FEA of the sheet metal forming process that involves various nonlinearities. Our objective is to develop a parametric study that can leads mainly to predict accurately the final geometry of the sheet blank and the distribution of strains and stresses and also to control various forming defects, such as thinning as well as parameters affecting strongly the final form of the sheet after forming process. Design/methodology/approach: The main approach of the current paper is to conduct a validation study of the FEM model. In fact, a 3D parametric FEA model is build using Abaqus /Explicit standard code. Numerous available test data was compared to theoretical predictions via our model. Here, several elastic plastic materials low was used in the FEA model and then, they were validated via experimental results. Findings: Several 2D and 3D plots, which can be used to predict incipient thinning strengths for sheets with flat initial configuration, have been presented for the various loading conditions. Unfortunately, most professionals in the forming process, lack this expertise, which is an obstacle to fully exploit the potential of optimization process of metal forming structures. In this study optimization approach is used to improve the final quality of a deep drawn product d by determining the optimal values of geometric tools parameters. Research limitations/implications: This paper is a first part study of a numerical parametric investigation that is dealing with the most influent parameters in a forming process to simulate the deep drawing of square cup (such as geometric, material parameters and coefficient of frictions). In the future it will be possible to get a large amount of information about typical sheet forming process with various material and geometric parameters and to control them in order to get the most accurate final form under particular loading, material and geometric cases. Originality/value: This model is used with conjunction with optimisation tool to classify geometric parameters that are participating to failure criterion. A mono objective function has been developed within this study to optimise this forming process as a very practical user friend manual.

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Damage analysis of the ceramic reinforced steel matrix composites sheets: experimental and numerical study

Bayraktar E., Ayari F., Katundi D., Chevalier J.-P., Bonnet F.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 49, nr 1

53--61

EN

Purpose: of this paper reports damage analysis of TiB2 (ceramic particles) reinforced steel matrix composite sheets. This new steel composite receives much attention as potential structural materials due to their high specific strength and stiffness. The goal of the research described in this paper is to study the usage of this new steel family in the manufacture of light structures. Design/methodology/approach: therefore in this study is focused to the titanium diboride TiB2 reinforced steel matrix composite sheets that they were characterized by optical and scanning electron microscopes after the mechanical tests carried out on the base metal and welded specimens under dynamic and static test conditions. Findings: The non homogeneity of the structure in this type of composites makes deeply complexity of their numerical and analytical modelling to predict their damage during the loading. For example, the interfaces essentially play a key role in determining mechanical and physical properties. For this reason, a Finite Element (FEM) analysis is used for modelling to simulate the macroscopic behaviour of this material, taking into account the relevant microscopic scales. Practical implications: defined in this research is based on the impact dynamic behaviour of this steel sheets by using a special impact tensile test developed formerly that all details were published in this journal. This type of test gives more comprehensible information about special steel sheets (welded or base metal) in case of dynamic crash conditions. Originality/value: The present research gives detail information on the new steel matrix composite sheets reinforced TiB2 ceramic particles. This new composite was developed by ARCELOR research group and impact dynamic behaviour and weldability of the welded parts and base metals from this composite steel are discussed here in order to give practical and useful solution for industrial applications.

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Fretting wear damage-I: numerical study of composite steel sheets reinforced with TiB2

Ayari F., Bayraktar E.

Archives of Materials Science and Engineering

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2011

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Vol. 51, nr 1

48-54

EN

Purpose: of this paper is based on the damage analysis by fretting wearing occurred on the composite steel sheets reinforced with TiB2 ceramic particles. There is a real lack to find a reliable data and detail research in literature that makes the purpose of this manuscript. Design/methodology/approach: Fretting is a surface degradation process in which removal of material is induced by small amplitude oscillatory movement between contacting components, such as flexible coupling joint structures etc. The main parameters affecting fretting wear are reported to be normal load, slip amplitude, frequency of the oscillatory movement, contact geometry, surface roughness and material properties. In this study, a finite element-based method is presented for simulating the contact of a rigid cylinder on flat fretting wear for the composite steel sheets reinforced with TiB2 ceramic particles. Findings: The general purpose commercial code ABAQUS was employed; this model can be used to facilitate generalization of the present approach to more complex applications. In this study a particular mesh technique was used to optimize the computation time, especially when dynamic analysis is used. In fact, two-dimensional, four-node, plane strain (linear) elements are employed throughout. The mesh (element size) in the contact area is very fine to capture the complicated variation of the surface and subsurface stresses and relative slip. The contact surface is constituted with a rigid hard steel cylinder material and a flat plate of composite steel sheets reinforced with TiB2 ceramic particles. Practical implications: This manuscript concerns a typical contact with the cylindrical plan geometry as it models the major problems and also stress distribution due to the contact was well defined. Our assembly is then, composed with a cylindrical contact with a plan substrate. An elastic - plastic analysis of fretting stress using a finite element ABAQUS is enhanced. The cylindrical pad is made of a rigid material and a flat plate the composite steel sheets reinforced with TiB2 ceramic particles. A bilinear elastic - plastic isotropic hardening model with a von Mises yield surface is employed to characterize the material behaviour of these composite steel sheets reinforced with TiB2 ceramic particles.This manuscript give a real and practical usage as a friendship notice concerning this subject. Originality/value: is very well shown that this model is firstly verified through comparison with an analytical elastic solution. Various parameters, such as friction coefficient, the normal force applied on the top of the pad, tangential force applied to the left side of the pad, and bulk tension applied on the right edge of the substrate are adopted to study the influences of these parameters on fretting stresses to understand the implication and importance of elastic-plastic analysis in fretting fatigue experiments. Keywords: Fretting wear; Slip; Contact; FEM; Mesh refinement; Composite steel sheets; Reinforcement of TIB2

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Torsional fatigue behaviour and damage mechanisms in the very high cycle regime

Bayraktar E., Xue H., Ayari F., Bathias C.

Archives of Materials Science and Engineering

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2010

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Vol. 43, nr 2

77-86

EN

Purpose: of this paper: Many engineering components operate under combined torsion and axial cyclic loading conditions, which can result in fatigue fracture after a very long life regime of fatigue. This fatigue regime were carried out beyond 109 loading cycles called very high cycle fatigue (VHCF) to understand the fatigue properties and damage mechanisms of materials. Design/methodology/approach: Torsional fatigue tests were conducted using a 20 kHz frequency ultrasonic fatigue testing device. The results obtained were compared to those of the conventional torsional fatigue test machine operated at 35 Hz to observe any discrepancy in results due to frequency effects between two experiments. Findings: All the fatigue tests were done up to 1010 cycles at room temperature. Damage mechanisms in torsional fatigues such as crack initiation and propagation in different modes were studied by imaging the samples in a Scanning Electron Microscope (SEM). The results of the two kinds of material show that the stress vs. number of cycle curves (S-N curves) display a considerable decrease in fatigue strength beyond 107 cycles. Research limitations/implications: Each test, the strain of specimen in the gage length must be calibrated with a strain gage bonded to the gage section. This is a critical point of this study. The results are very sensitive to the calibration system. Control of the displacement and the output of the power supply are made continuously by computer and recorded the magnitude of the strain in the specimen.

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Parametric Finite Element Analysis of square cup deep drawing

Ayari F., Lazghab T., Bayraktar E.

Archives of Computational Materials Science and Surface Engineering

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2009

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Vol. 1, nr 2

106-111

EN

Purpose: This paper deals with the FEA of the sheet metal forming process that involves various nonlinearities. Our objective is to develop a parametric study that can leads mainly to predict accurately the final geometry of the sheet blank and the distribution of strains and stresses and also to control various forming defects, such as thinning as well as parameters affecting strongly the final form of the sheet after forming process. Design/methodology/approach: In cold forming (deep drawing) operation, sheet metal is subject to large strains in order to obtain the final desired shape. However, under severe forming conditions the sheet metal may experience some thinning and even some tearing during the process. Parameters of the deep forming process that may contribute to such conditions include, aspect ratio, blank initial thickness, forming temperature, shoulder radii of the die and punch, contact conditions between the blank and the die, holder and punch, punch displacement rate, etc. The work presented in the current paper is a first part study of numerical parametric investigation that is dealing with the most influent parameters in a forming process to simulate the deep drawing of square cup (such as geometric parameters and coefficient of friction). The purpose of the current paper is to conduct a validation study of the FEM model that is used to conduct the study described above. In fact, a 3D parametric FEA model is built using ABAQUS/Explicit standard code. Findings: A methodology to develop this kind of theoretic resolution is pointed out and has been illustrated for a set of variables. Several 2D and 3D plots, which can be used to predict incipient thinning strengths for sheets with flat initial configuration, have been presented for the various loading conditions. Research limitations/implications: As it was mentioned above, this paper is the first part of a study of the numerical parametric investigation that is dealing with the most influent parameters in a forming process to simulate the deep drawing of square cup (such as geometric, material parameters and coefficient of frictions).