Résumé: The aim of the present work is to improve the materials’ performances, particularly their elastic property based on an optimal exploitation of surface work-hardening phenomenon, using surface plastic deformation treatment (DPS). The surface of a mechanical piece is considered as the most vulnerable zone that determines its mechanical performances. To improve the surface physico-mechanical properties, the surface plastic deformation treatment (DPS) is often used. The (DPS) acts by a combined action of: surface hardening, structural modification, and the generation of the compression residual stresses, the factors that will create a heterogeneous plastic deformation. Knowing that during operation the mechanical pieces have to be subjected to a stress smaller than the elastic limit (taking into account the safety margins), where the material behavior is reversible, and to reach the maximum allowable stresses, we have to increase the material’s elastic limits. This objective can be realized through an optimal use of work hardening phenomenon for the treated surface by the DPS. The work hardening is characterized by the increase of the yield strength (Re), the surface hardness (Hv), and consequently the increase of the brittleness. Depending on the considered metals, when the piece has a defect variation: cavity, inclusion (precipitate), or zones of different hardness, it can create a stress concentration which generates a local hardening. This phenomenon is one of the main causes of crack generation. In our study, we consider the influence of work hardening on the elastic behavior of XC38 steel and aluminum alloy.

Résumé: The aim of this work is to study the plastic instabilities occurring on the stamped sheets during deep drawing process. The analysis of the plastic deformation of the material showed that the deformation occurs in bi-axial extension at the bottom of the punch due to thinning of the sheet, in local necking together at the vertical wall level of the sheet and below the blank holder due to thickening of the sheet. As a first step, an experimental characterization of the material is undertaken, whose experimental tests made it possible to determine the fundamental characteristics of the material. In the second step, a study of the material behaviour during forming process by numerical simulation using Abaqus finite element code is proposed. The various simulations undertaken showed the variation of the two parameters; the blank holder force and the friction effect. The blank holder force and friction, applied respectively to the blank flange region and between the tool-blank surfaces, make it possible to optimize the deformation limits and to repel any instability which may appear on the material in deep drawing. The simulations carried out on Abaqus code allow to visualize the material behaviour during deformation, by locating the thinning and necking zones on the sheet and from there, in order to locate areas at risk of failure. An optimization of the process is proposed by varying the considered parameters in a validated numerical model. Satisfactory results have been obtained which clearly show the failure and the safe zones.

Résumé: The present work is a contribution in analyzing dimensional deviations in ellipsoidal thin-layer steel heads used for high-pressure air brake reservoirs. The dimensional deviations are attributed to the thickness distribution during the drawing process with regard to input geometrical parameters such as punch and die diameter, and also die and punch fillet. The aim of the present work is therefore optimizing the input data in order to respect the initial geometrical requirement. Investigation has been carried out using FEM code Abaqus, on a case example produced by the Algerian truck company according to G.R.C E81-102 standard. FEM simulations followed the process of deep drawing and concerned the effect of the most influencing factors such as the die corner radius, the punch corner radius, and the blank radius. Dimensional deviations are analyzed in terms of variations of thinning along the true dish path and hence engineering models of the corresponding true strain in the straight zone, the knuckle zone, and the crown zone of the dish are proposed.

Résumé: The present work investigates the reinforcement of concrete wheat-grain silos under initial damage. The reinforcement is achieved by mounting bands of carbon fiber reinforced polymer (CFRP) on the external walls of the silo. 4 modes of reinforcement are adapted according to the width of the band, the gap between two bands, the height of reinforcement and the number of layers achieved through banding. Analytical analyses were conducted using the Reimbert method and the Eurocode 1 Part 4 method, as well as numerically through the finite element software Abaqus. Results show that the normal pressure reaches a peak value when approaching the silo hopper. Initial damage in a concrete silo was first determined using a 3D geometrical model, while the damage analyses were conducted to optimize the CFRP reinforcement by mounting 2 CFRP bands close together above and below the cylinder–hopper joint. Increasing the number of banding layers could produce better performance as the damage was slightly decreased from 0.161 to 0.152 for 1 and 4 layers respectively.

Résumé: The object of this study is to highlight one the most encountered problems in the sheet metal forming. Cases of rupture on the mild steel sheet were recorded in a deep drawing workshop, during the forming operation of the wheelbarrows. The phenomenon appearance, led us to carry out a study of the material behavior during the metal forming. A characterization of the material is proposed and 3D simulations of the forming operation were performed on the finite element code Abaqus/CAE Explicit. The objective is to highlight the influence of the different deep drawing parameters on the sheet behavior during the deformation, especially the holding force, the die radius, the coefficient of friction between the contact surfaces and the punch velocity.The results are summarized in a representation of the strain curves in the three directions of the drawn part at the end of deep drawing operation, localization of the sheet areas which present a risk of tearing and the proposals to avoid this phenomenon depending on the variation of the operating parameters.

Résumé: The present study is based on cases of sheet rupture, which occurred on deep drawn components produced in a workshop of one company during deep drawing operations. A characterization of material behaviour in deep drawing is proposed to define the limits imposed to the forming of sheets by the development of a zone of localised necking. First, tension tests are carried out to determine the characteristics of the material, i.e., the anisotropy coefficient and the hardening law. Then, deep drawing tests of the Marciniak type are carried out to determine the Forming Limit Curve (FLC) of the material by means of the method of image correlation using specific software. Knowing the properties of the material and the limits of deformation which define the occurrence of necking, the problem of sheet rupture during material forming will be reduced.

Résumé: This study is based on cases of the sheet metal rupture in the deep drawn, recorded in workshop of the wheelbarrows manufacturing company. The process simulations for obtaining the wheelbarrow are conducted on the Abaqus/cae finite element code, in order to visualize the deformation process and the material mechanical behavior at deep drawing. Areas with high local thinning before a tear have been highlighted from the representation of the thickness configuration and the deformation at the end operation. This allows to predicting the areas of necking which caused of rupture at some drawns of the company, such as the wheelbarrow reported to the laboratory for analysis of material and of the tear of sheet at the end of operation. The results are summarized in the curves of stresses and strains distribution during the deep drawing, the localization of areas at risk of tears and the determination of parameters causing the tearing of sheet. Index Terms- Deep drawing, simulation, strain,stress, tear.

Résumé: This present study is proposed following cases of sheet rupture which occurred on deep drawn components produced in a workshop of one company, during deep drawing operations. First, experimental tests were conducted in order to determine the characteristics of the material. Secondly, numerical simulations, using finite element code Abaqus, were carried out to study multi problems, which appear during the forming, as the necking and the rupture of the sheet. Varying some multi-physical parameters in the deep drawing operations, would allow us to prevent this type of problem. Thus, the simulation, allowing easily the variation of some physical parameters in the model found, enables us to infer different scenarios that could rate the impact of these parameters in the occurrence of the problem. The model will then optimized, and it leads to improve the working conditions. In this study, we vary the coefficient of friction and pressure of the blank holder in order to deduce the influence of these two parameters. Results allowed the visualization of the deformation evolution of the material during the deep drawing process, the distribution of stresses and strains on different areas of the sheet, and the influence of each physical parameter on the material behaviour. Also, high local thinning areas that may lead to the rupture were located.