Philippe Dal Santo

A Simple Discrete Method for the Simulation of the Preforming of Woven Fabric Reinforcement

In this paper, a discrete approach for the simulation of the preforming of dry woven reinforcement is proposed. A “unit cell” is built using elastic isotropic shells and axial connectors instead of bars and beams used in previous studies. Shell elements are used to take into account the in-plane shear stiffness and to manage contact phenomenon with the punch and die. Connectors reinforce the structure in the yarn directions and naturally capture the specific behavior of the fabric. To identify the material parameters, uniaxial tensile tests and bias tests have been employed. A numerical algorithm, coupling Matlab and Abaqus/Explicit, is used to determine the shear parameters by an inverse method. The model has been implemented in Abaqus to simulate hemispherical stamping. Experimental results are compared to numerical simulations, good agreement between both results is shown.

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.

Experimental and Numerical Study of Single Point Incremental Forming for a Spiral Toolpath Strategy

Incremental sheet forming is a flexible forming process based on the sheet progressive localized deformation where a forming tool follows a trajectory predetermined in advance by CAD/CAM programs. Although it is a slow process compared to conventional processes, this relatively new technique is very adequate for prototyping and small series production since it does not require complex tooling (die, punch, etc.). This paper presents a numerical and an experimental study of the Increment Sheet Forming process for a spiral toolpath. A 30 mm depth conical forming part is considered for this purpose. The experimental forming operation has been conducted on a 3-axis milling machine and the experimental data analysis was performed using a Kistler measurement system and a 3D scanner. Moreover, a Finite Element simulation has been realized in order to predict the evolution of the forming forces and the part final profile. The numerical results were in good agreement with the experimental ones. Moreover, the analysis of the scanning data has successfully restituted the part final profile and the surface details.

Cold forming by stretching of aeronautic sheet metal parts

In this article, the development of an industrial prototype for manufacturing aeronautical fuselage panels is investigated. Deep drawing of large components such as aircraft fuselage panels is not an easy task in terms of dimensional accuracy, reliable material behaviour laws and failure criteria. Hot stretching processes ensure large ductility range of some materials. Nevertheless, when using high-performance aluminium alloys with acceptable low-plastic strain at ambient temperature, cold forming might be employed. A special stretching machine of 40-ton (400 kN) capability was instrumented and piloted in that way. Typical operations involved in the forming of parts are carried out with a die on which the sheet metal is successively stretched and drawn in several steps. Currently, the shape of the forming tool is directly determined from CAD models of the final sheet geometry without taking into account springback or residual effects. To increase the dimensional accuracy of the final components, a methodology to define the die shape and to control the process is proposed, taking into account the parameters influencing the forming operations. A feedback loop based on digitalised physical geometry and numerical simulation is carried out in order to ensure that the final shape of the sheet will be accurately obtained.

Creep forming of an Al-Mg-Li alloy for aeronautic application

Creep forming of Al-Mg-Li alloy sheets is studied. An instrumented bulging machine is used to form a double curvature panel at a reduced scale. The deformation of the work-sheet is ensured by a 7475 aluminum alloy lost sheet deformed by a gas pressure applied on its upper surface. A numerical model using the ABAQUS software is developed in order to obtain the pressure law and to ensure the forming conditions during the cycle. This model is validated by comparing experiments and numerical results in terms of deformed shape and thickness evolution.

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...