Abstract: As soon as it is question of modelling the follow-up of a geometry during an operation of forming process, the difficulties of meshing and remeshing are often emphases. If the part is situated between rigid tools (case of the deep drawing), in the problems of remeshing are also added difficulties on the management of the contact between the parts. In this case, the deformations are caused by the contact with the tools whose geometry are fixed. The piece must take the shape of the tool geometries during the deformation. In this paper, we present a method coupling an adaptive remeshing strategy and a technique of projection on the tool. The remeshing is based on refinement and coarsening procedures. The projection of the new nodes on the tool allows keeping the contact between the part and the tools. Numerical examples show the efficiency of the method.
Abstract: In this study, we present an experimental/numerical methodology which aims to improve 3D thin sheet hydroforming. The experimental study is dedicated to the identification of stress-strain flow by using the Nelder-Mead simplex algorithm optimization from the global measure of displacement and force. Applications are made to the simulation of thin sheet hydroforming using different die geometry to show the efficiency of the proposed methodology to localize plastic instability, thinning of the blanks and damage initiation under different forming condition.
Abstract: In metal forming processes, different parameters (Material constants, geometric dimensions, loads …) exhibits unavoidable scatter that lead the process unreliable and unstable. In this paper, we interest particularly in tube hydroforming process (THP). This process consists to apply an inner pressure combined to an axial displacement to manufacture the part. During the manufacturing phase, inappropriate choice of the loading paths can lead to failure. Deterministic approaches are unable to optimize the process with taking into account to the uncertainty. In this work, we introduce the Reliability-Based Design Optimization (RBDO) to optimize the process under probabilistic considerations to ensure a high reliability level and stability during the manufacturing phase and avoid the occurrence of such plastic instability. Taking account of the uncertainty offer to the process a high stability associated with a low probability of failure. The definition of the objective function and the probabilistic constraints takes advantages from the Forming Limit Diagram (FLD) and the Forming Limit Stress Diagram (FLSD) used as a failure criterion to detect the occurrence of wrinkling, severe thinning, and necking. A THP is then introduced as an example to illustrate the proposed approach. The results show the robustness and efficiency of RBDO to improve thickness distribution and minimize the risk of potential failure modes.
Abstract: Coupled constitutive equations, formulated in the framework of the thermodynamics of irreversible processes accounting for isotropic hardening as well as the isotropic ductile damage are used to simulate numerically, by the Finite Element Analysis, 3D metal hydroforming processes. The experimental study is dedicated to the identification of stress-strain flow and damage parameters by using the Nelder-Mead simplex algorithm optimization from the global measure of displacement and force. Applications are made to the simulation of thin sheet thermohydroforming using different die geometry to show the efficiency of the proposed methodology and to localize plastic instability, thinning of sheet and damage initiation under different forming conditions.
Abstract: FUSCOMP (FUSelage COMPosite) is a Research & Development program which has received the label from the Aerospace Valley competitiveness cluster. It will lead to a test of a composite fuselage demonstrator manufactured by the Liquid Resin Infusion (LRI) process. LRI is based on the moulding of high performance composite parts by infusing liquid resin on dry fibers instead of prepreg fabrics. The study of this proof of concept is based on the TBM 850 airframe, a pressurized business turboprop aircraft currently produced by DAHER-SOCATA. Technical achievements will concern numerical methods and finite elements analysis to be used for the modelling of this aircraft composite fuselage structure. Actual industrial projects face composite integrated structure issues as a number of structures (stiffeners,...) are more and more integrated onto the skins of aircraft fuselage. Indeed the main benefit of LRI is to reduce assembly steps which lead to cycle time gain and thus cost reduction. In particular, infusing components and sub-components at the same time avoids riveting parts altogether. However it is necessary to validate the dimensioning of the studied composite structure.
Abstract: Liquid Composite Molding (LCM) is a popular manufacturing process used in many industries. In Resin Transfer Molding (RTM), the liquid resin flows through the fibrous preform placed in a mold. Numerical simulation of the filling stage is a useful tool in mold design. In this paper the implemented method is based on coupling a Boundary Element Method (BEM) with a Level Set tracking. The present contribution is a two-dimensional approach, decoupled from kinetics, thermal analysis and reinforcement deformation occurring during the flow. Applications are presented and tested, including a flow close to industrial conditions.
Abstract: The manufacturing of aeronautic parts with high mechanical properties requires the use of high performance materials. That’s why; new materials are used for landing gears such as the titanium alloy Ti-5553. The machining of this material leads to high cutting forces and temperatures, and poor machinability which requires the use of low cutting conditions. In order to increase the productivity rate, one solution could be to raise the workpiece initial temperature. Assisted hot machining consists in heating the workpiece material before the material removal takes place, in order to weaken the material mechanical properties, and thus reducing at least the cutting forces. First, a bibliography review has been done in order to determine all heating instruments used and the thermal alleviation that exists on conventional materials. An induction assisted hot machining was chosen and a system capable to maintain a constant temperature into the workpiece during machining (turning) was designed. Trails permit to identify the variation of cutting forces according to the initial temperature of the workpiece, with fixed cutting conditions according to the TMP (Tool-Material-Pair) methodology at ambient temperature. Tool life and deterioration mode are identified notably. The results analysis shows a low reduction of specific cutting forces for a temperature area compatible with industrial process. The reduction is more important at elevated temperature. However, it has consequences on quality of the workpiece surface and tool wear.
Abstract: The object of this work research tasks relates to the improvement of the cutting tools in drilling within the industrial framework of the aeronautical assembly. The stakes of the study consist in optimizing the lifespan of the tools according to a criterion of respect of geometrical quality and surface quality of the bored holes. This optimization relates to the geometry of the cutting part of the drills. The discussion thread of work thus tends to set up methods which make it possible to bind the geometry of the tools to the final quality of borings carried out. The study was divided into three stages differentiated and complementary to modeling of the physical phenomena induced by the process of drilling. The first stage  lies in describing the real geometrical parameters according to the parameters of grinding of the tool. While being based on the modeling of the geometry, the experimental cutting model enables to identify the mechanical actions of cut along the edge. Lastly, the phenomenological  aspect of the process associates the parameters of cut the final quality of the bored holes. .
Abstract: This paper presents a numerical simulation of the Laser Shock Peening (LSP) process using Finite Element Method (FEM). The majority of the controlling parameters of the process have been taken into account. The LSP loading has been characterized by using a repetitive time Gaussian increment pressure applied uniformly at the impacted zone. The used behavior law of the treated material is supposed Johnson Cook elastic-viscous-plastic coupled with damage. The proposed model leads to obtain the surface modifications (i) the in-depth residual stresses profile, (ii) the induced plastic strains profile, (iii) the geometrical surface modification of the impacted zone and (iv) the superficial damage which can be induced in few cases, where the operating conditions are not well chosen and optimized. An aeronautical application of LSP has been carried out on aircraft turbine engine blade made by Ti-6Al-4V super alloy. This mechanical treatment is applied in order to increase the durability of titanium fan blades and decrease their sensitivity to foreign object damage (FOD). The resulting surface compressive residual stress significantly improves the high-cycle-fatigue properties of the component and greatly increases resistance to blade failure. Finally, we studied the feasibility of the influence of LSP treatment on the phenomenon of crack propagation by introducing a superficial crack defect on the edge of the studied blade structure. This is physically consistent and leads to optimize the operating conditions in order to limit the damage risks.