Mahfoudh Ayadi

Correlation between welding and hardening parameters of friction stir welded joints of 2017 aluminum alloy

Abstract An experimental study was undertaken to express the hardening Swift law according to friction stir welding (FSW) aluminum alloy 2017. Tensile tests of welded joints were run in accordance with face centered composite design. Two types of identified models based on least square method and response surface method were used to assess the contribution of FSW independent factors on the hardening parameters. These models were introduced into finite-element code “Abaqus” to simulate tensile tests of welded joints. The relative average deviation criterion, between the experimental data and the numerical simulations of tension-elongation of tensile tests, shows good agreement between the experimental results and the predicted hardening models. These results can be used to perform multi-criteria optimization for carrying out specific welds or conducting numerical simulation of plastic deformation of forming process of FSW parts such as hydroforming, bending and forging.

Contribution of Strain Hardening Law Coupled to Damage and Remeshing Procedure in the Localization of Plastic Instabilities Application to Hydroforming Processes

In this study, we present an experimental/numerical methodology, which aims to improve 3D thin sheet hydroforming considering coupled constitutive equations formulated in the framework of the thermodynamics of irreversible processes accounting for isotropic hardening as well as isotropic ductile damage. The experimental study is dedicated to the identification of stress-strain flow from the global measure of pole displacement, thickness evolution, and internal pressure expansion. During the hydroforming processes severe mesh distortion of element occurs and an automatic remeshing generation is essential to carry out the FEA. Some examples are given to demonstrate the efficiency of the proposed methodology.

Behavior Analysis of the Aluminum 2017A Sheet Using Vapor Bulge Test

The hot forming of thin structures (plates) uses the temperature as a factor that could increase the forming limits of the sheet metal. On top of the improving of forming limits, increasing temperature induces a decrease of spring- back and a clear reduction of limits loads necessary for the forming operation. The hot forming process is usually done in two independent phases: the first step is the blank heating and the second one is the load application. The present work shows a forming technique based on both temperature and pressure to make a sheet form. These parameters are linked to the water vaporization process into a cavity covered by the blank. This study will try to show:

Effect of Cooling on Mechanical Properties and Residual Stresses in Aluminium AA2017 Friction Stir Welds

Friction stir welding (FSW) is a relatively new joining technique particularly for aluminium alloys that are difficult to fusion weld. The most common applications are aircraft structures where the cost and weight can be reduced by using new joining techniques instead of riveting.The paper has investigated the effect of cooling on the distribution of residual stresses in friction stir welding of AA2017 aluminium alloy. An attempt has been made to examines the possibility to modify the residual stress state in the joint by applying cooling fluid during FSW processes. The results show that the magnitude of the tensile stress can be reduced significantly in the weld region and we can produce compressive stresses which can be beneficial e.g. for reducing crack propagation speed.

Experimental and numerical study of hydroforming aptitudes of Welded Tubes

This paper presents an experimental/numerical methodology, to improve 3D Welded Tube (WT) behaviour by hydroforming process. This process, used for manufacturing complex structures, allows improving the weight saving and quality of finished parts. The experimental study is dedicated to the identification of stress–strain flow of the Base Metal (BM) and the Heat-Affected Zone (HAZ) from the global measure and nanoindentation test of hydroformed tube state. Workpiece behaviour’s models show the combined effects of the inhomogeneous behaviour of BM and HAZ, and the geometrical singularities found in the WT. From the simulations carried out, it is clear the influence of the plastic flow behaviour of the WT final state.