Impact Forming of AA5052-H32 Sheets with Friction Stir Spot Welds Using a Shock Tube and Failure Assessment

Abstract

In this present study, both the experimental and numerical investigations are carried out to understand the formability of 1.5 mm thick AA 5052-H32 sheets with friction stir spot weld (FSSW). A shock tube experimental facility is utilized in which a rigid hemispherical striker is propelled at a high velocity and deforms the FSSW sheets at high strain rates. In this analysis, the effect of different tool rotational speed and plunge depth on the FS spot welding outputs and forming outputs are understood. Furthermore, DEFORM-3D FE code is used to perform FE simulation of both the FS spot welding and forming of the welded sheets interactively. During FE simulation of impact forming, tensile data obtained from the unwelded section of the sheet deformed using the shock tube is fit to modified Johnson-Cook (MJC) model. In the case of the FS spot welded region, a hardness based multiplying factor is identified and used to obtain stress-strain data by fitting to MJC model. The predicted temperature evolution during the FSSW is validated with the experimental data and a good correlation has been observed. The predicted material flow phenomenon gives an insight about the joint formation during FSSW. Various forming outputs such as deformation profile, failure pattern and effective strain distribution predicted by MJC model in combination with Freudenthal damage model is compared with the experimental data and the results have a fair agreement.