Experimental and numerical investigation of the generated heat in polypropylene sheet joints using friction stir welding (FSW)

In this paper, we aim to investigate the heat generated during friction stir lap welding in polypropylene sheets. In this method, the generated heat significantly depends on the tool’s rotational and linear speed, geometry, and tilt angle. Heat analysis and measurement during welding are performed numerically to validate the experimental results. A 3-D symmetric Finite Element (FE) model was created to estimate the generated and distributed heat. As is shown, the heat is mainly generated around and underside the tool due to the high friction between the rotating tool and the workpiece. This paper provided a good intuition on the generated and distributed heat during the FSW process, which can be considered a reference to produce optimum and high-quality products with fewer tests. Therefore, in this paper, the effect of a number of parameters on the generated heat during the welding process is studied experimentally and statistically and simulated in three different levels. The obtained results demonstrated a significant relationship between the properties and process parameters using analysis of variance (ANOVA) and response surface method (RSM) (Box-Behnken). Moreover, the results revealed that the effect of parameter interactions could be evaluated using the proposed mathematical model by analyzing the presented plots. In addition, the results from the simulated model using finite element software and Altair’s HyperWorks confirmed the mathematical model estimations and the experimental results. The created model can successfully predict 92% of the welding joint temperature using the conditions and materials proposed in this paper. The results of the simulation analysis were validated and compared with the experimental tests, indicating a temperature difference of approximately 6%. The most effective parameter in heat generation is the rotational speed of the tool, which is responsible for up to 70% of the overall heat. Tool’s geometry (15%), traveling speed (11%), and tilt angle (4%) are the other parameters effective in generating heat in the process, in respective order.