Investigation of Material Movement in Friction Stir Welding with Plasticine as an Analogue

Friction stir welding (FSW) is a sustainable solid-state joining process used in the aerospace, automotive, and shipbuilding industries. The success of the FSW depends on the flow of the softened material during the process. Understanding the plastic deformation is essential for attaining an optimized weld structure, necessitating a comprehensive explanation based on the flow dynamics. The number of preliminary trials using metal to determine the final process window consumes material, energy, and other resources to a considerable extent. The current investigation examined material movement and the mechanism of weld formation in the weld structure during FSW in a sustainable way. Homemade clay, referred to as plasticine, was utilized as a substitute to simulate material movement in FSW. Various colors of plasticine were merged to better visualize the flow in a weld. Several welds were performed using plasticine, employing different rotational speeds and tool shapes. The cross-sectional cuts from the plasticine welds revealed that extensive mixing was not present at lower tool rotational speeds, and the original boundary between the advancing and retreating side workpieces was identifiable. To enable a quantitative assessment of the mixed region composition in the weld, color calibration consisting of red, green, and blue values of digital images was obtained by mixing different colors with known mass proportions.