The formation of tunnel defects and their prediction have received far less attention than flow behavior in friction stir welding (FSW) operations, even though the former has been the subject of substantial study. Rotational velocity, plasticized area, and defect generation were the variables examined in this research. The formation of a tunnel defect significantly degrades the mechanical welding capabilities of FSW. Variations in welding settings may lead to weld flaws due to inadequate plasticized material flow and incorrect heat input. This research examined the tunnel generation in FSW butt joints of AA 5052‐H34 in three different bonding parameter scenarios. Tensile and bending tests, together with the use of (ANSYS) software to calculate the stress concentration factor, were used to assess the impact of tunnel formation. There were reports of tunnels appearing in the welded zone in Cases 2 and 3. Case 1 showed the greatest improvement, with a 65% increase in tensile strength compared to Case 2. Case 1 yielded 3.7 kN, representing the maximum force of bending. The most important component in preventing tunneling development is controlling thermal energy, which can be achieved by carefully monitoring the ratio of tool circulation to traverse velocity. A comparison of several weld schedules and an evaluation of the possibility of tunnel formation in an actual weld are both possible applications of the findings, as deemed possible.
Mejbel et al. (2026) studied this question.