Characteristics of potential sources-vertical force, torque and current on penetration depth for quality assessment in friction stir welding of AA 6061 pipes

Abstract

Abstract – Friction stir welding of the pipes or curved bodies in aerospace components is tedious due to complex geometry, and hence, research articles related to it are rare. Primarily, this research investigated the nature of vertical welding force, torque and current on the weld quality during the friction stir welding of Aluminium 6061 (AA 6061) pipe at different penetration depths – 1.4 mm, 1.54 mm, 1.66 mm, 1.7 mm, 1.9 mm and 2 mm. The feed rate and rotational speed were set fixed at 1 mm/s and 1800 rpm respectively. The weld quality was evaluated using visual inspection and tensile test. From the results, penetration depths from 1.7 mm to 2 mm were suitable for producing quality welds on a specimen with 2 mm thickness, which resulted in fewer shoulder marks, and percentage reduction of strength less than 25.61% compared to the base metal. Friction stir welding using penetration depth of 1.4 mm has resulted in a weld, with excess shoulder marks and 43.84% of reduction in strength, which is not acceptable. Also, the range of penetration depths (1.7 mm to 2 mm) for which the force remains constant is recommended for producing quality welds. While torque and power increased linearly with the penetration depth, the distribution of the current remained the same for different penetration depths. However, the current consumption varied significantly in each of the friction stir welding stages clearly distinguishing the tool penetration, dwell time, traverse tool movement and tool pull out. The experimentation was successful in laying the foundation for the process parameters signifying the importance of penetration depth.

Keywords Friction stir welding (FSW), AA 6061 pipe, penetration depth, vertical force, torque, current consumption