The corona bond response to normal stress distribution during the process of rotary friction welding

Continuous drive rotary friction welding was conducted on SUS304 stainless steel rods in diameter of ϕ25 mm under different welding pressures, rotation speeds, and friction time. At the friction interface, the normal stress distributions were measured, and the corona bond (i.e., plasticized metal) was characterized. The results show that, under a constant welding pressure, the normal stress initiates at the periphery of the sample interface, leaving the inner area that seems un-contacted at the very beginning of the friction process. Thereafter, the normal stress extends inside along the radial direction, which leads to its distribution presenting like a “U” shape. The normal stress at the periphery increases much faster than it at the inner area, resulting in the distribution presenting like a “V” shape. Then, the stress in the center continuously increases and the distribution gradually changes into “M” shape. The stress is lastly homogenously distributed. Evolution of the normal stress distribution determines the evolution of the corona bond. At the same time, evolution of the corona bond reacts on the distribution of normal stress. In addition, similar phenomena have been observed under different welding parameters.