Numerical simulation based upon friction coefficient model on thermo-mechanical coupling in rotary friction welding corresponding with corona-bond evolution

Numerical simulation method was employed to reveal the mechanism of manufacturing a rotary friction welding joint, in which a two-dimensional finite element model was constructed based on a comprehensive friction coefficient model to simulate the thermo-mechanical coupling during rotary friction welding. Experiments were focused on rotary friction welding of SUS304 in diameter of φ25 mm at 900 rpm under 80 MPa, of which the joint were studied on evolutions of temperature field, stress fields (i.e., both stress-Z and effective stress) and tensile strength corresponding with the corona-bond evolution. Thereafter, the simulation focused on the effect of rotation speed that varied as 500–2500 rpm, in which the minimum welding time necessary to cover a welding cycle was issued. The finite element model was shown valid by the consistency of comparison between simulation and experiment. Transition temperature fields (in contours) were verified in good agreement with transition morphologies of the joints as experimentally characterized by the corona-bonds. The results show that, rotary friction welding process can be classified into two stages: the corona-bond evolution and the plastic flow. The former stage is characterized by the corona-bond that develops and fills out the interface, in which the temperature is kept raising and the stress field kept varying; whereas the latter stage is denoted by the extrusion of flash that keeps forming at constant temperature and stress fields (i.e., both stress-Z and effective stress). The tensile test reveals that the latter stage makes negligible contribution to the joint strength, which falls in the range as 660–688 MPa as the welding time is regulated from 1.8 to 15 s. Thus, time consumed on former stage was ascertained to be the minimum welding time, which ranges in 1.5–2.9 s for SUS304 in φ25 mm of diameter welded under 80 MPa at the rotation speed of 500–2500 rpm.