Due to the large stress concentration at the root of the external thread, fatigue failure is apt to occur when subjected to alternating loads. In present study, to improve the fatigue resistance of threaded components, an ultrasonic rolling method was used to strengthen the surface structure of the root of external threads. Parameters of the Ultrasonic Surface Rolling Process (USRP) were optimized based on Response Surface Model(RSM) method, and the optimization objectives are surface roughness, surface hardness, surface residual stress, and a combination of these three factors, respectively. The strengthened threaded components were then subjected to tensile-tensile fatigue tests. Results show that the fatigue life of threaded parts after ultrasonic rolling are significantly improved compared to the original samples, with an average improvement of more than 10 times.
Liu et al. (Tue,) studied this question.