Research on ultrasonic assisted press-fit assembly of small interference fits

Interference fits are widely used in aerospace, precision instruments and other fields. Press-fit assembly is one of the traditional assembly methods for interference fitting parts. Wear during assembly will affect the performance of interference components and the service life of marine equipment. Ultrasonic assisted press-fit can significantly reduce the press-mounting force of an interference fit. However, its effect on connection quality is rarely studied. The mechanism of ultrasonic assisted press-fit is unclear. In this paper, ultrasonic assisted press-fit was simulated and experimentally studied. The effects of ultrasonic vibration on heat generation, press-mounting force, connection strength, and interface wear were analyzed and discussed. Through analogy analysis with similar ultrasonic assisted machining processes, the mechanism of ultrasonic assisted press-fit was revealed. The results show that the superimposed ultrasonic vibration can effectively reduce the joining force (up to 33.5%), and increase the connection coefficient from 10% to 40%. This is due to stress superposition, friction reduction and acoustic softening that reduces interface wear. The increase of the interface roughness Rz from 3.681 to 4.586 mu m confirms this analysis. Furthermore, the ultrasonic vibration can effectively reduce the material plastic flow of contact interface. This study reveals the significant advantages of ultrasonic assisted press-fit assembly (UAPA) method and provided a basis to understand the underlying mechanisms of UAPA.