Analysis of screw pitch effects on the performance of bolt-clamped Langevin-type transducers

Abstract

Bolt-clamped Langevin-type transducers (BLTs) are common vibration sources in high-power ultrasonic applications such as ultrasonic plastic joining. In this paper, the authors propose a low-aspect-ratio BLT shape based on numerical solutions of a complex elastic contact problem concerning the bearing stress (prestress) imposed on the interfaces between the parts by clamping with the screw bolt. The prestress distribution at the interface has significant influence on the mechanical quality factor $\mathrm{(Q)}$ of the BLT. It is found that the screw pitch of the clamping bolt heavily affects the prestress distribution in the simulation using the finite element method. The newly developed BLTs with a high resonance frequency of approximately 80 kHz has a relatively wide radiating face and sufficient volume ratio of the piezoelectric elements that convert electrical energy into mechanical energy. The average of their measured $Q$ values exceeds 1000 despite their high resonance frequency when they are driven at a voltage higher than 17 V rms.