Elastic contact problem of the piezoelectric material in the structure of a bolt-clamped Langevin-type transducer

Abstract

Bolt-clamped Langevin-type transducers (BLTs) are widely used in various fields of industrial application of high-power ultrasonics. One of the most crucial points in designing a transducer of this type is estimation of the bearing stress imposed by clamping on the interface between the metal block and the piezoelectric element. This prestress, which compensates for low tensile strength of the piezoelectric materials used, must be larger than the dynamic vibratory stress at the interface between the components in high-amplitude operation. Precise estimation of it is virtually impossible, owing to an intricate elastic contact problem. However, with the use of the unique finite-element-analysis system developed by one of the authors, approximate solutions of the problem have been obtained. A BLT design based on the results of the prestress calculations is proposed. The results of its experimental verification have also been reported.