Parametric Study of Bolt Clamping Effect on Resonance Characteristics of Langevin Transducers with Lumped Circuit Models.

Jinhyuk Kim,Jungwoo Lee

doi:10.3390/s20071952

Abstract

We recently proposed a numerical model using equivalent circuit models to analyze the resonance characteristics of Langevin transducers and design them in a systematic manner. However, no pre-load torque biased by a metal bolt was considered in the model. Here, a parametric study is, therefore, carried out to reveal how model parameters are adapted to incorporate the pre-compression effect into our existing model. Analytical results are compared with corresponding experimental data, particularly regarding the input electrical impedance and effective electromechanical coupling coefficient for the transducer at resonance modes. The frequency response of input impedance is presented as a function of torque, both theoretically and experimentally. For 10.0 N·m bias, for instance, both resonance and anti-resonance frequencies are calculated as 38.64 kHz and 39.78 kHz, while these are measured as 38.62 kHz and 39.77 kHz by the impedance analyzer. The impedance difference between these cases is 14 Ω at resonance and 9 kΩ at anti-resonance, while the coupling coefficients in both cases become 0.238 and 0.239, respectively. Hence, these test results are closely matched with their theoretical values. Consequently, this study provides a quantitative guideline that specifies the pre-loading condition of bolt clamps with proper parameter settings to predict the intended resonance characteristics of Langevin transducers.

Highlights

Bolt-clamped transducers, known as Langevin transducers, are widely used, giving rise to a boosted ultrasound transmission for various industrial or medical applications including welding [1], cleaning [2], and liposuction [3]
We devised a systematic design approach based on equivalent circuit models to examine the resonance characteristics of therapeutic Langevin transducers [7]
Mason’s model consisting of two mechanical ports and one electrical port separated through an ideal transformer was used to describe the complex behavior of piezoelectric ceramics, while the T-network model was used to represent other passive parts of the transducer

Summary

Introduction

Bolt-clamped transducers, known as Langevin transducers, are widely used, giving rise to a boosted ultrasound transmission for various industrial or medical applications including welding [1], cleaning [2], and liposuction [3]. Carried out to propose design methods of Langevin transducers for such uses [4,5,6]. The typical transducer structure is composed of piezoelectric layers, front/back masses, a horn, and a metal bolt. A pre-stressed central bolt clamps one or more pairs of piezo-rings, made of lead zirconate titanate (PZT), with other acoustically passive elements in order to apply mechanical bias to the whole transducer. Mason’s model consisting of two mechanical ports and one electrical port separated through an ideal transformer was used to describe the complex behavior of piezoelectric ceramics, while the T-network model was used to represent other passive parts of the transducer. Design variables were inherent material properties of each element, e.g. their physical dimension, acoustic impedance, Sensors 2020, 20, 1952; doi:10.3390/s20071952 www.mdpi.com/journal/sensors

Methods

Results

Conclusion