Geometric and Physical Parameters Influence on the Resonant Frequencies of Ultrasonic Vibrations of a Medical Scalpel

Abstract

Resonance frequencies of the longitudinal oscillations are investigated for a system consisting of diverse geometrical and physical elements—piezoceramic, elastic, and acoustic ones. The results are compared in COMSOL and ACELAN packages. The dependence of the first eigenfrequency value on the geometric parameters is evaluated. The dynamic viscosity effect on the longitudinal oscillations near the first resonance frequency (FRF) is studied. The system of elastic and acoustic elements, which allows describing the operation of an ultrasonic cutting device, is selected for the study. The oscillator is a piezoelectric transducer, which oscillates in thickness. An oscillation concentrator and a rod element are specified as elastic elements. They are made from stainless steel. Possible model of the human body soft tissues is an acoustic fluid. Modal and harmonic analysis of a complex system consisting of diverse physical elements is carried out. Axisymmetric and three-dimensional finite element models of the investigated system are constructed. Various types of curvature and thickness of the link with changeable surface shape are proposed for the oscillation concentrator. The first eigenfrequencies of the longitudinal vibrations of the rod element contacting with the acoustic liquid are obtained. Good agreement with the results of the ACELAN finite-element package is established. The amplitude-frequency characteristics of the end oscillations near the first resonance frequency are obtained. It is notable that the acoustic medium viscosity has little effect on the oscillation amplitude of the elastic rod and does not affect the resonance frequency at all. Harmonic and modal analysis has shown that the high-frequency longitudinal vibrations of the rod element depend significantly on the dissipation factor of the elastic elements and depend weakly on the viscosity of the contacting acoustic medium. The results obtained may be of interest under designing ultrasonic cutting medical devices.