Exciting Vibration Source Frequency (ladder) Disc Bending Vibration Characteristics

Longitudinal-flexural vibration composite transducer is used extensively in many fields of engineering and science. This system has characteristics with high power efficiency of a longitudinal vibration transducer and a large radiation area of a flexural vibration stepped circular plate. It is known as a longitudinal-flexural composite vibrating system, based on an extensive flexural-vibrating stepped plate that is driven at its centre by a longitudinal vibration transducer. The height of the stepped is equal to half a wavelength of the sound in the medium of propagation. The stepped profile of the plate is designed to properly compensate the zones vibrating in counter phase in order to control the acoustic field radiation.Ideally, in some previous papers, to achieve the best working conditions of longitudinal flexural composite vibrating system, the resonant frequency of longitudinal vibration transducer must be equal to that of flexural vibration of the plate. In high-power practical applications, some factors, such as the temperature, stiffness, load, tool wear, parts of the installation and other variables, always cause the system's natural frequency to drift and lead to degradation of the transducer's performances. The frequency of ultrasonic transducer had better equal to that of the plate in the theoretical calculation, but they occur inevitably in different frequencies in the practical application. Once the plate and the driving transducer do not have the same resonant frequency, the vibration characteristics of the plate, such as frequency characteristics, directivity and radiated field will change accordingly. This will low the efficiency of the system and cause serious damage to equipment.In such circumstance, longitudinal sandwich transducers with a certain area and different frequencies drive a (stepped) circular plate that produces the first-order flexural vibration by using of FEM, which are studied in this paper. Accordingly, the fundamental frequency, nodal circle and displacement distribution of the stepped plate with change of the driving frequency are obtained. The detailed work is as follow:1.The main research the first-order flexural vibration circular plate design methods, and the finite element calculation software research of excitation of the first flexural vibration frequency, the influence of the plate characteristics respectively from the radius of the nodal circle, the plate is the fundamental frequency and amplitude transverse displacement analysis.2. From thin plate theory research of the single step, and using the stepped plate design method finite element software to study the frequency of excitation of the first flexural vibration, the influence of the plate characteristics respectively from the radius of the nodal circle, the stepped plate is the fundamental frequency and amplitude transverse displacement analysis.3. the stepped plate radiation detector and of the transducer longitudinal vibration transducer longitudinal composite composed of the design optimization, using the finite element method to calculate, from experiment Angle to verify summarized and analyzed, got an incentive frequency make stepped plate the pitch circle under section of big incentives recovery in circle radius, the stepped radiation efficiency, directionality were improved.It is clarified that experimental results and the conclusions of numerical solution are in agreement. The conclusions are significant for both designers and applications.