超音波振動系統在高溫下之有限元素分析

Abstract

近年來，超音波振動輔助加工廣泛應用於塑性成形，藉由超音波振動的振幅引起模具與工件之間的相互振動與摩擦，可提高工件表面的溫度，使材料成形性提高，降低成形時所需之壓力。若將超音波系統作用於高溫下，結合熱壓、熔接、切削研磨等製程，更可製造出高精度與高品質兼具的產品。 本研究利用有限元素軟體ANSYS對超音波振動系統進行高溫下的分析，並考慮換能器中陶瓷壓電片的性質及超音波放大器在高溫下的材料特性，先對振動系統進行熱傳分析，得到系統之溫度分佈後，對加溫後的超音波振動系統進行模態分析以及頻率響應分析，得知此振動系統在不同溫度下的共振頻率及振幅分佈，探討溫度與共振頻率及振幅的關係。最後將模擬結果與實驗結果相互驗證，以確認本研究所提出之超音波振動系統在高溫下之有限元素分析模型。後續將可利用此模型輔助設計超音波振動系統，以提升超音波應用於高溫製程的發展性。

In recent years, the ultrasonic vibration assisted manufacture is widely used in plastic forming. The vibration brings about the friction between mold and workpiece, therefore, the surface temperature of the workpiece is raised. It can improve the material formability and reduce the forming pressure. If some manufacture processes such as embossing, welding, cutting or grinding process were combined with ultrasonic vibration system at high working temperature, products with both high precision and high quality can be obtained. In this study, an ultrasonic vibration system with high working temperature was analyzed by finite element software ANSYS. This analysis considered the piezoelectricity of the transducer as well as the material properties of the horn at high temperature. The temperature distribution was first calculated by thermal analysis. After that, this temperature distribution was input as an initial condition for modal analysis and harmonic response analysis. The resonance frequency and the vibration amplitude were obtained during the analyzing process, and the relationship between frequency, amplitude and temperature were also observed. Finally, the simulation results were compared to experimental measurement, to confirm the validity of the numerical analysis. The finite element model can be used in the components design of the ultrasonic vibration system with elevated temperature.