Effects of material properties and geometry on the vibration modes of dental ultrasonic instruments - finite element analysis

• Main Authors: Wei-Hao Lin, 林威豪
• Other Authors: Chun-Pin Lin
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/tj7qfy

碩士 === 國立臺北科技大學 === 製造科技研究所 === 103 === 　　Nowadays, ultrasonic instruments have been widely used in the field of dental medical. Natural frequency and modal shape are important parameters for designing the ultrasonic instruments, which are collectively called as &;quot;modal&;quot; in general. Using finite element analysis to predict the modal of structure has been widely used in various fields. This study utilizes finite element method to analyze the modal of dental ultrasonic instruments and to investigate the effects of geometry and material properties on the modal, thereby providing reference and application for design and analysis of the ultrasonic instruments. 　　This study was divided into two parts. The first part was to discuss the effects of the change of geometry on the modal of the ultrasonic instruments. The results indicated that the generation of the natural frequency with similar mode shapes is in a downward trend when the length of the instruments increases. The second part was to discuss the effects of the change of material properties on the modal of the instruments, wherein the discussion was performed by aiming at density, Young’s modulus and Poisson’s ratio. The results indicated that the generation of the natural frequency with similar mode shapes is in a downward trend when the density increases. On the contrary, the generation of the natural frequency with similar mode shapes is in an upward trend when the density decreases. The Young’s modulus is in an opposite trend in comparison with the density. The generation of the natural frequency with similar mode shapes is in an upward trend when the density increases. On the contrary, the generation of the natural frequency with similar mode shapes is in a downward trend when the density decreases. The change of the Poisson’s ratio does not affect the natural frequency greatly. 　　According to the results of modal analysis, the situation that the ultrasonic instruments driven by a transducer was simulated by steady-state dynamics - modal superposition analysis, thereby obtaining related information with physical meanings. This study discussed input amplitude and damping ratio. The results indicated that when input amplitude is larger, the output displacement is larger. When the damping ratio is larger, the output displacement is smaller. 　　Through the analytical methods of this study, the construction of an ultrasound transducer can be ignored, so that a simple way is used to simulate that the ultrasonic instruments are driven by the ultrasonic transducer, thereby avoiding the tedious construction of transducer mode. 　　All above results are synthesized to hopefully provide reference and application for the related ultrasonic instrument design in the future.