【作者】 张顺峰；

【导师】 赵淳生；

【作者基本信息】 南京航空航天大学 ， 工程力学， 2011， 硕士

【摘要】 本课题来源于国家自然科学基金项目《压电精密致动技术的基础研究》(项目编号:50735002)。超声电机是一种基于压电效应和超声振动的高新技术产品。由于复杂的工作环境,超声电机中的压电陶瓷非常容易受到环境的影响而产生断裂失效,从而导致超声电机无法正常的工作。针对这一现象,本文通过简化超声电机定子为一弹性复合梁,研究环境对压电陶瓷断裂失效的影响,主要内容及成果如下:综述了超声电机的发展历史,总结了现在超声电机工作中出现的断裂失效现象,并针对其工作的原理、结构和环境因素,提出了弹性复合梁的结构模型,确定了本课题的研究方向和内容;分析指出了影响超声电机工作稳定性的原器件以及系统环节,介绍了压电陶瓷两种主要的失效类型:电致失效和多场耦合失效,并将两种主要的失效现象机械断裂失效和电击穿失效进行了对比分析。对含导通裂纹的各向同性电介质的临界击穿电场进行了推导。对含预制裂纹的弹性复合梁进行了仿真计算,通过对不同位置预制裂纹的裂纹尖端应力分布的分析,得到极化区间内中间贯穿裂纹最易发生裂纹扩展。通过对压电陶瓷施加不同电压载荷、不同预载荷和温度载荷的弹性复合梁的仿真计算得到:电场增大促进裂纹的扩展,预载荷增大引起应变增大,促进了裂纹的扩展。而温度升高抑制裂纹的扩展。在仿真计算的基础上对各个不同边界条件的压电陶瓷进行了J积分的计算,结果表明当电压载荷和预载荷增大时,J积分值不断增大;当温度载荷增大时,J积分值不断减小直至稳定。最后,通过实验证实:电场载荷增大容易促进裂纹的扩展,预载荷增大引起裂纹应变减小,抑制了裂纹的扩展,施加的温度载荷越高裂纹越不容易发生扩展。更多还原

【Abstract】 This project was granted by the project of the National Natural Science Foundation of China. (Contract No: 50735002).Ultrasonic motor is a high-tech product based on the piezoelectric effect and ultrasonic vibration. Due to the complex service environment, cracking or fractures may often exist in piezoelectric ceramic of ultrasonic motor so that the ultrasonic motor can not work normally. In the present work, the stator of the ultrasonic motor was modeled as an elastic-composite beam, and then studies on the fracture and failure of the piezoelectric ceramic are made theoretically and experimentally. Main content and results are as follows:The developing history of ultrasonic motor was summarized, and the fracture and failure phenomenon in the ultrasonic motor then was pointed out. According to the working principle structure of the ultrasonic motor and its working environment, the elastic-composite beam structure model was developed, and the following works were completed:The devices and the other factors which influence the working stability of ultrasonic motor were pionted out. The main mechanism of failure and two main failure types were expounds. The two main failure phenomena (mechanical fracture failure and electric breakdown failure) were compared. Critical breakdown electric field was also derived.Simulation calculation was done to the elastic-composite beam that contains a prefabricated crack. It is found, from the stress distribution at the crack tip in the samples with prefabricated cracks at different position, that the middle throughout crack is the easiest to propagate in the polarization interval. Through the simulation results for the piezoelectric ceramics under different voltage, preloading value and temperature applying at the elastic-composite beam,it is obtained that the electric field and preloading can promote the crack growth, while the temperature retard the crack growth.J integral was made on the basis of simulation calculation of different boundary conditions for the piezoelectric ceramic.It is found that the J integral value increases constantly as the electric field and preloading value increases, but it constantly decrease and finally reaches a stability value as the temperature increases.Eexperimental works about the faliue of piezoelectric materials with cracks are also conduceted, and it is found that increasing the electric field can promote the crack growth, and the decreasing of strain which causes by preloading restrain the crack gracks, while as the temperature becomes higher, the crack trends to close, which is consistent with the above theoretical predications.更多还原