STRESS ANALYSIS AND GEOMETRICAL CONFIGURATION SELECTION FOR MULTILAYER PIEZOELECTRIC DISPLACEMENT ACTUATOR

Multilayer piezoelectric ceramic displacement actuators are susceptible to cracking in the region near the edge of the internal electrode, which may cause system damage or failure. In this paper, the stress distribution of a multilayer piezoelectric composite is investigated in a working environment and the optimized geometrical con?guration of the piezoelectric layer is obtained. The stress distribution in the structure and the stress concentration near the edge of the internal electrode, induced by non-uniform electric ?eld distribution, are analyzed by moir′e interferometry experiment and ?nite element numerical simulation. Based on the above analysis, two optimized geometrical models are presented for the purpose of geometrical con?guration selection, with which stress concentration can be reduced signi?cantly while the feasibility of the machining process and the basic structural functions occurring in the conventional model are retained. The numerical results indicate that the maximum stress in the optimized models is e?ectively diminished compared to the conventional model. For instance, the peak value of the principal stress in the optimized model II is 93.1% smaller than that in the conventional model. It is proved that stress concentration can be e?ectively relaxed in the latter of the two optimized models and thus the probability of fracture damage can be decreased.

精彩一“刻”——谈谈光盘刻录机

为了便于信息化教学，各个学校纷纷建设自己的资源库，文件传递的需求越来越多。而随着网络的普及，小型文件可以由快捷方便的网络发送，。很多电脑已经不再把软驱作为标准配置，于是古老的软盘驱动器就悄悄地退出了历史舞台。但是，移动存储的需求还是存在，比如动辄几百兆的影音文件的共享交换，大量的教学用数据的保存等等。这只有依靠大容量的移动存储设备了。流行的大容量移动存储设。备有大容量软驱(ZIP，LS120)、便携式硬盘、MO、CD-R、CO-RW等。不过作为低价格高容量的数据存储介质，还是光盘的使用最广泛。而光盘刻录机的不断降价也使得学校、个人刻录专用的数据碟、音乐碟或者VCD影礤成为现实。特别是近来某些大厂以特别优惠的价格甩卖较低档次的老型号刻录机，更在市场上引起一阵抢购热潮。本文主要对CD-RW作一介绍。