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A development of new displacement measuring system for evaluating the strength of fine ceramics at elevated temperatures

开发用于评估高温下精细陶瓷强度的新型位移测量系统

基本信息

批准号：
61850018
负责人：
HATANAKA Kenji
金额：
$ 3.52万
依托单位：
Yamaguchi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1987
项目状态：
已结题

项目摘要

It is needed to measure precisely the displacement produced on a specimen by loading at elevated temperatures for the reliable evaluation of the strength of engineering ceramics. The present study aims to develop the high temperature strength testing system of engineering ceramics which is equipped with the precise displacement measuring system newly devised : The testing system was constituted by the laser beam type displacement measuring system, the specially designed electric furnace, the jigs made of Silicon-Nitride ceramic and Ni-base super alloy, and the closed loop type material testing system. The main results obtained in the four-point bending test of the Silicon-Nitride ceramic by using this testing system are summarized as follows.1. The displacement measuring system developed in the present study makes it possible to detect the displacement of 200-300 um yielded on the Silicon-Nitride ceramic with the precision of about 2% of the displacement measured at test temperatures over 1,000゜C.2. The silicon-nitride ceramic shows the linear relutionship between load P and displacement at test temperatures below 1,100゜C . The P vs. relation, however,deviates from the above linear relationship in the positive direction of displacement axis. This suggests that the Silicon-Nitride ceramic produces plastic deformation at these temperatures.3. The flexural strength remains unchanged in test temperature range from room temperature to 1,000゜C. This reaches the maximun value around 1,100゜C, and then decreases drastically at test temperatures over 1,200 ゜C. The fracture toughness measured by the chevron notch type specimed is nearly constant over test temperatures from room temperature to 1,100 ゜C, and then this reaches the minimun value around 1,100 ゜C. Thus, the Silicon-Nitride ceramic exhibits the minimum fracture toughness around test temperature where the flexural strength reaches the maximum.

为了对工程陶瓷材料的强度进行可靠的评估，需要精确地测量高温加载时试样上产生的位移。本研究的目的是研制工程陶瓷高温强度测试系统，该系统配备了新研制的精密位移测量系统：测试系统由激光式位移测量系统、专用电炉、氮化硅陶瓷和镍基高温合金夹具以及闭环式材料测试系统组成。利用该测试系统对氮化硅陶瓷进行了四点弯曲试验，取得的主要结果如下：1.在本研究中开发的位移测量系统使得有可能检测在氮化硅陶瓷上产生的200-300 μ m的位移，其精度约为在超过1，000 ℃的测试温度下测量的位移的2%。氮化硅陶瓷在低于1,100 ℃的试验温度下显示出载荷P与位移之间的线性关系。但是，P与位移轴的关系在位移轴的正方向上偏离上述线性关系。这表明氮化硅陶瓷在这些温度下产生塑性变形。在室温至1，000 ℃的测试温度范围内，弯曲强度保持不变。这在1，100摄氏度左右达到最大值，然后在超过1，200摄氏度的测试温度下急剧下降。用V形切口型试验机测得的断裂韧性在室温至1,100 ℃的试验温度范围内几乎是恒定的，然后在1,100 ℃左右达到最小值。因此，氮化硅陶瓷在弯曲强度达到最大值的测试温度附近表现出最小的断裂韧性。