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

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。目前的研究目标是开发工程陶瓷的高温度强度测试系统，该系统已与新开发的精确置换测量系统匹配：该测试系统是由激光束类型置换测量系统构建的，专门设计的电气设施，由硅-氮基陶瓷和镍基超级合金和封闭的环路类型材料测试系统组成的。在使用此测试系统的四点弯曲测试中获得的主要结果是，使用该测试系统将其汇总为后续。在目前的研究中开发的置换测量系统可能会在1，000 ° C以上测试温度下检测到200-300微米的置换量，硅-腈陶瓷的精确度约为2%的置换量。硅基氮基陶瓷显示测试温度低于1，100 ° C的负载P和置换之间的线性关系。P与.关系，不管怎样，从置换轴的积极方向出发，从上方的线性关系中脱离出来。这是一个关于硅腈陶瓷产品在这些温度下的塑料变形的建议。柔韧性强度在从房间温度到1，000 ° C的测试温度范围内仍然没有变化。这一数值在1，100 ° C左右达到最大值，然后在测试温度超过1，200 ° C时明显下降。根据Chevron缺口类型规格的测定法，裂纹强度的测量接近于房间温度到1，100 ° C，然后在1，100 ° C左右达到最小值。Thus，Silicon-Nitride陶瓷展示了测试温度中最低的断裂强度，达到最大强度。

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.