High Temperature Fatigue Crack Growth in Silicon Nitride and Role of SCC.

氮化硅中的高温疲劳裂纹扩展和 SCC 的作用。

• 批准号: 02650054
• 负责人: MUTOH Yoshiharu
• 金额: $ 1.22万
• 依托单位: Nagaoka University of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1990
• 资助国家: 日本
• 起止时间: 1990 至 1991
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-02650054/
• 关键词: Ceramics; Silicon Nitride; Fatigue Crack; Crack Growth Rate; Bridging; High Temperature; Stress Corrosion Cracking; 応力波形; Ceramics; Silicon Nitride; Fatigue Crack; Crack Growth Rate; Bridging; High Temperature; Stress Corrosion Cracking; 応力波形

(1) During crack growth in silicon nitride, microcracking on weak grain boundaries and subsequently bridging occur. The acceleration of crack growth rate in cyclic fatigue compared to the case in static fatigue will result from that the bridges are fractured and removed by cyclic deformation.(2) The crack growth behavior in silicon nitride is strongly affected by the history of crack growth due to formation of the bridges. So, the crack growth rate can not be given uniquely by the applied K-value.(3) The crack tip stress intensity factor K-tip, which is given the actual stress field at the crack tip country on the effect of stress shield by the bridging, can be estimated by reducing the K at crack tip from the measured crack mouth opening displacement. The unique relationship between K-tip and crack growth rate is found independent of the history of crack growth.(4) The orientation of silicon nitride grain in the tensile direction in the high strain region at the crack tip was observed at the temperatures over 1200ﾟC, which corresponds to the softening point of the grain boundary glass phase. The transition of fracture mechanism was observed from brittle intergranular to ductile pulling out of grain with shear deformation of boundary glass phase.

（1）在氮化硅裂纹生长过程中，微裂纹在弱晶界和随后的桥梁上进行。与静态疲劳的情况相比，环状疲劳的裂纹生长速率的加速性将导致桥梁被骨折并通过循环变形来清除。（2）氮化硅的裂纹生长行为受到桥形成裂纹生长的历史的强烈影响。因此，裂纹的生长速率不能由施加的k值唯一给出。（3）裂纹尖端应力强度因子k-tip（在裂纹尖端国家通过桥梁的效果）给出了裂纹尖端的实际应力场，可以通过从裂纹尖端从测量的裂纹裂纹口张开的裂纹尖端减少k来估计。发现K-TIP和裂纹生长速率之间的独特关系与裂纹生长的历史无关。（4）在高应变区域在裂纹尖端的高应变区域在1200 c的温度下观察到氮气在高应变区域中的方向的方向，这对应于晶粒边界玻璃相的软化点。从脆性间间到延性的裂缝机制的过渡，并从晶粒中脱离边界玻璃相的剪切变形。