Crack-healing behavior of structural ceramics under the conditions of tensile stresses and high temperatures

拉应力和高温条件下结构陶瓷的裂纹愈合行为

基本信息

批准号：
15360047
负责人：
ANDO Kotoji
金额：
$ 9.28万
依托单位：
Yokohama National University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15360047/
关键词：
Crack-healing Ceramics Silicon nitride Alumina Mullite Bending strength Fatigue strength Stress intensity factor

项目摘要

In this study, Si_3N_4/SiC, alumina/SiC and mullite/SiC composites having excellent crack-healing ability were selected to be test materials. Being introduced a surface-crack of 100 μm, they were then carried out the crack-healing treatment at elevated temperatures raging from 800 to 1200℃ to be applied tensile stress. Based on the strength of the specimens crack-healed under stress, crack-healing behaviors under stress were investigated. From the obtained results, the following conclusions were derived.1.The heat-treated specimens have same strength as smooth specimens. The cracked specimens could crack-healed under the tensile stress that is 70 to 80% strength of the cracked specimens. The specimens crack-healed under stress had the same strength as the heat-treated smooth specimen at the crack-healed temperature. Moreover, the crack-healed part had enough high strength, because fracture initiation was mostly outside the crack-healed part.2.The critical condition to be able to heal the pre-crack was estimated from the equation of the stress intensity factor expressed by Newman-Raju and the stress intensity factor of the residual stress for every specimen.3.The specimens crack-healed under static and cyclic stresses had enough high static and cyclic fatigue strengths at the crack-healing temperature. These values corresponded to 70-80% fracture strength of the crack-healed specimens.Based on the above conclusions, it is confirmed that Si_3N_4/SiC, alumina/SiC and mullite/SiC composites used in this study can heal cracks initiated in service if the temperature, stress and atmosphere conditions were adjusted.

本研究选取裂纹修复能力优异的Si_3N_4/SiC、氧化铝/SiC和莫来石/SiC复合材料作为试验材料,引入100μm的表面裂纹,并在100℃下进行裂纹修复处理。高温从800℃到1200℃施加拉应力根据应力下裂纹愈合的试件的强度，裂纹愈合。对应力下的行为进行了研究，得出以下结论：1.热处理后的试件具有与光滑试件相同的强度，在拉应力为70%～80%的拉应力下，裂纹可以愈合。在应力作用下裂纹愈合的试样与在裂纹愈合温度下热处理的光滑试样具有相同的强度，而且裂纹愈合部分具有足够高的强度，因为断裂起始大多在裂纹扩展之外。 2.通过Newman-Raju表达的应力强度因子方程和每个试件的残余应力的应力强度因子来估计预裂纹能够愈合的临界条件。3.在静态和循环应力下裂纹愈合的试样在裂纹愈合温度下具有足够高的静态和循环疲劳强度，这些值相当于裂纹愈合试样的断裂强度的70-80%。根据上述结论，证实本研究中使用的Si_3N_4/SiC、氧化铝/SiC和莫来石/SiC复合材料在调整温度、应力和气氛条件的情况下可以修复使用中产生的裂纹。