不同环境对玻璃渗透氧化铝陶瓷亚临界裂纹扩展的影响’

、目的：研究口腔临床修复中常用的玻璃渗透氧化铝陶瓷（IA，In-CeramAlumina，IA）在干燥环境和潮湿环境下的亚临界裂纹扩展（SCG）行为的区别。方法：通过三点弯曲强度测量方法测得15个IA样本的强度数据，采用循环疲劳测试法测出干燥环境下15个IA样本以及在潮湿环境下15个IA样本的循环疲劳断裂次数数据；SCG行为通过裂纹扩展速率和应力强度因子（K1）的函数关系来描述。结果：不同环境下IA在循环载荷下发生亚临界裂纹扩展后导致材料断裂，在干燥环境下应力强度因子K1为临界应力因子Knc面的46％时发生裂纹传播；在潮湿环境下应力强度因子K1为临界应力因子Knc的40％时发生裂纹传播。结论：IA在循环载荷下存在SCG行为，当应力强度因子相同时，潮湿环境下样品的裂纹扩展速率较大，说明潮湿环境能加速亚临界裂纹扩展，符合口腔的实际情况。

Effects of Different Environment on Subcritical Crack Growth of Glass-infiltrated Alumina-based Dental Ceramics.

Objective： To evaluate subcritical crack growth（SCG） under cyclic loading of glass-infiltrated alumina -based（IA, In-Ceram Alumina） in dry and wet environment. Methods： Bar-shaped specimens of IA（n=45） were fabricated and loaded in thre-point bending （3p） and cyclic fatigued （F）in dry and wet conditions. The initial and the number of cycles to fracture were obtained from（3p）and F test respectively. The behavior of SCG was de scribed in terms of crack velocity as a function of stress intensity factor （K1）. Results： IA was prone to SCG under different environment,with crack propagation occurring at Kic as low as 46 %and 40% of its critical stress intensity factor （Knc） under dry and wet environment respectively. Conclusion： Glass-infiltrated alumina-based dental ce ramics cause pronounced SCG. The subcritical crack growth velocity of wet specimen is speeded at same stress in tensity factor of air specimens, which implies that wet environment speeds up the subcritical crack growth. The re sults correspond to oral practice.