简化脆性断裂裂尖模型及复合型断裂判据

通过对脆性断裂过程中开裂扩展机理的分析,提出一个新的简化脆性断裂裂尖模型,论证了裂尖荷载型式与裂尖断裂类型之间并不是惟一的对应关系,重新阐述和定义了裂尖处的应力强度因子和断裂韧度.通过对I型、II型及其复合型荷载作用下裂尖处应力场分析,提出了径向平面最大应力(M SRP)准则,认为在脆性断裂过程中,断裂方向由裂尖处径向平面上的最大应力所决定.分别针对I型、II型及I-II复合型荷载模式提出了裂纹断裂判断准则和开裂方向预测模型.通过推导得到了复合型荷载作用下严密完整的脆性断裂判据与裂纹开裂方向角的解析表达式,与有关脆性断裂试验结果进行的对比验证了所提出的模型及理论解的合理性.

A simplified crack tip brittle fracture model and fracture criterion for mixed mode of loading

Based on the analyses of crack extension mechanism for brittle fracture process, a simplified crack tip model in terms of an improved fracture mechanism is proposed.The non-correspondance between the modes of loading and the fractural types is demonstrated.The stress intensity factors and fracture roughness are redefined.Through analyzing stress field in the neighborhood of crack tip respectively under loading of Mode-I,Mode-II and mixed mode of Mode-I and Mode-II, it is indicated that the maximum stress is the predominant factor on which the extension direction of crack depends,the criterion named maximum stress on radial plane(MSRP) is presented,the analytical expression of criterion and analytical equation for the crack initiation angle are deduced.By comparison of theoretical solution with results from brittle fracture experiments,the theoretical rationality and feasibility of the proposed model and expression are verified.