中文摘要：

为了研究微观因素对铸铁材料极限强度的影响，根据材料的破坏机理，提出了一种宏、微观跨尺度裂纹扩展模型，该模型可描述材料从微观缺陷到宏观断裂的过程。模型中初始微观缺陷大小及3个尺度效应函数，代表着微观因素对破坏过程的影响。进行了铸铁试件的单向拉伸试验，根据试验数据，采用打靶计算，拟合出了模型中的2个材料特性参数。对铸铁试件的拉伸极限强度进行了计算，计算结果与铸铁件拉伸极限强度的试验数据完全吻合。研究结果表明，极限强度值受微观因素影响具有一定的离散性，可由模型得到正确反映。最后通过数值模拟计算，探讨了微观因素对材料破坏过程的影响。

英文摘要：

In order to investigate the influence of microscopic effects on the extreme strength of cast iron material , based on the failure mechanisms, a macro/micro trans-scale crack growth model is developed to describe the whole process of a failure process from a microdefect to final fracture at the macroscopic scale. Three scale transitional functions as well as the size of initial micro-defect in the proposed model represent the microscopic effects in a fracture process. Uniaxial tension test is performed for the cylinder specimens of cast iron material. Two other material parameters in the model are determined from the test data. The extreme strength is calculated and the calculated results are completely same as the test results. In addition, the scatter of extreme strength owing to microscopic effects can be accurately depicted by the proposed model. Numerical simulations are carried out to investigate the influence of microscopic effects on the fracture process.