中文摘要：

针对异型坯生产中出现较多表面裂纹的问题,在前期铸坯凝固过程热力行为研究基础上,提取凝固坯壳的温度与应力数据,使用扩展有限元方法,结合材料损伤力学、子模型技术模拟预制表面裂纹的扩展情况。研究结果表明：在裂纹尖端区域出现应力集中,应力值明显高于无裂纹位置;当应力集中区域最大主应力达到临界值时单元开裂,裂纹扩展。R角处预制纵裂纹扩展量最大,与拉坯方向呈75°、45°裂纹次之;预制表面横裂纹在沿横向扩展一个网格后扩展方向出现弯折,裂纹最终扩展方向均为沿纵向。

英文摘要：

Aimed at surface cracks problem of beam-blank in production process, a two-dimensional thermal-mechanical model was set up, the extension of surface cracks was simulated. During this process, the damage mechanics theory ＆XFEM ＆ level set method were used. The results show that stress concentration appears at the tip of the crack, the level of stress is higher than other positions, the crack extend forward once when the max principal stress reaches the limit. The prefabricated cracks in different directions extend along the rolling direction mainly, the length of crack extension in descending order is as follows： the longitudinal surface crack, the 75°, 45° direction with the direction of casting speed.