摘要
经典断裂力学理论和成熟的设计规范都是基于二维断裂理论的,大部分实际裂纹问题的裂纹尖端附近的应力场是三维应力场,三维应力下的约束情况对材料的断裂行为有显著的影响。首先建立CT试样的有限元模型,通过模拟车钩铸造E级钢的断裂韧性试验来验证扩展有限元模型的准确性。然后,开展了不同厚度的表面裂纹平板拉伸载荷下的三维扩展有限元模拟,将利用扩展有限元方法得到的拉伸极限载荷与传统的应力强度因子达到断裂韧性K IC时的极限载荷进行了对比。并结合裂纹前缘塑性区尺寸的大小,对厚板情况下两种方法获得的结果差异较大的原因进行了讨论。结果表明:使用扩展有限元方法能够很好得对CT试样的断裂行为进行模拟。由穿透型裂纹CT试样获得的断裂韧性K IC计算出的极限载荷在三维裂纹情况下偏保守。由断裂韧性计算出的最大载荷与扩展有限元方法得到的最大载荷之间的差异随着板厚度的增加而增大,在计算厚板表面裂纹的极限载荷时必须考虑裂纹的三维约束效应。
Classical fracture mechanics theory and mature design codes are based on two-dimensional fracture theory.The stress field near the crack tip of most practical crack problems is three-dimensional stress field.The constraint condition under three-dimensional stress has a significant impact on the fracture behavior of materials.The finite element model of CT specimen is established firstly,and the accuracy of the extended finite element model is verified by simulating the fracture toughness test of E-grade steel cast on coupler.Then,the three-dimensional finite element simulation of the surface crack plate with different thickness under tensile load are carried out.The tensile ultimate load obtained by the extended finite element method is compared with the ultimate load when the traditional stress intensity factor reaches the fracture toughness K IC.Combined with the size of the plastic zone at the front of the crack,the reason of the great difference between the two methods was discussed.The results show that the extended finite element method can simulate the fracture behavior of CT specimen well.The ultimate load calculated by K IC is conservative in the case of three-dimensional crack.The difference between the maximum load calculated by the fracture toughness and the ultimate load obtained by the extended finite element method increases with the increase of the plate thickness.The three-dimensional constraint effect of the crack must be considered when calculating the ultimate load of the thick plate with surface crack.
作者
孙国栋
刘宇杰
康国政
SUN Guodong;LIU Yujie;KANG Guozheng(School of Mechanics and Engineering,Southwest Jiaotong University,Chengdu 610031,China)
出处
《四川轻化工大学学报（自然科学版）》
CAS
2020年第5期7-13,共7页
Journal of Sichuan University of Science & Engineering(Natural Science Edition)
关键词
扩展有限元法
表面裂纹
拉伸极限载荷
平板
extended finite element method
surface crack
tensile ultimate load
plate
