管线钢的反向应变率效应及剪切形变带

Negative Strain Rate Effect and Shear Deformation Band in Pipeline Steel

利用Hopkinson压杆加载装置对圆柱状热处理态X70管线钢试样进行了动态冲击压缩实验,研究了损伤微结构演化与宏观力学行为之间的对应关系。结果表明:在.ε≤2.5×103s-1条件下,以马氏体组织为主的淬火X70管线钢变形抗力及变形能力较差,当其内部损伤引起的材料软化起主导作用时,材料表现出反向应变率效应;在应变率高达2.5×103s-1变形条件下,淬火态X70管线钢产生了剪切形变带,并且带内及周围都出现了孔洞,带内硬度明显增加。

Dynamic impact compression experiments were conducted on column specimens of X70 pipe ine steel after heat treatment using the Hopkinson pressure bar. The correlation between struc tural evolution and the dynamic stress-strain behavior was investigated. The results show that the martensite dominated microstructure of X70 pipeline steel after heat treatment is remarkably weak ened and damaged under the strain rate lower than 2.5×10^3s^-1. When the weakening by internal damage rate-dependent evolution is dominated, negative strain rate effect occurs. Furthermore, at the strain rate as high as 2.5× 10^3s^-1 shear deformation band forms, voids in and around the band appear, and the hardness of shear deformation band obviously increases.