40Cr材料动态起裂韧性KId（）的实验测试

描述了利用Ｈｏｐｋｉｎｓｏｎ压杆技术加载三点弯曲试样测试４０Ｃｒ，材料动态起裂韧性ＫＩｄ（）的试验方法。试样上的动态载荷历程由Ｈｏｐｋｉｎｓｏｎ杆直接测得，并分别代入动态有限元程序及近似公式求得动态应力强度因子历史；由贴在试样裂尖附近的应变片确定起裂时间，最终确定起裂时的动态应力强度因子值，即动态起裂韧性ＫＩｄ（）。试验结果表明:利用Ｈｏｐｋｉｎｓｏｎ压杆技术加载三点弯曲试样测试材料动态起裂韧性的方法是可行的，起裂时，动态有限元的位移法、应力法及近似公式法求得的动态应力强度因子值比较吻合；在本文的载荷速率下，４０Ｃｒ材料动态起裂韧性ＫＩｄ（）与准静态裂韧性ＫＩｄ（）相比，降低了约２８％。

EXPERIMENTAL MEASUREMENT OF DYNAMIC FRACTURE INITIATION TOUGHNESS OF 40Cr STEEL

In this paper,a testing method for measuring the dynamic fracture toughness of 40Cr material using three point bend specimen loaded with Hopkinson pressure bar is described. The loading applied to the specimen is determined from the pulse on the Hopkinson pressure bar. The dynamic stress intensity factor is calculated by means of finite element method and approximate formula respectively. The fracture time is measured using strain gauges mounted on the vicinity of the crack tip and the dynamic fracture initiation toughness is obtained based on the stress intensity factor history and the fracture time. The results show. that the testing procedure described in this paper is acceptable for measuring dynamic fracture initiation toughness under high loading rates.Over the loading rate range of this paper,the dynamic fracture toughness reduces about28% of the quasi-static fracture toughness.