相互贯通裂纹动态断裂的试验研究

Tests for dynamic fracture of interconnected cracks

为了研究动荷载作用下裂纹角度对相互贯通裂纹动态断裂特性的影响,采用动焦散试验系统进行了含预制裂纹的三点弯冲击试验。试验结果表明:两分支裂纹相互贯通,在动荷载作用下翼裂纹只会从与竖直方向夹角较小的分支裂纹尖端起裂扩展,当有一支分支裂纹起裂后,另一分支裂纹动态应力强度因子快速下降,试件内应变能重新分布;起裂的翼裂纹首先沿准竖直方向扩展,当扩展到试件约2/3高度后,翼裂纹扩展速度下降,扩展轨迹弯曲程度加大,I-II复合型断裂明显;分支裂纹起裂瞬间的KdI和KdII随着该裂纹与竖直方向夹角θ的增加而增大,其扩展的平均速度随着夹角θ的增加而减小。

In order to study effects of crack angle on dynamic fracture properties of interconnected cracks under dynamic load, the impact tests of three-point bending beams containing pre-cracks were conducted with a dynamic caustics test system. Test results showed that when two branch cracks are interconnected, a wing crack only initiates and expends from the tip of the branch crack with a smaller angle to the vertical direction under dynamic loading; after one branch crack initiates,the other branch one ’ s tip dynamic stress intensity factor quickly drops down and the strain energy redistributes in the specimen; the initiated wing crack firstly expends along the quasi-vertical direction; the wing crack expending speed decreases, and the bending level of the expending trajectory increases, and I-II complex fracture phenomenon is obvious after the wing crack extends to about 2/3 of the specimen height; with increase in angle between the branch crack and the vertical direction, Kf and Kd[{ of the branch crack at initiation moment increase, but the average expending speed of the wing crack decreases.