单边偏置裂纹相互作用的实验研究

Tests for interaction of unilateral offset cracks

为研究脆性介质中裂纹相互作用对裂纹扩展形态的影响,以有机玻璃(PMMA)为相似材料,采用动态焦散线实验方法开展了三点弯冲击动力学实验研究。结果表明:冲击荷载条件下,裂纹间相互作用影响裂纹起裂时间、裂纹尖端应力场以及裂纹偏转方向。裂纹相互作用使得裂纹起裂时应力强度因子K d I降低,起裂所需能量累积时间缩短;裂纹扩展初始阶段,单偏置裂纹尖端应力场剪应力分量为正,应力强度因子K d II大于0,单边偏置平行双裂纹相同位置处裂纹尖端应力场剪应力分量为负,K d II小于0;裂纹距离中心位置10 mm的情况下,单偏置裂纹起裂后向内侧偏转,单边偏置平行双裂纹相同位置处裂纹向外侧偏转。

Here,in order to study effects of cracks interaction in brittle medium on crack growth morphology,the dynamic caustics method was used to conduct 3-point bend impact dynamic tests taking PMMA as a similar material.The results showed that under the condition of impact load,cracks interaction affects crack initiation time,crack tip stress field and crack deflection direction;cracks interaction causes decreases in stress intensity factor K d I during crack initiation and time required for crack initiation energy accumulation;in initial stage of crack propagation,shear stress component of single-offset crack tip stress field is positive and stress intensity factor K d II is larger than zero,while shear stress component of crack tip stress field at the same position of unilateral offset parallel double cracks is negative and K d II is less than zero;when crack position is 10 mm away from center position,a single-offset crack deflects to inside after its initiation,a crack at the same positon of unilateral offset parallel double cracks deflects to outside.