基于数字图像相关方法的鲁灰花岗岩断裂特性研究

Study of fracture characteristics of Lu-grey granite based on digital image correlation method

采用单边直裂纹三点弯曲梁（SC3PB）对鲁灰花岗岩I型裂纹的断裂特性进行了实验研究,得到其断裂韧度为0.9~1.4MN/m1.5。基于数字图像相关方法（DIC）分析了峰值载荷前试件断裂位移场及应变场的演化过程,根据位移场的不连续性给出过程区的扩展轨迹,由应变场得到了高应变区域的变化规律。当局部水平位移梯度发生剧烈变化时,鲁灰花岗岩I型断裂进入过程区;且以水平方向应变达到0.11%~0.20%时作为进入过程区的门槛值;并进一步给出了过程区尖端沿竖直方向的扩展速率与过程区长度呈三次多项式递增关系。

Fracture characteristics of mode I crack of Lu-grey granite was experimentally studied by single-sided straight crack three-point bending beam（SC3PB）,and its fracture toughness was 0.9~1.4 MN/m1.5.Based on the digital image correlation（DIC）method,the evolution of the displacement field and strain fields of specimen before peak load were analyzed.According to the discontinuity of displacement field,the extended trajectory of process zone was given and the variation pattern of high strain region was obtained from the strain field.When the local horizontal displacement gradient changes drastically,the type I fracture of the Lu-grey granite enters the process zone.When the strain in the horizontal direction reaches 0.11%~0.20%,it is used as the threshold value of entering the process zone.Furthermore,the expansion rate of the tip of the process zone in the vertical direction and the length of the process zone are given a cubic polynomial increment relationship.