含缺陷PMMA介质的定向断裂控制爆破试验研究

以PMMA为试验材料,采用新型数字激光动态焦散线方法试验系统,从试验角度将裂纹缺陷和空孔缺陷纳入同一研究体系,进一步研究缺陷对定向断裂控制爆破裂纹扩展的影响。结果表明,缺陷形态对爆生主裂纹扩展长度的影响并不明显。爆生主裂纹的扩展分为2个阶段,Ⅰ阶段(0~120μs):爆生主裂纹的扩展速度和尖端动态应力强度因子均迅速减小;Ⅱ阶段(120μs~止裂):从缺陷处反射的应力波对裂纹尖端的作用效应逐渐明显,加强了裂纹尖端的能量积聚和应力集中,使得速度和动态应力强度因子均有较大程度的跃升;随着试件缺陷两侧曲率的增加,Ⅱ阶段的爆生主裂纹速度峰值和动态应力强度因子峰值均逐渐减小。

Experimental study on controlled directional fracture blasting#br# on PMMA mediums with flaws

The crack flaws and empty hole flaws were set in a single experiment using the experimental material of PMMA and the new system of digital laser dynamic caustics so that the effects of flaws on the crack propagation in the controlled directional fracture blasting were studied. The results show that the forms of flaws have little effect on the length of blasting induced main cracks. The propagation of main cracks have two stages. In stage I(0–120 μs)，the propagation velocity and stress intensity factor at crack tip decrease rapidly. In stage II(120 μs–crack arrest)，the effects on crack tips caused by stress wave reflected from flaws are more significant，the energy accumulation and stress concentration of crack tips are enhanced，and the velocity and dynamic stress intensity factor increase to a great extent. The peak velocity and peak dynamic stress intensity factor of blasting induced main crack decrease gradually with the curvature increasing of flaw sides during the stage II.