裂纹面动摩擦作用对脆性材料动力破坏的影响

EFFECT OF DYNAMIC FRICTION ON CRACK SURFACE ON DYNAMIC FAILURE OF BRITTLE MATERIALS

基于岩石类材料的I型裂纹模型,提出了一种考虑裂纹密度、裂纹相互作用以及裂纹面动摩擦作用的脆性材料动力模型。以正方形阵列分布的裂纹为例,定量分析了不同裂纹密度及不同摩擦行为对试件的裂纹扩展过程、试件受力和破坏的影响。数值计算结果表明:随着裂纹密度增大,裂纹间的相互作用增强,试件破坏时的加载应力降低,惯性效应引起试件轴向附加应力增大。裂纹面的滑动会降低裂纹面的动摩擦系数,促进裂纹发展,并降低试件的强度。相对于常数摩擦系数,考虑速度及状态依赖型摩擦模型对裂纹面的滑动过程更为合理。动强度因子对比结果显示出试件明显的应变率效应和尺寸效应。

Based on the model of Mode I cracks for rock-like material,a dynamic model for rock-like materials is proposed,which considers the crack concentration,density effect and dynamic friction of cracks.Taking the crack distributed in the square array as an example,the effects of different crack density and friction behavior on the crack propagation process,stress and failure of the specimen are quantitatively analyzed.The numerical results show that:with the increase of crack density,the interaction between cracks increases,the loading stress decreases,and the inertia effect causes the axial additional stress of the specimen to increase.The sliding of the crack surface will reduce the dynamic friction coefficient of the crack surface,promote the crack development,and reduce the strength of the specimen.Compared with the constant friction coefficient,considering the velocity and state-dependent friction model is more reasonable for the sliding process of the cracked surface.The comparison results of dynamic strength factors show that the specimen display an obvious strain rate effect and a dynamic size effect of rock mass strength.