基于颗粒流的带中心孔巴西圆盘试样裂纹扩展分析

Analysis of crack propagation of holed-flattened Brazilian disc with particle flow code

为研究带中心孔巴西圆盘的劈裂过程,利用颗粒流法分析不同孔径的带中心孔巴西圆盘的裂纹扩展规律和机理。结果表明,不同孔径的巴西圆盘断裂模式有一定差异,主裂纹均从孔洞在加载方向的两端萌生并沿加载方向扩展。当中心孔径较小时,次生裂纹从加载点附近萌生并与主裂纹发生连通作用,圆盘试样破裂分成两半;当中心孔径较大时,次生裂纹从加载点的一侧萌生并向中心孔方向扩展,圆盘试样劈裂成4块。带中心孔巴西圆盘的劈裂过程可分为弹性变形阶段、主裂纹的萌生和稳定扩展阶段、主裂纹的扩展失稳阶段和次生裂纹扩展失稳阶段等4个阶段。从应力场角度来看,巴西圆盘的劈裂过程是拉应力集中区不断转移并产生新的微拉裂纹,大量微裂纹萌生、扩展和贯通形成宏观裂隙的过程。从能量角度来看,巴西圆盘的劈裂破坏过程是岩石从受荷初期应变能不断积累,到达峰值强度后应变能瞬时释放并伴随耗散能急剧增加的过程。

The particle flow codeis is used to analyze crack propagation rules and mechanisms of holed-flattenedBrazilian disc with different aperture. The results show that there is a certain difference in the fracturemode of Brazil disc specimen with different center hole diameter. Regardless of the size of the hole, the maincracksare initiated from both ends of the hole in the loading direction and extend along the loading direction. Ifthe center aperture is small, the secondary cracks will be initiated from the loading point and connected to themain cracks, which lead to the rupture of the disc specimen in half. If the center aperture is large, the secondarycracks will be initiated from the side of the loading point and extend to the center hole, which dividethe disc specimen into four parts. The spliting process of holed-flattened Brazilian disc can be divided into four stages ： elastic deformation, initiation and stable propagation of the main cracks, unstable failure of the maincracks, unstable failure of the secondary cracks. From the point of view of stress field, tensile stress concentrationarea continually transfers and forms new micro tensile cracks during the spliting process. The initiation,propagation and coal escence of many micro tensile cracks form the macroscopic fracture. From the point ofview of energy, the continuous strain energy accumulates in the initial loading. Then strain energy releasessharply and dissipative energy increases rapidly after peak strength.