不同角度单裂纹缺陷试样的裂纹扩展与破坏行为

CRACK GROWTH MECHANISM AND FAILURE BEHAVIOR OF SPECIMEN CONTAINING SINGLE FLAW WITH DIFFERENT ANGLES

在诸如岩石、混凝土、陶瓷和玻璃等脆性介质中,常分布大量的裂纹缺陷。这些缺陷在载荷作用下造成裂纹的孕育、萌生、繁衍、扩展和贯通,导致介质的强度和刚度降低。通过自制的试验系统,研究了不同角度的预置单裂纹缺陷的花岗岩试样的裂纹扩展与破坏过程,并用数值模拟进行了验证。试验和数值结果显示:单轴载荷作用下,裂纹扩展和最后的破坏行为受预置单裂纹缺陷的角度影响。当角度较小时,裂纹萌生比较容易,在整个受压过程中均匀扩展,试样一般以混合模式破坏;当角度较大时,裂纹不易萌生,但在接近峰值强度时,扩展较快,并直接导致最后的剪切或劈裂破坏;当预置裂纹缺陷的角度与试样的破坏角接近时,试样最容易发生脆性破坏,并产生很大的应力降。

Rock, concrete, ceramics and glass, as discontinuous, inhomogeneous, anisotropic, and notelastic brittle medium, are typically made up of defected material containing flaws and pores. Under differential compressive stress, the crack initiation, propagation, coalescence and interaction may cause the strength and stiffness degradation of such medium. Original study of specimen containing flaw defect is mainly focused on single flaw model. By employing a test system and numerical tool, this paper investigated crack growth mechanism and failure behavior of specimen containing single flaw with different angles. The experimental and numerical results show that crack growth and final failure behavior is strongly affected by the flaw angle under uniaxial compression. When the flaw angle is small, crack initiation is easy： crack growth velocity is stability, and specimen failure with mixed mode. When the flaw angle is large, the crack initializes and propagation is compressed. However, crack growth is rapid while loading is close to the peak strength, then specimen will be broken with shear or splitting mode. when the value of flaw angle is close to that of failure angle, the specimen is easy to emerge brittle failure with prominent stress decrease.