基于3D-ILC含不同角度内裂纹圆盘断裂特性研究

Fracture characteristics of Brazilian disc with fully internal cracks based on 3D-ILC

巴西圆盘试验是力学领域的一个经典试验,含裂纹的圆盘试验多集中于二维或表面裂纹,但含内裂纹的Ⅰ-Ⅱ-Ⅲ型断裂研究一直较为落后.基于3D-ILC技术,在对巴西圆盘试样表面无任何影响的情况下,凭空生成任意参数的内裂纹,开展含不同角度内裂纹的及完整巴西圆盘试样试验,对裂纹扩展过程、应力双折射规律、裂纹起裂及破坏荷载进行分析,并与已有文献进行对比,开展三维内裂纹Ⅰ-Ⅱ-Ⅲ型断裂数值模拟,分析KⅠ,KⅡ,KⅢ分布规律及实现裂纹扩展全过程模拟,规律与试验相符.结果 表明:①3D-ILC在断裂力学试验中的优势得到证明,为断裂力学中的内裂纹及Ⅰ-Ⅱ-Ⅲ型断裂问题的研究奠定了基础.②与完整试样匀称连续的应力云纹分布相比,含内裂纹试样应力云纹集中于内裂纹尖端,呈花瓣状,色差对比显著.③30°内裂纹被括弧状破坏面切断;60°内裂纹上下尖端出现Ⅰ-Ⅱ型翼裂纹扩展,侧面出现Ⅲ型裂纹叠加;90°内裂纹试样,沿内裂纹面扩展破坏,为纯Ⅰ型破坏.④与完整试样破坏荷载相比,含30°,60°,90°内裂纹试样破坏荷载分别下降10.7%,60.6%,89.2%;30°,60°,90°内裂纹起裂与破坏荷载比分别为100%,11.7%,15.6%.⑤数值模拟与物理试验特征一致.结论 与成果对断裂力学领域的三维内裂纹、Ⅰ-Ⅱ-Ⅲ型断裂问题的研究提供了试验与理论基础.

The fully internal crack is created in the Brazilian disc based on the 3D-ILC method, without any effect on the surface. The uniaxial compression experiments are performed on the Brazilian discs with internal cracks at different angles. The experimental results are compared with the existing literatures. The propagation of the fully internal crack, the distribution of the stress-induced birefringence, the initiation of the crack and the failure stress and the fracture surface characteristics are investigated. Then the numerical simulations are carried out. The results show that:(1) The validity of the 3D-ILC is proved in the fracture mechanics researches.(2) The stress birefringence of the cracked specimen is discontinuous at the internal crack.(3) Compared to the intact specimens, the internal cracks greatly reduce the strength of the Brazilian disc, with decrease of 10.7%, 60.6% and 89.2% for the specimens with 30°, 60° and 90°. The stresses of crack initiation are 100%, 11.7% and 15.6% of the failure stress for the specimens with 30°, 60° and 90°.(4) The internal crack is penetrated by the primary crack for the Brazilian disc with crack of 30°. The mode Ⅰ-Ⅱ 3D wing cracks occur at the crack tip, while the mode Ⅲ cracks occur at the sides of discs with internal crack of 60°. The primary crack is mode Ⅰ crack for the disc with internal crack of 90°.(5) Numerical simulations are carried out on the Brazilian discs. The results may provide experimental support for the corresponding theoretical researches.