Abstract: As one of the perfect geometries in nature, sphere is common in daily and industrial life. The mechanical properties of sphere are of great significance to engineering safety and numerical simulation. Internal cracks or defects are inherent properties of materials and have an important influence on the mechanical properties of materials. However, the internal crack of the sphere is not considered in the current research due to the limit of technology. Thus, understanding of the propagation of internal cracks of brittle spheres is limited. In our study, internal cracks were created in glass sphere samples by 3D-ILC (3D-internal laser-engraved crack). Uniaxial compression tests were performed on samples with an internal crack at 60°. By comparing with results of intact sphere samples, the propagation of the internal crack, the load and the fractography were investigated. The distributions of KI, KII, KIII were calculated using M-integral. Results shows that: 1) the fracture patterns include wing cracks and primary crack; 2) the wing crack is composed of the smooth zone (mode I-II fracture) and the tear zone (mode I-II-III fracture); 3) the distributions of KI, KII, KIII around crack tips obtained by M-integral are consistent with the test results; 4) 3D-ILC can be successfully applied into the investigation of internal cracks of spheres and it provides experimental and theoretical basis for the study of 3D problem, internal cracks, and mode I-II-III fracture in fracture mechanics of brittle materials.

Key words: transparent rock-like materials, 3D internal crack, 3D-ILC, fracture mechanics, sphere