Non-tip failure of smooth fissure in 3D printed specimens

• Published in: Engineering fracture mechanics Vol. 234; p. 107112
• Main Authors: Dong, Q.Q., Ma, G.W., Wang, W.Q., Duan, Q.S.
• Format: Journal Article
• Language: English
• Published: New York Elsevier Ltd 01.07.2020; Elsevier BV
• Subjects: 3D-printed specimen; Amplitudes; Cracking pattern; Cracks; Failure; Failure behaviour; Fracture mechanics; Inclination angle; Non-tip cracking; Photosensitivity; S-shape fissure; Segments; Three dimensional printing; Uniaxial compression; Uniaxial compression; Failure behaviour; Cracking pattern; S-shape fissure; Non-tip cracking; 3D-printed specimen
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2020.107112

•A simplified theoretical model is proposed to predict tip cracking and non-tip cracking by decoupling the S-shape fissure into three cracking models.•The specimens prepared by 3D-printed transparent resin material are employed to approximate the counterparts of rock-like materials for their similarities in fracture pattern.•Minimal research found that non-tip-cracking occurs in S-shape fissure by tested on a lab. The cracking behavior of S-shape fissures is different from that of straight fissures with respect to the occurrence of non-tip-cracking. Non-tip cracking for kinked fissures has been investigated in our previous study. This paper reveals that non-tip cracking also occurs for smooth fissures without kinks. 3D printed photosensitive resin specimens with a smooth S-shape fissure are tested under uniaxial compression. The influence of geometry and orientation of the S-shape fissure on the specimen deformation and strength behaviour, especially the non-tip-cracking failure is investigated. Results show that two cracking patterns, tip-cracking and non-tip cracking, occurs in a similar trend with that observed for kinked fissures. The non-tip cracking is sensitive to the inclination angle β and the ratio between the amplitude and ratio of the amplitude to the half length of the S-shape fissure, i.e., the effective curvature A/a, as it only occurs when β equals to 30°, 45°, 60° and the A/a is equal to or greater than 2/7.5. A simplified piecewise linear crack model is proposed to predict the occurrence of the non-tip cracking failure. The S-shape fissure is approximated by three straight segments and the three failure models A, B and C corresponding to their equivalent straight segments are identified based on the maximum circumferential stress criterion. The cracking pattern of the S-shape fissure is governed by model A and C failure and the predicted cracking patterns match well with the respective experimental ones. The results from the present research complement the traditional fracture mechanics by extending the understanding about non-tip cracking failure.