Brittle failure criteria for components containing U-notches under Mode I loading

• Published in: Engineering fracture mechanics Vol. 200; pp. 86 - 103
• Main Authors: Chen, Dai-Heng, Ushijima, Kuniharu, Cantwell, Wesley J.
• Format: Journal Article
• Language: English
• Published: New York Elsevier Ltd 01.09.2018; Elsevier BV
• Subjects: Brittle material; Brittle materials; Brittleness; Characteristic length; Crack initiation; Criteria; Fracture toughness; Notches; Tensile strength; Tensile stress; U-notch; Brittle material; U-notch; Fracture toughness; Characteristic length
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2018.07.017

•The stress and energy conditions for brittle fracture do not need to be simultaneously fulfilled.•The failure load can be estimated from the larger value obtained from these conditions.•When KIC/σc is relatively small, the parameter lcm has a small influence on the modified fracture criterion.•For larger values of KIC/σc, σfe by the energy condition is always greater than σfs by the stress condition. In this study, a modified fracture criterion which satisfies the necessary stress and energy conditions is proposed for brittle materials. The criterion is based on the assumption that fracture is generated by the initiation of a crack with a finite length lcm. In the proposed criterion, it is assumed that the crack length lcm is an intrinsic material parameter, with a value between 0.8d0m⩽lcm⩽d0m(=2(KIC/σC)2/π). Here,d0m is the characteristic length used in the mean stress criterion, and KIC and σC are the fracture toughness and the tensile strength for the considered material, respectively. The stress and energy conditions for estimating the brittle fracture behaviour can be fulfilled progressively not simultaneously. However, both conditions must ultimately be fulfilled. Following tests on brittle materials, it has been shown that the predicted values of ultimate stress, based on the necessary stress and energy conditions, agree well with the experimental data.