Characteristics of Brittle Fracture Under Bi-axial Tensile Load (2nd Report)(Welding Mechanics, Strength & Design)
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In the previous report the brittle fracture initiation characteristics of plate subjected to bi-axial tensile load was investigated on the cruciform specimen of PMMA (polymethylmethacrylate) and SM41 (mild steel), each of which containes an inclined notch. The former specimens fractured in a perfectly brittle manner at room temperature. For the latter specimens, the test temperature was so selected that the fracture occures in a brittle manner with small scale yielding. In both cases, the fracture stress and the direction of initial crack propagation were well predicted by the criteria based on either maximum tangential stress, ^σθ, max, or maximum energy release rate ^Gθ, max. In this report the brittle fracture initiation characteristics with large scale yielding is investigated. A series of fracture tests is conducted on the cruciform specimens of SM41 under bi-axial tensile load, of which load ratios are 0/1, 1/2 and 1/1. Elastic plastic stress analysis is also carried out using the finite element method. The results obtained by the experiments and the finite element analysis lead to the following conclusions. (1) The direction of fracture initiation is nearly normal to the vector of crack opening displacement (COD) near the tip of notch obtained by the finite element analysis. (2) Brittle fracture stress under mixed mode conditions may be conservatively predicted by the critical COD for the opening mode fracture as the application of COD-concept.
- Transactions of JWRI
Transactions of JWRI 8(1), 121-130, 1979-06