Characteristics of Brittle Fracture Under Bi-axial Tensile Load
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In this paper, brittle fracture initiation characteristics of plate subjected to bi-axial tension is investigated on cruciform specimens of PMMA (polymenthylmethacrylate) and SM41 (mild steel), each of which contains an inclined crack. The brittle fracture tests are conducted on the cruciform specimens at the load ratio of 1/1, 1/2 and 0/1, and also on straight side specimens under uni-axial tension. The direction of initial crack propagation and the fracture stress are theoretically estimated by applying the following criteria: (1) the maximum tangential stress, σ_θ, max, (2) the minimum strain energy density factor, S_<min>, and (3) the maximum decreasing rate of total potential energy, G_θ, max. In the case of PMMA, the test results can be explained well in terms of σ_θ, max, in which a cirtain ambiguity remains. They can be also explained well in terms of S_<min>, except the direction of initial crack propagation in the case of load ratio, 1/2. However, the physical meaning of S_<min> is not understandable. The test results can be explained most clearly by applying <G_θ>_<max> criterion, in which the value of G_θ is calculated by the finite element method. In the case of SM41, the direction of initial crack propagation shows a similar tendency as in the case of PMMA. However, the fracture stresses are higher than the predicted ones applying the linear fracture mechanics, when the mode Il deformation is predominant. It may be concluded that the critical value of G_θ depends on the value of K_<II>, that is, the critical value increases as the value of K_<II> increases.
- Transactions of JWRI
Transactions of JWRI 5(2), 169-177, 1976-12