THE EFFECT OF STRESS GRADIENT AND STRESS BIAXIALITY ON THE BEHAVIOR OF MATERIALS.
Final rept. 15 Oct 60-15 Oct 61 on Refractory Inorganic Non-Metallic Materials,
SYRACUSE UNIV RESEARCH INST N Y
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Effects of stress gradient and stress biaxiality on the notch strength of brittle, semi-brittle and semi-ductile materials were investigated. Results obtained on a nearly ideally brittle titanium alloy are in agreement with the predictions of a fracture concept based on Neubers theory of notch stresses. Accordingly, the stress concentration factor is the dominant parameter. The magnitude of the stress gradient and stress biaxiality at the notch root has a secondary effect in that the notch strength of brittle materials is reduced with decreasing gradient and increasing biaxiality. The notch strength behavior of brittle ceramics has to be interpreted in terms of the inhomogeneity of these materials. Weibulls statistical theory of fracture was applied to this problem. Semi-brittle and semi-ductile materials exhibit a behavior similar in trend to that predicted for brittle materials with respect to stress concentration factor, stress gradient and stress biaxiality. However, for low stress concentration factor values, these effects are altered by phenomena due to plastic deformation at and near the notch root which significantly modify the stress and strain distribution and cause notch strengthening, the amount of which in itself appears related to the stress gradient and the stress biaxiality. Author