As one step in the characterization of its mechanical, metallurgical, and physical properties, the temperature dependence of the fracture toughness of a high-yield-strength grade of hot-pressed beryllium block was determined over the range between room temperature and 300℃. Fatigue cracks were generated in 8. 92-mm-thick double-cantilever beam spec¬imens by a reversed-loading method. Room-temperature fracture-toughness data from tests on specimens with Elox-machined notches and fatigue precracks were compared. Electron fractographs of fatigue and fast-fracture regions were obtained. Load-displacement records generated from tests on spec¬imens with natural cracks were nonlinear, whereas tests on specimens with machined cracks gave the expected linear records. Evidence points to a crack-closure phenomenon rather than plasticity as the source of the non-linearity.
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