多軸応力下でのグラスセラミックスの疲労特性 : 円板圧裂引張負荷による検討

概要

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Glass ceramic specimens having a controlled surface flaw introduced by Knoop indentation were tested under dynamic,static and cyclic loads by four-point bending of plates (unaxial tension) and by diametral -compression of disks (tension-compression). All specimens showed suscepibility to dynamic, static and cyclic fatigue failuer. Equivalent time-to failure obtained from the dynamic and cyclic fatigue data, using the assumption that there is no enhanced effect of cycle on the rate of subcritical crack growth, was plotted in the diagram between applied stress and tim-to-failure. The crack propagation parameter, n, was estimated from the relation of time-to-railure and the maximum applied stress in the static and cyclic fatigue tests and the stressing rate dependence of the fracture strength in the dynamic fatigue tests. Consequently, it was found that the n value for diametralcompression loading becamesomewhat higher than that for four-point bending. The higher n value in diametral-dompression could be mainly explained by the fact that a crack in a tension-compression stress state has a less freedom of motion than that in a uniaxial tension stress state, and such a strong orientation dependence for crack growth in a tension-compression stress state restrains the crack to grow around obstacles or grains.
社団法人日本材料学会の論文
1993-05-15