2017-T4 アルミ合金のストライエーション形状に及ぼす応力比の影響の定量解析と実働荷重推定の可能性

概要

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A prediction method of service loading from striations on fracture surface is proposed. Although it is well known that striation spacing corresponds to the crack growth rate da/dN,it is not possible to determine P_<max> and P_<min> under service loading only from s. This is because the value of s is influenced not only by ΔK but also by the stress ratio R (=P_<min>/P_<max>). The new idea in this study for determination of P_<max> and P_<min> is based on the anticipation that the information on R must be included in the relative height of striation H to s. The results of fatigue tests on 2017-T4 Al Alloy CT specimens showed a definite correlation between H/s and R. The difficulty of the measurement of H was overcome by sectioning the specimens at an inclined angle and by measuring small distance using SEM. Striations under R=-1 were compressed and flat, and H/s was small. With increasing R,H/s became large. Therefore, the standard laboratory test results on the relationship between s and ΔK, and also that between H/s and R enables us to predict service loading from the fatigue fracture surfaces.
1990-08-15