ポリプロピレンの疲労き裂伝ぱ挙動に及ぼす結晶化度と温度の影響 : 巨視的考察

概要

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In order to investigate macroscopically the effects of crystallinity and temperature on the fatigue crack growth behavior of polypropylene resins, the load controlled fatigue test was conducted and the macroscopic consideration of the fatigue crack growth behavior was made in this paper. The results obtained are as follows:(1) The fatigue strength of the notched specimen at a given temperature increased with an increase in crystallinity and mean size of spherulite, but it was influenced by the crystallinity more than the mean size of spherulite. The fatigue strength also increased with a decrease in temperature. The slope of S-N curves was gentle at temperatures near the glass transition point. (2) In the fatigue crack growth process, two kinds of damage zone occurred at the crack tip, and the size of the damage zone in the load direction decreased with a decrease in temperature. The mechanism of fatigue crack growth was made clear for the specimens with different crystallinities at room temperature. (3) The fatigue crack growth curves were divided into three types. The type I is a smooth curve at room temperature and the type II is a stepwise curve at temperatures below 20℃. It is the type III that the unstable fracture occurs suddenly when the stable crack grows a little and the crack growth curve is almost flat at lower temperatures.
社団法人日本材料学会の論文
1988-07-15