発電水車用ステンレス鋳鋼SCS1の疲労強度に及ぼす鋳造欠陥の影響,および欠陥寸法に基づく疲労寿命評価

概要

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In order to clarify the fatigue properties and the fracture mechanism of stainless cast steel SCS1 used as the turbine runner of hydraulic power generation for 40 years over, two types fatigue tests were carried out with a bending machine and a tension-compression machine. The results are summarized as follows: The S-N curve of aged SCS1 used in this study has wide variation and the fatigue strength by using a tension-compression machine was lower than that by using a bending machine. In order to examine the reason for that, fracture surfaces were observed by SEM. Accordingly, fatigue crack initiates at two types origin; slip and casting defects. The fatigue strength whose fracture origin was casting defects was significantly lower than that whose fracture origin was slip. So, it is clear that casting defects strongly affect the fatigue properties of aged SCS1. Furthermore, according to the estimation of fatigue life, it is clear that it is possible to evaluate the fatigue life of aged SCS1 used in this study by using the casting defect size (area)^<1/2> and the stress intensity factor K_<max> calculated by defect size.
社団法人日本機械学会の論文
2009-11-25