繰り返し熱衝撃下円筒内表面環状き裂の停留深さ

抄録

In this paper we analyze the crack arrest depth for an inner-surface circumferential crack in a finite-length cylinder under cyclic thermal shock. The edges of the cylinder were rotation-restrained and the inside of the cylinder was cooled from uniform temperature distribution. The effects of structural parameters and the heat transfer conditions on the maximum transient stress intensity factor were investigated with the previously developed systematic evaluation methods. Then, assuming the Paris law and a tentative value of threshold stress intensity range ΔK_th, we evaluated the crack depth for crack arrest under cyclic thermal shock. Finally, we developed a map to find the crack arrest depth for a cylinder with mean radius to wall thickness ratio R_m/ W= 1 and a specific length H under various heat transfer conditions. From this map, we can predict that when the heat transfer coefficient and/or initial wall-coolant temperature differences are large enough, the non-dimensional crack arrest depth saturates at a specific value and is no longer affected by material properties of the cylinder.