Micro-Surface-Cracks Behavior of 304 Stainless Steel Under Creep-Fatigue Interaction at Elevated Temperature

J. Ocean Eng. Technol. 1988;2(2):104-111.

고온하 304 스테인리스강의 크리프-피로상호작용하의 미소표면균열에 관한 파괴거동

서창민,이상돈,조일현

경북대학교 기계공학과,쌍용중공업,포항제철제철소

Keywords: Creep, Micro-Surface-Crack, High Temperature Fatigue, Fracture Mechanics, Smooth Specimen, Weibull Distribution of Cumulative Probability

핵심용어: 크리프, 미소표면균열, 고온피로, 파괴역학, 평활재, 와이블 누적확률

Abstract

This paper deals with the micro-surface-cracks behavior on the unnotched smooth specimens of Type 304 stainless steel at $593^{circ}C$ in air under creep and creep-fatigue conditions that have 10 mim and 1 min load holding times respectively. The behaviors of the micro-surface-cracks have been visualized by means of surface replica method and optical micro-photography. The quantitative characteristics of initiation, growth and coalescence of micro-surface-cracks have been investigated by observing and measuring the crack growth behaviors. some of the important results are as follows: Main crack initiates at grain boundary in the early stage(10 to 20%)of its life time and grows through coalescence and finally leads to fracture. The distribution of micro-surface-crack length, 2a, can be plotted against the composite Weibull distribution. The growth rate of the main crack can be plotted against the stress intensity factor, crack tip opering displacement and J integral.