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A Study on Fatigue Crack Growth Characterization Of Surface Crack In Pressure Vessel Materials

압력용기 소재에서의 표면균열의 피로균열 성장특성에 관한 연구

  • 허용학 (한국표준연구소, 재료응용연구실) ;
  • 이주진 (한국표준연구소 재료응용연구실) ;
  • 한지원 (한국표준연구소 재료응용연구실) ;
  • 김종집 (한국표준연구소 재료응용연구실) ;
  • 문한규 (한국표준연구소 재료응용연구실)
  • Published : 1990.04.01

Abstract

Cracks found in pressure vessels have been reported to be mostly semi-elliptic surface cracks. The fatigue crack growth behaviour of the surface cracks on pressure vessel materials, SPV 50Q and API 5A-K55, was studied with the consideration of the crack opening character. To determine the crack opening loads for the surface cracks, the displacement/strain were measured at three positions; the center and the side of the surface crack, the back face of the specimen using CMOD gauge and strain gauges. The experimental results showed that the crack opening load levels measured at the side of the surface crack were generally a little higher than those measured at the back face. As for the crack growth rates at the different parts of the surface crack, the experiments also showed that, if .DELTA.K$_{eff}$ is used, the exponent n of the Paris' law obtained were the same for the rear and the side parts of the surface cracks.