내압이 작용하는 감육 배관의 파괴거동 평가

Abstract

Fracture behavior and pipe strength are very important to the integrity of energy plants, and ocean structures. The pipes of energy plants and ocean structures are subject to local wall thinning, resulting from severe erosion-corrosion damage. Therefore, evaluation of failure pressure and fracture behavior of pipes in energy plants, ocean structures must be needed for getting integrity of them. In this study, the pipe failure tests were performed on carbon steel pipe with various local wall thinning shapes, wall thinning length, wall thinning depth. The tests were conducted under internal pressure. The results of tests showed that failure mode of wall thinned pipe depended on magnitude of internal pressure and wall thinning length as well as wall thinning depth. The circumferential strain of wall thinned pipe was measured by using strain gage and compared with that estimated by using finite element analyses(FEA). FEA could estimate the precise elastic circumferential strain but could not estimate the precise plastic circumferential strain. When circumferential strain was over 0.2%, failure of wall thinned pipe began. And twice of pressure at 0.2% circumferential strain was needed to burst pipe with t/T=0.1, L=102 mm. When the pressure was reached at failure pressure, wall thinned area of STS370 pipe burst as a result of plastic behavior with large plastic deformation. Acoustic emission has been widely used in various fields because of its extreme sensitivity, dynamic detection ability and location of growing defects. In this study we also investigated Acoustic emission signal by burst test. The AE signals began to be detected when circumferential strain was over 0.2% at yield region, plastic deformation region, except elastic region and the frequency range of AE signals was 78 to 351 kHz at that time. The 78~195 kHz signals and 292~351 kHz signals concentrated yield region, plastic deformation region, respectively. The results of the dominant frequency range would be expected to be basic data that can inspect energy plant in real-time.