• 제목/요약/키워드: SCC mode

검색결과 29건 처리시간 0.024초

시추코어를 이용한 암석의 mode II 파괴인성 시험법 개발과 적용 (Development and Application of Mode II Fracture Toughness Test Method Using Rock Core Specimen)

  • 정용복;박의섭;김현우
    • 터널과지하공간
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    • 제26권5호
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    • pp.396-408
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    • 2016
  • 암석파괴역학은 토목공학과 암반공학의 다양한 분야에서 널리 적용되는 학문이다. 그러나 대부분의 암반 공학 문제에서 mode II 거동이 우세함에도 불구하고 관련 연구는 mode I 거동에 대한 것이 대부분이다. 현재 mode I의 경우 4개, mode II 파괴인성의 경우 단 한 개의 ISRM 표준시험법이 있다. 본 연구에서 제안하는 새로운 시험법은 문헌조사를 통해서 필요조건으로 구속압 가능 여부, 노치성형의 용이성, 기존 시험장비의 활용, 단순한 시험절차를 정하고 이에 부합하도록 개발하였으며 SCC(Short Core in Compression)로 이름을 정하였다. Mode II 파괴인성 계산에 필요한 응력확대계수 계산식을 3차원 수치해석을 통해 선하중과 분포하중 조건에 대해서 구하였고 노치성형을 위한 지그도 제작하였다. 개발된 시험법을 MTS 시스템을 사용하여 화강암에 적용하였으며 가압속도는 0.002 mm/s로 하였다. 시험 결과 $2.33MPa{\sqrt{m}}$의 mode II 파괴인성을 얻었다. 동일한 화강암 블록에서 확보한 시험편에 대하여 간접인장시험으로 구한 mode I 파괴인성은 $1.12MPa{\sqrt{m}}$였다. 따라서 $K_{IIC}/K_{IC}=2.08$로 mode II 파괴인성이 mode I보다 크게 나타났다. 또한 비교적 매끄러운 파괴면과 암분의 생성을 통하여 SCC 시험법이 mode II 거동을 잘 표현함을 확인하였다. 따라서 제안된 SCC 시험법은 암석의 mode II 파괴인성을 결정하는 데 사용할 수 있을 것으로 판단된다.

오스테나이트 304 스테인레스 강의 응력부식균열에 미치는 냉간가공의 영향 (Effect of Cold Work on the Stress Corrosion Cracking in Austenitic 304 Stainless Steel)

  • 강계명;최종운
    • 한국안전학회지
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    • 제12권1호
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    • pp.19-28
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    • 1997
  • This study was made of the effect of cold working on the stress corrosion cracking(SCC) of austenitlc 304 stainless steel in boiling 42% $MgCl_2$ solution. For this experiment, specimens cold-worked of 0%, 10%, 20%, 30%, 40% were fabricated respectively, and then experiments of mechanical properties and stress corrosion cracking(SCC) of these specimens were carried out. The results of these experiments indicate that the maximum resistance to SCC showed at 20% of cold working degree and that the SCC susceptibility depended on the volume fraction of deformation-induced martensite by cold working and the work hardening of matrix. On the other hand, the fracture mode was changed. This phenomenon was considered that deformation-induced martensite was grown from transgranular fracture mode to intergranular fracture mode and caused by increased of dislocation density along the slip planes.

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원전 1차 계통수 모사환경에서 Type 304 스테인리스강의 응력부식균열개시 민감도 (Susceptibility of Stress Corrosion Crack Initiation of Type 304 SS in Simulated Primary Water Environment of PWR)

  • 조성환;김성우;이종연
    • 한국압력기기공학회 논문집
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    • 제20권1호
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    • pp.25-31
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    • 2024
  • The core shroud of rector vessel internals (RVI) of OPR1000 and ARP1400 is made of Type 304 stainless steel (SS) by bending and welding process that may induce high deformation and residual stress in manufacturing. This work aims to evaluate the susceptibility of stress corrosion crack (SCC) initiation of bent parts of RVI in high temperature primary water environment. For SCC initiation test, tensile specimens were fabricated from the 90 degree bent plate of Type 304 SS (DT specimen), that is an archived part of a Korean APR1400. After the SCC initiation test, the specimen surface was thoroughly examined by optical and scanning electron microscopy, and compared to the specimen fabricated from the as-received plate of Type 304 SS (AR specimen). The surface observation revealed that SCC initiated on the AR specimen surface in typical intergranular (IG) mode, while SCC on the DT specimen occurred in transgrannular mode as well as IG mode. It was also found that the size and number of SCC on the DT specimen were larger than that on the AR specimen. This was attributable to a strain-hardening during the bending process. To compare the susceptibility of SCC initiation, total crack density (TCD) was calculated from the total crack length divided by the measured area of AR and DT specimens. TCD of DT specimen was 4.6 times higher than AR specimen in average, indicating that higher possibility of degradation of bent parts of RVI for a long-term operation.

고온의 염기성 수용액에서 Ni기 합금의 응력부식파괴

  • 김홍표;황성식;국일현;김정수
    • 한국원자력학회:학술대회논문집
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    • 한국원자력학회 1998년도 춘계학술발표회논문집(2)
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    • pp.84-89
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    • 1998
  • Alloy 600 및 alloy 690과 Ni-8Cr-lOFe 합금 등의 응력부식(stress corrosion cracking, SCC) 거동을 고온의 염기성 분위기에서 C-ring 시편을 사용하여 연구하였다. Alloy 600과 alloy 690을 여러 조건에서 열처리하여 etching한 후 탄화물의 분포와 입계 주변의 Cr고갈 정도 등의 미세조직을 광학현미경과 주사 전자현미경(SEM)으로 관찰하였다. 이들 재료에 대한 SCC 시험을 315$^{\circ}C$의 40% NaOH 수용액에서 일정한 부하전위(부식전위 + 200㎷)를 가하면서 수행하였으며, 동일 조건에서의 분극거동도 측정하였다. Alloy 600 MA(mill anneal) 및 TT(thermal treatment)의 SCC 저항성은 alloy 690 TT와 Ni-8Cr-10Fe SA(solution anneal)보다 낮았다. Alloy 600 TT 재료는 alloy 600 MA 및 SA 재료에 비해 SCC 저항성이 더 컸다. 고용 탄소농도는 alloy 600의 SCC 저항성에 큰 영향을 주지 못했다. 대부분의 Alloy 600은 균열전파 입계균열을 보였으나, 일부에서는 입계 및 입내 혼합양상(mixed mode cracking)을 보였다. 염기성 분위기에서 Ni기 합금의 SCC 거동을 미세조직, 분극거동의 관점에서 고찰하였다.

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Study on Corrosion Characteristics and Stress Corrosion Cracking of the Weldment for HT-60 Steel in Synthetic Seawater

  • Na, Eui-Gyun;Koh, Seung-Ki;Oh, Seok-Hyung
    • Journal of Mechanical Science and Technology
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    • 제14권2호
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    • pp.152-158
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    • 2000
  • The contents of this paper include the evaluation of corrosion characteristics and the behaviour of stress corrosion cracking (SCC) for the weldment and post weld heat treatment (PWHT) specimen and parent of HT -60 steel using a slow strain rate test (SSRT) in synthetic seawater. Corrosion characteristics were obtained from the polarization curves by potentiostat, and SCC phenomena were evaluated through the parameters such as reduction of area and time to failure by comparing the experimental results in corrosive environment with those obtained in air. Corrosion rate of the weldment was the fastest, followed by parent and PWHT specimen. SCC phenomena between the weldment of HT-60 steel and synthetic seawater were shown. Besides, SCC was dependent upon the pulling speed greatly. Maximum severity of SCC was obtained at a speed of $10^{-6}mm/min$, whereas SCC could not be seen almost at $10^{-4}mm/min$. The resistance to SCC for PWHT specimen was improved considerably compared that of the weldment at $10^{-6}mm/min$. In case of SCC failure, it was verified from SEM examination that brittle mode and lots of pits could be seen at the fractured region near the surface of the specimen.

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Al-Cu-Mn 주조합금의 SCC 특성에 미치는 Sn 첨가의 영향 (Effect of Sn Addition on the SCC Properties of Al-Cu-Mn Cast Alloy)

  • 김광년;김경현;김인배
    • 한국재료학회지
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    • 제12권6호
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    • pp.436-441
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    • 2002
  • Effect of Sn addition on the stress corrosion cracking(SCC) resistance of the Al-Cu-Mn cast alley was investigated by C-ring teat and electrical conductivity measurement, The electrical conductivity and SCC resistance increased by Sn addition. The alley containing 0,10%Sn showed maximum electrical conductivity and the best SCC resistance. At the same composition, the electrical conductivity and SCC resistance increased from peak aged condition to ever aged condition. The PFZ and coarse precipitates along the grain boundary were observed from TEM micrographs. The fracture mode of the alloy was confirmed as intergranular type and showed brittle fracture surface. The SCC mechanism of the alloy was concluded as the anodic dissolution model, The maximum hardness was increased from 130Hv in the Sn-free alloy to 156Hv in the 0.10%Sn added alloy.

Atmospheric Corrosion of 7B04 Aluminum Alloy in Marine Environments

  • Zhang, Xiaoyun;Liu, Ming;Lu, Feng;Liu, Minghui;Sun, Zhihua;Tang, Zhihui
    • Corrosion Science and Technology
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    • 제17권1호
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    • pp.6-11
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    • 2018
  • Outdoor exposure tests using of 7B04 aluminium alloy samples including plate, tensile and various SCC samples were carried out in Tuandao station, Shandong province (East of China) and Wanning station, Hainan province (South of China). Corrosion characteristics including weight loss, microstructure, tensile strength and SCC susceptibility were investigated. The corrosion rates in Tuandao and Wanning showed high to low and the corrosion rates changed to the following equation of $w=at^b$ (b<1). The corrosion of 7B04 aluminium alloy in Wanning was more serious than that in Tuandao. Pitting appeared at early stage of expose test, and it can be changed to general corrosion with test time extension. The 7B04 aluminium alloy of which specimen shapes are forging and thick plate also showed SCC (Stress corrosion cracking) in the marine atmosphere. The higher SCC sensitivity was observed in Wanning station than in Tuandao station. The 7B04 aluminium alloy with a high stress level was more sensitive to SCC. Intergranular and transgranular or a mixed mode of cracking can be observed in different marine exposure.

New test method for real-time measurement of SCC initiation of thin disk specimen in high-temperature primary water environment

  • Geon Woo Jeon;Sung Woo Kim;Dong Jin Kim;Chang Yeol Jeong
    • Nuclear Engineering and Technology
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    • 제54권12호
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    • pp.4481-4490
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    • 2022
  • In this study, a new rupture disk corrosion test (RDCT) method was developed for real-time detection of stress corrosion cracking (SCC) initiation of Alloy 600 in a primary water environment of pressurized water reactors. In the RDCT method, one side of a disk specimen was exposed to a simulated primary water at high temperature and pressure while the other side was maintained at ambient pressure, inducing a dome-shaped deformation and tensile stress on the specimen. When SCC occurs in the primary water environment, it leads to the specimen rupture or water leakage through the specimen, which can be detected in real-time using a pressure gauge. The tensile stress applied to the disk specimen was calculated using a finite element analysis. The tensile stress was calculated to increase as the specimen thickness decreased. The SCC initiation time of the specimen was evaluated by the RDCT method, from which result it was found that the crack initiation time decreased with the decrease of specimen thickness owing to the increase of applied stress. After the SCC initiation test, many cracks were observed on the specimen surface in an intergranular fracture mode, which is a typical characteristic of SCC in the primary water environment.

Stress Corrosion Cracking Behavior of Cold Worked 316L Stainless Steel in Chloride Environment

  • Pak, Sung Joon;Ju, Heongkyu
    • 한국주조공학회지
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    • 제40권5호
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    • pp.129-133
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    • 2020
  • The outcomes of solution annealing and stress corrosion cracking in cold-worked 316L austenitic stainless steel have been studied using x-ray diffraction (XRD) and the slow strain rate test (SSRT) technique. The good compatibility with a high-temperature water environment allows 316L austenitic stainless steel to be widely adopted as an internal structural material in light water reactors. However, stress corrosion cracking (SCC) has recently been highlighted in the stainless steels used in commercial pressurized water reactor (PWR) plants. In this paper, SCC and inter granular cracking (IGC) are discussed on the basis of solution annealing in a chloride environment. It was found that the martensitic contents of cold-worked 316L stainless steel decreased as the solution annealing time was increased at a high temperature. Moreover, mode of SCC was closely related to use of a chloride environment. The results here provide evidence of the vital role of a chloride environment during the SCC of cold-worked 316L.

Shear Behavior and Performance of Deep Beams Made with Self-Compacting Concrete

  • Choi, Y.W.;Lee, H.K.;Chu, S.B.;Cheong, S.H.;Jung, W.Y.
    • International Journal of Concrete Structures and Materials
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    • 제6권2호
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    • pp.65-78
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    • 2012
  • An experimental study was carried out to evaluate fresh properties of a moderately high-strength (high-flowing) self-compacting concrete (SCC) and to investigate shear behavior and performance of deep beams made with SCC. Fresh and hardened properties of normal concrete (NC) and SCC were evaluated. The workability and compacting ability were observed based on casting time and number of surface cavities, respectively. Four-point loading tests on four deep beams (two made with SCC and two with NC) were then conducted to investigate their shear behavior and performance. Shear behavior and performance of beams having two different web reinforcements in shear were systematically investigated in terms of crack pattern, failure mode, and load-deflection response. It was found from the tests that the SCC specimen having a normal shear reinforcement condition exhibited a slightly higher load carrying capacity than the corresponding NC specimen, while the SCC specimen having congested shear reinforcement condition showed a similar load carrying capacity to the corresponding NC specimen. In addition, a comparative study between the present experimental results and theoretical results in accordance with ACI 318 (Building Code Requirements for Reinforced Concrete (ACI 318-89) and Commentary-ACI 318R-89, 1999), Hsu-Mau's explicit method (Hsu, Cem Concr Compos 20:419-435, 1998; Mau and Hsu, Struct J Am Concr Inst 86:516-523, 1989) and strut-and-tie model suggested by Uribe and Alcocer (2002) based on ACI 318 Appendix A (2008) was carried out to assess the applicability of the aforementioned methods to predict the shear strength of SCC specimens.