http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
압흔 주위 변형 양상 분석을 통한 구조용 강의 Luders strain 평가
최열,최종교,주웅용,권동일,안정훈 대한금속재료학회(대한금속학회) 2001 대한금속·재료학회지 Vol.39 No.1
The continuous indentation test was used to evaluate Lu¨ders strain of various steels such as ultra-fine grained steels and AISI 1020 steels. Inhomogeneous pile-up deformation in the indentation test could be related to Lu¨ders strain in tensile test. The pile-up deformation could be characterized as a localized flow phenomena. We analyzed the pile-up area as the parameter of Lu¨ders strain, and described the pile-up amount more quantitatively by considering the relation between plastic-zone size and pile-up radius. Finally, we derived the master curve for some steels, which included the ratio of elastic modulus to hardness as plastic-zone size. For various steels in this study, the values of Lu¨ders strain obtained from the master curve are consistent with those measured from the tensile test.
전위차법 (電位差法) 에 의한 35wt% MgCl2 수용액중에서의 304 계 스테인레스강의 응력부식균열의 생성 및 전파거동에 관한 연구
변수일,최종교,이우봉 대한금속재료학회(대한금속학회) 1988 대한금속·재료학회지 Vol.26 No.11
The behaviour of stress corrosion(SC) crack initiation and propagation of Type 304 stainless steel in 35 wt% MgCl₂ has been studied as a function of temperature and applied stress at the applied electrochemical potential of-106mV_(SHE) by using electrical potential method. In the present study. the electrical potential method allows to differentiate the incubation period from the propagation period for SC crack. The optical microscopy revealed that the pit is a primary source of SC crack initiation under the applied stress lower than yield strength. SC crack initiation stage is composed of three steps, 1) pit initiation, 2) pit growth to critical size, and 3) crack propagation in the lateral and the through-thickness directions. The portion if anodic dissolution trenches to pits as sites of SC crack initiation increased with applied stress higher than yield strength. The activation energy of the electrochemical reaction contribution to the SC crack initiation and the energy of the stress contribution to the SC crack initiation under 212MPa are evaluated to be 30.5 kJ/㏖ and 14.0 kJ/㏖ respectively. The fractography of SC crack propagation showed the transition of fracture mode from fully transgranular mode to the mixed zone with intergranular mode in the interior of the specimen. The intergranular portion is nearly independent of temperature, however it increases with the applied stress.
변수일,최종교,김홍표 대한금속재료학회(대한금속학회) 1986 대한금속·재료학회지 Vol.24 No.1
The effects of nonmetallic infusions and microstructures on the sulfide stress-corrosion cracking (SSCC) of welded line-pipe steels have been investigated by using electrical potential method. SSCC tests were conducted in H₂S-saturated aqueous solution containing 5 wt.% NaCl and 0.5 wt.% CH₃ COOH at temperature of 35±2℃ by using smooth U-bend specimens. Sulfide stress-corrosion (SSC) crack initiation and propagation took place in the weld fusion zone (WFZ) of two different kinds of American Petroleum Institute (API) grade X-65 due to the presence of elongated nonmetallic inclusions such as manganese sulfides. However, SSC crack of API grade J-55 initiated and also propagated along the pearlite band nearly perpendicular to the specimen surface of heat affected zone (HAZ) of both upper and lower half regions of the full thickness due to the globular morphology of nonmetallic inclusions such as calcium sulfides in WFZ produced by Ca treatment. And the unstable crack propagation was arrested in the midthickness region due to the orientation change of pearlite band nearly by 90˚, which gives rise to the occurrence of the stripes in the SSCC fracture surface. The SSCC kinetics of line-pipe steel weldments have been divided into the three distinct stages, namely crack incubation, slow crack propagation and unstable crack propagation stages, and were discussed in terms of nonmetallic inclusions and microstructures. It is suggested that the susceptibility to SSCC was rather affected by nonmetallic inclusions than microstructures.