Effect of Electrochemical Hydrogen Charging Time on Hydrogen Embrittlement of the Hot-Rolled and Accelerated Cooling Treated API X70 Steel

Dong‑Su Bae,Un‑Bong Baek,Seung‑Hoon Nahm,Ilguk Jo 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.2

This study investigated the effect of the hydrogen charging time on the hydrogen embrittlement of hot-rolled and acceleratedcoolingtreated API X70 steel by using the electrochemical hydrogen charging method. Tensile and V-notch Charpy impacttest were completed for the specimens of hydrogen charged for 0, 2, 4, and 10 h, and then microstructural observation wereperformed. The tensile and yield strength tended to decrease slightly and the total elongation started to decrease rapidly up to2 h charging time and then these gradually decreased with the hydrogen charging time. The post-uniform elongation increasedslightly after the holding time of 2 h due to the occurrence of two-step stress reduction phenomenon and its mechanismhas suggested. The effect of the hydrogen embrittlement on impact absorption energy according to the hydrogen chargingtime were also investigated. The fracture surface of the hydrogen charged ones are generally composed of cleavage fracturesurfaces. It was demonstrated that the external cracks were formed on the outside of tensile tested specimen and the externalshape of the fracture portion was fractured without large elongation at hydrogen charged specimens.

STS304 용접 열영향부의 조사손상에 미치는 He 주입의 영향

배동수 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.12

The heat affected zone (HAZ) of welded STS304 has been irradiated by using three irradiation modes of electron-beam irradiation, electron-beam irradiation after He-injection and electron/He ion dual-beam irradiation in 1250 kV high voltage electron microscope (HVEM) connected with an ion accelerators to study the effect of Heinjection on microstructural evolution. The size of voids increases considerably and their distribution is a bi-mode shape, when electron-beam is irradiated after He-injection. Void swelling percentage is largest in the case of electronbeam irradiation after He-injection. In cases of electron/He^(+)-ion dual-beam and electron-beam irradiation after Heinjection, the amount of grain boundary segregation is suppressed when compared with the case of electron-beam irradiation.

이동 애드 혹 네트워크에서의 환경적응형 QoS AODV 라우팅 프로토콜에 관한 연구

裵振勝,宋東勳,吳世德,鄭燦赫,金玄郁,李光培,文泰洙,郭承郁,河載承 明知大學校 産業技術硏究所 2004 産業技術硏究所論文集 Vol.23 No.-

In this paper, we propose a bidirectional mobile Ad Hoc routing protocol based on AODV(ad-hoc on-demand distance vector routing) with QoS(quality of service) support. At presence, wireless mobile communication focuses on how to efficiently support mobility of users more than QoS guarantee. However, in order to satisfy requirement of various applications which have been or will be served, QoS guarantee between end points is a very important issue. The existing AODV routing protocol is implemented to use only BE (Best Effort) service. However, actual wireless mobile environment requires to reduce a waste of communication resources and meet with the real-time change of data paths by setting up routes with QoS support, considering available communication resources at each node in advance. Therefore, in this thesis, we propose an adaptive QoS support method using hello message in order to rapidly meet with the change of available communication resources and to smoothly perform route maintenance. For performance evaluation, we analyzed the average data reception rate. At that time, we used evaluation parameters such as node's mobility-stop time, hello message period, and packet priority, considering the node's mobility and the number of best effort/QoS data flows. As results, we found that with our proposed method the average data reception rate was increased 16.293%, 15.914%, 17.238% for 300 mobility-stop second case and 4.809%, 4.264%, 2.956% for 300 mobility-stop second case.

STS 304 강의 용접부에 미치는 전자선 조사의 영향

裵東樹,鄭鎬信,姜昌龍 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.4

The heat affected zone(HAZ) and matrix of a welded STS 304 steel have been irradiated in an 1250 keV high voltage electron microscope at 673 K and up to 5.4 dpa(displacements per atom) to study the effect of electronbeam irradiation on the microstructure. In-situ observation showed that the voids formed by electron-beam irradiation coalescenced and grew to larger void with irradiation dose. Values of void size, void number density and void swelling percentage in HAZ were greater than those of matrix, and these were increased and then saturated gradually with irradiation dose. Non-equilibrium segregation phenomena such as Cr depletion and Ni enrichment were also observed in both the HAZ and matrix of welded STS304 steel at the grain boundary.

입자빔을 이용한 STS304강의 전자선조사 손상거동

裵東樹 동의대학교 산업기술개발연구소 2001 産業技術硏究誌 Vol.15 No.-

The heat affected zone of a welded STS304 steel has been irradiated in an 1300keV high voltage electron microscope at 673K and up to 5.4 dpa(displacements per atom) to study the effect of electron-beam irradiation on irradiation damage microstructure. The dislocation loop density of initial irradiation state was increased with electron-beam irradiation. Void size, void number density and void swelling percentage were increased and then saturated gradually with irradiation dose. The depletion of Cr and the enrichment of Ni were also recognized in HAZ part of welded STS304 steel at the grain boundary by EDS analysis, as reported already the same tendency for matrix material.

고 Mn-Cr 강의 조사손상에 미치는 전자선 조사 온도의 영향

배동수,정호신,강창용,남승훈,이해무 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.3

The effect of electron-beam irradiation temperature on irradiation damage of 12%Cr-15%Mn austenitic steel for structural material of nuclear and/or fusion reactors from the point of view of the reduced activation was investigated by using the 1,250 keV HVEM and an energy dispersed X-ray analyzer(EDX) in a 200 keV FE-TEM with beam diameter of about 0.5 nm. Void formation was not observed in irradiated specimen. The dislocation loop growth was observed and the density and size of dislocation loop were increased with irradiation dose. Irradiation-induced segregations of Cr and Mn at grain boundary were also observed by electron-beam irradiation condition. The amount of Mn segregation was increased with irradiation temperature, however, segregation phenomenon was disappeared in the case of Cr.

외부로의 열소산과 유속의 불균형성이 촉매변환기의 비정상 여 및 변환 특성에 미치는 영향

배상수,강동진 嶺南大學校 工業技術硏究所 1997 工業技術硏究所論文集 Vol.25 No.2

A transient axistymmetric model is used to simulate the thermal and conversion characteristics of a monolithic catalytic converter operating under warm-up conditions. The model takes into account the gas-solid heat and mass transfer, axial and radial heat conduction, chemical reactions and the attendant heat release, and heat loss to the surrounding. The model has been used to analyze the transient response of an axisymmetric ceramic monolith system (catalytic monolith, mat, and steel shell) during warm-up with respect to heat loss and flow nonuniformity at inlet. Numerical solutions indicate that wall temperature and CO conversion efficiency are much more dependent on the flow nonouniformity than that loss. Three dimension effects due to heat loss to the surrounding is localized near the steel shell. The flow nonuniformity plays a major role even inside the catalytic monolith. The convective that transfer due to flow nonuniformity balance with the exothermic reaction and this balance determiness steady state temperature distribution. As the amount of catalytic material increase the exothermic reaction becomes dominant in steady state.

족관절 삼과골절에서 후과골절편이 외상후 관절통증에 미치는 영향

배서영,신동훈 대한골절학회 2003 대한골절학회지 Vol.16 No.1

목 적 : 족관절 삼과골절에서 후과 골절편의 정복과 고정 여부에 관하여는 논란이 있으나 골절편의 크기가 관절면의 25~30% 이상을 차지하는 경우 고정이 필요하다는 주장이 일반적으로 받아들여지고 있다. 저자들은 후과 골절편의 크기 및 고정 여부가 실제로 임상결과에 영향을 주는 가장 중요한 인자인지 알아보고자 하였다. 대상 및 방법 : 본원에서 동반손상이 없는 족근관절 삼과골절로 치료받았으면서 내과 및 외과의 해부학적 정복이 이루어진 73명중 2년 이상 추시 가능하였던 30명을 대상으로 하였다. 수상 직후와 정복 직후의 측면사진에서 후과 골절편의 크기를 관절면을 차지하는 정도(%)로 측정하고 정복 직후 사진에서 잔존하는 전위 정도를 골편 간극과 관절면의 층짐으로 나누어 측정하였다. 또한 의무기록의 조사를 통해 후과의 고정 여부, 관절운동의 시작시기, 체중부하 시작시기를 조사하였다. 임상 결과는 AOFAS(American Orthopaedic Foot and Ankle Society)의 기준에 따라 통증, 기능, 정렬에 대해 점수를 매기고 추시상 관절의 통증이 남은 군과 통증이 없는 군으로 나누어 각 인자들 중 어떤 인자에 의해 좌우되는지 로지스틱 회귀분석과 Chi-square교차분석을 통해 유의수준 5%로 알아보았다. AOFAS 점수 중 기능이나 정렬 면에서는 차이가 없었으며 관절 불안정을 보이는 경우도 없었으며 운동범위의 제한을 보이는 경우가 1예 있었다. 관절통을 호소하는 군은 7명, 통증이 없는 군은 23명이었고 두 군간에 잔존하는 골절편의 간극과 관절면의 층짐 정도는 유의한 인자였으나 골편의 크기나 고정여부, 관절운동 시작시기, 체중부하 시작시기 등에서는 유의성을 검증할 수 없었다. 결 론 : 삼과골절에서 후과 골절편은 크기나 고정 여부보다도 정복 후 골절편의 간극이나 층짐이 임상결과, 특히 관절통증에 더 영향을 미치므로 고정 여부에 상관없이 정복후 정복 상태에 대한 정확한 평가가 필요하고 골편의 크기에 상관없이 해부학적 정복이 필요할 것으로 사료된다. 또한 후과의 부정위는 내외 양과의 골절이 해부학적으로 정복된다면 족관절 기능이나 불안정보다는 통증을 유발하는 것으로 사료된다. Purpose : There are some criticisms of indication for internal fixation of the posterior malleolar fragments in trimalleolar fractures. We tried to find out clinical and radiologic factors which affect on a clinical outcome of triballerolar fractures. Materials and Methods : Thirty three patients who were treated for trimalleolar fractures and given anatomical reduction of lateral and medial malleolus were included. We divided patients into two groups, a group without the pain and the other group with the pain. Preoperative and postoperative lateral plain radiographic films were used to estimate fragment size, post-reduction gap and step off. By reviewing the medical records, other factors such as the time of ankle motion, weight loading and whether posterior malleolus was fixed. Or not were studied. A clinical outcome was evaluated by ASFAS(American Orthopaedic Foot and Ankle Society) scaling system. We performed statistical analysis using Logistic regression analysis and Chi-square test on each factors. Results : There was no definite difference between two groups on the functional outcome. There was one case showing limited ankle motion. Seven patients were involved in the group with the pain and 23 in the group without the pain. The remnant fracture gap and step off of joint surface statistically showed the meaningful corellation with the pain but a fragment size and a surgical fixation, time of motion and weight loading did not show any significances. Conclusion : We doubt the significance of the size of posterior malleolar fragment. We concluded that anatomical reduction of posterior malleolus is the most significant factor of a clinical outcome regardless of the size or internal fixation, especially the pain after trimalleolar injuries.

절연, 내열, 충격특성이 우수한 Tube 개발

裵東樹 동의대학교 산업기술개발연구소 2001 産業技術硏究誌 Vol.15 No.-

A tube with high insulated, heat-resisting and impact properties was developed for industrial applications. Reference tubes for development a new tube were adapted the common ceramics one and a new material tube made by some american company. These tubes were analyzed and compared with a new tube by testing the Charpy impact test and heat-resisting test. And a new tube has prior properties of heat-resisting and toughness with reference ones.

?? 이종접합구조에 대한 격자이완 및 결정성의 변화

이동건,김종수,손정식,배인호,문영희 嶺南大學校 基礎科學 硏究所 1998 基礎科學硏究 Vol.18 No.-

We have investigated the lattice relaxation and crystalline qualities of InGaAs/GaAs heterostructure as a function of the layer thickness. The ?? heteroepitaxial layers were grown by molecular beam epitaxy(MBE).The eqilayer thickness were from 230 Å to 3 ㎛ with composition around ×=0.15. The lattice constants c obtained using double axis diffractometry(DAD) as a function of the layer thickness were constant until 1000 Å. Change in lattice constant of surface normal appeared at the thickness of1200 Å, and it decreased as layer thickness increased. The relaxation of epilayers were from 32% at 1200 Å to 84% at 3 ㎛, and the crystalline qualities of epilayers with increased with increasing thickness.