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고속열차 점착계수 향상을 위한 신규 복합재료 분말 마찰조절재 개발 및 점착력 특성 평가
오민철,안병민,Oh, Min Chul,Ahn, Byungmin 한국분말재료학회 (*구 분말야금학회) 2018 한국분말재료학회지 (KPMI) Vol.25 No.6
With the recent remarkable improvements in the average speeds of contemporary trains, a necessity has arisen for the development of new friction modifiers to improve adhesion characteristics at the wheel-rail interface. The friction modifier must be designed to reduce slippage or sliding of the trains' wheels on the rails under conditions of rapid acceleration or braking without excessive rolling contact wear. In this study, a novel composite material consisting of metal, ceramic, and polymer is proposed as a friction modifier to improve adhesion between wheels and rails. A blend of Al-6Cu-0.5Mg metallic powder, $Al_2O_3$ ceramic powder, and Bakelite-based polymer in various weight-fractions is hot-pressed at $150^{\circ}C$ to form a bulk composite material. Variation in the adhesion coefficient is evaluated using a high-speed wheel-rail friction tester, with and without application of the composite friction modifier, under both dry and wet conditions. The effect of varying the weighting fractions of metal and ceramic friction powders is detailed in the paper.
오민철 ( Min Chul Oh ),최윤정 ( Yoon Jung Choi ),양국희 ( Kook Hee Yang ) 대한뇌종양학회·대한신경종양학회·대한소아뇌종양학회 2009 대한뇌종양학회지 Vol.8 No.2
Gliosarcoma is an uncommon malignant brain tumor with biphasic tissue pattern consisted of both glial and sarcomatous components. Extracranial metastasis of gliosarcoma is extremely rare. We report a case of 61-year-old male who developed lung metastasis clinically from a left frontal gliosarcoma. The patient initially presented with progressively worsening headaches, right-sided numbness associated with left frontal brain tumor. He underwent surgical resection of tumor followed by radio- and chemotherapy for a primary gliosarcoma. Seven months following initial resection , the patient`s clinical status deteriorated with dyspnea and CT scan demonstrated a lung mass. Pathologic examination of lung mass revealed wide-spread, infiltrating malignant spindle cell clinically from primary gliosarcoma. To our knowledge this is the first reported case of gliosarcoma with lung metastasis in Korea.
장갑강 아크용접부의 방탄시험 대체검증 표준 제정에 대한 연구
김용(Yong Kim),오민철(Min Chul Oh),장지영(Ji Young Jang),김도희(Do Hui Kim) 대한용접·접합학회 2024 대한용접·접합학회지 Vol.42 No.1
The final goal of this study is to secure the basis for establishing a domestic test standard such that the H-plate ballistic test for weld verification required by TACOM Drawing 12479550 can be replaced with the Charpy impact test. The core of this study is to prove the correlation between the ballistic test and the impact test. As a result of ballistic test specimens manufactured with various welding parameters, the generated crack length showed a correlation of approximately 78% with impact toughness. In addition, cracks occurred at the weld toe and propagated along the fusion line irrespective of any variables. Therefore, the notch location of the impact test specimen was determined by the fusion line. Moreover, experiments proved that impact toughness did not change significantly when changing non-essential welding variables. The impact toughness of the fusion line critical values of MIL-A-12560 and MIL-A-46100 materials used in this study were 50 J and 22 J, respectively. This value exceeded the impact toughness management standard for the base material. Therefore, the passing threshold value was ultimately determined to be above the impact toughness threshold of the base material.
Al/Cu 레이저 용접에서 입열 및 간격에 따른 용접부 기계/금속학적 특성 연구
이찬양(Chan Yang Lee),오민철(Min Chul Oh) 대한용접·접합학회 2024 대한용접·접합학회지 Vol.42 No.1
The electrical connectivity and tensile strength between battery components are crucial factors for enhancing battery performance in electric vehicles. In this study, the welding characteristics of aluminum-copper welded joints manufactured using the multi-core laser welding process were studied according to the output power of core/ring laser. Moreover, the tensile strength change behavior according to various welding processes, such as single/two-line welding, and welding gap distance were measured. The results revealed that increasing the output power of the ring beam led to an increase in the tensile strength. However, excessive laser power would increase convection between aluminum and copper during welding and cause defects owing to the difference in the solidification temperature between the two materials. In addition, the mechanical properties were improved by increasing the distance between the two lines of straight laser welding. As the spacing increased, the fraction of the equiaxed microstructure increased, and grain growth was suppressed to improve mechanical properties.