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자동차용 브레이크 마찰재에서 고망간강의 마찰 및 마모특성
정광기(Kwangki Jung),이상우(Sang Woo Lee),권성욱(Sungwook Kwon),송명석(Myungsuk Song) 한국트라이볼로지학회 2020 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.36 No.2
In this study, we investigate the mechanical properties of high manganese steel, and the friction and wear characteristics of brake friction material containing this steel, for passenger car application, with the aim of replacing copper and copper alloys whose usage is expected to be restricted in the future. These steels are prepared using a vacuum induction melting furnace to produce binary and ternary alloys. The hardness and tensile strength of the high manganese steel decrease and the elongation increases with increase in manganese content. This material exhibits high values of hardness, tensile strength, and elongation; these properties are similar to those of 7-3 brass used in conventional friction materials. We fabricate high manganese steel fibers to prepare test pad specimens, and evaluate the friction and wear characteristics by simulating various braking conditions using a 1/5 scale dynamometer. The brake pad material is found to have excellent friction stability in comparison with conventional friction materials that use 7-3 brass fibers; particularly, the friction stability at high temperature is significantly improved. Additionally, we evaluate the wear using a wear test method that simulates the braking conditions in Europe. It is found that the amount of wear of the brake pad is the same as that in the case of the conventional friction material, and that the amount of wear of the cast iron disc is reduced by approximately 10. The high manganese steel is expected to be useful in the development of eco-friendly, copper-free friction material.
변준석(Junsuk Byun),나유미(Yumi Ra),권성욱(Sungwook Kwon),문주익(Juik Moon),이상억(Sangeok Lee),최인석(Inseok Choi),최원준(Won Jun Choi),민현식(Hyunsik Min),윤대성(Daesung Yoon) 대한종양외과학회 2013 Korean Journal of Clinical Oncology Vol.9 No.2
Purpose: Mental illness patients have difficulty of decision-making for treatment due to their own intellectual and socio-economic problems. Thus, doctors have a large role in course of treatment. In this study, we reviewed characters of breast cancer patients with mental illness and tried to define doctors’ role in course of treatment on the basis of our experience. Methods: We analyzed 12 patients with serious mental illness who had a difficulty on self-decision making who were treated for breast cancer between 2001 and 2012. We retrospectively reviewed medical records and relation with guardians. Results: The median age was 52 years old. Five patients were overweight with body mass index over 25 kg/m2. Seven patients had never been married and 11 patients were nullipara. Modified radical mastectomy was performed in all patients except one who received neoadjuvant chemotherapy. Nine patients were recommended chemotherapy, but only 5 patients were treated with chemotherapy and others were hormone therapy only. Four patients received chemotherapy staying with their family. A single patient was treated with chemotherapy stayed nursing home, but accompanying some intimate guardians while staying at hospital. There were two cases of recurrence, and the rest were being closely monitored without recurrence. Conclusion: More detailed and systematic diagnostic and treatment guideline were required which were not depending on each doctor’s and guardian’s unpredictable opinion in treatment of patients with severe mental illness.
Hot Spot의 시각적 분석을 통한 Hot Judder 저감의 실험적 연구
조상운(Sangwoon Cho),황선덕(Sunduk Hwang),장진성(Jinsung Jang),이정주(Jungju Lee),권성욱(Sungwook Kwon) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
This paper introduces hot judder, among the issues of NVH braking system, caused by hot spot on disc that generates unpleasant, anxious experience to the driver. Hot Judder generates around low frequency, effected by order analysis from the velocity of disc rotation. It is a phenomenon, which caused by occurrence of hot spot due to friction between disc and pad. Hot spot is the cause of the hot judder vibration. It transferred chassis, brake pedal and steering that is generated judder vibration. This study analyzes the cause of hot judder, according to the shape and property of a brake pad (type of slot, size of chamfer, compression rate and under layer). Thermal IR camera was used to visual analysis thermal behaviour and hot spot generation of disc. Correlation of DTV, BTV and thermal visual analysis were studied to analyze the cause of hot judder reduction.