• 한국자동차공학회논문집
• /
• 제7권9호
• /
• pp.172-181
• /
• 1999

The brakes employed on commercial vehicles must be able to withstand three types of demanding services which are use-emergency stops from high speed, many repeated stops as in a delivery or bus route, and speed control in mountain descents. Two type of friction brakes are in use ; drum breaks and disc brakes. Drum brakes are of the internally expanding type in which two shoes fitted externally with friction material are forced outward against the inside of a rotating drum on the wheel unit. In this case, the Braking power is produced by the friction force between a drum and a lining, and is converted into heat. In this research an unsteady state heat transfer analysis for drum brake system of heavy truck has been performed by ABAQUS/standard code in the case of single-braking and the repeated braking condition. The temperature histories obtained by the finite Element analysis have been compared with the result calculated by the simplified formulation and the result obtained by the experiment of real vehicle conditions.

• Tribology and Lubricants
• /
• 제5권1호
• /
• pp.21-27
• /
• 1989

A paper facirig, used for clutch disc or brake lining of the vehicles, is consisted of a combination of cellulose fiber of pulp with assorted filler and friction imparting particles, impregnated with a thermo-setting resin. In this study, as a substitution for the paper-production method, the molding-production method was attempted to produce the paper facings, and their frictional characteristics were investigated. According to the experimental results, it was estimated that the paper facings added with silica (SiO$_2$) have superior frictional characteristics, which is mused by the porosity and Mobs' hardness of the silica (SiO$_2$).

• 한국지진공학회논문집
• /
• 제17권5호
• /
• pp.227-235
• /
• 2013

Friction energy dissipative devices have been increasingly implemented as structural seismic damage protecting systems due to their excellent seismic energy dissipating capacity and high stiffness. This study develops rotational friction energy dissipative devices and verifies experimentally their cyclic response. Based on the understanding of the differences between the traditional linear-motion friction behavior and the rotational friction behavior, the configuration of the frictional surface was determined by investigating the characteristics of the micro-friction behavior. The friction surface suggested in this paper consists of brake-lining pads and stainless steel sheets and is normally stressed by high-strength bolts. Based upon these frictional characteristics of the selected interface, the rotational friction energy dissipative devices were developed. Bolt torque-bearing force tests, rotational friction tests of the suggested friction interfaces were carried out to identify their frictional behavior. Test results show that the bearing force is almost linearly proportional to the applied bolt torque and presents stable cyclic response regardless of the experimental parameters selected this testing program. Finally, cyclic tests of the rotational friction energy dissipative devices were performed to find out their structural characteristics and to confirm their stable cyclic response. The developed friction energy dissipative devices present very stable cyclic response and meet the requirements for displacement-dependent energy dissipative devices prescribed in ASCE/SEI 7-10.

• 한국산업보건학회지
• /
• 제1권2호
• /
• pp.144-153
• /
• 1991

This study was conducted to evaluate worker exposure to airborne asbestos fibers by industry, and to evaluate polarized-light microscopy for determining airborne asbestos fibers. A total of 11 plants including asbestos textile, brake-lining manufacturing, slate manufacturing, and automobile maintenance shops were investigated. Rsults of the study are summarized as follows. 1. Worker exposure levels to airborne asbestos fibers were the highest in asbestos textile industry, followed by brake-lining manufacturing, slate manufacturing, and automobile maintenance shops, in order. In asbestos textile industry, large variation of asbestos levels was found by plants. The worst plant indicated airborne fiber concentrations in excess of 10 fibers/cc, however, the best plant showed concentrations within 0.50 fibers/cc. 2. Characterization of airborne fibers by industry indicated that fibers from asbestos textile industry were the longest with the largest aspect ratio. Fibers from automobile maintenance shops were the shortest with the smallest aspect ratio. Based on characteristics of fibers and the highest levels of concentrations, it is concluded that workers in the asbestos textile industry are exposed to the highest risk of producing asbestosis, lung cancer, and mesothelioma. 3. Result s obtained using polarized-light microscopy were $43.7{\pm}12.3%$ of the results obtained using phase contrast microscopy. This may be resulted from the worse resolution of polarized-light microscopy than that of phase contrast microscopy. Based on the results, it is recommended that polarized-light microscopy be used for mainly bulk sample analyses and further study be performed to improve the method for determining airborne samples. However, polarized-light microscopy can be used for determining thick fibers.

• 한국산업보건학회지
• /
• 제19권3호
• /
• pp.307-320
• /
• 2009

This study was conducted not only to review airborne asbestos levels reported in workplaces in Korea, but also to analyze their levels according to various characteristics All asbestos concentration reported as either geometric mean (GM) and geometric standard deviation (GSD) or ranges were transformed to arithmetic mean to estimate exposure level. In addition, weighted arithmetic means (WAMs) were calculated to weigh asbestos levels based on the different number of samples. Differences of asbestos levels among several characteristics such as industry type, decade, operation and sampling and analytical methods were analyzed using analysis of variance (ANOVA). The number of articles studying asbestos levels from workplaces was found to be 9 including two report types. Five of those were reported prior to 1990s and rest of them after 1990s. Only several industries such as asbestos textile, asbestos cement, brake-lining repair shops were studied, while various industries using asbestos or asbestos containing materials (ACMs) were not studied. ANOVA found that asbestos exposure levels (WAM = 5.26f/cc) reported from textile industry were significantly higher than those from other industries (cement = 0.63f/cc, brake-lining = 0.2f/cc - 0.47f/cc) (p < 0.0001). Average exposure levels studied prior to the 1990s (3.13f/cc) were found to be significantly higher than that (0.86f/cc) after the 1990s (p<0.0001). All WAMs reported until the 1994 were found to be higher than the current occupational exposure limits (0.1f/cc). This study recommends that retrospective exposure to asbestos based on various industry types and operations should be assessed.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2012년도 추계학술대회 논문집
• /
• pp.546-552
• /
• 2012

This paper is a study on squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material. For this, data of pressure and temperature dependent material properties of lining is achieved by using lining data base and exponential curve fit. Complex eigenvalue analysis is performed for predicting squeal noise frequency and instability and chassis dynamo test is performed for achieving squeal noise frequency, sound pressure level, occurrence temperature & pressure. Initial multi models are composed for considering complex interface conditions such as pad ear-clip, piston-housing and guide pin-torque member. The simulation result of base models is compared with the test result. Squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material is performed and analyzed using multi models. And additional condition is disc material property variation. Entire simulation conditions are combined and analyzed. Finally, this paper proposes direction of the warm squeal noise model.

• 한국자동차공학회논문집
• /
• 제20권6호
• /
• pp.24-32
• /
• 2012

A large fraction of urban $PM_{10}$ concentrations is due to non-exhaust traffic emissions including road dust, tire wear particles, and brake lining particles. Although potential health and environmental impacts associated with tire wear debris have been increased, few environmentally and biologically relevant studies of actual tire wear debris have been conducted. Tire wear particles (TWP) are released from the tire tread as a result of the interaction between the tire and the pavement. Roadway particles (RP), meanwhile, are particles on roads composed of a mixture of elements from tires, pavements, fuels, brakes, and environmental dust. The main objective of present study is to identify the contribution of tires to the generation of RP and to assess the potential environmental and health impacts of this contribution. First, a mobile measurement system was constructed and used to measure the roadway particles on asphalt road according to vehicle speed. The equipment of the mobile system provides $PM_{10}$ concentrations by Dusttrak DRX and number density & size distribution measurements of fine and ultra-fine particles by a fast mobility particle sizer (FMPS) and an aerosol particle sizer (APS). When traveling on an asphalt road at constant speed, there is a clear tendency for PM10 concentration to increase slightly in accordance with an increase in the vehicle speed. It was also found that considerable brake wear particles and particles from tire/road interface were generated by rapid deceleration of the vehicle. The morphology and elements of the roadway particles were also analyzed using SEM-EDX technique.

• 한국항해항만학회지
• /
• 제34권10호
• /
• pp.775-780
• /
• 2010

기계장치에 있어서 브레이크 시스템은 기계의 안전상 동작만큼이나 중요한 부분이다. 기계를 급히 정지시켜야하는 비상시에 기계가 멈추지 않으면 큰 사고로 발전할 수 있기 때문이다. 이것은 모든 기계장치에서 공통된 사항이며, 선박에서 또한 마찬가지이다. 선박에는 2종류의 계류장치가 존재한다. 그 중 하나는 항해하는 선박을 근해에 정박시키기 위해서는 해저에 닻을 내리는 윈드라스 윈치이며, 또 다른 하나는 배를 항구에 계류시키기 위한 무어링 윈치이다. 그 중 기존에 사용하는 무어링 윈치의 경우, 브레이크 밴드가 하나의 철판으로 만들어져 있으며, 브레이크 밴드와 라이닝을 연결하는 볼트의 파손이 발생하게 된다. 본 연구에서는 이 파손을 방지하기 위해 유한요소해석 프로그램을 사용하여 응력이 집중되는 부위를 선정하였고, 이 부위를 분리하여 응력 집중을 해소하였다, 또한 이 분리지점의 각도에 따른 해석을 수행하여 최적의 위치를 선정하였다.

• 한국산업보건학회지
• /
• 제26권2호
• /
• pp.219-224
• /
• 2016

Objectives: Lung cancer occurred with worker working in an urban bus garage. A survey was conducted to investigate whether lung cancer had causal relationship with work. Exposure to asbestos and diesel engine exhaust were suspected. Methods: Airborne asbestos was sampled on membrane filter and analyzed using phase-contrast microscopy. Airborne diesel exhaust was sampled using quartz filter and analyzed with thermal-optical analyzer. Polynuclear aromatic hydrocarbons was sampled using PTFE filter and XAD-2 tube and analyzed with gas chromatography-mass selective detector. Results: Airborne asbestos concentration was under 0.01 fiber/cc. Worker who warmed up an engine of urban bus for 2 hours was exposed to elemental carbon concentration, $15.5{\mu}g/m^3$. Only naphtalene among polynuclear aromatic hydrocarbons was detected. Conclusions: It was difficult to conclude about worker exposure to asbestos because working hour related asbestos was too short. In reviewing papers, the exposure to asbestos over 0.01 fiber/cc during exchange brake lining was found. It was identified that worker's occupational exposure to diesel exhaust based on elemental carbon was higher than the other occupational exposure to diesel exhaust.

• Journal of Preventive Medicine and Public Health
• /
• 제25권3호
• /
• pp.269-286
• /
• 1992

The purpose of this study is to investigate the present state of worker's recognition and attitude about hazard materials and occupational disease in his workplace. In general worker's view of hazard materials and occupational disease that sis recognition and attitude is related to worker's health behavior for preventing occupational disease and improving his health status. The study subject is composed of workers in the asbestos related industry for example brake lining manufacturing industry, asbestos fiber manufacturing industry, and asbestos slate manufacturing industry. The result of the study are follows : 1. The most of workers in the asbestos related industry have taken health education and safety education, and the more than half of workers recognized the usefulness of preventive device, and ventilatory device in workplace. 2. About 70% of workers have always taken the preventive device. 3. About 80% of workers have recognized occupational disease in the asbestos related industry, and about 64% of workers have recognized that hls workplace have harmful effect on his health. 4. Recognition about the usefulness of ventilatory device in work place has not related with any variables. But recognition about the usefulness of repiratory protector has related with recognition of hazard materials in his workplace, for example asbestos. 5. Attitude about severity and susceptability of occupational disease in the asbestos related industry have related with knowledge about hazard materials and occupational disease.