• Tribology and Lubricants
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• 제33권1호
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• pp.15-22
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• 2017

Because the running speed of vehicles is increasing and a shorter braking distance is required, high heat-resistant brake pads are needed to satisfy the requirements of customers and car makers. In the near future, hazardous materials such as Cu, Cr, Zn, and Sb will be restricted from use in friction materials. Ceramic composites reinforced by carbon fibers are good candidates for eco-friendly friction materials. In this study, we develop ceramic composite friction materials. The friction materials are composed of carbon fibers, Si, SiC, graphite, and phenol resin and are prepared by hot forming and heat treatment at high temperatures. The density, void ratio, and compressive strength are $1.59-1.66g/cm^3$, 16.6-20, and 70-90 MPa, respectively. Friction and wear tests are performed using a pin-on-plate-type reciprocating friction tester at 25, 100, and $200^{\circ}C$. The counterpart material is a CrMoV steel extracted from a KTX brake disc. Friction coefficient, wear amount, and wear mechanism are measured and examined. We determine that the friction coefficients depend on the temperature and the fluctuation of the friction coefficients is larger at higher temperatures. The amount of wear increases with the surface temperatures of the specimens. The tribological properties of the developed composites are similar to those of a Cu-based sintered friction material. Through this study, it is confirmed that ceramic composite materials can be used as friction materials.

• Steel and Composite Structures
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• 제24권2호
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• pp.239-248
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• 2017

Friction dampers are displacement dependent energy dissipation devices which dissipate earthquake energy through friction mechanism and widely used in improving the seismic behavior of new structures and rehabilitation of existing structures. In this paper, the cyclic behavior of a friction damper with different friction materials is investigated through experimental tests under cyclic loading. The damper is made of steel plates, friction pads, preloaded bolts and hard washers. The paper aims at investigating the hysteretic behavior of three friction materials under cyclic loading to be utilized in friction damper. The tested friction materials are: powder lining, super lining and metal lining. The experimental results are studied according to FEMA-356 acceptance criteria and the most appropriate friction material is selected by comparing all friction materials results.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.115-122
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• 2007

The noises which occurs from the rolling stock can be divided largely into three classes and they are Rolling noise, Traction noise and Aerodynamic noise. In the event of braking the rolling stock which enter into the station, Brake shoes cause Fraction noise (braking noise) and excessive braking noise makes passengers and operators uncomfortable. This study is to reduce squeal noise and minimize displeasure by measuring the braking noise and defining the major noise sources and noise mechanism

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.144-149
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• 2008

A transient finite element simulation is developed for the two-dimensional stationary elastoplastic layer between sliding layers, to investigate thermoelastoplastic instability(TEPI) due to frictional heating in the material. The analysis will show some differences between the case of thermoelastic instability and TEPI, especially according to the contact pressure above yield stress. A transient behavior of contact pressure is captured to explain the behavior of thermoplasticity of contact with different sliding velocity. The instability of contact pressure in the long range of braking time will be explored to understand the generation mechanism of hot spots.

• 대한기계학회논문집A
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• 제35권7호
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• pp.723-728
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• 2011

진공회로차단기의 성능이 스프링조작기에 많이 좌우되기 때문에, 스프링조작기의 해석이 요구된다. 본 연구에서는 스프링의 특성시험을 먼저 수행한 후, 시험결과를 RecurDyn 프로그램을 이용한 컴퓨터시뮬레이션 스프링모델링에 이용하였다. 개발된 진공회로차단기의 다물체동역학 모델을 이용하여 차단기의 스템변위와 샤프트 회전각에 대한 시뮬레이션 하였으며, 시뮬레이션 결과를 시험과 비교 검증하였다. 검증된 다물체동역학 모델을 사용하여 차단속도를 증가시키기 위한 캠의 최적윤곽을 얻었다.

• 한국항공운항학회지
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• 제26권3호
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• pp.40-47
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• 2018

Reducing aircraft speed is the important task in the Rejected Takeoff and/or landing process. It is known that the effect of the Speedbrake is most important factor during the rejected takeoff maneuver in particular near V1 on the critical field length runway. The B747 designer created Automatic Speedbrake Control System to relieve pilot workload, improves brake operation and ensures proper Speedbrake operation for rejected take off. However, those who make the Rejected Takeoff procedure ignored the Automatic function and made it does all manual operations. This lets procedures difficult, complicated, and a cause of confusion and pilot error. This study was conducted to commentary the mechanism and function of the Automatic Speedbrake Control System of B747-8 and to propose appropriate B747-8 Rejected Take off procedures for its function to reduce the workload of pilots and contribute to reduce the possibility of pilot error during Rejected Takeoff.

• 한국자동차공학회논문집
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• 제19권2호
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• pp.42-49
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• 2011

To expand lean misfire limit and improve combustion stability, the effects of port masking were estimated to secure basic data for applying the mechanism to SI engine instead of asymmetrical port and port throttling devises. For this purpose, various shapes and ratios of masking plates were mounted between port and manifold. The masking effects were evaluated by mixture response test under various load and speed conditions. The results showed that lean misfire limits were expended and fast combustion was observed for all masking shapes and ratios, especially, the effect of diagonal 1/4 masking was remarkable. In conclusion, the port masking method could be easily applied to engine without redesign of port for improving part load performance.

• 제어로봇시스템학회논문지
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• 제16권11호
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• pp.1060-1067
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• 2010

In this paper, we present a new type of spherical robot having two arms. This robot, called KisBot, mechanically consists of three parts, a wheel-shaped body and two rotating semi-spheres. In side of each semi-sphere, there exists an arm which is designed based on slider-crank mechanism for space efficiency. KisBot has hybrid types of driving mode: rolling and wheeling. In the rolling mode, the robot folds its arms through inside of itself and uses them as pendulum, then the robot works like a pendulum-driven robot. In the wheeling mode, two arms are extended from inside of the robot and are contacted to the ground, then the robot works like a one-wheel car. The Robot arms can be used as a brake during rolling mode and add friction to the robot for climbing a slope during wheeling mode. We developed a remote controlled type robot for experiment. It contains two DC motors which are located in the center of each semi-sphere for main propulsion, two RC motors for each arm operation, speed controllers for each semi-sphere, batteries for main power source, and other mechanical components. Experiments for the rolling and wheeling mode verify the hybrid driving ability and efficiency of the our proposed spherical robot.

• 한국공간구조학회논문집
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• 제4권1호
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• pp.77-86
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• 2004

시공시 콘크리트의 하중은 받는 데크플레이트의 지지능력은 압축부분 플랜지에서 좌굴에 의해서 결정되어 진다. 얇은 철판 데크플레이트의 압축플랜지에서 중간스티프너의 크기와 위치는 플랜지의 좌굴모드에 강한 영향을 발휘한다. 높은 강도 철판으로 구성된 시험체 단면은 다양한 좌굴모드를 유도하기 위하여 작은 것에서 큰 스티프너에 걸쳐 압축플랜지에 만들어 졌다. ABAQUS 프로그램 해석은 좌굴모드를 지배하는 중간스티프너의 효과를 결정하기 위하여 수행되었다. 각 실험체 시리즈는 단순보로 순수휨이 적용되었다. 실험결과 소성파괴 메카니즘을 통하여 극한파괴에 앞서 다양한 좌굴형상이 나타났다. 실험으로 결정되어진 좌굴응력은 ABAQUS해석으로 얻어진 해석결과와 각국의 규준값들과 비교하기 위하여 사용되었다.

• International Journal of Automotive Technology
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• 제8권2호
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• pp.203-209
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• 2007

As the vehicle electronic control technology quickly grows and becomes more sophisticated, a more efficient means than the traditional in-vehicle driving test is required for the design, testing, and tuning of electronic control units (ECU). For this purpose, the hardware-in-the-loop simulation (HILS) scheme is very promising, since significant portions of actual driving test procedures can be replaced by HIL simulation. The HILS incorporates hardware components in the numerical simulation environment, and this yields results with better credibility than pure numerical simulations can offer. In this study, a HILS system has been developed for ESP (Electronic Stability Program) ECUs. The system consists of the hardware component, which that includes the hydraulic brake mechanism and an ESP ECU, the software component, which virtually implements vehicle dynamics with visualization, and the interface component, which links these two parts together. The validity of HIL simulation is largely contingent upon the accuracy of the vehicle model. To account for this, the HILS system in this research used the commercial software CarSim to generate a detailed full vehicle model, and its parameters were set by using design data, SPMD (Suspension Parameter Measurement Device) data, and data from actual vehicle tests. Using the developed HILS system, performance of a commercial ESP ECU was evaluated for a virtual vehicle under various driving conditions. This HILS system, with its reliability, will be used in various applications that include durability testing, benchmarking and comparison of commercial ECUs, and detection of fault and malfunction of ESP ECUs.