• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2004년도 춘계학술대회 논문집
• /
• pp.315-321
• /
• 2004

Dawin Friction Corp. has been advanced sintered brake pad for Korean concept high speed train (so called G7 train) with KRRI, You Jin and Rotem without the assistance of foreign company. In the course of development, the evaluation of our and foreign disk pads was performed by lab scale dynamometer and full scale dynamometer. As the result of dynamo test, it is shown that our developed brake disk is equal or superior to those of foreign companies in many respects, for example, wear resistance, noise, etc. The new brake pad which is developed through 'post G7-project' is equipped with G7 train and is under many tests without any problems at the present moment.

• Smart Structures and Systems
• /
• 제30권5호
• /
• pp.479-500
• /
• 2022

In this study, a new type of isolation bearing is proposed by combining S-shaped steel plate dampers (SSDs) with a spherical steel bearing, and the seismic control effect of a five-span standard high-speed railway bridge is investigated. The advantages of the proposed S-shaped steel damping friction bearing (SSDFB) are that it cannot only lengthen the structural periods, dissipate the seismic energy, but also prevent bridge unseating due to the restraint effectiveness of SSDs in the large relative displacements between the girders and piers. This study first presents a detailed description and working principle of the SSDFB. Then, mechanical modeling of the SSDFB was derived to fundamentally define its cyclic behavior and obtain key mechanical parameters. The numerical model of the SSDFB's critical component SSD was verified by comparing it with the experimental results. After that, parameter studies of the dimensions and number of SSDs, the friction coefficient, and the gap length of the SSDFBs were conducted. Finally, the longitudinal seismic responses of the bridge with SSDFBs were compared with the bridge with spherical bearing and spherical bearing with strengthened shear keys. The results showed that the SSDFB can not only significantly mitigate the shear force responses and residual displacement in bridge substructures but also can effectively reduce girder displacement and prevent bridge unseating, at a cost of inelastic deformation of the SSDs, which is easy to replace. In conclusion, the SSDFB is expected to be a cost-effective option with both multi-stage energy dissipation and restraint capacity, making it particularly suitable for seismic isolation application to high-speed railway bridges.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2004년도 학술대회지
• /
• pp.60-65
• /
• 2004

[ $MoS_2S$ ] is a well-known metal sulfide applied as solid lubricants and an additive to prolong the life of sintered bearings under severe conditions. However, the high price of $MoS_2S$ limited its wide application. This study is aimed to investigated the possibility for application to solid lubricants for $Cu_2S$ as a substitute of v. Bronzes added $Cu_2S$ and $MoS_2S$ are produced by powder metallurgy in this study, and then evaluated their friction and wear properties. The sliding wear test using pin-on-disc type machine, was conducted at several sliding speeds for three type test pieces, bronze and bronzes added $Cu_2S/MoS_2$. Addition of $Cu_2S$ to bronze leads to relatively good friction and wear properties, although it is not so good as addition of $MoS_2S$. But the properties of bronze added $Cu_2S/MoS_2$ would be not suitable for the condition under the high sliding speed.

• Tribology and Lubricants
• /
• 제21권2호
• /
• pp.77-82
• /
• 2005

In previous paper, the wear properties of clutch facing materials with two different copper amounts against fly-wheel materials used in the clutch system were investigated by sliding wear tests at different applied loads and speeds. This paper have been aimed to evaluate the friction properties for clutch facing materials at the same test conditions as the previous paper. The experimental results indicated that the friction properties of clutch facing materials are influenced from the thermal conductivities of the clutch facing material and the counter material. The clutch facing material with the lower thermal conductivity and the fly-wheel material with the higher thermal conductivity showed the low and stable friction coefficient in the range of high sliding speed. This appears to be due to the formation of a film on the surface of the fly-wheel material.

• Tribology and Lubricants
• /
• 제39권2호
• /
• pp.76-80
• /
• 2023

This paper describes an experimental investigation of the effect of cooling flow rate on gas foil thrust bearing (GFTB) performance. In a newly developed GFTB test rig, a non-contact type pneumatic cylinder provides static loads to the test GFTB and a high-speed motor rotates a thrust runner up to the maximum speed of 80 krpm. Force sensor, torque arm connected to another force sensor, and thermocouples measures the applied static load, drag torque, and bearing temperature, respectively, for cooling flow rates of 0, 25, and 50 LPM at static loads of 50, 100, and 150 N. The test GFTB with the outer radius of 31.5 mm has six top foils supported on bump foil structures. During the series of tests, the transient responses of the bearing drag torque and bearing temperature are recorded until the bearing temperature converges with time for each cooling flow rate and static load. The test data show that the converged temperature decreases with increasing cooling flow rate and increases with increasing static load. The drag torque and friction coefficient decrease with increasing cooling flow rate, which may be attributed to the decrease in viscosity and lubricant (air) temperature. These test results suggest that an increase in cooling flow rate improves GFTB performance.

• Journal of Mechanical Science and Technology
• /
• 제17권5호
• /
• pp.668-678
• /
• 2003

For the purpose to facilitate development of high-speed spindle units (SUs) running on rolling bearings, we have developed a beam element model, algorithms, and software for computer analysis of thermal characteristics of SUs. The thermal model incorporates a model of heat generation in rolling bearings, a model of heat transfer from bearings, and models for estimation of temperature and temperature deformations of SU elements. We have carried out experimental test and made quantitative evaluation of the effect of operation conditions on friction and thermal characteristics of the SUs of grinding and turning machines of typical structures. It is found out that the operation conditions make stronger effect on SU temperatures when rpm increases. A comparison between the results of analysis and experiment proves their good mutual correspondence and allows us to recommend application of the models and software developed for design and research of high-speed SUs running on rolling bearings.

• 해양환경안전학회지
• /
• 제18권3호
• /
• pp.273-278
• /
• 2012

선박 구조재료 FRP 재료의 대체 재료로 빠른 선속과 선적량 증가는 물론 재활용이 용이한 Al 선박으로 전환되고 있다. 본 논문에서는 인장실험을 통해 레저선박에 사용되는 5456-H116 합금에 대한 최적의 마찰교반용접 조건에서 프루브 직경의 효과를 기술하였다. 마찰교반용접에서 이송속도, 회전속도를 변수로 5 mm의 프루브 직경을 사용하여, 이송속도가 61 mm/min의 조건에서 가장 우수한 결과를 나타냈다. 프루브 직경 6 mm, 회전속도 170-210 rpm, 이송속도 15 mm/min 에서는 낮은 회전속도로 인하여 불충분한 용접열이 발생하여 거친 표면과 기공이 형성 되었다. 회전속도 500-800 rpm인 경우, 용접부에 칩이 관찰되었으며, 기공은 생기지 않았고, 용접표면은 우수하였으나 1100-2500 rpm에서는 지나친 용접열의 발생으로 많은 칩이 발생하였다. 열에 의한 영향은 용접 배면에서 관찰되었다. 이송속도가 15 mm/min에서 회전속도의 증가하게 되면 마찰이 증가함에 따라 용접열이 발생한다. 기계적 특성은 용접 입열량이 증가할수록 재질의 연화가 가속화되어 저하하였다.

• 한국생산제조학회지
• /
• 제22권4호
• /
• pp.700-707
• /
• 2013

Owing to high oil prices and environmental issues, the automobile industry has conducted considerable research and made large investments to manufacture a high-efficiency automobiles. In the case of automobile wheels in which a lightweight material is used to increase the fuel efficiency a mold is used to increase the production efficiency; however, the use of the molding method for this purpose is very expensive. Therefore an automobile wheel consists of two parts. In this study a two-piece automobile wheel is manufactured by the friction stir welding(FSW) of Al6061-T6 to reduce the manufacturing cost and process complexity. The FSW welding tool geometry and rotational speed, and the feed rate are key factors that significantly affect the weld strength. Therefore tensile tests were conducted on specimens produced using various welding conditions, and the optimal FSW welding conditions were applied to manufacture aluminum wheels. To ensure reliability, prototype aluminum wheels were manufactured and their mechanical reliability and safety were evaluated using a durability test, fatigue durability test, and impact test. Through this study, aluminum wheel production was made possible using the FSW method.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2004년도 추계학술대회 논문집
• /
• pp.375-381
• /
• 2004

Recently, the evolution in production techniques (e.g. high-speed milling) and the complex shapes involved in modem production design has been increasingly popular. The key to the achievement is a drastic improvement of the dynamic behavior of the machine tool axes used in production machinery. The more complex these tool paths the higher the speed and acceleration requirements. But it is very difficult to reach the target for high speed machine tool because of the limitations of servo system and motion control system. However the direct drive design of machine tool axes, which is based on linear motors and which recently appeared on the market, is a viable candidate to meet the ever increasing demands, because of these advantages such as no backlash, less friction, more mechanical simplicity and very higher acceleration and velocity comparing to the traditional system. This paper focused on the performance tests of the high speed horizontal machine tool based on linear motor. Especially, dynamic characteristics were investigated through circular test and circular form machining test is carried out considering many important parameter. Therefore these several experiments is used to be evaluated the model for prediction of circular motion error and circular machined error.

• Tribology and Lubricants
• /
• 제34권6호
• /
• pp.262-269
• /
• 2018

In this work the friction and wear characteristics of the gray cast iron surface processed by broaching method, which is widely used in the machinery industry, were investigated. The broaching process is mainly used for mass production because it has high dimensional accuracy and processing speed, but the defects on surface can be easily generated. In order to improve the tribological characteristics, the approach was to reduce the roughness and hardness of the surface by adding a machining process to the broaching specimen. The secondary machining process using abrasive grains produces low roughness and hardness than broaching because it has high tool accuracy and removes the work hardened surface. The friction coefficient and the wear rate were assessed using a reciprocating-type tribotester to analyze the effects of surface finishing on the tribological properties. The friction tests were conducted under dry and lubricated conditions. The test results showed that the reduction of surface roughness and hardness through secondary machining process in lubricated condition improved the friction and wear characteristics. The reason why the same results did not appear in a dry condition was that wear occurred more rapidly than in lubricated condition. Thus, the positive effect of roughness and hardness of the surface obtained through the secondary machining process was not observed.