A precise control of the launcher in MLRS(Multiple Launcher Rocket System) is important for a mission completion. During the field operation of the MLRS, a friction noise was heard in the elevation clutch that controls the launcher. It was confirmed that unsteady friction between friction plates and clutch plates has caused the noise in the clutch. Conducting the analysis of drive mechnism in the clutch, there was a possibility of the unsteady friction because of moderated spring constant. Therefore, after performing experiments on the elevation clutch varied with spring constant, it was determined the proper spring constant. Finally, an improvement on the spring constant in the elevation clutch is expected in the future by utilizing the result of this study.

In this study, factors analysis is performed for reducing friction in elevation motion of a large television stand over 50-inch. The first is a pipe type cross-section control for accurate position control of the piston rod. Here it was compared with the pipe type and labyrinth type orifice cross-section. The second study is for specification decision and volume compensation experiment as an apparatus for compensating of the volume of the cylinder is compressed as the volume of piston rod. Consequently, in the orifice cross section study between pipe type and labyrinth type through CAE and experimental consideration, cross section of labyrinth type orifice is preferred for reducing of friction. The result of total consideration in stability problem and performance of volume compensation for specification decision and volume compensation experiment is determined the final speculation of hollow rod φ8×φ4 and riveting system.

In this study, the curvature FSW experiments were performed with the 2 mm thickness of Al 5083-O using by the 5 axis(X/Y/Z/A/C) position control system. For the mechanical test of the butt joints, the tungsten heavy alloy as the tool material without necessary after finishing the heat treatment such as quenching was used. In particular, the insertion depth and the welding speed was changed at the constant rotation speed in order to select the optimum FSW condition. The test results were visually satisfactory for the approximate joint length of 300 mm. Sound joint was formed at the condition of 1.9 mm-1000 rpm-100 mm/min and its tensile strength of joint was the most high almost the same as that of the base material.

In this study, factors analysis is performed for reducing friction in elevation motion of a large television stand over 50-inch. The first is a pipe type cross-section control for accurate position control of the piston rod. Here, it was compared with the pipe type and labyrinth type orifice cross-section. The second study attempted to reduce the frictional force the gas seal lip technology. As the result of the first study, in the orifice cross section study between pipe type and labyrinth type through CAE and experimental consideration, cross section of labyrinth type orifice is preferred for reducing of friction. As the result of the second study, in the gas seal lip technology, the outer-inner diameter of φ20×φ8 in the test result of hollow rod is revealed more proper if the weight of 50 inch television assumed as 30kgf.

In order to improve seismic safety of nuclear power plant (NPP) structures in high seismicity area, seismic isolation system can be adapted. In this study, friction pendulum system (FPS) is used as the seismic isolation system. According to Coulomb‘s friction theory, friction coefficient is constant regardless of bearing pressure and sliding velocity. However, friction coefficient under actual situation can be changed according to bearing pressure, sliding velocity and temperature. Seismic responses of friction pendulum system with constant friction and various velocity-dependent friction are compared. The velocity-dependent friction coefficients of FPS are varied between lowand fast-velocity friction coefficients according to sliding velocity. From the results of seismic analysis of FPS with various cases of friction coefficient, it can be observed that the yield force of FPS becomes larger as the fast-velocity friction coefficient becomes larger. Also, the displacement response of FPS becomes smaller as the fast-velocity coefficient becomes larger.

The new rotary friction damper was developed using several two-nodal rotary frictional components with different clamping forces. Because of these components, the rotary friction damper can be activated by building movements due to lateral forces such as a wind and earthquake. In this paper, various dependency tests such as displacement amplitude, forcing frequency and long term cyclic loading were carried out to evaluate on the structural performance and the multi-slip mechanism of the new damper. Test results show that the multi-slip mechanism is verified and friction coefficients are dependent on displacement amplitute and forcing frequency except long term cyclic loading.

The triboelectric property of a material is important to improve an efficiency of triboelectric generator(TEG) in energy harvesting from an ambient energy. In this study, we have studied the TEG property of a semicon-ducting SnO2 which has yet to be explored so far. As a counter triboelectric material, PET and glass are used. Verticalcontact mode is utilized to evaluate the TEG efficiency. SnO2 thin film is deposited by atomic layer deposition on bareSi wafer for various thicknesses from 5.2 nm to 34.6 nm, where the TEG output is increased from 13.9V to 73.5V. Tri-boelectric series are determined by comparing the polarity of output voltage of 2 samples among SnO2, PET, and glass.In conclusion, SnO2, as an intrinsic n-type material, has the most strong tendency to be positive side to lose the electronand PET has the most strong tendency to be negative side to get the electron, and glass to be between them. Therefore,the SnO2-PET combination shows the highest TEG efficiency.

Various hybrid dampers have been developed as increasing tall buildings in Korea. To minimize the installment space and cost, the new hybrid friction damper was developed using friction components. It is composed of two one-nodal rotary frictional components and a slotted bolted frictional connection. Because of these components, hybrid friction damper can be activated by building movements due to lateral forces such as a wind and earthquake. In this paper, displacement amplitude dependency tests were carried out to evaluate on the structural performance and the multi-slip mechanism of the hybrid damper. Test results show that the multi-slip mechanism is verified and friction coefficients are increasing as displacement amplitudes are increasing.

In this study, to confirm the effect of alloying elements on the phase transformation and conditions of the friction stir process, we processed two materials, SS400 and SM45C steels, by a friction stir process (FSP) under various conditions. We analyzed the mechanical properties and microstructure of the friction stir processed zone of SS400 and SM45C steels processed under 400RPM - 100mm/min conditions. We detected no macro (tunnel defect) or micro (void, micro crack) defects in the specimens. The grain refinement in the specimens occurred by dynamic recrystallization and stirring. The microstructure at the friction stir processed zone of the SS400 specimen consisted of an α-phase. On the other hand, the microstructure at the friction stir processed zone of the SM45 specimen consisted of an α-phase, Fe3C and martensite due to a high cooling rate and high carbon content. Furthermore, the hardness and impact absorption energy of the friction stir processed zone were higher than those of base metals. The hardness and impact absorption energy of FSPed SM45C were higher than that of FSPed SS400. Our results confirmed the effect of alloying elements on the phase transformation and mechanical properties of the friction stir processed zone.

최근 지진의 빈도가 증가하면서 전력 시설물에 대한 피해 역시 심각한 상황이다. 요즘 들어 Hanger, Brace, Snubber와 같이 주요기기들을 연결하는 배관지지 시스템의 중요성이 강조되고 있다. 배관의 손상은 발전소 가동에 전체적인 영향을 미치기 때문에 손상을 주는 요인으로부터 보호할지지 장치가 필요하게 된다. 이러한 장치들은 배관에 작용하는 직․간접적인 진동과 충격을 저감시키는 역할을 하기 때문에 배관의 손상을 방지할 수 있다. 본 논문에서는 마찰진자 원리를 이용한 기계식 댐퍼를 개발하고 특성시험을 통해 장치 성능을 검증한 내용을 기술하였다. 또한 자체 개발한 설계 프로그램을 통해 예상된 해석값과 시험값을 비교분석하였고 결과적으로 설계의 신뢰성을 향상시켰다.

Pneumatic cylinder actuators are significantly utilized for industry automatic systems in the fields of mechanical applications. We propose a novel control method for pneumatic cylinder actuator systems including stochastic friction dynamics. The proposed control mechanism is linearly composed of nominal control and auxiliary control variables. The former is designed from linear system model without friction terms by using a previous linear system theory and the latter is constructed as a function of friction estimation which is carried out by a well-known least square algorithm for reducing the control error due to random friction dynamics. We accomplish numerical simulation to demonstrate reliability of the proposed control method and conduct a comparative study to improve its superiority.

In this study, the cold rolled DP590 FSW joints were obtained by the position control type of the FSW machine and examined. The FSW weldability was investigated using the Si3N4 tool specially made by Cold Isostatic Press (CIP). Defect-free joints were formed at 180-300 mm/min at 800 rpm. However, a groove-like defect was observed along the joint line of the advancing side due to the insufficient material flow. In addition, the life of the Si3N4 tool was compared to that of the polycrystalline cubic boron nitride (PCBN) tool for the durability. The SI3N4 tool that was broken in which tool reached a length of 5 m and around half of the performance level of the PCBN tool.

The adoption of scroll type air compressor is gradually increased in the automotive/residential air-conditioner and clean air compressor, and the most of critical components of the scroll are made of aluminum to reduce the friction and weight. Many studies for the surface treatment of the aluminum have been performed to reduce the friction between the components. In the preceding research, we suggested the most appropriate combination of the solid lubricant. In this study, we coated the part of fixed or orbiting scroll wrap with the solid lubricant that suggested in the preceding research, and then have performed analysis of performance characteristics for the part. As a result, we could obtain the 7.66μm of the coating thickness, Ra 0.8μm of the surface roughness and 0.088 of the friction coefficient. These represent the satisfactory capability of the suggested solid lubricant for the scroll type air compressor.

In this paper, the 5 joint toggle link of a injection molding machine is analyzed. Considering toggle link kinematics and frictions at the pin joints, clamping forces for each cross head position are calculated. The maximum clamping force and the install position of a tail-stock are determined by the stiffness of links, plates and tie-bar. The kinematic results of a finite element analysis considering friction and stiffness are compared with measured results

PURPOSES: This study is to predict the Sound Pressure Level(SPL) obtained from the Noble Close ProXimity(NCPX) method by using the Extended Kalman Filter Algorithm employing the taylor series and Linear Regression Analysis based on the least square method. The objective of utilizing EKF Algorithm is to consider stochastically the effect of error because the Regression analysis is not the method for the statical approach. METHODS: For measuring the friction noise between the surface and vehicle’s tire, NCPX method was used. With NCPX method, SPL can be obtained using the frequency analysis such as Discrete Fourier Transform(DFT), Fast Fourier Transform(FFT) and Constant Percentage Bandwidth(CPB) Analysis. In this research, CPB analysis was only conducted for deriving A-weighted SPL from the sound power level in terms of frequencies. EKF Algorithm and Regression analysis were performed for estimating the SPL regarding the vehicle velocities. RESULTS : The study has shown that the results related to the coefficient of determination and RMSE from EKF Algorithm have been improved by comparing to Regression analysis. CONCLUSIONS : The more the vehicle is fast, the more the SPL must be high. But in the results of EKF Algorithm, SPLs are irregular. The reason of that is the EKF algorithm can be reflected by the error covariance from the measurements.

본 연구에서는 1톤 용량의 배아미를 생산할 수 있는 중형 배아미 생산시스템의 설계, 개발 그리고 평가를 목표로 하였다. 개발된 배아정미기는 연삭과 마찰의 혼합방식으로 제조되었다. 배아미 생산시스템의 형태는 2대의 직렬 입형 배아정미기로 구성하였으며, 배아부착율, 백도, 싸래기율을 조사하였다. 또한, 연삭식, 마찰식, 연삭과 마찰의 혼합방식에 따라서 각각 배아미의 배아부착율, 백도, 싸래기율도 조사하였다. 본 시스템은 1단계 배아정미기에서는 연삭과 마찰의 혼합방식으로 미강을 깍은 후, 2번째 배아 정미기에서는 쌀의 배아가 떨어지지 않도록 미세 미강을 제거하면서 쌀의 백도를 높이도록 개발되었다. 배아정미기 시작기에서는 축 롤러 부분의 금강석 연삭돌을 3개, 스크린부에는 6개의 연삭돌을 설치하였고, 각각의 정미기 롤러축의 회전속도는 960 rpm과 780 rpm으로 하여 배아 부착율과 백도를 높였다. 그 결과, 약 20%의 배아 부착율을 증가시킬 수 있었다. 본 연구에서는 다음과 같이 요약할 수 있다. 첫째, 배아부착율은 현미의 함수율과 밀접한 관계가 있었다. 함수율 15.2±0.1%인 시료로 실험한 결과, 투입량 약 600 kg일 때 배아부착률은 약 70%를 나타내었다. 둘째, 배아미의 백도는 정미기 롤러축의 회전속도 960 rpm 과 780 rpm 조건으로 운전하였을 때 각각 35, 37 백도로 향상시킬 수 있었다. 셋째, 싸래기율은 본 시스템에서 1% 미만으로 나타냈다. 본 연구에서 개발된 연식마찰식 배아정미기를 평가해본 결과 배아부착율, 백도, 싸래기율을 효과적으로 개선할 수 있었고 30%의 에너지 이용을 절감할 수 있었다.

The friction and wear characteristics of the rubber matrix composites filled with nano sized silica particles were investigated at ambient temperature by pin-on-disc friction test. The volume fraction of silica particles was 19%. The cumulative wear volume and wear rate of these materials on counterpart roughness were determined experimentally. The major failure mechanisms were lapping layers, deformation of matrix, ploughing, debonding of particles, fracture of particles and microcracking by scanning electric microscopy photograph of the tested surface. The cumulative wear volume showed a tendency to increase with increase of sliding distance. The wear rate of these composites tested indicated low value as increasing the sliding distance.

The friction damper can be used for improving the seismic resistance of existing buildings. The damper is often installed in bracing members. The energy dissipation capacity of the damping systems depends on the type of the structure, the configuration of the bracing members, and the property of dampers. In Korea, there are numerous low- to mid-rise reinforced concrete moment frames that were constructed considering only gravity loads. Those frames may be vulnerable for future earthquakes. To resolve the problem, this study developed a toggle bracing system with a high density friction damper. To investigate the improvement of reinforced concrete frames after retrofit using the developed damped system, experimental tests were conducted on frame specimens with and without the damped system. The results showed that the maximum strength, initial stiffness and energy dissipation capacity of the framed with the damped system were much larger than those of the frame without the damped system.

Friction welding in dissimilar materials is widely applied in various engineering fields such as automobiles, rolling stocks, machine tools. Since interface edges of Friction-welded materials have stress singularity by differences of mechanical properties and temperature changes, it is necessary to assess stress singularity with the variation of flash shape and length. In this paper, the influences which the flashes created by friction welding concern to the stress singularity at interface edges are investigated. Through stress analysis by the BEM and static experiments, the influences were studied quantitatively, the stress singularity greatly depends on the shape of the flash and its size.