• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.803-808
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• 2000

This thesis studied whether friction welding of SPSS, localized torsion bar material could be accomplished or not. And then optimum welding conditions were examined and leaded through tensile, impact, torsion and hardness test after postweld heat treatment of the actual field condition. Obtained results were as follows; Linear relationship was existed between heating time and total upset, and a quadratic equation model could be made between tensile strength and heating time. Optimum welding conditions with fine structure were as follows in case total upset(U)=8.5mm; the number of rotations(n)=2,000 rpm, heating pressure($p_1$)=80MPa, upset pressure($p_2$)=200MPa, heating time($t_1$)=4sec, upset time($t_2$)=3 sec.

• Journal of Biosystems Engineering
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• 제34권2호
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• pp.89-94
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• 2009

Aerial application using an agricultural unmanned helicopter was suggested for an alternative against current pesticide application methods. Centrifugal clutches play important roles in the performance and safety of the helicopter operation. A previous study analyzed and verified the power transfer theory of the guide type centrifugal clutch. Based on the clutch theory, optimal designs of the clutch became possible and feasible using a simulation method. Design criteria of the clutch were the power transfer capacity of 24.66 kW(33.5 PS) at the rated engine speed and the engaging range speed of 3,000${\sim}$3,500 rpm. Various designs were accomplished using the simulation. An optimal clutch was simulated by determining the values of spring constant and mass of friction sector, which were 94,700 N/m and 123.7 g, respectively. The design performed the power capacity of 24.86 kW(33.8 PS) and engagement speed of 3,069 rpm, meeting the design criteria. Using the designed clutch, an efficient transfer of the power would be possible for the unmanned agricultural helicopter.

• International Journal of Automotive Technology
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• 제7권3호
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• pp.369-375
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• 2006

This paper describes a simple proportional and integral control algorithm for a swirl motor controller and its application. The control algorithm may be complicated in order to have desired performance, such as low steady state errors, fast response time, and relatively low overshoot. At the same time, it should be compact so that it can be easily implemented on a low cost microcontroller, which has no floating-point calculation capability and low computing speed. These conflicting requirements are fulfilled by the proposed control algorithm which consists of a gain scheduling proportional controller and an anti-windup integral controller. The mechanical friction, which is caused by gears and a return spring, varies very nonlinearly according to the angular position of the system. This nonlinear static friction is overcome by the proportional controller, which has a two-dimensional look up gain table. It has error axis and angular position axis. The integral controller is designed not only to minimize the steady state error but also to avoid the windup effect, which may be caused by the saturation of a motor driver. The proposed control algorithm is verified by use of a commercial product to prove the feasibility of the algorithm.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.472-472
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• 2009

The safety of cultural properties, medical treatment and electrical communication equipments in a building was hardly considered against the earthquake induced vibration, while the integrity of the building structure has been taken into account through the resistant earthquake design. This paper presents design of a seismic isolation table for both indoor and outdoor electrical communication equipment. First of all, artificial earthquake waves compatible with floor and ground response spectra for electrical communication equipments are generated using previously recorded seismic waves. Two kinds of one-degree-of-freedom seismic isolation table systems: spring-linear damper and spring-friction damper systems are considered and their responses to artificial earthquake waves are simulated. Design parameter study for two seismic isolation tables are performed through simulations and a seismic isolation table for both indoor and outdoor electrical communication equipment is designed considering the simulation results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1530-1535
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• 2003

The automatic load transfer switch (ALTS) typically automatically transfers electrical loads from a normal electrical power source to an emergency electrical power source upon reduction or loss of normal power source voltage. It can also automatically re-transfer the load to the normal power source when the normal voltage has been restored within acceptable limits. The transfer operation of ALTS is accomplished by a spring-driven linkage mechanism. In this paper we build a dynamic model of driving mechanism for ALTS using ADAMS and checked the characteristics of the transfer operation. Finally we performed a detailed design of the driving mechanism through results of analysis and confirmed it to satisfy design requirements.

• Structural Engineering and Mechanics
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• 제6권1호
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• pp.63-76
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• 1998

This paper presents dynamic responses of structures with sliding base which limits the translation of external loads from ground excitation. A discrete element model based on the discontinuous deformation analysis method is proposed to study this sliding boundary problem. The sliding base is simulated using sets of fictitious contact springs along the sliding interface. The set of contact spring is to translate friction force from ground to superstructure. Validity of the proposed model is examined by the closed-form solutions of an idealized mass-spring structural model subjected to harmonic ground excitation. This model is also applied to a problem of a three-story structural model subjected to the ground excitation of 1940 El Centro earthquake. Analyses of both sliding-base and fixed-base conditions are performed as comparisons. This study shows that using this model can simulate the dynamic response of a sliding structure with frictional cut-off quite accurately. Results reveal that lowering the frictional coefficient of the sliding joint will reduce the peak responses. The structure responses in little deformation, but it displaces at the end of excitation.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.1203-1209
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• 2006

One dimensional collision analysis is often used to simulate a train-to-train coupling or collision accident. But there are various numerical modeling techniques utilized for dynamic models of rolling stocks such as a lumped-spring-mass model or a bar-mass model. In rolling stock industries, a lumped-spring-mass model is mainly applied without consideration of bogie attachments separately. In this case, a dynamic stiffness coefficient is introduced to compensate the overestimated car mass effects due to the linkage stiffness of bogies and seats. In this paper, the effects of dynamic stiffness coefficients and wheel-rail friction coefficients were studied by simulating a bar-mass model with bogie attachments separately.

• 한국강구조학회 논문집
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• 제28권4호
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• pp.223-229
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• 2016

이 연구에서는 고무 스프링과 자력마찰을 조합한 스마트 댐퍼의 동적 실험을 수행하여 스마트 댐퍼의 깃발모양 (flag-shaped) 거동을 확인하고자 하였다. 스마트 댐퍼 동적실험을 수행하기 위하여, 네오디뮴 (NdFeB) 자석을 사용하였으며 $50mm{\times}50mm{\times}25mm$ ($B{\times}L{\times}H$)의 크기를 사용하였다. 또한 폴리우레탄 고무를 사용하였으며 길이 80mm 외경 80mm 내경 20mm의 크기의 원주형 고무스프링을 사용하였다. 동적 실험에서 자석의 개수와 진동수를 제어하여 수행하였으며, 자석의 개수는 0, 4, 8, 12개의 순서로 증가하였으며, 이는 자력 마찰력이 증가함을 의미하였다. 진동수는 0.1부터 2.0Hz까지 증가시키면서 진행하였다. 실험의 진행은 고무 스프링이 장착되지 않은 자력마찰 댐퍼의 자력 마찰력 평가 실험, 고무 스프링의 기압축량 평가 실험 및 최종적으로 자력 마찰력과 기압축 고무스프링이 합성된 스마트 댐퍼의 동적 실험 순서로 진행하였다. 실험 결과를 통하여 스마트 댐퍼의 깃발모양 거동을 평가하고 에너지 소산능력, 감쇠비를 평가하여 스마트 댐퍼로서의 성능을 확인하였다.

• 대한기계학회논문집
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• 제9권1호
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• pp.81-90
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• 1985

본 논문에서는 이에 대체하는 방법으로써 전달 매트릭스 방법을 들수 있는데, 선형 진동계 해석에 있어 이 방법의 효용은 많은 논문을 통해 실증된 바이다. 특히 저어널 베어링의 댐핑효과는 크고 또한 운전회전속도에서 선형화된 스프링 및 댐핑계 수들이 수평 및 수직방향으로 연성되어 있어 전달 매트릭스 방법의 적용이 이상적이다. 회전축계의 진동 해석에 있어 낮은 공진회전수와 안정한계회전수, 즉 시스템 댐핑이 영이 되는 점을 규명하는 것이 실제에서 중요하므로 낮은 고유 진동수만을 구하면 되 는데, 이를 위하여 수치해석의 기법을 타 각도로 연구 검토할 필요가 있다.

• Journal of Radiation Protection and Research
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• 제11권1호
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• pp.65-69
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• 1986

Picker C-9 $^{60}Co$원격치료장치에 의한 선량분포의 비대칭을 물팬톰에 의한 측정으로부터 발견하고 비대칭적인 선량분포의 원인이 선원의 비정상적인 'ON' 위치였음을 확인하였다. 선원이 비정상적인 위치에서 정지하게 된 원인이 선원을 'OFF'위치로 되돌리는 태엽의 일부 인접면이 접촉하게되어 마찰의 발생과 증대였음을 확인하였다. 태엽에 윤활유를 쳤을 때 선량분포의 대칭성이 다소 호전되었지만 근본적인 해결책은 태엽을 교체하는 것이다. 예방대책으로는 주기적인 선량분포의 측정에 의한 확인과 보수유지계획에 의한 관리가 수행되어야 할 것이다.