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Air Bearing Surface에 대한 Slider의 동적 거동에 관한 연구
김영환(Younghwan Kim),임윤철(Yoonchul Rhim) 한국트라이볼로지학회 2006 한국트라이볼로지학회 학술대회 Vol.2006 No.6
A load/unload(L/UL) system has been applied not only in portable and removable drives but also in desktop and servo drives due to its advantages such as larger data zone and lower power consumption. At L/UL system, contact or collision between slider and disk is an important issue for the stable performance of the system as an air bearing surface (ABS). Also, the curvature should be considered because of its effect on the rolling characteristics. In this paper, the dynamic behavior of a slider during loading process is investigated theoretically. The numerical steady states results are compared with experimental results of Center for Information Storage Devise (CISD). The FEM was used to solve the coupled compressible modified Reynolds equation and the dynamic equation for three-degree-of-freedom (3-D.O.F) slider model with the air bearing stiffness and damping. Also, contact or collision between disk and slider was taken into consideration. The results show the dynamic behavior of the slider during loading process according to initial flying height, disk rpm, skew angle, pitch static attitude (PSA) and roll static attitude (RSA).
마그네틱 베어링을 이용한 고속 회전체용 비접촉식 실 시험기의 설계와 실의 누설 특성 및 동특성 규명
안상규(SangKyu Ahn),김승종(SeongJong Kim),이종민(JongMin Lee),이용복(YongBok Lee),임윤철(YoonChul Rhim) 한국트라이볼로지학회 2007 한국트라이볼로지학회 학술대회 Vol.2007 No.11
Leakage and dynamic characteristics of a non-contact annular seal are important design parameters due to rotational stability of turbo machinery. Although research on a non-contact annular seal has been performed, there exist complicated problems to extract dynamic coefficients from rotating machinery. In this paper seal leakage were derived from a theoretical analysis considering I/O pressures and rotational speeds. In order to theoretically obtain stiffness and damping coefficients, system linearize modeling was carried out. An experimental apparatus using an AMB (Active Magnetic Bearing) system as well as a novel method of system identification was then proposed and described. The proposed AMB system consisting of an exciter and an I/O signal measuring device plays a critical role in levitating and setting dynamic positioning of the rotor without mechanical contacts. Eventually experimental and analytical results were compared each other, and good agreements were obtained.
리니어 압축기에서 그루브 형상 변화에 따른 피스톤의 동특성 해석
노상완(Sangwan Noh),오원식(Wonsik Oh),박경배(Kyeongbae Park),임윤철(Yoonchul Rhim) 한국트라이볼로지학회 2015 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.31 No.5
It is possible to prevent a piston from contacting the cylinder by changing the shape of the piston or by applying micro-textures, such as micro-grooves or micro-holes, over the piston surface. Usually, the minimum radial clearance reaches its minimum value at the beginning of the suction stroke because the pressure around the piston is low and almost axisymmetric such that the net pressure force on the piston is not sufficiently high to support the piston from touching the cylinder. In this study, we apply a series of saw-tooth-shaped grooves on the piston surface, and numerically investigate the effects of groove depth, groove angle, and the number of grooves with radial clearance variations using a finite difference method. We conduct a dynamic analysis of the piston for various changes in groove geometries to obtain the minimum radial clearance variation for the entire compression cycle. The minimum radial clearance increases while friction loss decreases when we apply the series of saw-tooth-shaped grooves on the piston. In addition, we analyze the impact of the change in the groove shape variable due to changes in radial clearance. Leakage variations are relevant to radial clearance, but have almost no effect on the groove parameters.