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이득원(Deuk-Won Lee),이철희(Chul-Hee Lee),김철현(Cheol-Hyun Kim),조원오(Won-Oh Cho) 한국트라이볼로지학회 2011 한국윤활학회지(윤활학회지) Vol.27 No.4
In this study, friction characteristics using elastomeric actuator with Magneto-rheological (MR) materials are identified. Typically, Magneto-rheological materials are divided into two groups by MR fluid in fluid state and MR elastomer in solid state like rubber. The stiffness characteristics of Magneto-rheological material can be changed as magnetic field is applied. MR fluid has been applied to various industry fields such as to brake, clutch, damper, engine mount and etc. However, MR fluid has been used under the sealed condition to prevent leaking issues. In order to overcome these problems, MR elastomer that has same property as MR fluid has been developed and studied. MR elastomer mainly consists of polymer material such as natural rubber or silicon rubber with particles that can be polarized with magnetic field. And it is called as a smart material since its stiffness and damping characteristics can be changed. In this study, MR elastomer is produced and pin-on-disc tests are carried out to identify the friction characteristics of the material. Several test conditions are applied to evaluate the feasibility to use as a smart actuator in the field of vibration control.
이득원(Deuk-Won Lee),이철희(Chul-Hee Lee),윤혁채(Hyuk-Chae Yun),조원오(Won-Oh Cho),김교헌(Gyo-Heon Kim),박정률(Jeong-Ryul Park) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
Generated axial force (GAF) due to internal friction of driveshaft joint is one of the causes generating the shudder of vehicle. It also causes vibration problem on steering wheels of vehicles during idling. In this study, automated test machine is developed to precisely measure the GAF caused by internal friction in constant velocity joints. As the developed machine can control the temperature of joint, loading torque, angle of rotation and joint angles, actual vehicle driving condition can be applied. In order to validate the developed constant velocity joint tester, GAF is compared by using different types of grease in tripod joints. Also GAF is measured for both on new and used constant velocity joints to be compared and analyzed. The test result shows the repeatability and consistency of the test machine in terms of the different test conditions. By using the constant velocity joint tester, friction performance of the joint can be evaluated by proposing the best constant velocity joints as well as greases generating lowest GAF.
연성룡(Chenglong Lian),이득원(Deuk-Won Lee),이광희(Kwang-Hee Lee),이철희(Chul-Hee Lee),김철현(Cheol-Hyun Kim),조원오(Won-Oh Cho) 한국트라이볼로지학회 2012 한국윤활학회지(윤활학회지) Vol.28 No.3
In this study, application feasibility of Magneto-rheological elastomer to friction control is investigated to identify the reciprocating friction and wear performance in applied magnetic field. Friction and wear of MR elastomerare measured by reciprocating tester by controlling the magnetic field. In the case of applied magnetic field, the coefficient of friction increases as both load and velocity increase. For the case of no magnetic field, the value of coefficient of friction hardly changes during the test. The amount of destruction is measured through cross section images of MR elastomer after tests. The depths of destruction are compared for MR elastomer with or without magnetic field. The results show that the depth of destruction of MR elastomer with magnetic field is deeper than without magnetic field. Based on the obtained results, optimal braking and driving performance can be achieved by controlling the coefficient of friction of MR elastomer, which can be applied to various industrial applications such as driving systems of automobiles and robots.
이광희(Kwang-Hee Lee),이득원(Deuk-Won Lee),이철희(Chul-Hee Lee),윤혁채(Hyuk-Chae Yun),조원오(Won-Oh Cho) 한국트라이볼로지학회 2012 한국윤활학회지(윤활학회지) Vol.28 No.6
Generated Axial Force (GAF) due to internal friction at Constant Velocity (CV) joints is one of the causes generating vibration problems such as shudder in vehicle. In this study, the GAF measuring tester is developed to precisely measure GAF caused by internal friction in CV joints. As the developed tester can control temperature at joint, driving torque, angle of rotation and joint angles, actual driving conditions such as sudden acceleration can be applied to the machine. GAFs are measured and compared by using different types of grease in tripod housing. Also GAFs are measured for both new and used CV joints to be compared and analyzed. The test result shows the repeatability and consistency of the tester in terms of the different test conditions. By using the developed CV joint tester, friction performance of the joint can be evaluated by proposing the best CV joints as well as greases generating the lowest GAF.
정근우(KeunWoo Chung),김영운(Young-Wun Kim),임도혁(Do Hyuk Im),조원오(Won Oh Cho) 한국트라이볼로지학회 2009 한국트라이볼로지학회 학술대회 Vol.2009 No.6
Room temperature ionic liquids (RTILs) have been attracting significant and growing interest as the lubricants, owing to their intrinsic useful properties such as good thermal stability, negligible vapor pressure, good low temperature properties, good flame retardant properties. In this study, several imidazolium-based ionic liquids, 3-alkyl-1-alkylimidazolium tetrafluoroborates, hexafluorophosphonates, trifluoromethane sulfonates, and bis(trifluoromethanesulfoimide), were synthesized. The physical properties of synthetic RTILs such as kinematic viscosity, RI, thermal properties were evaluated and their tribological behaviors of 4-ball WSD and friction properties as the lubricants were evaluated.
박정헌(Park, Jeong-Heon),이철희(Lee, Chul-Hee),김철현(Kim, Cheol-Hyun),조원오(Cho, Won-Oh) 한국소음진동공학회 2011 한국소음진동공학회 논문집 Vol.21 No.8
This paper presents vibration characteristics of magnetorheological(MR) elastomer, whose elastic modulus are controllable by applied magnetic field. By using this property, the material can be applied to vibration absorber, so that the stiffness of the absorber can be changed and actively controlled according to the magnetic flux density. However, the various performances of MR elastomer depends on different polarized direction of particles by applied magnetic field and dimension during the manufacturing process. In this paper, in order to obtain the optimal characteristics of MR elastomer, MR elastomers with different types and dimensions are prepared for a series tests. Using this test setup, extent of natural frequency shifted against magnetic field at various excitation frequencies can be measured. Specimens are prepared with 3 types, as cylinder samples exposed to magnetic field vertically, horizontally and unexposed during cure, respectively. Also, a set of design variables are considered to produce MR elastomers. Through the modal tests of mass structure with MR elastomer, the optimal design as well as the polarization direction of MR elastomer is obtained among the various dimensions and 3 directional types of MR elastomers.
박정헌(Park, Jeong-Heon),홍성근(Hong, Sung-Geun),이광희(Lee, Kwang-Hee),이철희(Lee, Chul-Hee),김철현(Kim, Cheol-Hyun),조원오(Cho, Won-Oh) 한국소음진동공학회 2012 한국소음진동공학회 논문집 Vol.22 No.6
This paper presents a solution of the vibration reduction in the hollow shafts by using magentorehological( MR) elastomer. Proposed active damping structure is built by embedding the MR elastomers whose elastic modulus is controllable by an applied magnetic field. MR elastomers consist of synthetic rubber filled with micron-sized magnetizable particles. For reduction of vibration, dynamic damper of hollow shaft is designed by using MR elastomer and equipped in the hollow shaft for the application to drive shaft. Experiment results are shown through the experiments to confirm the effect of MR elastomer dynamic damper for vibration reduction. Thus, the designed damping structure can be applied to vibration absorber used in drive shafts as well as the propeller shafts.