• Tribology and Lubricants
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• v.25 no.1
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• pp.7-12
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• 2009

Coating brittle intermetallic compounds on metal can enlarge the range of their use. It is found that intermetallic compound coating layers made by only combustion synthesis in an electric furnace have porous multi-phase structures containing several intermediate phases, even though the coating layers show good wear resistance. In this study, dense $Ni_{3}Al$ single phase layer corresponding to the initial composition of the mixed powder is coated on two different ferrous materials by the diffusing treatment after combustion synthesis. After- ward, sliding wear behaviors of the coating layer are evaluated in comparison with that of the coating layer with porous multi-phase structure made by only combustion synthesis. As a result, the wear properties of the coating layer composed of dense $Ni_{3}Al$ single phase are considerably improved at the range of low sliding speed com- pared with that of the coating layer with porous multi-phase structure, particularly in the running-in wear region. This is attributed to the fact that wear of the coating layer is progressed by shearing as a sequence of adhesion, not by occurring of pitting on the worn surface due to having dense structure without pores.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.483-488
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• 2003

Frictional heating in brakes causes thermoelastic distortion of the contacting bodies and hence affects the contact pressure distribution. The resulting thermo-mechanical coupling can cause thermoelastic instability (TEI) if the sliding speed is sufficiently high, leading to non-uniform heating called hot spots and low frequency vibration known as hot judder. The vibration of brakes to the known phenomenon of frictionally-excited thermoelastic instability is estimated studying the interface temperature and pressure evolution with time. A simple model has been considered where a layer with half-thickness ${\alpha}$ slides with speed V between two half-planes which are rigid and non-conducting. The advantage of this properly simple model permits us to deduce analytically the critical conditions for the onset of instability, which is the relation between the critical speed and the growth rate of the interface temperature and pressure. Symmetrical component of pressure and temperature distribution at the layer interfaces can be more unstable than antisymmetrical component. As the thickness ${\alpha}$ reduces, the system becomes more apt to thermoelastic instability. Moreover, the evolution of the system beyond the critical conditions has shown that even if low frequency perturbations are associated with low critical speed, it might be less critical than high frequency perturbations if the working sliding speed is much larger than the actual critical speed of the system.

• Journal of the Korean institute of surface engineering
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• v.25 no.3
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• pp.107-116
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• 1992

The optimum thickness of Pd-Ni plated layers used as an electrical contact film was investigated by evaluating mechanical, thermal and environmental characteristics. The variations of morphologies and chemical compositions were studied by using SEM, EDS and ESCA. As a result of wear test, the wear resistance behavior of the gold plated layers was not changed with the sliding velocity changes. The palladium-nickel plated layer showed better wear resistance than the gold plated layer at low sliding velocity, but it showed poor wear resistance at high sliding velocity. Under the thermal condition of $400^{\circ}C$ in air, the gold thickness of $2\mu\textrm{m}$ without underplate on phosphorous bronze formed copper oxide on the surface layer by rapid diffusion of copper whereas the gold thickness of $0.8\mu\textrm{m}$ deposited on nickel and palladium-nickel underplate was stable at $400^{\circ}C$. Under the sulfur dioxide environments, the gold thickness of $0.3\mu\textrm{m}$ deposited on the nickel thickness of$ 3\mu\textrm{m}$ and the palladium-nickel thickness of $2\mu\textrm{m}$ underplate was more corrosion-resistant than the gold thickness of $2\mu\textrm{m}$ without underplate on phosphorous bronze. Under the nitric acid vapor environment, corrosion resistance of the gold film was superior to an equivalent thickness of the palladium-nickel film.

• Korean Journal of Materials Research
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• v.16 no.12
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• pp.766-770
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• 2006

The frictional behavior of oxide films on top of the plasma nitrocarburized compound layers was investigated in terms of post-oxidation treatment temperatures. The post-oxidation treatment at both temperatures($400^{\circ}C,\;500^{\circ}C$) produced magnetite($Fe_3O_4$) films which led to a significant enhancement in corrosion resistance. However, this process did not result in any improvement in frictional behavior of the nitrocarburized surface. The wear mechanisms were governed predominantly by the abrasive action of the slider on the surface irrespective of the counterface material(SiC and Bearing steel). When the specimen was sliding against a SiC counterface, the oxide films were destroyed during the early stage of the sliding process and the wear debris of the oxide film at the sliding track had a great influence on the friction coefficient. On the other hand, when sliding against a bearing steel counterface, the slider was mainly worn out due to the much higher hardness of the surface hardened layer. The fluctuation of the friction coefficient of $400^{\circ}C$-oxidized/ nitrocarburized specimen is much severer than that of $500^{\circ}C$ specimen, due to the less amount of wear debris.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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• pp.357-364
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• 2002

A new chattering free sliding made control is proposed for robot manipulators. The control input is derived from the reaching law and the Lyapunov stability criteria, which is only composed of continuous terms. It has a chattering free characteristics and a concise farm. In implementing procedures, no change of equations is needed. Thus, it does not degrade the original merits of the sliding mode control. And it is applied to a 2-link SCARA robot manipulator. It is shown that the proposed control has good trajectory tracking performance compared with the PD control and the conventional sliding mode control which uses the boundary layer concept.

• Structural Engineering and Mechanics
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• v.26 no.4
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• pp.377-392
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• 2007

A discrete sliding mode control (SMC) method based on hybrid model of neural network and nominal model is proposed to reduce the vibration of flexible structures, which is a robust active controller developed by using a sliding manifold approach. Since the thick boundary layer will reduce the virtue of SMC, the multilayer feed-forward neural network is adopted to model the uncertainty part. The neural network is trained by Levenberg-Marquardt backpropagation. The design objective of the sliding mode surface is based on the quadratic optimal cost function. In course of running, the input signal of SMC come from the hybrid model of the nominal model and the neural network. The simulation shows that the proposed control scheme is very effective for large uncertainty systems.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.253-256
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• 1996

In this paper, A new time-varying sliding surface design using eigenvalue locus is proposed to achieve fast and robust in a class of high-order uncertain dynamic system. A moving sliding surface(MSS) was proposed earlier for the second-order variable structure control systems(VSCS). This methodology led to fast and robust control responses of the second-order VSCS. However, the moving algorithm of the MSS was too complicated to be employed the high-order VSCS. To resolve this problem, we propose a new moving algorithm that switching surface moves such that the eigenvalues of equivalent system in the sliding mode have a predetermined locus. Using the proposed surface fast and robust behaviors are accomplished. The problem of chattering can be eliminated by using a boundary layer of switching surface. The efficiency of proposed algorithm is illustrated by an application to four-order workbench.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1036-1041
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• 2008

In order to analysis the reason of sliding failure in embankment slope under construction in soft soil area, a model section located in Gimhae Region in Gyeongsangnam-Do, where the sliding failure had been occurred during embankment works in soft soil area, had been selected. This area had been firstly treated with the Pack Drain Method, and additional embankment works of 9.7 meters out of total 14 meters in thickness had been under construction. The results of analysis showed that the reason of sliding failure were overspeed in embankment construction and the overestimation of design factors in calculating strength of each layer of embankment and poor management and inaccuracy reading of measurement devices.

• Transactions on Control, Automation and Systems Engineering
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• v.3 no.1
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• pp.15-20
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• 2001

In this paper, adaptive algorithms on the sliding model control for robust tracking control of robust manipulators are presented. The presented algorithms use adaption laws for tuning both the sliding mode gain and the thickness of the boundary layer to reject a disconitnuous control input, and to improve the tracking performance. It is shown that the robustness of the developed adaptive algorithms are guaranteed by the sliding mode control law and that the algorithms are globally convergent in the presence of disturbances and modeling uncertainties. Computer simulations are performed for a two-link manipulator, and the results show good properties of the proposed adaptive algorithms under large mainpulator parameter uncertainties and disturbances.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.7
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• pp.578-583
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• 2001

The bushing for high voltage and large and power should endure weight of itself and force of pushing from contact with circuit breaker. Like this, epoxy mold bushing has to be strong without fault. However, the external circumstances and internal factors was caused by partial discharge, flashover and dielectric breakdown. Therefore, to remove external factor of defect and to prevent the internal cracks and cavity generated from the contraction on interface of Cu-Epoxy, we should form semi-conductive layer on Cu bar by carbon. Then, the PD properties and the insulation qualities of epoxy mold type bushing was able to improved by roles of cushions for the direction of diameter and by effects fo natural sliding like as separated from conductor for the direction of length. So, in this work, we could prove the method of semi-conductive layer in making the long conductor.