• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.2
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• pp.399-406
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• 1990

This paper is studied to know corrosive wear mechanism of STS304 steel on atmospherical temperature against mating material as the same. The corrosive test was carried out by rubbing the annular surface of two test pieces in distilled water and NaCl aqueous solution. The corrosive wear mechanism was investigated by S.E.M. The experimental results show that there is one Lcr transferring from severe wear to mild wear on change of NaCl concentration and atmospherical temperature, and which is the other still remaining in server wear state. It was found that the critical sliding distance Lcr shorten with increasing NaCl concentration but it is longer with ascending atmospherical temperature and the mild wear state still continues under the condition of high generation rate and elimination rate of the corrosive product. Considering upon the result, the model of corrosive wear mechanism is proposed.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.04a
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• pp.515-528
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• 1995

Slips and falls are the major causes of the pedestrian injuries in the industry and the general community throughout the world. With the awareness of these problems, the friction coefficients of the interface between floorings and footwear have been measured for the evaluation of slip resistant properties. During this measurement process, the surface texture has been shown to be substantially effective to the friction mechanism between shoe heels and floor surfaces under various types of walking environment. Roughness, either of the floor surface or shoe heels, provides the necessary drainage spaces. This roughness can be designed into the shoe heel but this is inadequate in some cases, especially a wear. Therefore, it is essential that the proper roughness for the floor surface coverings should be provided. The phenomena that observed at the interface between a sliding elastomer and a rigid contaminated floor surface are very diverse and combined mechanisms. Besides, the real surface geometry is quite complicate and the characteristics of both mating surfaces are continuously changing in the process of running-in so that a finite number of surface parameters can not provide a proper description of the complex and peculiar shoe - floor contact sliding mechanism. It is hypothesised that the interface topography changes are mainly occurred in the shoe heel surfaces, because the general property of the shoe is soft in the face of hardness compared with the floor materials This point can be idealized as sliding of a soft shoe heel over an array of wedge-shaped hard asperities of floor surface. Therefore, it is considered that a modelling for shoe - floor contact sliding mechanism is mainly depended upon the surface topography of the floor counterforce. With the model development, several surface parameters were measured and tested to choose the best describing surface parameters. As the result, the asperity peak density (APD) of the floor surface was developed as one of the best describing parameters to explain the ambiguous shoe - floor interface friction mechanism. It is concluded that the floor surface should be continuously monitored with the suitable surface parameters and kept the proper level of roughness to maintain the footwear slip resistance. This result can be applied to the initial stage of design for the floor coverings.

• Tribology and Lubricants
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• v.11 no.5
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• pp.26-30
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• 1995

Sliding experiments have been conducted on alumina and silicon carbide ceramics. Wear and friction data of both materials indicate that wear proceeds in two distinct stages. The wear occurs by a relatively mild plastic-grooving process in the initial stage, but eventually gives way to a severe grain pull-out process after a defined period of sliding test. The datails of the transition mechanism are presented. The effects of grain size and second phase particle on the wear transition are also presented.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.1
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• pp.123-129
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• 2012

Recently, interests on cleaning robots workable in pipes (termed as in-pipe cleaning robot) are increasing because Garbage Automatic Collection Facilities (i.e, GACF) are widely being installed in Seoul metropolitan area of Korea. So far research on in-pipe robot has been focused on inspection rather than cleaning. In GACF, when garbage is moving, the impurities which are stuck to the inner face of the pipe are removed (diameter: 300 mm or 400 mm). Thus, in this paper, by using TRIZ (Inventive Theory of Problem Solving in Russian abbreviation), an in-pipe cleaning robot of GACF with the 6-link sliding mechanism will be proposed, which can be adjusted to fit into the inner face of pipe using pneumatic pressure(not spring). The proposed in-pipe cleaning robot for GACF can have forward/backward movement itself as well as rotation of brush in cleaning. The robot body should have the limited size suitable for the smaller pipe with diameter of 300 mm. In addition, for the pipe with diameter of 400 mm, the links of robot should stretch to fit into the diameter of the pipe by using the sliding mechanism. Based on the conceptual design using TRIZ, we will set up the initial design of the robot in collaboration with a field engineer of Robot Valley, Inc. in Korea. For the optimal design of in-pipe cleaning robot, the maximum impulsive force of collision between the robot and the inner face of pipe is simulated by using RecurDyn(R) when the link of sliding mechanism is stretched to fit into the 400 mm diameter of the pipe. The stresses exerted on the 6 links of sliding mechanism by the maximum impulsive force will be simulated by using ANSYS$^{(R)}$ Workbench based on the Design Of Experiment(in short DOE). Finally the optimal dimensions including thicknesses of 4 links will be decided in order to have the best safety factor as 2 in this paper as well as having the minimum mass of 4 links. It will be verified that the optimal design of 4 links has the best safety factor close to 2 as well as having the minimum mass of 4 links, compared with the initial design performed by the expert of Robot Valley, Inc. In addition, the prototype of in-pipe cleaning robot will be stated with further research.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.203-208
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• 1999

Friction and wear test have been performed on nylon, polyacetal, and PTFE(polytetrafluoroethylene), in reciprocating dry sliding conditions against a steel disc. According to the results, polyacetal show lowest wear rates and PTFE was found to exhibit lowest friction coefficient. The prominent wear mechanism found were adhesion and abrasion.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.6
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• pp.871-883
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• 1997

Kinetodynamics of a cam driving slider mechanism consists of kinematic analysis and force analysis. The kinematic analysis is to determine the kinematic characteristics of a cam driving mechanism and a slider mechanism. The force analysis is to determine the joint forces of links, the contact forces of the cam and follower, and the driving torque of a main shaft. This paper proposes a close loop method and a tangent substitution method to formulate the relationships of kinematic chains and to calculate the displacement, velocity and acceleration of the cam driving slider mechanism. Also, and instant velocity center method is proposed to determine the cam shape from the geometric relationships of the cam and the roller follower. For dynamic analysis, the contact force and the driving torque of the cam driving slider mechanism are calculated from the required sliding forces, sliding motion and weight of the slider.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1619-1629
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• 1995

The Al/Al$_{2}$O$_{3}$ SiC and Al/Al$_{2}$O$_{3}$/C hybrid metal matrix composites (MMCs) were fabricated by squeeze infiltration method. Uniform distribution of reinforcements were found in the microstructure of metal matrix composites. Mechanical tests were carried out under various test conditions to clearly identify mechanical behavior of MMCs, and the wear mechanism of Al/Al$_{2}$O$_{3}$/(SiC or C) hybrid metal matrix composites were investigated. The tensile strength and hardness of hybrid composites was resulted in increasing compared with those of the unreinforced matrix alloy. Wear resistance was strongly dependent upon kinds of fiber, volume fraction and sliding speed. The wear resistance of metal matrix composites was remarkably improved by the addition of reinforcements. Especially, the wear resistance of the hybrid composites of carbon fibers was more effective than in the composites reinforced with alumina and SiC whiskers of reinforcements. This was due to the effect of carbon fiber on the solid lubrication. Wear mechanisms of hybrid composites were suggested from wear surface analyses. The major wear mechanism of hybrid composites was the abrasive wear at low to intermediate sliding speed, and the melting wear at intermediate to high sliding speed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.45-46
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• 2006

In this paper, a dual stage servo mechanism has been developed for image tracking system to improve transient control performances such as small rise time, small overshoot, small settling time, etc. A secondary stage, a platform, actuated by a pair of electro-magnets is mounted on a conventional elevation gimbal. In this mechanism, the gimbal provides large range but slow motion and the platform provides small range but fast positioning. A sliding mode control is applied to the platform positioning to attain robust performances and stability in the presence of the disturbance related to dynamic coupling of the gimbal and the platform. Results from experiments illustrate that the suggested dual stage mechanism controlled by the sliding mode control is effective in improving transient responses and attenuating the disturbance related with dynamic coupling.

• Journal of Welding and Joining
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• v.11 no.4
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• pp.91-102
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• 1993

The plasma sprayed $Cr_3C_2$-NiCr coatings are widely used as wear-resistant and corrosion-resistant materials. The mechanical and wear properties of the plasma sprayed $Cr_3C_2$-NiCr coating on steel plate were examined in this study. The pore in the coatings could be classified into two types, the one is the intrinsic pore originated from the spraying powder, the other is the extrinsic pore formed during spraying. During the tensile adhesion test, the fracture occured at the interface of top coating and bond coating. It is though that the compressive residual stress increases with the increase of the top coating thickness. From the wear test, it was found that the wear rate increased with the increase of the sliding velocity regardless of the temperature. It is thought that the fracture toughness reduces with the increase of the sliding velocity at $30^{\circ}C$ and that the adhesion amount increases with the increase of the sliding velocity at $400^{\circ}C$ It is concluded that the wear mechanism at $30^{\circ}C$ is the fracture and pull-out of the carbide particles due to the fatigue on sliding surface, while the wear mechanism at $400^{\circ}C$ is the adhesion of the smeared layer formed during wear process.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.12
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• pp.38-44
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• 2002

A walking training robot is proposed to provide stable and comfortable walking supports by reducing body weight load partially and a force control of an arm of walking training robot using sliding mode controller is also proposed. The current gait training apparatus in hospital are ineffective for the difficulty in keeping constant unloading level and for the constraint of patients' free walking. The proposed walking training robot effectively unloads body weight during walking. The walking training robot consists of an unloading manipulator and a mobile platform. The manipulator driven by an electro-mechanical linear mechanism unloads body weight in various levels. The mobile platform is wheel type, which allows patients to walt freely. The developed unloading system has advantages such as low noise level, lightweight, low manufacturing cost and low power consumption. A system model fur the manipulator is established using Lagrange's equation. To unload the weight of the patients, sliding mode control with p-control is adopted. Both control responses with a weight and human walking control responses are analyzed through experimental implementation to demonstrate performance characteristics of the proposed force controller.