• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제26회 추계학술대회
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• pp.145-151
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• 1997

PAG(Polyalkylene Glycol) and esters are tested with HFC-134a as a refrigeration oil. This investigation enhances the testing method by taking the compressor's environment into account. A testing environment charged with refrigerant gas more closely simulates the conditions of a compressor. The friction coetTicient of the PAG/HFC-134a system is similar to that of the mineral oil/CFC-12 system at operating conditions. Ester oils are preferable at the start & stop condition in the lubricity aspect. PAG shows good lubricity in conditions of extreme contact pressure. Consequently, this test provides reliable results on compressor lubricity of refrigeration oils with HFC-134a. It suggests a methodological way for the proper selection of refrigeration oils that may improve the durability and performance of a compressor.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.87-92
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• 2000

In this paper, we investigated the braking performance of a composite brake shoe for power car. Laboratory bench test and field tests were carried out to characterize the braking performance by the parameters such as friction coefficient, wear rate, braking temperature and stopping distance. Density distribution was found to have a significant influence on the wear rate. The composite brake shoe with even density distribution showed better braking performance. The braking performance of a composite brake shoe was also compared with that of a cast iron brake shoe which is currently being used. The result indicated the performance of the composite brake shoe is better than the cast iron brake shoe.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.344-349
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• 2005

This paper presents a geometrical error analysis of wheel curve generation method for micro aspheric surface machining using parallel grinding method. In aspheric grinding, wheel wear in process is crucial parameter for profile error of the ground surface. To decrease wheel weal parallel grinding method is adopted. Wheel and work piece (Tungsten carbide) contact point changes during machining process. In truing process of the wheel radius is determined by the angle and distance between wheel and truer. Wheel radius error is predominantly affected by vertical deviation between the wheel rotation center and the truer center Simulation for vertical error and wheel radius error shows same tendency that expected by geometrical analysis. Experimental results show that the analysis of curve generation method matches with simulations and wheel radius errors.

• Tribology and Lubricants
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• 제35권6호
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• pp.330-336
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• 2019

Conditioning is a process involving pad surface scraping by a moving metallic disk that is electrodeposited with diamond abrasives. It is an indispensable process in chemical-mechanical planarization, which regulates the pad roughness by removing the surface residues. Additionally, conditioning maintains the material removal rates and increases the pad lifetime. As the conditioning continues, the pad profile becomes unevenly to be deformed, which causes poor polishing quality. Simulation calculates the density at which the diamond abrasives on the conditioner scratch the unit area on the pad. It can predict the profile deformation through the control of conditioner dwell time. Previously, this effect of the diamond shape on conditioning has been investigated with regard to microscopic areas, such as surface roughness, rather than global pad-profile deformation. In this study, the effect of diamond shape on the pad profile is evaluated by comparing the simulated and experimental conditioning using two conditioners: a) random-shaped abrasive conditioner (RSC) and b) uniform-shaped abrasive conditioner (USC). Consequently, it is confirmed that the USC is incapable of controlling the pad profile, which is consistent with the simulation results.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.836-842
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• 2001

The more sophisticated patterns of propagation model is presented in this paper, which includes three different source characteristics. The spherical, cosine and dipole radiation characteristics compared and sound event level and the maximum sound level are calculated by experiment and calculation. It is shown that patterns of propagation has dipole characteristics for low speed range(below about 150km/h) at electric multiple system. We know that push-pull high speed system(maximum speed: 300km/h) has cosine characteristics of noise propagation. For this purpose, We conduct the experiment of noise and know the empirical formula of noise level and radiation coefficient K. This model of simulation is conducted through point source array model at wheel/rail contact point by using program and experimental formula. We can guess prediction of profile, flat and wear of wheel by above modeling in near field.

• 대한기계학회논문집
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• 제19권1호
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• pp.292-300
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• 1995

According to the number of cold-rolled coils, the amount of roll wear and thermal expansion, and roll gap profile were calculated, by using the actual data from the finishing mill. Also, based on those data, the calculations of the deflection, the flattening, and the contact pressure of vwork rolls and backup rolls were made respectively. Specially, in the calculation of contact pressure, the numerical results were obtained not only during the normal rolling, but also during the abnormal rolling, by modeling mathematically the dynamic impact force which occurs when the head section of the strip is threading through rolls. With those results the growth of the fatigue region and the fatigue damage of rolls were predicted. Also the optimum roll-grinding depth was determined to maximize the roll life.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.37-43
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• 2000

The effect of the alignment of the contacting bodies is concerned. Tilting of a body (indenter) is regarded as a mis-alignment. Recently developed method fur evaluating the contact normal traction is introduced and discussed, in which piecewise parabolic profile is considered as a generalized contact profile. Indentation by a wedge with rounded apex is solved as an example problem. In the case of partial slip regime, the variation of shear traction is examined during the closed path of shear force by using the efficient numerical technique. Concentration of the slip region is also investigated. By evaluating the energy dissipation from the contact surface, the effect of the mis-alignment-alignment on wear is discussed.

• Tribology and Lubricants
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• 제15권2호
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• pp.164-170
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• 1999

Gerotor is widely used as a hydraulic pump or motor, by virtue of its volume changing ability. Performance deterioration of a gerotor hydraulic motor mainly due to the wear come from the contact between inner rotor with trochoidal curve and outer rotor with circular arc profile. This research covers the basic investigation about the contact forces of a gerotor hydraulic motor using analytic method. The influence of the eccentricity and the radius of circular arc teeth on the contact stress was evaluated.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.123-124
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• 2010

• 한국철도학회논문집
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• 제16권2호
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• pp.93-98
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• 2013

Railway system is today the most efficient way for transportation in many cases in several forms of application. Yet, wear phenomenon, profile evolution, fatigue, fracture, derailment are the major worries (financial and safety) in this system which force significant direct and indirect maintenance costs. To improve the cyclic maintenance procedures and the safety issues, it can be very satisfactory to be informed of the state of wheel/rail interaction with mileage. In present paper, an investigation of the behavior of the shear stresses by logged distance is approached, by implementing the field measurement procedure, in order to determine the real conduct of the most important cause of defects in wheel/rail contact, shear stress. The results coming from a simulation procedure indicate that the amounts of shear stresses are still in high-magnitudes when the wheel and rail are completely worn; even though in simulation based on the laboratory measurements of profile evolutions, the stresses become significantly reduced by logged distance.