• Journal of the Korean Society for Heat Treatment
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• v.7 no.4
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• pp.262-269
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• 1994

This study has been carried out to evaluate effects of alloying elements and nitrocarburizing on rolling contact fatigue life. Manganese has a significant influence on the distribution of retained carbides and microstructural changes after rolling contact fatigue test. The effect of the manganese addition stabilized fine retained carbide particles during rolling contact fatigue life test, and so increased fatigue life markedly. High carbon chromium bearing steel with different matrixes were nitrocarbunzed by austenitic nitrocarburizing process at $850^{\circ}C$ for 4hrs. Rolling contact fatigue life of the nitrocarburized specimen was increased 2 times than full hardening treated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.875-879
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• 2007

The effects of the statistical properties of the Coulomb friction coefficients on the dynamic responses of a galloping quadruped robot are investigated in this paper. In general, the Coulomb friction coefficients are assumed to be deterministic for a controller design to achieve required motion characteristics. However, the friction coefficients between the ground and the robot legs are not constant in reality. Therefore, statistical characteristics of the friction coefficients need to be considered for a multi-body modeling of the robot galloping on the ground. The effects of the statistical properties on the dynamic responses of the quadruped robots are investigated.

• Tribology and Lubricants
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• v.10 no.2
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• pp.51-55
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• 1994

Rolling friction test was carried out to investigate the effect of the wear amount on rolling contact fatigue process in lubrication oil. The methods of this process were conducted at two Hertzian contact pressure and three slide ratio in each case by employing normalized and annealed carbon steel. During process of the rolling contact fatigue, the number of rotation until surface damage was occurred, the wear amount of rolling contact surface, and residual stress and half-value breadth using X-ray reflection on rolling contact surface were investigated. The result of this study shows that rolling contact fatigue process was directly influenced by wear trend and was confirmed by change of residual stress and half-value breadth on rolling contact surface.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1835_1836
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• 2009

본 논문에서는 비접촉식 미세 측정 광학기에 의해 측정된 이미지를 Stitching 기술과 B-Spline 보간법에 의해 보다 빠르고, 정밀한 복원 기법을 제안한다. 이를 위해 먼저 각각의 이미지로부터 매칭, 피매칭 템플릿(Template)을 검출한다. 그런 다음 두 이미지의 오버랩(Overlap)되는 부분을 기준하여 기준면으로부터 roll, pitch, yaw 오차를 계산하여 매칭시킨다. 마지막으로, B-Spline 보간법에 의해 매칭된 부분을 연속화한다. 제안된 방법은 실험을 통해 그 응용 가능성을 증명한다.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.1
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• pp.21-29
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• 2016

To overcome the large ring gear manufacturing problems seen in slewing bearings and girth gears, pin gear drive units have been developed. Among them, a novel slewing bearing with an internal pinwheel gear set (i-PGS) is introduced in this paper. First, we consider the exact cam pinion profile of i-PGS with the introduction of a profile shift coefficient. Furthermore, a new root relief profile modification for the i-PGS cam pinion is presented. Then, the contact stresses are investigated to determine the characteristics of the surface fatigue by varying the shape design parameters. The results show that the contact stresses of i-PGS can be reduced significantly by increasing the profile shift coefficient. In addition, the contact ratio, a measure of teeth overlapping action, decreases with the decrease of the allowable pressure angle.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1996.10a
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• pp.207-212
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• 1996

The shotpeening treatment were conducted for improving the strength of rolling contact fatigue of machine element like a gear. This paper was undertaken to analyze the influence of shotpeening treatment for inner race of ball bearing on the roiling contact fatigue. Shotpeening treatment were applied to the full hardened and the carbonitrided bearing. And the rolling contact fatigue life test and X-ray diffraction test were carried out. The results of this study showed that the fatigue life of ball bearing in the clean and the contaminated oil could be improved by shotpeening treatment. This effect was found to be more pronounced to the full hardened bearing.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.714-719
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• 2004

Railway wheels and axles belong to the most critical components in railway vehicles. The service conditions of railway vehicles became more severe in recent years due to the increase of speed. Therefore, a more precise evaluation of wheel/set life and safety has been requested. One of the major reasons of railway wheel damage is a contact zone failure by wheel/rail contact. In this paper, we conducted a rolling contact fatigue test for wheels using a specimen of wheel/rail. the behavior of hardeness and residual stress below the contact surface of the test pieces in the fatigue process were analyzed. Finally, the relation between fatigue life and contact pressure was obtained.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.04a
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• pp.74-79
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• 1997

Most of the results of recent research for the influence of indentation on rolling contact fatigue has been carried out with high strength material under the point contact. The plastic lug around the indent also has been known as a source of stress concentration. This study is undertaken to analyze the influence of indentation on rolling contact fatigue with low strength material under the line contact. The results in this study show that the plastic flow around indentation by rolling friction has a major influence, differed from the results of high strength material. And the change of residual stress and half-value breadth measured to the failure by X-ray diffraction can be identified to predict the rolling contact fatigue life of indented materials.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.8 s.173
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• pp.84-91
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• 2005

The role of microstructure is quite significant in fretting of Ti-6Al-4V since its material properties depend strongly on crystallographic texture. In this study, we adopt crystal plasticity theory with a 2-D planar triple slip idealization to account fur microstructure effects such as grain orientation distribution, grain geometry, as well as $\alpha$ colony size. Crystal plasticity simulations suggest strong implications of microstructure effects at fretting contacts.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.3
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• pp.299-305
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• 2017

Gate-lifting devices in small- to mid-sized sluice gates mostly employ the mechanical roller rack pinion (RRP) system. This RRP system, which consists of a rack-bar and a pinion, transforms a rotation motion into a linear one. The rack-bar has a series of roller trains that mesh with the pinion. In this study, we adopt an exact involute-trochoid tooth profile of the pinion to obtain a higher contact fatigue strength using the profile modification coefficient. Further, we determine the contact forces and investigate Hertz contact stresses to predict the pitting life of the pinion according to varying the shape design parameters. The results indicate that the design fatigue life of an RRP system for sluice gate can be achieved only when the design value of the profile modification coefficient reaches or exceeds a certain level.