• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.7
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• pp.1149-1155
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• 1997

J-integral for a subsurface horizontal crack in a circular plate with an inner hole under rolling line contact is evaluated according to loading positions with various load conditions, crack length and crack location. Two-dimensional crack is modeled, and the relation between Tresca stress for uncracked model and J-integral is discussed. The loading location which gives the maximum J-integral depends on load condition and crack location, and the presence of friction force increases Tresca stress and J-integral near the surface. Regardless of friction force, crack location that gives maximum J-integral is the same as that of maximum Tresca stress in an uncracked model, and the value of J-integral is propotional to crack length. It is also showed that the variation of an inner radius of a disk does not effect J-integral value.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.6
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• pp.931-937
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• 2008

The rail/wheel rolling contact affects the microstructure in the surface layer of rail. Recently. continuum damage mechanics allows us to describe the microprocesses involved during the straining of materials and structures at the macroscale. Elastic and plastic strains. the corresponding hardening effects are generally accepted to be represented by global continuum variables. The purpose of continuum damage mechanics is to introduce the possibility of describing the coupling effects between damage processes and the stress-strain behavior of materials. In this study. the continuum damage mechanics caused by elastic deformation was briefly introduced and applied to the fatigue damage of the rails under the condition of cyclic loading. The material parameter for damage analysis was first determined so that it could reproduce the life span under the compressive loading in the vicinity of fatigue limit. Some numerical studies have been conducted to show the validity of the present computational mechanics analysis.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.738-739
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• 2006

This paper will describe a powder and processing method that facilitates single press-single sintered densities approaching $7.5g/cm^3$. At this sintered density, mechanical properties of the powder metal (P/M) component are significantly improved over current P/M technologies and begin to approach the performance of wrought steels. High performance gears have the added requirement of rolling contact fatigue durability that is dependent upon localized density and thermal processing. Combining high density processing of engineered P/M materials with selective surface densification enables powder metal components to achieve rolling contact fatigue durability and mechanical property performance that satisfy the performance requirements of many high strength automotive transmission gears. Data will be presented that document P/M part performance in comparison to conventional wrought steel grades.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.1109-1114
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• 2005

The rolling contact fatigue of wheels for high speed trains is a matter of increasing importance. The wheel damages from fatigue crack makes noise up and safety down. RCF-casued accidents cause traffic congestion and economical costs as well as personal injuries. In this study, we examine the rolling contact fatigue of wheels for power car running at 300km/h. Using the results of multi-body dynamic analysis and the proposed procedure of Ekberg, we calculate the fatigue index of surface-initiated fatigue, subsurface-initiated fatigue and fatigue initiated at deep material defects. As a result. the fatigue index shows us whether fatigue will appear and in which form. In addition, we present Shakedown map on surface-initiated fatigue.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.144-145
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• 2006

A developed molybdenum hybrid-alloyed steel powder is based on a molybdenum prealloyed steel powder to which molybdenum powder particles are diffusion bonded. The sintered compact made of this powder has a finer pore structure than that of the conventional molybdenum prealloyed steel powder, because the ferritic iron phase $({\alpha}-phase)$ with a high diffusion coefficient is formed in the sintering necks where molybdenum is concentrated resulting in enhanced sintering. The rolling contact fatigue strength of the sintered and carburized compacts made of this powder improved by a factor of 3.6 compared with that of the conventional powder due to the fine pore structures.

• 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.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.5
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• pp.148-156
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• 2000

In this paper, we investigate contact characteristic of wheel-rail interface for rolling stock using the finite element method. Contact stress distribution due to the rail mounting slope is obtained in order to reduce the contact stress. Stress analysis of the rail, firstly, is performed one subjected to elliptical pressure based on Hertz theory. Secondly, we perform stress analysis of the rail subjected to contact stress obtained by this study. Results for the maximum shear stress, its location and the principal shear stress distribution are compared.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.5
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• pp.380-387
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• 2016

Present research target to develop the procedure of long-term fatigue analysis of the structural details near the upper rolling chock of IMO type B tank by using the time domain modal analysis technique where both the contact and friction behavior can be accurately simulated. In order to perform the time domain analysis focused on the contact and friction, the entire model of the hull and tank was condensed with DOF reduction technique, which is obtained by transforming the global finite element model into its quasi-static modal coordinate. Modal analysis using the quasi-static deformation modes is chosen as a cost effective time domain simulation method and this is based on the fact that the structural response of the tank is quasi-static. Based on the developed cost effective time domain simulation method, the long-term fatigue analysis procedure for the structural details near the rolling chock and key of independent type tank is targeted to be established. The developed fatigue assessment procedure takes into account, wave induced stress and both contact and friction induced stress without loss of accuracy.

• Tribology and Lubricants
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• v.36 no.6
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• pp.371-377
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• 2020

In In this study, we compared the results of a ball bearing life prediction model based on rolling element loads with the results of fatigue life prediction of ball bearings when a stress-based contact fatigue life prediction technique is applied to the ball bearing. We calculate the load acting on each rolling element by the external load of the bearing and apply the result to the Lundberg-Palmgren (LP) theory to calculate ball bearing life based on the rolling element. We also calculate stress-based ball bearing life through contact and fatigue analyses based on contact modeling of the ball and raceway while considering the fatigue test results of AISI 52100 steel. In stress-based life prediction, we use three high-cycle fatigue-determination equations that can predict the fatigue life when multi-axis proportional loads such as rolling-slide contact conditions are applied. These equations are derived from the stress invariant and critical plane methods and the mesoscopic approach. Life expectancy results are compared with those of the LP model. Results of the analysis indicated that the fatigue life was predicted to be lower in the order of the Crossland, Dang Van, and Matake models. Of the three, the Dang Van fatigue model was found to be the closest to the LP life.

• Journal of Korea Foundry Society
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• v.14 no.3
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• pp.267-273
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• 1994

The structure of austempered ductile cast iron, called ADI, consists of graphite, retained austenite, and bainite. The bainite component of them is considered a useful structure for exriting materials for roll of rolling mill. Therefore, the ADI can be considered applicable to material for rolling contact element. The diverse tests, such as rolling contact friction test, impact test, and X-ray reflection test, were carried out to investigate the possibility of it`s application. The result of this study showed that the expected fact was confirmed. The specimen showed that the best performance had the structure of the low bainite containing the stable retained austenite of about 20%.