• 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.429-430
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• 2008

• Korean Journal of Materials Research
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• v.7 no.9
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• pp.744-749
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• 1997

본 연구에서는 고주파 유도경화처리한 중탄소강의 회전접촉 피로거동을 0.44wt.%C강과 0.55wt.%C강을 사용하여 조사하였다. 회전접촉 피로시험은 Polymet RCF-1 시험기에서 탄성유체 윤활 조건으로 회전속도 8,000rpm, 최대 Hertz응력 492kg/m$m^2$을 가하면서 실시하였다. 미세한 lath마르텐사이트가 고주파 유도경화한 0.44wt.%C강과 0.55wt.%C강의 표면경화층에 형성되었고 소량의 페라이트가 일부 형성되었으며 0.44wt.%C강과 0.55wt.%C에 비해 비교적 큰 페라이트가 나타났다. 회전접촉 피로시험 후 표면경도가 거의 유지되는 표면경화층에서 회전접촉 피로시험전에 비해 경도가 상승하였다. 이 경도증가량의 최대치($\Delta$ Hv$_{max}$)와 피로수명과의 관계를 조사한 결과 0.55wt.%C강이 0.44wt.%C강에 비해 회전접촉 피로중에 일어나는 소변형에 대한 높은 저항성에 주로 기인하여 $\Delta$ Hv$_{max}$값은 낮게 나타나고 피로수명은 높게 나타났다.

• Tribology and Lubricants
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• v.31 no.5
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• pp.189-194
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• 2015

This paper focuses on the conformal contact problem. A typical example of conformal contact is the contact between a pin and hole. In particular, this paper focuses on the condition for assuming a contact stress field to be a Hertzian pressure profile by using well-known classical solutions associated with Hertzian contact. Persson first developed the conformal contact analysis method around half a century ago, but there have been no significant improvements since then. The present research also adopted this method, but developed new solutions from the viewpoint of application to structural design. The analysis began with a comparison between Persson°Øs conformal contact stress and the Hertzian stress fields. The next step was to check the differences in the normalized stress values of both. This study used the tolerance for the difference in the peak stresses of Persson°Øs solution and the Hertz solution to validate the Hertzian assumption. This gave the range for the difference in radii of the pin and hole when the contact force and mechanical properties of the material are specified. The results showed that, at a tolerance of 5%, the Hertzian assumption is valid if half of the contact angle is less than 35°ý. In addition, the Hertzian assumption holds even for a relatively long contact length, in contrast to the general incomplete contact problem. This paper discusses these results along with other aspects of the application to the design.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.4
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• pp.59-65
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• 2010

This paper presents the study on the contact stress analysis of a pair of mating spur gears during rotation. Contact stress analysis is performed between two spur gear teeth at different contact positions during rotation. An example is presented to investigate the variation of contact stress on a pair of mating gears with contact positions. The variation of contact stress during rotation is compared with the contact stress at lowest point of single tooth contact(LPSTC) and AGMA Equation for contact stress. The results show that contact stress varies along the contact position and gets maximum values in the beginning and end of the contact. In this study, the gear design considering the contact stress on a pair of mating gears is more severe than that of AGMA standard.

• Journal of Korean Association for Spatial Structures
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• v.11 no.3
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• pp.77-83
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• 2011

Laminated composite plates have shown their superiority over metals in applications requiring high specific strength, high specific modulus, and so on. Therefore, they have used in various industry. However, they have poor resistance to impact compared to typical metal materials. To resolve this problem by many researchers for a variety of studies have been attempted. This study investigates characteristic of impact behavior of laminated composite plates due to initial stress. Using finite element program which involved the indentation law, we investigate characteristic of impact behavior of laminated composite plates due to initial stress.

• Tribology and Lubricants
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• v.24 no.2
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• pp.90-95
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• 2008

An elastic-plastic contact analysis is developed using a semi-analytical method. The elastic contact is solved within a Hertz theorem. The reciprocal theorem with initial strains is then introduced, to express the surface geometry as a function of contact stress and plastic strains. The irreversible nature of plasticity leads to an incremental formulation of the elastic-plastic contact problem, and an algorithm to solve this problem is set up. Closed form expression, which give residual stresses and surface displacements from plastic strains, are obtained by integration of the reciprocal theorem. The distribution of contact stress, residual stress and plastic strain are obtained by the changed surface geometry.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.11
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• pp.1453-1459
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• 2011

A roller pinion gear (RPG) system composed of either a pin or a roller and its conjugated cam gear can improve the gear endurance from that of a conventional gear system by reducing the sliding contact while increasing the rolling motion. In this paper, we first proposed the exact cam gear profile and the self-intersection condition obtained when the profile shift coefficient is introduced. Then, we investigated the Hertzian contact stresses and the load stress factors while the varying the shape design parameters to predict the gear surface fatigue life, which is strongly related to the gear noise and vibration at the contact patch. The results show that the pitting life can be extended significantly by increasing the profile shift coefficient.

• Tribology and Lubricants
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• v.31 no.6
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• pp.272-280
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• 2015

Recently, Luu suggested fatigue life equation that uses every term of the Crossland equation with stress gradient effect. Luu’s model, however, has a limit of being unable to coverage small radii that are less than a specified length. Furthermore, rolling model has a very small contact area compared to the rolling element size, and fatigue failure occurs on the small radius such as surface asperity by cyclic loading. Therefore, it is necessary to modify fatigue life equation in order to enable fatigue analysis for a small radius. In this paper, the fatigue life considering a stress gradient effect in rolling contact was obtained using Luu’s modified equation. Fatigue analysis was performed to study the effect of stress gradient on the fatigue life using newly adopted equation and to compare the results with pervious models. In order to do this, a series of simulation such as surface stress analysis, subsurface stress analysis, and fatigue analysis are conducted for two rolling balls of same size that contact each other. Through such a series of processes, the fatigue life can be calculated and equation that is proposed in this paper evaluates the fatigue life in case the contact area is small.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.481-488
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• 1988

In the analysis of impulsive response of plate, Lagrange's theory, Reissner's theory and Mindlin's theory are generally used. But, in applying these theories the impulsive stresses directly underneath the concentrated impact point cannot be analyzed because the solution fails to converge. In this paper, therefore, an attempt for a supported square plate is made by using three-dimensional dynamic theory of elasticity on the supposition that the uniform distributed load acts on the central part of it. In order to clarify the validity of theoretical analysis, the strain variations are measured experimentally for a square glass plate. Finally it is shown that these theoretical results are in close agreement with the experimental results.