• Journal of Oral Medicine and Pain
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• v.14 no.1
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• pp.35-42
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• 1989

악구강계의 질환을 진단하고 치료후의 예후를 판정하기 위하여 maximal clenching시에 측정된 tooth contacts의 수와 분포가 이용되어 왔다. 그러나 maximal clenching시 반복된 tooth contacts의 측정은 저작근 피로등 문제점을 가지고 있다. 본연구는 건강한 성인 15명을 대상으로 maximal clenching 및 habitual clenching시 T-Scan system을 이용하여 치아접촉 수와 접촉시간을 측정, 비교 검토하여 habitual clenching을 이용한 방법이 Tooth contacts의 연구에 이용될 수 있는지를 확인 하는데 목적이 있으며, 연구결과는 다음과 같다. 1. Habitual clenching시 upright, semisupine position에서의 전측두근의 근활성은 maximal clenching시의 64.5%, 61.9% 및 73.3%로 나타났다. 2. Maximal clenching시 치아접촉 수와 접촉시간은 16.82개 및 0.429초로 나타났으며 habitual clenching시에는 11.65개 및 0.177초로 나타났다. 3. 치아접촉수와 접촉시간은 체위에 따라 크게 변화되지 않았다. 4. 치아접촉수와 접촉시간의 측정시에 habitual clenching을 이용하는 방법이 maximal clenching을 이용하는 방법보다 재현성이 더 높은 것으로 나타났다. 5. Tooth contacts의 연구시 habitual clenching을 기준으로 사용할 수 있다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.9
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• pp.1391-1398
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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 wheelset life and safety has been requested. Wheel/rail contact fatigue and thermal cracks due to braking heat are two main mechanisms of the railway wheel failure. In this paper, an evaluation procedure for the contact fatigue life of railway wheel is proposed. One of the main sources of the contact zone failure is the residual stress. The residual stress on wheel is formed during the manufacturing process which includes a heat treatment, and then is changed by contact stress developed by wheel/rail contact and thermal stress induced by braking. Also, the cyclic stress history for fatigue analysis is determined by applying finite elements analysis for the moving contact load. The objective of this paper is to estimate fatigue life by considering residual stress due to heat treatment, braking and repeated contact load, respectively.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1995.06a
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• pp.25-30
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• 1995

본 연구에서는 건식 구름접촉시 발생하는 tribological한 현상들을 plate on ball tester를 이용하여 실험적으로 고찰하였다. 실험의 주된 관심은 각 열처리 방법으로 제작한 시편에 대하여 건식 구름접촉시 cycle수에 따른 plate의 표면 거칠기, 트랙의 형상, 졍도 및 구름저항의 변화이며 이런 자료를 토대로 열처리공정의 차이에서 오는 정도수명 및 피로수명에 대한 상대평가를 통해 마찰, 마멸의 저감에 적합한 열처리방법을 제시하고자 한다.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.5
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• pp.531-537
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• 2012

Fretting fatigue tests were conducted to investigate the effect of contact pressure on fretting fatigue behavior in aluminum alloy A7075-T6. Test results showed that when the contact pressure is so low that gross or partial slip occurs at the pad/specimen interface, fretting fatigue damage increases with the contact pressure. However, when the contact pressure is high enough to prevent slip at the interface, fretting fatigue damage decreases with the contact pressure. In order to understand how the contact pressure influence the fretting fatigue damage, finite element analyses were conducted and the analysis results were used to evaluate critical plane fretting fatigue damage parameters and their components. It is revealed that fretting fatigue damage estimated with the parameters exhibits the same variation as that in the tests. Moreover, the variation of fretting fatigue damage is closely related with that of the maximum normal stress on the critical plane rather than the strain amplitude on the critical plane.

• Tribology and Lubricants
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• v.27 no.3
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• pp.162-166
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• 2011

This study is aimed to predict the fatigue life for bearings under combined radial, thrust and moment load. In order to do this, a series of simulation such as bearing load distribution, initial surface stress, subsurface stress and fatigue analysis is needed. And using the bearing's material fatigue property we can predict fatigue life for ball bearing.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.8
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• pp.84-91
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• 2002

This paper analyzes the subsurface stress at the spherical contact using Hamilton equation, and with that data, calculates the fatigue limit under the variations of friction coefficient using fatigue theory. After rough surface being made, this paper figures out the random load generated by contacting to the rough surface, analyzes the stress of its subsurface, and calculates the fatigue limit of the rough surface using fatigue theory. The three parts of the fatigue theory are applied, which are critical plane theory, stress invariant theory and mesoscopic theory.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.53-59
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• 2004

Rough surfaces are taking into account to estimate the contact fatigue life. A computational methodology and the theoretical basis in this case is presented in this paper. Displacement solution technique by Cho and Love is applied to calculate the stress history beneath the surface subjected to loading. Mesoscopic multiaxial fatigue criterion is then applied to predict fatigue life. This fatigue criterion yields satisfactory results for non-proportional loading and can satisfactorily describe the physical mechanisms of crack initiation as well. As a result of analysis the relation between the life and the roughness as well as the most probable depth of the crack nucleation is discussed.

• Tribology and Lubricants
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• v.29 no.1
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• pp.33-38
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• 2013

This study is aimed to predict the fatigue life for pitch bearings under combined radial, thrust load and moment. In order to do this, a series of simulation such as bearing load distribution, initial surface stress, subsurface stress and fatigue analysis is needd. Fatigue life for pitch bearing can be predicted by using a bearing's material fatigue property.

• 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.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.1
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• pp.53-61
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• 2016

Angular misalignment has a significant effect on the characteristics of angular contact ball bearings (ACBBs). This paper presents an analysis of fatigue life for ACBBs subjected to angular misalignment. A simulation model is developed with de Mul's bearing model and the ISO basic reference rating life model. Simulation is performed to calculate the life of the ACBBs subjected to angular misalignment. The numerical results show that angular misalignment influences the load distribution significantly, thus reducing the bearing rating life. The fatigue life of ACBBs is decreased by angular misalignment regardless of axial preload, external radial load and rotational speed. The results show that angular misalignment should be maintained at less than 1mrad for ACBBs.