• Advances in nano research
• /
• 제12권5호
• /
• pp.483-488
• /
• 2022

The present work is an attempt to study the vibration analysis of the single-walled carbon nanotubes (SWCNTs) under the effect of the surface irregularity using Donnell's model. The surface irregularity represented by the parabolic form. According to Donnell's model and three-dimensional elasticity theory, a novel governing equations and its solution are derived and matched with the case of no irregularity effects. To understand the reaction of the nanotube to the irregularity effects in terms of natural frequency, the numerical calculations are done. The results obtained could provide a better representation of the vibration behavior of an irregular single-walled carbon nanotube, where the aspect ratio (L/d) and surface irregularity all have a significant impact on the natural frequency of vibrating SWCNTs. Furthermore, the findings of surface irregularity effects on vibration SWCNT can be utilized to forecast and prevent the phenomena of resonance of single-walled carbon nanotubes.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
• /
• pp.369-375
• /
• 2009

The Periodic replacements criterion of rail is calculated on the basis of the research result of RTRI in Japan. It is suggested that the service life of the continuous welded rail(CWR) is estimated by the relationship between the rail surface irregularity according to the accumulated passing tonnage and bending fatigue of welded part in CWR. In order to establish the periodic replacements criterion of CWR, this study measured the rail surface irregularity according to the accumulated passing tonnage, the types of track system and welding. Therefore, it is analyzed that the gas pressure welding is the worst one of the others. In addition, it is analyzed that the rail surface irregularity growth rate in ballast track is about $0.02{\sim}0.03mm$/100MGT and its in concrete track is about $0.005{\sim}0.02mm$/100MGT Finally, the result of this study is able to use the basis data to establishing the periodic replacements criterion of CWR considering rail grinding.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2010년도 춘계학술대회 논문집
• /
• pp.684-691
• /
• 2010

Rail is one of major track components for train service, it should be provided in the condition of flat and smooth driving aspect. Therefore, it is inevitable that there would be the field welding to integrate on CWR(Continuous Welded Rail) removing rail joint in these days. It is high chance to be some rail surface irregularity due to the limitation on the status of work condition If a high speed train runs on the rail surface irregularity in the welding part, big impact load comes to pass on that, so track irregularity cycle is reduced, therefore track maintenance cost can be increased. this paper has analyzed wheel load variation according to removing the rail surface irregularity using portable grinding machine in the high speed line. The result measured before and after in the field is decreased about 9.26% on the wheel load variation.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.988-991
• /
• 2006

Rolling Stock running are making Rail Head Surface damage(corrugation, flaking, shelling, etc). It's coming out Rail Head Surface Irregularity. It increases Rolling Stock and structure vibration. Therefore, this paper analyzes the influence of Rail Head Surface Irregularity to railway vibration. And, It introduces the management method of Rail Head Surface and proposes its R&D direction in railway-run organization.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2009년도 춘계학술대회 논문집
• /
• pp.1109-1110
• /
• 2009

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2010년도 춘계학술대회 논문집
• /
• pp.315-323
• /
• 2010

장대레일 교체주기는 자갈궤도 레일두부 표면요철과 레일 휨피로의 상관관계 분석을 통해 산정되었다. 본 연구에서는 국내 도시철도(서울메트로) 콘크리트궤도에서 레일두부 표면요철량에 따른 레일 휨응력을 측정하였다. 또한, 콘크리트궤도 레일두부 표면요철, 속도와 레일 휨응력의 상관관계를 분석하였다. 결론적으로, 중회귀분석을 통해 운행속도(U), 표면요철(v, w)에 따른 레일 휨응력(Y) 예측식을 도출하였다. 본 연구결과는 콘크리트궤도 장대레일 교체주기를 수립하기 위한 기초데이터로 활용이 가능할 것이다.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
• /
• pp.2135-2146
• /
• 2011

The rail surface irregularity is generated severely by train braking effect in the section of station. The braking force increases slip rate and friction factors caused by wheel-rail contact points. It brings rail surface irregularity as well. In this study, interactions between wheel and rail were investigated using rolling contact fatigue theory and mechanism of rail degradation through fracture mechanics. For the more, the Von-Mises stress occurred on the rail due to the interaction between wheel and rail was analyzed using 3-D finite element method. The amounts of surface irregularity of rail were measured according to accumulated passing tonnage in urban railway in fields. Therefore, the maintenance of rail should be separated by running and braking sections to prevent RCF defects.

• Smart Structures and Systems
• /
• 제23권1호
• /
• pp.31-44
• /
• 2019

The present study investigate the compressive stress, shear stress, tensile stress, vertical electrical displacement and horizontal electrical displacement induced due to a load moving with uniform velocity on the free rough surface of an irregular transversely isotropic functionally graded piezoelectric material (FGPM) substrate. The closed form expressions ofsaid induced stresses and electrical displacements for both electrically open condition and electrically short condition have been deduced. The influence of various affecting parameters viz. maximum depth of irregularity, irregularity factor, parameter of functionally gradedness, frictional coefficient of the rough upper surface, piezoelectricity/dielectricity on said induced stresses and electrical displacements have been examined through numerical computation and graphical illustration for both electrically open and short conditions. The comparative analysis on the influence of electrically open and short conditions as well as presence and absence of piezoelectricity on the induced stresses and induced electrical displacements due to a moving load serve as the salient features of the present study. Moreover, some important peculiarities have also been traced out by means of graphs.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
• /
• pp.783-792
• /
• 2011

The control of rail surface irregularity is very important for the high speed train service in the high speed rail. In order to manage it, initial, preventative, and maintainable rail grinding have been performed and among them, preventative rail grinding conducts in every each year. This study carried out the field test for dynamic track response according to rail surface irregularity comparing before and after rail grinding. In addition, the change of dynamic track responses according to rail grinding was analyzed and the fatigue life was estimated though Rainflow Counting Method and RMC Equivalence Stress. Therefore, it suggested that rail fatigue life should be increased by rail grinding, because amount of impact occurred on track is decreased by getting rid of rail surface irregularity.

• 한국표면공학회지
• /
• 제43권1호
• /
• pp.12-16
• /
• 2010

The morphology of the passivated surface of stainless steel (SS) was quantitatively characterized based on fractal geometry. In particular, the surface irregularities of the passivated 304 and 439 SSs were comparatively analyzed in terms of their self-similar fractal dimensions. The passivated surface of 439 SS in an acid-based electrolyte proved to have a higher fractal dimension, as compared to that of 304 SS, esp. at a scale of several tens of nanometers, strongly indicating the higher irregularity of the passivated surface. It is anticipated that the fractal approach suggested herein might be effectively utilized to analyze the irregularity of the steel surface and/or the compactness of the oxide film.