Dynamic Contact Analysis of Current Collector Shoe and Third Rail under Quasi High Speed Condition

AbstractCharacteristic substrate speeds and meniscus shapes associated with the onset of air entrainment are studied during dynamic wetting failure along a planar substrate. Using high-speed video, the behaviour of the dynamic contact line (DCL) is recorded as a tape substrate is drawn through a bath of a glycerol/water solution. Air entrainment is identified by triangular air films that elongate from the DCL above some critical substrate speed. Meniscus confinement within a narrow gap between the substrate and a stationary plate is shown to delay air entrainment to higher speeds for a wide range of liquid viscosities, expanding upon the findings of Vandre, Carvalho & Kumar (J. Fluid Mech., vol. 707, 2012, pp. 496–520). A pressurized liquid reservoir controls the meniscus position within the confinement gap. It is found that liquid pressurization further postpones air entrainment when the meniscus is located near a sharp corner along the stationary plate. Meniscus shapes recorded near the DCL demonstrate that operating conditions influence the size of entrained air films, with smaller films appearing in the more viscous solutions. Regardless of size, air films become unstable to thickness perturbations and ultimately rupture, leading to the entrainment of air bubbles. Recorded critical speeds and air-film sizes compare well to predictions from a hydrodynamic model for dynamic wetting failure, suggesting that strong air stresses near the DCL trigger the onset of air entrainment.

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Capillary transfer of soft films

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2000340117 ◽

2020 ◽

Vol 117 (10) ◽

pp. 5210-5216 ◽

Cited By ~ 4

Author(s):

Yue Zhang ◽

Mengtian Yin ◽

Yongmin Baek ◽

Kyusang Lee ◽

Giovanni Zangari ◽

...

Keyword(s):

High Speed ◽

Computational Analysis ◽

Liquid Surface ◽

Theoretical Models ◽

Dynamic Contact ◽

Surface Wetting ◽

Motion Direction ◽

Wetting Properties ◽

Geometric Patterns ◽

Solid Substrates

Existing transfer technologies in the construction of film-based electronics and devices are deeply established in the framework of native solid substrates. Here, we report a capillary approach that enables a fast, robust, and reliable transfer of soft films from liquid in a defect-free manner. This capillary transfer is underpinned by the transfer front of dynamic contact among receiver substrate, liquid, and film, and can be well controlled by a selectable motion direction of receiver substrates at a high speed. We demonstrate in extensive experiments, together with theoretical models and computational analysis, the robust capabilities of the capillary transfer using a versatile set of soft films with a broad material diversity of both film and liquid, surface-wetting properties, and complex geometric patterns of soft films onto various solid substrates in a deterministic manner.

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Study on Bonding Properties of Copper and Aluminum in Nano Scale Using Molecular Dynamics Simulation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.152-154.183 ◽

2012 ◽

Vol 152-154 ◽

pp. 183-187 ◽

Cited By ~ 6

Author(s):

Quang Cherng Hsu ◽

Yen Yu Cheng ◽

Bao Hsin Liu

Keyword(s):

High Temperature ◽

Low Temperature ◽

Bonding Strength ◽

High Speed ◽

Tensile Force ◽

Pure Aluminum ◽

Pure Copper ◽

Dynamics Simulation ◽

Low Speed ◽

Speed Condition

According to MD simulation results, pressing depth between two bonding materials will affect bonding strength. Alloy material (Al0.9Cu0.1) had void defect phenomenon in low bonding speed condition because the increasing chance of atom migration which will result in low bonding strength. High tensile speed causes material fracture phenomena happen earlier than low speed. Material stress in low speed is smaller than in high speed. Fracture morphology of material is different in different tensile speed. In low speed condition, material can be stretched thinner than in high speed condition. Material in high temperature has greater kinetic energy than low temperature; therefore, material in high temperature has better formability and behaves larger tensile strain than low temperature. For pure aluminum, when temperature raises to 900K which is close to melting point (933K), its crystal structure is no longer belongs to F.C.C. structure, so bonding strength is weaker than low temperature. Large size material has larger contact area than small size material; therefore, the tensile force and tensile strength of the former are larger than the latter. The order of bonding strength for these three materials is: binary alloy > pure copper > pure aluminum.

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Lubricated Loaded Tooth Contact Analysis and Non-Newtonian Thermoelastohydrodynamics of High-Performance Spur Gear Transmission Systems

Lubricants ◽

10.3390/lubricants8020020 ◽

2020 ◽

Vol 8 (2) ◽

pp. 20 ◽

Cited By ~ 3

Author(s):

Gajarajan Sivayogan ◽

Ramin Rahmani ◽

Homer Rahnejat

Keyword(s):

High Speed ◽

High Performance ◽

Spur Gear ◽

Contact Analysis ◽

Operating Conditions ◽

Tooth Contact Analysis ◽

Transmission Systems ◽

Tooth Contact ◽

Contact Kinematics ◽

Loaded Tooth Contact Analysis

Energy efficiency and functional reliability are the two key requirements in the design of high-performance transmissions. Therefore, a representative analysis replicating real operating conditions is essential. This paper presents the thermoelastohydrodynamic lubrication (TEHL) of meshing spur gear teeth of high-performance racing transmission systems, where high generated contact pressures and lubricant shear lead to non-Newtonian traction. The determination of the input contact geometry of meshing pairs as well as contact kinematics are essential steps for representative TEHL. These are incorporated in the current analysis through the use of Lubricated Loaded Tooth Contact Analysis (LLTCA), which is far more realistic than the traditional Tooth Contact Analysis (TCA). In addition, the effects of lubricant and flash surface temperature rise of contacting pairs, leading to the thermal thinning of lubricant, are taken into account using a thermal network model. Furthermore, high-speed contact kinematics lead to shear thinning of the lubricant and reduce the film thickness under non-Newtonian traction. This comprehensive approach based on established TEHL analysis, particularly including the effect of LLTCA on the TEHL of spur gears, has not hitherto been reported in literature.

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In Situ Rubber-Wheel Contact on Road Surface Using Ultraviolet-Induced Fluorescence Method

Applied Sciences ◽

10.3390/app10248804 ◽

2020 ◽

Vol 10 (24) ◽

pp. 8804

Author(s):

Jhonni Rahman ◽

Yutaka Shoukaku ◽

Tomoaki Iwai

Keyword(s):

Contact Area ◽

High Speed ◽

High Sensitivity ◽

Dynamic Contact ◽

Road Surface ◽

Oxide Semiconductor ◽

Small Scale ◽

In Situ Observation ◽

On The Road

This study examines the relationship between rubber-wheel and the contact area on the road surface. Ultraviolet-induced fluorescence microscopy was used to observe and measure the contact parts with pyranine as a dye solution. The high sensitivity to U.V. light makes it easy to distinguish contact and non-contact regions on a very small scale. The experiment was conducted in static and dynamic conditions to identify its influence on the apparent contact area of rubber-wheel and road surface. The in-situ observation of the contact area was captured and recorded using a high-speed digital camera with 1-inch a CMOS (complementary metal oxide semiconductor) sensor. Additionally, the contact area between rubber-wheel and road surface was measured using an analyzing software. The results show differences in static and dynamic contact conditions based on the operating parameters.

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Dynamics of Droplet Motion Induced by Electrowetting

Volume 1: Heat Transfer in Energy Systems; Thermophysical Properties; Theory and Fundamentals in Heat Transfer; Nanoscale Thermal Transport; Heat Transfer in Equipment; Heat Transfer in Fire and Combustion; Transport Processes in Fuel Cells and Heat Pipes; Boiling and Condensation in Macro, Micro and Nanosystems ◽

10.1115/ht2016-7331 ◽

2016 ◽

Author(s):

Yi Lu ◽

Aritra Sur ◽

Dong Liu ◽

Carmen Pascente ◽

Paul Ruchhoeft

Keyword(s):

Contact Angle ◽

High Speed ◽

Numerical Models ◽

Dynamic Contact Angle ◽

Dynamic Contact ◽

High Speed Photography ◽

Droplet Dynamics ◽

Droplet Shape ◽

Moving Contact Line ◽

Moving Contact

Electrowetting has drawn significant interests due to the potential applications in electronic displays, lab-on-a-chip devices and electro-optical switches, etc. Current understanding of electrowetting-induced droplet dynamics is hindered by the inadequacy of available numerical and theoretical models in properly handling the dynamic contact angle at the moving contact line. A combined numerical and experimental approach was employed in this work to study the spatiotemporal responses of a droplet subject to EW with both direct current and alternating current actuating signals. The time evolution of the droplet shape was measured using high-speed photography. Computational fluid dynamics models were developed by using the Volume of Fluid-Continuous Surface Force method in conjunction with a selected dynamic contact angle model. It was found that the numerical models were able to accurately predict the key parameters of the electrowetting-induced droplet dynamics.

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On Scaling Method to Investigate High-Speed Over-Tip-Leakage Flow at Low-Speed Condition

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4038619 ◽

2018 ◽

Vol 140 (6) ◽

Author(s):

Hongmei Jiang ◽

Li He ◽

Qiang Zhang ◽

Lipo Wang

Keyword(s):

High Speed ◽

Turbine Blades ◽

Flow Distribution ◽

Tip Clearance ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Scaling Method ◽

Low Speed ◽

Tip Leakage ◽

Speed Condition

Modern high-pressure turbine blades operate at high-speed conditions. The over-tip-leakage (OTL) flow can be high-subsonic or even transonic. From the consideration of problem simplification and cost reduction, the OTL flow has been studied extensively in low-speed experiments. It has been assumed a redesigned low-speed blade profile with a matched blade loading should be sufficient to scale the high-speed OTL flow down to the low-speed condition. In this paper, the validity of this conventional scaling approach is computationally examined. The computational fluid dynamics (CFD) methodology was first validated by experimental data conducted in both high- and low-speed conditions. Detailed analyses on the OTL flows at high- and low-speed conditions indicate that, only matching the loading distribution with a redesigned blade cannot ensure the match of the aerodynamic performance at the low-speed condition with that at the high-speed condition. Specifically, the discrepancy in the peak tip leakage mass flux can be as high as 22%, and the total pressure loss at the low-speed condition is 6% higher than the high-speed case. An improved scaling method is proposed hereof. As an additional dimension variable, the tip clearance can also be “scaled” down from the high-speed to low-speed case to match the cross-tip pressure gradient between pressure and suction surfaces. The similarity in terms of the overall aerodynamic loss and local leakage flow distribution can be improved by adjusting the tip clearance, either uniformly or locally.

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The impact of video lottery game speed on gamblers

Journal of Gambling Issues ◽

10.4309/jgi.2006.17.12 ◽

2006 ◽

Cited By ~ 16

Author(s):

Robert Ladouceur ◽

Serge Sévigny

Keyword(s):

High Speed ◽

Structural Characteristics ◽

Responsible Gambling ◽

Loss Of Control ◽

Low Speed ◽

Problem Gamblers ◽

Speed Condition ◽

The Impact ◽

Video Lottery ◽

Practical Implications

Video lotteries seem to be one of the most profitable games for the gambling industry and are reported as the game of choice for many problem gamblers. Their popularity or, in some cases, their addictiveness, might be related to their structural characteristics: reinforcement schedule, lights, appearance, sound, and speed. We investigated the effects of video lottery game speed on concentration, motivation to play, loss of control, and number of games played. Forty-three participants were randomly assigned to either a high-speed (5 seconds) or a low-speed (15 seconds) condition. Results: gamblers in the high-speed condition played more games and underestimated the number of games played more than did participants in the low-speed condition. However, speed did not influence concentration, motivation, or loss of control over time or money. Conclusion: speed has a limited impact on occasional video lottery gamblers. The theoretical and practical implications of speed are discussed in the context of responsible gambling policies.

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