Effects of Ni-Coated Graphite Flake on Braking Behavior of Cu-Based Brake Pads Applied in High-Speed Railway Trains

Cu-based brake pads applied in high-speed railway trains containing Ni-coated graphite flake and uncoated graphite flake were fabricated by powder metallurgy. The braking properties of the brake pads were investigated by a scaled down testing apparatus with the pad-on-disk configuration under various braking speeds and braking pressures. Compared with the brake pads containing uncoated graphite flake (designated GF), the brake pads containing Ni-coated graphite flake (designated NGF) exhibits a similar braking performance at lower braking speed and pressure. However, NGF shows more stable friction coefficient, lower linear wear loss, and lower maximum temperature during the braking process at worse braking conditions, e.g., 350 km/h, 1.5 MPa. The Ni-coating on the surface of Ni-coated graphite can transfer the mechanical bonding between copper and graphite to diffusion bonding so that there is a stronger interface bonding between copper and Ni-coated graphite. Further, the multiple linear regression analyses reveal that the mean friction coefficient of NGF is more sensitive to braking pressure than braking speed because of the better thermal resistance of NGF, while the mean friction coefficient of GF and the linear wear loss are mainly affected by braking speed.

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Study on Wear and Fatigue Performance of Two Types of High-Speed Railway Wheel Materials at Different Ambient Temperatures

Materials ◽

10.3390/ma13051152 ◽

2020 ◽

Vol 13 (5) ◽

pp. 1152

Author(s):

Lei MA ◽

Wenjian WANG ◽

Jun GUO ◽

Qiyue LIU

Keyword(s):

High Temperature ◽

Low Temperature ◽

High Speed ◽

Room Temperature ◽

Lamellar Spacing ◽

Wear Loss ◽

High Speed Railway ◽

Railway Wheel ◽

Ambient Temperatures ◽

Railway Wheels

The wear and fatigue behaviors of two newly developed types of high-speed railway wheel materials (named D1 and D2) were studied using the WR-1 wheel/rail rolling–sliding wear simulation device at high temperature (50 °C), room temperature (20 °C), and low temperature (−30 °C). The results showed that wear loss, surface hardening, and fatigue damage of the wheel and rail materials at high temperature (50 °C) and low temperature (−30 °C) were greater than at room temperature, showing the highest values at low temperature. With high Si and V content refining the pearlite lamellar spacing, D2 presented better resistance to wear and fatigue than D1. Generally, D2 wheel material appears more suitable for high-speed railway wheels.

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Ballast Flying DEM Microscopic Analysis and Counteracting Measures

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.97-98.266 ◽

2011 ◽

Vol 97-98 ◽

pp. 266-270 ◽

Cited By ~ 1

Author(s):

Guo Qing Jing ◽

Liang Gao ◽

Xiao Lin Sun

Keyword(s):

Friction Coefficient ◽

Microscopic Study ◽

High Speed ◽

Microscopic Analysis ◽

Dynamic Force ◽

High Speed Railway ◽

Model Method ◽

Study Results

Ballast flying problems obsess the high speed railway developments, causing damages to the train and deteriorations to the rail. In the paper, DEM is used to conduct ballast flying mechanism microscopic study, results show ballast flying increases with train dynamic force, and decreases with ballast size and friction coefficient, ballast flying counteracting measures are presented, such as ballast bed parameter and ballast glue. In the end, future possible microscopic ballast flying model method is presented by DEM coupled with CFD.

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The Application of Vibration Accelerations in the Assessment of Average Friction Coefficient of a Railway Brake Disc

Measurement Science Review ◽

10.1515/msr-2017-0016 ◽

2017 ◽

Vol 17 (3) ◽

pp. 125-134 ◽

Cited By ~ 6

Author(s):

Wojciech Sawczuk

Keyword(s):

Friction Coefficient ◽

Heat Dissipation ◽

Brake Disc ◽

Brake Pads ◽

Rail Vehicles ◽

Wide Range ◽

Disc Brakes ◽

Vibroacoustic Diagnostics ◽

Braking Process

AbstractDue to their wide range of friction characteristics resulting from the application of different friction materials and good heat dissipation conditions, railway disc brakes have long replaced block brakes in many rail vehicles. A block brake still remains in use, however, in low speed cargo trains. The paper presents the assessment of the braking process through the analysis of vibrations generated by the components of the brake system during braking. It presents a possibility of a wider application of vibroacoustic diagnostics (VA), which aside from the assessment of technical conditions (wear of brake pads) also enables the determination of the changes of the average friction coefficient as a function of the braking onset speed. Vibration signals of XYZ were measured and analyzed. The analysis of the results has shown that there is a relation between the values of the point measures and the wear of the brake pads.

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Effects of friction-based fixed bearings on seismic performance of high-speed railway simply supported girder bridges and experimental validation

Advances in Structural Engineering ◽

10.1177/1369433218798120 ◽

2018 ◽

Vol 22 (3) ◽

pp. 687-701 ◽

Cited By ~ 2

Author(s):

Lizhong Jiang ◽

Shanshan Cao ◽

Biao Wei

Keyword(s):

Friction Coefficient ◽

Seismic Performance ◽

High Speed ◽

Dynamic Test ◽

Seismic Damage ◽

Damage State ◽

High Speed Railway ◽

Simply Supported ◽

Girder Bridges ◽

Seismic Force

This study investigated the seismic performance of simply supported girder bridges with a span length of 32 m. Those bridges were a common part in China’s high-speed railway system and used spherical bearings to connect girders and piers. First, a finite element model of the scaled bridge with a geometrical similarity ratio of 1:8 was established by OpenSees. Second, five seismic damage states of fixed bearings and piers were defined based on the deformation failure criterion. Finally, an incremental dynamic analysis and a pseudo-dynamic test were performed to evaluate the effects of friction-based fixed bearings on the seismic response and damage state of bearings and piers. Results show that the sliding of friction-based fixed bearings effectively restricts the force transmitting between piers and girders, and reduces the seismic damage of piers. Those bearings with a small friction coefficient lead to a large relative displacement between piers and girders, while those bearings with a large friction coefficient cause a large seismic force exceeding the yield load of piers. Therefore, an appropriate friction coefficient of friction-based fixed bearing should be determined to achieve an optimal seismic performance of bridge according to the specific conditions of bridge and ground motion inputs.

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Maximum temperature of the disc during repeated braking applications

Advances in Mechanical Engineering ◽

10.1177/1687814019837826 ◽

2019 ◽

Vol 11 (3) ◽

pp. 168781401983782 ◽

Cited By ~ 1

Author(s):

Piotr Grzes

Keyword(s):

Friction And Wear ◽

Element Model ◽

Maximum Temperature ◽

Bulk Temperature ◽

Brake Disc ◽

Subsequent Stage ◽

System Of Equations ◽

Brake Pads ◽

Brake Application ◽

The Mean

A computational finite element model of a brake disc for determining transient axisymmetric (two-dimensional) temperature field during repeated brake application has been proposed. The presented research is a subsequent stage of a previous study on the coupling of velocity and maximum temperature for a single braking in accordance with the system of equations of heat dynamics of friction and wear. In the analysed case, changes in the mean, flash, maximum and bulk temperature of the disc were determined and discussed. The calculations were carried out at the temperature-dependent coefficient of friction, the thermophysical properties of cast-iron disc combined with cermet brake pads and the time-varying contact pressure. The obtained results were compared with the reference values from the braking simulation at constant operating parameters and independent of temperature properties of materials. It was shown that the maximum values of the mean temperature for both cases differed slightly during the entire process. The flash temperature determined from the heat dynamics of friction and wear system of equations was the highest at the beginning and gradually decreased with the number of brake applications.

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Numerical simulation of rail surface-initiated rolling contact fatigue in the switch panel of railway turnouts

Proceedings of the Institution of Mechanical Engineers Part F Journal of Rail and Rapid Transit ◽

10.1177/0954409720909971 ◽

2020 ◽

pp. 095440972090997

Author(s):

Xiaochuan Ma ◽

Ping Wang ◽

Jingmang Xu ◽

Rong Chen ◽

Linya Liu

Keyword(s):

Friction Coefficient ◽

Fatigue Damage ◽

High Speed ◽

Interaction Analysis ◽

Rolling Contact Fatigue ◽

Contact Fatigue ◽

Rolling Contact ◽

Control Measures ◽

High Speed Railway ◽

Friction Control

Considering the complex characteristics of the track structure in railway turnouts, it is difficult and also expensive to experimentally study rail damages; therefore, numerical methods are an effective alternative. This study presents a numerical method to simulate rail surface-initiated rolling contact fatigue in the switch panel of railway turnouts. This method includes simulation of the vehicle–turnout wheel–rail dynamic interaction, analysis of the wheel–rail multipoint non-Hertzian rolling contact that considers the relative motion between the switch and stock rails, and calculation of the accumulated rail surface-initiated rolling contact fatigue. The accumulated rail surface-initiated rolling contact fatigue after the vehicles passed a turnout switch panel 80 times (the average number of vehicles running on the Chinese high-speed railway lines per day) in the through route with facing move was simulated based on this procedure. The result showed that the maximum surface-initiated rolling contact fatigue damage of the switch rail and the stock rail was 1.57 × 10−2 and 0.62 × 10−2, respectively. Surface-initiated rolling contact fatigue in the switch rail mainly occurred at the gauge angle, and in the stock rail it mainly occurred at the center of the rail. In addition, the influence of track parameters (rail inclination, track gauge, and friction coefficient) is analyzed. The friction coefficient influenced the rail surface-initiated rolling contact fatigue. When the coefficient exceeded 0.3 in particular, the rail rolling contact fatigue damage increased sharply. Hence, suitable friction control measures should be taken during rail maintenance in order to mitigate the rail surface-initiated rolling contact fatigue damage, e.g. by keeping the wheel–rail friction coefficient below 0.3.

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Tribological behaviors of precipitates reinforced Cr-Ni-Mo-V steel lubricated by water or water-silica mixture

Industrial Lubrication and Tribology ◽

10.1108/ilt-07-2017-0219 ◽

2018 ◽

Vol 70 (8) ◽

pp. 1431-1436 ◽

Cited By ~ 1

Author(s):

Shuaishuai Zhu ◽

Baosen Zhang ◽

Zhixin Ba ◽

Xiangyang Mao ◽

Weijie Fei ◽

...

Keyword(s):

Friction Coefficient ◽

High Speed ◽

Brake Disc ◽

Wear Properties ◽

Fatigue Wear ◽

Industrial Firms ◽

Content Type ◽

Liquid Cell ◽

Braking Process ◽

Worn Surface

Purpose This paper aims to investigate the friction and wear properties of Cr-Ni-Mo-V steel against 440C stainless steel under both water and water–silica mixture lubricant. Design/methodology/approach The Cr-Ni-Mo-V steel specimens were taken from a forged steel brake disc with the process of quenching at 900°C and tempering at 600°C. The tribological testing was performed using a contact configuration of ball-on-flat with a liquid cell according to the ASTM standard. Detailed examinations on the worn surface were analyzed using a scanning electron microscope. Findings The results indicate that the friction coefficient and friction damage of the steel sliding under water–silica mixture are higher than those under water. The friction coefficient decreases with increasing load and increases with the sliding speed for the two lubricants. The mass wear rate presents a rising trend with both sliding load and speed. The wear mechanisms of the Cr-Ni-Mo-V steel sliding under the two lubricants are oxidation wear, abrasive wear and fatigue wear. Research limitations/implications Because of the chosen tribological testing approach, the research results could not describe the tribological performance of the brake disc accurately during actual braking process of the high-speed train. Therefore, researchers are encouraged to test the proposed propositions further. Originality/value This study shows that the tribology behavior of the Cr-Ni-Mo-V steel with water or water–silica mixture lubrications helps the industrial firms and academicians to work on the wear of the brake disc in rainwater or wet environment.

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Effects of Oscillation Frequency on the Tribological Properties of Self-Lubrication Spherical Plain Bearings with PTFE Woven Liner

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.455.406 ◽

2010 ◽

Vol 455 ◽

pp. 406-410 ◽

Cited By ~ 11

Author(s):

Ming Qiu ◽

Z.L. Gao ◽

S.J. Yao ◽

Long Chen

Keyword(s):

Friction Coefficient ◽

Contact Pressure ◽

High Frequency ◽

Oscillation Frequency ◽

Wear Loss ◽

Linear Wear ◽

Plain Bearing ◽

Working Principle ◽

And Performance ◽

Spherical Plain Bearing

The working principle and performance characteristics of a self-made oscillation tribo-tester were introduced. Under different oscillation frequency and pressure conditions, the friction coefficient and linear wear of spherical plain bearings with polytetrafluoroethylene (PTFE) woven liner were investigated. By using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), the wear mechanism of the spherical plain bearing was analyzed. The results indicate that with the oscillation frequency increases, the friction coefficient of spherical plain bearings decreased while the wear loss increased. In the high frequency of 4.8Hz, the reduction ranges of the friction coefficient is not obvious with the contact pressure increased, but the effect of contact pressure on the wear of the spherical plain bearing is great. During the experiment, adhesive wear, abrasive wear and spalling wear took place on the surfaces of woven liners.

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Experimental Study on the Maximum Allowable Hydration Temperature for 900t Box Girder of High-Speed Railway

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.90-93.964 ◽

2011 ◽

Vol 90-93 ◽

pp. 964-968

Author(s):

Xue Min Li ◽

Er Yu Zhu ◽

Yong Zheng Zhou ◽

Yue Hong Qin

Keyword(s):

Experimental Study ◽

High Strength Concrete ◽

High Speed ◽

High Strength ◽

Maximum Temperature ◽

Railway Bridge ◽

Box Girder ◽

High Speed Railway ◽

Technical Guide ◽

Allowable Temperature

Due to the usage of high-strength concrete, excessive hydration heat is generated in the whole span box girder of high-speed railway. The maximum allowable temperature should not exceed 60°C according to the Technical Guide on Railway Bridge Construction of Passenger Dedicated Line. However, according to the field measurement and simulation to the maximum temperature of box girder concrete, we find that the maximum hydration temperature of concrete is generally more than 60°C which is the limited value of the specification. The research results show that the limited value of maximum hydration temperature for box girder concrete can be relaxed to 65°C.

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