A steel spring floating-slab track (SSFST) capable of mitigating railway-induced vibrations has been widely used in a metro line in Beijing. In sharp curves with radii of less than 500 m, severe corrugation with wavelengths of about 125–200 mm and passing frequencies of 70–80 Hz occurred on low rails. Field measurements and numerical simulations were used to investigate the cause of the corrugation. The results show that the wavelength of corrugation is related to the speed of the vehicle and the corrugation passing frequency is a fixed frequency. The formation of the rail corrugation in the sharp curves does not depend on the torsional and bending resonances of wheelsets and P2 resonance. The wheel–rail vertical fluctuating force at frequencies of 67–75 Hz arises easily under a broadband excitation of the rail irregularity due to the vertical bending of the rail and the floating slab relative to the subgrade. The numerical simulations show that the corrugation with dominant wavelengths of 160–200 mm initiates when the vehicle passes over the irregularity. The simulation results are consistent with the field test results. The corrugation occurs on SSFST as a result of the vertical bending of the entire track, driven by a wavelength-fixing mechanism.
A railway wheel installed with the web-mounted noise shielding and vibration damping assemblies is introduced in this paper. The shielding and damping assemble is alternant constrained to the both ends connecting to the tyre and hub. This design can produce shear strain in periodical variation, and then vibration energy of the shielding plate and the wheel is dissipated effectively. Assembles can also reduce the noise radiation from the wheel web. In order to investigate the vibration and sound radiation reduction of this new type of wheel relevant tests are carried out in a semi-anechoic room. In the test, damping ratio, acceleration, sound energy, sound field and directivity of the damping wheel are given and analyzed. The same tests are conducted for a standard wheel as a comparison. The test results show that the damping ratio of the damping wheel increases significantly compared to the standard one, especially for the damping ratios at the prominent resonance frequencies. The increase of the damping ratio is as much as 44 times. The sound energy levels (SEL) of the damping wheel in the overall range and at a dominant resonance frequency are, respectively, 15 and 40 dB, much less than those of the standard one. By comparing the sound fields and directivities of the two wheels, the sound radiation of the damping wheel is lower in all directions.
In order to study the relation between rail cant and wheel/rail rolling contact behavior,it is analyzed that LMA wheelset with 1353 mm back-to-back distance in contact with a tangent track with 60 kg/m rails and 1435 mm gauge.The improved program of three-dimensional contact geometry of wheelset/track is used to calculate the contact geometry parameters of the wheelset/track versus the lateral displacement of the wheelset.These analyzed parameters include the contact point location,the contact angle,the instant rolling circle radius,the equivalent conicity,and the normal distance between the wheel and rail.They are used in the calculation of the creepages and the rolling contact behavior of the wheelset.The creepages are calculated with formulas and the rolling contact behavior is determined by using Kalker's theory of three-dimensional elastic bodies in rolling contact with non-Hertzian and the corresponding program CONTACT.The calculated rolling contact behavior comprises the contact area,the stick/slip areas in the contact area,the slips,the contact stresses,and the friction work.The effect of the different rail cants on the contact geometry parameters and the rolling contact behavior is also investigated.The results obtained show that the rail cant has a great influence on the wheel-rail rolling contact behavior.The rolling radius difference and the equivalent conicity increase with the rail cant decreasing from 1/20 to 1/40,especially when the lateral displacement of the wheelset ranges from 6 mm to 9 mm.This character indicates that the rail cant of 1/40 more easily strengthens the self-centring capability of the wheelset and is propitious to curving negotiation.The maximum pressure and equivalent stress for 1/40 rail cant case are the smallest,but the total friction work is the greatest.The corresponding results for 1/20 rail cant show the opposite situation.According to all the numerical results,it is found that 1/40 rail cant is better than 1/20 for LMA-CN60.The results are useful for the optimum design of the rail cant.
The objective of this paper is to ascertain the wheel–rail low adhesion mechanism using a high-speed wheel–rail rolling contact test rig under different interfacial contaminations. Based on the experimental results, a numerical method was proposed to investigate the wheel–rail wear and rolling contact fatigue due to low adhesion issues. The experimental results indicated that the wheel–rail low adhesion phenomena can happen under interfacial liquid contaminations, especially at high-speed running condition. Preliminary numerical investigations showed that the low adhesion condition can easily lead to sliding hence serious wear, especially at the speed between 160 km/h and 200 km/h. The temperature rise within the contact patch can be significantly more severe once wheel and rail are in full slip, causing rolling contact fatigue due to material softening.
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