Parameter Influences on Rail Corrugation of Metro Tangential Track

2020 ◽  
pp. 2150034
Author(s):  
Zhiqiang Wang ◽  
Zhenyu Lei
Keyword(s):  
Characteristic Frequency ◽  
Control Variable ◽  
Low Frequency ◽  
Vehicle Speed ◽  
Characteristic Frequencies ◽  
Vertical Stiffness ◽  
Rail Corrugation ◽  
Friction Power ◽  
Specific Frequency ◽  
Dominant Characteristic

Rail corrugation can reduce riding comfort by vibration and noise, and even cause running accident. In this paper, the vehicle–track coupled dynamic model was developed for a metro’s tangential track considering the wear in rail materials. The influences of different track structure parameters and vehicle speed on the generation and development of rail corrugation of the tangential track were analyzed using the developed model by the control variable method. The results show that for different parameters, the friction power in wheel–rail contact patch fluctuates with time, but the overall fluctuation range is relatively uniform. Meantime, an analysis of one-third octave curves of the friction power reveals that the characteristic frequencies of friction power are mainly concentrated in the middle and low frequency bands. At the dominant characteristic frequency, the longitudinal stiffness and damping of fasteners, and lateral and vertical damping of fasteners have less influence on rail corrugation, while the lateral and vertical stiffnesses of fasteners, spacing of fasteners, wheel–rail friction coefficient and vehicle speed have greater effect on rail corrugation. The changes in vertical stiffness and spacing of fasteners will cause the characteristic frequency of friction power to be offset, resulting in a shift from 80[Formula: see text]Hz to 100[Formula: see text]Hz, which will further lead to rail corrugation of the corresponding wavelength. Thus, it can be concluded that the vertical stiffness and spacing of fasteners have an important impact on the generation and development of rail corrugation at the specific frequency. Besides, the variations of the other variables bring little change to the characteristic frequencies of friction power as well as on rail corrugation. The mechanism of parameters unveiled here provides some guides for the parameter optimization problem on restraining the generation or development of rail corrugation on the tangential track.

Contact and creep characteristics of wheel–rail system under harmonic corrugation excitation

2020 ◽  
pp. 107754632095335
Author(s):  
Zhenyu Lei ◽  
Zhiqiang Wang
Keyword(s):  
Frequency Band ◽  
High Frequency ◽  
Low Frequency ◽  
Vertical Vibration ◽  
Vibration Acceleration ◽  
Characteristic Frequencies ◽  
Rail Corrugation ◽  
Average Value ◽  
Creep Characteristics ◽  
Creep Force

To study the wheel–rail contact and creep characteristics and the evolution law of corrugation with different wavelengths, the wave-like wear is idealized as continuous harmonic excitations consisting of three wavelengths and wave depths, and the vehicle–track space coupled dynamic model is established for specific analysis. The results show that when the wavelength is fixed and the wave depth increases, the average values of rail/wheel vertical vibration acceleration and wheel–rail longitudinal creepage/creep force increase and the average value of transverse creepage/creep force decreases. But, when the wave depth is fixed and the wavelength increases, the average values of rail/wheel vertical vibration acceleration and longitudinal creepage/creep force decrease and the average value of transverse creepage/creep force increases. Both longitudinal and transverse creepages/creep forces contain the characteristic frequency consistent with the passing frequency of initial irregularity. The characteristic frequencies of longitudinal creepages/creep forces tend to develop in the high-frequency band with the increase of wave depth, whereas the characteristic frequencies of transverse creepages/creep forces concentrate in the low-frequency band and decrease with the increase of wave depth. Under the condition of the same wavelength, with the increase of operation times, the wear amount increases slightly in the low-frequency band but greatly in the middle- and high-frequency bands, which shows that rail corrugation will gradually develop toward short wavelength corrugation at the constant velocity. When rail corrugation is formed, its development speed will gradually slow down with the increase of vehicle running times, and the development speed of short wavelength corrugation is faster than that of long wavelength corrugation.

EXPRESS: The effect of low frequency equalisation on preference and sensorimotor synchronisation in music

2021 ◽  
pp. 174702182110371
Author(s):  
Scott Beveridge ◽  
Estefanía Cano ◽  
Steffen A. Herff
Keyword(s):  
Body Movement ◽  
Low Frequency ◽  
Empirical Support ◽  
Processing Technique ◽  
Original Version ◽  
Upper Body ◽  
Signal Processing Technique ◽  
Band Energy ◽  
Sensorimotor Synchronisation ◽  
Specific Frequency

Equalisation, a signal processing technique commonly used to shape the sound of music, is defined as the adjustment of the energy in specific frequency components of a signal. In this work we investigate the effects of equalisation on preference and sensorimotor synchronisation in music. Twenty-one participants engaged in a goal-directed upper body movement in synchrony with stimuli equalised in three low-frequency sub-bands (0 - 50 Hz, 50 - 100 Hz, 100 - 200 Hz). To quantify the effect of equalisation, music features including spectral flux, pulse clarity, and beat confidence were extracted from seven differently equalised versions of music tracks - one original and six manipulated versions for each music track. These music tracks were then used in a movement synchronisation task. Bayesian mixed effects models revealed different synchronisation behaviours in response to the three sub-bands considered. Boosting energy in the 100 - 200 Hz sub-band reduced synchronisation performance irrespective of the sub-band energy of the original version. An energy boost in the 0 - 50 Hz band resulted in increased synchronisation performance only when the sub-band energy of the original version was high. An energy boost in the 50 - 100 Hz band increased synchronisation performance only when the sub-band energy of the original version was low. Boosting the energy in any of the three subbands increased preference regardless of the energy of the original version. Our results provide empirical support for the importance of low-frequency information for sensorimotor synchronisation and suggest that the effect of equalisation on preference and synchronisation are largely independent of one another.

Theoretical investigation into the measurability of rail unevenness and corrugation using the dynamic response of axle box and bogie

2020 ◽  
pp. 095440972092321
Author(s):  
Yurong Wang
Keyword(s):  
Dynamic Response ◽  
Standing Waves ◽  
Vehicle Speed ◽  
Long Distance ◽  
Rail Corrugation ◽  
Track Maintenance ◽  
Track System ◽  
Measurement Results ◽  
Ballasted Track ◽  
Rail Irregularity

Monitoring track unevenness is important for noise and vibration control and track maintenance. Rail corrugation and shorter wavelength track unevenness can be measured using the corrugation analysis trolley, but it is not suitable for measurement over long distance. It is of great significance to study the dynamic behavior of the response of the axle box and bogie to the unevenness excitation for a better understanding of the measurement results. In this paper, the dynamic response of the axle box and bogie to the unevenness excitation is analyzed in the frequency domain by taking account of multiple wheel–rail interactions, which is the case in practice. The response of the axle box and bogie is found to be affected by the so-called P2 resonances at low and medium frequencies and the standing waves of rail vibration at higher frequencies due to the multiple wheel–rail interactions. Based on the analysis of the response of the axle box and bogie, the measurability of track unevenness is discussed. Results show that the measurement of rail unevenness using the axle box response is mainly limited by the P2 resonance. The frequency range of measurement for the ballasted track studied is estimated to be 1–35 Hz, corresponding to the measurable unevenness wavelength of 0.6–20 m (or longer) at a vehicle speed of 20 m/s. Above 200 Hz, the standing waves of rail vibration will cause serious uncertainty in the measurement of short wavelength rail irregularity using the axle box response for the resilient track. Short pitch rail corrugation, however, can be evaluated using the axle box response due to its strong correlation with certain modes of the wheel–track system.

Effect of rail pad stiffness on the wheel/rail force intensity in a railway slab track with short-wave irregularity

2019 ◽  
Vol 233 (10) ◽  
pp. 1038-1049 ◽  
Author(s):  
Amin Khajehdezfuly
Keyword(s):  
High Frequency ◽  
Critical Speed ◽  
Concrete Slab ◽  
Low Frequency ◽  
Short Wave ◽  
Vehicle Speed ◽  
Frequency Range ◽  
Slab Track ◽  
High Frequency Excitation ◽  
Frequency Excitation

In this paper, a two-dimensional numerical model is developed to investigate the effect of rail pad stiffness on the wheel/rail force in a slab track with harmonic irregularity. The model consists of a vehicle, nonlinear Hertz spring, rail, rail pad, concrete slab, resilient layer, concrete base, and subgrade. The rail is simulated using the Timoshenko beam element for considering the effects of high-frequency excitation produced by short-wave irregularity. The results obtained from the model are compared with those available in the literature and from the field to prove the validity of the model. Through a parametric study, the effect of variations in rail pad stiffness, vehicle speed, and harmonic irregularity on the wheel/rail force is investigated. For the slab track without any irregularity, the wheel/rail force is at maximum when the vehicle speed reaches the critical speed. As the rail pad stiffness increases, the critical speed increases. When the amplitude of irregularity is high, wheel jumping phenomenon may occur. In this situation, as the vehicle speed and rail pad stiffness are increased, the dynamic wheel/rail force is increased. In the low-frequency range, the wheel/rail force increases as the rail pad stiffness increases. In the high-frequency range, the wheel/rail force increases as the rail pad stiffness is decreased.

Phase-based spectrum analysis method for identifying weak harmonics

2018 ◽  
Vol 24 (23) ◽  
pp. 5585-5596 ◽  
Author(s):  
Jingsong Xie ◽  
Wei Cheng ◽  
Yanyang Zi ◽  
Mingquan Zhang
Keyword(s):  
Signal Processing ◽  
Fourier Transform ◽  
Wavelet Transform ◽  
Characteristic Frequency ◽  
Discrete Wavelet ◽  
Accurate Identification ◽  
Processing Methods ◽  
Characteristic Frequencies ◽  
Frequency Detection ◽  
Signal Processing Methods

Fault characteristic frequency extraction is an important means for the fault diagnosis of rotating machineries. Traditional signal processing methods commonly use the amplitude information of signals to detect damages. However, when the amplitudes of characteristic frequencies are weak, the recognition effects of traditional methods may be unsatisfactory. Therefore, this paper proposes the phase-based enhanced phase waterfall plot (EPWP) method and frequency equal ratio line (FERL) method for identifying weak harmonics. Taking a cracked rotor as an example, the characteristic frequency detection performances of the EPWP and FERL methods are compared with that of the traditional signal processing methods namely fast Fourier transform, short-time Fourier transform, discrete wavelet transform, continuous wavelet transform, ensemble empirical mode decomposition, and Hilbert–Huang transform. Research results demonstrate that the effects of EPWP and FERL for the recognitions of weak harmonics which are contained in steady signals and transient signals are better than that of the traditional signal processing methods. The accurate identification of weak characteristic frequencies in the vibration signals can provide an important reference for damage detections and improve the diagnostic accuracy.

Audible-frequency stiffness of a primary suspension isolator on a high-speed tilting bogie

2003 ◽  
Vol 217 (1) ◽  
pp. 47-62 ◽  
Author(s):  
L Kari
Keyword(s):  
High Speed ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Vertical Stiffness ◽  
Audible Frequency ◽  
Minimum Number ◽  
Shear Relaxation ◽  
Operator Kernel ◽  
Incompressible Rubber ◽  
Good Agreement

The preload-dependent dynamic stiffness of a primary suspension isolator on a high-speed tilting bogie is examined via measurements and modelling within an audible frequency range. The stiffness is found to depend strongly on both frequency and preload. The former displays some resonance phenomena, such as stiffness peaks and troughs, while the latter exhibits a steep low-frequency stiffness increase in addition to an anti-resonance peak shifting to a higher frequency with increased preload. The problems of simultaneously modelling the preload and frequency dependence are removed by adopting a frequency-dependent waveguide approach, assuming incompressible rubber with an Abel operator kernel as its shear relaxation function. The preload dependence is modelled by a non-linear shape factor based approach, using a globally equivalent preload configuration. All the translational stiffnesses are modelled, including the vertical, longitudinal and lateral directions, and the vertical stiffness results are compared to those of measurements in a specially designed test rig. Good agreement is obtained for a wide frequency domain-covering 100-600 Hz-using a minimum number of parameters and for a wide preload domain-from vanishing to the maximum in service, 90 kN.

On-Board Aircraft Engine Bearing Prognostics: Enveloping or FFT Analysis?

2009 ◽  
Author(s):  
Hai Qiu ◽  
Huageng Luo ◽  
Neil Eklund
Keyword(s):  
Spectrum Analysis ◽  
High Frequency ◽  
Characteristic Frequency ◽  
Low Frequency ◽  
Aircraft Engine ◽  
Frequency Region ◽  
Data Sampling ◽  
Frequency Range ◽  
Bearing Defect ◽  
Bearing Characteristic

Roller bearing prognosis requires the detection of a bearing defect signature in the earliest possible stage in order to avoid a minor or catastrophic mechanical failure. Defects can occur in any of the bearing parts, inner and outer race, cage and rolling elements. It is possible to identify the defective component of the bearing based on the specific vibration frequencies that are excited. However, the pattern of vibration spectrum changes as the bearing deteriorates through different stages. Depending on which failure stage the bearing is in, different techniques are required to find fault signatures in different frequency ranges. Techniques such as enveloping analysis that works in the high frequency region require higher data sampling rates and therefore more expensive data acquisition hardware than techniques conducted in low frequency region. This paper compares two popular rolling element bearing diagnostics techniques — spectrum analysis in the bearing characteristic frequency range and enveloping analysis in the high frequency range — using aircraft engine test rig data. The techniques are compared both in terms of the time of detection and data sampling requirement; this analysis provides guidance for technology adoption in future field deployment. Results demonstrate that enveloping analysis is able to detect bearing defects much earlier than the spectrum analysis, but it requires a higher data sampling rate. The bearing defect characteristic frequency is detectable in low frequency spectrum only in the late stage of the failure and it is contaminated by other harmonics such as shaft unbalance. From a practical perspective, the final choice of the technology adopted for deployment should be based on an analysis of hardware requirements and tolerance of detection latency.

scholarly journals Dual-Frequency RF Impedance Matching Circuits for Semiconductor Plasma Etch Equipment

Electronics ◽  
2021 ◽  
Vol 10 (17) ◽  
pp. 2074
Author(s):  
Jeongsu Lee ◽  
Sangjeen Hong
Keyword(s):  
Impedance Control ◽  
Impedance Matching ◽  
Low Frequency ◽  
Electrode Impedance ◽  
Dual Frequency ◽  
Plasma Etch ◽  
Bias Power ◽  
Ion Energy ◽  
Specific Frequency ◽  
Frequency Power

The change in electrode impedance of semiconductor equipment due to repetitive processes is a major issue that creates process drift. In the current plasma etch chamber with a dual-frequency power system, the high-powered radio frequency (RF) source contributes to the enhancement of the plasma density, and the low-frequency bias power at the bottom electrode is adopted to enhance the injected ion energy in the plasma. The impedance control of the top electrode in dual-frequency capacity coupled plasma limits the impedance matching capability of the RF matching system because it only considers the high-frequency RF source. To control the precise impedance in dual-frequency semiconductor equipment, independent impedance control is required for each frequency. In this study, the impedance corresponding to a specific frequency was independently controlled using L (inductor) and C (capacitor). A 60 MHz stop filter and VVC were used to control 2 MHz impedance at a specific point, and a 2 MHz stop filter and VVC were used to control 60 MHz impedance. In the case of 2 MHz impedance control, the 2 MHz impedance changed from 10.9−j893 to 0.3−j62 and the 60 MHz impedance did not change. When controlling the 60 MHz impedance, the 60 MHz impedance changed from 0.33 + j26.53 to 0.2 + j190 and the 2 MHz impedance did not change. The designed LC circuits cover the impedance of 60 and 2 MHz separately and are verified by the change in the capacitance of the vacuum variable capacitors implemented in the RF impedance matching system.

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