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Critical speed

About: Critical speed is a research topic. Over the lifetime, 2764 publications have been published within this topic receiving 31365 citations.


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Journal ArticleDOI
TL;DR: In this paper, an integrated train-track-subsoil dynamic interaction model of ground vibration is developed on the basis of vehicle dynamics, track dynamics and the Green's functions of subsoil.

73 citations

Journal ArticleDOI
TL;DR: A simple and effective method is presented that allows the diagnosis of rotor faults for induction machine drives in time-varying conditions and is tailored to direct rotor flux field-oriented controlled drives.
Abstract: Motor current signature analysis is the reference method for the diagnosis of induction machines' rotor faults; however, in time-varying conditions, it fails as slip and speed vary, and, thus, sideband components are spread in a bandwidth that is proportional to the variation. Variable speed drive applications are common in the aerospace, appliance, railway, and automotive industries and also in electric generators for wind turbines. In this paper, a simple and effective method is presented that allows the diagnosis of rotor faults for induction machine drives in time-varying conditions. It is tailored to direct rotor flux field-oriented controlled drives, where the control system provides suitable signals that are exploited for the demodulation to a constant frequency of time-varying signatures related to the rotor faults. Simulations and experiments are reported to validate the proposed method on a critical speed transient.

72 citations

Journal ArticleDOI
TL;DR: In this article, the coupling between bending and torsion due to gears as well as the effect of axial torque on bending vibrations is taken into account to determine the coupled lateral and Torsional response due to torsional excitation.

71 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present a method to rapidly predict the speed at which high speed trains travel close to the wave propagation velocity of the supporting track-ground system, which results in a significant increase in track maintenance due to subgrade deterioration.
Abstract: When high speed trains travel close to the wave propagation velocity of the supporting track-ground system, large amplitude track deflections are generated. This has safety implications, and also results in a significant increase in track maintenance due to subgrade deterioration. Thus, this paper presents a method to rapidly predict the speed at which these ‘critical velocity’ effects occur. The method is based upon a dispersion analysis of both the track (either ballast or non-ballasted/slab track) and the underlying ground, which are treated as uncoupled systems. Unlike previous approaches, the new calculation approach is fully automated thus not requiring any post-processing to extract the soil dispersion curve. It also works for soil layers of arbitrary depth, uses minimal computing power and can calculate critical speeds associated with higher soil modes. The dispersion based method can be deployed on new/existing lines via a drop-weight test, or using existing geotechnical data. Its accuracy is tested by comparing the results against an alternative semi-analytical, quasi-static railtrack model, and found to be 97% accurate. The code is useful for railway track infrastructure design and its short run times mean it can be used as a scoping tool for newly proposed high speed railroad lines. To obtain new insights into the key variables effecting critical velocity, a sensitivity analysis is undertaken using 1000 random soil profiles. It is found that on average, for the same track height, slab tracks are less likely to encounter critical velocity issues than ballasted tracks because their critical speed is typically 11% higher. It is also shown that track height plays an important role with increases in slab track thickness and reductions in ballasted track thickness both causing increases in critical velocity. Furthermore, it is found that soil saturation affects critical speed considerably (by up to 12–17% depending on track type) because changes to Poisson’s ratio alter the dispersion characteristics of layered soils in the mid-frequency range, where critical velocity effects occur. Finally, it is shown that railpad stiffness has a low influence, and that increasing the rail bending stiffness on ballasted tracks increases critical speed.

71 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20241
202343
2022120
202182
202092
2019102