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An Eigen root analysis is fulfilled for a high-speed rail vehicle concerning suspension parameters variation and active control using a simplified lateral-dynamics-intended model. The model is verified to be capable of reflecting the modal features of both carbody suspension modes and hunting modes. Subsequently, the effects of suspension parameters and the active yaw damper (AYD) on the vehicle modes are examined with various wheel/rail conicities. It shows that the frequency of hunting motion does not linearly increase with the vehicle speed but saturates to a value over 300 km/h. The crucial influential suspension parameters of the vehicle modes include the series stiffness and damping coefficient of the yaw damper, the longitude positioning stiffness on the wheelset, the series damping of the lateral damper, and the lateral stiffness of air springs. Sky-hook damping/stiffness control of AYD helps to increase the modal damping for bogie hunting concerns. For a large conicity of 0.37 case, a minimum of 400 kN·s/m is suggested for the damping control and 10 MN/m for stiffness control. Moreover, the damping control would adequately relieve the carbody hunting with a conicity of 0.11, and the stiffness control still works fine even with an extremely small conicity of 0.07. [ABSTRACT FROM AUTHOR]

This paper describes the longitudinal-vertical coupling dynamics of a high-speed train rescued by locomotives during the braking process on grades. The coupler jackknifing behaviour under compressive forces will affect the running safety of the coupling train. In this paper, the longitudinal-vertical impacts by field testing for the locomotive to train rescue scenario are firstly introduced. The quasi-static force analyses of the train and couplers are carried out to study the coupler jackknifing mechanism on graded tracks. The three-dimensional dynamic model of the train and coupler system is then developed. In this model, the coupler rotational motions, hysteresis characteristic of draft gears, braking characteristic are taken into account. The typical responses during the braking process for the high-speed train rescued by the diesel locomotive are reproduced and verified. The running safety of the longitudinal-vertical interaction for selected scenarios is further evaluated. The Influences of train speed and track gradient on the longitudinal-vertical dynamics are also studied. Two improvement measures, including the limitation of the coupler pitch angle and coupler force, are discussed to provide possible solutions. [ABSTRACT FROM AUTHOR]

The wheel polygonisation is the harmonic wave along the wheel circumference, which has been widely reported in high-speed railway vehicles in China in recent years. The polygonization mechanism has not been fully understood yet, and this work discusses one possible mechanism through several experiments. Firstly, a field test for the CRH3 high-speed train with polygonal wheels is carried out. It is found that the vibration in vertical takes major responsibility, and there are several resonance bands for the train-track system. Another field test shows that the rail is sensitive to the polygonisation characteristic frequency, but the wheel axle is not. Then the rail local vibration modes are analyzed by the operational deflection shape (ODS) test in the laboratory. A loaded bogie is fixed on the tested track to simulate the real working conditions. The result shows that the frequency of one local mode is 591 Hz, which is a typical wheel polygonisation frequency. Besides, the wheel-rail contact point is not on the vibration node of this local mode. Thus, the resonance of this local rail mode can be one possible mechanism for the high-order wheel polygonisation. [ABSTRACT FROM AUTHOR]

In order to establish a more accurate model to simulate actual working conditions, a back-calculation method for road excitation of monorail is introduced and dynamic transcendental equations are set up in this paper. By neglecting the subtle influence of the pitching angle on the vertical acceleration of the bogies, this dynamic model (i.e. the dynamic transcendental equations) is greatly simplified. Besides, the calculation result shall be closer to the measured data. Comparison between the back-calculation results of the two vehicles in a monorail proves that this method can be applied to experiments accurately. Through validating the model by comparing the experiment data and the simulated results, it can be noticed that the simulated result of the acceleration under the action of the back-calculated road irregularities is consistent with the experimental data, which indicates the back-calculation process is precise enough. Band pass filtering is applied to the measured acceleration data to get the signals in the frequency range of 0.5–10 Hz as per the standard, which proves that the model is valid only in low frequencies but good enough for researches of vehicle stability. [ABSTRACT FROM AUTHOR]

Wheel–rail contact calculation is of vital importance in vehicle system dynamics. In the existing methods of wheel–rail contact calculation, the finite element method and Kalker's CONTACT program, which are based on the complementary energy principle, are the two methods with accuracy recognised. However, because of its very slow calculation speed, it cannot meet the requirement of online calculation, so a variety of fast non-elliptic algorithms have been proposed. The semi-Hertz method, which is recognised for its great contributions to the fast wheel–rail contact calculation, is based on the concept of virtual penetration. The calculation of virtual penetration is crucial to evaluate the shape and normal pressure distribution of the contact patch. In practice, the virtual penetration is related to the curvature of the whole contact patch; however, the range of the contact patch is determined by the value of penetration. Such an interaction leads the calculation into a dead loop. In the semi-Hertz method, the penetration is calculated by the Hertz parameters of the initial contact point. Thus, the practical range of the method is limited. In this paper, a fast-iterative method for solving virtual penetration is proposed, and a reliable value of virtual penetration can be obtained under any lateral wheel–rail relative curvature variation with good stability and speed. The normal and tangential solutions are analysed with different methods in this paper. [ABSTRACT FROM AUTHOR]

High magnitude impact loads caused by polygonal wear of the wheels have been associated with in-service failures of structural components of high-speed railways, although the mechanisms leading to wheels' polygonalisation is not yet fully understood. In this study, a long-term field test programme is undertaken and the data are analysed to gain better understanding of the growth in polygonal wear, and its characteristics and correlation with the axle box acceleration. The field measurements on a high-speed railway involved monitoring of wheels profiles between successive re-profiling of the wheels so as to identify the rate of growth of wear in addition to the axle box acceleration. The data suggested rapid growth in wheel wear, which could be characterised by polygonal wear of nearly 18th and 19th harmonic order. It is further shown that the magnitude of axle box acceleration increased considerably with increasing wear magnitude of the wheel. [ABSTRACT FROM AUTHOR]

The polygonal wear around the wheel circumference could pose highly adverse influences on the wheel/rail interactions and thereby the performance of the vehicle system. In this study, the effects of wheel polygonalisation on the dynamic responses of a high-speed rail vehicle are investigated through development and simulations of a comprehensive coupled vehicle/track dynamic model. The model integrates flexible slab track, wheelsets and axle boxes subsystem models so as to account for elastic deformations caused by impact loads induced by the wheel polygonalisation. A field-test programme was undertaken to acquire the polygonal wear profile and axle box acceleration response of a high-speed train, and the data are used to demonstrate the validity of the coupled vehicle/track system model. Subsequently, the effects of wheel polygonalisation are evaluated in terms of wheel/rail impact forces, axle box vertical acceleration and dynamic stress developed in the axle considering different amplitudes and harmonic orders of the polygonal wear. The results suggest that the high-order wheel polygonalisation can give rise to high-frequency impact loads at the wheel/rail interface, and excite some of the vibration modes of the wheelset and the axle box leading to high-magnitude axle box acceleration and dynamic stress in the wheelset axle. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate the uptake, accumulation and the enhanced dissipation of di(2-ethylhexyl) phthalate (DEHP) spiked in soil (with a concentration of 117.4 ± 5.2 mg kg−1) by eleven plants including eight maize (Zeamays) cultivars and three forage species (alfalfa, ryegrass and teosinte). The results showed that, after 40 days of treatment, the removal rates of DEHP ranged from 66.8% (for the control) to 87.5% (for the maize cultivar of Huanong-1). Higher removal rate was observed during the first 10 days than the following days. Plants enhanced significantly the dissipation of DEHP in soil. Enhanced dissipation amount in planted soil was 13.3–122 mg pot−1for DEHP, and a net removal of 2.2%–20.7% of the initial DEHP was obtained compared with non-plant soil. The contribution of plant uptake to the total enhanced dissipation was <0.3%, and the enhanced dissipation of soil DEHP might be derived from plant-promoted biodegradation and sorption stronger to the soil. Nevertheless, the capability in accumulation and enhanced dissipation of DEHP from spiked soils varied within different species and cultivars. [ABSTRACT FROM AUTHOR]