Search

Copyright of Rolling Stock (1002-7602) is the property of Rolling Stock Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The impact of transport-induced vibrations on people is a particularly important problem. Sudden or intensifying vibration phenomena of a local nature may compromise safety, especially in transport. The paper addresses the results of research on the impact of spring stiffness parameters on the propagation of vibrations in the vehicle structure using simple amplitude and frequency measures. The use of the developed method of selective multi-criteria analysis of frequency bands made it possible to compare the vibrations recorded in the vehicle with a new or worn coil spring. The results of the present study allow the development of a large data base in which all signals are classified by the exploitation parameters and location of the propagation of vibration in the vehicle. The most important findings and achievements of the presented study are the testing of actual suspension components with real damage under controlled conditions, the identification of the vibration propagation path from the wheel to the driver and passenger feet, the quantitative comparison of vibrations affecting humans in the vehicle (through the feet), and the frequency decomposition of vibration for selected bands. These findings improve the proper interpretation of the developed measures and, as a result, the difficulties in using this knowledge at the engineering level, for example, in the design and construction improvement stage. Therefore, innovation points and engineering significances are a method of selective multi-criteria analysis of frequency bands and have potential applications in diagnostics and the design of suspension systems and in terms of passengers' comfort. [ABSTRACT FROM AUTHOR]

When borax gets wet, it clumps. In this case, 76,000 pounds of previously wetted borax clumped on the inside of a rail car. The unbalanced load caused the rail car to fall on a yard worker, killing him. Tracking meteorological conditions in transit from Turkey to a port in Deleware, truck transit to a warehouse, handling at the warehouse, and rail transit to an interim transfer station was key to developing the origin and cause for the rail car derailing. There was evidence that clumping had rendered the product unusable by the end-user. However, this event occurred at the interim transfer station where the rail car product was transferred to trucks. This paper describes the process of determining how and where the borax absorbed moisture and shows physics that determined derailing was the result of an unbalanced load. This demonstrates the cause and effect of this event. [ABSTRACT FROM AUTHOR]

Copyright of Rolling Stock (1002-7602) is the property of Rolling Stock Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The impact of transport-induced vibrations on people is a particularly important problem. Sudden or intensifying vibration phenomena of a local nature may compromise safety, especially in transport. The paper addresses the results of research on the impact of spring stiffness parameters on the propagation of vibrations in the vehicle structure using simple amplitude and frequency measures. The use of the developed method of selective multi-criteria analysis of frequency bands made it possible to compare the vibrations recorded in the vehicle with a new or worn coil spring. The results of the present study allow the development of a large data base in which all signals are classified by the exploitation parameters and location of the propagation of vibration in the vehicle. The most important findings and achievements of the presented study are the testing of actual suspension components with real damage under controlled conditions, the identification of the vibration propagation path from the wheel to the driver and passenger feet, the quantitative comparison of vibrations affecting humans in the vehicle (through the feet), and the frequency decomposition of vibration for selected bands. These findings improve the proper interpretation of the developed measures and, as a result, the difficulties in using this knowledge at the engineering level, for example, in the design and construction improvement stage. Therefore, innovation points and engineering significances are a method of selective multi-criteria analysis of frequency bands and have potential applications in diagnostics and the design of suspension systems and in terms of passengers’ comfort.

Dynamic behavior of vehicle systems and driving comfort is an optimization problem. Passive suspension system usage in design considerations is seen in heavy commercial vehicles where the owners are known to be highly cost conscious. Subjective evaluation of driving comfort by skilled drivers results from individual’s perceptions about vibrations with wide variations. Simulation methods and/or objective test measurements are used for finding the influence of vehicle structural parameters and operational parameters. Studies were conducted with objective of finding the minimum acceleration levels at driver seat for optimum driving comfort. In such research, full-vehicle model optimization needs complex simulations and iterations of the approximations to achieve optimum ride comfort. In this paper, cost-effective optimization of the suspension system design and geometry for a new vehicle application are explained. Structural design variables selected through simulation models have been evaluated with objective of achieving minimum acceleration at the driver seat. Orthogonal array method was applied for reducing the number of test configurations to six, from 48 possible combinations. The results obtained show the structural design parameter optimization by objective evaluation as effective for optimum ride comfort. Acceleration levels measured in test vehicle configuration with the shortest kingpin mounting location and progressive stiffness springs with damper at the rear-axle showed a significant improvement in ride comfort. No significant improvement was observed from different damper configurations in the front suspension. Thus, the ride comfort was enhanced with minimal changes only in the rear-axle suspension design parameters and optimization of vehicle hitching point geometry during the development of new vehicle application. It has been proposed to select variables through simulation, optimize the number of test configurations using orthogonal array and make an objective evaluation of the ride impact progressively based on successive test results.

The vehicle test big data has important significance for the study of vehicle performance and characteristics. Aiming at the test of the dynamic stiffness characteristics of a bogie suspension system of rail vehicles, a simplified rigid-flexible hybrid model of the bogie is established, and the force condition of the bogie suspension system is analyzed. Based on this simplified model, a mathematical model of the dynamic stiffness of the primary suspension, secondary suspension, and integrated suspension is established. In addition, a method for testing the three-way dynamic stiffness of a bogie suspension system in a complete, assembled state is proposed, and a dynamic stiffness test model of the bogie primary suspension, secondary suspension, and comprehensive suspension is established. Dynamic stiffness tests of the primary suspension, secondary suspension, and integrated suspension were carried out, and according to the big data analysis of the bench test, the dynamic stiffness curve of each suspension in the frequency of 0.5-5 Hz is obtained. The test results show that the dynamic stiffness of the suspension of the bogies varies nonlinearly with the change in frequency. The dynamic stiffness values of the suspensions at different frequencies vary greatly. As a result, the vehicle's operating characteristics cannot be evaluated based on the suspension static stiffness or the suspension stiffness at a single frequency, indicating the necessity of the suspension dynamic stiffness test after the bogie is assembled.

Dynamic behavior of vehicle systems and driving comfort is an optimization problem. Passive suspension system usage in design considerations is seen in heavy commercial vehicles where the owners are known to be highly cost conscious. Subjective evaluation of driving comfort by skilled drivers results from individual's perceptions about vibrations with wide variations. Simulation methods and/or objective test measurements are used for finding the influence of vehicle structural parameters and operational parameters. Studies were conducted with objective of finding the minimum acceleration levels at driver seat for optimum driving comfort. In such research, full-vehicle model optimization needs complex simulations and iterations of the approximations to achieve optimum ride comfort. In this paper, cost-effective optimization of the suspension system design and geometry for a new vehicle application are explained. Structural design variables selected through simulation models have been evaluated with objective of achieving minimum acceleration at the driver seat. Orthogonal array method was applied for reducing the number of test configurations to six, from 48 possible combinations. The results obtained show the structural design parameter optimization by objective evaluation as effective for optimum ride comfort. Acceleration levels measured in test vehicle configuration with the shortest kingpin mounting location and progressive stiffness springs with damper at the rear-axle showed a significant improvement in ride comfort. No significant improvement was observed from different damper configurations in the front suspension. Thus, the ride comfort was enhanced with minimal changes only in the rear-axle suspension design parameters and optimization of vehicle hitching point geometry during the development of new vehicle application. It has been proposed to select variables through simulation, optimize the number of test configurations using orthogonal array and make an objective evaluation of the ride impact progressively based on successive test results. [ABSTRACT FROM AUTHOR]

The article deals with assessment of railway wagon suspension characteristics. The essential characteristics of a suspension are represented by the stiffness constants of the equivalent springs and the eigen frequencies of the oscillating movements in reference to the main central inertia axes of a vehicle. The premise of the experimental determination of these characteristic is the knowledge of the gravity center position and the knowledge of the main central inertia moments of the vehicle frame. The vehicle frame performs the general spatial movement when the vehicle moves. An analysis of the frame movement generally arises from Euler's equations which are commonly used for the description of the spherical movement. This solution is difficult and it can be simplified by applying the specific assumptions. The eigen frequencies solutions and solutions of the suspension stiffness are presented in the article. The solutions are applied on the railway and road vehicles with the simplifying conditions. A new method which assessed the characteristics is described in the article. [ABSTRACT FROM AUTHOR]

The vortex gripper is a new kind of non-contact gripper, which generates negative pressure by blowing compressed air into a vortex cup through two tangential nozzles. It can provide an adequate suction force for handling a workpiece without contact. This gripper can avoid the disadvantages of traditional gripping devices, such as inducing mechanical scratches, local stress concentration, frictional static electricity, and blots on the workpiece. In this study, we experimentally and theoretically investigated the effect of supply flow rate on the performance of the vortex gripper. First, we proposed three performance indexes for evaluating the properties of the vortex gripper: the maximum force, suspension region, and suspension stiffness. Then, we obtained a series of F–h (i.e., the suction force against the spacing between the gripper and the workpiece) curves at different supply flow rates and the pressure distributions at the surface of the workpiece for different values of spacing h . Based on the experimental data, we analyzed the effect of the supply flow rate on the maximum force, and by nondimensionalization of the F–h curves, the changes in the suspension region were assessed. Furthermore, we proposed an additive method of pressure distribution and deduced a simplified theoretical formula for suspension stiffness. In addition, from the perspective of the suspension stability of the workpiece, we evaluated the physical significance of the slope of the F–h curves after nondimensionalization. The findings of this study could help researchers to comprehend the operation of the vortex gripper and provide guidance for implementing the vortex gripper in practical applications. [ABSTRACT FROM AUTHOR]

A three-axis micromachined accelerometer with a proof mass suspended electrostatically in six degrees of freedom was designed and tested to evaluate its performance of this sensitive sensor for potential microgravity space applications. The device is based on a glass/silicon/glass bonding structure, fabricated by bulk micromachining process, and operated with force-balance technology. The motion of the proof mass with respect to each side is fully servo-controlled by capacitive position sensing and electrostatic force feedback. The design and simulation of multiaxis suspension control loops are presented based on the stiffness requirements for different full-scale ranges. The ground test of this sensitive accelerometer is facilitated by setting the vertical axis at a relatively high measurement range to counteract the one-g gravity, whereas the range in two lateral axes can be set as low as possible to achieve high sensitivity. Detailed experimental results of electrostatic suspension, threeaxis accelerometer, and its cross-axis sensitivity are presented with the device operated initially in an atmospheric environment. The preliminary test results of a prototype accelerometer show that a sensitivity up to 688.8 V/g and a noise density down to 3 μg/Hz1/2 can be achieved by setting an extremely low full-scale range of ±2.90 mg. The results also show that much different stiffness levels in the design of three-axis suspension is a major source of cross coupling effects in the prototype accelerometer. [ABSTRACT FROM PUBLISHER]

A new structure of superconducting suspension system is proposed based on a method used to calculate the magnetic field in a thin clearance between superconducting blocks. Force characteristic of the passive superconducting suspension system is analysed. Based on the existing structure of superconducting suspension system, an electrostatic suspension system is introduced to obtain high suspension stiffness. Details of the hybrid suspension system are introduced and the corresponding controller is also described. This paper provides a theoretical guidance for the next experiment, and also has reference to designing high stiffness suspension system. [ABSTRACT FROM AUTHOR]

A mathematical model of a railway carriage moving on tangent tracks is constructed by deriving the equations of motion concerning the model in which single-point and two-point wheel-rail contact is considered. The presented railway carriage model comprises of carbody and front and rear simple conventional bogie with two leading and trailing wheelets attached to each bogie. The railway carriage is modeled by 31 degrees of freedom which govern vertical displacement, lateral displacement, roll angle and yaw angle dynamic response of wheelset whereas vertical displacement, lateral displacement, roll angle, pitch angle and yaw angle dynamic response of carbody and each of the two bogies. Linear stiffness and damping parameters of longitudinal, lateral and vertical primary and secondary suspensions are provided to the railway carriage model. Combination of linear Kalker's theory and nonlinear Heuristic model is adopted to calculate the creep forces in which introduced at wheel and rail contact patch area. Computer aided-simulation is constructed to solve the governing differential equations of the mathematical model using Runge-Kutta fourth order method. Principle of limit cycle and phase plane approach is applied to realize the stability and to evaluate the concerning critical hunting velocity at which railway carriage starts to hunt. Numerical simulation model is used to study the dynamic responses of a railway carriage bogie subjected to specific parameters of wheel conicity and primary suspension characteristics. A comparison to study the sensitivity of railway carriage bogie to dynamic responses is also presented at different vertical primary suspension stiffness parameters. [ABSTRACT FROM AUTHOR]

Based on a method used to calculate the magnetic field in a thin clearance between superconducting blocks, this paper analyzes the force characteristics of the superconducting suspension system. The superconducting suspension system is stable even without feedback control. Linear feedback control is still introduced to improve the suspension stiffness. Then, the corresponding controller is designed, and many details about the operating conditions are also analyzed. Simulation results show the feasibility of this model. This paper provides a theoretical guidance for the next experiment and also has reference meaning to the supporting system of the superconducting accelerometer, gradient meters, flywheel, and so on. [ABSTRACT FROM AUTHOR]

This paper addresses the effects of pitch static attitude (PSA) and roll static attitude (RSA) on air bearing slider steady performance, especially for ultralow flying height sliders. We performed simulations for three different low flying sliders with flying heights (FHs) of 7 nm, 5 nm, and 3.5 nm using the static simulator code of the Computer Mechanics Laboratory. We found that PSA and RSA have quite significant effects on the steady performance these air bearing slider designs, and the effect is more important the smaller the size and the lower the FH of the slider We also investigated the effects of suspension stiffness on the air bearing sliders' flying attitude (pitch and roll) and found that these effects are similar to those of PSA and RSA. [ABSTRACT FROM AUTHOR]

A simple two-degree-of-freedom (2DOF) model is used to derive a number of analytical formulae describing the dynamic response of railway vehicles to random excitations generated by vertical track irregularities. The dynamic response is given in terms of standard deviations of a number of relevant performance indices such as body-bogie suspension stroke and body acceleration. The derived analytical formulae can be used either during preliminary design or for other special purposes, especially when approximated results are acceptable. An estimation of the degree of approximation offered by analytical formulae is attempted and the results seem satisfactory. By inspection of the analytical formulae a parameter sensitivity analysis may be readily performed. In the second part of the paper, an optimization method for the improvement of the dynamic behaviour of railway vehicles is introduced. The method, based on multiobjective programming (MOP), is a general one and can be exploited for many engineering purposes. In the paper the method has been applied with the aim of achieving the desired trade-off among conflicting performances such as standard deviation of the body acceleration versus standard deviation of the secondary suspension stroke. As a result, new analytical formulae defining the settings of some relevant vehicle suspension parameters have been derived. [ABSTRACT FROM AUTHOR]