Study on the Effect of Damping Asymmetry of the Vertical Suspension on the Railway Bogie Vibrations

Mădălina Dumitriu

doi:10.3390/sym14020327

Abstract

This paper has an original approach to the study of vibrations in the bogie of the railway vehicle by taking into account the asymmetry of the vertical damping of suspension. The study relies on the results derived from the numerical simulation applications, where the damping asymmetry of the bogie suspension is simulated through different degrees of reducing the damping of the suspension of one of the wheels compared to the reference value. Under such circumstances, the vibrations behaviour of the bogie, assessed in five reference chassis points—four points located against the suspension of each wheel and one point located against the bogie’s center of mass—will be the result of several combined effects. A first effect is produced by the suspension asymmetry that trigger interferences between the vertical vibrations of bounce and pitch and the horizontal roll vibrations of the bogie. Another effect is introduced by the reduction of the damping in the system. To these, the geometric filtering effect due to the bogie wheelbase is added, which has a selective nature depending on velocity. The analysis of the bogie vertical vibrations aims to assess the level of vibrations and identify the dominant vibration mode in the bogie reference points, as well as to determine the critical point of the vibration mode of the bogie, in correlation with velocity and the reduction degree of the suspension damping.

Highlights

From a mechanical perspective, the railway vehicle represents a complex oscillating system, which features a vibrations behaviour with specific characteristics
This section introduces the results of the numerical simulations regarding the power spectral density of acceleration and the root mean square of acceleration in the bogie reference points, based on which the characteristics of the bogie vibrations behaviour and the effect of the vertical suspension damping asymmetry are being studied
The paper studies the effect of the asymmetry of the vertical suspension damping on the vibrations behaviour of a two-axle bogie, which can be triggered by the depreciation of the characteristics of the dampers during exploitation

Summary

Introduction

The railway vehicle represents a complex oscillating system, which features a vibrations behaviour with specific characteristics. The previous research studies dedicated to the assessment of the behavior of vertical vibrations of the bogie to the failure of a damper in the primary suspension of the vehicle, developed on the basis of a simplified model with two degrees of freedom—bounce and pitch, have shown that the asymmetry of the vertical damping of suspension introduces an imbalance in the system [22,26] This imbalance leads to dynamic interferences between the bounce and pitch vertical vibrations of the bogie, which are decoupled for the symmetrical damping of suspension. The roll vibrations of the bogie are not excited, as per the equation below: Jb b 4b2c b 4b2k b 0

The Calculation of the Frequency Response Functions of the Bogie

Analysis of the Vibrations Behaviour of the Bogie

Results and Discussion

The Study of the Characteristics of the Bogie Vibrations Behavior

Conclusions