Mass-Spring System - Railway Pro

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3How a Mass-Spring SystemFunctionsEffectively isolatingvibrationsThe goal of vibration isolation is todynamically decouple the superstructurefrom its environment in order toreduce the transmission of vibrationsand structure-borne sound.This decoupling is achieved by creatinga system capable of vibration. Ifa permanently elastic spring layer, suchas Sylomer® or Sylodyn®, is installed,the isolation takes place directly at thesource of the emissions. This ensuresthat the support point force F u(t) issmaller than the exciter force F e(t), resultingin reduced vibrations producedby the support point forces.mcF e(t)dF u(t)The function of an elasticallysupported superstructure can bedescribed very easily using an alternatesystem, referred to as a singledegree of freedom system. Manyvibration problems can be approximatelyexplained with this simplephysical model. If the superstructuremass is brought out of equilibrium bya brief exciter force F e(t), the massexecutes vibrations with the naturalfrequency f 0.c = dynamic spring stiffnessm = superstructure mass +unsprung mass of wheelset6
The speed with which these vibrationsdecrease in amplitude dependson the damping of the spring.For Sylomer® and Sylodyn® materials,the damping is described by themechanical loss factor.The amplitude frequency response(amount of transmission function) mustbe determined in order to evaluate amass-spring system. This describes theamplitude relationship based on thefrequency f or based on the frequencyrelationship between the support pointforce F u(t) and the exciter force F e(t) inthe case of source isolation.Load transmission factor V R3.02.52.00.10.20 00.3Two areas exist in the vibrationisolation system, specifically anamplification area and an isolationarea.The amplification only occurs if anexciter frequency is present thatmatches the natural frequency of theelastic support or in the case ofbroadband stimulation.The isolation starts at a frequency thatcorresponds to 2•f 0. The amplitudefrequency response indicates that theamplification at the insulator naturalfrequency f 0is reduced with an increasinglevel of damping, while the level ofisolation decreases with increasingdamping.In terms of the properties of the springin a mass-spring system, this meansthat the system must have the lowestpossible ratio of dynamic to staticstiffness. The dynamic stiffness of thesupport should also only be subject tominor changes due to frequency andload.The dimensioning of a mass-springsystem is an optimization problem forengineers. This problem requiresin-depth and specialized knowledge,such as that which Getzner has offeredwith its partners for years. The functioningof a mass-spring system can,however, be greatly affected by standingwater under the mass trough andwithin the system. When installing amass-spring system, it is thereforeessential to ensure sufficient long-termdrainage.1.50.50.81.0=1.00.80.3 0.50.50.20.10.00.3 0.4 0.6 0.8 1 2 2 3 4 5 6 7 8Tuning ratioAmplificationIsolation7
Page 4 and 5: 2Highly EffectiveStructure-Borne No
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Mass-Spring System - Railway Pro

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