Analysing the correlation between vehicle responses and track irregularities using dynamic simulations and measurements

Track irregularities play a key role in vehicle response, but it is not uncommon to find irregularities with similar statistical characteristics giving very different vehicle behaviour. It is therefore important to find a consistent way of describing track irregularities, which better matches the vehicle behaviour to facilitate an efficient track maintenance and vehicle acceptance testing. Various proposals have been made to resolve this issue, although with limited success. In the present paper, a methodology to break down the track–vehicle interaction into steps, by analysing the irregularity–response correlation in detail, is applied to both the measured and simulated data of a passenger coach. The results show a very good agreement and a high correlation coefficient between the vertical axle box acceleration and the second spatial derivative of the vertical track irregularities when analysing the simulated data, but not for the measured data. Parameter variations are carried out through simulations, in which the vertical track stiffness, vehicle unsprung mass, vertical primary suspension and different combinations of track irregularities are varied. The results show that track stiffness mainly affects the axle box acceleration whereas the primary vertical suspension stiffness and unsprung mass predominantly affect the vertical wheel–rail forces. Therefore, it is important to understand the influence of track stiffness, especially with the help of the measured data, and the methods that reduce its influence should be investigated in future works.