Spectral analysis of a standard test track profile during passage of an agricultural tractor

Abstract

National statistics on work safety are pointing out a decreasing trend about related injuries and fatalities but an increasing number of reports about professional diseases. In this frame are also considered the mechanical vibrations, in particular whole-body vibrations (WBV). This study aims to reproduce and analyse the vertical displacement of the wheel of an agricultural tractor during the passage on a standard surface (ISO 5008) for defining potential correlations between the surface contour and the effects on vehicle dynamic and driver comfort by analysis of the signals acting under the tractor tires. An agricultural tractor, in four setting conditions and four different forward speeds, was tested on an ISO 5008 standard test track. The accelerations at the hubs of the tractor were acquired and subsequently reproduced on a four hydraulic actuators test bench, at CRA-ING laboratories, Treviglio, Italy. The analysis of the spectrums generated have shown that a roughness surface induces a transformation of the part of energy developed by the forward speed of the vehicle in vertical acceleration that excites the elastic parts (i.e. tires, suspensions). These phenomena seem to indicate that vehicle’s vibration entity is due to the combination of surface roughness and forward speed as amplitude and to the elastic properties of the vehicle as frequency.