Vibration characteristics of tractor seat cushion materials

Operators of agricultural machinery are exposed to an extensive range of indirect vibrations through the seats, which gradually causes chronic damages. One of the ways to reduce the vibrations imposed on the operators is to use appropriate materials in tractor seat cushion. The present study was carried out in order to select appropriate foam or sponge and investigate different factors in reducing vibrations imposed on operator’s body so as to promote drivers health and enhance their working efficiency. Vibration experiments were performed at different accelerations on foam and sponge materials at different thicknesses and densities for different occupant masses, and the input and output acceleration signals were recorded and analyzed. Using the analysis of variance, analysis of the mean squares of the input and output acceleration, the type of material used in the seat cushion and the effect of different factors on them were investigated. The results showed that in reducing vibrations, sponge for mass of 90 kg and more and foam for mass of 75 kg and less were more efficient. The sponge was also suitable for acceleration of excitation above 6 ms2and foam for acceleration of excitation above 3 ms2 and below. Therefore, according to the working conditions of agricultural machines and anthropometric characteristics of Iranian drivers and the appropriate suitable thickness of the seat cushion (68 cm), it is recommended that their seat cushion be made of a combination of foam and sponge with high density and thickness of 8 cm.