Damping characteristics of seat cushion materials for tractor ride comfort

The cushioning material in a tractor seat plays a dominant role in supporting operator posture, isolating vibration and improving ride quality. Vibration attenuation in a tractor seat is achieved by selecting proper suspension and damping mechanism. This paper describes damping characterisation of tractor seat cushion materials to improve operator’s comfort. Nine commercially available seat cushion materials of different densities, thickness and compositions were selected for the study. A sinusoidal displacement exciter was designed to measure damping characteristics of the seat cushion materials in the frequency range of 1–8 Hz with displacement amplitudes of 10, 15 and 20 mm peak-to-peak. It was observed that the equivalent viscous damping coefficient (Ceq) of cushion materials decreased with the increase in frequency and peak-to-peak amplitude of vibration and decrease was very sharp in the lower frequency range up to 3 Hz. The average percentage reduction in Ceq increased with increase in peak-to-peak amplitude of vibration from 10 to 20 mm for the selected seat cushion materials. The average percentage reduction in Ceq was the highest for thinner high density polyurethane (PU) foam (thickness of 44 mm, density of 19.09 kg/m3) at different frequencies of vibration. It may be concluded that the high density PU based cushion material is good for dampening vibrations transmitted in tractor under dynamic condition.