Effect of the using foam and sponge in seat pan on transmission of vibration to driver body

Transmission of mechanical energy from vibration source to human body has different effects, such as reduced efficiency, skeletal lesions, disorder in the comfort, physiological and psychological problems. The lack of suspension systems on agricultural machines has causedthat the operators of agricultural machinery to be exposed to a wide range of vibrations indirectly. Use of suitable seat foam is one solution to reduce the vibrations. In this study, the vibration transmission of Polyurethane foam or sponge and effect of various factors for reducing vibrations is investigated. Therefore, different types of foam and sponge with a thickness of 6, 8, 10 and 12 cm, and densities of 12.5, 20, 30 and 50 kg/m3 were exposed to the vibration. Also the passenger mass and stimulation acceleration in three different levels were applied to the samples. Acceleration Data were records and the experimantal analyses were then performed with SPSS and MATLAB software. The results showed that vibration transmissibility of the cold foam was less than that of hot foam (about 10%). Considering the Anthropometrics data and the range of tractor operators mass in Iran (72-90 kg), and also due to the principles of ergonomics, the use of cold foam with a density of 50 kg/m3 (transferability of 26%), the thickness of 8-10 cm in acceleration of 3-4 m/s2 (transferability of 17%) is the most appropriate choice for the machines with high vibration seat.