Ergonomic characteristics and operator body fatigue against two-wheel tractor vibration

ABSTRACT: Power tillers are very simple and versatile machines with large scale diffusion in developing countries, where they are commonly used both for agriculture and for transportation purposes. The operators of these kinds of machinery are exposed to high levels of hand transmitted vibration. Long time working with this machinery cause dynamic disorders, damaging different part of the body such as: earache, spine and digestion disorders and vascular disease,investigated throughout experiments that conducted at five engine speeds(1400, 1600, 1800, 2000 and 2200 rpm) and three axes (vertical (z), lateral (y) and longitudinal (x)) in three position on engine, handle grip and operators body. The recorded digital time domain signals, were converted to frequency domain and then 1/3 octave spectrum of vibration acceleration was calculated. The amount of vibration damage on operatorʹs body were determined. The results showed that the vibration acceleration increased with increasing the engine speed. The vibration acceleration was the highest values at vertical direction for all of the experiments. The total weighted acceleration has the maximum value at the frequency of 16, 31.5 and 60 Hz with the vibration amplitude reach up to 7.3, 6.95 and 5.8 m/s2 respectively in handle grip and at the frequency of 6.3, 16 and 31.5 with the vibration amplitude reach up to 0.06, 0.16 and 0.07 m/s2 respectively in chest of operator. The mean value of total vibration acceleration in low frequencies, which is the most sensitive frequency of hand- arm system, has considerable values. At frequencies above 40 Hz in operator chest position for all engine speeds, the acceleration values are less than 1 m/s2 and in handle position frequencies above 100 Hz the acceleration values are less than 1 m/s2. The handle vibration at specific frequencies and at high engine speeds was greater than the allowable amount for the Comfort limit and some desease and symptoms like headache, Influence on speech and Lump in the throat could be appeared.