الخلاصة

Abstract The aim of this research was to assess the WBV that the tractor driver exposed to while carrying out some traditional agricultural operations . The study involved three different investigations conducted at three different sites . Each investigation was considered as a single experiment and carried out individually at four different engine speeds (800, 1000, 1200, 1600) rpm except the plowing site, it was conducted at two speeds only (1200, 1600)rpm . The experimental sites were the stop site for loading or unloading , the transportation site at asphalt road and earthen road with (2WD , 4WD) and plowing site with (2WD , 4WD) . The effect of WBV at the orthogonal axes ( X, Y, Z) , the total vibration of tractor seat Av and the time duration to reach exposure action value EAV and exposure limit value ELV were determined . The vibration was measured and defined in accordance with European Union regulation guide (2002 /44/EC Directive) and the organization of ISO ( ISO – 2631 – 1 – 1997 ) . The results indicated that irrespective of the type of operation , the rms acceleration levels along the longitudinal direction Ax axis was higher than the lateral direction Ay and the vertical direction Az at all speed tested . A strong correlation between the resultant of total vibration Av and Ax axis was found with r equal to 0.97 . The vibration values of Ay and Az axes were below the warning value EAV while the Ax and Av exceeded EAV and approached the risk value ELV in some engine speeds for both stop and transport sites . However; with respect to plowing site all orthogonal axes and Av exceeded the risk value ELV , Therefore, driving the tested tractor over a long period of time lead to a serious health problems and the driver must implement a serious measures . In general, from the health point of view and under the condition in which the research was conducted , the vibration of the tractor cannot be tolerated for more than four hours at the lowest level of vibration of the stop site . While the shortest time of exposure to vibration was 23 minutes during the process of plowing .