Evaluation of Whole-body-vibration Among Tractor (41 kW) Drawn Subsoilers

Whole-body-vibration can be say to that part of vibration which received by a person’s body, from the machine. Subsoiling is heavy draft farm operation so to know the effect of subsoiling on vibration, it needs documentation which helps to decide safe exposure limits in sense of duration of safe subsoilling hours. For study, three subsoilers as single tine straight shank subsoiler (S1), double tine straight shank subsoiler (S2), and double tine curved shank subsoiler (S3) at three different depths (20-25, 25-30, and 30-35 cm) performed subsoiling and evaluated the effect of subsoiling on different parameters as vibration, fuel consumption, wheel slip, draft, and soil disturbance area were observed and analyzed. The vibration was increased as operating depth was increased. It was recorded maximum at depth of 30-35 cm (d3) for “X” direction as 0.296 m/s2, for “Y” direction as 0.284 m/s2, for “Z” direction as 0.431 m/s2, and for total acceleration (Ahv) as 0.451 m/s 2. The vibration in “X” direction was increased 5.86 % and 11.64 %, in “Y” direction was increased 6.52 % and 12.42 %, in “Z” direction was increased 3.68 % and 8.11 %, and Ahv was increased 10.23 % and 13.59 %, for d2 and d3 depths compared to d1 depth. On the other hand, the fuel consumption, wheel slip, and draft were found maximum for S2 subsoiler and minimum for S1 subsoiler. Soil disturbance area was observed maximum for S2 subsoiler and minimum for S1 subsoiler. Also same effect as vibration, the increased subsoiling depth resulted increased in these parameters. The safe exposure working hours were calculated as work with S1 subsoiler at the depths of d1, d2, and d3 were 8 h, 6 h, and 4 h respectively. Same as for S2 subsoiler were 4 hours at all depths and for S3 subsoiler it was calculated 4 to 6 hours. In conclusion, single tine subsoiler can be a better option for subsoiling. Only the soil disturbance area and field capacity becomes half as compared to double tine subsoilers. keywords: whole-body-vibration, subsoiling, vibration database, safe exposure period.

inTRODuCTiOn With invention of internal combustion engines and further advances in engine technology, the problem of un-necessary sound and vibration are arisen. Vibration enters the human body from the organs in contact with vibrating surface. When a worker sits or stands on a vibrating surface, the contact among both is called whole-body-vibration exposure. Many people are exposed to vibration (WBV) in their occupational lives. The biodynamic responses of the human body in sitting conditions have been widely measured under whole-body vibration (WBV) 4 . Working with agricultural machine in farm operation, the important thing in manmachine interference is ergonomic as human health. Obviously exposing high level vibration and more than allowable time of operation affect the health as damaging different part of body and consequently decreasing efficiency and quality of work 8 .
Vibration is the mechanical oscillation of an object about an equilibrium point. normally, the agricultural tractor produces low-frequency vibrations and it affects severe to human body. These vibrations are depended on various parameters such as as soil type, field operations, tractor mass distribution, engine speed and forward speed 5,7,9] . In view of the deterioration in health and working efficiency base on vibration, it is necessary to study the effect of vibration transmission to the vehicle seat 6 . Most of the past work on vibration align with tractor is only done as riding tractor and study the vibrating effect on running tractor. But the use of tractor is mostly with implement working in field and trailer working 1 .
Based on the feedback from the tractor drivers operating subsoilers complained about severe fatigue after working few hours. This needs a documentation /database. neither the effect of implements on tractor ride vibration is well understood, nor is the effect of tractor ride vibration on operator's effectiveness and health. To know this effect of vibration characteristics of implement as different subsoilers, working depths, and particular safe working period, this present study was undertaken. The human vibration data collection for subsoilers working at different depths and to analyze the effect of the experiment on the transmissions of human vibration to operator helps to work-out the schedule of safe / harmful exposure limits can be determined. It can be find out by comparing the vibrations values with the limits of tri-axial acceleration set by the International Standards ISO:2631-5(2004) 3 and total exposure acceleration by the EU Directive 2002/44/EC. 2002 2 . By comparing these data with standards, one can decide the safe working hours of subsoiling operation for individual three subsoilers at respective depths.

mATERiALS AnD mEThODS
For this experimentation mature, the performance was evaluated with 41 kW tractor John Deere -5310 and three subsoilers. To measure the parameters like whole-body-vibration, fuel consumption, wheel slip, draft, and soil disturbance area, the used instruments are human vibration meter VM-30h, fuel consumption measuring device, length measuring tape, digital dynamometer and soil profile meter respectively.

Experimental Site
To perform the experiment, the field of Instructional Farm, Department of Soil and Water Engineering, College of Agricultural Engineering and Technology, JAU, Junagadh was selected.

Experimental Design
The experiment was carried out with two factors and nine combinations as three subsoilers working at three different depths with three replications to study the effect of subsoiling on wholebody-vibration and other parameters.    Fuel consumption (l/h) 3.

Vibration measurement
Vibration (X, Y, and Z direction) acceleration r.m.s. values (Whole-body-vibration) were collected in first run in the plot and the data were saved in vibration meter. It was also collected total vibration (Ahv) values of Whole-body-vibration for same plot in second run and data were saved in vibration meter. Total Vibration Value (Ahv) was determined from vibration in three orthogonal directions and for particular exposure period, it was calculated via instrument software as ; Where, a hwx , a hwy, a hwz are the acceleration interval r.m.s. values for X/Y/Z axes, and k x ,k y ,k z are multiplying factors as 1.4, 1.4 and 1 respectively.  [2] given permissible acceleration value as 1.15 m/s 2 .

RESuLTS AnD DiSCuSSiOn
Results and Discussion describes the experimental testing and functional performance in the field. It also includes the effect of subsoiling on whole-body-vibration, fuel consumption, wheel slip, draft and soil disturbance area. Aimed to vibration, the safe exposure period for operator for subsoiling operation discussed and presented accordingly.

Vibration Parameters
Vibration acceleration r.m.s. (root mean square) and Total acceleration (Ahv) data were obtained for three subsoilers operating at three different depths

Vibration acceleration r.m.s
For analysis, the average value of three replications of Vibration acceleration r.m.s. is presented in Table 2 for individual direction. Limiting acceleration values of whole-body-vibration for particular directions given by ISO:2631-5(2004) 3 are as Table 1. Obtained acceleration data were compared with standard and results showed that how much hours of subsoing in particular condition was beyond the safe working period.

Total Acceleration (Ahv)
For analysis, the average value of three replications of total acceleration (Ahv) was analysed as finding of calculated exposure hours for 8 h, 6 h, and 4 h in Microsoft Excel software. This calculated acceleration is presented in Table 3. European standard "EU Directive 2002/44/EC. 2002" [2] gives the maximum permissible safe limiting value as 1.15 m/s 2 . Obtained Total acceleration (Ahv) data gives the calculated exposure acceleration and these data were compared with European Standard, whose results showed that how much hours of subsoiling in particular condition was beyond the safe working period. Both of the Vibration acceleration r.m.s. and Total acceleration (Ahv) compared with standards and gives same results of safe working hours for particular subsoiling operations.

Operating Parameters
The parameters as fuel consumption, wheel slip, draft, and soil disturbance area were also measured during subsoiling in three replications. The average result is given in Table 5.
The major conclusions drawn from this experiment were;

1.
The vibration was increased as operating depth was increased. It was recorded maximum at depth of 30-35 cm (d 3 ).

2.
The vibration acceleration r.m.s. value in "X" axis was found minimum with single tine straight shank subsoiler (S 1 ). It was increased by 36.79 % and 22.71 % for S 2 and S 3 , respectively than S 1 for maximum depth d 3 .

3.
The vibration acceleration r.m.s. value in "Y" axis was found minimum with single tine straight shank subsoiler (S 1 ). It was increased by 40.11 % and 23.49 % for S 2 and S 3 , respectively than S 1 for maximum depth d 3 .

4.
The vibration acceleration r.m.s. value in "Z" axis was found minimum with single tine straight shank subsoiler (S 1 ). It was increased by 56.22 % and 18.13 % for S 2 and S 3 , respectively than S 1 for maximum depth d 3 .

5.
The total acceleration (A hv ) vibration was found minimum with single tine straight shank subsoiler (S 1 ). It was increased by 31.73 % and 23.28 % for S 2 and S 3 , respectively than S 1 for maximum depth d 3 . 6.
The fuel consumption, wheel slip, draft, and soil disturbance area were also increased as operating depth was increased.

7.
Comparison of safe exposure working period for the operator for subsoiling operation at d 3 depth, safe exposure period of S 1 subsoiler is 6 h, for S 2 subsoiler is 4 h, and for S 3 subsoiler is 4 to 6 h.
Future scope of the work regarding this study is work on whole-body-vibration attenuation may be undertaken and also study of hand arm vibration can be conducted for analysis and finding of safe limiting hours of working.