The effect of anti-vibration material on whole-body vibration exposure via the cabin floor

Transcription

1 Ref: C0576 The effect of anti-vibration material on whole-body vibration exposure via the cabin floor Dimitrios Kateris, Ioannis Gravalos, Theodoros Gialamas, Panagiotis Xyradakis, Anastasios Georgiadis and Roxana Agarici, Technological Educational Institute of Thessaly, School of Agricultural Technology, Department of Biosystems Engineering, Larissa, Greece Abstract The aim of this study is to present and analyze the vibration in the cabin floor of agricultural tractor in different driving conditions with or without anti-vibration material on cabin floor. A Pulse system type 3560C with 17-channel (Brüel & Kjaer) was used for data acquisition. Two triaxial accelerometer (model 5424B) and four monoaxial accelerometer (model 4533B) were placed at selected points on the cabin floor. An investigation of three case studies took place: a) the agricultural tractor was stationary and the engine was operated at different speeds ( rpm), b) the tractor was moving in road at two different speeds (6 and 20 km/h) and c) the tractor was moving in the field (6 km/h). Data measurements were performed on the tractor cabin floor using sampling frequency of Hz. The data were collected for 30 sec for each tractor operation case with two series of sampling for each surface and speed. The results show that the use of an anti-vibration material can significantly reduce the wholebody vibration via the cabin floor to the operator body. At the same time the use of such materials can increase the working hours and increase the efficiency in each cultivation operation. Particular attention should be given to the material texture which should not prevent the operator s movements. Keywords: agricultural tractor, vibration, cabin floor, anti-vibration material 1 Introduction An agricultural tractor is exposed to vibration caused by moving engine elements, and unevenness of soil profile (Scarlett et al., 2007). Operator of agricultural tractor under whole body vibration exposure (during ploughing and harrowing operations) cans result severe discomfort and health problems. The effects of vibration on the health of tractor operator on the basis of frequency up to 2 Hz causing discomfort problems, such as: exhaustion, headache, nausea, vomiting, inability, weakening, and vertigo. Vibration influence at frequencies from 2 to 80 Ηz causing: skeleton alterations, digestive system disorders, changes in the urinary and genetic system (Tiemessen et al., 2007; Zehsaz et al., 2011). The cabin floor and seat are the main transmission paths of vibration to the tractor operator s body. Therefore, it is necessary to study the vibration behavior of cab floor and seat in detail. Hoshino et al. (2003) investigated the load transfer paths in the cabin structures of heavyduty trucks under static loading. A simple mass-spring model developed for vibration analyses. Load path analyses shown that the low stiffness of the cross-member caused by discontinuities and nonuniformities in the paths. Fredӧ & Hedlund (2004) shown that the truck cabin floor optimization (plate segments that were stiffer than the main beam structure) had better vibroacoustic performance. Hostens & Ramon (2003) found in the cabin of a combine that an increase in driving speed results an increased whole body vibration. Another study by Oude Vrielink (2009) indicates that for many agricultural tractors, driving at high speed Proceedings International Conference of Agricultural Engineering, Zurich, /8

2 (25km/h) leads to unacceptably high vibration, while driving at low speed (15km/h) are vibration values acceptable. Loutridis et al. (2011), in their study was focused on the effect that the electronic engine speed regulator has on tractor ride vibration levels. It seems that electronic regulation has an advantage when used in typical field tasks such as cultivating. An effective remedial measure is to reduce the vibration transmitted through cabin floor and seat, by means of low-pass mechanical filters, active vibration control systems, and passive isolation systems (anti-vibration materials). For a vibration-isolation seat, the spring and damper represent mechanical filters supporting the seat pan and operator. An active vibration control system, which consists of actuator, vibration sensor, and electronic controller, can possess safety interlocks to ensure it does not generate harmful vibration at the seat pan (Brammer & Peterson, 2004). Unfortunately, vibration isolation systems are not provided for the handles and cabin floor of old agricultural tractors. For tractor handless (steering wheel, gear shift lever) there have been attempts to apply the principle of vibration isolation to gloves, and so called anti-vibration gloves are commercially available. In a vibration-isolated cabin floor the operator s feet are decoupled from the metal floor. The incorporation of an elastic layer made of precisely engineered isolation pad results in significantly better isolation of the dynamic forces acting on the cabin floor. In this study, the goal is to investigate the efficiency of anti-vibration material, as a passive isolation system, to protect the cabin floor against disturbing vibration caused by an old wheeled tractor during their operation. 2 Materials and methods In this paper, a relatively old wheeled tractor (Renault 461) was used for the experimental tests. An investigation of three case studies took place: a) the agricultural tractor was stationary and the engine was operated at different speeds ( rpm), b) the tractor was moving in road at two different speeds (6 and 20 km/h) and c) the tractor was moving in the field (6 km/h). In each case study was measured the acceleration in cabin floor with and without the anti-vibration material. During the experimental process, the Pulse system type 3560C with 17-channel (Brüel & Kjaer) (Figure 1) and PSV-400 scanning laser vibrometer (Polytec) (Figure 1), were used to measure acceleration and displacement on cabin floor respectively. Figure 1: The Pulse system type 3560C with 17-channel (Brüel & Kjaer) and the PSV-400 scanning laser vibrometer (Polytec). At the beginning were selected six different points on the cabin floor. In particular, three points at the left side (Figure 2) and three points at the right side (Figure 2) on the cabin floor. In these points were placed two different types of accelerometers. In points No.2 and No.5 (Figures 2 & 2) were placed two triaxial accelerometers (model 5424B) (Figure 2(c)) and in points No and 5 (Figures 2 & 2) four monoaxial accelerometers (model 4533B) (Figure 2(d)). Proceedings International Conference of Agricultural Engineering, Zurich, /8

3 (c) (d) Figure 2: & The points were placed the accelerometers on the cabin floor, (c) a triaxial accelerometer model 5424B (Brüel & Kjaer) and (d) monoaxial accelerometer model 4533B (Brüel & Kjaer). All signals, a total of 10 channels (3 channels per triaxial and 1 channel per monoaxial accelerometer), obtained from the accelerometers were lead into Pulse system type 3560C with 17-channel (Brüel & Kjaer). The Pulse system was used for data acquisition. Then, the signals were stored on a personal computer (Laptop) via a LAN cable at a sample frequency of Hz and measurement duration 30 sec. The PSV-400 scanning laser vibrometer was used to measure displacement of predefined points on the cabin floor. This devise is a non-contact transducer for the displacement measurement of vehicles components. It is based on the laser- Doppler effect, and it is equipped with the computer controlled orientation system. It is inherently a sequential procedure making a set of point measurements. A camera is used to view the all cabin surface. The engine speed is accurately recorded with a tachometer. 3 Results and Discussions The values of the maximum acceleration on cabin floor without and with anti-vibration material at the selected points in different engine speeds are reported in Table 1 and Table 2. In general, it is obvious that the maximum values of acceleration in all cabin floor points are significant lower with the anti-vibration material. The acceleration values at the right side of the cabin floor are lower than the left side. It is probably due to the cabin structure. Analytically, in Figures 3 to 3(f) were presented comparatively the maximum acceleration values in three points for each cabin floor side for 800, 1600 and 2200 rpm. The results indicate that there is no significance difference between different engine speeds at the same cabin floor condition (e.g. with anti-vibration material) but there is a great difference between different cabin floor condition (with and without anti-vibration material) at the same engine speed. This immediately leads to the conclusion that the anti-vibration material interrupts the transmission paths of vibration to the tractor operator s body. When the engine speed increased the maximum acceleration value in each of the two cabin floor condition is increased also. At the left side of the cabin floor the maximum acceleration value appears at the frond side of cabin floor (point No.4) in all the speed values, with or without anti-vibration material. But at the right side the maximum acceleration value appears at the middle of cabin floor (point No.2) in all the speed values, with anti-vibration material. Proceedings International Conference of Agricultural Engineering, Zurich, /8

4 Table 1: Maximum acceleration values on cabin floor without the anti-vibration material in different engine speed (stationary). Engine Speed (rpm) No.2 Maximum Acceleration (m/s 2 ) No.5 No.1 No.3 No.4 No.6 Z X Y Z Z Z X Y Z Z Table 2: Maximum acceleration values on cabin floor with the anti-vibration material in different engine speed (stationary). Engine Speed (rpm) Maximum Acceleration (m/s 2 ) No.2 No.1 No.3 No.4 No.5 Z X Y Z Z Z X Y Z Y No.6 (d) Proceedings International Conference of Agricultural Engineering, Zurich, /8

5 (e) (c) (f) Figure 3: The maximum vertical (Z) acceleration in selected six points on cabin floor 800 rpm, 1600 rpm, (c) 2200 rpm with and without anti-vibration material (cabin floor left side), (d) 800 rpm (e) 1600 rpm and (f) 2200 rpm with and without anti-vibration material (cabin floor right side). In Figures 4 to 4(d) were presented comparatively the acceleration values in three axis X, Y, Z at two points (No. 2 and No. 5) for each cabin floor condition (with or without antivibration material) for 800, 1600 and 2200 rpm. In point No. 2 (Figure 4 and 4(c)) and for cabin floor condition without anti-vibration material, the maximum acceleration value appears in axle Z for the all engine speeds but with anti-vibration material the maximum value appears in axle X. In point No. 5 (Figure 4 and 4(d)) with the same cabin floor condition, the maximum acceleration values appear exactly opposite behaviour. It is probably due to the anti-vibration material structure. Proceedings International Conference of Agricultural Engineering, Zurich, /8

6 (c) (d) Figure 4: The maximum acceleration values in different axles (X,Y,Z) in positions No 2 without anti-vibration material (cabin floor right side), No 5 without anti-vibration material (cabin floor left side), (c) No 2 with anti-vibration material (cabin floor right side), (d) No 5 with anti-vibration material (cabin floor left side). In Figures 5 and 5 were presented comparatively the maximum vertical Z acceleration in the selected six points on cabin floor in different operating conditions (road at 6 km/h, road at 20km/h, and field at 6 km/h) for cabin floor right side and for cabin floor left side respectively. It is obvious that the right side of the cabin floor has the greatest maximum vertical accelerations in all conditions. Also, once again the use of anti-vibration materials helped to interrupt the main transmission paths of vibration. In point No. 5 (Figure 5) and for cabin floor without anti-vibration material the greatest maximum vertical acceleration value appears for all three cases. The results indicate that accelerations are increased when the tractor is moving at a speed of 20 km/h versus the speed of 6 km/h except in point No 5 in cabin floor condition without anti-vibration material. It is confirmed by study of Oude Vrielink (2009). When the tractor is moving in the field at a speed of 6 km/h, the maximum vertical acceleration increased in all selected points versus tractor is moving in the road at the same speed, except in position No 5 in cabin condition without anti-vibration material also. The point No. 5 appears high maximum vertical acceleration due the design of the cabin floor (less stiffness). Figure 5: The maximum vertical (Z) acceleration in selected six points on cabin floor in different conditions cabin floor right side cabin floor left side. Figures 5 to 7 depict examples of the cabin floor displacement patterns, the agricultural tractor was stationary and the engine was operated at different speeds 800, 1400 and 2000 rpm. Comparing Figures 5 and 5 and Figures 6 and 6, it can be seen that the exist- Proceedings International Conference of Agricultural Engineering, Zurich, /8

7 ence of the anti-vibtration material reduces slightly the displacement at the investigated surface. When the engine speed takes high speed values (2000 rpm) the differentiation between the two cabin floor conditions is more than obvious (Figures 7 and 7). Therefore, the anti-vibration material, as a passive isolation system, protects the cabin floor against disturbing vibration at high engine rpm. Figure 5: Cabin floor displacement in 800rpm without anti-vibration material and with antivibration material on cabin floor. Figure 6: Cabin floor displacement in 1400rpm without anti-vibration material and with antivibration material on cabin floor. Figure 7: Cabin floor displacement in 2000rpm without anti-vibration material and with antivibration material on cabin floor. Proceedings International Conference of Agricultural Engineering, Zurich, /8

8 4 Conclusions A large part of the agricultural tractors fleet includes tractors older than 15 years. These tractors show significant vibration values in cabin floor. This shortcoming should be overcome by additional measures. An easy and inexpensive solution is the installation of low cost additional materials on the cabin floor in order to absorb the vibrations. This study showed that it is possible with materials which are easy to find on the market and there cost isn t so high. From the test results, the following conclusions can be drawn: In an attempt to improve vibration damping, attention should be given to the effectivity of the cabin floor. It should be placed materials demonstrably achieve vibration damping. The maximum values of acceleration in all cabin floor points are significant lower with the anti-vibration material. The acceleration values at the right side of the cabin floor are lower than the left side. It is probably due to the cabin structure. The cabin floor without anti-vibration material shows increased displacement in 2000 rpm compared to the case of 2000 rpm with anti-vibration material. In the other two cases this differentiation is not so obvious. 5 References Brammer, A.J., & Peterson D.R. (2004). Vibration, mechanical shock, and impact. New York: McGraw-Hill, (Chapter 11). Fredö, C.R., & Hedlund A. (2004). NVH optimization of truck cab floor panel embossing pattern. SAE International, , 1-7. Hoshino, H., Sakurai, T., Takahashi, K. (2003). Vibration reduction in the cabins of heavyduty trucks using the theory of load transfer paths. JSAE Review, 24, Hostens, I., & Ramon H. (2003). Descriptive analysis of combine cabin vibrations and their effect on the human body. Journal of Sound and Vibration, 266, Loutridis, S., Gialamas, Th., Gravalos, I., Moshou, D., Kateris, D., Xyradakis, P., & Tsiropoulos Z. (2011). A study on the effect of electronic engine speed regulator on agricultural tractor ride vibration behavior. Journal of Terramechanics, 48, Oude Vrielink, H.H.E. (2009). Exposure to whole-body vibration and effectiveness of chair damping in highpower agricultural tractors having different damping systems in practice. Report ErgoLab Research BV & Profi, 46 pp. Scarlett, A.J., Price, J.S., & Stayner R.M. (2007). Whole-body vibration: Evaluation of emission and exposure levels arising from agricultural tractors. Journal of Terramechanics, 44, Tiemessen, I.J., Hulshof, C.T.J., & Frings-Dresen, M.H.W. (2007). An overview of strategies to reduce whole-body vibration exposure on drivers: A systematic review. International Journal of Industrial Ergonomics, 37, Zehsaz, M., Sadeghi, M.H., Ettefagh, M.M., & Shams, F. (2011). Tractor cabin s passive suspension parameters optimization via experimental and numerical methods. Journal of Terramechanics, 48, Proceedings International Conference of Agricultural Engineering, Zurich, /8