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, 41110 Larissa, Greece

e-mail:dkateris@agro.auth.gr

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 heavy-duty 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 (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.

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 sta-tionary and the engine was operated at different speeds (800 -2400

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(a)) and PSV-400 scanning laser vibrometer (Polytec) (Figure 1(b)),

were used to measure acceleration and displacement on cabin floor respectively.

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.

Table 1: Maximum acceleration values on cabin floor without the anti-vibration

material in different engine speed (stationary).

In Figures 5(a) and 5(b) 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(b)) 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 1: (a) The Pulse system type 3560C with 17-channel (Brüel & Kjaer) and (b)

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(a)) and three points at the right side (Figure 2(b))

on the cabin floor. In these points were placed two different types of accelerometers.

In points No.2 and No.5 (Figures 2(a) & 2(b)) were placed two triaxial accelerometers

(model 5424B) (Figure 2(c)) and in points No 1-3-4 and 5 (Figures 2(a) & 2(b)) four

monoaxial accelerometers (model 4533B) (Figure 2(d)).

Figure 2: (a) & (b) 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 65536 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.

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(a) 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.

Engine

Speed

(rpm)

Maximum Acceleration (m/s2)

Position

No.1 Position No.2

Positio

n No.3

Positio

n No.4 Position No.5

Position

No.6

Z X Y Z Z Z X Y Z Z

800 41.5 18.0 19.1 34.4 21.8 55.5 73.4 70.6 77.7 39.9

1000 64.6 25.1 25.7 40.8 38.1 91.5 154.0 106.1 142.6 50.7

1200 68.1 26.1 30.0 54.3 51.8 124.6 185.9 128.8 137.5 66.2

1400 102.5 39.3 40.1 60.6 59.3 132.8 160.3 142.3 166.0 81.6

1600 118.6 38.9 43.9 72.8 64.5 135.0 258.2 156.1 180.2 94.8

1800 161.1 46.7 72.3 87.6 78.5 134.9 233.7 184.5 231.9 113.7

2000 130.1 53.5 65.2 93.8 68.7 192.7 276.0 203.5 237.2 84.2

2200 178.2 50.9 70.8 89.4 110.5 150.5 287.8 199.3 243.7 117.9

Table 2: Maximum acceleration values on cabin floor with the anti-vibration

material in different engine speed (stationary).

Engine

Speed

(rpm)

Maximum Acceleration (m/s2)

Position No.1

Position No.2 Position

No.3

Position

No.4 Position No.5

Position

No.6

Z X Y Z Z Z X Y Z Y

800 4.1 4.6 4.2 5.7 4.5 9.4 2.3 5.7 7.7 3.2

1000 3.1 5.8 6.9 5.3 5.7 17.1 4.1 9.7 10.1 6.8

1200 7.3 7.3 5.9 6.7 4.4 18.9 5.2 9.0 15.9 3.6

1400 6.9 8.6 11.0 6.7 5.5 26.1 7.6 13.6 23.3 7.0

1600 8.3 5.6 6.7 7.0 3.7 12.2 7.9 9.1 19.5 8.8

1800 8.5 10.3 8.8 9.6 6.3 16.7 7.8 13.2 18.7 5.7

2000 7.8 13.7 6.0 8.9 5.1 23.7 7.2 12.9 23.0 5.7

2200 7.9 14.9 10.4 9.1 8.6 17.2 6.7 9.8 16.9 4.9

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.

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, 2005-01-2342, 1-7

Hoshino, H., Sakurai, T., Takahashi, K. (2003). Vibration reduction in the cabins of heavy-duty

trucks using the theory of load transfer paths. JSAE Review, 24, 165–171

Hostens, I., & Ramon H. (2003). Descriptive analysis of combine cabin vibrations and their

effect on the human body. Journal of Sound and Vibration, 266, 453–464.

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Z. (2011). A study on the effect of electronic engine speed regulator on agricultural tractor ride

vibration behavior. Journal of Terramechanics, 48, 139–147.

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 2009-10-1. ErgoLab Research BV & Profi, 46 pp.

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emission and exposure levels arising from agricultural tractors. Journal of Terramechanics, 44,

65–73.

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, 245–256.

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Figure 5: The maximum vertical (Z) acceleration in selected six points on cabin

floor in different conditions (a) cabin floor right side (b) cabin floor left side.

Figures 6 to 8 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 6(a) and 6(b) and Figures 7(a) and 7(b), it can

be seen that the existence 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 8(a) and 8(b)). Therefore, the anti-vibration material, as a

passive isolation system, protects the cabin floor against disturbing vibration at high

engine rpm.

Figure 4: The maximum acceleration values in different axles (X,Y,Z) in positions

(a) No 2 without anti-vibration material (cabin floor right side), (b) 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).

Figure 3: The maximum vertical (Z) acceleration in selected six points on cabin

floor (a) 800 rpm, (b) 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(a) 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 anti-vibration material) for 800, 1600 and 2200 rpm. In point No. 2 (Figure

4(a) 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(b)

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.

Figure 6: Cabin floor displacement in 800rpm (a) without anti-vibration material

and (b) with anti-vibration material on cabin floor.

Figure 7: Cabin floor displacement in 1400rpm (a) without anti-vibration material

and (b) with anti-vibration material on cabin floor.

Figure 8: Cabin floor displacement in 2000rpm (a) without anti-vibration material

and (b) with anti-vibration material on cabin floor.