Evaluation Of Whole-body Vibration Research Articles

Measurement Time in the Evaluation of Whole-Body Vibration: The Case of Mechanized Wood Extraction with Grapple Skidder

The grapple skidder is a self-propelled forestry machine that is used for the extraction of trees in wood harvesting—commonly used in full tree systems. Moving this machine can expose operators to occupational hazards of physical origin, among which whole body vibration stands out. However, the measurement of this risk agent does not have a standard measurement time, being performed for periods of approximately 30 min—disregarding the time of the daily workday. In view of this, it was analyzed whether occupational exposure to whole body vibration transmitted to grapple skidder operators using different measurement times complies with the guidelines for preventative purposes. Thus, measurements of whole-body vibration were carried out along three orthogonal axes over a period of one hour and over a daily workday of eight hours—by which were measured the daily (8 h) vibration exposure for the l-axis and the vibration value. The acceleration values in the three evaluated axes were higher for the daily working day, denoting the influence of the measurement time. In addition, the vibration dose value resulted in values above the action limit for both evaluations; however, the daily workload was highlighted—indicating the presence of higher vibration peaks over a longer measurement time. Thus, the assertiveness and influence of measurement times over the daily working day for whole-body vibration transmitted to grapple skidder operators is evidenced.

Evaluation of Whole Body Vibration (WBV) of Dumper Operators Based on Job Cycle

Dumper operators are frequently exposed to whole body vibration (WBV) in surface mines. Surface mining activities involve the amalgamation of comparatively high intensity of vibration and extended exposure durations. Efficient risk reduction mandates knowing of important phases of a task that poses a threat to health of dumper operators. So far in India very limited studies have been reported on WBV exposure with regard to surface mines. This paper evaluates WBV of dumper operators based on ISO 2631-1:1997 Standards and European Union (EU) Directive 2002 for different phases of job cycle. Six dumpers were considered for this study and the vibration measurements were made for all the four phases of the job cycle by placing the triaxial accelerometer on the operator’s seat-surface and at the seat-back, independently. The findings of the study revealed that the haulage task (loaded travel and empty travel) remains the chief contributor to vibration exposure according to seat-surface and seat-back measurements. Maximum frequency weighted root mean square (RMS) of 1.12 m/s2 and 1.09 m/s2 were reported for empty travel task for seat-surface and seat-back measurements, respectively. For seat-surface measurements based on RMS, Z axis remains as the dominant axis of vibration for all the dumpers during haulage task, whereas for seat-back measurements, the dominant axis varies between X and Y. Exposure action value (EAV) based on RMS has exceeded the threshold value of 0.5 m/s2 for all the dumpers during loaded travel and empty travel for seat-surface as well as for seat-back measurements.

Experimental attenuation and evaluation of whole body vibration for an off-road vehicle with magnetorheological dampers

The paper presents an analysis of vehicle vibration, ride comfort and handling which have a decisive influence on health and safety of a driver. Experiments were carried out for a commercially available experimental all-terrain vehicle in the field in hard conditions with retaining the sufficient repeatability. The vehicle is equipped with a complex vibration control system, taking advantage of four automotive magnetorheological dampers. Numerous sensors, which measure acceleration in four points of the vehicle body, near the driver’s seat, feet and hands, body orientation in space and speed of vehicle wheels, are available in the vehicle. They were used for evaluation of magnetorheological dampers’ control signals and analysis of vibration affecting the driver. Constant values of magnetorheological damper control current were used for emulation of different settings of passive suspension. The analysis performed in frequency domain showed how vibration propagates in a medium-sized all-terrain vehicle and indicated that driver’s hands are mostly affected by the road-induced vibration. It was also confirmed that the greatest improvement of ride comfort can be obtained for the soft suspension, i.e. uncontrolled magnetorheological dampers. Furthermore, the Skyhook algorithm was implemented, including the proportional control of the magnetorheological damper force and the inverse Tanh model of the magnetorheological damper. It was validated for the wideband road-induced excitation contrary to the experiments commonly presented in the literature, which are performed only for harmonic excitation. It was shown that the properly tuned Skyhook algorithm enables improving vehicle handling compared to the passive suspension and simultaneously it can maintain the similar or even better results of ride comfort.

Three-axial evaluation of whole-body vibration in agricultural telehandlers: The effects of an active cab-suspension system

ABSTRACTAgricultural and earth-moving machinery operators are particularly exposed to whole-body vibration (WBV), which has severe effects on health and affects comfort and performance. Few studies have investigated vibrational safety and comfort issues in telescopic handlers. These vehicles are widespread in many off-road applications—such as construction, agriculture, and mining—used to handle loads and to lift persons and equipment. This study investigated the effects of an active hydro-pneumatic cab-suspension system fitted to a telehandler on a driver's vibration exposure along the x-, y-, and z-axes, through both objective and subjective assessments. Sixteen healthy professional telehandler drivers took part in the study. Objective measurements were acquired at the operator's seat, and subjective ratings were taken while participants drove the telehandler with either a deactivated or activated suspension system at 12 kph on an ISO 5008 smooth track. The results showed that the activation of the cab-suspension system reduced the root-mean-square acceleration along the x- and z-axes (p =.038 and p =.000, respectively). Moreover, the frequency analysis showed a reduction in the acceleration along the z-axis in the range of 2–25 Hz (p <.05 for all comparisons); in particular, the acceleration was reduced by 50% in the higher frequency range (4–20 Hz). A reduction in the vibration intensity was perceived by the participants along the y- and z-axes (p =.009 and p =.003, respectively). Implications for the future development of suspension systems are discussed.

Measurement and evaluation of whole body vibration of agricultural tractor operator

Exposure of whole body vibration (WBV) influences performance, comfort, and long term health risks of tractor operator. Therefore, measurement and evaluation of WBV parameters should be carried out to find probable effects on the health of tractor operators. In this study, a system was designed to measure the WBV of agricultural tractor operators and evaluated the hazard risks on operator’s body according to the ISO standards, and implementation of the WBV test in the official testing station was also suggested. A tri-axial accelerometer was employed to measure vibrations transmitted to the seated operator body as a whole through the supporting surface of the buttock on four typical farm roads under different speeds. The vector sum A(8) exposures on the rough tracks (earthen and grassland roads) exceeded the action limits of 0.5 m/s2 at a 10.9 km/h forward speed and reached to the action limit value at a 16.0 km/h forward speed on the concrete road. The vector sum of VDV(8) exposures did not exceed the action limits of 9.1 m/s1.75 and was greater on the grassland road. The vector sum Sed(8) exposures values exceeded the moderate probability of an adverse health limit of 0.5 MPa on all farm roads at high forward speeds and exceeded the high probability of an adverse health limit of 0.8 MPa on asphalt, concrete, and grassland roads which should be lower than the exposure limit values as suggested by the ISO and EC standards. The WBV evaluation procedure should be considered for implementation at the official tractor test station, which would response to domestic and international tractor test regulations and improve the market competitiveness. Keywords: agricultural tractor, whole body vibration, tractor operator, driving safety, ride comfort, test standard, health risk DOI: 10.3965/j.ijabe.20171001.2113 Citation: Kabir Md S N, Chung S-O, Kim Y-J, Sung N-S, Hong S-J. Measurement and evaluation of whole body vibration of agricultural tractor operator. Int J Agric & Biol Eng, 2017; 10(1): 248–255.

Investigation and validation of consumer device accelerometers for the assessment of whole-body vibration

AbstractThere exist a discrepancy between the usage of the expensive standard accelerometer and the cheap and accessible consumer device accelerometer for the measurement of whole-body vibration (WBV). This study investigated the validity of accelerations (g-forces) obtained from a consumer device accelerometer by simultaneously using the consumer device accelerometer with a standard accelerometer during evaluation of WBV experienced by earthmoving equipment operators. The consumer device accelerometer is a software (WBV) compatible with iOS devices from operating system 5 and above (LIS331DLH, 3-axis, ±2 g acceleration range, MEMS type) while the standard accelerometer used during this study is a GCDC tri-axial accelerometer (GCDC X16-4 3-Axis, G-Force Data logger, ±18 g acceleration range, MEMS type). The two accelerometers were mounted following the basicentric axes of the seated operators and put on before earthmoving operation. Data from both the accelerometers were analysed using MATLAB. Results got...

Evaluation of Whole Body Vibration and Back Pain Problem among Light Rapid Transit (LRT) Drivers

A cross sectional study was conducted to evaluate whole body vibration (WBV) and back pain problem among light rail transit (LRT) driver. This study was carried out to determine exposure level of whole body vibration and identify back pain problem due to whole body vibration exposure among LRT driver. Standardized Nordic questionnaire was used for the analysis of musculoskeletal symptoms, to identify the prevalence of back pain, information about health history, working time duration, and working experiences was obtained from 52 drivers of light rail transit (LRT) train. HVM 100 Larson Davis was used to measure whole body vibration measurement of eight LRTs with different vehicle number. The measurement of whole body vibration was done during operation working time. The data collected from HVM 100 were transferred to the Blaze software for getting the vibration magnitude of the experiment while data collected from survey were analyzed by using Statistical Package for the Social Sciences (SPSS) for statistical analysis. The analysis of graph patterns and the differentiation of magnitude value from each LRT were studied to determine the exposure level of vibration. A high prevalence of back pain (82.7%) among LRT drivers was found and high daily exposure level was obtained. The finding showed that, there are relations between back pain and daily vibration exposure which resulted in a correlation coefficient of 0.709, with significant at α = 0.05. In conclusion, it was expected that the individuals subjected to the high vibration levels would tend to report back pain.

Ride Quality Investigation of Passenger Cars on Different Road Conditions

Objective: The ride qualities of the six passenger cars were evaluated in 4 subjects on the highway and uneven road. The relation between vibration with driving velocity and driving posture were also investigated separately. Background: Ride comfort plays an important role in the vehicle design. Vibration is the one of the principal components associated with ride comfort. Method: The acceleration of the foot, hip and back were measured using B&K accelerometers in this study. The velocity of the passenger cars was maintained at a constant speed of 80km/h on the highway and 40km/h on the uneven road. For evaluating the effects of driving velocity and driving posture on vehicle"s vibration level, separate experiments were performed on the highway with 5 different vehicle speeds and 5 different backrest angles, respectively. Results: The overall ride value of the luxury car showed the best result while the smaller car showed the worst value on the highway. On the uneven road the overall ride value level was increased 75~98%. All the vehicles had the SEAT value less than 1. Faster the velocity lowers the SEAT value. The ride quality in terms of vibration gets worst when the backrest angle increased. Conclusion: The smaller car had a first mode at the higher frequency and showed higher vibration level. SEAT value was mostly affected by the seat property not by vehicle. We ranked the luxury car seat had a best vibration reduction quality than others based on SEAT values. When the driving velocity increased, the overall ride values were increased proportionally and the SEAT values were somewhat decreased. Application: Evaluation of whole-body vibration in the passenger car.

Evaluating Methods of Vibration Exposure and Ride Comfort in Car

Objective: This paper studies the method of measuring whole-body vibration in the car and terms associated. Background: Human exposure to vibration can be broadly classified as localized and whole-body vibration. The whole-body vibration affects the entire body of the exposed person. It is mainly transmitted through the seat surfaces, backrests, and through the floor to an individual sitting in the vehicle. It can affect the comfort, performance, and health of individuals. Method: Human responses to whole-body vibration can be evaluated by two main standards such as ISO 2631 and BS 6841. The vibration is measured at 8 axes - three translations at feet, 3 translations of hip and two translations of back proposed by Griffin. B&K"s sensors used in this study are the 3-axes translational acceleration sensor to measure the translational accelerations at the hip, back and foot. Results: The parameters associated with the whole-body vibration in the car are frequency weightings, frequency weighted root-mean-square, vibration dose values, maximum transient vibration value, seat effective amplitude transmissibility, ride values and ride comfort. Conclusion: Studied the evaluating methods of vibration exposure and ride comfort. Application: Evaluation of whole-body vibration in the car.

Evaluation of Whole-body Vibration in Building

Evaluation of Whole-body Vibration in Building

The Evaluation of Whole-Body Vibration Level in Hand-Held Pneumatic Tools (Rock Drill) by “Pneurop Cagi Test Code” Method

The evaluation of whole-body vibration in hand - held pneumatic tools (Rock drills) used in the Lashotor stone mines in Isfahan by the method PNEUROP CAGI (compressed air and gas institute) TEST CODE. This shows the methods for the use of construction equipment in stone mines under work circumstances. This method is designed to evaluate noise and vibration propagated by the hand – held pneumatic tools. Rock Drills are categorized as the major sources of noise and vibration by the Federal noise control Act of 1972. The paper demonstrates vibration values in three directions X, Y, Z and the three vital indices for workers while working with equipment, compared to standard graphs, produced by “Rock Drill” used in the above specified test method. This paper focuses on measurement and prediction of whole -body vibration indices in a rock drill used in stone mines using a B &amp; K vibration meter type 2512. In order to evaluate them we had to record the whole-body acceleration on the ground where the operator was standing and processing his work. The indices include reduced comfort (RC), fatigue decreased proficiency (FDP), and exposure level (EL) for a frequency response of 1–80 Hz shown Table I. As can be seen in table I, there are high values of rms acceleration in the Z and XY axes for exposure level and fatigue decreased proficiency, respectively. All values are based in a 5-hour exposure time. Although we found high levels of vibration in different axes, the most important index in comparison with its recommended limits can be exposure level, because it is a better index weighted for human vibration in workplaces. The reduced comfort index is not recommended for occupational and industrial use.

Evaluation of Whole-Body Vibration by the Category Judgment Method

The purpose of this research is to establish a scale for comfort with regard to whole-body vibration by the category judgment method. Experiments were conducted with random signals as stimuli. These stimuli consisted of three types of signal, namely stimulus F, with flat PSD (Power Spectrum Density) ranging from 1 to 100 Hz, stimulus H with PSD, which became 20 dB higher at 100 Hz than at 1 Hz, and stimulus L that had a PSD 20 dB lower at 100 Hz. These signals were modified by Wk frequency weighting in accordance with ISO 2631-1, and the R.M.S. values were adjusted to be equal. In addition, the signal levels were varied over a range of five steps to create 15 kinds of individual stimuli. The subjects sat on a flat, horizontal metal plate mounted directly on the vibrator and were exposed to vertical vibrations before being asked to choose a numerical category to best indicate their perceived level of comfort (or otherwise) during each stimulus. The creation of this assessment scale, including the aforementioned categories, enabled not only clarification of the relationship between the vibration stimuli and the degree of comfort but also discovery of the connection between the frequency-weighted R.M.S. acceleration and the corresponding categories representing each degree of comfort without overlap. Moreover, it became clear that the subjects' assessment of the degree of comfort perceived differed with differences in the vibration spectrum.

709 労働現場におけるISO2631に基づいた全身振動の測定と評価(生体の振動と反応,ヒューマン・ダイナミクス(1))

709 労働現場におけるISO2631に基づいた全身振動の測定と評価(生体の振動と反応,ヒューマン・ダイナミクス(1))

Whole-body vibration and health effects in the agricultural machinery drivers.

Recently farm mechanization has been widespread and developing rapidly, in particular riding farm machines are increasingly used in paddy fields in Japan. We have no information available on the actual situation regarding whole-body vibration on the seats of these farm machines from the standpoint of labour protection. Measurement and evaluation of whole-body vibration was performed on the seats of popular riding agricultural machineries. Whole-body vibration on the seats of combine harvesters and wheel tractors exceeded exposure limits and the fatigue-decreased proficiency boundary limit of 8 hr and also shortened the reduced comfort boundary limits of ISO 2631 (1985). Some combines, tractors and carieers had only less than one hour exposure duration as compared with the ISO 2631-1 standard (1997). On the other hand a questionnaire was also performed on the subject of agricultural machine operators. Any specific injury or other effects, i.e. low back injuries were not found among the group of operators as compared with those in non-operator farmers. It seems to be difficult to find out the health effects of whole-body vibration itself, because there may be a lot of causes, i.e. working posture, operating heavy materials, in farm working conditions.

Implementation of double-pulsed holography in evaluation of whole-body vibration

This study used a unique holographic technique to evaluate the effects of vibration on soft tissues and bones. It was possible to record forced whole-body vibration in humans by holograph interferometry using a double-pulsed ruby laser. The study investigated the manner in which the muscles of the back and vertebral column are affected by vibrations applied to the human buttocks in the sitting position. The subject was exposed to vibration at two frequencies: 40 and 60 Hz (vertical Z axis). Transmission of the vibrations along the subject's back was recorded by means of double-pulsed holography and electromyography. Evaluation of the vibration pattern showed that the vibrations are transmitted along the back all the way up to the neck and head. The pattern of vibration in the muscles of the back and vertebral column showed that the greatest effect was exerted on the lumbar region of the back and the area of transition between the thoracic and cervical regions.

Measurement and evaluation of whole-body vibration at work

The vibration to which the human body can be exposed while at work is complex. It may be composed of various frequencies, occur in several directions and contact the body at more than one point. The vibration will often vary from moment to moment and may contain shocks. The useful evaluation of vibration with respect to human response requires that the manner in which the responses depend on the frequency, direction duration of the vibration and the occurrence of shocks is adequately taken into account. This paper describes current methods of measuring and evaluating human exposures to whole-body vibration and shock.

A Methodology for the Test Design and Evaluation of Human Whole-Body Vibration in Ground Vehicle Systems

To date, testing and evaluation of whole-body vibration in ground vehicle systems have not always fully utilized appropriate experimental design methodology, applicable statistical tests, or relevant criteria. A test design and evaluation methodology was developed to eliminate these oversights. This methodology uses inferential statistics, questionnaires, and a comparison of vibration data with representative mission scenarios. The methodology was employed in the evaluation of two alternative tracked ground vehicle designs. The independent variables were track type, terrain, vehicle speed, and crew position. The dependent variables were International Standards Organization (ISO) 2631 whole-body vibration exposure limit times at the lateral, transverse, and vertical axes. Two different multivariate analyses of variance (MANOVAs) performed on the exposure limit data indicated that all main effects, as well as several interactions, were significant (p &lt; .01). A comparison of exposure limits to a representative mission scenario indicated that both track types would exceed ISO 2631 exposure, comfort, and fatigue limits during expected travel over cross-country terrain. Crew questionnaires also indicated crew discomfort when exposed to this type of terrain. The experiment demonstrated that the procedure was useful in helping to determine the extent that vehicle vibration permits the performance of the vehicle mission, within limits dictated by safety, efficiency, and comfort.

Subjective reactions to whole-body vibration of short duration

An important problem in the evaluation of whole-body vibration is how shocks are to be included in a comprehensive measure of the vibration load on man. This calls for knowledge of how the effect of the vibration changes as a function of its duration. This was the purpose of three experiments in which subjects were exposed to vertical sinusoidal vibration of varying duration. The vibrations were each presented together with a vibration of the same frequency but with a constant duration. The subjects task was to adjust one of the vibrations until both gave rise to the same discomfort towards the end of the vibration. Experiment I dealt with durations between 0·1 and 4 seconds of a 31·5 Hz vibration with intensities of either 1·1 or 2·3 m/s 2. In Experiment II the same vibrations were used but the investigated interval was 1–128 seconds. These two experiments showed that the subjective effects, expressed as log m/s 2, increases linearly with log exposure duration up to 3–4 seconds. After this “critical time” the effect continues to increase, but at a much slower rate. In Experiment III the 31·5 Hz vibration was compared to one of 6·3 Hz with respect to the increase of the effect between 0·2 and 117 seconds. The 31·5 Hz vibration yielded the same growth function as in Experiment II, whereas the effect of the 6·3 Hz vibration increased linearly during the whole interval and thus showed no indication of a “critical time”. Furthermore, this low frequency vibration showed a slower growth rate. The results are compared to those of two earlier studies in which partly different conclusions were drawn.