Handle Vibration Research Articles

Effects of Short-Term Hand Tractor Operation on Upper Limb Responses of Users

ABSTRACT Objectives Continuous exposure to hand-arm vibration integrated with poor posture and forceful movements are known causes of musculoskeletal disorders (MSD). In most related studies, force and vibration levels in experimental research is controlled. This study aims to determine how actual hand tractor field operation can affect the upper limb of users. It intends to characterize upper limb muscle activation applied during actual hand tractor usage. Lastly, it determines the immediate impacts on hand strength and perceived upper limb discomfort after the operation. Methods We recruited 15 farm operators with a mean working experience of 20.1 ± 12.2 years. They were asked to operate a hand tractor on paddy fields for at most 8 minutes. Handle vibration was measured using a tri-axial accelerometer. The total unweighted vibration acceleration was computed and used to represent the handle vibration magnitude. Muscle activation was measured using surface electromyography (sEMG). Six sEMG sensors were attached to the dominant and non-dominant side of the extensor carpi radialis (ECR), bicep, and deltoid. Pre- and post-task hand strength and subjective discomfort rating were also taken. Results The total unweighted handle vibration acceleration is 17.45 ± 7.53 m/s2. This exceeds the allowable safe value. Meanwhile, the percentage of maximum voluntary contraction (% MVC) of the muscles ranged from 6% to 14% with the ECR having a significantly higher activation (p < .05) than the bicep and deltoid. The post-task grip strength of the dominant hand was lower than its pre-task value (p < .01) while that of the non-dominant side did not vary significantly. There is a modest trend of higher hand discomfort of the non-dominant side on post-task than pre-task rating (p < .10). Although, overall, the perceived discomfort ranged from none to mild discomfort. Conclusion In conclusion, the study showed an indication that the effects of vibration on humans are evident even at mild muscle exertion, with the exertion predominantly concentrated on the distal arm area clearly affecting grip strength and hand discomfort. In such cases, future recommendations can revolve around the improvement of the hand tractor handle grip to impose grip comfort and ease.

Investigation of Motorcycle Handle Vibration Attenuation using a Suspended Handlebar with Different Rubber Mount Characteristics

Motorcycle riders are exposed to prolonged hand-transmitted vibration that can lead to hand numbness and trembling and, in extreme cases, disorders such as the Hand-arm Vibration syndrome (HAVs). The vibration of a motorcycle handle is the result of two major excitation forces, namely the engine vibration and the road-tire vibration. Operating the engine throttle control requires the rider to grip and twist the throttle handle which in turn provides a good vibration transmission path from the handle to the hand. The on-road measurement of hand-arm vibration (HAV) in a rider of an underbone single-cylinder motorcycle show a relatively high value of HAV, with a_hv of 8.28m/s^2. One feasible solution is to attenuate the handlebar vibration transmissibility, by using rubber mounts to create a suspended handlebar. In this study, based on Experimental Modal Analysis (EMA), a hand gripped modal model of the handlebar is developed, and the evaluation is done on the frequency responses of different handlebar designs. The selection criterion is based on the frequency response function (FRF) synthesis index (area under curve) and in this work the area under FRF curve is taken for frequency range of 0 ? 200Hz based on the HAV system. Order analysis of the handle vibration showed higher acceleration level in the z-axis (vertical) compared to the y-axis (horizontal) and for the on-road testing produces, much higher vibration level is determined compared to engine-related vibration due to the tire-road interaction. The suspended handlebar with the best performance is selected for actual on-the-road test, and the result shows a lower a_hv value of 4.08m/s^2 (51% reduction), which significantly increases the vibration exposure limit value (EAV) time from 44 minutes to 3 hours.

Effects of various handle shapes and surface profiles on the hand-arm responses and comfort during short-term exposure to handle vibration

The magnitude of hand- (HTV) and wrist- (WTV) transmitted vibration can negatively impact upper limb responses even during short-term exposure. This study aimed to establish the effects of various handle-grip designs on the harmful impacts of vibration, sustained grip exertion, and unnatural posture. The primary focus was to investigate how using a handle grip and how three shapes with two surface profiles affect HTV, WTV, and forearm muscle activities during exposure. The secondary goal was to evaluate the immediate effects on fundamental hand functions, perceived discomfort/comfort, and perceived vibration level after exposure. The final objective was to assess which of the handle designs had the least harmful effects. Fourteen young male adults were recruited and asked to consistently grip a vibrating handle structure for 2 min while the primary parameters were recorded. Pre- and post-task measurements of secondary parameters were recorded on the six design conditions and one control condition (no handle grip). The study found that implementing a regular circular-smooth handle resulted in lower transmitted vibrations, leading to lower upper-limb discomfort, higher grip comfort, and lower perceived vibration. Additionally, shape significantly affected HTV, resulting in grip strength reduction, while surface profile did not influence transmitted vibrations but significantly impacted ring and small finger sensitivity, finger and hand discomfort, and grip comfort. Finally, forearm muscle activities were unaffected, and no significant interaction effects were observed. Circular handles also had the least negative impacts, and elliptic handles had the most negative impacts on the upper extremity because of the level of hand-handle contact stress and hand-grip effort. Meanwhile, the uneven distribution of vibration on the fingers and palm imposed by the rounded spikes on the patterned surface led to decreased finger sensitivity, higher discomfort, and lower grip comfort. Therefore, when machine operation involves moderate grip exertion, pronated forearm posture, and short-term handle vibration exposure, implementing a hard-solid handle with less hand-handle contact area, less grip effort, and even texture is recommended.

Determination of the dynamic performance of natural viscoelastic composites with different proportions of reinforcing fibers

Abstract Viscoelastic composites are strong and handle vibration damping quite well, which allows them to be used in a wide variety of applications. Thus, there is a need to determine the optimal amount of fiber to ensure high mechanical and dynamic performance with as little interference as possible. The purpose of this work is to find the most appropriate percentage of organic fiber – cellulose derived from corn stalks in a polylactic acid matrix, studying the changes in damping characteristics, tensile strength, bend-test. As parameters for comparison, the coefficient of bending and breaking strength, modules of accumulation and losses, factor C were chosen. It was found that strength indicators decrease with fiber fraction growth. While the damping factor at the glass transition temperature increases. In order to confirm the results obtained, the calculation of the C factor was used. The study investigates the damping factor’s dependence on the mechanical properties. It is shown that there is a correlation between moduli and bending strength with increasing fiber fraction. The scientific novelty of this work is the study of natural viscoelastic composites with different proportions of reinforcing fibers based on mechanical and dynamic characteristics in order to create and apply biodegradable viscoelastic composites in various fields.

Anti-Resonance Frequency Control by Span-Tuning Dynamic Vibration Absorber for Brush Cutter Vibration Reduction

Abstract Significant handle vibrations often occur during mowing operation even with anti-vibration type brush cutters. This is often caused by combined-bending natural mode of the main pipe and driveshaft which is mainly excited by cutting head rotational force. In this study, we focused on the placement span of the rubber bushings that support the driveshaft to suppress this kind of resonance. More specifically, we have designed a new component, called a span-tuning dynamic vibration absorber (ST-DVA), which utilizes the bending mode of the driveshaft that is determined by the placement span of rubber bushings. Analysis results of the finite element method (FEM) showed that the ST-DVA generated anti-resonance at a specific point on the main pipe under the first-order inertial force of the cutting head. We also succeeded in controlling anti-resonance frequency under the excitation. In actual measurements at the target frequency, handle vibration of the first-order component of the cutting head could be reduced by 51% and overall handle vibration could be reduced by 49% compared with those produced via equal-span rubber bushing placement. Hence, our study provides a design method that makes it possible to utilize the driveshaft, which a primary brush cutter component, as a dynamic vibration absorber by altering the placement span of the rubber bushings.

R2: Drilling into concrete: Effect of feed force on handle vibration and productivity

Approximately 1.6 million commercial construction workers in the US use rotary hammer drills for drilling into concrete to insert anchor bolts or rebar. The exposure to vibration may lead to hand-arm vibration syndrome and other musculoskeletal disorders depending on handle vibration acceleration level, hand grip force, and duration of exposure. There is little information on the relationship between feed force (FF), e.g., the push force applied by the worker, and handle vibration. A robotic test bench for rotary hammer drills was used to evaluate the effects of different FF on handle vibration and productivity (e.g., penetration rate and holes drilled). Increasing FF from 95 to 163 N was associated with an increase in total weighted handle vibration (ahv) of 7.2–8.5 m/s2 (slope, p < 0.001) but from 163 to 211 N there was no change in vibration level (slope, p = 0.17). Increasing FF from 95 to 185 N was associated with an increase in penetration rate of 7.2–8.5 m/s2 (slope, p < 0.001) but from 185 to 211 N there was no change in penetration rate (slope, p = 0.49). Based on the maximum allowable duration of exposure to hand vibration, specified by the ISO and ACGIH Action Limits, and the penetration rate, the drilling productivity, in m drilled per day, is greatest for the lowest FF tested. Contractors and construction workers should be informed that when drilling into concrete, the lowest exposure to harmful hand vibration and the best overall productivity occurs when the lowest operational FF is applied during hammer drilling.

Attenution of Motorcycle Handle Vibration using Suspended Handlebar

Motorcycle rider is exposed to the handle vibration. Extended exposure to high level of handle vibration can result is hand-arm vibration syndrome (HAVs). In South East Asia the majority of the motorcycle are powered by single cylinder small displacement (70 – 125 cc) engines. This paper describes the modal analysis of a small single cylinder underbone type motorcycle widely used in the rural and urban for commuting to workplace. A suspended handlebar is developed by mounting the handlebar on rubber mounts. Transmissibility measurement are carried out for static and on the road condition. There are conditions where transmissibility is above unity due to resonance for the existing handlebar and this condition is overcome by the suspended handlebar except at frequency of 25 Hand this was below the operating frequency range of the motorcycle engine of cruising speed (50 – 60 Hz). On the road tests show that the handlebar is effectively attenuate with the installation of the engine mounts. Maximum attenuation of 79 % is achieved at 3300 – 3400 rpm which give HAV of 3.41 ms −2.

Exploratory Study on the Impacts of Handle Vibration on the Hand and Forearm

Exploratory Study on the Impacts of Handle Vibration on the Hand and Forearm

Grass trimmer hand-arm vibration reduction using multi-axial vibration absorber

In this investigation, the novel multi-axial vibration absorber is proposed to reduce the handle vibration of petrol engine grass trimmer. The proposed vibration absorber is designed using Dunkerley’s equation and fabricated for testing. The experimental modal analysis of absorber is conducted to find resonance frequencies of the absorber and to validate the results obtained from equations. The experimental tests are carried on grass trimmer with absorber attached near handle location to find effectiveness of absorber in reducing hand-arm vibrations in the x, y and z directions. The result indicated that the total vibration value measured at the handle of grass trimmer is reduced by substantial level with the attachment of multi-axial vibration absorber.

Pneumatic rock drill vs. electric rotary hammer drill: Productivity, vibration, dust, and noise when drilling into concrete

ObjectivesBoth pneumatic rock drills and electric rotary hammer drills are used for drilling large holes (e.g., 10–20 mm diameter) into concrete for structural upgrades to buildings, highways, bridges, and airport tarmacs. However, little is known about the differences in productivity, and exposures to noise, handle vibration, and dust between the two types of drills. The aim of this study was to compare these outcomes with similar mass electric rotary and pneumatic rock drills drilling into concrete block on a test bench system. MethodThree experiments were conducted on a test bench system to compare an electric (8.3 kg) and pneumatic drill (8.6 kg) on (1) noise and handle vibration, (2) respirable silica dust, and (3) drilling productivity. The test bench system repeatedly drilled 19 mm diameter x 100 mm depth holes into cured concrete block while the respective exposure levels were measured following ISO standards. ResultsProductivity levels were similar between the electric and the pneumatic drill (9.09 mm/s vs. 8.69 mm/s ROP; p = 0.15). However, peak noise (LPeak: 117.7 vs. 139.4 dBC; p = 0.001), weighted total handle vibration (ahw: 7.15 vs. 39.14 m/s2; p = 0.002), and respirable silica dust levels (0.55 vs. 22.23 mg/m3; p = 0.003) were significantly lower for the electric than the pneumatic drill. DiscussionWhile there were no differences in drilling productivity between an electric and pneumatic drill of similar mass, there were substantial differences in exposure levels of noise, handle vibration, and respirable silica dust. Structural contractors should switch from pneumatic rock drills to electric rotary hammer drills for structural drilling into concrete in order to reduce worker exposures to the hazards of noise, hand vibration, and silica dust.

Grass trimmer handle vibration reduction by imposing node method using vibration absorber

The purpose of this investigation is to apply imposing node technique for vibration reduction of petrol engine grass trimmer handle using vibration absorber. The algorithm is devised to find the required resonance frequency of the absorber to impose node at desired location on beam. The numerical simulations are performed to find the usefulness of absorber for imposing nodes at the handle attachment location on timer pipe. The experimental test is conducted to validate the numerical results and to evaluate the vibration suppression during no cutting and cutting conditions. The vibration total value measured at handle of grass trimmer shows that absorber is useful in handle vibration reduction.

Attenuation of Motorcycle Handle Vibration Using Dynamic Vibration Absorber

Motorcycle riders are exposed to hand-transmitted vibration of the hand-arm system due to the vibration of the handle and extended exposure can result in numbness and trembling. One feasible solution to attenuate the handle vibration is by using a dynamic vibration absorber (DVA). In this work a DVA is designed and mounted on the motorcycle handle in order to reduce the vibration at the handle by transferring the vibration from the primary system handle to the secondary mass. Removal of elastomeric material at the DVA mounting locations, symmetry of secondary mass and the direction of DVA attachment influence the vibration absorption. A series of tests conducted show that the vibration on the handle is mainly induced by the engine and there is additional source of vibration from the road surface roughness. Installation of DVA at different locations on the handle resulted in various attenuation levels at different speed in the x and z directions. the attenuation level is between 59-68 % in the biodynamic x-directions for speed at 30-50kmh-1.

Construction Ergonomics: Concrete Bit Wear Increases Handle Vibration and Drilling Time

The use of large electric hammer and pneumatic drills exposes construction workers to high levels of hand vibration that may lead to hand arm vibration syndrome and other musculoskeletal disorders. This hammer drill test bench study demonstrated a small but significant increase in z-axis handle vibration (4.8 to 5.1 m/s2; ISO weighted) and drilling time per hole (7.8 to 12.3 s) with worn concrete bits when compared to a new bit. Drill bit manufactures may consider advising contractors that worn bits will increase the exposure of workers to hand vibration and will reduce worker productivity. Construction contractors should adopt a bit replacement program based on bit wear patterns in order to reduce exposure level and drilling time to hazardous hand vibration.

Fingers' vibration transmission and grip strength preservation performance of vibration reducing gloves

The vibration isolation performances of vibration reducing (VR) gloves are invariably assessed in terms of power tools' handle vibration transmission to the palm of the hand using the method described in ISO 10819 (2013), while the nature of vibration transmitted to the fingers is ignored. Moreover, the VR gloves with relatively low stiffness viscoelastic materials affect the grip strength in an adverse manner. This study is aimed at performance assessments of 12 different VR gloves on the basis of handle vibration transmission to the palm and the fingers of the gloved hand, together with reduction in the grip strength. The gloves included 3 different air bladder, 3 gel, 3 hybrid, and 2 gel-foam gloves in addition to a leather glove. Two Velcro finger adapters, each instrumented with a three-axis accelerometer, were used to measure vibration responses of the index and middle fingers near the mid-phalanges. Vibration transmitted to the palm was measured using the standardized palm adapter. The vibration transmissibility responses of the VR gloves were measured in the laboratory using the instrumented cylindrical handle, also described in the standard, mounted on a vibration exciter. A total of 12 healthy male subjects participated in the study. The instrumented handle was also used to measure grip strength of the subjects with and without the VR gloves. The results of the study showed that the VR gloves, with only a few exceptions, attenuate handle vibration transmitted to the fingers only in the 10–200 Hz and amplify middle finger vibration at frequencies exceeding 200 Hz. Many of the gloves, however, provided considerable reduction in vibration transmitted to the palm, especially at higher frequencies. These suggest that the characteristics of vibration transmitted to fingers differ considerably from those at the palm. Four of the test gloves satisfied the screening criteria of the ISO 10819 (2013) based on the palm vibration alone, even though these caused amplification of handle vibration at the fingers. The fingers' vibration transmission performance of gloves were further evaluated using a proposed finger frequency-weighting Wf apart from the standardized Wh-weighting. It is shown that the Wh weighting generally overestimates the VR glove effectiveness in limiting the fingers vibration in the high (H: 200–1250 Hz) frequency range. Both the weightings, however, revealed comparable performance of gloves in the mid (M: 25–200 Hz) frequency range. The VR gloves, with the exception of the leather glove, showed considerable reductions in the grip strength (27–41%), while the grip strength reduction was not correlated with the glove material thickness. It is suggested that effectiveness of VR gloves should be assessed considering the vibration transmission to both the palm and fingers of the hand together with the hand grip strength reduction.

Effect of bit wear on hammer drill handle vibration and productivity

ABSTRACTThe use of large electric hammer drills exposes construction workers to high levels of hand vibration that may lead to hand-arm vibration syndrome and other musculoskeletal disorders. The aim of this laboratory study was to investigate the effect of bit wear on drill handle vibration and drilling productivity (e.g., drilling time per hole).A laboratory test bench system was used with an 8.3 kg electric hammer drill and 1.9 cm concrete bit (a typical drill and bit used in commercial construction). The system automatically advanced the active drill into aged concrete block under feed force control to a depth of 7.6 cm while handle vibration was measured according to ISO standards (ISO 5349 and 28927). Bits were worn to 4 levels by consecutive hole drilling to 4 cumulative drilling depths: 0, 1,900, 5,700, and 7,600 cm.Z-axis handle vibration increased significantly (p<0.05) from 4.8 to 5.1 m/s2 (ISO weighted) and from 42.7–47.6 m/s2 (unweighted) when comparing a new bit to a bit worn to 1,900 cm of cumulative drilling depth. Handle vibration did not increase further with bits worn more than 1900 cm of cumulative drilling depth. Neither x- nor y-axis handle vibration was effected by bit wear. The time to drill a hole increased by 58% for the bit with 5,700 cm of cumulative drilling depth compared to a new bit.Bit wear led to a small but significant increase in both ISO weighted and unweighted z-axis handle vibration. Perhaps more important, bit wear had a large effect on productivity. The effect on productivity will influence a worker's allowable daily drilling time if exposure to drill handle vibration is near the ACGIH Threshold Limit Value.[1] Construction contractors should implement a bit replacement program based on these findings.

Carbide-tipped bit wear patterns and productivity with concrete drilling

Drilling into concrete with carbide-tipped bits using a hammer drill is a physically demanding task performed in commercial construction for setting anchors and rebar. Bit wear will not only decrease productivity (rate of penetration) but can also increase drill handle vibration, noise and dust exposure to workers. The purpose of this study was to evaluate the relationships between geometric patterns of bit wear and rate of penetration. Image analysis methods were used to quantify 13 geometric parameters of the carbide tip at various levels of wear, and the changes in the geometric parameters were then compared to changes in penetration rate. Two different bit designs were studied. New bits were worn by repeatedly drilling into aged concrete. Penetration rate was determined on a test bench system programmed to drill into aged concrete to a specific depth under force control while the time to complete the hole was measured. Increasing fluke slope, increasing shoulder rounding, and decreasing bit width were highly correlated to reduced productivity. The findings have practical value for contractors and bit manufacturers in providing a method to identify concrete bits that should be replaced due to reduced cutting ability.

A new test bench system for hammer drills: Validation for handle vibration

Workers' can be exposed to high levels of hand vibration when drilling into concrete or rock using hammer drills; exposures that can cause hand arm vibration syndrome. Exposure levels may be reduced by different drill and bit designs and drilling methods, but these interventions have not been systematically evaluated. The purpose of this project was to develop a robotic test bench system for measuring handle vibration on drills in order to compare differences in drill designs, power sources, bit designs and drilling methods. The test bench is a departure from the ISO method for measuring drill handle vibration (ISO 28927-10), which requires drilling by humans. The test bench system was designed to repeatedly drill into concrete blocks under force control while productivity and handle vibration were measured. Handle vibration levels with different drills and bit sizes were similar to those collected following ISO methods. A new robotic test bench system for measuring handle vibration is presented and validated against ISO methods and demonstrates dynamic properties similar to human drilling.

Vibration test and analysis of mini-tiller

Intense vibration happens at the handle of the mini-tillers that abundantly used in mountainous and hilly areas of southwest China. It is absolutely essential to probe into the vibration characteristics and factors why handle of the tiller vibrates violently. Therefore, the vibration acceleration signals of a mini-tiller’s handle and engine cover were tested under the following four conditions: the engine being idle, racing at medium and high speeds, and the tiller working in the field with high engine speed. The signals were processed by means of the time domain eigenvalue analysis and the frequency spectrum analysis. The results showed that when the tiller was under static condition, with increase of the engine speed, the handle vibration decreased in the vertical direction, increased in the fore-and-aft direction and had marginal changes in the left-to-right direction. When the tiller worked at high engine speed, the handle vibrated most violently in the fore-and-aft direction, while the vibrations at the engine cover and handle decreased substantially in each direction, compared with the static conditions. Rotary blades cutting soil increased the damping of the whole machine so as to reduce the vibration at the handle and the engine cover, but the handle vibration was still violent. When the tiller worked, that soil absorbing energies of some frequencies led to the first order unbalanced inertia force of the engine becoming the main reason why handle vibrated intensely. Keywords: mini-tiller, vibration test, time domain analysis, frequency domain analysis DOI: 10.3965/j.ijabe.20160903.1979 Citation: Li G, Chen J, Xie H J, Wang S M. Vibration test and analysis of mini-tiller. Int J Agric & Biol Eng, 2016; 9(3): 97－103.

Vibration Training for Upper Body

The aim of the present study was to evaluate the vibration transmission from a vibration platform through Vectran cables to the upper body and its relationship to induced muscular activation. Fifteen clinically healthy participants performed 3 different arm exercises-biceps curl, triceps curl, and lateral raise. Vibration transmission to the upper body was assessed over a wide range of accelerations (from 1.90 to 5.98 g) and frequencies (from 25 to 40 Hz). To assess the vibration transmission, 7 triaxial accelerometers were attached from the hand up to the head, and the root-mean-square of acceleration signal of each site-specific body point was calculated. Muscular activity of biceps brachii, triceps brachii, deltoid, and upper trapezius was recorded. The results showed a significant attenuation of the platform accelerations transmitted through the Vectran cables to the upper body. Handle vibration ranged between 27 and 44% of the acceleration delivered by the platform depending on platform vibration parameters (acceleration/frequency). Vibration increased the muscle activity of biceps brachii, triceps brachii, deltoid, and upper trapezius muscles significantly only during biceps curl exercises. No frequency or acceleration effect was found on the size of the muscle response. The results of the present study suggest that a cable-pulley resistance system on a vibration platform channels the vibration safely from the platform to the arms and induces additional muscle activation in some arm muscles when biceps curl exercises are performed.

A Study on Rotary Weeding Blade Installation Angle for Reduction of Hand Vibration in Working Type Cultivator

Purpose: Walking type cultivator used for weeding generated excessive handle vibration as well as bouncing motion depending on the weeding speed. This research was conducted to define a design factor of the rotary weeding blades for reducing soil reaction forces as well as hand vibration. Methods: The motion and forces acting on the rotary blades were reviewed to find out the most influencing parameter on hand vibration. The installation angle (IA) of the blade was selected and analyzed to determine the condition of no reaction force less. For removing the unnecessary upward soil reaction, the design factor theory of weeding blade was suggested based on geometrics and dynamics. For evaluation of design factor theory, the experiment in situ was performed base on ISO 5349:1. The vibration <TEX>$a_{hv}$</TEX> and theoretical value <TEX>$X_{MF}$</TEX> were compared with two groups that one was positive group (<TEX>$X_{MF}$</TEX> > 0) and the other was negative group (<TEX>$X_{MF}$</TEX> < 0). Results: <TEX>$X_{MF}$</TEX> was derived from rotational velocity, forward velocity, disk diameter, weeding depth, blade's width and IA of blade. Two groups had significant difference (p < 0.05). In aspect of the group mean total exposure duration, positive group was 17.53% bigger than negative group. When disk radius 100, 150 and 200 mm, minimum IAs were <TEX>$4{\sim}27^{\circ}$</TEX>, <TEX>$3{\sim}15^{\circ}$</TEX> and <TEX>$2{\sim}10^{\circ}$</TEX>, respectively. A spread sheet program which calculated XMF was developed by Excel 2013. Conclusions: According to this result, minimum IA of weeding blade for soil reaction reduction could be obtained. For reduction hand-arm vibration and power consumption, minimum IA is needed.