High-frequency shock-type vibration (HFV) with a frequency content mainly above 1250 Hz, e.g., from impact wrenches, is likely to cause a significant amount of vibration injuries and even hand-arm vibration syndrome. The objective of this study was to measure vibration up to 100 kHz with a Laser Doppler Vibrometer (LDV) and investigate the variation of vibration over the machine surface, the vibration propagation into finger tissue, and the vibration reduction on the finger tissue due to a foamed polymer layer. Our results showed that the vibration on the handle varies moderately and that the amplitudes are higher on the machine surface. A large proportion of the vibration is transferred into the finger tissue and thereby subjects the finger tissue to high-vibration amplitudes, but it is effectively reduced by a thin layer of foamed polymer.

Hand-arm vibration caused by isolated shocks is familiar from the occupational sphere, for example during work with stud guns and pneumatic nail drivers or forging hammers. Whether the existing methods for the measurement and assessment of continuous vibration in accordance with EN ISO 5349-1 [1] are also adequate for measuring and assessing isolated shock exposures is the subject of an ongoing research project. In order for confounding effects from the leisure sphere (e.g. tennis, golf) to be excluded, the effects of shocks were measured. With reference to the example of tennis as a leisure activity, the procedure is presented, including the preliminary studies required for isolated impact measurement, for determining the measurement points and coupling and for the elimination of artefacts. The field measurements were conducted on experienced players (test persons) in the scenarios of "serve", "return forehand" and "return backhand". The unweighted ah, the band-limited acceleration ahF and the additional frequency weighting awp were evaluated in accordance with ISO/TR 18570 in addition to the usual measurement variable of the frequency-weighted acceleration ahw. An indicative risk assessment was performed based on the existing assessment method. A health risk presented by exposure in the leisure sphere alone cannot be excluded by assessment of a typical exposure scenario. 

A project included redesign the tools to achieve low vibration, improved ergonomics, dust removal, and reduced noise while maintaining productivity, improving work environment. The first part of the project was a survey of vibration exposure to workers in the stone industry. The results from the survey showed that three work operations contributed to more than 90% of the vibration exposure. The second part of the project, the redesign of the tools was carried out using three approaches such as analytical calculation, multi-body simulation, and experimental study. Care has been taken to reduce friction in the system and the damping coefficient is estimated to be below 2 % of critical damping. Vibration isolation between the suspended mass and the housing is applied in the axial, radial and rotational directions in order to handle the vibrations that still remain after the tuned absorber.

By automatically balanced hand held grinders, vibrations are reduced to at least half and thereby reducing the estimated risk for vibration injuries by a factor of four. Simultaneously less grinding disc consumption and better grinding results are obtained. Vibration from grinders originates mainly from unbalance in the grinding wheel. Grinding wheels are low-price products, with uneven distribution of mass and coarse tolerances. This gives rise to out-of-balance, which changes as the wheel wears. By fitting an automatic balancer, that consists of steel balls contained in a cylindrical ball race on the shaft of the grinder, unbalances will be compensate for in the machine during grinding. The time it takes for an automatic balancer to stabilize is only a few tenths of a second. When grinding, the balancer is stable, even during substantial changes in speed. The technique is applicable to almost all grinding machines on the market and the first grinders using the technique have just been put on the market.

Workers in the rock face stabilisation sector are exposed to high levels of vibration from pneumatic rock drills, which can lead to vibration injuries. The work situation is also ergonomically challenging since the work often is performed on steep cliffs with heavy equipment and a substantial degree of dust exposure. To reduce exposure to vibrations, the equipment has been redesigned, including the machine’s handle, feeding hoist and the implementation of a reciprocating mass generating a counter force to reduce the vibrations. As a side project, a dust removal device was also developed. It was shown that vibration and dust exposure can be substantially reduced.

Long term vibration exposure may cause vibration white fingers (VWF) as well as neurophysiological disturbances such as dampness and tingling in fingers and hands, reduced grip strength and difficulties in handling small objects. In an assembly industry of heavy vehicles in Sweden a high prevalence of VWF has been reported in spite of low vibration when measuring the A(8) value according to ISO 5349. The operation that expose the workers for vibration is very similar in the production line and consists of tightening nuts and bolts with an impact wrench and an anvil in form of a wrench. Measuring vibration at frequencies up to 50 kHz shows high acceleration peaks especially in the anvil but also in the impact wrench. These high amplitude peaks are suspected to constitute a significant contribution to the high prevalence of VWF and are not taken into account in the current ISO 5349 standard which is also stated in the scope.

Vibration injury in the hand–arm system from hand-held machines is one of the most common occupational health injuries. Machines emitting high-frequency shock vibrations, e.g., impact wrenches have since long been identified as a special risk factor. In legislative and standard texts, the terms shock, impact, peak and transient vibration are frequently used to underline the special risks associated with these kinds of vibrations. Despite this fact, in the literature there is not a mathematically stringent definition of either shock vibration or how the amplitude of the shock is defined. In this study, we suggest algorithms for definition and quantification of these terms and apply them to machine vibrations of various kinds.

Since its initial publication in 1986, ISO 5439 has been unclear on the evaluation of isolated and repeated shock vibration. In 2015, an expert’s workshop was held in conjunction with the 13th International Conference that identified features of a vibration signal that may be important for predicting health outcomes, including high-frequency vibration and shock. Since then, ISO standards have been drafted on the measurement of shock and measurement of high-frequency vibrations, and in the European Union, a proposed revision of machinery supply legislation will require manufacturers to provide information on the average peak amplitude of acceleration. The Nancy Workshop introduced the issue of hand-transmitted (mechanical) shock (HTS) and work currently active within International Standards groups, and discussed options for defining HTS measurement. The workshop concluded that HTS is likely to present different risks to those of continuous hand–arm vibration, and that, therefore, there is a need for different metrics, and that high-frequency vibration is an important component of many HTS sources, e.g., impact wrenches, nail guns, riveting hammers, etc.; therefore, HTS evaluation should include higher frequencies of vibration, possibly up to 10 kHz.

High-frequency shock-type vibrations (HFVs) from, e.g., impact wrenches with a frequency content mainly above 1250 Hz have long been suspected to cause a significant number of vibration injuries, HAVS. These vibrations are unregulated in the current standard for risk estimation, ISO 5349-1; thereby, the risk of injury is suspected to be underestimated. The objective of this study was to investigate the effects on finger tissue subjected to HFVs similar to those from impact wrenches by using a 2D finite element model of a fingertip. The model was validated through experiments. Using the input acceleration from the experiments, the model predicted high pressure variation and particular negative pressures at levels close to 0.1 MPa (1 Bar) or more, which are levels where cavitation in liquid can occur, with a detrimental effect on biological systems.

Vibration injuries cause significant costs for society, great personal suffering, and often the relocation of personnel within a company. The project “Zero Vibration Injuries” is a Swedish initiative with the objective of taking a holistic approach to the problem, involving all stakeholders. The project’s vision is “Zero Vibration Injuries”. This is achieved by addressing the source of the problem by reducing the vibration levels in hand-held machines and applying the solutions in industry to the benefit of the users.

Objectives. Exposure to hand-transmitted shocks is a widespread phenomenon in the workplace. Separate risk assessments for shocks do not exist in current international hand–arm vibration regulations, leading to potential underestimation of associated health risks. Methods. In a pilot study approach, eight healthy males were exposed to sets of 3 × 5 min of repetitive shocks and 1 × 5 min of random vibration, controlled at a weighted vibration total value of 10 m/s2. Baseline and post-exposure measurements of vibration perception thresholds, finger skin temperature, maximal grip/pinch force and the Purdue pegboard test were conducted. Muscle activity was monitored continuously by surface electromyography. Results. Shock exposures evoked a temporary increase of vibration perception thresholds with high examination frequencies. A decrease of skin temperature was hinted for shocks of 1 and 20 s–1. Electromyographical findings indicated an additional load on two forearm muscles during shock transmission. Maximum grip force and manual dexterity were not affected, and pinch force only partially reduced after the exposures. Conclusion. Physiological effects from shock exposure conform to those described for hand–arm vibration exposure in principle, although some divergence can be hypothesized. Randomized designs are required to conclusively assess the need of occupational health concepts specifically for hand-transmitted shocks.

Background and Aims Hand-arm vibration syndrome (HAVS) is an irreversible neurodegenerative, vasospastic and musculoskeletal occupational disease of workers using powered hand tools. The etiology is poorly understood. Neurological symptoms include numbness, tingling and pain. This study examines impact hammer vibration-induced injury and recoverability of hair mechanosensory innervation. Methods Rat tails were vibrated 12?min/d for 5 wk followed by 5 wk recovery with synchronous non-vibrated controls. Nerve fibers were PGP9.5 immunostained. Lanceolate complex innervation was compared quantitatively in vibrated vs sham. Vibration peak acceleration magnitudes were characterized by frequency power spectral analysis. Results Average magnitude (2515?m/s2, rms) in kHz frequencies was 109 times that (23?m/s2) in low Hz. Percentage of hairs innervated by lanceolate complexes was 69.1% in 5wk sham and 53.4% in 5wk vib generating a denervation difference of 15.7% higher in vibration. Hair innervation was 76.9% in 5wk recovery sham and 62.0% in 5wk recovery vibration producing a denervation difference 14.9% higher in recovery vibration. Lanceolate number per complex (18.4?±?0.2) after vibration remained near sham (19.3?±?0.3), but 44.9% of lanceolate complexes were abnormal in 5 wk vibrated compared to 18.8% in sham. Interpretation The largest vibration energies are peak kHz accelerations (~?100?000?m/s2) from shock waves. The existing ISO 5349-1 standard excludes kHz vibrations, seriously underestimating vibration injury risk. The present study validates the rat-tail, impact hammer vibration as a model for investigating irreversible nerve damage. Persistence of higher denervation difference after 5-week recovery suggests repeated vibration injury destroys the capability of lanceolate nerve endings to regenerate.