Investigations on the description and definition of single shocks affecting the human hand-arm system during work as well as on possibilities for their assessment

Status:

completed 10/2015

Aims:

Single shocks are a special type of hand-arm vibration while working with mechanized (e.g. nailers, bolt guns) or non-mechanized (axes, hammers) tools. Until now there is no confirmed information about subjective and biological or health effects. There are a lot of different terms describing the kind of vibration under investigation (single shocks, repetitive shocks, impulse vibration) and one cannot always be sure, that different researchers mean the same thing when they use the same term.

Activities/Methods:

- investigations on the basics of measurements of the exposure conditions of single shocks - laboratory examinations of subjective distinction of single shocks, continuous shock sequences and other types of mechanical vibrationaffecting the human hand-arm system during work.

Results:

The results show, that with the state-of-the-art measurement technique several measurement parameters describing the shock exposure can be determined with the required accuracy. Many of these parameters are correlated to each other. The choice of one or more of these parameters for the judgment of the potential risk or the relevance to human health must be investigated in future studies in medical-biological cause-effect relationship. The results show furthermore three regions of subjective perception to distinguish regarding shock exposures: - Repeated single shocks - Continuous shock sequences - Stochastic vibrations Repeated shocks and continuous shock sequences are separated by Border A with about 15 Hertz, continuous shock sequences and stochastic vibration are separated by Border B with about 25 Hertz. Already relatively low magnitudes of acceleration cause a shock sensation. There is a significant interdependency of magnitude and pulse duration with a slope of 10 dB/decade in a double logarithmic scaling, and it seems to be in accordance with the principle of energy equivalence.

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