Human finger subjected to shock vibration loading

Typ
Examensarbete för masterexamen
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Publicerad
2022
Författare
Nilsson, Johan
Oljelund, David
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In Sweden it is estimated that around 330 000 workers use vibrating hand-held tools with an exposure of at least 2 hours per day. The damage of hand transmitted vibrations for hand-held tools within the frequency span 6.3 - 1250 Hz have been studied and are described by the international standard ISO 5349. The potential damage of exposure to higher frequencies is however not currently described by the standard and the human response of exposure is not known. Previous work has studied a 2D Finite Element model representing a human finger to investigate effects of shock waves, i.e. waves with high-frequency (above 1250 Hz) transients. However, those attempts were made without access to experimental data, and without clear distinction between the effects from geometry, material properties and FE-mesh. Therefore a 1D FE model of a finger was developed to study these effects on propagating waves. For comparison with experiment output, the 1D FE model was tested with a real input load. The experiments made on real fingers examined the effects from different fingers, loading magnitude, dates. In addition, acetone and electro-conductive gel was applied to the fingers to study the consistency of the finger response as well as the influence of fingerprints. Furthermore, two types of substitute fingers, ballistic gel and silicon, with different materials substituting bone were produced and tested to see if an increased consistency of the response could be achieved. This was concluded into recommendations for future implementations for the 2D FE model. It was concluded that the dynamic response and wave propagation velocity did not change significantly without the fingerprint. The substitute fingers tested did not behave more consistently than the real fingers. For the 1D FE model it was concluded that in order to capture the experimental output better it is needed to study the damping of the finger to better model the damping. Additionally, the bone in the finger significantly affect the reflection and transmission of the wave.
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Ämne/nyckelord
LS DYNA, experiment, vibration, human finger, ISO 5349, FE model
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