[An experimental study on transmission of hand-arm vibration on the body of users]

Vibration forced into the hand-arm system was observed on the body surface during work with chain saw and under loading experiments by electrodynamic shaker in the laboratory, and factors related to transmission over joints were investigated using pig elbow joints constructed with ulna, radius and humerus. Vibration was measured according to IS 5349 and JIS C1511 between 8 and 1,000 Hz in vibration frequency. Vibration on the bone of pig foreleg conducted without attenuating its amplitude from the peripheral side to the central side between 8 and 1,000 Hz. On the other hand, vibration transmitted over joints damped its amplitude in higher frequency components rather than in lower frequency between 8 and 1,000 Hz. The decreasing ratio of transmitted vibration over joint was changed by the resonance of the soft tissues between the bones constructing the joint. The attenuation changed with the elastic modulus of the soft tissues. The peak frequency was considered to be the resonance because of the physical mass and elasticity. The harder the joint was tied, the stronger became the transmission, because the resonance moved to higher frequencies with increase in elastic modulus. In the loading test from the electrodynamic shaker to the hand-arm system of man, vibration on the soft tissues was transmitted on its surface as wave motion, when the vibration was observed over the skin on the soft tissues. Vibration reduced its amplitude at every joints especially above 100 Hz. The shape of the vibration attenuation curves varied according to the frequency and components of the chain saws.(ABSTRACT TRUNCATED AT 250 WORDS)