Vibration isolators for portable vibrating tools. Part 6. Problems concerning vibration force measurement.

Multi-point independent simultaneous force measurements were made to investigate the vibration force distribution on the palm and to determine one representative point on it for the purpose of field survey. The phase relationships between the force and the acceleration were also pursued. In connection with vibration force transmission, important effects such as vector, bypassing and mechanical impedance effects were studied with a model hand by using a vibration table. The real force transmission characteristics were examined with the human hand. A force measurement field survey was finally attempted on a grinder, an impact wrench and a riveter. The results observed on the model hand are in good agreement with those derived from the vibration theory for the vector and the bypassing effects. On the other hand, the results on the human hand are extremely complicated, owing to the contact conditions between the palm and the force pickups, and the results could not be fully interpreted. It can be concluded that the vibration force measured at the palm near the hand joint, where the force level usually shows the largest values, is representative. The vibration force on the palm does not represent proportionally the total force transmitted to the hand, but only reflects the characteristics of a visco-elastic material influenced by the vibration force.