VIBRATION ISOLATORS FOR PORTABLE VIBRATING TOOLS

PART 5. VIBRATION FORCE MEASUREMENT FOR EVALUATION OF EFFECTIVENESS OF VIBRATION ISOLATORS

Abstract

A newly developed dynamic force pickup was applied to measurement of vibra-tion force, in which several experimental conditions were examined by laboratory tests using the vibration table for establishment of the method of force measure-ment. For real application, effectiveness of vibration isolation materials to portable vibrating tools was measured by the force pickup. As the field survey, the vibra-tion force level and the spectra were observed on a rivetting hammer.
It was concluded that the force pickup with the cross section of about 45 x 30 mm² was usable. The following conditions were suitable to get good reproducibility and linearity, namely, pressing force to the force pickup more than 3 kgf, angles of each joint of the hand-arm at 90°C and the near-wrist position on the palm touch-ing the force pickup.
The vibration force-frequency characteristics obtained under these conditions were confirmed by digital simulation using a mini-computer. It was realized that use of the force pickup to check the effectiveness of the vibration isolation materials like rubber foam was problematic, because of large dependence on the measuring conditions.
On the rivetting hammer, the vibration force spectra had the main components at 31.5 and 40 Hz, and its force level was about 150 dB±2 dB. The isolation material was not effective on the rivetting hammer, for the main frequency was very low.