Assessment of ergonomically designed handle shapes for low-frequency vibration responses

Abstract

Hand-operated tool handles transmit a large magnitude of vibration to the hand-arm system during low-frequency operations. Therefore, the precise design of a hand tool is very important to overcome musculoskeletal disorders, hand-arm vibration, etc. This study was aimed at developing optimal tool handles with an increased contact area and to overcome the contact pressure, which causes discomfort and pain. Six different human hand-based optimal handles (handles B to G) and one optimal cylindrical handle (handle A) were designed and fabricated using 3D printing technology, in order to assess the effect of low-frequency vibrations. The effect of handle shapes was evaluated with objective and subjective measurements using 15 subjects. Objective measurements were performed to assess the vibration transmissibility by experimental study at the frequency range of 0–100 Hz, and subjective measurements were performed to rate the handles based on comfort descriptors and overall comfort of the handles. Root mean square vibration accelerations were recorded at the wrist, elbow, and shoulder of each subject and at the base of the handle fixture to evaluate the vibration transmissibility for each handle. The mean vibration transmissibility was found to be minimum for handle B and was rated to be more comfortable by the subjects. The results indicated that all the human hand-based handles transmit less vibration and were rated to be more comfortable than the optimal cylindrical handle.