A new methodology for measuring the vibration transmission from handle to finger whilst gripping

The transmission of vibration from hand-held tools via work gloves and into the operators' hands can be affected by several factors such as glove material properties, tool vibration conditions, grip force, and temperature. The primary aim of this study is to develop a new methodology to measure and evaluate vibration transmissibility for a human finger in contact with different materials, whilst measuring and controlling the grip force. The study presented here used a new bespoke lab-based apparatus for assessing vibration transmissibility that includes a generic handle instrumented for vibration and grip force measurements. The handle is freely suspended and can be excited at a range of real-world vibration conditions whilst being gripped by a human subject. The study conducted a frequency response function (FRF) of the handle using an instrumented hammer to ensure that the handle system was resonance free at the important frequency range for glove research, as outlined in ISO 10819: 1996: 2013, and also investigated how glove material properties and design affect the tool vibration transmission into the index finger (Almagirby et al. 2015). The FRF results obtained at each of six positions shows that the dynamic system of the handle has three resonance frequencies in the low frequency range (2, 11 and 17 Hz) and indicated that no resonances were displayed up to a frequency of about 550 Hz. No significant vibration attenuation was shown at frequencies lower than 150 Hz. The two materials cut from the gloves that were labelled as anti-vibration gloves (AV) indicated resonance at frequencies of 150 and 160 Hz. However, the non-glove material that did not meet the requirements for AV gloves showed resonance at 250 Hz. The attenuation for the three materials was found at frequencies of 315 Hz and 400 Hz. The level and position of the true resonance frequencies were found to vary between samples and individual subjects.