Dynamic response of MRE under power tool excitation: Implications for hand-arm vibration reduction

Abstract

Prolonged exposure to power tools on construction sites can lead to Hand-Arm Vibration Syndrome (HAVS), a debilitating condition characterized by numbness, pain, and permanent damage to nerves, blood vessels, and muscles in the hands and arms. ISO 2631-1:1997 dictates that vibrations in the 0-80 Hz range, mainly those transmitted through the hand-arm system, exhibit long-term effects. While passive vibration isolation techniques are often limited by their application-specificity, active isolation techniques are limited to specific devices. This study introduces a semi-active vibration isolation system to mitigate vertical vibrations under varying drilling conditions and overcome these limitations. The focus is on the front/chuck region, where precise control is essential, and increased grip force can amplify vibration transmission. A Magnetorheological elastomer-based handle (MREH) is designed and attached to the hammer drill. An experimental setup is built where the modified drilling machine with the MRE handle is mounted on a sliding platform to accommodate bricks and concrete beam samples of varying hardness. The performance evaluation of the MREH is conducted using the natural frequency obtained from the Modal Testing method at different magnetic fields. Results indicate the field-dependent behaviour of the MREH on the isolation capabilities by reducing the amplitudes. The characteristic behaviour of MRE results in a maximum shift of 2 Hz and a corresponding 73.68% reduction in amplitude, increasing the drilling comfort by limiting the vibration transmission.