Study of biomechanical response of human hand-arm to steering wheel vibrations

In this paper the finite element model of a human hand and arm (bone only model), comprising the hand, forearm and upper arm, has been analyzed to find its response to random vibrations transmitted from the steering wheel of a tractor. The purpose of this study is to determine the effect of sinusoidal and random excitations on the response of the hand-arm bones, from the point of view of understanding hand-arm vibration syndrome (HAVS). Biomechanical properties of the bone have been taken from literature. Modal analysis has been done to obtain the first few natural frequencies and mode shapes. Subsequently a 25 N force (nominal force from the steering wheel) has been imparted in the form of a stepped sine excitation from 0 to 200 Hz. This load has been applied as a distributed force perpendicular to the hand, with a part of scapula, the shoulder bone, constrained. The points of application of these loads were experimentally identified by observing the hand grip on the steering wheel. Finally random vibration analysis has been done by giving the acceleration spectra as input to the hand. These spectra were obtained by measuring accelerations along the three axes on the left and right hand sides of a steering wheel, at different engine speeds. The ISO 5349-1 frequency weighting curves have been used to weight the output acceleration PSD plots obtained to determine the total daily vibration exposure A(8).