HAND-ARM VIBRATION ANALYSIS: THE FINITE ELEMENT APPROACH

Abstract

The study of the vibration influence on the hand-arm system leads to the conclusion that many factors may cause occupational diseases in this field of activity: starting from workers using hand tools, continuing with professional drivers affected by the speed change gear vibrations, several occupational categories are affected. This fact requires enhanced attention from manufacturers’ point of view, in the sense of developing different systems for protection against vibrations. For achieving this, the dynamic behaviour investigation of the hand-arm system is of utmost importance. From the vibration linear theory point of view, the first step of the analysis is to identify the system natural frequencies and natural mode shapes. Although several experimental research have been carried on, theoretical studies are rare and limited to lumped-parameter studies in which distributed masses are reduced to concentrated mass connected to each others via springs and dampers in series or parallel consisting a multiple-degree-of-freedom vibratory system. The reason is maybe linked to the fact that the modeling of human body or part of it is not straightforward, maybe complexities are associated with this type of analysis: it is not possible to consider a single element of body and deal with as if it was isolated; nearly all human body elements have extremely difficult geometries not easily described in terms of simple geometrical shapes; biomaterials do exhibit complicated non-linear viscoelastic behaviour and linear vibration theory fails to succeed in description of such a complex behaviour. The research work presented in this paper aims to develop a model for the hand-arm system. The system consists of arm, forearm and hand, assembled together and linked by different types of joints. The model is obtained with CAD tools and analyzed using the finite elements method. Conclusions are drawn for further improvements.