Key Features:

Number of Pages: 9
Images
Labelled Diagrams

Buy Now

Abstract:

Prolonged, intensive exposure to hand-transmitted vibration could cause a series of disorders in the sensorineural, vascular, and muscular systems of the fingers, which are the major components of hand-arm vibration syndrome. The hand-arm responses to vibration have been mostly investigated in terms of biodynamic responses, which are believed to serve as the essential foundation for understanding the mechanisms associated with vibration-induced disorders and for developing better risk assessment methods. Moreover, thorough characterizations of the biodynamic responses are considered vital for the design and assessment of vibration attenuation devices, and for developing hand-arm vibration simulators for the assessment of power tools.

The vibration power absorption density (VPAD) is a good measure for the vibration exposure intensity of the soft tissues of the fingers. In order to calculate the VPAD at a fingertip, we proposed a hybrid modeling approach, which combines a 2D finite element (FE) model with a lumped parameter model. Whereas the lumped components are used to represent the global biodynamic characteristics of the hand-arm system, the FE component is used to predict the detailed stresses, strains, and VPAD in the fingertip The transmission of handle vibration to the wrist, elbow, and shoulder of the human hand and arm are characterized in the laboratory for the bent-arm and extended arm postures. Anti-vibration (AV) gloves have been increasingly used to help reduce vibration exposure.

However, the exact mechanisms of the AV gloves have not been seriously analyzed and sufficiently understood. How to appropriately assess the effectiveness of AV gloves for protecting the hand remains an issue for further studies. Therefore, the vibration transmissibility of the glove, the ratio of the vibration at the glove-hand interface to the handle vibration, is typically used as a measure of the glove effectiveness. The proposed model is applied to predict the effectiveness of the glove in terms of vibration transmitted to the fingers-glove and palm-glove interfaces, the finger bones, and the wrist.

Table of Content:

- EXPERIMENTAL SET-UP
- MODELING OF FINGERTIP
- MODELING OF HAND-ARM SYSTEM

Introduction:

Vibration is the study of motions that repeat themselves after an interval of time. It is the most important criteria that have to be considered during design. It is both useful and harmful to engineering systems. Unwanted vibrations may cause rapid wearing of machine parts, excessive stress, etc. Usually, in industries, the workers deal with powered hand tools. Clinical studies have shown that the operators of hand-held power tools are prone to develop various vibration-induced disorders of the hand and arm, which are collectively referred to as “Hand-Arm Vibration Syndrome (HAVS)”. Prolonged, intensive exposure to hand transmitted vibrations has been associated with a series of disorders in the vascular, sensorineural, musculoskeletal structures of the human fingers and hand-arm system.

The characteristics of HAVS, generated by the operation of power tools are considered to be affected by the dynamics of coupled tool hand systems. Hence the vibration transmission characteristics of power tools and proper vibration attenuation mechanism have to be investigated. The primary objective of the seminar is to analyze the vibration transmissibility in the finger tip[1], the hand-arm system under different postures [2]. The primary technique used in the study is the “Vibration Power Absorption Density (VPAD)” technique. As a means to eliminate vibration-induced disorders, an anti-vibration glove [3] is analyzed. Mechanical equivalent models of the fingertip and hand-arm system with gloves are developed.