Abstract

This study presents a finite element (FE) model of the human hand-arm system to derive natural frequencies and mode shapes. The FE model is calibrated by considering modal parameters obtained from experimental vibration analyzed by using operational modal analysis (OMA) and transmissibility. Modal and harmonic analyses of the FE model are performed for two boundary conditions. The first one considers fixed shoulder condition while the second one introduces the trunk in order to permit motion of the shoulder. The results show that the natural frequencies of the second model that permits shoulder motion are comparable with those determined from measurements. Especially, the natural frequency about 12 Hz, which is corresponding to the frequency of maximum weight in ISO-5349-1 (2001), is not present in the model with fixed shoulder condition, while it appears in the second model. The results of the present study suggest that improved finite element models of the human hand-arm system may reveal hand-arm injury mechanism, the understanding of which may assist in deriving appropriate frequency weightings for the assessment of different components of the hand-arm vibration syndrome.

Highlights

  • Two boundary conditions were considered: the first is a fixed shoulder condition and the second is a model with the trunk to permit shoulder motion

  • The resonant frequencies were compared with those estimated from the measured experimental transmissibility responses and operational modal analysis using the autogressive moving average technique (OMA-autoregressive moving average (ARMA))

  • The results showed that the model that permits shoulder motion is a better model since the some of the derived resonant frequencies are closely related to the resonant frequencies determined from measured transmissibility responses and OMA-ARMA technique

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Summary

Introduction

Tions of the hand-arm of the operators of hand-held power tools. The hypothesis of the present study is that finite element model of the human hand-arm system will yield reliable identification of the resonant frequencies and mode shapes of the hand-arm system. This study presents finite element (FE) model of the hand-arm system to determine the natural frequencies and mode shapes of different substructures of the human hand-arm. In order to calibrate these models and determine which model is more representative of the human hand-arm, the natural frequencies of the FE models are compared with those derived from measured transmissibility and those obtained from operational modal analysis (OMA). The posture assumed by an operator of the hand-held power tool depends on the type of tool and the kind of the operation being performed, the extended hand-arm posture, as shown, is modeled in this study for simplicity and in order to compare the FE model results with available experimental data The posture assumed by an operator of the hand-held power tool depends on the type of tool and the kind of the operation being performed, the extended hand-arm posture, as shown in Figure 1, is modeled in this study for simplicity and in order to compare the FE model results with available experimental data

Methods
FE model with fixed shoulder
FE model with motion of the shoulder
Modal and harmonic analyses of FE models
Estimation of resonant frequencies from measured transmissibility responses
Natural frequencies and mode shapes of the hand-arm system
Conclusions
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