Modeling mechanical responses of fingertip to dynamic loading.
Wu-JZ; Dong-RG; Rakheja-S; Schopper-AW
Proceedings of the International Society of Biomechanics XVIII Congress, July 8-13, 2001, Zurich, Switzerland. H Gerber and R Muller, eds., New York: Pergamon, 2001 Jul; :1-3
Extended exposure to mechanical vibration has been related to many vascular, sensorineural and musculoskeletal disorders of the hand-arm system, frequently termed the "hand-arm vibration syndrome" (HAVS). The purpose of the present study is to simulate numerically the responses of fingertip to vibratory loading. A two-dimensional, nonlinear finite element model of a fingertip has been devleoped to study the deformations and strain fields of the soft tissue. The model incorporates the most essential anatomical elements of a fingertip, such as soft tissue, bone and nail (Fig. 1A). The finger is assumed to be in contact with a steel plate, simulating the interaction between hand and a vibrating machine tool or handle. The soft tissue is assumed to be nonlinearly visco-elastic; the nail, bone, and steel plate were considered to be fixed; the steel plate was subjected to prescribed sinusoidal vibrations. Owing to relatively large deformations of the soft tissue under specified static and dynamic loading, Lagrangian large deformation theory was applied in the present analysis. The deformation pattern of the fingertip (Fig. 1B) and the results derived from the analyses suggest local compressive strains in excess of 90% and thus justify the use of large deformation formulations. The analyses were performed under different static load, and vibrations of different frequencies and magnitudes, to study the time-dependent deformation behavior of fingertip under cyclic loading. The results are further analyzed to derive the time-dependent distributions of displacement, strain, stress, and strain energy density within the soft tissue. Our simulations show that contact force and loading frequency have a strong influence on the dynamic responses of figertip, which agree with the experimental observations reported in the literature. The present model provides a useful tool to study the mechanism of tissue degeneration under vibratory loading encountered during operation of hand-held power tools.
Mechanical-properties; Models; Vibration-exposure; Simulation-methods; Vibration; Occupational-exposure; Exposure-levels; Exposure-assessment
Proceedings of the International Society of Biomechanics XVIII Congress