The development of a new artificial model of a finger for assessing transmitted vibrations

Prolonged exposure of the hand to tool-induced vibrations is associated with the occurrence of conditions such as vibration white finger. This study involves the development of a new artificial model that approximates both loading and vibration behaviour of the human finger. The layered system uses polypropylene "bones", encased in a cylinder of low modulus, room-temperature curing silicone gel (to replicate subcutaneous tissues), with an outer layer of latex (to replicate the dermis and epidermis). A protocol for manufacture was developed and dynamic mechanical analysis was carried out on a range of gels in order to choose a range close to the mechanical properties of the human finger. The load-deflection behaviour under quasi-static loading was obtained using an indenter. The indentation measurements were then compared with a set of validation data obtained from human participant testing under the same conditions. A 2-D FE model of the finger was also used to assess vibration responses using existing parameters for a human finger and those obtained from the tested materials. Vibration analysis was conducted under swept sinusoidal excitations ranging from 10 to 400Hz whilst the FE finger model was pressed 6mm toward the handle. Results were found to compare well. This synthetic test-bed and protocol can now be used in future experiments for assessing finger-transmitted vibrations. For instance, it can aid in assessing anti-vibration glove materials without the need for human subjects and provide consistent control of test parameters such as grip force.