Measuring and predicting the transmission of vibration through gloves to the hand

• Main Author: Md Rezali, Khairil Anas bin
• Other Authors: Griffin, Michael
• Published: University of Southampton 2015
• Subjects: 620.8
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680673

The main objective of this research was to advance understanding of factors influencing the transmission of vibration through glove materials to the hand and to the fingers. The transmissibility of a glove to the hand depends on two primary factors: the biodynamic response of the hand and the dynamic characteristics of the glove material. Although some of the factors affecting the biodynamic response of the hand and the dynamic characteristics of glove materials have been investigated previously, there is insufficient understanding to be able to predict glove transmissibilities. The apparent mass of the hand, the dynamic stiffness of three glove materials (Foam A, Foam B, and Gel A), and their transmissibilities to the hand were measured with five variables: (a) material thickness (6.4, 12.8, and 19.2 mm), (b) push force (10, 15, and 20 N), (c) contact area (with diameters 12.5. 25.0, and 37.5 mm), (d) vibration magnitude (1, 2, and 4 m/s2 r.m.s.), (e) with and without arm support, and (f) different frequency ranges (10 to 300 Hz and 2 to 50 Hz). With the hand pushing down on a flat surface and vertical vibration, measurements were obtained at the palm of the hand, the thenar eminence, and the index finger. It is concluded that the apparent mass of the hand and the dynamic stiffnesses of the glove materials at high frequencies are predominantly affected by contact area and contact force. A change in contact area or contact force can therefore increase or decrease glove transmissibility. At frequencies greater than 20 Hz, the apparent mass at the palm and the transmissibilities of the glove materials to the palm were similar with and without arm support. At frequencies between 20 and 100 Hz, as the dynamic stiffness of the material decreased, the transmissibility of the material to the palm decreased whereas the transmissibility to the index finger increased. Changes in the vibration magnitude will not have a large effect on glove transmissibility. Using the measured apparent mass of the hand and the measured dynamic stiffnesses of the glove materials, the transmissibility of the materials to the hand were predicted using an impedance model. The predicted transmissibilities were similar to, and showed similar trends to, the measured transmissibilities. The predicted transmissibilities seemed to reflect individual changes in the dynamic response of the hand, suggesting a method of predicting inter-subject variability in glove transmissibility. Simple lumped parameter models of the hand were developed (with two and four degrees-of-freedom) and combined with the dynamic characteristics of glove material (represented by a standard linear viscoelastic model) to predict glove transmissibility to the palm of the hand. The two degree-of-freedom model (representing the material and the hand) consistently provided a prediction of glove transmissibility to the palm that was inferior to the predictions of the four degree-of-freedom model (representing the material, the hand, and the arm), suggesting the exclusion of the dynamic response of the arm affects the ability of a model to predict glove transmissibility to the palm. The research shows that the transmission of vibration through a glove to the palm of the hand or to the finger can be predicted from the dynamic stiffness of the glove material and the apparent mass of the hand. Such predictions will assist the optimisation of glove dynamics, reduce the time to assess the performance of a glove, and reduce the need for testing with human subjects.