Characteristics of Human Fingertips in Shearing Direction.

Abstract

This paper describes characteristics of human fingertips in shearing directions. In the experiment, the shearing force is applied on the thumb, middle, or little finger. Stiffness and viscosity parameters are estimated using Kelvin-Model. Considering contact area, the thumb has the strongest stiffness among the three fingers, and middle and little fingers have the same stiffness. The stiffness depends on the direction of the shearing force. The stiffness in the direction from nail to first joint of finger is stronger than that in the perpendicular direction. As the normal force of gripping increases, the shearing stiffness and viscosity increase without regard to the loading rate of the shearing force. The shearing stiffness has an upper Iimit value, and the viscosity par unit area keeps constant. Moreover, the strain rate of the fingertips is investigated, and it is found that the normal force of gripping affects the stiffness of the fingertips.