Compliance and Fatigue Life Analysis of U-shape Flexure Hinge

This paper establishes four models of U-shape flexure hinges with different notch shapes and structure parameters, and presents the close-form compliance equations for the four structure types of U-shape flexure hinges. The compliance of the flexure hinges is developed based on the Castiglione's second theorem and calculus theory. A relationship between compliances and structure parameters is deduced using the models. The influences of the notch structure parameters on the compliance of the flexure hinges are investigated. Moreover, fatigue life of U-shape flexure hinges is studied by finite element analysis, the results show that the fatigue life of flexure hinge increases gradually with the increasing of flexure hinge center thickness t and hinge notch width m. With the increasing of the major axis of the ellipse a and semi minor axis of the ellipse b, the fatigue life of flexure hinge fluctuates locally, the general trend is a gradual decrease. The stress and fatigue life of U-shape flexure hinges and arc flexure hinge are compared. The results show that the reliability of U-shape flexure hinge is higher than that of circular arc flexure hinge.