Abstract
Flexure hinges as the displacement guiding and amplifying mechanism or sensing component are widely used for micro-actuators and sensors. However, the existing flexure hinges, leaf-spring or notch type, cause serious stress concentration which severely weaken the fatigue life of compliance mechanism. Therefore, developing long fatigue life flexure hinges is very important for high working frequency actuators and sensors, such as fast-tool-servo. Corner-fillet leaf-spring type flexure hinge could provide large displacement with lower stress. Stiffness expressions of it with both fixed-fixed and fixed-guided boundary conditions are derived by using Castigliano’s theorem. The main influence factors for stress concentration are investigated and the formulas of stress concentration factor are obtained in terms of ratio of fillet radius to the minimum thickness. These analytical formulas have been verified by comparing with finite element analysis (FEA) results. Stress-life method is chosen to research the influence of fillet radius on fatigue life and the results indicate fillet radius can improve fatigue life of flexure hinge effectively. The proposed analytical solution is the fundamental of optimal design of a leaf-spring type flexure hinge based mechanism with fatigue life constraints.
Highlights
Compliant mechanisms are widely used in micro actuator [1,2,3], micromanipulator [4], displacement amplifier [5], micro/nano positioning stages [6,7,8,9], accelerometers [10,11,12] and sensors [13, 14]
Due to the large displacement output and its popular used in actuators and sensors, corner-fillet leaf-spring type flexure hinges(CFLSFH) are proposed for long fatigue life and large displacement in this paper, and the key work is to develop an analytic expression of the stiffness, and determine an optimal ratio of radium to the minimum thickness under fatigue life constraint
This paper proposes analytic solutions of stiffness of CFLSFH in fixed-fixed and fixed-guided boundary condition, which are widely used in micro-position stages and sensors
Summary
Compliant mechanisms are widely used in micro actuator [1,2,3], micromanipulator [4], displacement amplifier [5], micro/nano positioning stages [6,7,8,9], accelerometers [10,11,12] and sensors [13, 14]. Due to the large displacement output and its popular used in actuators and sensors, corner-fillet leaf-spring type flexure hinges(CFLSFH) are proposed for long fatigue life and large displacement in this paper, and the key work is to develop an analytic expression of the stiffness, and determine an optimal ratio of radium to the minimum thickness under fatigue life constraint. 65 Li Rui-qi et al.: Analytical Solution of Stiffness for a Corner-Fillet Leaf-Spring Type Flexure Hinge with a Long Fatigue Life. CFLSFHs are considered as leaf spring for simple design when fillet radius is small, the assumption is inaccuracy for large fillet radius CFLSFHs. CFLSFHs are cross-section varying beams, which is far more difficult to obtain the analytic solution of stiffness for either fixed-fixed or fixed-guided condition. Fatigue life of CFLSFH is researched and the case results indicate that fillet can improve the fatigue life effectively
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