Experimental setup for measuring the mechanical behavior of loaded thin compliant joints with highest precision

Abstract

Compliant mechanisms with flexure hinges represent a defining element of many precision devices in various fields of science and technology. Due to their importance, the ability of modeling their behavior with high precision represents the key for a further enhancement of their performance. The present scientific work contributes to the experimental verification of distinct mechanical models for thin semicircular flexure hinges. For this purpose an experimental setup for the load application on the hinge has been developed, designed and set up. The device is designed to precisely determine the rotational stiffness of thin flexure hinges in their elastic range with a minimal notch height of 50, 75 and 100 ➭m, but can be applied in a wider context in other applications as well. Two sets of hinges were analyzed, both manufactured by wire EDM in different companies. Although both sets were made with the same geometric dimensions, pronounced differences in their stiffness were measured. It is demonstrated that manufacturing has a large impact on the stiffness of the hinges because it affects the resulting geometry in the microscopic scale. The experimental results for one of the hinge sets are in good agreement with the calculations using the finite element method. Further research is required to confirm this trend. This would provide solid evidence for the invalidity of existing analytical stiffness equations for flexure hinges in the considered thickness range.