Adaptation of Cross-Axis Flexural Pivots for Specific Load-Deformation Regimes.

Abstract

Cross-axis flexural pivots (x-pivots) hold promise as frictionless bearings for applications that require moderate angular displacement under large uniaxial tensile loads. Stress analysis through three-dimensional finite element modeling provides a framework for designing x-pivots to withstand expected loads and deformations for a large number of cycles. This type of analysis is especially important in protecting the mechanism against nonlinear stress effects induced by combined bending and tensile loading, which can prove catastrophic in certain loading regimes. Building on our prior research, we focus in this article on new techniques for mitigating the two most impactful nonlinear stress effects: blade buckling and bowstringing. Specifically, we highlight the ways in which design modifications-to local geometry of the variable-thickness blades, geometry of the complete x-pivot mechanism, and the relationship between the x-pivot and the absolute global system-can be leveraged to tailor mechanism performance to the loads and deformations required of a given application. We use finite element analysis to evaluate the effects of these design modifications in the context of different planar and six degrees-of-freedom loading regimes. Our results demonstrate that informed design changes can significantly reduce peak stresses over a fixed loading sequence, which is an important step toward practical implementation of x-pivots in real-world systems.