Characterization of Hertzian rolling microslip in precision revolute joints for deployable space structures.

摘要

The capabilities of space-born telescopes are primarily limited by their launch systems, dictating both light-gathering power and resolution, by constricting aperture size. Precision deployable space structure technology enables smaller stowed configurations for launch and a larger deployed operational state in space. The primary engineering difficulties arise from the accuracy and repeatability requirements of the deployed system, where an optical system requires tens of nanometers RMS surface displacement. Recent studies identify that instabilities and errors in a deployable space structure are primarily caused by the stick-slip friction between the contact interfaces of the latches and joints. The intent of this research is to model and characterize the nonlinearities of contact of a precision revolute joint for deployable space structures. The joint is a modified pin-clevis joint, where the deployment mechanism, load-path, and sources of instability are relegated to the contact interfaces of pair of angular contact bearings. This research presents a nonlinear lumped-parameter finite element modeling the nonlinear mechanics of contact to characterize the microdynamic behavior of the angular contact bearings for a precision revolute hinge. The mechanics of contact are based on Hertz contact theory and a numerical simulation subproblem based on the influence function method. The numerical simulation is rigorously validated and is shown to efficiently and effectively model transient rolling contact with varying normal contact forces, where current literature and numerical modeling techniques fail. The in uence of surface roughness and stochastic variations due to manufacturing and assembly are studied in regards to stiffness performance metrics. Rolling hysteresis is identified for various conditions, and a zero-loss rolling mechanism is discovered and investigated. Design implications, capabilities, recommendations, and optimal improvements for the precision hinge design are stated.