Repeatability of Joint-Dominated Deployable Masts

Citation

Stohlman, Olive Remington (2011) Repeatability of Joint-Dominated Deployable Masts. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/D3AR-G573. https://resolver.caltech.edu/CaltechTHESIS:05242011-022845109

Abstract

Deployable masts are a class of structure that can be stowed in a small volume and expanded into long, slender, and stable booms. Their greatest benefit as space structures is their packing ratio: masts can typically be packed to a fraction of their deployed length at a diameter only modestly wider than their deployed width. This thesis is concerned with precision deployable masts, which can be stowed and deployed with repeatability of the tip position of better than 1 mm over 60 m. The methods of investigation are experimental measurements of a sample mast and numerical modeling of the mast with specially attention to hysteretic joints.

A test article of an ADAM mast was used for the experimental work. Two categories of experi- ment were pursued: measurements of mast components as inputs to the model, and measurements of full bays as validation cases for the model. Measurements of the longeron ball end joint friction, cable preload, and latch behavior are of particular note, and were evaluated for their variability. Further measurements were made of a bay in torsion and a short two-bay mast in shear, showing that there is residual displacement in this mast after shear loading is applied and released.

The modeling approach is described in detail, with attention to the treatment of the mast latches, which lock the structure in its deployed configuration. A user element subroutine was used within the framework of the Abaqus finite element analysis solver to model the behavior of the latches with high fidelity.

Validation cases for the model are presented in comparison with experimental observations of a two-bay mast. These cases show that the model captures a number of important and complex nonlinear effects of the hysteretic mast components. Parametric studies of the impacts of component behaviors and modeling practices are explored, emphasizing the impacts of part variability and the idealization of the mast latching mechanisms.

Thesis Files