Evaluation of an Inflated Beam Model Applied to Everted Tubes

TL;DR

This study validates the inflated beam model for everted tubes by comparing experimental tip deflections with theoretical predictions, demonstrating its accuracy and providing numerical and iterative methods for deflection and force calculations.

Contribution

It introduces a numerical and iterative approach for modeling everted tube deflections and validates the inflated beam assumption through experimental data.

Findings

Everted and uneverted beams have similar tip deflections.

The model accurately predicts tip deflections with small errors.

Everted beams buckled at 83% of theoretical buckling load.

Abstract

Everted tubes have often been modeled as inflated beams to determine transverse and axial buckling conditions. This paper seeks to validate the assumption that an everted tube can be modeled in this way. The tip deflections of everted and uneverted beams under transverse cantilever loads are compared with a tip deflection model that was first developed for aerospace applications. LDPE and silicone coated nylon beams were tested; everted and uneverted beams showed similar tip deflection. The literature model best fit the tip deflection of LDPE tubes with an average tip deflection error of 6 mm, while the nylon tubes had an average tip deflection error of 16.4 mm. Everted beams of both materials buckled at 83% of the theoretical buckling condition while straight beams collapsed at 109% of the theoretical buckling condition. The curvature of everted beams was estimated from a tip load and a known displacement showing relative errors of 14.2% and 17.3% for LDPE and nylon beams respectively. This paper shows a numerical method for determining inflated beam deflection. It also provides an iterative method for computing static tip pose and applied wall forces in a known environment.