Analysis of Nonlinear Elastic Deformations for a Homogeneous Beam at Varying Tip Loads and Pitch Angles

摘要

The Princeton beam experiments of 1975 were performed in hopes of producing viable data for beam nonlinear elastic deformation models in hopes of improving helicopter main beam designs. The recorded data, specifically for homogeneous beams of 7075 aluminum, have been referenced as a baseline for the past thirty years to validate numerous computer models and theories in an effort to build beams capable of withstanding aeroelastic, static, and dynamic loading. The purpose of this study is to improve upon the data recorded in 1975 using newer technologies including a laser distance meter, digital inclinometer, and three-dimensional traverse to test X-axis, Y-axis, Z-axis and angular displacements for varying tip loads and pitch angles. Initial beam deformations due to machining stresses were included in the testing, and the beam was analyzed at tip loads between zero and four pounds for positive and negative pitch angles in fifteen-degree increments from zero to ninety degrees. The results were analyzed in numerous comparisons between the different tip loads and pitch angles, and the overall results were compared with Princeton beam data to ensure their validity. The experimental results showed an improvement in terms of precision as well as a relatively close correlation with Princeton beam data. There were some displacement discrepancies, but such differences can be examined in the future. The results can be used for beam vibrational mode and frequency testing as the beam's geometry can be reproduced graphically and computer model verifications, allowing for more precise computer models for homogeneous nonlinear beam displacements.