ISSN: 0090-3973
Page Count: 11

Effects of Fixturing Mass on Dynamic Strain Errors in Structural Fatigue Testing

Hewitt, RL
Senior research officer,,Institute for Aerospace Research, National Research Council of Canada,,Ontario,,

(Received 22 September 1999; accepted 30 June 2000)

Abstract

Improvements in control systems have allowed significant increases in testing frequencies for full-scale aircraft structural fatigue tests. This means that it is possible to be testing at frequencies that result in significant dynamic strains, with consequent over-testing.

This paper presents an analysis of a simple cantilever beam as a representation of a test on an aircraft wing. Using a state space formulation and the MatLab mathematical programming system, comparisons between static and dynamic strains for various locations on the beam are made for a variety of loading arrangements.

It is shown that significant dynamic strain errors will occur at testing frequencies above about 10% of the first natural frequency of the specimen itself. The errors can increase significantly due to the mass of the fixturing, and are further exacerbated by static counterbalancing.

Keywords:
aircraft, strain, dynamic errors, control, fatigue, full-scale testing, modeling, simulation

Paper ID: JTE12137J
DOI: 10.1520/JTE12137J
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