Development of Techniques for Incorporating Buffet Loads in Fatigue DesignSpectra. Volume 1. Analysis Development and Test Results

摘要

Two procedures have been developed to simplify the generation of combined buffetand maneuver load histories. They are intended for use in the early stages of design when only limited wind tunnel and analytical buffet information is available. In the first method, power spectral density (PSD) curves are recorded or predicted at each angle of attack and dynamic pressure condition. Random amplitude load histories are then generated from each PSD curve. The second technique uses the root-mean-square, or RMS, of the buffet loads to generate constant amplitude blocks of buffet cycles at each angle of attack and dynamic condition. Random amplitude cycles are, therefore, replaced by constant amplitude loads causing equivalent fatigue damage. Experimental results using both buffet spectrum generation models are presented. Titanium and aluminum specimens were tested to obtain fatigue crack initiation and crack growth data. All the tests used a plate with a hole as specimen geometry. Fatigue lives obtained with the simplified constant amplitude model are compared with the results using the more complex random amplitude method. The constant amplitude model is a viable method for rapid buffet fatigue prediction, and requires minimum data.