This paper describes a combined experimental and numerical investigation aimed at identifying the physical mechanisms and modeling errors that are the culprits for the lack of correlation between experimental measurements and analytical predictions of the modal parameters of helicopters airframes. The identification of the major contributors to this lack of correlation is an indispensable first step to actual modification and improvement of modeling processes and tools. The study focuses on simple comfigurations: panels with lap and butt joints fastened with HI-LITE fasteners or rivets. Impact hammer tests were used to measure their natural frequencies, mode shapes, and damping ratios. The results were compared with numerical predictions based on current industry modeling practices. Next, shaker tests were used to investigate the nonlinear behavior of the fastened connections. The most significant discrepancy between measurements and predictions were due to modeling idealizations of the joints. Nonlinearities were also important, though to a lesser extent.
Improving modal parameter predictions for jointed airframe panels. Part I: Experiments
Verbesserung der Modalparameter-Vorhersagen für Hubschrauberrumpfstrukturverbindungen. Teil I: Experimente
Journal of the American Helicopter Society ; 43 , 2 ; 156-163
1998
8 Seiten, 17 Bilder, 3 Tabellen, 16 Quellen
Article (Journal)
English
Hubschrauber , Rumpfwerk , Rahmen (Fahrzeug) , Leichtbauweise , experimentelle Untersuchung , analytische Untersuchung , Versuchsaufbau , Korrelation , physikalische Eigenschaft , Zuverlässigkeitsvoraussage , Modalparameter , Qualitätsverbesserung , Konfiguration , Überlappnaht (Schweißen) , Nietverbindung , Schlagfestigkeitsprüfung , Nichtlinearität , Resonanzfrequenz , Dämpfungsfaktor , Strukturdynamik
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