To properly model complex aircraft structure an understanding of mixed mode, also known as three dimensional, crack growth is required. The Center for Aircraft Structural Life Extension (CAStLE) at the United States Air Force (USAF) Academy is in the process of completing a project to generate three dimensional (3D) crack growth data for thin sheet (1.6 mm) aluminum alloy (AA) 2024-T351 and predict the measured crack growth rate, crack trajectory and residual strength using state-of-the-art stress analysis and life prediction tools. To produce the mixed mode crack trajectory and residual strength mechanical testing data ARCAN specimens were used with a modified ARCAN fixture. The ARCAN test fixture allows the ARCAN sample to be rotated to produce different mixtures ofmode I and mode II loading (with 0 being pure tension/compression (mode I) and 90 pure shear (mode II)). ARCAN specimens were tested at angles of 0, 30, 60 and 75 under constant K starting loads followed by a increasing test and a stress ratio of 0.1. A travelling optical microscope was used to track crack trajectory and crack growth. While mechanical testing was being completed, we also developed a crack prediction model of the ARCAN specimen using FRANC3D NG, a solid modeling, mesh generation and fracture mechanics code from Cornell University Fracture Group. FRANC3D NG should be able to predict the cracking behavior observed m the ARCAN tests. A parallel effort was also undertaken to develop an engineering model of mixed mode crack growth where contributions to mode I and mode II growth.
Three diminsional crack growth prediction
2009
34 Seiten, 24 Bilder, 4 Tabellen, 13 Quellen
Aufsatz (Konferenz)
Englisch
Three dimensional crack growth prediction
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