Surface Flaw Crack Growth in Plates of Finite Thickness

摘要

This combined experimental and analytical study was directed at predicting the growth and shape change of surface flaws under axial loading using crack growth data obtained from simple compact tension specimens. The experimental effort aimed at automating surface crack growth testing using 2219-T851 aluminum specimens. Test variable included different stress ratios, flaw sizes and shapes. Tests were conducted using constant amplitude loading with marker bands to measure shape changes. Compilance techniques were employed in an attempt to automate crack growth data acquistion. Although useful for running tests, these techniques lacked adequate sensitivity when compared to visual measurements. The analytical effort was directed at determining which crack growth models and stress intensity solutions could best predict the growth and shape change of surface flaws. The characterization of surface flaws as semi-ellipses and the independence of crack growth rate and direction were addressed. The resulting model was successful in predicting growth and shape changes under most conditions, but did not adequately predict the effects of load interaction under high stress ratio conditions.