M.S. Thesis Presentation by Doug Miller
Thursday, April 11, 2002

(Drs. Steven Johnson and Rami Haj-Ali, co-advisors)

"Stress Intensity Factors for Circumferential Part-Through Cracks from Holes in Hollow Cylinders Subjected to Tension and Bending Loads"

Abstract

Hollow cylinders loaded in remote tension or bending can be found in many important structural applications, such as aircraft landing gear and piping systems. In many cases, failure of these structures could result in serious injury or loss of life. The critical nature of these types of structures requires that they be designed not only for strength but for durability and damage tolerance as well. This makes it necessary to have accurate stress analyses of part-through cracks for damage tolerance assessments. A problem that has not been addressed in the literature is for a part-through crack emanating from a hole in a hollow cylinder. This study presents three-dimensional finite element (FE) models for evaluating the stress intensity factors (SIFs) of two symmetric circumferential part-through cracks emanating from the external corner of a hole in a hollow cylinder. The crack shape is a quarter-ellipse mapped onto the circular cylinder. A wide range of cylinder and crack geometric parameters is investigated. In order to generate finite element meshes for a variety of geometric configurations, an automatic mesh generation computer program is developed. SIFs are developed along the crack front for remote tension and bending, and are calculated using the virtual crack closure technique (VCCT). The convergence of the SIFs based on the number of crack-front elements is studied, along with the effects of the cylinder and crack geometry. The SIFs are presented as nondimensional curves to make them easy to apply to engineering problems. The newly generated results from this study should be useful for performing crack growth or residual strength analyses for the part-through crack configurations considered.