An Innovative and Robust Approach to Studying Fatigue Properties of Aluminum 7075 Bar Utilizing Miniature I-Beam Geometry

Aerospace structures are optimally designed and analyzed to specifically-defined engineering parameters. Thus, there is a strong drive to understand fatigue properties of materials, enabling an engineer determine their influence on these constraints. Space structures are usually designed to minimize weight and volume; hence thin designs utilizing strong, lightweight materials are ultimately desired. The goal of this research is to address an innovative testing technique of material properties not readily obtained from current test methods. The properties studied in this research include crack growth rates of small diameter rods in both the radial and transverse grain directions under a constant-amplitude tensile load at room temperature. This approach is illustrated on I-beam specimen manufactured from Aluminum 7075-T7351 Bar. The crack growth rates from the experimental data are then compared with literature results for plates, sheets, and extrusions of the same material. The research completed reveals the test results have comparable [Paris relationship] exponential m-values. The significance of quantifying small diameter metallic material properties have potential for great impact on the future of space structures, but are not limited to one part of the industry.M.S.Committee Chair: John W. Holmes, Ph. D.; Committee Member: Andrew Makeev, Ph. D.; Committee Member: David McDowell, Ph. D