Newman, James C., Jr.

Committee Member

Daniewics, Steven R.

Committee Member

Lacy, Thomas E.

Date of Degree


Document Type

Graduate Thesis - Open Access


Fatigue-crack-growth-rate tests were conducted on compact tension specimens made of 7050-T7451 aluminum alloy and 9310 steel. Compact tension specimens were tested over a wide range of load ratios (0.1 less than, or equal to R less than, or equal to 0.9) to generate crack-growth-rate data from threshold to near fracture. Three methods were used to generate near threshold data. A crack-closure analysis was performed on both materials using the FASTRAN crack-closure model. The crack-growth-rate data for each material correlated very well and each collapsed onto a nearly unique curve in the low- and mid-rate regimes using the strip-yield model in the FASTRAN life-prediction code. For the 7050 alloy, a constraint factor of α = 1.8 was required, while for the 9310 steel α = 2.5 worked very well in correlating the test data over a very wide range in R values and rates from threshold to near fracture.