Schneider, Judith A.
Newman, James C., Jr.
Smith, Donald M.
Date of Degree
Graduate Thesis - Open Access
Master of Science
James Worth Bagley College of Engineering
Traditionally, pre-cracking has been performed under tension-tension loading, followed by a load reduction scheme to obtain fatigue crack growth rate data in the near threshold regime. These data have been shown to exhibit load history effects due to remote crack closure. An alternative test method has been developed to minimize these load history effects. This test procedure uses compression pre-cracking to initiate a crack, followed by constant amplitude loading to grow the crack to failure. Compression-compression (C-C) loading as a means of forming a starter crack for fatigue crack growth is a relatively new concept. Cracks grown under C-C loading emanate from the notch tip due to a tensile residual stress field formed during the unloading cycle. The subsequent constant amplitude steady-state crack growth is free of load history effects, after crack growth beyond several compressive plastic zone sizes, and therefore will give a better steady-state representation of the near-threshold regime. A more in-depth examination at this phenomenon is performed herein.
McKnight, Dustin Henry, "The Use of Compression Precracking Constant Amplitude (CPCA) Test Method to Obtain Near-Threshold Fatigue Crack Growth Behavior In AA7075-T7351" (2005). Theses and Dissertations MSU. 4683.