SYMPOSIA PAPER Published: 01 January 1988

A Statistical Approach to Crack Closure Determination


A statistical procedure was employed to determine opening loads from load versus crack opening displacement data records taken during fatigue crack growth rate testing of a high strength steel weldment. The slope of the upper linear portion of the load-deflection curve served as a control value, which was compared with slopes calculated over successive intervals of the curve. Opening loads were defined using a statistical test to consistently determine deviation from linearity on the upper portion of the load deflection curve. These loads depended on the size of intervals taken and the number of data pairs in each interval. Data records of various densities, degrees of scatter, and degrees of curvature were analyzed to evaluate the procedure's ability to determine consistent opening loads. By systematically accounting for test dependent data scatter, or “noise,” a consistent definition of opening load was achieved.

Author Information

Roberson, LJ
David Taylor Research Center, Bethesda, MD
Kirk, MT
David Taylor Research Center, Bethesda, MD
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Developed by Committee: E08
Pages: 230–246
DOI: 10.1520/STP27212S
ISBN-EB: 978-0-8031-5052-2
ISBN-13: 978-0-8031-0996-4