SYMPOSIA PAPER Published: 01 January 1988

A Method for Determining Crack Opening Load from Load-Displacement Data


The fatigue crack opening load is determined as the tangent point on the ascending load-displacement data between the curved portion and the upper linear region. A model for the “unzipping” behavior of the crack indicats that the curved portion of the load-deflection curve is second order. The opening load is determined by a nonlinear, least squares fit of the data to the model, which optimally locates the tangent point of the two curves. The method provided consistent results for determining opening load Pop for 7475-T731 aluminum using data from a crack tip opening gage.

Author Information

Carman, CD
General Dynamics Corporation, Fort Worth, TX
Turner, CC
General Motors Corporation, Dayton, OH
Hillberry, BM
School of Mechanical Engineering, Purdue University, West Lafayette, IN
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Developed by Committee: E08
Pages: 214–221
DOI: 10.1520/STP27210S
ISBN-EB: 978-0-8031-5052-2
ISBN-13: 978-0-8031-0996-4