SEDL / STP / STP982-EB / STP27210S

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

Carman, CD
General Dynamics Corporation, Fort Worth, TX

Turner, CC
General Motors Corporation, Dayton, OH

Hillberry, BM
Professor, School of Mechanical Engineering, Purdue University, West Lafayette, IN

Pages: 8    Published: Jan 1988

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Abstract

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 P^op for 7475-T731 aluminum using data from a crack tip opening gage.