An Experimental Method for Measuring Stress Intensity Factor Distributions in Three-Dimensional Problems

Abstract

In this paper, an attempt has been made to briefly chart the progress over a period of some 30 years during which the writer and his associates have tried to effect a marriage between the well known, frozen stress method (augmented with the methods of Tardy and Post for refining the near tip fringe analysis), with the principles of fracture mechanics, using an extension of an idea proposed by Irwin. Although a conscious effort was made by the writer to keep the elements of the method as simple as possible so as to allow the application to as broad a range of practical problems as possible while maintaining reasonable engineering accuracy, there were occasional diversions into supporting developments such as the singularity change when a crack intersects a free boundary and the combined use of the stress freezing method with moire. In general, the guidelines employed by the writer included: Use of well established experimental methods; simple algorithms where singularity dominated data zones were revealed by the data itself; applicability to any crack shapes even when unknown apriori; and engineering accuracy of {+-}5% in K{sub 1} in Mode 1 dominated problems.