Crack initiation in cyclic compression and its applications

The characteristics and applications of crack initiation under far-field cyclic compressive loads are examined in notched specimens of a lower strength steel. The fatigue cracks, initiated at the notch root due to residual tensile stresses, grow at a progressively decreasing velocity before arresting completely. Simple correlations are explored between the total fatigue crack growth distance and the size of an effective damage zone estimated from the initial crack growth rate. Some important applications of crack initiation in cyclic compression in both long and short fatigue crack problems are demonstrated. Experimental results are presented to show that crack initiation in cyclic compression offers some interesting possibilities for obtaining accelerated estimates of slow fatigue crack growth rates, while minimizing some of the inherent uncertainties arising from the artifacts of conventional test techniques. Possible applications of this method are also discussed with respect to the study of physically-short flaws and of the evaluation of the progressive development closure during fatigue.