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A series of unique long crack da/dN-delta K experiments that employedperiodic overloads to eliminate crack closure were used to determine both the mode I andthe mode II crack closure-free crack propagation behavior of normalized SAE 1045 steel.A good correlation was found between the mode I and mode II crack growth rate curves.Similarly, there was a good correlation between short crack growth rate data taken fromthe literature and the present crack closure-free long crack data. Short and long crackdata for all of the modes fall into a single scatter band, and the threshold stress intensityis about the same for all the data sets.INTRODUCTION