Measurement of Crack-Tip Stress Distributions by X-Ray Diffraction

Variable amplitude fatigue crack growth behavior — a short overview

“…X-ray measurements have shown that upon application of an overload, the residual compressive zone is enlarged compared to the baseline loading [63,64] and that the magnitude of the residual stress may be of the order of the yield stress [65]. When an overload induced compressive residual stress is superimposed on the applied stresses, a reduction of the local tip stress is predicted, which might be expected to generate retardation of crack growth rates [1].…”

Experimental and Theoretical Analyses of the Load Sequence Effects on Fatigue Crack Growth Resistance

“…(32) (52) The relations (46) and (52) demonstrate that the exponents of fatigue life and crack growth equations (or the slopes of the corresponding curves in log-log coordinates) are interrelated. They also show that the exponent a in the two parameter driving force, AK*, is decreasing from Vi at the near threshold region to n7 (1+n') at the Paris region.…”

“…These investigations have resulted in proposal of several crack growth retardation theories. In general, these theories attribute delayed retardation behavior to crack closure [27], residual stresses [49, 50,51], or a combination of these mechanisms [52].…”

“…Allison [52] conducted a similar study on 1045 steel to determine the ' residual stresses before and after the application of overload. Fig.35 shows the residual stress profiles before and after the overload application and the maximum stress profile at the base load.…”

Fatigue Crack Tip Plastic Strain in High-Strength Aluminum Alloys

“…Allison [21] has measured the stress distribution near a loaded fatigue crack tip in carbon steel using an X-ray beam size of 625 pm. This is the only known work which might be compared with the data of Fig.…”