The effects of scratches and shot peening on the fatigue crack growth of aluminum alloy 2024-T3

The primary objective of the research was to investigate the effects of scratch, shot peening and specimen orientation on the crack growth of aluminum alloy 2024-T3. An experimental study was performed to determine the crack growth rates of scratched-then-shot peened specimens and scratched specimens in various specimen orientations. Tests were conducted at a constant stress amplitude with different stress ratios. The crack growth rate of a scratched specimen increased with increasing the scratch depth. Glass shot peening significantly reduced crack growth rates of scratched specimens. The crack growth data of scratched-then-peened specimens were similar to those of as-received specimens at low and intermediate {dollar}rm Delta K{dollar} ranges. The specimen orientation had effects on the fatigue life but no effects on the crack growth rate. Increase in the positive stress ratio increased crack growth rates of specimens. However, the change of the negative stress ratio resulted in different effects. In addition, it was found that the scratch exhibited small crack growth behavior. This behavior is related to the crack's shape change occurring after crack's going through the thickness of a specimen. An analysis model for stress intensity factor {dollar}rm Delta Ksb{lcub}scr{rcub}{dollar} for scratched specimens was developed. Crack growth rates of scratched specimens showed a good relationship with {dollar}rm Delta Ksb{lcub}scr{rcub}.{dollar}...