Influence of hole cold expansion on fatigue resistance of 2024 aluminum alloy

Abstract

The effect of stress concentration around the hole easily leads to fatigue failure of aircraft structures, and usually causes catastrophic accidents. In order to elucidate the influence of cold expansion on the fatigue life of AA2024-T351 specimens, fatigue tests of specimens before and after cold expansion were accomplished on high frequency fatigue test machine. Combining the finite element simulation with X-ray diffraction measurement, the evolution of residual stress around the hole was thus investigated. Meanwhile, scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed to observe the fatigue fracture morphology, fatigue striation and microstructure characteristics, and to explore the influence of microstructure features on fatigue life. Research results show that the cold expansion with 0.4 mm can significantly improve the fatigue resistance of AA2024-T351 specimens, and the fatigue limit can be increased by about 42%.

Keywords

• hole cold expansion
• fatigue life
• 2024-t351 aluminum alloy
• finite element simulation
• residual stress