Study on local cyclic plastic behavior of aluminum alloy with notched parts based on digital image correlation method

ZHAO Xun; LI Jian; GE Junming; SUN Tao; ZHAO Yan; WANG Zhenming; ZHU Jianguo

doi:10.16579/j.issn.1001.9669.2026.07.009

Abstract：[Objective]Plastic collapse failure frequently occurs in notched aluminum alloy pressure vessels.The influence mechanism of notch type and size on local cyclic plastic behavior was revealed to provide reference for accurate fatigue life prediction of notched components.[Methods]Firstly,2024-T4 aluminum alloy specimens with U-shaped and V-shaped notches of different sizes were fabricated,and stress-controlled low-cycle fatigue tests were carried out.Secondly,full-cycle strain field data at the notch root were obtained by digital image correlation method,and the evolution law of local ratcheting strain with cycle number was analyzed.Then,key parameters such as stress concentration factor were calculated by finite element software,and a fatigue life prediction model considering notch stress concentration factor and root steady-state ratcheting strain rate was established.Finally,the microscopic mechanism of fatigue damage differences among different notches was verified by fracture morphology observation.[Results]The results show that the steady-state ratcheting strain rate decreases significantly and the fatigue life increases when the radius of U-shaped notch increases from 0.2 mm to 2 mm and the angle of V-shaped notch increases from 15° to 150°.The proposed prediction model has higher accuracy than the traditional Manson-Coffin model,and the mean square errors of prediction for U-shaped and V-shaped notches are reduced by 0.004 48 and 0.004 51,respectively.The differences in fracture microscopic characteristics are consistent with the variation laws of macroscopic ratcheting strain rate and fatigue life.