铝合金薄板冲击后疲劳试验与谱载寿命

Tests of low velocity impact are performed on the sheets of AAs 2524-T3 and 7075-T62, respectively, with four different impact forces, and static and fatigue experiments are conducted on the intact and post-impact sheets under static tensile, constant amplitude and block spectrum loading. The impact-dent size, static and fatigue properties, and spectrum-loading life are determined, with the effect of impact on fatigue characteristics and damage mechanism analyzed and discussed from fractographic and experimental observations. An S-N-K_t surface model is proposed to depict fatigue characteristics for fatigue lifetime prediction of post-impact sheets subjected to block spectrum loading. A new concept is applied for experimental data and a reasonable agreement obtained between the theoretical and experimental results, demonstrating the effective and practical use of the developed surface model. A nonlinear elastic-plastic FE model based on the Johnson-Cook constitutive equation is generated to model the residual stress patterns and stress concentration around the impact-dent, and fatigue lives of post-impact sheets of AAs 2524-T3 and 7075-T62 subjected to block spectrum loading are predicted from the S-N-K_t surface model. Good agreements have been achieved between predictions and experiments.