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对服役多年的高速列车用7N01铝合金材料进行疲劳裂纹扩展速率试验,其对数坐标系中的疲劳裂纹扩展速率da/d N与应力强度因子ΔK的关系呈折线形式。与未服役材料对比,在裂纹扩展初期阶段,裂纹扩展速率降低。选取两种原始铝合金材料进行107次预循环应力作用后的疲劳裂纹扩展速率试验,研究低于疲劳极限的预循环应力对材料断裂力学性能的影响。结果表明:经预循环应力作用的材料,其da/d N与ΔK的关系曲线在裂纹扩展初期(对应于低应力强度因子阶段)均出现折转现象。对试验数据的回归分析表明:预循环应力的作用使得材料的断裂力学性能有所提高,预循环应力对材料产生“锻炼”效应。
The test of fatigue crack growth rate of 7N01 aluminum alloy for high speed trains with many years of service has a broken line in the logarithmic coordinate system, da / d N and stress intensity factor ΔK. Compared with the unused material, the crack growth rate decreases in the early stage of crack growth. The fatigue crack growth rate of 107 aluminum alloy materials subjected to pre-cycle stress was selected to study the effect of pre-cyclic stress below the fatigue limit on the fracture mechanics properties. The results show that the curves of da / d N and ΔK in the material subjected to pre-cyclic stress show a turning-over phenomenon at the initial stage of crack propagation (corresponding to the low stress intensity factor stage). The regression analysis of the experimental data shows that the effect of pre-cyclic stress improves the fracture mechanics properties of the material, and the pre-cyclic stress has the effect of “exercise” on the material.