对Al-4%Cu合金试样拉伸实验的锯齿形应力曲线进行了系统的统计分析, 研究了锯齿应力跌幅、跌落时间以及再加载时间等特征物理量随应变、试样厚度 和加载应变率的时序演化规律. 结果表明, 跌落时间对应变不敏感; 1和2 mm厚 试样的平均应力跌幅和平均再加载时间均随应变线性增加, 3 mm厚试样的统计结 果比较复杂. 展示了PLC效应中自组织临界性存在的证据, 并通过与经典沙堆 模型的对比, 结合动态应变时效原理和位错理论, 解释了PLC变形带形成的非线性机制.
A systematic statistical analysis of the characteristics of the Portevin-Le Chartelier (PLC) effect in Al-4%Cu alloy, including the stress drop amplitude and the reloading time, etc., is carried out. The drop duration is found to be a constant independent of the strain. The average stress drop amplitude and the average reloading time of 1 and 2 mm thick samples increase with strain linearly, while the cases of 3 mm thick samples are much more complicated. The evidence of self--organized criticality is demonstrated, and the nonlinear mechanism in the PLC effect is also explained by comparing with the classic sand--pile model, and by combining with the dynamic strain aging (DSA) principle and the dislocation dynamics.
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