利用三维数字图像相关技术研究了常温下不同厚度5456铝镁合金板状试件在加载过程中的锯齿形屈服现象及其变形分布. 统计分析锯齿跌落幅值和周期发现, 2者均随应变增大而增大, 且锯齿周期随厚度增大而增大, 而锯齿幅值与厚度相关性较弱. 在拉伸方向应变场和离面位移场中观察到了Portevin-Le Chatelier (PLC)带, PLC带宽不随应力跌落幅值变化而变化, 随试件厚度增大而增大; PLC带倾角与应力跌落幅值、试件厚度无关, 约为60°. 将锯齿幅值和变形信息相联系, 获得了锯齿幅值与带内最大应变成正比关系这一规律. 通过变形时域分析发现, PLC带引起局部拉伸方向应变突增的同时, 也引起相同区域离面位移的突变.

One of the key issues to deeply understand the intrinsic mechanism of Portevin-Le Chatelier (PLC) phenomenon is to analyze the spatial distribution and the evolution of the deformation in PLC bands, associated with serrated yielding. In this work, an investigation was carried out with 5456 aluminium magnesium alloy sheet specimens of different thicknesses at room temperature by using three dimensional digital image correlation (3D-DIC) method, which focused itself on the deformation analysis within serrated yielding under different loading procedures. After statistically analyzing loading curves, it is found that the average amplitude and average period increase with increasing strain. Moreover, there is a positive correlation between the average period and the thickness of specimen, while the average amplitude and the thickness of specimen are independent to some degree. In addition, the experimental result also indicates that the width of the PLC band increases with increasing thickness of the specimen. However, the spatial analysis in PLC bands proves that the angle between the PLC band and the tensile direction is about 60°, which is irrelevant to the specimen thickness and the serration amplitude. Furthermore, it is also found that PLC bands of out-of-plane displacement coincide with bands of strain in the tensile direction by temporal analysis. Most importantly, the experimental result shows that the serration amplitude is proportional to the maximum strain in PLC band when PLC band occurs.