采用实验和数值建模方法探究微成形中材料变形行为和晶粒变形行为的关系.拉伸实验结果表明,流动应力的离散度随厚度晶粒尺寸比(T/d)的减小而增大,这与流动应力的变化规律相反.显微硬度测试结果表明,每个晶粒都有其独特的变形行为且随机分布于试样中.含晶粒数量越少的试样越容易形成易变形区和发生变形集中现象.最后,建立了一个同时考虑晶粒尺寸、几何尺寸和个体晶粒变形行为的尺寸依赖模型,并通过对比实验证实了该模型的有效性和实用性.
To describe the relationship between the whole material deformation behavior and each grain deformation behavior in micro-forming, experimental and numerical modelling methods were employed. Tensile test results reveal that contrary to the value of flow stress, the scatter of flow stress decreases with the increase of thickness-to-grain diameter (T/d) ratio. Microhardness evaluation results show that each grain owns unique deformation behavior and randomly distributes in each specimen. The specimen with less number of grains would be more likely to form an easy deformation zone and produce the concentration of plastic deformation. Based on the experiment results, a size-dependent model considering the effects of grain size, geometry size, and the deformation behavior of each grain was developed. And the effectiveness and practicability of the size-dependent model were verified by experimental results.
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