基于应变梯度塑性理论的微塑性成形力学性能

不同厚度的T2紫铜试样的单向拉伸、微硬度和微弯曲试验表明，材料的力学行为与内禀的材料特征参数相关：厚度为30μm的板材，其拉伸强度比厚度为150μm的板材提高了28%，平均晶粒尺寸D为50μm的细晶，其拉伸强度比平均晶粒尺寸D为120μm的粗晶拉伸强度提高了33%，拉伸时呈现出“越小越强”的特征；当压痕深度与板材厚度的比值大于0.2时，压入深度越大，压痕硬度越大，呈现出“越大越硬”的现象；回弹角随板料厚度的减小而增大，当材料厚度小于一定值（0.06mm）时，材料的应变梯度硬化效应使得回弹角随板料厚度的变化更为剧烈，这种变化与采用应变梯度塑性理论预测的结果基本一致。

Mechanical Properties of Micro Plastic Forming Based on Strain Gradient Theory

The unilateral stretching, microhardness, and microbending tests of T2 copper samples with different thicknesses show that the mechanical behavior of material is relevant to the intrinsic characteristics of material: the tensile strength of sheet material with thickness of 30μm is increased by 28% compared with that of the sheet material with thickness of 150μm, the tensile strength of the fine grain with average grain size D of 50μm is improved by 33% compared with that of the coarse grain with average grain size D of 120μm, with the “the finer, the stronger” characteristic displayed. When the ratio of the indentation depth to the sheet thickness is more than 0.2, the deeper the indentation is, the harder the indentation is, with the “the deeper, the harder” characteristic displayed. The springback angle decreases as the thickness of the sheet increases. When the thickness of sheet is less than a certain value (0.06mm), the strain gradient hardening effect of the material makes the change of springback angle with the change of sheet thickness stronger. This change is substantially consistent with the results predicted by using the strain gradient plastic theory.