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在微塑性成形过程中,虽然零件的宏观尺寸达到了毫米或微米级,但其微观组织却没有发生明显的变化,材料的表层晶粒尺寸也就越来越趋近零件的几何尺寸,导致塑性成形规律呈现出与宏观大尺寸零件不同的尺寸效应现象。对四种厚度的304不锈钢薄板试样进行了单向拉伸试验和微弯曲试验,测量了薄板的厚度。结果表明,随着薄板厚度的减小,塑性变形区内表层晶粒的位错滑移变化对力学性能和无量纲弯矩的影响越来越显著,表现出“越薄越强”的尺寸效应现象。引入修正的Hall-Petch公式与修正的Nix-Gao应变梯度模型,使力学性能和无量纲弯矩的预测和试验结果吻合。
In the micro-plastic forming process, although the macroscopic size of the part has reached the level of millimeters or micrometers, the microstructure does not change obviously. The surface grain size of the material also approaches the geometric dimension of the part, resulting in plasticity Forming rules show a large size with the macroscopic size of the phenomenon of different parts. The uniaxial tension test and microbending test of four kinds of thickness 304 stainless steel sheets were carried out, and the thickness of the sheets was measured. The results show that with the decrease of sheet thickness, the influence of the dislocation slip of surface grains in the plastic deformation zone on the mechanical properties and the moment of non-dimensional bending becomes more and more obvious, showing that the thinner and stronger Size effect phenomenon. The modified Hall-Petch formula and modified Nix-Gao strain gradient model are introduced to make the prediction and test results of mechanical properties and non-dimensional moments coincide.