国产A508-3钢小尺寸拉伸样品的拉伸颈缩行为研究

对不同厚度国产A508-3钢小尺寸拉伸样品进行了室温拉伸试验，分析了拉伸性能及颈缩段参数，并基于有限元逆运算构建了小尺寸拉伸样品拉伸过程的GTN（Gurson-Tvergaard-Needleman）细观损伤模型，研究了厚度对小尺寸拉伸样品拉伸颈缩行为的影响规律与机理。试验结果表明，小尺寸拉伸样品在变形过程中发生了弹性变形、均匀塑性变形和颈缩变形；随着样品厚度由0.75 mm降低至0.30 mm，屈服强度、抗拉强度和均匀延伸率无明显变化，非均匀延伸率及总延伸率逐渐降低，颈缩角逐渐增大，断裂角在厚度降低至0.50 mm后逐渐增大。GTN细观损伤模型中用于表征空洞形核和融合率的参数在0.30 mm样品中明显降低，此结果与小尺寸拉伸样品颈缩行为规律相互印证。

Necking Behavior of Small Tensile Specimen of Domestic A508-3 Steel

Tensile tests were carried out on small tensile specimens of domestic A508-3 steel with different thicknesses at room temperature, and the tensile properties and necking parameters were analyzed. Based on the inverse finite element method, the Gurson-Tvergaard-Needleman (GTN) meso-damage model of small tensile specimens were established according to tensile test. And then the effect and the mechanism of thickness on necking behavior of small tensile specimens were analyzed. The experimental results show that all specimens exhibit elastic deformation, uniform plastic deformation and necking deformation during the tensile tests. Little significant effect of specimen thickness on yield strength, ultra tensile strength and uniform elongation were observed. However, when the thickness of the small tensile specimens decrease from 0.75 mm to 0.30 mm, the non-uniform elongation and total elongation decrease significantly, and the necking angle increases significantly. Additionally, when the thicknesses of the small tensile specimens decrease from 0.50 mm to 0.30 mm, the fracture angles increase obviously. According to the GTN meso-damage model analysis, the parameters used to characterize the cavity nucleation and fusion rate significantly decrease in the 0.30 mm thickness specimen, which indicate that the nucleation and fusion of the cavity become more difficult and the resistance to necking increase in the necking stage. The results of GTN meso-damage model for the necking behavior of the miniature specimens are consistent with the tensile tests.