15-15Ti奥氏体不锈钢热老化小尺寸试样单轴拉伸行为的GTN微观损伤模型研究

Study on Uniaxial Tensile Behavior of Thermally Aged Small-Sized Sample of 15-15Ti Austenitic Stainless Steel by a GTN Microscopic Damage Model

通过加速热老化试验模拟了15-15Ti奥氏体不锈钢的辐照效应,构建了Ramberg-Osgood力学本构模型和GTN(Gurson-Tvergaard-Needleman)微观损伤模型。结合有限元方法,探讨了热老化不同时间的15-15Ti奥氏体不锈钢小尺寸试样在不同温度拉伸试验过程中的应力-应变响应行为和损伤断裂过程。结果表明:热老化小尺寸试样中有少量碳化物析出和大量σ相形成,导致其抗拉强度和屈服强度显著下降;未热老化试样的拉伸断口中有大量韧窝,为韧性断裂,而热老化试样的拉伸断口中韧窝数量明显减少,析出相周围有撕裂棱,为脆性断裂;热老化试样标距段的应力集中和颈缩均延迟发生;热老化试样的断裂应变明显小于未热老化试样;热老化能促使小尺寸试样中孔洞的聚集和增多,从而加速失效。

Irradiation effect of 15-15Ti austenitic stainless steel was simulated by accelerated thermal aging test.Ramberg-Osgood mechanical constitutive model and GTN(Gurson-Tvergaard-Needleman)microscopic damage model were established.The stress-strain response behavior and damage fracture process of 15-15Ti austenitic stainless steel small-sized samples thermally aged for different periods of time during tensile testing at different temperatures were approached combined with finite element method.The results showed that(a)a small amount of carbide precipitated and a large amount ofσphases formed in the thermally aged small-sized sample,thus resulting in a significant decrease in its tensile strength and yield strength;(b)the sample not thermally aged exhibited a large number of dimples in tensile fracture,was ductile fracture,whereas the thermally aged sample exhibited significantly reduced dimples in tensile fracture and the tearing edges around precipitated phase,was brittle fracture;(c)occurrences of both the stress concentration and necking in gauge section of the thermally aged samples were delayed;(d)breaking strain of the thermally aged sample was significantly less than that of the sample not thermally aged;and(e)the thermal aging was capable of promoting the accumulation and increase of holes in small-sized sample,thus accelerating failure.