FGH97缺口试样基于黏塑性本构的弹塑性响应分析

Analysis of elastoplastic response in FGH97 notched specimens based on viscoplastic constitutive model

针对缺口试样在高温条件下局部区域应力应变难于测量的问题,基于光滑试样材料力学性能试验,优化得到550℃粉末高温合金FGH97的Chaboche黏塑性统一本构方程参数,并将其应用到FGH97缺口试样单调拉伸及循环加载弹塑性有限元分析中.研究结果表明:①缺口局部区域进入塑性后其应力分布与弹性条件明显不同,随应力增大,最大应力位置向内移动;②在循环载荷条件下,随着循环数的增加,缺口平分线上应力/应变范围变化不大,缺口根部塑性区域出现明显平均应力松弛,并逐渐趋于稳定,导致缺口根部循环载荷比不同于外部施加载荷;③缺口根部塑性区域逐渐增大,但增大的幅度逐渐降低.该研究可为进一步分析缺口构件疲劳寿命影响因素提供支持.

In order to solve the difficulties in measuring local stress and strain,the parameters of Chaboche viscoplastic constitutive equations for powder metallurgy super alloy FGH97 at 550 ℃,which were obtained based on the experiments of material mechanical properties,were used in the elastoplastic FEM（finite element method） analysis of notched specimens subjected to tensile and cyclic loading.The results show that：（1） plastic stress/strain state at notch root is obviously different from elastic one.With the increase of stress,location of maximum stress moves inside.（2） Under cyclic loading,with the increase of cyclic number,the stress and strain range along symmetric path at notch root changes little.Mean stress relaxation occured in the plastic zone at notch root gradually turns to be stable,and it also leads to different cyclic stress ratios compared with the applied load.（3） The plastic zone at notch root gradually increases,but the increasing range gradually decreases.The research result can provide support to further analysis of influencing factors which affect fatigue life of FGH97 notched specimens.