Udimet 720 Li 高温变形特性的粘塑性本构建模研究

采用Chaboche统一粘塑性本构方程,对Udimet 720 Li在700℃时的单调拉伸、循环加载及蠕变特性等复杂的高温变形现象进行了建模研究.探讨了Chaboche本构理论对这些变形现象进行建模的形式,并特别针对快速各向同性软化和非对称循环加载时的平均应力松弛现象,对Chaboche本构理论进行了修正和变化.将经过修正的Chaboche本构理论,与Levenberg-Marquadt非线性优化算法相结合,编制了材料参数优化程序,得到了材料参数值.研究表明,经过修正的Chaboche本构模型可较好地建模镍基高温合金Udimet 720 Li在高温下的各种变形行为.

Visco-plastic constitutive modeling of inelastic deformation of Udimet 720 Li at high temperature

The mechanical deformations of a Nickel-based superalloy Udimet 720 Li was modeled simultaneously by the Chaboche unified viscoplastic constitutive theory under tensile, cyclic and creep loading conditions at 700℃. To describing the phenomena of cyclic relaxation of mean stress under strain controlled cyclic loading and fast isotropic softening during unloading, the equations of internal variables of the theory were modified. A program code of parameter optimization was compiled with 1-dimentional Chaboche model by Levenberg-Marquadt nonlinear algorithm. A global strategy for model parameters optimization was proposed, which produced good results. The numerical simulations showed that this modified Chaboche model has sufficient capability of modeling various mechanical behaviors under complex loading conditions.