双剪切试样在镍基单晶合金蠕变变形损伤和寿命研究中的应用

APPLICATION OF THE DOUBLE SHEAR SPECIMENS IN THE STUDY OF THE CREEP DAMAGE AND RUPTURE OF THE NICKEL-BASE SINGLE CRYSTAL SUPERALLOYS

在对不同滑移系的双剪切试样进行蠕变实验的基础上,结合单向应力拉伸蠕变实验,并利用晶体滑移各向异性蠕变损伤本构模型和有限元程序,对双剪切蠕变试样进行了研究.结果表明,双剪切试样受剪区域的应力状态基本为均匀分布且随蠕变时间变化很小.大部分受剪区域为单滑移系开动.提出的基于蠕变γ＇相筏化规律的蠕变损伤本构模型,结合有限元（FEM）分析可以很好地描述双剪切试样的蠕变损伤规律,并可以和单向应力状态的实验结果联系起来.双剪切试样可以用来研究镍基单晶合金蠕变性能的晶体取向相关性.实验表明这种晶体取向相关性与开动滑移系类型及γ＇相筏化规律相关.

Double shear creep specimen made of nickel-based single crystal superalloys can be loaded directly on its slip systems, i.e. the applied shear stress is along the slip direction on the slip plane, so that it can be used to study the creep behavior of slip systems. Based on the experiments of the double shear creep specimens in different orientations and the uniaxial tensile creep experiments at 950℃, the creep and damage behavior of the double shear creep specimens was studied systematically with the help of a creep damage crystallographic constitutive relationship and the finite element method. The results show that there is a near uniform stress state in the shear zone. And the uniform stress is almost independent of the creep time. In the center part of shear zone, only one slip system was activated. The creep damage crystallographic constitutive relationship can be used to model the creep behavior of the double shear creep specimens. And there is a relationship between the creep behavior of the double shear creep specimens and the uniaxial tensile creep specimens. The crystallographic anisotropy can be studied by the double shear creep specimens, which is dependent on activated slip systems and the rafting of γ' phase.