考虑大变形的涡轮叶片热应力有限元算法研究

Study on finite element method of thermal stress ofturbine blade under large deformation

以航空发动机涡轮叶片为研究对象,基于有限单元法,采用六面体八节点单元,提出考虑几何非线性影响的热应力计算方法;使用B-bar和混合网格技术提高了复杂网格的求解精度;采用更新拉格朗日格式考虑了大变形条件下的几何非线性问题,使用Newton-Raphson迭代方法进行涡轮叶片热应力数值求解。通过缺口平板、立方体、悬臂梁、圆环算例,与ABAQUS对比,热应力、大变形模型的相对精度达到99%;最后讨论了考虑大变形对热应力的影响,在温度、气动、离心力载荷工况下,考虑大变形后,涡轮叶片变形量减小,热应力降低,相对计算精度提高4.67%。提出的考虑大变形的热应力数值算法,可用于涡轮叶片径向间隙设计和服役寿命评估,为航空发动机零部件精细化设计提供理论和计算工具支撑。

Focusing on the finite element method for simulating the large deformation of turbine blade under varied loads,a method for calculating the thermal stress coupled with geometric nonlinearity was proposed based on the eight-node hexahedron element.B-bar and hybrid element technologies were used to improve the precision of results;the updated-Lagrangian(UL)incremental approach was presented for the simulation of large deformation,and the Newton-Raphson iterative method was utilized to numerically calculate the thermal stress of turbine blade.Compared with ABAQUS,the relative accuracy of thermal stress and large deformation models reached 99%through examples of notched plate,cube,cantilever beam,and ring;finally,the influence of considering large deformation on thermal stress was discussed.Under temperature,aerodynamic,and centrifugal load conditions,the radial deformation of turbine blades and thermal stress decreased,and relative calculation accuracy improved by 4.67%.This research is of great benefit to the design of radial clearance and assessment of low cycle fatigue life of turbine blade,and furthermore it can provide theoretical and computational support for exquisite design of aeroengine components.