汽轮机叶轮T型叶根槽半椭圆表面裂纹应力强度因子数值研究

为确定在离心力作用下汽轮机叶轮T型叶根槽半椭圆表面裂纹的应力强度因子，采用三维有限元法求解含裂叶轮的位移场。表面裂纹前缘平方根应力奇异性使用由20节点三维等参块单元退化而成的四分之一节点奇异单元来模拟。在有限元分析中，考虑了叶根与叶根槽的接触作用。对具有不同椭圆率的表面裂纹，通过位移相关技术计算了沿裂纹前缘各点的应力强度因子，研究了裂纹长度对沿裂纹前缘各点应力强度因子的影响。数值结果表明：I型、II型和III型应力强度因子都在表面点达到最大值；随着表面裂纹长度的增大，沿裂纹前缘各点的I型应力强度因子也增大。

Numerical Investigation on Stress Intensity Factors for a Semi-elliptical Surface Crack at the T-root Groove of a Turbine Disc

In order to determine the stress intensity factors (SIFs) for a semi-elliptical surface crack at the T-root groove of a turbine disc under centrifugal forces, three-dimensional finite element method was employed to solve the displacement field of the cracked disc. The square-root stress singularity along the surface crack front was simulated using the quarter point singular elements collapsed by 20-node three-dimensional isoparametric elements. The contact interaction between the blade root and its groove was considered in the finite element analysis. The SIFs along the crack front for the surface crack with different aspect ratios were calculated by displacement correlation techniques, and the effect of the crack length on SIFs along surface crack front were investigated. The numerical results show that the modes I, II and III SIFs reach the maximum values of their individual modes at surface point and the mode I SIFs along the crack front increase as the surface crack length increases.