压气机叶片的损伤容限研究

本文用断裂力学方法对压气机和风扇转子叶片作损伤容限分析。采用20节点立体元对叶片作应力场和位移场计算,用裂纹表面位移法求解裂尖应力强度因子K_Ⅰ、K_Ⅱ及K_Ⅲ随裂纹长度a变化的关系。根据叶片材料的断裂韧性K_IC、叶片径向伸长量δ_c以及自振频率偏移量f_c值来确定转子叶片失效的准则及临界裂纹长度a_c值。利用Paris公式并考虑到高周振动应力对低周疲劳裂纹扩展的影响求得叶片的损伤容限寿命N_f。文中给出了某压气机叶片的算例。为了研究自振频率随裂纹长度变化的关系,进行了叶片振动实验 

RESEARCH ON DAMAGE TOLERANCE OF COMPRESSOR BLADE

This paper discribes the damage tolerance analysis of compressor blade by fracture mechanics.Finite element method with 20 nodes solid elements is used for the stress calculation.A displacement method is provided to determine the stress intensity factors K Ⅰ,K Ⅱ and K Ⅲ versus crack length a of the blade.Based on the material toughness K ⅠC ,additional extension δ c and deviation of natural frequency f c of the cracked blade,the failure criterion of the compressor blade is discussed and the critical crack length is determined.By the use of Pris formula and in consideration of the influence of high cycles on low cycle fatigue crack propagation,the damage tolerance life of the blade is obtained.As an example,a calculation of a certain compressor blade is given.In order to investigate the relation of natural frequency versus crack length,the vibration of compressor blades has been tested.The presented method can be used for the strength evaluation of turbo jet engine.