叶片外物损伤的实验模拟及其疲劳强度的研究

Investigations into Simulation Test and Fatigue Strength of Foreign Object Damage of Blades

关键词:  叶片  外物损伤  步进法  疲劳强度 

Key words:  Blade  Foreign object damage  Step-test  Fatigue strength

摘要:

研究了空气炮法模拟外物损伤叶片的可行性,分析了外物损伤对模拟叶片疲劳强度的影响规律。用空气炮发射以300m/s左右速度发射直径1~4mm的钢珠,冲击模拟叶片,空气炮法在发射速度控制和撞击缺口深度方面具有较强的可控性及可重复性。采用光学和扫描电子显微镜对外物损伤的宏观和微观特征进行了观察,冲击损伤处具有材料丢失、塑性变形、剪切撕裂、应力集中、微裂纹、空穴结构和材料的折叠等特征。采用步进法对部分外物损伤模拟叶片进行了高周疲劳强度测试,试验结果比较分散,且冲击损伤引起的高周疲劳强度下降不随缺口深度的增加而单调变化,表明物损伤模拟叶片的疲劳强度是受缺口的宏观特征、微观特征等综合因素的影响。 

Abstract:

The validation of foreign object damage (FOD) of blades simulated by the gas gun and the effects of FOD on the fatigue strength of simulated blades are investigated. The specimens are impacted by the steel balls with different diameters of 1mm, 2mm, 3mm and 4mm at about 300m/s, which shows good repeatability and control in impact velocity and depth of dent after impact. The macroscopic and the microcosmic feature of the dent are observed through optical and scanning electronic microscopy .The features like material loss, plastic deformation, shear tear, stress concentration, micro notch, droplet structure and material fold etc. are obviously found in the impact area. Then the High Cycle Fatigue test of the typical specimen is done by the step-test method and fatigue strength of simulated FOD blade exhibits a relative scatter trend. It is found that the strength of the specimen does not change monotonously along with the depth of the dent. It means that the strength of the specimen is influenced by various factors, such as the macroscopic and the microcosmic feature of the dent. 