虑及高循环疲劳的裂纹型外物损伤叶片的可用极限

为了发展一种航空发动机钛合金风扇/压气机叶片外物损伤（FOD）可用极限的确定方法，对典型叶片的可用极限进行了调研，基于裂纹门槛值原理建立了应力比相关的FOD裂纹不扩展等值曲线图，根据TC4钛合金不同应力比下材料的疲劳耐久性极限强度对比了两种裂纹不扩展判据的适用性，通过该方法确定了一种典型风扇叶片撕裂/裂纹型外物损伤的可用极限。结果表明:现有维修手册中对叶片不同区域不同类型FOD的可用极限要求不同，FOD可用极限的主要限制尺寸为损伤深度，深度限制一般在1mm以内。通过裂纹不扩展等值曲线图确定的典型风扇叶片撕裂/裂纹型FOD可用极限分布在0.020~0.525mm内，可用极限沿叶片展向分布可分为三个区域:叶根区可用极限约0.08mm，叶中区可用极限约0.3mm，叶尖区可用极限约0.5mm，越靠近叶根可用极限越小。 

Serviceable limits of a crack type foreign object damaged blade considering high cycle fatigue

To develop a method of determining serviceable limits of foreign object damage (FOD) in aeroengine titanium fan/compressor blades, researches of serviceable limits in typical blades were firstly conducted, then stress ratio related contour maps of FOD crack non-propagation were established based on the principle of crack growth threshold, the suitability of two crack non-propagation criteria was compared according to the TC4 titanium material fatigue durability limit strength at different stress ratios, finally, serviceable limits of tearing/crack type foreign object damages in a typical fan blade were determined by this method. The results show that, in the present maintenance books, serviceable limit requirements are different for different types of FOD and different blade regions, the main limited size of FOD serviceable limits is damage depth, the depth limitation is generally less than 1mm. The tearing/crack type FOD serviceable limits of the typical fan blade determined by the contour maps of crack non-propagation are within the range of 0.020-0.525mm, the serviceable limit distribution along the blade span can be divided into three regions: the serviceable limit in the blade root area is about 0.08mm, the serviceable limit in the blade middle area is about 0.3mm, and the serviceable limit in the blade tip area is about 0.5mm, the closer to blade root means the smaller serviceable limit.