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.