Failure analysis of low-pressure turbine rotor blades of an aeroengine

Fractographic study showed that the blade bearing No. XRXA 342 has failed by fatigue. The fatigue crack was found to have initiated in the airfoil over a length of 1500-2000 m on the concave surface at a height of about 3 mm from the blade root platform and 9.5 mm from the trailing edge. The progressive crack propagation was over about 30 mm on the concave surface and 20 mm on the convex surface before giving way to final static overload failure. The fracture in the other five blades was found to be under impact load. None of these blades showed any evidences of progressive failure. It is confirmed that after fatigue failure in blade XRXA 342, the dislodged airfoil impacted with these blades leading to their fracture. Hence, these failures and the other damages seen in various engine parts are secondary in nature and they have occurred subsequent to the primary failure in blade XRXA 342