Mechanisms of Fatigue Crack Initiation and Propagation in Hydropumps NP-89D of Aircraft Tu-154M of Cast Aluminum Alloy AL5

摘要

The paper demonstrates results of quantitative fractographic analyses of in-service fatigued hydropumps NP-89D of cast AL5 Al-based alloy. The model that better describes microcracks threshold taken place from cast porosities is based on Vickers hardness of metal matrix and the {the square root of}area of defects (the {the square root of}area model). Crack growth period estimated by the result of meso-beach marks spacing measurements and stress equivalent calculated by the {the square root of}area model used to discuss causes of the in-service cracking of the pump casing. Shown that damping of self-oscillations with simultaneous decrease in an equivalent stress level of the hydrounit will allow increase operating time up to pump probable failure to more than 10~(10) individual cycles. It will lead to increase in the period of operation of casings without their fatigue cracking more than on two orders.