Analysis of Sub-Critical Cracking in a Ti-5Al-2.5Sn Liquid Hydrogen Control Valve
A liquid hydrogen main fuel control valve for a rocket engine failed by fracture of the Ti-5Al-2.5Sn body during the last of a series of static engine test firings. Fractographic, metallurgical, and stress analyses determined that a combination of fatigue and unexpected aqueous stress-corrosion cracking initiated and propagated the crack which caused failure. The failure analysis approach and its results are described to illustrate how fractography and fracture mechanics, together with a knowledge of the crack initiation and propagation mechanisms of the valve material under various stress states and environments, helped investigators to trace the cause of failure.
D. A. Meyn, R. A. Bayles, Analysis of Sub-Critical Cracking in a Ti-5Al-2.5Sn Liquid Hydrogen Control Valve, ASM Failure Analysis Case Histories: Air and Spacecraft, ASM International, 2019, https://doi.org/10.31399/asm.fach.aero.c9001558
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