Numerical and experimental investigations of the effect of repeated cyclic thermal loads on the strength of materials of recoverable liquid-propellant rocket engines

Elements of the liquid-propellant rocket engines (LPREs) are subject to the action of intense mechanical and thermal loads, which are temporally related to the start-up, normal regime, and switch-off periods of the working cycle. Recoverable LPREs experience these loads many times. Repeated (cyclic) loads lead to the manifestation of processes typical of fatigue, whereby residual stresses and (plastic) deformations are retained and accumulated in the LPRE materials. Numerical investigations using models of the nonstationary thermal and stressed-strained state and the plastic behavior of materials have been performed in order to determine the limiting numbers of loading cycles for the structural materials employed in various units of LPREs. A special computational-experimental procedure is described, which allows these materials to be studied in a stressed-strained state close to that in real LPREs.