Fatigue failure analysis and life prediction of micro-pipelines under heterogeneous random vibration loads in aerospace engines

As space engines advance toward reusability, addressing structural fatigue fractures has become increasingly critical. The small pipelines within these engines are particularly vulnerable to damage from vibration loads, which can lead to cracks and failures, ultimately compromising engine safety. Although random vibration experiments are routinely employed to verify pipeline reliability, detailed research on quantitative fatigue life prediction methods for pipelines under complex pre-load and vibration conditions remains limited. This study investigates the mechanisms of vibration-induced fatigue failure by analyzing random vibration test results. A finite element model (FEM) was developed to simulate the vibration response of pipelines subjected to pre-loaded and heterogeneous vibration excitations. The accuracy of various time-domain and frequency-domain life assessment methods was evaluated, confirming the effectiveness of the multi-axial equivalent stress approach based on Lemaitre stress and the Dirlik frequency-domain model. Moreover, this study demonstrates that the effects of internal pressure, boundary displacement, and attached mass can be linearly superimposed to accurately predict pipeline fatigue lifetimes.