Ratcheting fatigue reliability and sensitivity analysis of hydraulic pipe under in-service loadings

Considering the critical role of ratcheting fatigue reliability in determining the structural integrity of hydraulic pipelines, the development of robust probabilistic fatigue theories becomes essential for optimizing design schemes. This paper focuses on the ratcheting fatigue reliability and sensitivity analysis of the hydraulic pipe subjected to sustained in-service conditions. Firstly, the deterministic finite element model analysis is adopted to determine the equivalent stress amplitude at the critical location of the pipe, thereby establishing the limit state function. An advanced experimental setup is developed to replicate the in-service loadings on the hydraulic pipe. The finite element model is systematically validated through the experimental method. Subsequently, the Kriging-based single-loop Monte Carlo simulation method is established to evaluate the ratcheting reliability of the hydraulic pipe. The effectiveness and accuracy of the developed method are validated by comparison with the traditional quasi-Monte Carlo simulation method. The influence of cyclic force amplitude and operating internal pressure on the ratcheting failure probability of the hydraulic pipe are assessed to provide guidance for reliability-based design. Finally, the ratcheting fatigue sensitivity of input random variables is evaluated to advance the theoretical framework and practical implementations of statistical analysis for the optimum design of the hydraulic pipe.