Imperfect maintenance policy for a degradation-shock model considering dynamic environment effects and varying failure thresholds

The maintenance of engineering systems operating in dynamic environments is a challenging task due to the combined effects of natural degradation, random shocks, and evolving environmental conditions. To address these challenges, this study develops a comprehensive framework that integrates environmental dynamics into degradation-shock models to analyze their effects on system behaviour. It incorporates environment-dependent hard failure thresholds and accounts for imperfect maintenance. Environmental conditions influence not only the system’s degradation rate but also its shock tolerance, particularly through varying hard failure thresholds. The diminishing effectiveness of imperfect maintenance with repeated activities is also considered. Closed-form expressions for maintenance-related indicators are derived, supporting optimal decision-making for periodic inspection strategies. A decision model is established to maximize the long-term average profit rate, optimizing variables, such as the number of imperfect repairs and inspection intervals. The framework is validated through a case study on floating offshore wind turbines and a sensitivity analysis, highlighting the critical interplay between environmental dynamics, maintenance effectiveness, and system performance.