Optimization of hybrid component-level opportunistic maintenance strategy with dual-source ordering

To reduce operational losses from EMU maintenance shutdowns while ensuring safety, this study develops an integrated optimization model combining hybrid opportunistic maintenance with dual-source spare parts procurement under imperfect maintenance. Scheduled maintenance is applied to non-critical components, while critical ones use reliability-based maintenance for cost-effective, safe operations. Dynamic triggers based on mileage and reliability thresholds optimize timing adaptively. To handle spare parts uncertainty, the model integrates dual-source procurement—routine and emergency orders—with inventory controls such as stock limits and reorder points. A proportional factor further adjusts maintenance timing based on available opportunities. A case study on EMU bogie systems shows 13.5% cost savings over non-opportunistic strategies and 4.8% over single-component approaches, while downtime decreases by 4.8% and 9.2%, respectively. The framework supports coordinated maintenance and inventory decisions for complex engineering systems.