Computational Fretting-Fatigue Analysis of Braided Nitinol Non-Vascular Stents with Multi-Point Contact Coupling

Braided Nitinol non-vascular stents are valued for their flexibility and biocompatibility in luminal applications, but are susceptible to fretting wear and fatigue under long-term physiological loading, which can lead to fracture, migration, and severe associated clinical complications. Existing studies, focusing on macro-mechanics or single-point contact configurations, fail to capture multi-point contact coupling in braided structures, thereby limiting the accurate prediction of their long-term durability. To bridge this gap, this study developed a multiscale computational framework integrating stent-level macromechanics with wire-interfacial micromechanics. The primary focus was on simulating fretting wear evolution and predicting fatigue life at the critical braided unit level. Within this framework, a finite element (FE) model incorporating a localized Archard wear model and nonlinear mesh adaptivity was developed to simulate multi-point wear progression. Fatigue life was dynamically predicted by combining the Smith-Watson-Topper (SWT) multiaxial fatigue criterion and Miner's linear cumulative damage rule. The results revealed that contact pressure evolved from an initial concentrated single-peak pattern to a dispersed multi-peak pattern, reflecting a load redistribution mechanism within the braided structure. Wear increased nonlinearly across all contact regions. The Y region, experiencing the highest normal load, exhibited the most severe wear and the fastest damage accumulation, reaching failure at approximately 3.32×10⁶ cycles. Simulation results are in good agreement with experimental data, with a relative deviation of 9.94%. The validated multi-scale framework and computational model enable accurate multi-point contact fretting wear analysis of braided units. This work provides an effective and systematic tool for accurate assessment of stent wear performance, fatigue life prediction, and structural optimization guidance, thereby contributing to improving the long-term clinical reliability of braided stents.