Numerical assessment of the structural integrity of UAV shafts reconditioned by thermal spraying

The present study investigates the structural behavior of unmanned aerial vehicle (UAV) shafts reconditioned through thermal spray coatings, with emphasis on stress distribution and integrity under operational loading conditions. UAV shaft components are subjected to combined axial, torsional, and bending loads, leading to progressive surface degradation and potential failure in critical regions. Thermal spraying represents an efficient reconditioning technique; however, the addition of a coating layer alters the mechanical response of the component, particularly at geometric discontinuities. A three-dimensional finite element model was developed to simulate the mechanical response of coated shafts, incorporating both substrate and coating material properties. The analysis considers realistic service loads and focuses on key geometric parameters, including shaft diameter, fillet radius, and coating thickness. A simulation plane of 9 tests was employed to evaluate the influence of these parameters on stress distribution in critical regions, namely the frontal area, cylindrical section, and fillet zone. The results demonstrate that the fillet radius is the most influential parameter governing stress concentration, while coating thickness significantly affects stress redistribution, especially at the coating–substrate interface. Higher stiffness coatings tend to shift stress concentrations toward the interface, whereas lower stiffness coatings exhibit elevated stress levels within the coating layer. Although no statistically significant effects were identified due to limited dataset size, consistent trends indicate the dominant role of geometric parameters in controlling stress behavior. The findings provide valuable guidelines for the design and optimization of reconditioned UAV shafts, highlighting the necessity of balancing coating thickness and geometric features to minimize stress concentrations and ensure structural reliability.