Physics-Based Predictive Modeling of Fatigue Crack Propagation Using Strain Field Analytics in Aeronautical Fuselage Aluminum Structures

Introduction: Predictive modeling of fatigue crack propagation in metallic structures is essential for structural integrity assessment and prognostics-driven maintenance in aerospace systems. While sensing technologies enable damage detection, the translation of strain measurements into quantitative crack size remains a major analytical challenge. This work presents a physics-based modeling framework aimed at deriving an explicit analytical relationship between distributed strain fields and crack length evolution in aeronautical aluminum components.

Methods: A novel analytical formulation was developed grounded in Linear Fracture Mechanics and stress concentration theory. The model describes crack-tip stress redistribution and its spatial decay along the structure, enabling strain estimation at discrete sensor locations. By incorporating geometric correction factors, gauge positioning, and nominal strain normalization, the formulation allows crack length to be solved as an inverse problem without requiring direct load input. The resulting equation establishes a closed-form relationship linking localized strain amplification to crack size. Experimental fatigue datasets obtained from instrumented aluminum 6082-T6 specimens were used exclusively for calibration and validation purposes, alongside independent non-destructive crack measurements.

Results: The predictive formulation demonstrated strong capability to reconstruct crack growth trajectories under different fatigue loading scenarios. High correlation was achieved between analytically predicted and experimentally measured crack lengths, with coefficients above 0.97. The model captured strain concentration gradients associated with crack propagation and maintained millimetric accuracy across most of the growth regime, with deviations primarily linked to sensor spacing effects.

Conclusions: The proposed model provides a robust analytical tool for strain-based crack quantification in metallic structures. The load-independent formulation, reduced sensing requirements, and compatibility with computational implementation position it as a scalable approach for digital twins, prognostics, and multiscale structural integrity modeling in advanced aerospace applications.