Integrated geometric refinement of Ti-6Al-4V containment casings balancing mass reduction and constitutive sensitivity under impact loading

Abstract

The prevention of catastrophic fracture during fan blade-out (FBO) events is a critical requirement for aero-engine safety certification. While the suppression of void growth under triaxial compression is a known mechanical principle, this research establishes how macroscopic geometric compliance can be used to actively control the local triaxiality history during high-strain-rate impacts. Rather than treating parameter sensitivity and structural mass as isolated variables, this study shows that increasing global structural flexibility physically forces the local dynamic stress tensor into a compressive state, preventing fracture. Utilizing a finite element model of a Trent 1000-class turbofan, an iterative geometric refinement was performed to minimize casing mass without compromising energy absorption capability. The Johnson–Cook (J–C) plasticity and damage laws for the Ti-6Al-4V alloy served as the baseline, with a conservative limit model developed to account for identified ±5% calibration uncertainties in thermal softening ( m ) and strain rate sensitivity ( C ). Numerical results demonstrate that a 6.3% reduction in casing mass is achievable while maintaining a factor of safety (FS) of 1.25 under nominal loading and 1.66 under conservative material assumptions. The analysis reveals that the optimized, more compliant geometry facilitates beneficial cycles of triaxial compression near −0.7, which suppresses void nucleation and prevents catastrophic perforation. This study provides a validated engineering framework for the design of lightweight, damage-tolerant containment systems that remain resilient even under unfavorable constitutive calibration scenarios.