Crystal plasticity prediction method for fatigue crack initiation life of Ti6Al4V ELI titanium alloy based on microstructure characteristics
DU Along
YU Peishi
ZHAO Yuxiang
XU Qiang
ZHAO Junhua
Abstract：Ti6Al4V ELI titanium alloy is widely used in important structures of deep-sea manned equipment due to its excellent mechanical properties.However,during deep-sea service,manned equipment is continuously subjected to complex fatigue loads,which can easily lead to crack initiation and propagation,and in extreme cases,may even lead to catastrophic rupture accidents.Crack initiation is a key factor in determining the overall fatigue life,and accurate prediction of it is essential to ensure the safety of the equipment.Although existing fatigue life analysis methods have been able to reveal the fatigue behavior characteristics of Ti6Al4V ELI titanium alloys to a certain extent,their accuracy is still insufficient when predicting the life of materials with different microstructures.To solve this problem,a realistic microstructure model was reconstructed using electron back scatter diffraction(EBSD)technology,the numerical simulations were conducted based on the crystal plasticity finite element method,and a fatigue crack initiation life prediction model for Ti6Al4V ELI titanium alloy was successfully established.The low-cycle fatigue behavior of dual-phase structured Ti6Al4V ELI titanium alloy was simulated,and two fatigue indicator parameters(FIPs),cumulative plastic slip and cumulative energy dissipation,were introduced to comprehensively assess the extent of damage during fatigue.The results show that the fatigue damage is mainly concentrated in the regions with severe plastic slip and high energy dissipation,especially at the interface location between the α-phase and β-phase.In addition,the tensile asymmetry within the grains leads to lattice rotation,which further exacerbates strain localization and accelerates the evolution of microstructure.By comparing with the experimental lifetime data,it is found that the lifetime prediction method based on cumulative plastic slip exhibits higher accuracy compared with the lifetime prediction method based on cumulative energy dissipation.Meanwhile,the fatigue indicator parameter-based prediction method better reveals the variability of the life of Ti6Al4V ELI titanium alloys with different microstructures compared with the conventional Coffin-Manson(C-M)model.This study not only provides new ideas and methods to improve the accuracy of fatigue crack initiation life prediction for Ti6Al4V ELI titanium alloy,but also provides strong support for the safety and reliability of this material in practical applications.
Keywords：Crystal plasticityFatigue indicator parameterCrack initiationFatigue life predictionTitanium alloy
Publication Date：2025-12-15
Online Publishing Date：2026-09-12(First online date of this platform, not the publication date of the document)
Pages：17( 1-17 )