Influence of Elliptical Hole’s Inclination Angle on Fatigue Crack Growth Behavior of Titanium Alloy

Abstract

In this paper, the fatigue crack growth behavior of compact tensile (CT) specimens fabricated from TC4ELI alloy is examined with elliptical holes of different inclination angles (α = 0°, 30°, 60°, 90°). The study includes growth life (N), path, and growth rate (da/dN). These analyses employ the extended finite element method (XFEM) considering different prefabricated crack lengths. Additionally, the conventional finite element method (CFEM) is used to analyze the stress intensity factor amplitude (ΔK). An elastoplastic analysis is conducted to calculate the changes in the plastic zone, the stress distribution near the crack tip, and the plastic strain energy of the specimen. The findings suggest that the hole can hinder crack growth and cause growth path to deflect. Elliptical hole can reduce the degree of ΔK_v and ΔK_I of the crack to a certain extent, while increasing ΔK_II. This behavior contributes to a decrease in da/dN and an increase in N. As the inclination angle increases, its hindering influence on the crack growth diminishes, leading to a weakening of influence on the crack growth. The tendency for the plastic zone and the stress near the crack tip to increase with crack growth is also suppressed. Plastic strain energy also increases as the inclination angle increases. Additionally, an increase in prefabricated crack length weakens the hindering influence of the hole. However, the relationship between the hindering influence and the inclination angle remains unchanged. Finally, the analysis results for growth path and da/dN are verified through experimental methods.