An exponential equation of fatigue crack growth in titanium

Titanium and its alloys are known for not showing a high degree of linearity of the fatigue crack growth (FCG) data. In the present work, the FCG curves of commercially pure titanium are evaluated using the conventional Paris approach and a new exponential equation named αβ model, which allows for considering non-linear da/dN–ΔK relationships. The following load ratios (min/max) were adopted for the fatigue tests: R = 0.05, 0.1, 0.15, 0.30, 0.50 and 0.60. The αβ model is more effective than Paris-based equations in describing the FCG behavior of titanium and can be easily generalized to take in account a range of stress ratios. This new model also qualifies as a promising tool to assess the FCG curves of other structural materials.