Crack growth life of Ti–3Al–2.5V tubes under internal impulse pressure

This paper presents application of laser micro-machining (LMM) in introducing a longitudinal (axial) semi-elliptical sharp notch as a pre-crack on external surface of Ti–3Al–2.5V tubes to study fatigue crack growth characteristics. The notch root radius was less than 0.03 mm. Internal impulse pressure test results were obtained for the tubes with a LMM notch of 0.23 mm deep and 0.25 aspect ratio under different internal pressure levels. Fatigue crack growth life was predicted for the tubes and validated by the experimental life data. It is observed that all predicted crack growth life data based on both NASGRO equation and Paris’ law are in good agreement with the experimental life data. Modeling and experimental results indicate that LMM is an appropriate tool for introducing a pre-crack to study fatigue crack growth in titanium and possibly other materials.