Fatigue Life and Crack Growth Behavior of Ti-6Al-4V Fabricated via Laser Directed Energy Deposition

Accurate representation of fatigue -crack -growth -rate behavior is crucial for predicting the fatigue life of additively manufactured materials in structural applications. In this study, fatigue -crack -growth and fatigue -life behavior of Ti-6Al-4V specimens fabricated via laser directed energy deposition (DED-L) were investigated and compared to their conventionally manufactured counterparts. Compression precracking constant -amplitude and ASTM load -reduction methods were used to generate large -crack growth rate data in the near -threshold (low -rate) regime on standard compact tension (C(T)) specimens. In addition, single -edgenotch -bend (SEN(B)) specimens were used to generate fatigue and small -crack -growth -rate data. Uniaxial fatigue tests were also conducted on flat, KT= T = 1, dogbone specimens. A plasticity -induced crack closure model, fatigue structural analysis (FASTRAN), was used to predict the fatigue life of the notched and unnotched specimens. The obtained results were also compared to the fatigue life and crack growth behavior of wrought Ti-6Al-4V. The experimental results indicated that crack growth in the SEN(B) specimens was faster than that in the C(T) specimens at higher rates, but comparable in the low -rate near -threshold regime. Furthermore, the fatigue life of DED-L Ti-6Al-4V specimens was successfully predicted using large -crack growth data.