Characterising and representing small crack growth in an additive manufactured titanium alloy

•The modified Hartman-Schijve equation is used for predicting small crack growth rate.•Material constants in the equation can be fitted by long crack test data alone.•Small crack is modelled by setting the stress intensity factor threshold to a small value.•Small crack growth rate in 3D printed titanium was measured for model validation.•Predicted small crack growth life in another specimen geometry agreed well with test.