Effect of Prestrain on Fatigue Crack Growth in Low-carbon Steel

The current procedures of fatigue design of marine pipeline components allow for extending service life by considering a certain portion of the crack growth well before it turns into the instable phase. In structural components of transport systems material may undergo plastic pre-strain during the construction. The effect of pre-strain on the crack growth may be different depending on the material properties. 

Fatigue crack propagation was examined in testing symmetrically notched specimens machined from pre-strained steel plate coupons. Non-simultaneous crack initiation and propagation at the notches was reduced to symmetrical scheme by a simple coordinate transformation procedure. 

It was found that tensile pre-strain up to 0.01 did not substantially change the crack growth rate related to the stress intensity factor scale. Further increase of plastic pre-strain of material up to 0.15 caused almost two-times slowing down the crack growth rate compared to that of virgin material.