An Experimental Study of Fatigue Crack Propagation of 16MnR Pressure Vessel Steel in Mode-I Constant Amplitude Loading

An experimental investigation was performed on fatigue crack growth behavior of a 16MnR pressure vessel steel. Standard compact tension (CT) specimens with three specimen thicknesses and notch sizes were subjected to Mode I constant amplitude loading with several stress ratios and loading amplitudes. The results revealed that the stress ratio had an insignificant influence on the fatigue crack growth of the material. The stable fatigue crack growth rate (FCGR) was accelerated as specimen thickness increased. The fatigue crack was extended in terms of the curve crack shape. The crack front at the surface was retarded compared to that at the interior along thickness direction, and the crack front at the mid-thickness plane reached the maximum value of the crack length. The similar curve crack shape was obtained in the stable crack growth stage. The maximum difference of the crack front along thickness direction was increased with the increasing of the specimen thickness. The early crack growth from the notch was effected by the size of the notch, the stress ratio and loading amplitude.