The fatigue crack growth rate and crack opening displacement in 18G2A-steel under tension

In the paper, the results of crack tip opening displacement (CTOD) and crack opening displacement (COD) in place of crack initiation as well as the fatigue crack growth rate in higher strength steel are presented. The investigation were carried out on flat specimens with central notch under constant amplitude tensile fatigue loading at stress ratio R = 0.2 and different value of the stress σmax. The test results showed that with growth of crack length l grew values of the CTOD and COD. In the work, it was proposed calculation of the CTOD value on basis various dependence of plastic zone radius on crack tip.

► I studied the crack opening during fatigue cracking in tensile steel samples.
► The fatigue crack growth rate is function of crack opening displacement.
► This function had for low stress linear character and non-linear for high.
► I proposed formulas to calculation of the crack tip opening displacement.