Self-arresting cracks at notches in ductile cast iron

In this research, an experimental study of the notch effect in ductile cast iron EN-GJS-400-18-LT has been performed. Double-edge notched specimens with different notch root radii were tested under fully reversed axial loading. The notch root was monitored with a travelling microscope. By judicious selection of the load amplitudes, self-arresting cracks were observed in most of the specimens.Two different models were used to analyse the growth of a short crack from the notch root. One model was a generalisation of El Haddad’s equation to short-crack growth in an inhomogeneous stress field. The other was a slightly modified version of a model by Härkegård based on El Haddad’s asymptotic solutions for shallow and deep cracks.Self-arresting cracks in the double-edge notched specimens were predicted in reasonable agreement with experimental observations. The two short-crack-growth models were also applied to literature fatigue data for notched rotating bend specimens of a similar type of ductile cast iron. Härkegård’s model predicted the notched fatigue limit in good agreement with reported observations.

► The following note has been added to the text: dimensions are in mm. Please check Fig. 2 and Fig. 8. ► The acronym SAC has been added to the nomenclature list. ► 52.2 MPa has been changed by 52 MPa in the text.