Effect of single plastic prestraining on crack resistance. 1. The rate of fatigue crack growth in heat-resistant steel

1.	Prestraining has an ambiguous effects on the FCG rate in steels 15Kh1MFA (I) and 15Kh2MFA (II). With increase in prestraining there is a decrease in the FCG rate in the threshold region of the KDFF of steel 15Kh2MFA (I) and also in the middle section for steel 15Kh2MFA (II). However, in the threshold region of the KDFF of steel 15Kh2MFA (II) FCG increases.
2.	An increase in the level of prestraining for steels 15Kh2MFA (I) and 15Kh2MFA (II) leads to an increase of the SIF during opening of the crack. Due to this, the KDFF of these steels when plotted in the coordinates log V–log Keff is invariant relative to the degree of prestraining.

Institute of Strength Problems, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Problemy Prochnosti, No. 12, pp. 9–14, December, 1988.