Method of investigation into cracks growth kinetics during cyclic elastic-plastic deformation using J-integral

When studying the kinetics of crack growing two ways of cyclic J-integral determination hase been used. The compact samples t=25 mm with the initial fatigue crack 3 mm long made of the 15Kh2NMFA steel (σsub(u)=720 MPa; σsub(0.k)=610 MPa; delta=22.3%; psi=75.7%; asub(n)2.04x10sup(6) J/m2; E=2.11x105 MPa) have been tested. It is necessary to continue the search of the method of cyclic J-integral determination during soft loading, which takes into account both the strain accumulated and the strain for a single cycle of loading. It will permit to control the propagation of fatigue cracks in a wide range of levels of nominal stresses (at σsub(n)sup(c)>2σsub(s) included)