mining conditions: yH -25 MPa; ~ = 0.8; K -5.77 MPa; Ko -0.i K; P " ~o = 30~ A --0.5; A~ -0; P -0; 7, = 13.5~10-s; Yo " 30-10-'; M = 0.545.10m; Ro -2 m. Values of residual strength and post-llmit condition radii are according to calculation ro = 2.38 Ro; r n = 1.95 Ro respectively.The equation for the post-llm~t condition region around the working is written in the form r n -(2.38 + 0.ii cos 28)Ro. The size of this zone in the side of the working reaches of value of 2.49 Ro, and in the roof it reaches -2.27Ro.For comparison we consider the case of absence of residual strength and post-limlt condition zones around ~he working.Then only a plastic strain region having the shape of an ellipse whose semiaxes [3] for the given mining conditions u -1.42 Ro and b -1.02 Ro forms around the working.

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[4][5][6]. Also, there is a lack o f experimental data and theoretical generalization on crack propagation for a trapezoidal load cycle w ith various hold periods under m aximum load [7,8]. The m ajority of researchers in this case restrict them selves to the use o f the linear dam age sum m ation hypothesis based on the independent dam aging effect o f fatigue and creep [2,9]. Som etim es, they determ ine the m aterial susceptibility to a certain m ode o f fracture (fatigue or tim e-dependent) and, on this basis, choose the fracture m echanics param eters to describe experim ental crack grow th rate data [10,11]. It is notew orthy that such approaches do not always yield satisfactory results and require further experim ental and physical substantiation.E arlier [12,13], on the basis o f the experim ental data obtained and calculations perform ed, it was show n that the m ost com m only used approaches give no w ay o f predicting the crack grow th kinetics in the alloys under study to sufficient accuracy. In this paper, w e w ill discuss the m ethods proposed for the solution o f the above problem .R esea rch T ask S ta tem en t. H igh-tem perature nickel-based alloys EP742 and EP962 for aircraft applications w ere used as m odel m aterials. Their m echanical properties and other characteristics as w ell as the experim ental procedure w ere detailed earlier in [12,14]. The m aterials under study are used to m anufacture long-life aircraft gas-turbine engine (A G TE) disks. The service conditions (flight cycle) involve operation o f the m aterial under cyclic loading w ith long hold periods at m axim um load in a cycle. The solution o f this problem m akes it

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