The stress-strain state of a rectangular plate with a central circular hole and a disc with an edge notch is analyzed both for elastic and elastic-plastic behaviour when cracks emanate from the contours of these concentrators. Stress intensity factors are determined as well as the value of the inelastic deformation at stress concentration zones. The parameters describing the process of crack nucleation are established. The computational results are compared with experimental data when evaluating the period of macrocrack nucleation. NOMENCLATURE a,b = plate length and width d* = the material constant E = Young's modulus G = elastic shear modulus h = thickness of a plate or a disc K, = stress intensity factor (SIF) for the opening mode crack K,$ = SIF for the opening mode of a crack emanating from the concentrator L, = concentrator contour (K = 0); plate or disc contour ( K = I); crack contour ( K = 2.3) I = crack length 1, = length of equivalent crack f , = length of plastic zone 1, = length of a crack emanating from the concentrator N, = number of loading cycles before crack nucleation N ( t K ) , T(tK) = stress components on the L, contour R = disc radius or hole radius in the plate t , = current coordinate of the contour L, u(t,), o(t,) = displacement vector components S , , 86, = notch tip opening displacement (NTOD) and NTOD range (in point A) p = Poisson ratio p = notch radius in the disc uys = yield stress of the material u : , Au:= normal stress and normal stress range at the characteristic distance d* from the concentrator tip uyvmax = maximum stress at the concentrator tip uy(x) = normal stress component along the concentrator axis O(z), Y ( 2 ) = Kolosov-Muskhelishvili complex stress function

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