Consideration of anisotropy and contact of cracks edge at stress calculations of rolling bearings

Investigation of influence of anisotropy on stress-deformed state of base (roller bearings track) considering the appearance of cracks with contacting edges in it is done in the work. The boundary integral equation method is used to determine the stresses. Solution of the Integral equation is done numerically by the mechanical quadrature method. At the task solution it is considered that cracks can be located in the compressive stresses areas, wherefore the cracks edges can contact. The unknown contact stresses on the cracks edges and contact area were determined correspondingly from the set quadratic programming problem. The stresses under the bearings were determined according to the Hertz formula. On the ground of the carried out investigations the following conclusions can be done: mechanical anisotropy of bearings at the track edge allows increasing resistance to brittle crack initiation or decreasing growth rate of fatigue cracks. At that, it is necessary to choose such thermo-mechanical methods of processing at which the module of elasticity in circular direction will be larger than in radial direction (perpendicular to the edge); additional compressive stresses decrease the stress intensity factor (SIF) and tension stresses increase. In this regard in the track neighborhood it is reasonable to do thermal processing to create residual compressive stresses in circular direction. One of the ways to create mechanical anisotropy and compression stresses is insertion of the previously heated thin-walled anisotropic cylinders; the calculated maximum values of the stress intensity factor (SIF) give the possibility to calculate the growth rate of fatigue cracks for different lengths and crack angular inclinations. At that, in the early stages the calculations process is simplified, because here there is the crack edges contact and hence K I =0. Under such conditions a crack will grow along the strait line where it is located. At long lengths of cracks when the crack edges contact is absent, these SIFs allow calculating critical values of crack lengths. Analogical results are obtained for other values of the relations of elasticity modules w, friction factors k, values of parameter m, characterizing the level of additional stresses. These results (which are not provided here) confirm the stated above conclusions on influence of these parameters on the SIF values.