FATIGUE FRACTURE OF THIN PLATES WITH STRESS CONCENTRATORS UNDER UNIAXIAL ASYMMETRICAL LOADING

Abstract

The problem of fatigue crack growth from a stress concentrator in thin finite plates under high-cyclic uniaxial asymmetrical loading is considered. As the stress concentrators are considered an elliptical hole, circular hole and central crack. Purpose. Testing the model of fatigue fracture based on the joint consideration of boundary-value problem of fracture mechanics and damage kinetics problem of the continuum damage theory on the solution of the problem of the growth of a crack in a thin finite plate with stress concentrators under uniaxial asymmetrical high-cycle loading. Methodology/ approach. It is assumed that fatigue damage accumulation is the cause of crack motion. Two-stage process damage accumulation involves the incubation stage and crack propagation stage. This process is described by scalar parameter of damage ω∈[0;1]. The condition of the damage parameter equality to 1 is taken as the criterion of the fatigue fracture front initiation and movement. It is assumed that main part of body is deformed linear-elastically while all non-linear effects are concentrated in plastic zones at the crack tip. According to presented model the fatigue crack increases step by step on the length of cyclic plastic zone. The lengths of plastic zones near crack tip are defined on base modified Dugdale model. Findings The numerical analytical solution is obtained on basis of fatigue crack growth two-stage theoretical model and equivalent stresses criterion reduced asymmetrical loading to equivalent symmetrical cyclic loading on rupture time. The calculation results using model agree well with those obtained by experiment.