Koval V. Low-cyclic fatigue of structural elements taking into account damage

The dissertation is devoted to the development of a method for estimating the durability of structural elements, taking into account the kinetics of damage accumulation for low-cycle loading conditions. Damage parameter in work was defined by change of electrical resistivity of a sample (for case of static loading) and by means of change of the module of elasticity analysis (for a case of cyclic loading). Analytical dependences for damage parameter determination at the level of a yield stress and rupture stress are received. The method of approximate calculation of hardening coefficient for the effective deformation diagram is offered. Effective characteristics of metal materials D16T, VT22, 15HSND, 18H2N4VA, 12H18N10T, 07H16N6 are defined. Neuber-Makhutov's dependences for determination of effective concentration coefficients of stress and strain are modified, comparison for the modified and basic approach is carried out. For a case of low-cyclic loading (symmetric stress-controlled cycle) cyclic parameters for materials D16T, VT22, 15HSND, 18H2N4VA have been received. Kinetic curves of damage accumulation are received. On the basis of energy approach the assessment method of structural elements durability is offered. The calculated rupture cycles values received by this method have been compared with experimental and values according to a standard Makhutov’s method.