Modeling Plastic Deformation of Polychrystalline Structural Alloys Under Block-Type Nonsymmetrical Regimes of Soft Low-Cycle Loading

Abstract

Processes of plastic deformation of polycrystalline structural alloys under block-type nonstationary regimes of soft low-cycle loading are considered. Modified Korotkikh's thermal-plasticity model pertaining to the class of yield theories with translation-isotropic hardening is used as defining relations of plasticity. The modification of Korotkikh's model consists in using a different formulation of evolutionary equations for the displacement of the yield surface center (the micro-stress tensor), used for block-type nonstationary regimes of low-cycle loading for describing effects of setting under a hard loading regime (controlled strains) and ratcheting under a soft loading regime (controlled stresses) of the plastic hysteresis loop. Determining the material parameters and scalar functions of the plastic deformation model, assessing its adequacy and scope of application was done based on the experimental studies of the deformation process of laboratory specimens made of stainless steels of the austenite (SS316L, SS304) and ferrite (20MnMoNi5-5) classes in the conditions of uniaxial and multiaxial, proportional and non-proportional regimes of soft block-type cyclic loading. Comparison of the numerical results with the experimental data indicates that the developed plasticity model qualitatively and quantitatively, accurately enough for engineering purposes, describes the main effects of plastic deformation (displacements of the plastic hysteresis loops and decreasing strain amplitudes) under block-type nonstationary nonsymmetrical regimes of soft low-cycle loading.

Evaluation of Resource Characteristics of Polycrystalline Structural Alloys During Degradation by Joint Mechanisms of Fatigue and Creep of the Material

“…Для описания сложных циклических режимов деформирования в пространстве деформаций вводится поверхность циклической «памяти» [23]:…”

“…Для учета эффектов упрочнения и разупрочнения, проявляющихся вследствие синергетического действия различных физических механизмов в поликристаллических конструкционных сплавах, таких как мартенситные фазовые превращения, изменение дислокационной плотности, изменение текстуры, выделение карбидов и др. [23], скорость изменения радиуса поверхности пластического нагружения принимается в виде суммы скоростей изменения радиуса поверхности пластического нагружения с учетом вклада каждого физического механизма:…”

“…На рис. 2 приведены законы нагружения, реализуемые в испытаниях.Физико-механические характеристики стали 316[7] и материальные параметры модели МПС при температуре 650 °С[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] приведены в таблицах 1-4.…”

Modeling of the Fatigue Durability of Structural Alloys Under Two-Frequency Loading

“…Óðàâíåíèÿ íàêîïëåíèÿ ïîâðåaeäåíèé áàçèðóþòñÿ íà ñâÿçè âåëè÷èíû ïîâðåaeäåííîñòè ñ ìàêðîñêîïè÷åñêèìè ïàðàìåòðàìè, êîòîðûå ìîãóò áûòü ýêñïåðèìåíòàëüíî îïðåäåëåíû.  íàñòîÿùåå âðåìÿ íàèáîëåå ôèçè÷åñêè îáîñíîâàííûì è àïðîáèðîâàííûì ÿâëÿåòñÿ ýíåðãåòè÷åñêèé ïîäõîä ïðè îïðåäåëåíèè ðåñóðñíûõ õàðàêòåðèñòèê ïîëèêðèñòàëëè÷åñêèõ òåë [19][20][21][22][23][24]. Â.Â.…”