2 Íàó÷íî-èññëåäîâàòåëüñêèé èíñòèòóò ìåõàíèêè Íàöèîíàëüíîãî èññëåäîâàòåëüñêîãî Íèaeåãîðîäñêîãî ãîñóäàðñòâåííîãî óíèâåðñèòåòà èì. Í.È. Ëîáà÷åâñêîãî, Íèaeíèé Íîâãîðîä, Ðîññèéñêàÿ Ôåäåðàöèÿ 3 Íèaeåãîðîäñêèé ãîñóäàðñòâåííûé òåõíè÷åñêèé óíèâåðñèòåò èì. Ð.Å. Àëåêñååâà, Íèaeíèé Íîâãîðîä, Ðîññèéñêàÿ Ôåäåðàöèÿ pmptmvgavt@yandex.ru Ïîñòóïèëà â ðåäàêöèþ 20.03.2017Îáñóaeäàåòñÿ ïðîáëåìà îöåíêè ïðî÷íîñòè è ðåñóðñà îòâåòñòâåííûõ èíaeåíåðíûõ îáúåêòîâ, ýêñïëóàòàöèîííûå ñâîéñòâà êîòîðûõ õàðàêòåðèçóþòñÿ ìíîãîïàðàìåòðè÷åñêèìè íåñòàöèîíàðíûìè òåðìîìåõàíè÷åñêèìè âîçäåéñòâèÿìè. Ðàññìîòðåíû íåêîòîðûå äåãðàäàöèîííûå ìåõàíèçìû êîíñòðóêöèîííûõ ìàòåðèàëîâ (ìåòàëëîâ è èõ ñïëàâîâ), õàðàêòåðíûå äëÿ äàííûõ îáúåêòîâ. Ñôîðìóëèðîâàíû îñíîâíûå òðåáîâàíèÿ ê ìàòåìàòè÷åñêèì ìîäåëÿì íàêîïëåíèÿ óñòàëîñòíûõ ïîâðåaeäåíèé. Íà áàçå ðàçâèòîãî âàðèàíòà îïðåäåëÿþùèõ ñîîòíîøåíèé ìåõàíèêè ïîâðåaeäåííîé ñðåäû ïðîâåäåí ÷èñëåííûé àíàëèç âëèÿíèÿ óãëà íàêëîíà îõëàaeäàþùèõ êàíàëîâ íà òåðìîöèêëè÷åñêóþ äîëãîâå÷íîñòü ìîäåëåé aeàðîâûõ òðóá êàìåð ñãîðàíèÿ ãàçîòóðáèííûõ äâèãàòåëåé. Îñîáîå âíèìàíèå óäåëåíî âîïðîñàì èññëåäîâàíèÿ ïðîöåññîâ ñëîaeíîãî òåðìîöèêëè÷åñêîãî äåôîðìèðîâàíèÿ è íàêîïëåíèÿ óñòàëîñòíûõ ïîâðåaeäåíèé, ñîïðîâîaeäàþùèõñÿ âðàùåíèåì ãëàâíûõ ïëîùàäîê òåíçîðîâ íàïðÿaeåíèé, ïîëíûõ è ïëàñ-òè÷åñêèõ äåôîðìàöèé è ïðîöåññàì íàêîïëåíèÿ óñòàëîñòíûõ ïîâðåaeäåíèé. Ñîïîñòàâëåíèå ðåçóëüòàòîâ ïðîâåäåííûõ ðàñ÷åòîâ ñ ýêñïåðèìåíòàëüíûìè äàííûìè ïîêàçàëî, ÷òî ðàçâèòàÿ ìîäåëü ìåõàíèêè ïîâðåaeäåííîé ñðåäû êà÷åñòâåííî è ñ íåîáõîäèìîé äëÿ èíaeåíåðíûõ ðàñ÷åòîâ òî÷íîñòüþ êîëè÷åñòâåííî îïèñûâàåò îïûòíûå äàííûå è ìîaeåò ýôôåêòèâíî ïðèìåíÿòüñÿ äëÿ îöåíêè òåðìî-öèêëè÷åñêîé äîëãîâå÷íîñòè ìàòåðèàëîâ è êîíñòðóêöèé ïðè ìíîãîîñíûõ íåïðîïîðöèîíàëüíûõ ïóòÿõ òåðìîöèêëè÷åñêîãî íàãðóaeåíèÿ.Êëþ÷åâûå ñëîâà: òåðìîöèêëè÷åñêàÿ äîëãîâå÷íîñòü, ìåõàíèêà ïîâðåaeäåííîé ñðåäû, ñëîaeíîå äåôîðìèðîâàíèå, ìîäåëüíûå îáðàçöû aeàðîâûõ òðóá, îõëàaeäàþùèé êàíàë, óãîë íàêëîíà, ìàêðîñêîïè÷åñêàÿ òðåùèíà, ïðî÷íîñòü, ðàçðóøåíèå.ÏÐÎÁËÅÌÛ ÏÐÎ×ÍÎÑÒÈ È ÏËÀÑÒÈ×ÍÎÑÒÈ, ò. 79, ¹ 2, 2017 ã.

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.

The problem of evaluating the strength and service life of operating properties of critical engineering facilities which are characterized by multivariable non-stationary thermomechanical effects, leading to degradation of initial strength properties of structural materials (metals and alloys) on the mechanisms of fatigue and creep is considered. A mathematical model describing the processes of unsteady creep of metals under complex stress state is constructed. A theoretical-experimental method of determining the material parameters and scalar functions defining transient creep ratios is developed. The results of numerical modeling of the creep process 304 at block thermocyclic complex modes of deformation are presented. The numerical results are compared with those of full-scale experiments. Particular attention is paid to issues of simulation of creep for complex deformation processes, accompanied by the rotation of the main sites of stress and strain tensors and creep strains.

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