Macroscopic Correlation of Deformation Events in Low-Stability State of the Crystal Lattice and Spectral Density of Acoustic Emission Signals

Макаров, С. В.; Плотников, В. А.; Потекаев, А. И.

doi:10.1007/s11182-014-0329-0

Cited by 12 publications

(4 citation statements)

References 16 publications

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“…Колебательная энергия акустической эмиссии (как отмечено выше) должна накапливаться в объеме деформируемого образца. Единственным процессом, который может обеспечить накопление колебательной энергии, является процесс формирования стоячих акустических волн на естественных резонаторах в системе образец-волновод [27]. Разумеется, бегущая волна (точнее волновой пакет) также характеризуется некоторой колебательной энергией, однако эта энергия быстро затухает при распространении волнового пакета.…”

Section: анализ экспериментальных результатовunclassified

Accumulation of deformation and acoustic emission in aluminum-magnesium alloy AMg6 in the conditions of deformation of the structural transition

Макаров

Плотников

2020

Lett. Mater.

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In the course of thermomechanical loading of an aluminium-magnesium alloy under soft loading conditions, a monotonicstepwise or quasi-stepwise character of deformation accumulation has been observed. Monotonous accumulation of deformation is followed by a monotonous growth of the root-mean-square voltage of acoustic emission, as well as deformation jumps are followed by high-amplitude discrete signals of acoustic emission. The accumulation of deformation in an aluminum-magnesium alloy in a non-isothermic cycle is characterized by the two-stage process: low-temperature monotonous, with a low rate of deformation accumulation, and high-temperature stepwise or quasi-stepwise with a high-rate of deformation accumulation. The temperature transition point from the low-temperature area to the hightemperature area has the value of approximately 570°C and determines a low-to-high-rate transition of deformation accumulation. This kind of transition from the low-temperature area of deformation accumulation to the high-temperature one is characterized by a change in the mechanism of deformation accumulation and represents a deformation structural transition. Thus, the deformation structural transition is the transition from deformation accumulation that is controlled by thermally-activated dislocations climb to deformation accumulation that is controlled by grain boundary processes of perfect (lattice) dislocations generation at triple boundary junctions and occurs when mechanical stress, temperature and acoustic emission energy achieve certain critical values. While the mechanical stress grows, the transition temperature goes down and the acoustic emission oscillation energy rises thus showing that a certain balance of critical parameters is kept. The deformation structural transition is the result of the joint action of thermal fluctuations, static shifts of stress field and dynamic shifts of standing acoustic waves formed by primary signals of the acoustic emission at natural resonators of the sample volume under deformation.

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Section: анализ экспериментальных результатовunclassified

Accumulation of deformation and acoustic emission in aluminum-magnesium alloy AMg6 in the conditions of deformation of the structural transition

Макаров

Плотников

2020

Lett. Mater.

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“…В то же время в наших работах показано [25, 37 -38], что амплитуда акустического сигнала (точнее квадрат амплитуды) может служить мерой корреляции элементарных деформационных актов в связи с тем, что выход на поверхность системы дислокационных сегментов одной системы скольжения генерирует систему когерентных акустических волн, интерференция которых формирует единичный акустический сигнал аномально большой амплитуды. Кроме того установлено [38], что в деформируемом объеме формируется система стоячих акустических низкочастотных волн, в которых запасается заметная по величине колебательная энергия акустической эмиссии. В этой связи можно предполагать, что сигналы акустической эмиссии, трансформированные в низкочастотные акустические стоячие волны, осуществляют активацию и корреляцию элементарных деформационных актов, то есть выполняют роль фактора самоорганизации в макроскопическом объеме в слабоустойчивой кристаллической среде.…”

Section: пластическая деформация и акустическая эмиссияunclassified

Weakly Stable State of the Crystal Lattice of Metals and Alloys

Макаров¹,

Плотников²,

Dem’yanov³

et al. 2019

LOM

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The state of the crystalline medium under the conditions of thermal fluctuations and mechanical stresses called weakly stable is determined by the displacement of atoms at a relative distance of 0.15-0.20 from the equilibrium positions. Such a displacement of the atoms follows the Lindemann criteria of the crystals melting, and the state of atomic ensemble can be described as delocalized one. The state of delocalization means the transition of the atom through the maximum of interaction force and is characterized by a strong anharmonic component of oscillations and softening of elastic modules. It is the state of delocalization of the atomic ensemble that is the weakly stable state of the crystal lattice. Weakly stable state of metal materials is manifested in a wide range of phenomena. These include abnormal reduction of elastic modules in thermoelastic martensitic transformations, second-order structural-phase transitions with the formation of long-period structures, abrupt plastic deformation, most clearly manifested in aluminium and its alloys, increasing the rate of deformation during creep in the ultrasonic field under static load. This paper presents the results of the analysis of the weakly stable state of the crystalline medium, especially in plastic deformation, that is, in the processes caused by the displacement of atoms from the equilibrium position. In these processes, the weakly stable state of the system can occur in the field of mechanical stresses and thermal fluctuations when the acoustic field of standing waves is applied, formed by primary acoustic emission signals, the combined action of which allows to overcome the potential barrier. In this state, the oscillatory displacement of the acoustic standing wave acts as a factor of self-organization, that is, it may be sufficient to activate the correlated dislocation slip, in fact, the athermal above-barrier slip in the weakly stable state of the crystal lattice.

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“…By introducing the concept of the weak-stable lattice state, we assume a crystalline state of the medium as active medium [5,10]. Thus, when plastic flow of the crystal lattice is an oscillating system excited in the standing wave mode, the activation of an elementary deformation event results from both thermal fluctuations [9] and the influence of acoustic oscillations [11].…”

Section: Acoustic Wave Factor Of Self-organization Of Elementary Defomentioning

confidence: 99%

Wave correlation of elementary deformation events during plastic deformation of metals

Макаров¹,

Плотников²,

Lysikov³

2016

AIP Conference Proceedings

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The investigations show that the spectral density of acoustic emission signals for monotonic accumulation of deformation is represented by three spectral lines located below 60 kHz and some area of about 90 kHz, while the spectral density of signals for the stepwise pattern is characterized by a significant complication of the spectrum, the emergence of new spectral lines. Acoustic emission reflects self-organization processes characterized by poor stability and elementary processes in the atomic subsystem under external influence. ACTIVATION ENERGY AND THE LOW-STABILITY STATE OF THE CRYSTAL LATTICE The special state of the crystal lattice, which is called the low-stability state and associated with the state of the atomic ensemble in the field of mechanical stresses and thermal fluctuations, is a combined effect, which allows

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Macroscopic Correlation of Deformation Events in Low-Stability State of the Crystal Lattice and Spectral Density of Acoustic Emission Signals

Cited by 12 publications

References 16 publications

Accumulation of deformation and acoustic emission in aluminum-magnesium alloy AMg6 in the conditions of deformation of the structural transition

Accumulation of deformation and acoustic emission in aluminum-magnesium alloy AMg6 in the conditions of deformation of the structural transition

Weakly Stable State of the Crystal Lattice of Metals and Alloys

Wave correlation of elementary deformation events during plastic deformation of metals

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