Nucleation and growth of macrofluctuations of plastic strain with discontinuous yield and luders deformation: Results of high-speed video filming

Krishtal, M. M.; Khrustalev, A. K.; Волков, А. В.; Borodin, S. A.

doi:10.1134/s1028335809050024

Cited by 17 publications

(13 citation statements)

References 2 publications

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“…The time dependences of geometric parameters of the incomplete band demonstrate typical nonlinear dynamics with a sharp acceleration at the final growth stage. It should be recalled that due to a lower stress level in the region of the specimen head, the growth rate of incomplete arcuate bands is less than the band growth rate in the central region of the gauge part, where the band grows in the direction of maximum tangential stresses [23][24][25][26]30]. It can be seen that the instant of the band exit to the opposite side surface corresponds to peaks in ( ) АЕ t  , t  and S  .…”

Section: B Acoustic Signals Generated During Formation Of Deformatiomentioning

confidence: 98%

“…The last decade exhibited an important progress in this sense due to improvements of the time resolution of visualization of the surface of a deforming sample. Application of various optical techniques with an acquisition rate of 1 000 to 5 000 fps made it possible to reveal nucleation of an embryo of a PLC band on one side of the specimen and its growth in the direction of the maximum tangential stresses, about 60° to the tensile axis [23][24][25]. To complete the picture, it should be added that quasi-simultaneous strain localization across the specimen was also observed [25,26].…”

Section: Introductionmentioning

confidence: 99%

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Millisecond dynamics of deformation bands during discontinuous creep in an AlMg polycrystal

et al. 2020

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Formation of bands of macroscopic strain localization during staircase creep in an AlMg polycrystal is studied by the acoustic emission (AE) technique and high-speed video-recording with an image acquisition rate up to 50 000 frames per second. The simultaneous measurements by two methods allow to distinguish different types of embryo deformation bands and concomitant AE signals and establish correlations between the band evolution and the acoustic response. It is found that the fastest stages of band formation, associated with its emergence to the surface and subsequent accelerated expansion, generate complex AE bursts in the frequency band ~0.05-1 MHz. The correlations hidden in the complex structure of an individual acoustic burst are investigated by methods of statistical and fractal analysis. On the other hand, relationships between average parameters of various physical responses to discontinuous creep are assessed. Particularly, a close correspondence is found between the envelope of the acoustic burst and the rate of stress change during formation of a single deformation band. Evolution of dynamical behavior of embryo bands with increasing creep stress is discussed. Notably, a qualitative change in the AE waveform observed on approaching the ultimate stress is considered from the viewpoint of anticipation of the oncoming fracture.

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Section: B Acoustic Signals Generated During Formation Of Deformatiomentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Millisecond dynamics of deformation bands during discontinuous creep in an AlMg polycrystal

et al. 2020

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“…However, Chihab et al [23] have not verified their hypotheses due to the lack of direct strain measurements in their experiments. The results of high-speed filming, which suggest a possibility of the mixed scenario of the PLC band nucleation, were presented later [8][9][10][11]38,41].…”

Section: Effect Of Strain Rate On the Mechanism Of Nucleation And Subsequent Development Of The Plc Bandmentioning

confidence: 87%

On the mechanisms of nucleation and subsequent development of the PLC bands in an AlMg alloy

Yuzbekova

Mogucheva

Borisova

et al. 2021

Journal of Alloys and Compounds

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The nucleation and subsequent development of the Portevin-Le Chatelier bands during tensile deformation in a binary AlMg alloy was investigated by the digital image correlation technique. The following states of the material were employed for the current investigation: coarse-grained (CG), fine-grained (FG) after equal channel angular pressing (ECAP), severely strained (SS) after ECAP followed by cold rolling. Special attention was paid to the nucleation of an embryo band by maximizing the contrast of the deformation images. Particular spatiotemporal patterns of the alloy in three different conditions, testifying to the initiation of an embryo band having a wedge shape on the lateral surface of the specimen, were obtained at high and intermediate strain rates. The evaluation of the serration amplitude and the band velocity showed that the dependence of these values on strain consists of two stages (the linear growth-up/drop stage and the steady-state stage) for CG materials and only one stage (the linear growth-up/drop stage) for FG materials. The nucleation of deformation bands always occurs according to a mixed mechanism, in which the thickening of the embryo slows down with a decrease in the strain rate.

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“…The plane parallel glass plate is necessary to provide acoustic contact and electrical insulation of the acoustic sensor from the specimen with current. The choice of the low fre quency sensor operating in the range of 1 Hz-20 kHz was caused by the characteristic times in the evolution of PLC deformation bands, known from the literature: the time of the most rapid initial phase of the band development, 0.2-1.0 ms [16][17][18], and the band propagation time ~0.01-0.1 s [19][20][21]. The AE signal ϕ AE (t) and the specimen current I(t) were recorded using an analog to digital converter and a computer with a data recording frequency to 20 kHz.…”

Section: Investigation Of the Effect Of Electric Current On Serrated mentioning

confidence: 99%

Investigation of the effect of electric current on serrated deformation and acoustic emission in the aluminum-magnesium alloy 5056

et al. 2015

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The effect of direct electric current on the serrated deformation of the aluminum-magnesium alloy 5056 has been studied using the acoustic emission method and high speed video filming of propagating deformation bands. The phenomenon of the electric current induced suppression of low frequency acoustic emission signals has been revealed in the range of 1 Hz-2 kHz, which is connected with the development of Portevin-Le Chatelier deformation bands. The characteristic times of damping and growth of plastic insta bilities and acoustic signals caused by them after current turn on and turn off, respectively, have been esti mated.

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Nucleation and growth of macrofluctuations of plastic strain with discontinuous yield and luders deformation: Results of high-speed video filming

Cited by 17 publications

References 2 publications

Millisecond dynamics of deformation bands during discontinuous creep in an AlMg polycrystal

Millisecond dynamics of deformation bands during discontinuous creep in an AlMg polycrystal

On the mechanisms of nucleation and subsequent development of the PLC bands in an AlMg alloy

Investigation of the effect of electric current on serrated deformation and acoustic emission in the aluminum-magnesium alloy 5056

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