RU2704575C1 - Method of simulating transient processes of accumulation of damages in a diagnosed object and a device of a bifurcation model - Google Patents

Abstract

FIELD: simulation of processes.

SUBSTANCE: use to simulate unstable transient processes of damage accumulation in a diagnosed object with registration of points of structural and system bifurcation. Summary of invention consists in the fact that to record dynamics of transient processes during formation of bulk cone and change of their trend at points of structural and system bifurcation, due to accumulation of critical mass of granulate at apex of cone, its settling under action of own weight and subsequent avalanche caving, it is proposed to create conditions of conic surface collapse of granulate at low thickness of formed layer δ=10–20 mm, and time strobing of transient processes is carried out by synchronous recording of video images and arrays of local pulses, recorded using acoustic emission monitoring, every second separating AE signals into clusters of lower, middle and upper energy level, by counting frequency of their registration ω_i=L,M,U and percentage content W_i=L,M,U, fixing the dynamics of these parameters on the graphs and changing the trend of transient processes at the points of structural and system bifurcation, thus confirming the moments of their recording with frames of high-speed video filming.

EFFECT: possibility of simulating the dynamics of changing trend of accumulation of damages in points of structural and system bifurcation occurring in the diagnosed object.

8 cl, 8 dwg

Description

The invention relates to methods and devices of experimental mechanics and non-destructive testing, using high-speed video synchronized with acoustic emission monitoring, for temporary gating of transients simulating damage accumulation in the diagnosed object, for example, during degradation and fatigue destruction of the structure of a structural material.

The purpose of the claimed object is to simulate unstable transient processes of damage accumulation in the diagnosed object with registration of structural and system bifurcation points by temporarily gating the process of forming a granulate bulk cone using high-speed video synchronized with acoustic emission monitoring.

по стандартной методике [2].The closest technical solution adopted for the prototype is the method and device considered in the publication [1], in which for the registration of unstable transient accumulation of damage and points of systemic and structural bifurcation, modeled during the formation of the bulk cone when the granulate expires from the storage funnel on the horizontal surface of sheet glass, due to the formation of a critical mass of granulate at the top of the cone, its settling under the influence of its own weight and subsequent avalanche th collapse, using a high speed video synchronized with acoustic emission (AE) monitoring, recording activity accumulation radar pulses channels acoustic emission system

according to the standard method [2].

The disadvantage of this technical solution is that the standard method for planar location of AE events in solids, used in experiments under AE monitoring the process of forming a bulk cone, due to the high level of attenuation of acoustic waves with a granulate layer thickness of more than 20 mm, did not allow recording low-energy AE pulses resulting from the accumulation of the critical mass of the granulate at the top of the cone, its settling under the influence of its own weight and the subsequent avalanche like usheniya.

In development of this technical solution for modeling the dynamics of transients and recording structural and systemic bifurcation points that arise as a result of the accumulation of a critical mass of granulate at the top of a cone, its subsidence under its own weight and subsequent avalanche-like collapse, it is proposed to artificially create conditions for granulate collapse using a conical surface when a small thickness of the formed layer δ = 10-20 mm, for which the accumulation of granulate is carried out on the conical surface of the metal eskogo waveguide coated with a damping layer and the gate time transients produced by the synchronous recording of video and arrays of radar pulses every second separating pulses in clusters lower (H), medium (P) and upper (B) energy level, counting the frequency of their registration ω _{i = H, C, B} and the percentage of W _{i = H, C, B} by the formula:

W _i = (N _i / N _Σ ) ⋅100%,

where N _{i = H, C, B} is the number of pulses in the i-th cluster,

N _Σ is the total number of accumulated location pulses, fixing the dynamics of these parameters on the graphs, and the change in the trend of transients at the points of structural and systemic bifurcation, confirming the moments of their registration with high-speed video frames.

The inventive device of the bifurcation model from the prototype [1] differs in that a conical waveguide is installed through a contact lubricant layer on the glass plate of the center of the funnel-accumulator equipped with a metering unit for regulating the flow of granulate, the conical surface of which is covered with a damping layer, the bracket in which the funnel is fixed - the drive is made movable, which allows you to adjust the position of the dispenser relative to the top of the bulk cone of the granulate at a predetermined level of 100-150 mm. As granulate, granules of crushed lead glass with a size of 200-400 microns were used, generating the required level of amplitude of AE pulses at the stages of the formation of the bulk cone of glass granulate in the process of acoustic emission monitoring. For a better location of AE events that occur during the collision of glass granules falling from the funnel-hopper dispenser onto the surface of the formed cone, one of the AE transducers is installed coaxially with the center of the waveguide, and the rest evenly around its periphery. As a waveguide, a solid aluminum cone with an inclination angle of 30-33 ° and a base diameter of 140-150 mm is used, which allows for a small thickness of the glass granulate layer δ = 10-20 mm to create conditions for an avalanche-like collapse of the granulate and registration of AE signals resulting from it. To reduce the expansion of the granules upon impact with the surface of the forming cone, the surface of the waveguide is covered with a damping layer, which is used as a gauze fabric impregnated with glue, and to form a glass granulate layer of the required thickness δ = 10-20 mm on the conical waveguide, the horizontal dimensions of the glass plate on which it is installed conical waveguide should be 2-2.5 times the diameter of its base. When shooting transient processes that occur when a critical mass of granulate accumulates on top of a waveguide cone, settles under its own weight and subsequent avalanche collapse, a high-speed video camera should be located at an angle of 60 ° relative to the plane of the glass plate at a distance of 400-500 mm from the surface of the conical waveguide.

The purpose of this technical solution is to develop a method for modeling damage accumulation in the diagnosed object and a bifurcation model device, which allows registering the dynamics of transients at the stages of granular bulk cone formation and damage accumulation trend changes at structural and system bifurcation points.

Effect: recording on the graphs of acoustic emission monitoring the dynamics of transients simulating the accumulation of damage to the diagnosed object during the formation of the bulk cone of the granulate, and the trend change at the points of structural and system bifurcation, confirmed by synchronous recording of processes on frames of high-speed video. The problem to which this invention is directed is to develop a method for modeling damage accumulation and a bifurcation model device, which allows modeling the dynamics of damage accumulation trend changes at structural and system bifurcation points that occur in the diagnosed object, for example, as a result of degradation and fatigue failure of the structure of the structural material subjected to cyclic loading.

The essence of the proposed method is that for recording the dynamics of transients during the formation of a bulk cone and changing their trend at points of structural and systemic bifurcation, due to the accumulation of the critical mass of granulate at the top of the cone, its settling under the action of its own weight and subsequent avalanche collapse, it is proposed to using a conical surface, artificially create conditions for granulate collapse at a small thickness of the formed layer δ = 10-20 mm, and temporary gating dnyh processes performed with a synchronous recording of video and arrays of radar pulses recorded using acoustic emission monitoring, every second separating AE signals into clusters lower, middle and upper energy level, counting the frequency of their registration ω _{i = H, C, B} and percentages W _{i = H, C, B} , fixing the dynamics of these parameters on the graphs, and the change in the trend of transients at the points of structural and systemic bifurcation, confirming the moments of their registration with high-speed frames video shooting.

The device of the bifurcation model, which allows to implement the proposed method, differs from the prototype [1] in that a cone waveguide is installed through a contact lubricant layer on the glass plate of the center of the funnel-funnel equipped with a dispenser, the conical surface of which is covered with a damping layer, the bracket in which is fixed the granulate storage funnel is made movable, which allows you to adjust the position of the dispenser relative to the top of the granulate bulk cone at a predetermined level of 100-150 mm. As granulate, granules of crushed lead glass (hereinafter referred to as glass granulate) are used with a size of 200-400 μm, generating the required amplitude level of AE pulses at the stages of formation of the bulk cone of glass granulate in the process of acoustic emission monitoring. For a better location of the AE events that occur during the collision of glass granules falling from the funnel-hopper dispenser to the top of the formed cone, one of the AE transducers is installed coaxially with the center of the waveguide, and the rest evenly along its periphery. As a waveguide, a solid aluminum cone with an inclination angle of 30-33 ° and a base diameter of 140-150 mm is used, which allows for the thickness of the glass granulate layer δ = 10-20 mm to create conditions for an avalanche-like collapse of the granulate and registration of AE signals resulting from it. To reduce the expansion of the granules upon impact with the apex of the cone being formed, the waveguide is covered with a damping layer, which is used as a gauze fabric impregnated with glue, and to accumulate a granulate layer of the required thickness δ = 10-20 mm on the conical waveguide, the horizontal dimensions of the glass plate on which the cone is mounted waveguide, 2-2.5 times the diameter of its base. When shooting transient processes that occur when a critical mass of granulate accumulates on top of a waveguide cone, settles under its own weight and subsequent avalanche collapse, a high-speed video camera should be located at an angle of 60 ° relative to the plane of the glass plate at a distance of 400-500 mm from the surface of the conical waveguide.

The claimed method and device model is illustrated by the following graphic materials:

FIG. 1 is a diagram of a bifurcation model;

FIG. 2 is an arrangement of acoustic emission transducers;

FIG. 3 - results of AE monitoring of the formation of the cone of the granulate;

Fig 4 - typical moments of the formation of the bulk cone;

FIG. 5 - typical waveforms and spectra of location pulses;

FIG. 6 - waveforms and pulse spectra of AE upon impact of granules on the top of the cone;

FIG. 7 - waveforms and pulse spectra of AE during subsidence of the cone apex;

FIG. 8 - areas of separation of location pulses into energy clusters.

The device of the bifurcation model, using which the claimed method is implemented, includes a tripod consisting of a flat base (1), a vertical stand (2) and an arm (3) fixed on it, acoustic emission transducers (4) mounted by the back on the base of the tripod (1), a glass plate (5), resting on the transducers (4) through a contact lubricant layer (6), a granulate storage funnel (7), mounted in an arm (3) above the center of the plate (5), communication cables (8) acoustic signal preamps Russia (9), a unit for collecting and processing acoustic emission data (10), a control computer (11), a high-speed video camera (12), and differs from the prototype [1] in that, on a glass plate (5), it is opposite to the center of the storage funnel (7) equipped with a dispenser (13), through the contact lubricant layer (6) a conical waveguide (14) is installed, the conical surface of which is covered with a damping layer (15), the bracket (3) is made movable, vertically moved along the strut (2), and regulating the position of the dispenser (13) relative to the top of the bulk cone of the granulate this level is 100-150 mm.

When implementing the claimed technical solution, the task is realized using a bulk cone of granulate, the formation of which is carried out using a conical surface, artificially creating conditions for the accumulation of critical mass of granulate on top of the cone, its settling under the influence of its own weight and the subsequent avalanche-like collapse of the granulate with a small thickness of the formed layer δ = 10-20 mm, and temporary gating of transients is carried out by synchronous recording of video images and arrays of location pulses recorded using acoustic emission monitoring, every second dividing the AE signals into clusters of lower, middle and upper energy levels, counting the frequency of their detection ω _{i = H, C, B} and the percentage of W _{i = H, C, B} , fixing the dynamics of these parameters on the graphs, and the change in the trend of transients at the points of structural and systemic bifurcation, confirming the moments of their registration with frames of high-speed video.

The technical and economic efficiency of the invention lies in the possibility of recording on the graphs of acoustic emission monitoring the dynamics of transients simulating the accumulation of damage in the diagnosed object during the formation of the bulk cone of the granulate and the change in their trend at the points of structural and systemic bifurcation, confirmed by synchronous recording of processes on high-speed frames filming, which allows you to more accurately predict the residual life of diagnosed objects and reduce the risk of pre-emergency situations.

As an example of a demonstration of the proposed method and device, the modeling of unstable transient processes occurring at the stages of the formation of the bulk cone of glass granulate is considered. The dynamics of these processes and bifurcation points during the experiments were recorded by means of high-speed video recording using the Video Sprint camera and acoustic emission monitoring using the eight-channel multi-parameter A-Line 32D system, for synchronization of which the software developed on the basis of the LabVIEW product was used .

None of FIG. Figure 1 shows a diagram of a model of damage accumulation in a diagnosed object, for example, in the structure of a structural material for recording transient processes and bifurcation points, implemented by temporarily gating the process of forming a bulk cone of glass granulate using high-speed video synchronized with acoustic emission monitoring.

Lead glass granules with a granule size of 200-400 microns were used as bulk material for the experiments. The containers for the glass granulate served as a funnel-drive made of thick glazed paper, equipped with a dispenser that regulates the flow of glass granules. The diameter of the outlet of the dispenser ranged from 0.2 to 2 mm. During the experiment, the container was fixed in the movable bracket of the tripod and moved relative to the surface of the glass as the bulk cone grew, so that the height of the glass granules falling on top of the forming cone remained constant at 100 mm. To locate the sources of AE signals resulting from the collision of granules, their subsequent bounce and rolling along the inclined surface of the formed cone, seven R15α transducers mounted on the back of the glass were used. Six PAEs were evenly spaced along the perimeter of the aluminum waveguide at a distance of 70 mm from the central PAE No. 7, which is opposite to the place where the granule flow falls onto the formed cone. In FIG. Figure 2 shows the layout of PAEs, the parameters of planar location and clusterization of AE events, including the size of location clusters, the relationship between the color of the clusters and the number of recorded events, as well as the maximum amplitude of the detected pulses.

Consider the results of one of the experiments, during which a glass granulate with a volume of 260 ml and a mass of 546 g with a granule size of 200-400 μm was used, loaded into a funnel-drive made of glazed paper. The outflow of glass granules from the container occurred within 317 seconds of the experiment from 40 to 357 seconds inclusive. As a result, on the surface of the sheet glass on which the aluminum waveguide was mounted, a bulk cone of regular glass granulate was formed with an average diameter at the base of 158 mm, a height of 53 mm and a tilt angle of 34 °.

In FIG. Figure 3 presents the results of AE monitoring of the formation of the bulk cone of glass granulate on the surface of an aluminum model.

As follows from graph a in FIG. 3 - accumulation of location pulses by channels of the AE system, during AE monitoring of the formation of the bulk cone of glass granulate, a total of (N _Σ ) _l = 14037 AE events was recorded. The greatest number of location pulses during the experiment was recorded by the central converter - PAE No. 7. Peripheral converters - PAE No. 1-No. 6, equidistant from the central one at a distance of 70 mm, recorded 3-4 times less number of location pulses. Based on the intensity of detection of location pulses, characterized by the slope of the curves, the accumulation of AE events can be divided into three periods: τ ₁ = 40-60 s, τ ₂ = 60-204 s and τ ₃ = 204-357 s experiment. Within 20 seconds of the period τ _{1, the} impact of the falling glass granules occurred directly with the surface of the aluminum cone model. The stage τ ₂ is already characterized by the collision of glass granules with a growing layer of glass granulate forming on the surface of the model cone. As the thickness of the glass granulate layer increased and its damping ability increased, the intensity of the accumulation of location pulses by the AE channels of the system dropped noticeably. At stage τ ₃ , the growth of accumulation of location pulses is again recorded due to avalanche-like collapse of the top of the bulk cone, the frequency of which increased with increasing thickness of the glass granulate layer.

In graphs b and c of FIG. Figure 3 presents the pictures of the coordinate and amplitude locations recorded during the formation of the bulk cone of AE events. As follows from graph b, the highest density of localized events, exceeding 120 units / cm ² , and marked on the coordinate location graph by red clusters, was recorded in the region between concentric circles formed by radii of 30 mm and 60 mm. In the region under consideration, as can be seen from the graph with the amplitude location, the location clusters were red, corresponding to the maximum pulse amplitude u _m ≥60 dB according to the designations adopted for clustering (see Fig. 2).

As follows from graphs e and ƒ in FIG. 3, reflecting the dynamics of changes in the maximum amplitude and duration of location pulses during the formation of the bulk cone, the pulses of maximum amplitude u _m = 70-90 dB and duration t _u = (50-65) ⋅10 ³ μs were recorded at the stage τ ₁ as a result of the collision of the incident granules of glass with the surface of an aluminum model. When a loose damping layer of glass granulate was formed at the τ ₂ stage on the model surface, the amplitude and duration of the recorded location pulses began to noticeably decrease as it grew. A particularly sharp drop in these parameters of the location pulses was observed at the stage τ ₃ , when their level no longer exceeded u _m = 75 dB and t _u = 10⋅10 ³ μs.

Locational pulses recorded during AE monitoring were formed in the field of descriptors: relative energy (E _u ) and average oscillation frequency (N _u / t _u ), three energy clusters B, C and H, the boundaries of which are shown in diagram d of FIG. 3. The lower cluster (H) with boundary values of the intervals: parameter E _u = 60-80 μV / unit, parameter N _u / t _u = 10-210 kHz, average cluster (C): E _u = 80-100 μV / units, N _u / t _u = 20-180 kHz and the upper cluster (B): E _u = 100-130 μV / unit, BN _u / t _u = 50-150 kHz.

In diagram g of FIG. Figure 3 shows the dynamics of changes in the weight content of location pulses W _H , W _C , W _B , recorded in energy clusters H, C, B during AE monitoring of the formation of the bulk cone of glass granulate. As follows from the graph g, the largest changes in the weight content of location pulses in the energy clusters H, C, B occurred during the first 20 seconds of the period τ ₁ during the formation of the initial layer of glass granulate on the surface of the aluminum model. In this case, the weighted content of location pulses in cluster B decreased from 80% to W _B = 20%, while in clusters C and H it increased from 10% to W _C = 40% and W _H = 35%. At stage τ _{2, the} drop in the parameter W _B and the increase in the parameters W _C and W _H continued from 60 to 120 second of the experiment, after which the process of changing the weight content of location pulses in the energy clusters stabilized and the parameter values were W _B = 6%, W _C = 52% and W _H = 42%. In the period τ ₃ , as the frequency of avalanche-like sliding of the granules from the top of the cone increased, the weight content of location pulses in cluster H increased and their content in clusters C and B decreased. At the end of the experiment, the weight content of location pulses in energy clusters was: W _H = 59% , W _C = 38% and W _B = 3%.

- активности регистрации локационных импульсов каналами АЭ системы. Как следует из сопоставления графиков h и i, параметры частоты и активности регистрации локационных импульсов каналами АЭ системы на этапах мониторинга процесса формировании насыпного конуса изменялись достаточно синхронно. Этап τ₁, характеризуется резким возрастанием активности регистрации локационных импульсов всеми каналами АЭ системы. В начальный период этапа τ₁, когда происходило соударение падающего стеклогранулята с поверхностью алюминиевой модели, основной массив составляли импульсы кластера В, наибольшая частота регистрации которых достигала ω_B=20-25 Гц. На последних секундах этапа τ₁ резко возрастает частота регистрации локационных импульсов, относящихся к кластерам С и Н, уровень которых на 60 секунде эксперимента составлял ω_C=80 Гц и ω_H=94 Гц. В этот период активность регистрации локационных импульсов седьмым каналом, ПАЭ которого был установлен напротив падения потока гранул стекла на алюминиевую модель, достигала

.Graphs h and i in figure 3 reflect the dynamics of changes in the parameters ω _B , ω _C , ω _H - the frequency of registration of location pulses in energy clusters and the parameter

- activity of detecting location pulses by AE system channels. As follows from the comparison of the h and i graphs, the parameters of the frequency and activity of detecting location pulses by the AE channels of the system at the stages of monitoring the process of forming a bulk cone changed quite synchronously. Stage τ ₁ is characterized by a sharp increase in the activity of detecting location pulses by all channels of the AE system. In the initial period of stage τ ₁ , when the incident glass granulate collided with the surface of the aluminum model, the main array consisted of pulses of cluster B, the highest detection frequency of which reached ω _B = 20–25 Hz. In the last seconds of stage τ ₁ , the frequency of detecting location pulses related to clusters C and H sharply increases, the level of which at 60 seconds of the experiment was ω _C = 80 Hz and ω _H = 94 Hz. During this period, the activity of detecting location pulses by the seventh channel, whose PAE was installed opposite the drop in the flow of glass granules on the aluminum model, reached

.

а в конце второго этапа на 204 с эксперимента уже не превышала

At step τ _{2, the} flow of granules fell already on the formed loose layer of glass granulate. As a result of this, the energy of the impact of the falling granules on the loose surface of the glass granulate was noticeably extinguished. According to the DVR, the cone growth process was accompanied by an increase in its diameter due to rolling and sliding of granule flows from the top of the cone to the base. The flow of granules falling to the top of the bulk layer of glass granulate eroded it, causing massive rolling of granules, periodically accompanied by avalanche-like landslides. This is responsible for the intense pulsations of AE signal registration on the h and i graphs. As the thickness of the glass granulate layer increased, the damping ability of the bulk cone increased, as a result of which the detection frequency of location pulses in clusters B, C, and H synchronously decreased and at the end of the stage 204 s of the experiment amounted to: ω _B = 7 Hz, ω _C = 30 Hz, and ω _H = 20 Hz. The maximum activity of the AE system channels at the τ ₂ stage was recorded during the period 60–80 s of the experiment, after which a gradual decrease in activity was observed on all channels of the AE system. In this case, the highest AE activity was observed on the seventh channel, on which the registration of location pulses in the initial period τ ₂ (60-80 s) reached its maximum

and at the end of the second stage by 204 from the experiment it did not exceed

регистрировалась седьмым каналом, ПАЭ которого был расположен оппозитно месту падения гранул стекла на поверхность алюминиевой модели.The beginning of stage τ _{3 is} accompanied by a sharp increase in the frequency of detection of location pulses belonging to clusters C and H, the level of which increased to ω _C = 100 Hz and ω _H = 180 Hz. In this case, the frequency of detecting location pulses in cluster B decreased almost to zero. This nature of the change in the frequency of registration of pulses in energy clusters B, C, and H at stage τ ₃ is caused by avalanche-like collapse of the apex of the cone, when the main array of location pulses are signals from the lower energy cluster, the frequency of which increased with increasing thickness of the glass granulate layer. At the same time, the activity of detecting location pulses on all channels also increased. The highest activity reaching

was recorded by the seventh channel, the PAE of which was located opposite to the place where the glass granules fell on the surface of the aluminum model.

Динамика изменения этих параметров, приведенная на графиках g, h и i фиг. 3, дает наглядное представление о происходящих неустойчивых переходных процессах на всех этапах формирования насыпного конуса стеклогранулята, а также при изменении их тренда в точках структурной и системной бифуркации.As follows from the analysis of the results of AE monitoring of the formation of the bulk cone of glass granulate, the most informative parameters that allow you to get a clear idea of the unstable transients that occur are the parameters of the weight content of location pulses in energy clusters W _H , W _C , W _B , and their detection frequencies ω _B , ω _C , ω _H and activity of detecting location pulses by channels of AE systems

The dynamics of changes in these parameters shown in the graphs g, h and i of FIG. 3, gives a visual representation of the occurring unstable transient processes at all stages of the formation of the bulk cone of glass granulate, as well as when their trend changes at the points of structural and systemic bifurcation.

Synchronization of video and acoustic emission registration of the process of formation of the bulk cone of glass granulate made it possible to identify the main types of AE signals and establish the nature of their occurrence using temporary gating of transients. During the experiment, the following types of AE pulses were recorded. The first type is signals recorded during elastic collisions and rebounds of glass granules from the surface of an aluminum model. The second type is signals recorded as a result of collision and introduction of granules into a loose layer of glass granulate. The third type is the signals recorded during the periodic collapse of the top of the cone and the sliding of the outer layer of glass granulate as a result of the shift of the layers.

In the high-speed video images of FIG. Figure 4 shows typical moments of the formation of a bulk cone of glass granulate at the stages τ ₁ , τ ₂ , τ ₃ . A comparison of the graphs g, h and i of the criteria parameters in FIG. 3, when the accumulation trend of glass granulate changes at the points of structural and systemic bifurcation with synchronously recorded frames of high-speed video recording, it was possible to trace in detail the dynamics of transients at the stages of the formation of the bulk cone and to accurately identify the nature of the main sources of location pulses characteristic of waveforms and spectra.

At the stage τ _{1, the} process of forming a layer of glass granulate on the aluminum model was as follows. The granules, upon hitting the top of the model, bounced off the point of impact, repeatedly impacting with its surface at a distance of 30-60 mm, where it was recorded on graph b of FIG. 3 maximum density of location pulses. After a rebound from the surface of the model, the granules could make 3-4 rebounds from the glass plane, after which they rolled along it colliding with other granules to a complete stop. In this case, the acoustic emission system mainly recorded pulses resulting from elastic collisions with the surface of the aluminum model and the plane of the glass plate. The maximum amplitude level of the pulses of the granules rolling along the plane of the glass was already below the level of the discrimination threshold u _th = 30 dB.

As can be seen from the video recording fragment a in FIG. 4, after the first impact on the top of the aluminum model, the granules made several more rebounds along its surface and the plane of the glass plate. Moreover, as a result of such collisions, at the stage τ ₁ , location pulses of three main types were recorded, the waveforms and spectra of which had the characteristic form shown in the graphs of FIG. 5.

As can be seen from the graphs in FIG. 5, the recorded AE pulses resulting from the collision of the glass granulate with the surface of the aluminum model and the plane of the glass plate had similar waveforms and spectra. They are distinguished by the level of recorded amplitudes and the density of the released energy in the passband of frequency filters Δƒ = 30-500 kHz. The main energy of the spectra of such pulses, as follows from graphs b in FIG. 5, is localized in the region of resonant frequencies of the used converters R15α-ƒ _p = 150-170 kHz.

The accumulation of glass granulate on the surface of an aluminum waveguide at the τ ₂ stage is a complex multifactor process. In the period of 60-90 s, the maximum AE activity at this stage (see graphs h and i in Fig. 3), the pulses were recorded as a result of the impact of the flow of falling granules with the apex of the cone, their rebound and penetration into the loose surface layer of granulate, the initiation of landslides of granulate in the form of mudflows and their movement along the conical surface of the waveguide. In FIG. Figure 6 shows typical waveforms and spectra of AE pulses recorded during this period at the τ ₂ stage.

As the thickness of the glass granulate layer increased at the stage of τ _{2, the} flow of granules, colliding with its surface, generated pulses of noticeably smaller amplitude and duration. When the granules collided with the loose surface of the glass granulate, both rebound of the granules and their introduction into the surface layer at the point of impact were observed. The spectral forms of AE signals No. 1 and No. 2 in FIG. 6, recorded during the first and repeated collisions of granules with a loose layer of glass granulate of the forming cone, do not significantly differ from the frequency distribution of energy in the spectra shown in figure 6. The introduction of granules into the loose surface layer of the cone, accompanied by impact on the nearest “neighbor”, caused impulses type No. 3 in FIG. 6, which occur upon contact of rubbing surfaces. Such an active introduction of falling granules into the loose surface layer of glass granulate upon reaching the critical thickness of the bulk layer in the region of the top of the cone initiated the occurrence of mudflows of rolling granules. In picture b of FIG. 4, obtained in the process of high-speed video recording, a typical mudflow resulting from a local collapse at the top of the forming bulk cone is shown. The graphs of FIG. 6 pulses of type No. 4 arose at the moments of debris flow initiation, and pulses No. 5 during the sliding of the outer layer of glass granulate along the inclined surface of the cone.

As follows from FIG. 6, the waveforms and spectra of signals No. 4 and No. 5 differed from the other types being analyzed not only in terms of the amplitude and density of the recorded energy, but also in the shape and spectral distribution of the released energy. AE pulses recorded during the initiation of mudflows and their sliding along the inclined surface of the cone are characterized by a unique waveform and a characteristic spectrum of the energy density distribution. If the energy of signals of types No. 1-No. 3 has a maximum at the resonant frequency of the applied PAEs Δƒ _p = 150-170 kHz, then the peak of the energy distribution of signals of types No. 4 and No. 5 generated by the processes of initiation and movement of mudflows of glass granulate is localized in a rather narrow low-frequency region Δƒ _m = 40-60 kHz.

The cone formation process at the τ ₃ stage was accompanied by periodically collapsing of its top and avalanche-like sliding of the glass granulate masses to its base. Moreover, the frequency of avalanche collapse and mudflows increased as the height of the glass granulate layer increased, which during the experiment did not exceed 20 mm on the surface of the aluminum model. The subsidence of the top of the cone under the action of its own weight generated a shear wave over the entire thickness of the bulk layer of glass granulate. In this case, avalanche-like creeps of the outer layer of glass granulate arose along the entire perimeter of the forming cone. In fragment C, the high-speed video recording of FIG. Figure 4 shows the avalanche-like movement of a glass granulate layer over the surface of an aluminum model caused by subsidence of the top of the forming cone.

When the apex of the cone subsided and avalanches descended at the stage of τ ₃ , AE pulses were recorded related not only to the lower, but also to the middle and even to the upper energy clusters. Moreover, the waveforms of these signals and their spectra shown in the graphs of FIG. 8 differ markedly from those previously recorded in steps τ ₁ and τ ₂ shown in FIG. 5 and 6.

As follows from the graphs of FIG. 7, the waveforms and AE spectra of signals of type No. 1 and No. 2 arising at the moments of cone vertex subsidence noticeably differ from signals during avalanche-like sliding of the outer layer of glass granulate recorded at the top of cone No. 3 and at its base No. 4. The waveforms and spectra of the latter are quite similar to those that arise during the debris flow of glass granulate (see graphs 4 and 5 in Fig. 6). The main energy of the signals during subsidence of the top of the cone is localized in a wider range of 40-160 kHz compared with the frequency range of 40-60 kHz characteristic of the spectra of signals recorded during avalanche-like sliding of the surface layer of glass granulate.

выделяемой на пиковой частоте ƒ_m регистрируемого максимума и частоте резонанса ƒ_R применяемых преобразователей, в полосе пропускания Δƒ цифрового фильтра АЭ системы.Locational pulses having similar waveforms and spectra recorded at the stages of the formation of the bulk cone obviously belong to similar or close sources of AE radiation. Therefore, in the field of the most characteristic parameters that carry information about the shape of the signals, they should form identification clusters that testify to the nature of the sources of AE events. In spectral analysis, the separation of recorded location pulses into clusters with similar spectra belonging to similar or similar types of AE events is performed in the parameter field η - ƒ _Δ using the partial energy density coefficient

allocated at the peak frequency ƒ _{m of the} detected maximum and the resonance frequency ƒ _{R of the} applied converters in the passband Δƒ of the digital filter of the AE system.

регистрируемой на частоте ƒ_m, к плотности энергии

на резонансной частоте ƒ_R=160 кГц преобразователя R15-α, в частотном диапазоне Δƒ=30-500 кГц полосы пропускания цифрового фильтра АЭ системы.In FIG. Figure 6 shows the result of dividing location pulses recorded during the formation of the bulk cone of glass granulate into energy clusters in the parameter field η - Δƒ reflecting the ratio of the peak energy density

recorded at a frequency ƒ _m , to the energy density

at the resonant frequency ƒ _R = 160 kHz of the R15-α converter, in the frequency range Δƒ = 30-500 kHz of the passband of the digital filter of the AE system.

Formed in the descriptor diagram of FIG. 8 clusters of I, II, III location pulses correspond to certain types of signal sources. Cluster I includes pulses during the collision of the falling granules with an aluminum waveguide, repeated impacts after bouncing along the surface of the forming bulk cone and glass plate. Cluster II combines the pulses resulting from the introduction of falling granules into the loose layer of glass granulate and the initiation of mudflows of glass granulate at stages τ ₂ and τ ₃ , as well as periodically occurring subsidence of the top of the forming cone at the final stage of the experiment. Cluster III combines pulses arising from mudflow and avalanche-like collapses of the surface loose layer of glass granulate from the top of the bulk cone at the stages of its formation.

при которых происходит качественное изменение структуры системы, находящейся в состоянии неустойчивого равновесия накопления стеклогранулята на конической поверхности волновода. В точках структурной бифуркации толщина слоя стеклогранулята, накопленная на конической поверхности волновода, достигает критического уровня δ≈20 мм, при котором под действием собственного веса происходит его проседание и лавинообразное обрушение. Системная бифуркации на графиках е - i динамического изменения параметров системы наглядно проявляется в двух точках. Точка B₁ - момент прекращения непрерывной эмиссии, характерной для этапа τ₁, при которой регистрируются импульсы с длительностью t_u>65⋅10³ мкс и амплитудой u_m=15-90 дБ, возникающие при соударении потока гранул с поверхностью алюминиевой модели, совпадает с началом этапа τ₂, когда на ее поверхности образуется рыхлый слой стеклогранулята. Точка В₂, отделяющая этап τ₂, характеризуемый стабильным накоплением стеклогранулята на конической поверхности волновода и локальными селевыми сползаниями стеклогранулята с вершины конуса, возрастанием его демпфирующей способности, снижением уровня активности АЭ, амплитуды и длительности регистрируемых локационных импульсов (см. графики d, е и i на фигуре 4), от этапа τ₃, которому присущи периодически происходящие оседания вершины формирующегося конуса и лавинообразные обрушения наружного слоя стеклогранулята.An analysis of the dynamics of changes in the parameters shown in graphs e - i in Figure 4 allows you to accurately determine the points of structural and systemic bifurcation of unstable transients recorded during the formation of a bulk cone of glass granulate on the conical surface of the waveguide. On the h and i plots, the points of the structural bifurcation correspond to the moments of the peak minimum values of the parameters ω _{i = H, C, B} and

at which there is a qualitative change in the structure of the system, which is in an unstable equilibrium of accumulation of glass granulate on the conical surface of the waveguide. At the points of structural bifurcation, the thickness of the glass granulate layer accumulated on the conical surface of the waveguide reaches a critical level of δ≈20 mm, at which its subsidence causes its subsidence and avalanche collapse. System bifurcation on the graphs e - i of the dynamic change in the parameters of the system is clearly manifested at two points. Point B ₁ - the moment of termination of continuous emission, characteristic of stage τ ₁ , at which pulses with a duration of t _u > 65⋅10 ³ μs and amplitude u _m = 15-90 dB, which occur when the granule flow collides with the surface of the aluminum model, are recorded with the beginning of step τ ₂ , when a loose layer of glass granulate forms on its surface. Point В ₂ , separating stage τ ₂ , characterized by stable accumulation of glass granulate on the conical surface of the waveguide and local mudflows of glass granulate from the top of the cone, increase of its damping ability, decrease in AE activity, amplitude and duration of detected location pulses (see graphs d, е and i in figure 4), from step τ ₃ , which is characterized by periodically occurring subsidence of the vertices of the forming cone and avalanche-like collapse of the outer layer of glass granulate.

The considered example of the demonstration of the proposed method and device of a bifurcation model for modeling the dynamics of transients and recording points of structural and systemic bifurcation using a conical aluminum waveguide with a base diameter of 140 mm and an inclination angle of 30 °, covered with a damping layer of glued gauze fabric on the conical surface of which conditions for the accumulation of the critical mass of the granulate, its settling under the action of its own weight and the subsequent avalanche-like collapse at m The thin thickness of the formed layer, δ = 10--20 mm, clearly demonstrated the possibility of temporal gating of unstable transients and registration of structural and systemic bifurcation points at the stages of the formation of the bulk cone of glass granulate using high-speed video recording synchronized with acoustic emission monitoring.

Bibliography.

1. Makhutov N.A., Vasiliev I.E., Ivanov V.I., Elizarov S.V., Chernov D.V. Testing the methods of cluster analysis of arrays of acoustic emission pulses during the formation of the bulk cone of glass granulate. // Factory Laboratory. - 2016. No. 5. from. 44-54.

2. Ivanov V.I., Barat V.A. Acoustic emission diagnostics. M .: Publishing house "Spectrum", 2017.368 p.

Claims (11)

1. A method for simulating transient damage accumulation processes in a diagnosed object with registration of structural and systemic bifurcation points, including the formation of a granulate bulk cone on a horizontal surface, during which the dynamics of transient processes resulting from the accumulation of the critical mass of granulate at the top of the cone and its settling under the action are recorded dead weight and subsequent avalanche collapse, using high-speed video synchronized with acoustic emission monitoring, recording the activity of accumulation of location pulses by channels of the acoustic emission system

characterized in that, using a conical surface, the conditions for granular collapse are artificially created with a small thickness of the formed layer δ = 10-20 mm, while transient processes are temporarily gated by pulsing every second into clusters of lower (H), middle (C) and upper ( _C ) energy level, calculate the frequency of their registration ω _{i = H, C, B} and the percentage of W _{i = H, C, B} according to the formula: Wi = (N _i / N _Σ ) ⋅100%, where N _{i = H, C, B} is the number of pulses in the i-th cluster, N _Σ is the total number of accumulated location pulses; the dynamics of these parameters and the change in the trend of transients at the points of structural and systemic bifurcation are recorded on the graphs, confirming the moments of their registration by high-speed video frames. 2. The bifurcation model device, using which the method according to claim 1 is implemented, includes a tripod consisting of a flat base, a vertical stand and an arm fixed to it, acoustic emission transducers mounted on the back of the tripod base, a glass plate resting on the transducers through a layer of contact lubricant, a funnel-storage granulate fixed in an arm above the center of the plate, communication cables, preamplifiers of acoustic emission signals, an acoustic collection and processing unit emission data, control computer, high-speed video camera, characterized in that a conical waveguide is installed through a contact lubricant layer on the glass plate opposite to the center of the funnel-accumulator equipped with a dispenser, the conical surface of which is covered with a damping layer, the bracket is made movable with the possibility of adjusting the position of the dispenser relative to the top of the bulk cone of the granulate at a given level of 100-150 mm 3. The device according to p. 2, characterized in that the granules used are granules of ground lead glass with a size of 200-400 microns. 4. The device according to claim 2, characterized in that one of the acoustic emission transducers is installed in the center of the conical waveguide, and the rest evenly around the periphery of its base. 5. The device according to claim 2, characterized in that a solid aluminum cone with a base diameter of 140-150 mm and an inclination angle of 30-33 ° is used as the waveguide. 6. The device according to p. 2, characterized in that as a damping layer used a coating of gauze, impregnated with glue. 7. The device according to claim 2, characterized in that the horizontal dimensions of the glass plate are 2-2.5 times the diameter of the base of the conical waveguide. 8. The device according to p. 2, characterized in that the video camera is located at an angle of 60 ° relative to the plane of the glass plate at a distance of 400-500 mm from the surface of the conical waveguide.

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