Influence of the Structure of a Gouge-Filled Fault on the Parameters of Acoustic Emission

2019 ◽  
Vol 105 (5) ◽  
pp. 759-765 ◽  
Author(s):  
Alexey A. Ostapchuk ◽  
Kseniya G. Morozova ◽  
Dmitry V. Pavlov

Presented are the results of laboratory experiments on investigating manifestations of acoustic emission (AE) of a gouge-filled fault during stick-slip. The laboratory experiments were held at the slider-model setup, when a granite block slides along a rough granite base under normal and shear loads. In the course of experiments we altered the structure of the two-component filler of the fault and focused on variations of the AE parameters. The kinematic parameters of fault slip events in all the realizations remained approximately the same. The eff ect of gouge structure on the statistics of AE has been revealed. An alteration of proportion of quartz sand / glass beads in the filler of the fault was accompanied by an alteration of the b-value of frequency-energy distribution from 0.53 to 0.85, and the p-value of Omori law from 1.00 to 2.06. Also, it has been demonstrated that the nucleation of a slip event is accompanied by an alteration of the mechanism of AE generation – at the initial stage the 'tensile crack' signals prevailed, while at the final stage – the 'shear crack' signals did. The alteration of AE genesis manifested vividly in a corresponding alteration of the emitted waveforms for all the realizations.

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 20
Author(s):  
Justyna Zapała-Sławeta ◽  
Grzegorz Świt

The study analyzed the possibility of using the acoustic emission method to analyse the reaction of alkali with aggregate in the presence of lithium nitrate. Lithium nitrate is a chemical admixture used to reduce adverse effects of corrosion. The tests were carried out using mortars with reactive opal aggregate, stored under the conditions defined by ASTM C227. The acoustic activity of mortars with a corrosion inhibitor was referred to linear changes and microstructure of specimens in the initial reaction stages. The study found a low acoustic activity of mortars with lithium nitrate. Analysis of characteristic parameters of acoustic emission signals, combined with the observation of changes in the microstructure, made it possible to describe the corrosion processes. As the reaction progressed, signals with different characteristics were recorded, indicating aggregate cracking at the initial stage of the reaction, followed by cracking of the cement paste. The results, which were referred to the acoustic activity of reference mortars, confirmed that the reaction of opal aggregate with alkali was mitigated in mortars with lithium nitrate, and the applied acoustic emission method enabled the detection and monitoring of ASR progress.


1973 ◽  
Vol 12 (64) ◽  
pp. 144-146 ◽  
Author(s):  
W. F. St. Lawrence ◽  
T. E. Lang ◽  
R.L. Brown ◽  
C. C. Bradley

AbstractAcoustic emissions in the audio spectrum are reported from observations of laboratory experiments conducted on snow samples in uniaxial compression. A number of tests show the pattern of acoustic emissions to be a function of the rate of deformation. Over the frequency range 20 to 7 000 Hz acoustic emissions are associated with rates of deformation corresponding to brittle fracture of the snow sample. Though probably present, no acoustic emissions were detected from samples deforming plastically.


Tribology ◽  
2006 ◽  
Author(s):  
Massimo Antonini ◽  
Rodolfo Faglia ◽  
Carlo Remino ◽  
Marco Pedersoli

A noisy mechanical seal is a grave problem, especially in water pumps designed for the automotive industry. The noisiness is often caused by dynamic instability (stick-slip behavior), which occurs when the seal lubrication changes from hydrodynamic to mixed. Starting from this hypothesis, the paper shows a theoretical model that describes the interaction between the seal disks. Therefore this model correlates the acoustic emission to the working conditions of the water pump.


2014 ◽  
Vol 753 ◽  
pp. 217-241 ◽  
Author(s):  
S. V. Kostrykin ◽  
A. A. Khapaev ◽  
I. G. Yakushkin

AbstractThe problem of the decay of intense vortices in a shallow rotated neutrally stratified fluid is considered using simulations with a modified model of von Kármán type and laboratory experiments. The numerical model describes a forced axisymmetric vortex, vertically confined, but infinite in the horizontal plane. It may be used for comparisons with laboratory experiments, in which a quasi-turbulent eddy flow is generated, using magnetohydrodynamic forcing. A detailed analysis of simulations of the free decay of the flow from an initial state, given either by an arbitrary Poiseuille or by a forced stationary profile of vorticity, is provided. Based on this analysis, three different regimes of decay of intense anticyclones in the parameter space of the Ekman and initial Rossby numbers are found. It is shown that anticyclones with large enough Rossby and small enough Ekman numbers may decay to a non-trivial stationary state, or at least they decay much slower than cyclones of the same intensity. The laboratory experiments show much slower decay of intense anticyclones than weak anticyclones or cyclones, and also a dominance of anticyclones over cyclones during the initial stage of decay. These observations qualitatively agree with theoretical predictions.


2015 ◽  
Vol 112 (23) ◽  
pp. 7117-7122 ◽  
Author(s):  
Irit Rosenhek-Goldian ◽  
Nir Kampf ◽  
Arie Yeredor ◽  
Jacob Klein

Intermittent sliding (stick–slip motion) between solids is commonplace (e.g., squeaking hinges), even in the presence of lubricants, and is believed to occur by shear-induced fluidization of the lubricant film (slip), followed by its resolidification (stick). Using a surface force balance, we measure how the thickness of molecularly thin, model lubricant films (octamethylcyclotetrasiloxane) varies in stick–slip sliding between atomically smooth surfaces during the fleeting (ca. 20 ms) individual slip events. Shear fluidization of a film of five to six molecular layers during an individual slip event should result in film dilation of 0.4–0.5 nm, but our results show that, within our resolution of ca. 0.1 nm, slip of the surfaces is not correlated with any dilation of the intersurface gap. This reveals that, unlike what is commonly supposed, slip does not occur by such shear melting, and indicates that other mechanisms, such as intralayer slip within the lubricant film, or at its interface with the confining surfaces, may be the dominant dissipation modes.


2020 ◽  
pp. 80-84
Author(s):  
В.А. Николаев

В зерноуборочных комбайнах, применяемых в настоящее время, очень велики затраты энергии на выделение зёрен из колосьев. Для уменьшения затрат энергии предлагается комбайн, который производил бы выделение зёрен из колосьев методом вытирания. При перемещении верхней части растения лентой верхнего транспортёра по деке происходит выделение зёрен из колосьев. Сквозь отверстия деки проваливается зерновой ворох, содержащий зерновки, частицы соломы, полову, семена сорных растений, пыль и другие компоненты. Первичную очистку зернового вороха от примесей с одновременным снятием с зерна поверхностной влаги целесообразно осуществлять потоком агента сушки. Агент сушки поступает в пространство между декой и расположенным под ней решетом. Перемещение зерновки в потоке агента сушки от деки к решету разбито на этапы с шагом поворота зерновки относительно продольной оси 15°. Начальный этап перемещения зерновки в потоке агента сушки от деки к решету –из положения 0 в положение 1. Рассмотрены силы, воздействующие на зерновку в начале перемещения на начальном этапе. На основе анализа сил и методом построений рассчитаны кинематические параметры зерновки при её повороте относительно продольной оси в процессе перемещения из положения 0 в положение 1. Полученные кинематические параметры зерновки в потоке агента сушки, её траектория от деки до поверхности решета создают возможность проектирования рациональной конструкции комбайна. In combine harvester threshers currently used energy costs for the extraction of grains from ears are very high. To reduce energy costs, a combine is proposed that would extract grains from the ears by grinding method. When the upper part of the plant is moved by the belt of the upper conveyor along the deck, grains are extracted from the ears. Grain heap containing bruchid weevils, straw particles, chaff, weed seeds, dust and other components falls through the holes of the deck. Primary cleaning of grain heap from impurities with simultaneous removal of surface moisture from grain is advisable to be carried out by flow of drying agent. The drying agent enters the space between the deck and the underlying screen. Bruchid weevil displacement in drying agent flow from deck to screen is divided into stages with bruchid weevil pitch relative to longitudinal axis 15°. Initial stage of bruchid weevil movement in drying agent flow from deck to screen is from position 0 to position 1. Forces acting on bruchid weevil at the beginning of movement at the initial stage are considered. Based on the analysis of forces and the method of constructions, kinematic parameters of bruchid weevil are calculated when it turns relative to the longitudinal axis in the process of moving from position 0 to position 1. The obtained kinematic parameters of the bruchid weevil in the flow of the drying agent, its trajectory from the deck to the surface of the screen create the possibility of designing a rational design of the combine.


2021 ◽  
Author(s):  
Zhaoyang Song ◽  
Jie Tan ◽  
Zhiqiang Liu ◽  
Lihui Sun ◽  
Fangbo Ning

Abstract Taking the weakly cemented sandstone of Erdos, China, as the research object, the evolution law between the relative stress of weakly cemented sandstone and the multiparameters of the acoustic emission under different dry-wet cycles was explored, and the critical failure identification mode of weakly cemented sandstone under dry-wet cycles was established. The results show that as the number of dry-wet cycles increases, the wave velocity loss rate gradually increases. Overall, the longitudinal wave loss rate is larger than the shear wave loss rate, indicating that the longitudinal wave is more sensitive to the degradation of weakly cemented sandstone. With an increase in the number of dry-wet cycles, the fracture crack is mainly caused by the main crack penetration failure, and the secondary crack is significantly reduced. The fractal dimension decreases with an increase in the dry-wet cycles and reaches its maximum at 0 dry-wet cycles, which means that 0 dry-wet cycles witness the most complex morphology of fractures within the weakly cemented sandstone. This finding indicates that the dry-wet cycle inhibits the generation and expansion of fractures. The event rate appears to be close to 0 before the rupture, and then the platform oscillates, followed by a sudden increase. The acoustic emission b-value is relatively high during the initial stage and then decreases, which is the initial damage process. The elastoplastic phase rises again, the peak stage decreases rapidly, and the weakly cemented sandstone undergoes unstable damage. The change in the acoustic emission entropy value is exactly the opposite of the b-value change law. When the weakly cemented sandstone reaches the critical failure state under different dry-wet cycles, the relative stress value is 95%. The test results provide new methods and a basis for the damage evolution mechanism and fracture prediction of weakly cemented sandstone under dry-wet cycles.


2021 ◽  
Vol 107 (3) ◽  
pp. 26-32
Author(s):  
V. Kukhta ◽  
◽  
V. Makeev ◽  
O. Kyrmanov ◽  
V. Skalsky ◽  
...  

Purpose. Comparative analysis of the strength of hybrid restoration composites of light polymerization during their local loading using the phenomenon of acoustic emission. The following restoration composites were studied: Latelux, Tetric N-Ceram, Charisma Classic. Results. It was determined that the nature of the destruction of all composites is the same: elastic-plastic at the initial stage of the load with a transition to brittle as its further growth. Three types of composite failure are observed: correct, incorrect and mixed. The first predominated during fracture under the action of local loading of the Latelux composite, for Tetric N-Ceram and Charisma Classic materials a mixed type of fracture is characteristic. Conclusions. Analysis of the parameters of the AE signals showed that the signals had the highest amplitude and energy when the Tetric N-Ceram composite was destroyed, and the lowest – Latelux. All dental composites are dominated by high-energy ductile-brittle and brittle fracture, which indicates the spread of micro- and macrocracks of various sizes in materials. Key words: polymer composites, strength, acoustic emission method.


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