Assessment of the Mechanism of Adhesive Destruction Coatings

2021 ◽  
Vol 410 ◽  
pp. 841-846
Author(s):  
Valentina I. Loganina
Keyword(s):  
Acoustic Emission ◽  
Contact Zone ◽  
Acoustic Signal ◽  
Large Amplitude ◽  
Polyvinyl Acetate ◽  
Slow Growth ◽  
Bond Breaking ◽  
Plastic Deformations ◽  
Signal Energy

Information on deformation of coatings at different loading levels during peeling is given. It is shown that the deformations of the organosilicon coating appear already at the initial stages of loading, and the obtained data correlate with the data on acoustic emission. For a polyvinyl acetate coating at low loading levels, equal to 0.3-0.4 R, the release of acoustic signal energy is not observed. The absence of signals with a large amplitude at loading levels up to 0.7-0.8 R indicates the development of plastic deformations in the contact zone of the coating with the substrate. It was found that early localization of bond breaking in the contact zone, leading to the formation of a fracture focus, occurs in organosilicon coatings KO-168. For PVAC coatings, an abrupt growth of cracks is characteristic, which is preceded by its slow growth. The pseudoplastic mechanism of destruction of PVAC coatings has been established. The influence of the nature of the substrate on the change in the nature of the peeling of the coatings is considered.

Attenuation of Acoustic Emission Signals in Structural Interfaces

2012 ◽  
Vol 569 ◽  
pp. 343-346
Author(s):  
Xiang Hong Wang ◽  
Hong Wei Hu ◽  
Zhi Yong Zhang
Keyword(s):  
Acoustic Emission ◽  
Real World ◽  
Simple Structure ◽  
Size Structure ◽  
Experimental Results ◽  
Signal Energy ◽  
Real World Applications ◽  
Structural Interfaces ◽  
Ae Signals

Received acoustic emission (AE) signals are transmitted across structural interfaces in many real-world applications. This paper studies attenuation of the signals across two common structural interfaces. The experimental results indicate that interface has effects on attenuation, which depends on the relative scales of structures. Signal energy is strengthened due to multiple flections of signals on the small-size structure when an interface is constructed by different scales. Thus the received signals are distorted worse than the original signals. So it is a better way to mount sensors on a simple structure with a size as much as a structure incurred AE sources.

scholarly journals ANALYSIS OF THE EFFICIENCY OF SPECTRAL ESTIMATION METHODS FOR DETECTION OF UAV ACOUSTIC SIGNALS

2021 ◽  
pp. 4-15
Author(s):  
М. V. Buhaiov ◽  
V. V. Branovytskyi ◽  
Y. O. Khorenko
Keyword(s):  
Acoustic Emission ◽  
Unmanned Aerial Vehicles ◽  
Acoustic Signal ◽  
Spectral Estimation ◽  
Acoustic Signals ◽  
Frequency Resolution ◽  
Estimation Methods ◽  
Signal To Noise ◽  
Statistical Quality ◽  
Aerial Vehicles

One of the most important components of counteracting small unmanned aerial vehicles is their reliable detection. You can use propeller noise to detect such objects at short distances. An energy or harmonic detector is used to receive unmanned aerial vehicles acoustic emission. At low signal-to-noise ratios , which is most common in practice, the harmonic detector provides a higher probability of detection compared to energy. The principle of the harmonic detector is based on spectral analysis of acoustic signals. A mathematical model of the acoustic signal of an aircraft-type unmanned aerial vehicles is proposed. It is shown that at short time intervals (tens of milliseconds) such signals can be considered as stationary and for its analysis can be used known methods of spectral estimation. Nonparametric, parametric and subspace methods of spectral estimation are considered for processing of acoustic emission of unmanned aerial vehicles. To conduct a comparative analysis of different methods of spectral estimation, a statistical quality index was used, which can be calculated as a variation of the estimation of power spectral density. This index characterizes the method of spectral estimation in terms of frequency resolution and the ability to detect harmonic components of the signal into noise and not create interference that exceeds the amplitude of the signal. As a result of researches it was established that at high signal-to-noise ratios parametric methods are more effective in comparison with nonparametric. However, such a statement will be valid only if the correct order of the model. It is shown that the use of spatial methods is impractical for the analysis of acoustic signals of unmanned aerial vehicles. The use of the value of the statistical quality indicator as a threshold for deciding on the presence or absence of the acoustic signal of the unmanned aerial vehicles in the adopted implementation and its further processing should be used at SNR values greater than 5 dB.

scholarly journals Slow growth of a crack with contact zone

2017 ◽  
pp. 38-43
Author(s):  
A.A. Kaminsky ◽  
◽  
M.F. Selivanov ◽  
Keyword(s):  
Contact Zone ◽  
Slow Growth

Application of acoustic emission for monitoring shear behavior of bonded concrete–rock joints under direct shear test

2012 ◽  
Vol 39 (8) ◽  
pp. 887-896 ◽  
Author(s):  
Z.A. Moradian ◽  
G. Ballivy ◽  
P. Rivard
Keyword(s):  
Acoustic Emission ◽  
Shear Strength ◽  
Normal Load ◽  
Adhesive Bond ◽  
Shear Behavior ◽  
Displacement Rate ◽  
Bond Breaking ◽  
Bonded Joints ◽  
Direct Shear ◽  
Shear Process

Studying shear behavior and failure mechanism of concrete–rock interfaces between concrete structures and rock mass is highly important. To this end, laboratory direct shear tests were conducted on several bonded interfaces. The effect of normal stress, displacement rate, and bonding percentage on shear behavior of bonded joints were also evaluated. The results showed that the adhesive bond between concrete and rock has the most important effect on shear mechanism of concrete–rock interfaces. When the normal load is low, the asperities do not contribute in shear process, so the shear strength of the joints is governed by adhesive bond. The only contribution of the asperities is that they show a small peak after bond breaking peak. When the normal load is high, the asperities break simultaneously with adhesive bond and they show their contribution in the whole shear process. In a constant normal load, by decreasing bonding percentage, the brittle failure of the bonded joints is changed into softening failure because of less contribution of the adhesive bond and more contribution of the rough asperities in joint failure. Acoustic emission (AE) monitoring of bonded joints showed that for all different tested samples under various loading conditions, there has been no or very few AE activities before adhesive bond breaking point, indicating that other parameters (roughness, normal load, displacement rate) are impressed by adhesive bond and maximum shear strength is determined by this parameter.

The Pipeline Leak Location Techniques Based on Modal Acoustic Emission

2004 ◽  
Author(s):  
Jingpin Jiao ◽  
Bin Wu ◽  
Cunfu He ◽  
Renyuan Fei
Keyword(s):  
Acoustic Emission ◽  
Acoustic Signal ◽  
Cross Correlation ◽  
Guided Waves ◽  
Correlation Method ◽  
Signal Propagation ◽  
General Process ◽  
Leak Location ◽  
Waves Propagation ◽  
The One

Due to the multiple modes and dispersive nature of acoustic leak signal propagation in pipeline, the traditional AE cross correlation method was ineffective to location the leak in pipeline. Based on the theory of modal acoustic emission (MAE), two different pipeline leak location techniques are brought forward. One is based on two modes with one sensor; the other is based on one mode with two sensors. The general process is narrated as following three steps. Firstly, based on the theory of guided waves propagation in cylinder, the acoustic leak signals in positions nearby the sensor(s) can be predicted using the information of dispersion characteristics of guided waves in pipeline and the acoustic signal received by the sensor(s). Secondly, by transformed the predicted signals in time and space, two (one) individual modes (mode) of the acoustic signal at the position of the sensor(s) are isolated. By correlated the two modes of the same sensor (one mode of the two sensors), the leak position can be located accurately. The leak location experiments have been carried out to prove the validity of the one sensor and two sensors leak location techniques; it is indicated that the location errors of the two leak location techniques are usually less than 5%, and the techniques can be used to location the leak of pipeline filled with liquid or gas.

Quantitative Relationships for Acoustic Emission from Orthogonal Metal Cutting

1981 ◽  
Vol 103 (3) ◽  
pp. 330-340 ◽  
Author(s):  
Elijah Kannatey-Asibu ◽  
David A. Dornfeld
Keyword(s):  
Acoustic Emission ◽  
Metal Cutting ◽  
Energy Content ◽  
Energy Levels ◽  
Cutting Parameters ◽  
Signal Energy ◽  
Emission Signal ◽  
Orthogonal Metal Cutting ◽  
Ae Signal ◽  
Work Of Deformation

Theoretical relationships have been drawn between acoustic emission (AE) and the metal cutting process parameters by relating the energy content of the AE signal to the plastic work of deformation which generates the emission signals. The RMS value of the emission signal is expressed in terms of the basic cutting parameters. Results are presented for 6061-T6 aluminum and SAE 1018 steel over the range of speeds 25.2 to 372 sfm (0.128 to 1.9 m/s) and rake angles 10 to 40 deg. Good correlation has been found between predicted and experimental signal energy levels. In addition, AE generation from chip contact along the tool face is studied and the AE energy level reflects the existence of chip sticking and sliding on the tool face, and indicates the feasibility of utilizing AE in tool wear sensing.

scholarly journals Detection and Recording of Acoustic Emission in Discrete IGBT Transistors

2018 ◽  
Vol 1 (1) ◽  
pp. 27-31 ◽  
Author(s):  
Radosław Gordon ◽  
Andrzej Dreas
Keyword(s):  
Acoustic Emission ◽  
Experimental Research ◽  
Acoustic Signal ◽  
Sensor Signal ◽  
Acoustic Emission Sensor

Abstract The article presents the results of experimental research, which is to show a correlation between the change of operating status of single IGBT transistor and its acoustic emission. Sensor signal was obtained with oscilloscope in order to further process it digitally and determine possibility of the damage to the element based on registered acoustic signal.

scholarly journals Modeling of Surface Geometric Structure State After Integratedformed Milling and Finish Burnishing

2017 ◽  
Vol 25 (2) ◽  
pp. 131-136 ◽  
Author(s):  
Stefan Berczyński ◽  
Daniel Grochała ◽  
Zenon Grządziel
Keyword(s):  
Physical Model ◽  
Contact Zone ◽  
Experimental Studies ◽  
Element Model ◽  
Surface Plastic ◽  
Plastic Deformations ◽  
Mean Values ◽  
Milled Surface ◽  
Structure State ◽  
Burnishing Process

Abstract The article deals with computer-based modeling of burnishing a surface previously milled with a spherical cutter. This method of milling leaves traces, mainly asperities caused by the cutting crossfeed and cutter diameter. The burnishing process - surface plastic treatment - is accompanied by phenomena that take place right in the burnishing ball-milled surface contact zone. The authors present the method for preparing a finite element model and the methodology of tests for the assessment of height parameters of a surface geometrical structure (SGS). In the physical model the workpieces had a cuboidal shape and these dimensions: (width × height × length) 2×1×4.5 mm. As in the process of burnishing a cuboidal workpiece is affected by plastic deformations, the nonlinearities of the milled item were taken into account. The physical model of the process assumed that the burnishing ball would be rolled perpendicularly to milling cutter linear traces. The model tests included the application of three different burnishing forces: 250 N, 500 N and 1000 N. The process modeling featured the contact and pressing of a ball into the workpiece surface till the desired force was attained, then the burnishing ball was rolled along the surface section of 2 mm, and the burnishing force was gradually reduced till the ball left the contact zone. While rolling, the burnishing ball turned by a 23° angle. The cumulative diagrams depict plastic deformations of the modeled surfaces after milling and burnishing with defined force values. The roughness of idealized milled surface was calculated for the physical model under consideration, i.e. in an elementary section between profile peaks spaced at intervals of crossfeed passes, where the milling feed fwm = 0.5 mm. Also, asperities after burnishing were calculated for the same section. The differences of the obtained values fall below 20% of mean values recorded during empirical experiments. The adopted simplification in after-milling SGS modeling enables substantial acceleration of the computing process. There is a visible reduction of the Ra parameter value for milled and burnished surfaces as the burnishing force rises. The tests determined an optimal burnishing force at a level of 500 N (lowest Ra = 0.24 μm). Further increase in the value of burnishing force turned out not to affect the surface roughness, which is consistent with the results obtained from experimental studies.

scholarly journals Damage Accumulation in Cyclically-Loaded Glass-Ceramic Matrix Composites Monitored by Acoustic Emission

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
D. G. Aggelis ◽  
K. G. Dassios ◽  
E. Z. Kordatos ◽  
T. E. Matikas
Keyword(s):  
Acoustic Emission ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Matrix Composites ◽  
Signal Energy ◽  
Accumulated Damage ◽  
Pull Out ◽  
Threshold Criteria ◽  
Ae Signals ◽  
Barium Osumilite

Barium osumilite (BMAS) ceramic matrix composites reinforced with SiC-Tyranno fibers are tested in a cyclic loading protocol. Broadband acoustic emission (AE) sensors are used for monitoring the occurrence of different possible damage mechanisms. Improved use of AE indices is proposed by excluding low-severity signals based on waveform parameters, rather than only threshold criteria. The application of such improvements enhances the accuracy of the indices as accumulated damage descriptors. RA-value, duration, and signal energy follow the extension cycles indicating moments of maximum or minimum strain, while the frequency content of the AE signals proves very sensitive to the pull-out mechanism.

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