Using Acoustic Emission Monitoring to Observe the De-Bonding Behavior of Rebar in Cyclic Pull-Out Tests

2015 ◽  
Vol 784 ◽  
pp. 377-384
Author(s):  
Kuang Chih Pei ◽  
Yu Cheng Kan
Keyword(s):  
Acoustic Emission ◽  
Cyclic Load ◽  
Acoustic Emissions ◽  
Remaining Life ◽  
Bond Behavior ◽  
Signal Density ◽  
Pull Out ◽  
Emission Monitoring ◽  
Rc Structure ◽  
Ae Signal

This research aimed to reveal the bond behavior and failure mechanism of varying size rebar embedded in concrete with inside pre-crack through a series of quasi-static/cyclic pull-out tests and real-time acoustic emissions monitoring (AE). The obtained AE signal density records of the tests provide potential usage for evaluate the safety of reinforced concrete (RC) structure subjected to cyclic load, as well as quantitative study in the remaining life of RC after earthquake or shake damage.

Bond Behavior of Low-Activated High Aluminate Concrete with Reinforcement under Cyclic Load

2019 ◽  
Vol 972 ◽  
pp. 34-39
Author(s):  
Yu Cheng Kan ◽  
Kuang Chih Pei ◽  
Wei Lin Hsu
Keyword(s):  
Compressive Strength ◽  
Static Loading ◽  
Cyclic Load ◽  
Ultimate Load ◽  
High Alumina ◽  
Test Results ◽  
Normal Concrete ◽  
Bond Behavior ◽  
Pull Out ◽  
Emission Monitoring

The bond behavior of reinforcement and low-activated concrete (LAC) was investigated in this study. The acoustic emission monitoring was also engaged while the specimen being loaded to figure out the inside fracture. Static loading and dynamic loading were applied for both of the LAC and normal concrete in the pull-out tests. The upper load was applied starting from 30% of the static ultimate load Pu with a 10% increment until the failure. The loading frequencies for the test were 0.5 Hz、1.0 Hz and 2.0 Hz. The bond stiffness after each stage of dynamical loads was examined. Test results reveal that the LAC performs higher compressive strength than normal concrete for a given W/C ratio. But, the bond strength of LAC seems not promotes correspondingly. It may be attributed to the conversion effect of high alumina contained in LAC, which leads to more voids inside the concrete.

scholarly journals Experimental Study on Acoustic Emission and Resistivity Response of Sandstone under Constant Amplitude Cyclic Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Kui Wang ◽  
Xue Li ◽  
Zheng Huang ◽  
Mingjie Zhao
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Cyclic Load ◽  
Stress Amplitude ◽  
Rate Of Change ◽  
Rapid Decline ◽  
Engineering Practice ◽  
Loading Frequency ◽  
Constant Amplitude ◽  
Ae Signal

A lot of engineering practice shows that, during the construction and operation of rock mass projects, in addition to the static load, the rock is more subjected to cyclic load. Constant amplitude cyclic load is one of the simpler cyclic loading methods. The damage of rocks gradually accumulates under the action of periodic cyclic load, and finally, fatigue damage occurs, which affects the stability of the project. Therefore, it is necessary to study the mechanical properties of the rock under the action of constant amplitude cyclic load. Acoustic emission (AE) parameters and resistivity are both sensitive to the damage process of the rock and can well describe the damage evolution law of the rock. Under the action of constant amplitude cyclic loading, different loading conditions, different state specimens, and so on, factors will make a big difference to the AE signal and resistivity, such as the difference in stress amplitude, loading rate, and saturation. Therefore, in this paper, the typical sandstone in the Chongqing area is taken as the research object, the AE characteristics and resistivity characteristics of sandstone under different test conditions such as different stress amplitude, different loading frequency, and different saturation are tested, and the evolution of AE is found. It also has a three-stage rule: in the initial stage, the deformation is faster and the AE signal is strong; in the constant velocity stage, the deformation develops slowly and the AE signal is also stable; in the acceleration stage, the deformation develops sharply and the AE signal also becomes more intense. With the increase of cyclic loading stress amplitude, or the decrease of cyclic loading frequency, or the decrease of rock sample saturation, the acoustic emission signal generated in each cycle will be stronger. The resistivity as a whole shows a rapid decline in the loading phase and a rapid rebound in the unloading phase. The changes in resistivity at different stress amplitudes show differences in the first few cycles; the overall change trend of resistivity at different frequencies is consistent, but the rate of change increases with decreasing frequency, and the variation trend of resistivity is very different under different saturation.

scholarly journals Gas face seal status estimation based on acoustic emission monitoring and support vector machine regression

2020 ◽  
Vol 12 (5) ◽  
pp. 168781402092132
Author(s):  
Yuan Yin ◽  
Xiangfeng Liu ◽  
Weifeng Huang ◽  
Ying Liu ◽  
Songtao Hu
Keyword(s):  
Support Vector Machine ◽  
Acoustic Emission ◽  
Cross Validation ◽  
Acoustic Emissions ◽  
Support Vector ◽  
Support Vector Machine Regression ◽  
Eccentric Load ◽  
Acoustic Emission Monitoring ◽  
Emission Monitoring ◽  
Face Seals

The difficulty of knowing the real-time status of gas face seals is the main cause of common problems, including sudden failure, ineffective diagnosis, and unpredictability of service life. This study analyzed the acoustic emission signals generated from experiments, uncovering their features in terms of the frequency distribution, periodic fluctuations, and the behaviors during different operation phases. A new vectorization procedure was designed according to the knowledge of informative acoustic emission features. Based on the vectorization procedure, a support vector machine regression method was applied to develop models predicting the eccentric load on the stator of the seal. Cross-validation was conducted to evaluate the regression performance and search for a proper kernel scale. This study found the informative features of acoustic emissions at different timescales and during different seal operation phases, and particularly the great informative potential of certain segments of the starting and stopping phases. The vectorization and support vector machine regression were shown to be effective in estimating the loads in experiments with cross-validation. Thus, a method for estimating the status of gas face seals based on acoustic emission monitoring was established.

scholarly journals Experimental investigation of pretensioned bolts under cyclic loading: Damage assessment using acoustic emission

2019 ◽  
Vol 15 (5) ◽  
pp. 155014771984935 ◽  
Author(s):  
Tieliang An ◽  
Xigui Zheng ◽  
Dengxing Zhu ◽  
Deyu Qian ◽  
Yu Guo ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Cyclic Load ◽  
Loading Path ◽  
Loading Frequency ◽  
Damage Factor ◽  
Acoustic Emission Energy ◽  
Pull Out ◽  
Anchorage System ◽  
The Relationship

Understanding the acoustic emission effects on bolts under cyclic loading is of great significance for the support of roadways. The presented research focuses on the acoustic emission characteristics of bolts under cyclic loading. The following main conclusions were drawn: (1) With a higher loading frequency, the acoustic emission counts rate increases, while the total energy released in a given cyclic loading path decreases. (2) A fitting formula is established according to the relationship between the tension amplitude and cumulative acoustic emission counts, which can analyze the tension magnitude level of the cyclic load. (3) A damage factor for a cyclic load is proposed based on the acoustic emission counts generated during the cyclic and monotonic loading process that can analyze the degree of damage to the anchorage system caused by the cyclic load. (4) Based on the spatial distribution of the acoustic emission orientation points and the acoustic emission energy generated during the pull-out process, the acoustic emission damage evolution process of the anchorage specimens is deduced, and the mechanism of the high stability of the pretension anchorage system after cyclic loading is analyzed. The above conclusions may provide some experimental references for the application of acoustic emission technology in bolts supporting roadways.

Acoustic emission monitoring for bond integrity evaluation of reinforced concrete under pull-out tests

2016 ◽  
Vol 20 (9) ◽  
pp. 1390-1405 ◽  
Author(s):  
Ahmed A Abouhussien ◽  
Assem AA Hassan
Keyword(s):  
Acoustic Emission ◽  
Reinforced Concrete ◽  
Acoustic Emission Signal ◽  
Concrete Structures ◽  
Signal Strength ◽  
Concrete Cover ◽  
Reinforced Concrete Structures ◽  
Bond Behavior ◽  
Emission Signal ◽  
Pull Out

This article presents the results of an experimental investigation on the application of acoustic emission technique for monitoring the steel-to-concrete bond integrity of reinforced concrete structures. A series of direct pull-out tests were performed on 54 reinforced concrete unconfined prism samples with variable rebar diameter (10, 20, and 35 mm), embedded length (50, 100, and 200 mm), and concrete cover (20, 30, and 40 mm). The samples were tested under incrementally increasing monotonic loading while being continuously monitored via attached acoustic emission sensors. These sensors were utilized to acquire different acoustic emission signal parameters emitted throughout the tests until failure. Also, an acoustic emission intensity analysis was implemented on acoustic emission signal strength data to quantify the damage resulting from loss of bond in all tested specimens. This analysis employed the signal strength of all recorded acoustic emission hits to develop two additional parameters: historic index ( H ( t)) and severity ( Sr). The results of bond behavior, mode of failure, and free end slip were compared with the recorded acoustic emission data. The results showed that the cumulative number of hits, cumulative signal strength, H ( t), and Sr had a good correlation with different stages of bond damage from de-bonding/micro-cracking until bond splitting failure and bar slippage, which caused cover cracking or delamination. The analysis of cumulative signal strength and H ( t) curves enabled early identification of two progressive stages of bond degradation (micro-cracking and macro-cracking) and recognized the various modes of failure of the tested specimens. The variations of bar diameter, concrete cover, and embedded length yielded significant impacts on both the bond behavior and acoustic emission activities. The results also presented developed intensity classification charts, based on H ( t) and Sr, to assess the bond integrity and to quantify the bond deterioration (micro-cracking, macro-cracking, and rebar slip) in reinforced concrete structures.

scholarly journals Investigation of Bonding Behavior of FRP and Steel Bars in Self-Compacting Concrete Structures Using Acoustic Emission Method

Sensors ◽  
2019 ◽  
Vol 19 (1) ◽  
pp. 159 ◽  
Author(s):  
Bo Di ◽  
Jingkai Wang ◽  
Haotian Li ◽  
Jinhang Zheng ◽  
Yu Zheng ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Self Compacting Concrete ◽  
Fiber Volume ◽  
Pull Out ◽  
Steel Bar ◽  
Initial Location ◽  
Steel Bars ◽  
Ae Signal ◽  
Ae Location ◽  
Debonding Process

To extend understanding of the bonding behavior of fiber reinforced polymer (FRP) and steel bars in self-compacting concrete (SCC), an experimental series consisting of 36 direct pull-out tests monitored by acoustic emission (AE) were performed in this paper. The test variables involved rebar type, bar diameter, embedded length, and polypropylene (PP) fiber volume content. For each test, the pull-out force and free end slip were continuously measured and compared with the corresponding AE signals. It was found that the proposed AE method was effective in detecting the debonding process between the FRP/steel bars and the hosting concrete. The AE signal strength exhibited a good correlation with the actual bond stress-slip relationship measured in each specimen. Based on the AE location technique, the invisible non-uniform distribution of bonding stress along the bar was further revealed, the initial location of damage and the debonding process were captured. Additionally, the contribution of bar-to-concrete load-bearing mechanism (chemical adhesion, friction, and mechanical interlocking) to sustain the pull-out force was effectively clarified by studying the collected signals in the frequency domain of AE methods. The experimental results demonstrate that the proposed AE method has potential to detect the debonding damage of FRP/steel bar reinforced SCC structures accurately.

Correlation Between Acoustic Emission and Wear of Multi-Layer Ceramic Coated Carbide Tools

1997 ◽  
Vol 119 (2) ◽  
pp. 238-246 ◽  
Author(s):  
S.-S. Cho ◽  
K. Komvopoulos
Keyword(s):  
Acoustic Emission ◽  
Cutting Speed ◽  
Shear Zones ◽  
Machining Process ◽  
Contact Friction ◽  
Depth Of Cut ◽  
Near Surface ◽  
Pull Out ◽  
Ae Signal ◽  
Coated Carbide

Acoustic emission (AE) was used to monitor the machining process and tool condition during turning of AISI 4340 steel with uncoated, two-layer (TiC/Al2O3) coated, and three-layer (TiC/Al2O3/TiN) coated cemented WC-Co tools. The experiments were performed at four different feedrates and constant cutting speed and depth of cut. The variation of the AE signal with cutting time is interpreted in light of the dominant mechanisms, rates, and patterns of wear and the contact friction conditions at the tool/workpiece and tool/chip interfaces. Correlations between intrinsic frequencies and AE sources are identified by examining the root-mean-square, dominant amplitude, type, and count rate of the AE signals. It is shown that AE frequencies in the range of 50–100 kHz are primarily due to plastic deformation in the near-surface tool regions and the primary, secondary, and tertiary shear zones of the workpiece, whereas cracking leading to coating delamination and WC grain pull-out generates frequencies in the range of 170–200 kHz. The tool life estimated from the root-meansquare of the AE signal is shown to be in good agreement with that determined from measurements of the maximum wearland width on the tool nose. The obtained results demonstrate that AE is an effective technique for in-process wear monitoring and wear mechanism identification of multi-layer ceramic coated tools.

Gas Turbine Condition Monitoring Using Acoustic Emission Signals

2019 ◽  
Vol 2 (3) ◽  
Author(s):  
S. Shahkar ◽  
K. Khorasani
Keyword(s):  
Acoustic Emission ◽  
Gas Turbine ◽  
Condition Monitoring ◽  
Gas Turbines ◽  
Acoustic Emissions ◽  
Time Instant ◽  
Rotary Machinery ◽  
Ae Signal ◽  
Reliable Classification ◽  
Ae Signals

Acoustic emission (AE) signals are recognized as complementary measures for detecting incipient faults and condition monitoring in rotary machinery due to their containment of sources of potential fault energy. However, determining the potential sources of faults cannot be easily realized due to the non-stationarity of AE signals. Available techniques that are capable of evoking instantaneous characteristics of a particular AE signal cannot optimally perform in a sense that there is no guarantee that these characteristics (hereinafter referred to as the “features”) remain constant when another AE signal is obtained from the system, albeit operating under the same machine condition at a different time instant. This paper provides a theoretical framework for developing a highly reliable classification and detection methodology for gas turbine condition monitoring based on AE signals. Mathematical results obtained in this paper are evaluated and validated by using actual gas turbines that are operating in power generating plants, to demonstrate the practicality and simplicity of our methodologies. Emphasis is given to acoustic emissions of similar brand and sized gas turbine turbomachinery under different health conditions and/or aging characteristics.

Acoustic Emission Monitoring of Nanoindentation-Induced Slip and Twinning in Sapphire

2002 ◽  
Vol 750 ◽  
Author(s):  
Natalia I. Tymiak ◽  
Antanas Daugela ◽  
Thomas J. Wyrobek ◽  
Oden L. Warren
Keyword(s):  
Acoustic Emission ◽  
Yield Point ◽  
Loading Rate ◽  
Activity Detection ◽  
Emission Monitoring ◽  
Rate Effects ◽  
Ae Signal ◽  
Sapphire Single Crystal ◽  
Ae Signals ◽  
Crystallographic Orientations

ABSTRACTMonitoring with an Acoustic Emission (AE) sensor integrated into an indenter tip was utilized for the evaluation of the earliest stages of indentation-induced plasticity in sapphire single crystal. The evaluated surfaces included basal (C), rhombohedral (R) and two different prismatic orientations (A and M). The differences between the mechanisms of the initial stages of plasticity for the various crystallographic orientations were reflected in the following aspects of AE activity: detection of a specific type of AE waveform that correlated to the presence of linear surface features near the indentation impressions; AE signal associated with the yield point, consisting either of one or two distinct waveforms; and presence or absence of AE signals after the yield point. Moreover, analysis of AE activity revealed loading rate effects on the yield point mechanism for the M plane. The possibility of plasticity onset mechanisms involving both slip and twinning is discussed.

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