scholarly journals Mechanical Properties of Thin-Ply Composites Based on Acoustic Emission Technology

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 913
Author(s):  
Kaidong Zheng ◽  
Dongfeng Cao ◽  
Haixiao Hu ◽  
Yundong Ji ◽  
Shuxin Li
Keyword(s):  
Acoustic Emission ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Operating Conditions ◽  
Fiber Failure ◽  
Crack Propagation Resistance ◽  
Evolution Characteristics ◽  
Damage Process ◽  
Laminate Thickness ◽  
Ae Signals

Compared with standard-ply composites, thin-ply composites exhibit a superior mechanical performance under various operating conditions due to their positive size effects. Thin-ply laminate failure modes, including matrix initial damage (MID), matrix failure (MF), and fiber failure (FF), have been distinguished through a systematic acoustic emission (AE) signals analysis combined with scanning electron microscopy (SEM). First, the characteristic frequencies of various failure modes are identified based on unidirectional laminates ([90] 68 and [0] 68). Then, according to the identified frequencies corresponding to distinctive damage modes, four lay-up sequences (02[[90m/0m]ns]02, m = 1, 2, 4, 8, n × m = 16) with a constant total thickness are designed, and the effects of the number of identical plies in the laminate thickness on the damage evolution characteristics and the damage process under uniaxial tension loads are dynamically monitored. The obtained results indicate that the characteristic frequency ranges for MID, MF, and FF are identified as 0–85 kHz, 165–260 kHz, and 261–304 kHz, respectively. The thickness of identical plies has a significant effect on onset damage. With the decrease of the number of identical plies (i.e., m in the stacking sequences), the thin-ply laminates exhibit the initiation of damage suppression effects and crack propagation resistance.

scholarly journals Prefabricated Urban Underground Utility Tunnels: A Case Study on Mechanical Behaviour with Strain Monitoring and Numerical Simulation

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Yonggang Xiao ◽  
Jubing Zhang ◽  
Jie Cao ◽  
Changhong Li
Keyword(s):  
Numerical Simulation ◽  
Working Conditions ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Low Cost ◽  
Side Wall ◽  
Operating Conditions ◽  
Land Occupation ◽  
Depth Analysis ◽  
Simulation Results

The prefabricated urban utility tunnels (UUTs) have many advantages such as short construction period, low cost, high quality, and small land occupation. However, there is still a lack of in-depth analysis of the mechanical performance of the prefabricated urban utility tunnel (UUT) structure with bolted connections under different working conditions. In this paper, the force performance of a prefabricated UUT in Tongzhou District, Beijing, was studied under different working conditions using two methods: field monitoring and numerical simulation. The multichannel strain monitor was used for monitoring, and the internal wall concrete and bolt strain change data under the two conditions of installation and backfill were obtained. Combined with the construction process of the UUTs, a three-dimensional numerical model was established by COMSOL, where the build-in bolt assembly was used to simulate the longitudinal connection of the tunnel. The simulation results were compared with the measured data to verify the rationality of the computational model. The simulation results showed that the concrete and bolts on the inner wall of the tunnel work well under the two conditions of installation and backfilling; The deformation of the top plate of the prefabricated tunnel was approximately parabolic, with the largest vertical displacement (0.37 mm) in the middle and the most sensitive to the vertical load in the central part of the roof. The central portion of the side wall had the largest displacement (0.17 mm) in the inner concave. The tensile stress of bolt 3 increased the most (30.75 MPa) but was still much smaller than the yield strength of the bolt. The concrete and bolts of the UUT were found to work well through force analysis under operating conditions. In conclusion, analysis of structural forces and deformation failure modes will help design engineers understand the basic mechanisms and select the appropriate UUT structure.

Frequency Characteristics of Acoustic Emission Signals from Cementitious Wasteforms with Encapsulated Al

2006 ◽  
Vol 985 ◽  
Author(s):  
Lyubka Spasova ◽  
Michael I. Ojovan
Keyword(s):  
Acoustic Emission ◽  
Power Spectrum ◽  
Acoustic Waves ◽  
Mechanical Performance ◽  
Frequency Characteristics ◽  
Cement Matrix ◽  
Intrinsic Frequency ◽  
Cement System ◽  
Primary Frequency ◽  
Ae Signals

AbstractAcoustic emission (AE) signals were continuously recorded and their intrinsic frequency characteristics examined in order to evaluate the mechanical performance of cementitious wasteform with encapsulated Al waste. The primary frequency in the power spectrum and its range of intensity for the detected acoustic waves were potentially related with appearance of different micromechanical events caused by Al corrosion within the encapsulating cement system. In addition the process of cement matrix hardening has been shown as a source of AE signals characterised with essentially higher primary frequency (above 2 MHz) compared with those due to Al corrosion development (below 40 kHz) and cement cracking (above 100 kHz).

Acoustic Emission Characteristics of Rock Failure under Uniaxial Loading

2011 ◽  
Vol 378-379 ◽  
pp. 43-46 ◽  
Author(s):  
Tao Xie ◽  
Qing Hui Jiang ◽  
Rui Chen ◽  
Wei Zhang
Keyword(s):  
Acoustic Emission ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Progressive Failure ◽  
Failure Process ◽  
Testing Machine ◽  
Rock Failure ◽  
Rock Failure Process ◽  
State Variation ◽  
Acoustic Emission Test

With RMT-150C rock testing machine and AEWIN E1.86 DISP acoustic emission system applied, the acoustic emission test was accomplished with two kinds of rock samples including marble and granite under uniaxial compression. Cyclic loading and continuous loading were used through the experiment, and the mechanical performance and acoustic emission (AE) characteristics were obtained during the process of rock progressive failure. Details related to the relationship between amount of AE and stress-strain was given in this paper. A comparison between marble and granite was made as well following the general AE law, on the basis of which, the failure mechanism of rock mass was investigated. Finally, some conclusions can be summarized as follows:(1) AE activity features are different with stress state variation in rock failure process;(2) loading patterns make a direct impact on the failure process thereby affecting AE activities;(3)AE activities are various basing on the different types of rocks, structures and failure modes.

scholarly journals A Reliable Acoustic EMISSION Based Technique for the Detection of a Small Leak in a Pipeline System

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1472 ◽  
Author(s):  
Thang Bui Quy ◽  
Sohaib Muhammad ◽  
Jong-Myon Kim
Keyword(s):  
Acoustic Emission ◽  
Nearest Neighbor ◽  
Transformation Method ◽  
Operating Conditions ◽  
Training Data ◽  
Pipeline System ◽  
K Nearest Neighbor ◽  
Knn Classifier ◽  
Water Pipelines ◽  
Ae Signals

This paper proposes a reliable leak detection method for water pipelines under different operating conditions. This approach segments acoustic emission (AE) signals into short frames based on the Hanning window, with an overlap of 50%. After segmentation from each frame, an intermediate quantity, which contains the symptoms of a leak and keeps its characteristic adequately stable even when the environmental conditions change, is calculated. Finally, a k-nearest neighbor (KNN) classifier is trained using features extracted from the transformed signals to identify leaks in the pipeline. Experiments are conducted under different conditions to confirm the effectiveness of the proposed method. The results of the study indicate that this method offers better quality and more reliability than using features extracted directly from the AE signals to train the KNN classifier. Moreover, the proposed method requires less training data than existing techniques. The transformation method is highly accurate and works well even when only a small amount of data is used to train the classifier, whereas the direct AE-based method returns misclassifications in some cases. In addition, robustness is also tested by adding Gaussian noise to the AE signals. The proposed method is more resistant to noise than the direct AE-based method.

NON-DESTRUCTIVE EVALUATION AND STRENGTH CHARACTERISTICS OF CFRP WITH HEAT DAMAGE

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4285-4290 ◽  
Author(s):  
JIN WOOK KIM ◽  
YOUNG UN KIM ◽  
CHANG KWON MOON ◽  
SEOK HWAN AHN ◽  
KI WOO NAM
Keyword(s):  
Acoustic Emission ◽  
Structural Integrity ◽  
Matrix Cracking ◽  
Fracture Mechanisms ◽  
Heat Damage ◽  
Time Frequency ◽  
Reinforced Plastic ◽  
Damage Process ◽  
Distinct Frequency ◽  
Ae Signals

In this study, the heat-damage process of a carbon fiber reinforced plastic (CFRP) under monotonic tensile loading was characterized by acoustic emission. Additionally, epoxy specimens and prepreg specimens were used to determine the characteristics of acoustic emission (AE) signals of epoxy and fiber, respectively. The AE characteristics of CFRP showed three types of distinct frequency regions. Time-frequency analysis methods were employed for the analysis of fracture mechanisms in CFRP such as matrix cracking, debonding and fiber fracture. To evaluate the cumulative counts of AE signals, it seems that the results can be applied usefully to guarantee structural integrity and/or to the survey of destruction of the structure with heat-damage, that was made to the composite materials.

scholarly journals Damage Evolution Analysis in a “Spaghetti” Bridge Model Using the Acoustic Emission Technique

2021 ◽  
Vol 11 (6) ◽  
pp. 2718
Author(s):  
Boris Nahuel Rojo Tanzi ◽  
Mario Sobczyk ◽  
Tiago Becker ◽  
Luis Alberto Segovia González ◽  
Sabrina Vantadori ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Geometric Distribution ◽  
Frequency Variation ◽  
Loading Test ◽  
Evolution Analysis ◽  
Bridge Model ◽  
Theoretical Predictions ◽  
Damage Process ◽  
Damage Processes ◽  
Ae Signals

This paper applies the Acoustic Emission (AE) Technique to analyze the damage process in a one-meter span bridge model that was built from spaghetti sticks during a loading test. The AE signals are analyzed in terms of four coefficients that are evaluated as predictors of structure failure, with frequency variation appearing to be the strongest indicator of instability. The AE data are also compared to theoretical predictions that are given by the Bundle Model, confirming that underlying general patterns in damage processes are highly influenced by the geometric distribution of the structure and the loading pattern that is applied to it.

Critical Behaviour in Concrete Structures and Damage Localization by Acoustic Emission

2006 ◽  
Vol 312 ◽  
pp. 305-310 ◽  
Author(s):  
Alberto Carpinteri ◽  
Giuseppe Lacidogna ◽  
Gianni Niccolini
Keyword(s):  
Acoustic Emission ◽  
Concrete Fracture ◽  
Rc Structures ◽  
Size Dependent ◽  
Spatially Distributed ◽  
Damage Process ◽  
Non Destructive ◽  
Dependent Behaviour ◽  
Ae Signals ◽  
Fracture Processes

Extensive research and studies on concrete fracture and failure have shown that concrete should be viewed as a quasi-brittle material having a size-dependent behaviour. Numerous experimental techniques have been employed to evaluate fracture processes, and a number of modelling approaches have been developed to predict fracture behaviour. The non-destructive method based on the Acoustic Emission (AE) technique has proved highly effective, especially to check and measure the damage phenomena that take place inside a structure subjected to mechanical loading. In this paper an experimental investigation conducted on concrete and RC structures by means of the AE technique is described. The AE signals reflecting the release of energy taking place during the damage process were recorded and micro-cracking sources were localised by measuring time delays by means of spatially distributed AE sensors.

scholarly journals Flexural Characteristics Evaluation for Reinforced Concrete Affected by Steel Corrosion Based on an Acoustic Emission Technique

2019 ◽  
Vol 9 (8) ◽  
pp. 1640 ◽  
Author(s):  
Zhang ◽  
Tan ◽  
Wang ◽  
Cheng ◽  
Yang ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Reinforced Concrete ◽  
Failure Modes ◽  
Steel Corrosion ◽  
Test Method ◽  
Rc Beam ◽  
Acoustic Emission Technique ◽  
Statistical Parameters ◽  
Dense Distribution ◽  
Ae Signals

The purpose of this research is to utilize a more advanced test method for investigating the effect of steel corrosion on the flexural characteristics of a reinforced concrete (RC) beam on a microscopic cracking level. Firstly, over-reinforced RC beam specimens were prepared and corroded using an electrical accelerated steel corrosion setup in different ratios. Subsequently, bending and acoustic emission (AE) tests were performed on all the specimens to obtain their ultimate flexural loads, failure modes and AE signals. Furthermore, rise time/peak amplitude (R/A), ringing counts/duration (AF) and improved b (Ib) values, as the statistical parameters of AE signals, were calculated for indicating the transformation of RC specimens’ crack modes and failure modes under the effect of steel corrosion. Finally, the locations of AE events were obtained by localization technology and compared with the locations of concrete cracks (cracks map). The results revealed that the ultimate flexural load decreases with steel corrosion. The crack tends to transform from shear- to tensile-type along with the increase of the steel corrosion ratio. The trend of the Ib-value curve can reflect the formation and development of cracks; and the larger the duration of violent fluctuations in the Ib-value curve is, the larger the ultimate flexural load of the RC beam is. The region where the crack is located can be judged by the position where the relatively dense distribution of the AE events is.

scholarly journals Acoustic Emission Characteristics and Damage Evolution of Rock under Different Loading Modes

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3649
Author(s):  
Ersheng Zha ◽  
Ru Zhang ◽  
Zetian Zhang ◽  
Ting Ai ◽  
Li Ren ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Fracture Surface ◽  
Tensile Stress ◽  
Energy Release ◽  
Failure Modes ◽  
Failure Process ◽  
Tensile Tests ◽  
Single Fracture ◽  
Loading Modes ◽  
Ae Signals

To study the evolution of acoustic emission (AE) parameters and the differences in the fracturing and failure process of rocks under different loading modes, AE signals of marble were detected during uniaxial compression tests (UCTs), direct tensile tests (DTTs) and indirect tensile tests (ITTs) in this paper. Then, the temporal and spatial evolution of the AE parameters and damage development of rock under different loading modes were analyzed. The results showed that the sequence of total AE events and AE counts under different loading modes was UCT > DTT > ITT. In the DTT and ITT, the energy release of AE signals was concentrated at the peak stress and weakened rapidly afterward, whereas in the UCT, there were still a large number of AE signals accompanied by violent AE energy release during the postpeak stage. The generation mechanism of AE sources in rock and the corresponding failure modes were different under different loading modes. In the UCT, the multiple cleavage fractures were mainly caused by compression-induced fracturing. In the DTT, the single fracture surface was generated by tensile stress, whereas in the ITT, compressive-tensile stress was applied to the fracture surface. In addition, the stress levels at which the b-value and the spatial fractal dimension Ds of AE events decreased dramatically were consistent under the different loading modes, and the sequence was UCT < DTT < ITT. According to the changes in AE parameters during the whole process of rock deformation and failure, the first and second precursor points before failure were defined to distinguish the development of microfracture damage and failure processes in rocks under the different loading modes. The above results have certain significance for future studies on the monitoring of surrounding rock instability and failure prediction.

scholarly journals Failure Mode Analysis of Carbon Fiber Composite Laminates by Acoustic Emission Signals

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Xinye Liu ◽  
Xinyue Yao ◽  
Jinhui Cai ◽  
Jiusun Zeng ◽  
Wingkong Chiu
Keyword(s):  
Acoustic Emission ◽  
Composite Laminates ◽  
Failure Modes ◽  
Fiber Composite ◽  
Mode Analysis ◽  
Carbon Fiber Composite ◽  
Bending Tests ◽  
Stacking Order ◽  
Failure Mode Analysis ◽  
Ae Signals

Composite laminates have complex failure modes. In order to investigate the evolution of failure in the composite laminates, this paper performed an experimental study on four laminates with different layups using acoustic emission (AE) technique. Two different kinds of defects are imposed on the laminates, including a hole and a crack in the center. Tensile and bending tests are performed on the defective laminates and real-time AE signals are collected. By analyzing the spectrograms of the obtained AE signals and integrating with the dispersion curves, the evolution of failure modes for different laminates can be observed. The tests show that the defects cause multiple failure modes, which change gradually during the experiments. It is also revealed that laminates with different layups have different failure modes. More specifically, the stacking order of different plies has a greater impact on the occurrence of delamination and fiber fracture than matrix crack. The tentative research shows that there is great potential for improving the performance of the composite laminates by careful selection of ply layups.

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