Three Stages of Composite Specimen Destruction in Static Failure

Abstract The paper presents the results of standard specimen fracture made of anisotropic carbon fiber plastic with an epoxy matrix. Static stepwise loading of the specimen was carried out on an Instron 8801 testing machine to determine the characteristics of ductile fracture G1C in the first mode in accordance with ASTM D5528. During loading, the parameters of acoustic emission (AE) signals, such as AE impulse amplitudes and their energy were synchronously recorded. At the same time, the magnitude of the opening and the growth of the crack initiated by the artificial cut at the end of the specimen were recorded. According to the analysis of the acoustic emission signals, three zones with different G1C behaviour were identified: initial crack propagation, its stationary growth and accelerated fracture of the specimen. The zonal character of the change in the acoustic emission signals made it possible to determine the energy of the acoustic emission signals as diagnostic evidence for the onset of rapid destruction of the specimen. The amplitude of the AE-signals in the zones, however, remained constant. Online monitoring of changes in the energy of acoustic emission signals will prevent the onset of rapid destruction of an object in places of its deformations. The paper does not aim at defining G1C as usual. It presents the investigation of the fracture stages for a composite material using an acoustic emission method.

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Real-Time Monitoring of Degradation of Zirconia Ceramic by Acoustic Emission

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.433-435.816 ◽

2013 ◽

Vol 433-435 ◽

pp. 816-820 ◽

Cited By ~ 2

Author(s):

Kai Ge Wu ◽

Chan Yang Choe ◽

Seung Mi Lee ◽

Ji Ae Yoo ◽

Chang Yong Hyun ◽

...

Keyword(s):

Acoustic Emission ◽

Low Temperature ◽

Time Domain ◽

Zirconia Ceramic ◽

X Ray Diffraction ◽

Zirconia Ceramics ◽

X Ray ◽

Ae Signal ◽

Three Stages ◽

Ae Signals

Acoustic emission (AE) technique was employed to monitor the low temperature degradation (LTD) behavior of a zirconia ceramic, which was carried out in air at 200°C. AE signals, typical waveform of which exhibited as pulse-like type, were detected during LTD and increased with the duration time of LTD. The AE signal of accumulative counts number and amplitude in time domain exhibited a roughly sigmoid variation including three stages, which reflect approximately the evolution of LTD. The AE findings were supported by X-ray diffraction (XRD) examination. It was suggested that AE technique can be used to monitor the mechanism of LTD of zirconia ceramics.

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Study on the Mechanical Behavior and Acoustic Emission Properties of Granite under Triaxial Compression

Geofluids ◽

10.1155/2021/3954097 ◽

2021 ◽

Vol 2021 ◽

pp. 1-17

Author(s):

Jiaqi Guo ◽

Pengfei Liu ◽

Junqi Fan ◽

Hengyuan Zhang

Keyword(s):

Acoustic Emission ◽

Crack Initiation ◽

Triaxial Compression ◽

Testing Machine ◽

Confining Pressure ◽

High Energy ◽

Granite Sample ◽

Initiation Point ◽

Granite Samples ◽

Ae Signals

To study the rock mechanical behaviors and damage process mechanism of granite samples under triaxial stress, conventional triaxial compression tests were carried out on an RMT-150B rock mechanics testing machine and acoustic emission detector. The test results show that the strength of the granite sample has a good linear relationship with the confining pressure, the cohesion force c of the granite samples is 29.37 MPa, and the internal friction angle is 54.23° by calculation based on the Mohr-Coulomb strength criterion. The larger the initial confining pressure of the rock sample is, the larger the crack initiation stress ( σ ci ) and dilatancy stress ( σ cd ) of the granite specimen are, the larger the energy values at the crack initiation point and dilatancy point are, and the larger the peak energy storage and energy release rate at the failure are. In the case of a small initial confining pressure, the AE ringdowning counts and the cumulative AE ringing counts increase to their maximum instantaneously at the peak stress point, and the damage of the sample develops rapidly. While the initial confining pressure is high, the AE ringing counts and the cumulative AE ringing counts of the granite specimens increase evenly, and the deformation damage of the granite specimens is slow. Before the crack initiation point, AE signals are mainly low-energy and low-frequency friction-type AE events, while after the dilatation point, AE signals of samples are mainly high-frequency and high-energy fracture-type AE events. The failure mode of granite samples judged by acoustic emission parameters according to the distribution of characteristic values of AE parameters RA and AF is consistent with the reality. The AE b value of the granite sample is large when the confining pressure is low, and there will be a sudden drop, the decrease time is late, and the decrease rate is large. Under the same stress level, the larger the confining pressure is, the larger the damage variable D is.

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Analysis of Acoustic Emission (AE) Signals for Quality Monitoring of Laser Lap Microwelding

Applied Sciences ◽

10.3390/app11157045 ◽

2021 ◽

Vol 11 (15) ◽

pp. 7045

Author(s):

Ming-Chyuan Lu ◽

Shean-Juinn Chiou ◽

Bo-Si Kuo ◽

Ming-Zong Chen

Keyword(s):

Stainless Steel ◽

Acoustic Emission ◽

Frequency Domain ◽

Monitoring System ◽

Welding Quality ◽

Steel Sheets ◽

Signal Features ◽

Ae Signal ◽

Laser Microwelding ◽

Ae Signals

In this study, the correlation between welding quality and features of acoustic emission (AE) signals collected during laser microwelding of stainless-steel sheets was analyzed. The performance of selected AE features for detecting low joint bonding strength was tested using a developed monitoring system. To obtain the AE signal for analysis and develop the monitoring system, lap welding experiments were conducted on a laser microwelding platform with an attached AE sensor. A gap between the two layers of stainless-steel sheets was simulated using clamp force, a pressing bar, and a thin piece of paper. After the collection of raw signals from the AE sensor, the correlations of welding quality with the time and frequency domain features of the AE signals were analyzed by segmenting the signals into ten 1 ms intervals. After selection of appropriate AE signal features based on a scatter index, a hidden Markov model (HMM) classifier was employed to evaluate the performance of the selected features. Three AE signal features, namely the root mean square (RMS) of the AE signal, gradient of the first 1 ms of AE signals, and 300 kHz frequency feature, were closely related to the quality variation caused by the gap between the two layers of stainless-steel sheets. Classification accuracy of 100% was obtained using the HMM classifier with the gradient of the signal from the first 1 ms interval and with the combination of the 300 kHz frequency domain signal and the RMS of the signal from the first 1 ms interval.

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Acoustic Emission Testing and Ib-Value Analysis of Ultraviolet Light-Irradiated Fiber Composites

Applied Sciences ◽

10.3390/app11146550 ◽

2021 ◽

Vol 11 (14) ◽

pp. 6550

Author(s):

Doyun Jung ◽

Wonjin Na

Keyword(s):

Acoustic Emission ◽

Irradiation Time ◽

Tensile Load ◽

Failure Behavior ◽

Value Analysis ◽

Emission Testing ◽

Final Failure ◽

Acoustic Emission Testing ◽

Woven Glass Fiber ◽

Ae Signals

The failure behavior of composites under ultraviolet (UV) irradiation was investigated by acoustic emission (AE) testing and Ib-value analysis. AE signals were acquired from woven glass fiber/epoxy specimens tested under tensile load. Cracks initiated earlier in UV-irradiated specimens, with a higher crack growth rate in comparison to the pristine specimen. In the UV-degraded specimen, a serrated fracture surface appeared due to surface hardening and damaged interfaces. All specimens displayed a linearly decreasing trend in Ib-values with an increasing irradiation time, reaching the same value at final failure even when the starting values were different.

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Acoustic Emission Monitoring of Leaks in Pipes for Transport of Liquid and Gaseous Media: A Model Experiment

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.13-14.351 ◽

2006 ◽

Vol 13-14 ◽

pp. 351-356 ◽

Cited By ~ 12

Author(s):

Andreas J. Brunner ◽

Michel Barbezat

Keyword(s):

Acoustic Emission ◽

Model Experiment ◽

Structural Integrity ◽

Fiber Composite ◽

Leak Testing ◽

Pipe Segment ◽

Potential Applications ◽

Gaseous Media ◽

The Media ◽

Ae Signals

In order to explore potential applications for Active Fiber Composite (AFC) elements made from piezoelectric fibers for structural integrity monitoring, a model experiment for leak testing on pipe segments has been designed. A pipe segment made of aluminum with a diameter of 60 mm has been operated with gaseous (compressed air) and liquid media (water) for a range of operating pressures (between about 5 and 8 bar). Artificial leaks of various sizes (diameter) have been introduced. In the preliminary experiments presented here, commercial Acoustic Emission (AE) sensors have been used instead of the AFC elements. AE sensors mounted on waveguides in three different locations have monitored the flow of the media with and without leaks. AE signals and AE waveforms have been recorded and analysed for media flow with pressures ranging from about 5 to about 8 bar. The experiments to date show distinct differences in the FFT spectra depending on whether a leak is present or not.

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Acoustic Emission and K-S Metric Entropy as Methods for Determining Mechanical Properties of Composite Materials

Sensors ◽

10.3390/s21010145 ◽

2020 ◽

Vol 21 (1) ◽

pp. 145

Author(s):

Lesław Kyzioł ◽

Katarzyna Panasiuk ◽

Grzegorz Hajdukiewicz ◽

Krzysztof Dudzik

Keyword(s):

Mechanical Properties ◽

Acoustic Emission ◽

Composite Material ◽

Composite Materials ◽

Testing Machine ◽

Measurement Data ◽

Entropy Method ◽

Displacement Sensor ◽

Metric Entropy ◽

Plastic Phase

Due to the unique properties of polymer composites, these materials are used in many industries, including shipbuilding (hulls of boats, yachts, motorboats, cutters, ship and cooling doors, pontoons and floats, torpedo tubes and missiles, protective shields, antenna masts, radar shields, and antennas, etc.). Modern measurement methods and tools allow to determine the properties of the composite material, already during its design. The article presents the use of the method of acoustic emission and Kolmogorov-Sinai (K-S) metric entropy to determine the mechanical properties of composites. The tested materials were polyester-glass laminate without additives and with a 10% content of polyester-glass waste. The changes taking place in the composite material during loading were visualized using a piezoelectric sensor used in the acoustic emission method. Thanks to the analysis of the RMS parameter (root mean square of the acoustic emission signal), it is possible to determine the range of stresses at which significant changes occur in the material in terms of its use as a construction material. In the K-S entropy method, an important measuring tool is the extensometer, namely the displacement sensor built into it. The results obtained during the static tensile test with the use of an extensometer allow them to be used to calculate the K-S metric entropy. Many materials, including composite materials, do not have a yield point. In principle, there are no methods for determining the transition of a material from elastic to plastic phase. The authors showed that, with the use of a modern testing machine and very high-quality instrumentation to record measurement data using the Kolmogorov-Sinai (K-S) metric entropy method and the acoustic emission (AE) method, it is possible to determine the material transition from elastic to plastic phase. Determining the yield strength of composite materials is extremely important information when designing a structure.

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A Principal Component Analysis of Acoustic Emission Signals from a Landing Gear Component

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.13-14.41 ◽

2008 ◽

Vol 13-14 ◽

pp. 41-47 ◽

Cited By ~ 6

Author(s):

Rhys Pullin ◽

Mark J. Eaton ◽

James J. Hensman ◽

Karen M. Holford ◽

Keith Worden ◽

...

Keyword(s):

Principal Component Analysis ◽

Acoustic Emission ◽

Background Noise ◽

Principal Component ◽

Component Analysis ◽

Landing Gear ◽

Fracture Detection ◽

Artificial Fracture ◽

High Level ◽

Ae Signals

This work forms part of a larger investigation into fracture detection using acoustic emission (AE) during landing gear airworthiness testing. It focuses on the use of principal component analysis (PCA) to differentiate between fracture signals and high levels of background noise. An artificial acoustic emission (AE) fracture source was developed and additionally five sources were used to generate differing AE signals. Signals were recorded from all six artificial sources in a real landing gear component subject to no load. Further to this, artificial fracture signals were recorded in the same component under airworthiness test load conditions. Principal component analysis (PCA) was used to automatically differentiate between AE signals from different source types. Furthermore, successful separation of artificial fracture signals from a very high level of background noise was achieved. The presence of a load was observed to affect the ultrasonic propagation of AE signals.

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Grinding Acoustic Emission Classification in Terms of Mechanical Behaviours

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.329.15 ◽

2007 ◽

Vol 329 ◽

pp. 15-20 ◽

Cited By ~ 2

Author(s):

Xun Chen ◽

James Griffin

Keyword(s):

Neural Network ◽

Acoustic Emission ◽

Material Removal ◽

Grinding Process ◽

Short Time Fourier Transform ◽

Fundamental Investigation ◽

Mechanical Behaviours ◽

Wavelets Transform ◽

Short Time ◽

Ae Signals

The material removal in grinding involves rubbing, ploughing and cutting. For grinding process monitoring, it is important to identify the effects of these different phenomena experienced during grinding. A fundamental investigation has been made with single grit cutting tests. Acoustic Emission (AE) signals would give the information relating to the groove profile in terms of material removal and deformation. A combination of filters, Short-Time Fourier Transform (STFT), Wavelets Transform (WT), statistical windowing of the WT with the kurtosis, variance, skew, mean and time constant measurements provided the principle components for classifying the different grinding phenomena. Identification of different grinding phenomena was achieved from the principle components being trained and tested against a Neural Network (NN) representation.

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Study on Characteristics of Ultrasonic Velocity for the Concrete under Stress

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.438-439.220 ◽

2013 ◽

Vol 438-439 ◽

pp. 220-223 ◽

Cited By ~ 1

Author(s):

Ling Zhang ◽

Chun Ling Yan

Keyword(s):

Ultimate Strength ◽

Ultrasonic Velocity ◽

Ultrasound Examination ◽

Testing Machine ◽

Strength Level ◽

Growth Trend ◽

Universal Testing Machine ◽

Universal Testing ◽

Three Stages ◽

The Relationship

Cube concrete (150×150×150mm) of five ages (7, 14, 21, 28 and 35 days) under different stress conducted the ultrasound examination by non-metallic detector and universal testing machine. The results show that the relationship curve of the stress and the ultrasonic velocity can be divided into three stages, the smooth straight stage, the linear deceleration stage and the attenuation destruction stage from the load beginning to the ultimate strength for the same age. There is a growing trend about the ultrasonic velocity with the increase of the age to concrete samples of C10 and C20 in the same loading; however, the overall growth trend of the velocity is not obvious to concrete samples of C30, C35, C40 and C45. It also shows that the relationship curve of strength level and the velocity can be divided into two distinct stages, the sharply increasing stage (C10-C30) and the fluctuating stage (C30-C45). Simultaneously, the paper further illustrates and explains the reasons to appear these stages and the phenomena.

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