Study on the Prediction Method for Brittle Failure of Hard Rock Based on Acoustic Emission Test

2012 ◽  
Vol 594-597 ◽  
pp. 376-379 ◽  
Author(s):  
S C. Xu ◽  
B R. Chen ◽  
C Y. Jin
Keyword(s):  
Acoustic Emission ◽  
Main Shock ◽  
Hard Rock ◽  
Emission Rate ◽  
Prediction Method ◽  
Triaxial Tests ◽  
True Triaxial ◽  
Acoustic Emission Test ◽  
Different Characteristics ◽  
Ae Signals

In this paper, a series of true triaxial tests indoor with acoustic emission mornitoring were conducted and the characteristics of acoustic emission rate and energy releasing rate in the section adjacent to failure were gained. According to the different characteristics of acoustic emission rate, we divided the events rate into three types which were main shock, foreshock-main shock and cluster shocks. And then, a prediction method for hard rock was put forward according to different events rate types based on the trends of AE signals in the section adjacent to failure for hard rock.

Classification of journal bearing friction states based on acoustic emission signals

2018 ◽  
Vol 85 (6) ◽  
pp. 434-442 ◽  
Author(s):  
Noushin Mokhtari ◽  
Clemens Gühmann
Keyword(s):  
Acoustic Emission ◽  
Time Domain ◽  
Journal Bearing ◽  
Prediction Method ◽  
Support Vector ◽  
Mechatronic Systems ◽  
Prediction Time ◽  
Ae Signals ◽  
Bearing Friction

Abstract For diagnosis and predictive maintenance of mechatronic systems, monitoring of bearings is essential. An important building block for this is the determination of the bearing friction condition. This paper deals with the possibility of monitoring different journal bearing friction states, such as mixed and fluid friction, and examines a new approach to distinguish between different friction intensities under several speed and load combinations based on feature extraction and feature selection methods applied on acoustic emission (AE) signals. The aim of this work is to identify separation effective features of AE signals to subsequently classify the journal bearing friction states. Furthermore, the acquired features give information about the mixed friction intensity, which is significant for remaining useful lifetime (RUL) prediction. Time domain features as well as features in the frequency domain have been investigated in this work. To increase the sensitivity of the extracted features the AE signals were transformed to the frequency-time-domain using continuous wavelet transform (CWT). Significant frequency bands are determined to separate different friction states more effective. A support vector machine (SVM) is used to classify the signals into three different friction classes. In the end the idea for an RUL prediction method by using the already determined information is given and explained.

Acoustic Emission Characteristics of Sericite Schist Coarse Aggregates under Consolidated Undrained Triaxial Tests

2013 ◽  
Vol 423-426 ◽  
pp. 909-913
Author(s):  
Lan Qiang Yang ◽  
Shang Lin Qin ◽  
Hui Gao ◽  
Shan Xiong Chen
Keyword(s):  
Acoustic Emission ◽  
Large Scale ◽  
Sliding Friction ◽  
Axial Strain ◽  
Confining Pressure ◽  
Rolling Friction ◽  
Triaxial Tests ◽  
Emission Characteristics ◽  
Coarse Aggregates ◽  
Ae Signals

In order to study the acoustic emission characteristics of coarse aggregates, improved of large-scale triaxial apparatus is used to do the consolidated undrained triaxial tests of sericite schist coarse aggregates, with the acoustic emission signals monitoring. The test results show that a large number of AE signals of sericite schist coarse aggregates are generated in the initial stage. Before the axial strain reach 10%, AE counts are relatively quiet. But after 10%, they become anomalous and emerge obvious leap values. When the confining pressure up to 200kPa, AE signals are mainly generated by sliding friction. With confining pressure increasing, the proporation of rolling friction and particle breakage is more and more obvious.

Acoustic Emission Testing of a Process Reactor

2005 ◽  
Author(s):  
Simon Yuen ◽  
David Wang ◽  
Paul Benedictus
Keyword(s):  
Acoustic Emission ◽  
Slag Inclusion ◽  
Thick Wall ◽  
Operating Pressure ◽  
Weld Overlay ◽  
Emission Testing ◽  
Acoustic Emission Testing ◽  
Acoustic Emission Test ◽  
Ae Signals

An Acoustic Emission Test (AET) was performed on a hydrocarbon processing reactor to inspect for environmental cracking in 2000. The thick-wall reactor was built in 1965, fabricated from 2.25Cr-1Mo steel with Type 347 stainless steel weld overlay. Past internal inspections of the reactor using liquid penetrant had revealed cracking at internal ring supports. Such inspections were exhaustive and time consuming. The AET was performed to achieve 100% inspection coverage of the reactor and to identify suspect areas for further evaluation. The test included over-pressurization of the reactor to 10% above its operating pressure before the shutdown and the actual cooling of the reactor from 745°F to 300°F. Upon completion of the acoustic emission (AE) monitoring, significant indications were identified, most noticeably at the reactor dump nozzle and the bottom head to shell weld. Both of these were in areas that had not been inspected previously. Follow-up inspections, including external ultrasonic and internal liquid penetrant test, were performed to investigate all the areas of significant AE activities. The results showed internal cracks isolated to the weld overlay at the catalyst dump nozzle and a 12” long weld slag inclusion in the bottom head to shell weld. A methodology was developed also to evaluation criticality of AE signals during different stages of AE test.

Acoustic Emission Test of Pressure Vessel Leakage

2013 ◽  
Author(s):  
Zhongzheng Zhang ◽  
Hua Liang ◽  
Cheng Ye ◽  
Wensheng Cai ◽  
Jun Jiang
Keyword(s):  
Acoustic Emission ◽  
Pressure Vessel ◽  
Safety Valve ◽  
Waveform Analysis ◽  
Statistical Parameters ◽  
Valve Leakage ◽  
Parameter Configuration ◽  
Acoustic Emission Test ◽  
Leakage Failure ◽  
Ae Signals

In order to study acoustic emission (AE) signals characteristics of pressure vessel leakage, several cases of common in-service pressure vessel with leakage failure such as seal leakage, pitting corrosion perforation and safety valve leakage were tested by AE technology. Through statistical parameters of AE signals and waveform analysis on leakage process, the distribution characteristics of the AE hits, amplitude and frequency etc. were summarized on the different forms of leakage failure. The study will provide a reference for the device parameter configuration, sensor selection and estimation of the failure mode on in-service pressure vessel leakage.

scholarly journals Analysis on rock fracture signals and exploration of infrared advance prediction under true triaxial loading

2021 ◽  
Author(s):  
jiawang hao ◽  
lan qiao ◽  
zhanjin li ◽  
Qingwen Li
Keyword(s):  
Strain Energy ◽  
Fractured Rock ◽  
Rock Fracture ◽  
Prediction Method ◽  
Triaxial Tests ◽  
Sudden Increase ◽  
True Triaxial ◽  
High Temperature Area ◽  
Infrared Monitoring ◽  
Temperature Area

To predict the fractured rock failure under deep triaxial stress in advance, the true triaxial tests were carried out using thermal infrared monitoring and acoustic emission (AE). This paper proposes “infrared temperature jumping rate (ITJR)” to reflect the “jumpiness” of the temperature field matrix, and establishes an infrared advance prediction method. The results show that the high temperature area will converge and expand gradually, and cracks propagate along a certain direction. In the sudden temperature reduction area, the rock stripping is easy to occur. At the boundary between high-low temperature areas, it is easy to produce breakage cracks and form rock spalling. In the short quiet period, the rock gradually gathers strain energy, which will be released in the fracture period. By comparing the time of AE sudden increase with the time of ITJR mutation, it shows that the method has a good advance prediction effect for rock fracture.

Acoustic Emission Test on Steel/Composite and Steel/Composite/Steel Built-Up Sections

2011 ◽  
Author(s):  
Rushie Ghimire ◽  
Gary Anderson ◽  
Fereidoon Delfanian
Keyword(s):  
Acoustic Emission ◽  
Tensile Tests ◽  
Glue Line ◽  
Stress And Strain ◽  
Steel Component ◽  
Cumulative Count ◽  
Steel Composite ◽  
Acoustic Emission Test ◽  
Ae Signals ◽  
Composite Steel

Acoustic Emission (AE) has been widely used to monitor and inspect built-up steel/composite sections; primarily at the glue line. AE testing was conducted on steel-composite (SC) and steel-composite-steel (SCS) built-up sections to determine the glue line failure and damage sustained by the inner layer of the built-up section by putting the sensors on the inner and outer layers of the built-up sections. The straight specimens of steel/composite and steel/composite/steel were tested with load applied to only one steel layer. The AE sensors were placed on the outer steel component so that detected signals traveled through the loaded steel, glue lines, and the composite or the loaded steel component, two glue lines, composite and unloaded steel components of the built-up section(s). The AE signals received by the sensors placed on the loaded steel in tension was compared to signals of sensors placed directly opposite on the unloaded steel or composite to determine the effect the steel/composite and steel/composite/steel built-up sections had on the signal. AE signals were also compared to signals generated during tensile tests of steel specimens only and composite specimens only. AE parameters like amplitude, hits, counts, frequency, cumulative count, and rise time of the AE signals were recorded, analyzed, and compared. AE parameters were also compared to traditional material properties (like yield and failure stress and strain). Tested specimens were examined with a microscope and observations were compared and analyzed relative to AE and material parameters, and reported.

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

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.

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

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.

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

2006 ◽  
Vol 13-14 ◽  
pp. 351-356 ◽  
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.

Sign in / Sign up

Export Citation Format

Share Document