Acoustic Emission Activity Research Articles

Particle Flow Simulation of Failure Characteristics of Deep Rock Influenced by Sample Height-to-Width Ratios and Initial Stress Level under True-Triaxial Unloading

The micromechanism of the effects of different height/width ratios (H/W) and initial stress levels on unloading characteristics of deep rock was investigated based on PFC3D true-triaxial unloading simulation. The results show that the increase of H/W will increase the movement speed of rock particles and intensify the acoustic emission (AE) activity inside the rock. With the increase of H/W, the failure mode of rock changes from splitting failure to tensile-shear failure. With increasing initial stress level, the particle velocity and overall fragmentation degree of rock increase. However, the increase of lateral stress will limit the coalescence of microfractures and weaken AE activity in the rock. Under unloading condition, the bonds between particles generally crack along the unloading direction, and the tensile effect is more pronounced under the condition of low initial stress level and high H/W. Under unloading condition, the variable energy of rock increases with increasing H/W and initial stress level, and the kinetic energy of rock particles increases with increasing H/W. The increase of initial stress level will increase the kinetic energy of rock particles when H/W is high.

Monitoring the effect of age and drying on the fracture behavior of earth concrete

This work aims to assess at days 14, 28 and 90 the effect of different curing conditions on earth concrete mixtures on the compressive strength and fracture energy. Moreover, the compression tests were monitored in parallel with AE technique and image processing. The results show the domination of suction effect at the age of 14 and 28 days in all mixtures. Nevertheless, its dominance reduces at later ages in the RS mixtures. Moreover, the fracture energy decreases with time indicating a more brittle behavior. The acoustic emission (AE) technique was able to reflect this brittleness by displaying fewer phases of AE activity during the fracture process, delay in crack formation and decrease in AE hits. In addition, the cameras’ photos revealed the occurrence of higher damage at 90 days.

Quantitative statistical analysis of the crack propagation and fracture process of self‐compacting rubber concrete based on acoustic emission

In this study, acoustic emission (AE) was used to monitor the whole process of tensile and fracture of the self-compacting rubber concrete (SCRC) under four-point bending. The AE activities of SCRC during the stretching and fracture process were analyzed by statistical methods to correlate the process of crack propagation with changes in mechanical properties. And by comparing the tensile and fracture properties, the change patterns of crack mode, the cumulative events and energy of AE in the bending process of SCRC with different rubber particles content, the influence of the incorporated rubber particles on the propagation of microcracks, and the macroscopic fracture mechanism were analyzed. Studies showed that with the incorporation of rubber particles, the ductility of the concrete before and after cracking was improved. Due to the weak bonding surface between the rubber particles and the matrix, the microcracks began to propagate at low-stress levels and developed steadily throughout the stretching process. As the rubber content increased, more rubber components participated in the tensile and fracture process. Because of the elastic stretching of rubber particles, the tensile deformation capacity and fracture properties of the concrete have been improved. And in the whole process of tensile and fracture, the cracking of the weak cemented surface of the matrix and the pulling of the rubber particles were more likely to cause shear mode cracks.

Numerical investigation on fracture evolution of asphalt mixture compared with acoustic emission

ABSTRACT To reveal the fracture damage of asphalt mixture, an image-based numerical approach is proposed in this study considering the distribution of aggregate and asphalt mortar. Both digital image processing technique and discrete element method are applied to simulate the inhomogeneity of specimen and its fracture evolution at low temperature. At the same time, the acoustic emission (AE) activities are measured in laboratory to be compared with the micromechanical responses of numerical models. Results indicate that the developed method is suitable for modelling the numerical specimen of asphalt mixture, taking into account the size gradation and morphology of aggregates in the two-dimensional image. The numerical results of asphalt mixture have a good agreement with that of laboratory tests in cracking distribution and statistical probability. Cracks first appear on the aggregate–mortar interface, located in the upper and middle parts of the specimen, and then the brittle shear failure gradually propagates along the surface. Cumulative probabilities of both AE ringing counts and microfracture number follow the Weibull distribution. The numerical model has a significant advantage in the fracture evolution of asphalt mixture because the eccentric loading is unavoidable in laboratory tests due to personal and mechanical errors.

Non-invasive early detection of failure modes in total hip replacements (THR) via acoustic emission (AE)

Total hip replacements (THR) are becoming an common orthopedic surgucal procedure in the United States (332K/year in 2017) to relieve pain and improve the mobility of those that are affected by osteoarthritis, ankylosing spondylitis, or injury. However, complications like tribocorrosion, or material degradation due to friction and corrosion, may result in THR failure. Unfortunately, few strategies to non-invasively diagnose early-stage complications are reported in literature, leading to implant complications being detected after irreversible damage. Therefore, the main objective of this study proposes the utilization of acoustic emission (AE) to continuously monitor implant materials, CoCrMo and Ti6Al4V, and identify degradations formed during cycles of sleeping, standing, and walking by correlating them to potential and friction coefficient behavior. AE activity detected from the study correlates with the friction coefficient and open-circuit potential observed during recreated in-vitro standing, walking, and sleeping cycles. It was found that the absolute energy level obtained from AE increased as the friction coefficient increased, potential decreased, and wear volume loss increased. Through the results, higher friction coefficient and AE activity were observed in Ti6Al4V alloys while there was also a significant drop in potential, indicating increased tribocorrosion activity. Therefore, AE can be utilized to predict material degradations as a non-invasive method based on the severity of abnormality of the absolute energy and hits emitted. The correlation between potential, friction coefficient, and AE activity was further confirmed through profilometry which showed more material degradation in Ti6Al4V than CoCrMo. Through these evaluations, it was demonstrated that AE could be utilized to identify the deformations and failure modes of implant materials caused by tribocorrosion.

Preparatory acoustic emission activity of hydraulic fracture in granite with various viscous fluids revealed by deep learning technique

SUMMARYTo investigate the influence of fluid viscosity on the fracturing process, we conducted hydraulic fracturing experiments on Kurokami-jima granite specimens with resins of various viscosities. We monitored the acoustic emission (AE) activity during fracturing and estimated the moment tensor (MT) solutions for 54 727 AE events using a deep learning technique. We observed the breakdown at 14–22 MPa of borehole pressure, which was dependent on the viscosity, as well as two preparatory phases accompanying the expansion of AE-active regions. The first expansion phase typically began at 10–30 per cent of the breakdown pressure, where AEs occurred three-dimensionally surrounding the wellbore and their active region expanded with time towards the external boundaries of the specimen. The MT solutions of these AEs corresponded to crack-opening (tensile) events in various orientations. The second expansion phase began at 90–99 per cent of the breakdown pressure. During this phase, a new planar AE distribution emerged from the borehole and expanded along the maximum compression axis, and the focal mechanisms of these AEs corresponded to the tensile events on the AE-delineating plane. We interpreted that the first phase was induced by fluid penetration into pre-existing microcracks, such as grain boundaries, and the second phase corresponded to the main fracture formation. Significant dependences on fluid viscosity were observed in the borehole pressure at the time of main fracture initiation and in the speed of the fracture propagation in the second phase. The AE activity observed in the present study was fairly complex compared to that observed in previous experiments conducted on tight shale samples. This difference indicates the importance of the interaction between the fracturing fluid and pre-existing microcracks in the fracturing process.

Laboratory-Scale Investigation of the Slippage of a Natural Fracture Resulting from an Approaching Hydraulic Fracture

The interaction between a natural fracture (NF) and a hydraulic fracture (HF) has been studied extensively, both experimentally and numerically, to better understand the potential for crossing and arrest of a hydraulic fracture intersecting a natural fracture. However, the actual mechanical interaction between a hydraulic and a natural fracture or a bedding plane has not been studied, particularly under triaxial stress and injection conditions. Analysis of field microseismic data recorded during hydraulic fracturing shows that the bedding plane could slip due to the approaching hydraulic fracture. In this paper, we present the results of some lab-scale experimental work, demonstrating HF/NF interaction with an emphasis on the slippage of a discontinuity surface. Injection pressure, stress applied, and the sample deformation are monitored during the tests. Acoustic Emission (AE) technology is employed to record the AE signals generated during fracture initiation, propagation, and during the sliding of the joint. In addition, strain gauges are used to measure the slippage on the natural fracture. The tests are carried out on 101.6 mm diameter cylindrical samples of PMMA, shale, and granite. The calculated displacement based on the recorded strain clearly shows a jump at the breakdown point, which is accompanied by increased AE activity and stress drop. Analysis of the data clearly shows the occurrence of slippage on the joint in response to an approaching hydraulic fracture. Expectedly, the degree of shear slip varies with natural fracture dip and friction angle.

Experimental Investigation of Fatigue Crack Growth Behavior of the 2.25Cr1Mo0.25V Steel Welded Joint Used in Hydrogenation Reactors.

In this work, the fatigue crack growth (FCG) behavior and fatigue damage mechanism of the 2.25Cr1Mo0.25V steel welded joint used in hydrogenation reactors were investigated. The multi-pass welding was carried out to manufacture the welded joint using the combined shielded metal arc welding (SMAW) and submerged automatic arc welding (SAAW) processes. The FCG behavior of different zones in the welded joint, including the base metal (BM), the heat-affected zone (HAZ) and the weld metal (WM), were studied by compact tension tests. Moreover, the acoustic emission (AE) technique was used to monitor AE signals generated from FCG process for further understanding FCG behavior and fatigue mechanisms. Additionally, the microstructures and fracture surfaces of different specimens were observed by optical microscopy (OM) and scanning electron microscopy (SEM). The results revealed that the microstructure of BM is fine granular bainite, while the WM shows coarser bainite grains. The HAZ exhibits the most significant inhomogeneity with large dispersion of grain size. FCG results showed that the HAZ exhibits much higher fatigue crack growth rate (FCGR) at low ΔK values, while the BM shows the most superior fatigue resistance. The AE technique is successful in monitoring and identifying damage evolutions during the FCG process. Moreover, an enhanced AE activity is observed in FCG of the WM specimen, which is attributed to the combined influence of the formation of numerous secondary cracks and coarse-grained microstructures.

Characterisation of hydrogen assisted cracking in modified 9Cr-1Mo steel welds using acoustic emission non destructive technique

ABSTRACT This study aims a systematic experimental investigation using acoustic emission (AE) non-destructive technique for online monitoring of hydrogen assisted cracking (HAC) in modified 9Cr-1Mo steel (P91 steel) welds during Gap-Bead on Plate (G-BOP) and implant tests. Welds made without preheating, with different preheating and combined pre and post heating were tested using G-BOP test. AE results of G-BOP tests have shown that time duration in which HAC active varies with temperature of preheating and combined pre and post heating. Reduction of AE activity in welds made with pre and post heating compared to those only made with preheating revealed a beneficial effect of the former in reducing HAC. In the case of implant tests, crack initiation and propagation are identified for different applied loads from the AE analysis. An attempt has been made to compare HAC during G-BOP tests and implant tests using AE frequency analysis. The dominant frequency of AE signals characteristic of HAC has been identified. This study shows the potential of using AE frequency analysis for online monitoring of hydrogen assisted cracking (HAC) in welds.

Fracture monitoring of steel and GFRP reinforced concrete beams using acoustic emission and digital image correlation techniques

AbstractIn this work, fracture monitoring of steel and GFRP bars reinforced concrete beams in flexure is investigated by using non‐destructive acoustic emission (AE) and digital image correlation (DIC) techniques. The combined methodology provides complementary information from 'the ear' aided by the AE and from 'the eye' aided by the DIC. AE waveform parameters of the number of AE hits and their amplitudes, cumulative signal strength (CSS), average frequency, and rise‐time successfully pick‐up the divergent cracking initiation and fracture progression in steel‐reinforced concrete (RC) and GFRP‐RC beams. AE‐XY plots and longitudinal strain profiles obtained from DIC give an early, online, and real‐time representation of progressive AE activity and strains inside concrete much before it is visible to the naked eye. AE in conjunction with DIC was able to efficaciously depict the micro‐and‐macro cracks evolution and their advancement in steel‐RC and GFRP‐RC at various stages of loading Moreover, DIC identified critical damage areas as a function of loading periods, while AE was capable of monitoring the damage process and revealed changes in the overall behavior. It is successfully demonstrated that combined AE and DIC monitoring can enhance non‐destructive monitoring skills in RC structures involving widely different steel and GFRP bars as reinforcements and depict efficaciously their fracture/cracking behavior.

Assessment of bond-slip behavior of hybrid fiber reinforced engineered cementitious composites (ECC) and deformed rebar via AE monitoring

This paper investigates the efficiency of acoustic emission (AE) technique for monitoring and assessing the bond-slip behavior and damage characteristics of deformed rebar embedded in hybrid fiber reinforced engineered cementitious composites (ECC). A series of pull-out tests were conducted on 48 prism samples with variable rebar diameters (14 mm, 20 mm, and 25 mm), embedded length (3d, 4d and 5d), and cover thickness (2.5d, 4d, 5d and 6d). Two AE sensors, attached on ECC surface and rebar surface respectively, were utilized to critically monitor the AE activity emitted from the ECC matrix and the interface between ECC and rebar throughout the tests. The bond-slip behavior of ECC-rebar presented a more ductile performance than conventional concrete (CC)-rebar because of fiber bridging effect. The damage classification and damage characteristics were clarified by measuring AE activity. The debonding process of ECC-rebar could be divided into four main stages based on the slope changes of cumulative AE hits, and further refined into several substages based on the sudden rises of AE energy. Besides AE cumulative parameters, the Ib-values calculated from AE signals of ECC matrix and ECC-rebar interface were analyzed and compared, which behaved more effectively in identifying the development of cracks and distinguishing the maximum bond stress. Also, the AE intensity analysis was implemented to identify the micro-mechanism transformation during different bonding stages. Moreover, the AE intensity results of CC-rebar obtained from previous research and ECC-rebar in this study were compared.

Damage Analysis of Composite CFRP Tubes Using Acoustic Emission Monitoring and Pattern Recognition Approach.

The acoustic emission method has been adopted for detection of damage mechanisms in carbon-fiber-reinforced polymer composite tubes during the three-point bending test. The damage evolution process of the individual samples has been monitored using the acoustic emission method, which is one of the non-destructive methods. The obtained data were then subjected to a two-step technique, which combines the unsupervised pattern recognition approach utilizing the short-time frequency spectra with the boundary curve enabling the already clustered data to be additionally filtered. The boundary curve identification has been carried out on the basis of preliminary tensile tests of the carbon fiber sheafs, where, by overlapping the force versus time dependency by the acoustic emission activity versus time dependency, it was possible to identify the boundary which will separate the signals originating from the fiber break from unwanted secondary sources. The application of the presented two-step method resulted in the identification of the failure mechanisms such as matrix cracking, fiber break, decohesion, and debonding. Besides the comparison of the results with already published research papers, the study presents the comprehensive parametric acoustic emission signal analysis of the individual clusters.

Study on mechanical properties and damage evolution of carbonaceous shale under triaxial compression with acoustic emission

To explore the mechanical properties and damage evolution characteristics of carbonaceous shale with different confining pressures and water-bearing conditions, triaxial compression tests accompanied by simultaneous acoustic emission (AE) monitoring were conducted on carbonaceous shale rock specimens. The AE characteristics of carbonaceous shale were investigated, a damage assessment method based on Shannon entropy of AE was further proposed. The results suggest that the mechanical properties of carbonaceous shale intensify with increasing confining pressure and degrade with increasing water content. Moisture in rocks does not only weaken the cohesion but also reduce the internal friction angle of carbonaceous shale. It is observed that AE activities mainly occur in the post-peak stage and the strong AE activities of saturated carbonaceous shale specimens appear at a lower normalized stress level than that of natural-state specimens. The maximum AE counts and AE energy increase with water content while decrease with confining pressure. Both confining pressure and water content induce changes in the proportions of AE dominant frequency bands, but the changes caused by confining pressure are more significant than those caused by water content. The results also indicate that AE entropy can serve as an applicable index for rock damage assessment. The damage evolution process of carbonaceous shale can be divided into two main stages, including the stable damage development stage and the damage acceleration stage. The damage variable increases slowly accompanied by a few AE activities at the first stage, which is followed by a rapid growth along with intense acoustic emission activities at the damage acceleration stage. Moreover, there is a sharp rise in the damage evolution curve for the natural-state specimen at the damage acceleration stage, while the damage variable develops slowly for the saturated-state specimen.

Effects of bedding orientation on the failure pattern and acoustic emission activity of shale under uniaxial compression

The bedding orientation influences the failure pattern and brittleness of shale. Clarifying the relation between acoustic emission and the effects of bedding orientation on the failure behaviors of shale is important to understand the mechanism of the formation of fracture networks. In this study, we analyzed the failure patterns and crack complexity of the shale specimens with various bedding orientations under uniaxial compression using X-ray computed tomography. We proposed an improved criterion based on the acoustic emission waveform parameters to identify the mechanism of the acoustic emission events and showed that the failure mechanism changed from tension to shear during the failure process of each specimen because the shear cracks link independent tensile cracks to form macrofractures in the later loading stage. The proportion of shear-mode events in the specimens declined when the bedding orientation angle increased from 0° to 90°, whereas that of the tensile-mode events exhibited an opposite trend; these changes were consistent with the observation results of X-ray images, indicating the transition of the dominant failure mechanisms with the bedding orientation. The large b value of the acoustic emission events corresponded to a complex crack distribution; thus, this b value may be useful to evaluate the brittleness of shale. These results denote the relation between the mechanisms of the failure patterns in shale and the acoustic emission activity and improve our recognition to the fracture network characteristics.

Failure evaluation of composite concrete using an acoustic emissions technique

One major problem with concrete is high brittleness with low tensile strength and strain capacity, which can cause sudden failure. Structural Health Monitoring (SHM) is thus very important to detect cracks in initial stages to avoid catastrophic failure. In this research, an acoustic emissions (AE) technique was applied to enable SHM to detect cracks and predict the failure of composite concrete. This physical non-destructive testing process utilises transient elastic waves caused by the rapid release of energy from a localised source within a structure. A low-frequency acoustic emission system was thus tested for economical monitoring of the damage to reinforced composite cubic concrete under compression. Specimens of standard size (150 x 150 x 150 mm) were produced without and with polyamide reinforcement bars. The compression strength of the cubic concrete was then tested according to BS EN 12390-1. Prior to testing, a low-cost single piezoelectric wafer active sensor was applied to the centre of one side of each specimen, which was then connected to a PC’s sound card. Data was successfully recorded using sensors and the real-time of the applied load was recorded using a separate data logger. Traditional AE signal parameters were extracted and used for damage evaluation. The results indicated that the AE system was capable of detecting cracks in representative structures to final failure. Signal amplitude with load versus time showed an increase in AE activity and energy approaching the end of the test, while commutative hits could be used to distinguish between stable and unstable loading stages. The system also detected the initiation of the final failure stage at 72.6% and 83% of the failure load of specimens without and with polyamide reinforcement bars, respectively.

Study on crack dynamic evolution and damage-fracture mechanism of rock with pre-existing cracks based on acoustic emission location

The acoustic emission (AE) location technique is used to characterize the entire progressive failure process of rock with preexisting cracks. The mechanical properties, AE characteristics, crack dynamic propagation process, failure modes and damage-fracture evolution rules are studied for prefabricated rock samples with different crack inclination angles under uniaxial compression. The results show that the peak strength and elastic modulus first decrease and then increase with increasing crack angle. AE events exhibit different characteristics with changes in stress. In the initial compaction and elastic deformation stage, the AE activity is not obvious; when microcracks form in the rock sample, the AE count increases; after entering the crack stable growth stage, the AE activity becomes significant; during the period of unstable crack propagation to rock failure, the AE activity is extremely active. The AE location can well accurately reflect the crack initiation position, propagation direction and surface orientation in the rock. AE location can well reflect cracks initiation position, propagation direction and space surface shape in the rock. For intact samples, microcracks are first generated at the ends of the sample and extend internally along the loading direction until they coalesce and form macroscopic cracks; for precracked samples, microcracks appear first at the tips of the prefabricated crack, and extend outward at a certain angle, while the microcracks are mainly concentrated around the preexisting crack, with a small number of microcracks distributed at both ends of the sample. With increasing the crack angle, the rock failure mode changes from splitting failure to tension-shear mixed failure and finally to single shear failure. The AE positioning results are in good agreement with the observed macroscopic failure of the rock samples. The damage variable based on AE counts divides the rock damage-fracture evolution process into four stages, and the initial damage and damage rate of the rock sample with a crack angle of 45° are the largest.

Influence of graphite content on fracture behavior of MgO–C refractories based on wedge splitting test with digital image correlation method and acoustic emission

Mechanical and thermal stresses are one of the main reasons causing the damage of MgO–C refractories in service. An in-depth understanding of the fracture behavior of MgO–C refractories is essential for the further development of high-performance MgO–C refractories. In this paper, effect of graphite content on fracture behavior of MgO–C refractories under wedge splitting test was investigated with the Digital Image Correlation (DIC) and Acoustic Emission (AE) technology. The results showed that the increase of graphite content in MgO–C refractories led to a reduction in brittleness and an improvement of thermal shock resistance. MgO–C refractories with higher graphite content were likely to generate crack at earlier loading stage and to have larger ultimate crack mouth opening displacement. It indicated a lower crack initiation resistance of MgO–C refractories and a better further damage propagation resistance. In addition, the proportion of crack in the MgO grains decreased and the tortuousness of crack path increased with the increasement of graphite content. It promoted the transformation of AE activity and energy dissipation from “burst type” to “slow release type” and the nonlinearity of MgO–C refractories mechanics behavior during failure process.

Laboratory Investigation on the Effects of Natural Fracture on Fracture Evolution of Granite Exposed to Freeze-Thaw-Cyclic (FTC) Loads

The natural fractures in rock mass are susceptible to damage evolution when subjecting to repeated freeze-thaw (F-T) weathering in cold regions, which can lead to the instability of rock engineering and even occurrence of geological hazards. Knowledge of how natural fracture impacts the overall fracture evolution of freeze-thawed rock is important to predict the stability of rock structure. In this work, we reported uniaxial experimental measurements of the changes in strength, deformation, acoustic emission (AE) pattern, and Felicity effect during increasing amplitude stress-cycling conditions on granite. The results show that the change of fracture aperture is related to the fracture openness and filling characteristics, open-type fracture is sensitive to F-T treatment, and its aperture increases faster than the close-type and fill-type fracture. In addition, strength decreases, and the damping characteristics first decrease and then increase with increasing natural fracture volume. AE activities also present different responses during sample deformation. The proportion of AE signals having low-frequency characteristics increases with increasing natural fracture volume, and the shear sliding along natural fracture results in the surge of AE activities. Moreover, the Felicity effect indicates that the Felicity ratio presents a fluctuation decreasing trend, and the preexisting fractures alter the stress memory characteristics of rock. It is suggested that the changes of the geomechanical and AE pattern are the interactions between the natural fracture and the newly stimulated fracture. The testing results are expected to improve the understanding of the influence of natural fractures on rock fracture evolution and can be helpful to predict the stability of rock structures and rock mass in cold regions.

Acoustic Emission Characteristics and Joint Nonlinear Mechanical Response of Rock Masses under Uniaxial Compression

The joint arrangement in rock masses is the critical factor controlling the stability of rock structures in underground geotechnical engineering. In this study, the influence of the joint inclination angle on the mechanical behavior of jointed rock masses under uniaxial compression was investigated. Physical model laboratory experiments were conducted on jointed specimens with a single pre-existing flaw inclined at 0°, 30°, 45°, 60°, and 90° and on intact specimens. The acoustic emission (AE) signals were monitored during the loading process, which revealed that there is a correlation between the AE characteristics and the failure modes of the jointed specimens with different inclination angles. In addition, particle flow code (PFC) modeling was carried out to reproduce the phenomena observed in the physical experiments. According to the numerical results, the AE phenomenon was basically the same as that observed in the physical experiments. The response of the pre-existing joint mainly involved three stages: (I) the closing of the joint; (II) the strength mobilization of the joint; and (III) the reopening of the joint. Moreover, the response of the pre-existing joint was closely related to the joint’s inclination. As the joint inclination angle increased, the strength mobilization stage of the joint gradually shifted from the pre-peak stage of the stress–strain curve to the post-peak stage. In addition, the instantaneous drop in the average joint system aperture (aave) in the specimens with medium and high inclination angles corresponded to a rapid increase in the form of the pulse of the AE activity during the strength mobilization stage.

ACOUSTIC EMISSION TESTING OF FIBERGLASS PIPES AND FITTINGS

Experimental studies was carried out. The purpose was to develop a method to test fiberglass pipelines in operating mode. The acoustic emission method was chosen as the main method of nondestructive testing, and visual and dimensional inspection was chosen as an additional method. Acoustic parameters and acoustic emission properties of fiberglass pipes were determined. It was found that acoustic emission sensors can be installed at distances of up to 9-18 m from each other. A series of loading tests was carried out to refine the methodology. Every loading case was performed until leakage registration. In most cases, leakage occurred near the fillet at pressures of 2.2…3.0 from the working pressure, which indicates a large margin of safety for fiberglass pipes. It is confirmed that the acoustic emission method allows early defect detection. Based on the acoustic emission data, 4 main stages of fiberglass pipes degradation were identified. Visual and dimensional inspection was informative only at stages III – IV. Stage IV in most cases corresponds to the leakage. Even early stage of depressurization was registered as continuous acoustic emission. Signals with amplitudes exceeding 60…80 dB were registered at all loading stages. The location map became informative after filtering events by acoustic emission parameters. A methodology for the testing of fiberglass pipes and fittings in operating mode was developed. It contains, in contrast to the currently valid standards, specific numerical values of various quantities related to both the preparation and carrying out of acoustic emission testing and the classification of the identified sources of acoustic emission according to the degree of danger and allows to evaluate the residual life of fiberglass pipelines. The most informative parameter was the activity of acoustic emission; therefore, it is recommended to carry out loading without holding the pressure. It is planned to carry out additional experiments to clarify the mechanisms of fracture acting at each of the 4 identified stages of degradation.