scholarly journals Experimental Research on Acoustic Emission Characteristics and Felicity Effects during Coal Fatigue Failure under Cyclic Loading

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Yongjie Yang ◽  
Luyi Xing
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Fatigue Damage ◽  
Fatigue Failure ◽  
Stress Level ◽  
Counting Rate ◽  
Test System ◽  
Emission Characteristics ◽  
Evolution Law ◽  
Felicity Effect

In order to study the acoustic emission characteristics and Felicity effect in the process of coal fatigue failure and reveal the internal relationship between the fatigue damage evolution law and the acoustic emission activity, with the help of MTS815.02 electrohydraulic servo rock mechanics test system and PCI-2 acoustic emission detection and analysis system, a triaxial cycling loading acoustic emission test was carried out on the coal samples. The results show that the higher the upper limit stress is, the more obvious the degree of fatigue damage will be caused by coal samples. At the same time, the more active acoustic emission signal will appear. The coal samples under linear loading are on the initial damage state, and slight fatigue, moderate fatigue, deep fatigue, and ultimate fatigue failure under cyclic loading. The acoustic emission shows the “L-” type development evolution law in any previous stress level range, while at the last stress level, it shows the obvious “U-” type development evolution law. The higher the frequency of the cyclic loading is, the higher the rate of initiation and expansion of the microcrack will be, while the more obvious acoustic emission phenomenon will appear. Furthermore, the ringing counting rate is basically the same as that of the energy counting rate. Under triaxial cyclic loading, a shear failure mode that extends along different directions of fracture surface will be presented. The acoustic emission in the range of different stress levels shows a different degree of Felicity effect. In contrast, it is more reasonable to use the principal stress difference as a parameter to study the Felicity effect of coal under cyclic loading.

Experimental Verification and Theoretical Analysis on Felicity Effect of Acoustic Emission in Concrete

2007 ◽  
Vol 353-358 ◽  
pp. 2333-2336
Author(s):  
Rui Fu Yuan ◽  
Yuan Hui Li ◽  
Xing Dong Zhao
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Constitutive Model ◽  
Stress Level ◽  
Damage Mechanics ◽  
Kaiser Effect ◽  
Loading Cycle ◽  
Previous Cycle ◽  
Felicity Effect ◽  
Good Coincidence

The experiment of acoustic emission (AE) on concrete specimens under uniaxial cyclic loading was conducted. The Kaiser effect of acoustic emission in concrete and the Felicity effect, which manifest the memorizing ability to the maximum previous stress level of Kaiser effect, were validated by the experiment. The mechanism of Felicity effect was analyzed based on the theory of statistical damage mechanics and a tentative AE factor constitutive model of brittle material under uniaxial cyclic loading was suggested. The curve of constitutive model is in good coincidence with the curve from the experiment. The experimental results showed that the Felicity effect became clearer along with the increasing of stress level. Each loading cycle would cause new damage inside the material, and the response of material to the new loading cycle is different from the previous cycle.

scholarly journals Analysis of Damage Evolution in Concrete under Fatigue Loading by Acoustic Emission and Ultrasonic Testing

Materials ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 341
Author(s):  
Marc Thiele ◽  
Stephan Pirskawetz
Keyword(s):  
Acoustic Emission ◽  
Elastic Modulus ◽  
Cyclic Loading ◽  
Fatigue Damage ◽  
Fatigue Loading ◽  
Measurement Methods ◽  
Material Structure ◽  
Fatigue Process ◽  
Acoustic Methods ◽  
Normal Strength

The fatigue process of concrete under compressive cyclic loading is still not completely explored. The corresponding damage processes within the material structure are especially not entirely investigated. The application of acoustic measurement methods enables a better insight into the processes of the fatigue in concrete. Normal strength concrete was investigated under compressive cyclic loading with regard to the fatigue process by using acoustic methods in combination with other nondestructive measurement methods. Acoustic emission and ultrasonic signal measurements were applied together with measurements of strains, elastic modulus, and static strength. It was possible to determine the anisotropic character of the fatigue damage caused by uniaxial loading based on the ultrasonic measurements. Furthermore, it was observed that the fatigue damage seems to consist not exclusively of load parallel oriented crack structures. Rather, crack structures perpendicular to the load as well as local compacting are likely components of the fatigue damage. Additionally, the ultrasonic velocity appears to be a good indicator for fatigue damage beside the elastic modulus. It can be concluded that acoustic methods allow an observation of the fatigue process in concrete and a better understanding, especially in combination with further measurement methods.

Cumulative fatigue damage for 3-D angle-interlock woven composite under three-point bending cyclic loading

2012 ◽  
Vol 22 (1) ◽  
pp. 3-16 ◽  
Author(s):  
Limin Jin ◽  
Baozhong Sun ◽  
Bohong Gu
Keyword(s):  
Cyclic Loading ◽  
Fatigue Damage ◽  
Stress Level ◽  
Three Dimensional ◽  
Woven Composite ◽  
Damage Development ◽  
Static Test ◽  
Three Point Bending ◽  
Cumulative Fatigue Damage ◽  
Number Of Cycles

This article presents the quantitative characterization of cumulative fatigue damage behavior for the three-dimensional angle-interlock woven composite undergoing three-point bending cyclic loading. The S–N curve was obtained to demonstrate the fatigue life of the three-dimensional angle-interlock woven composite under different stress levels. The increment of cycles for each 5% interval of stress level was reported to show the difference of fatigue resistance performances of the three-dimensional angle-interlock woven composite among the high, middle, and low intervals of stress level. In addition, the Cumulative Fatigue Damage versus Number of Cycles (D–N) curve and the Deflection Index versus Number of Cycles (F–N) curve were deduced to characterize the three-stage cumulative fatigue damage. Furthermore, the damage morphologies of the three-dimensional angle-interlock woven composite after fatigue tests were photographed to compare with those in quasi-static test. The cracks initiation and propagation in the three-dimensional angle-interlock woven composite during the process of cyclic loading were summarized to find the mechanisms of fatigue damage development.

scholarly journals Size Effect of Concrete Specimens on the Acoustic Emission Characteristics under Uniaxial Compression Conditions

2017 ◽  
Vol 2017 ◽  
pp. 1-12
Author(s):  
Jianbo Wu ◽  
Enyuan Wang ◽  
Xuekun Ren ◽  
Mingwei Zhang
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Uniaxial Compression ◽  
Stress Level ◽  
Peak Stress ◽  
Deformation And Failure ◽  
Nonlinear Growth ◽  
Concrete Materials ◽  
Felicity Ratio ◽  
Loading Methods

Acoustic emission (AE) experiments under uniaxial compression and cyclic loading-unloading compression conditions were performed using different sizes of cubic concrete specimens. The influences of the loading methods and the concrete sizes on the mechanical parameters and the concrete AE activities were analyzed. The loading method was found to have great impact on the deformation, failure, and energy dissipation of concrete materials. With the increase of the material size, the uniaxial compressive strength of the concrete specimens gradually decreased, while the corresponding strain of peak strength increased first and then decreased. The elasticity modulus fluctuated irregularly. Under the uniaxial compression conditions, five AE patterns corresponding to the deformation and failure of the concrete materials were observed. A significant nonlinear relationship was found between the AE and the stress level. The cumulative AE rings at the peak stress showed nonlinear growth with the increase of the concrete size. Based on an established relationship between the cumulative AE rings and the stress level, the necessary conditions for the existence of the quiet AE period were given. Under the uniaxial cyclic loading-unloading compression conditions, the Felicity ratio decreased first and then increased as the stress increased. The research results have some guiding significance to AE-based monitoring of internal stress evolution of coal, rock, and concrete materials and thereby enable assessment of their stability.

Experimental and numerical studies on fracture characteristics of notched granite beams under cyclic loading and unloading

2020 ◽  
Vol 56 (1) ◽  
pp. 3-17
Author(s):  
Xiaojing Li ◽  
Peijie He ◽  
Jianhui Tang ◽  
Xudong Chen
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Correlation Method ◽  
Average Frequency ◽  
Test System ◽  
Underground Engineering ◽  
Three Point Bending ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading ◽  
Felicity Ratio

In underground engineering, such as mining engineering and deep tunnel engineering, the rock is often loaded and unloaded repeatedly. The strength of rock under cyclic load is lower than that under static load. To obtain the fracture response of the rock, the three-point bending tests of notched granite beams under cyclic loading and unloading were carried out with Electro-hydraulic Servo Material Test System. The acoustic emission technology was adopted to monitor the acoustic emission events of sample in the process of fracture. It is revealed that the fracture toughness of granite under cyclic loading and unloading is lower than that under static loading. Based on the acoustic emission energy obtained from monitoring, the damage evolution during cyclic loading and unloading was analyzed. The fracture mode of granite samples is analyzed by the RA value-average frequency correlation method. And the Felicity ratio during the loading and unloading cycle was calculated to evaluate the severity of initial damage of the material. It is revealed that Kaiser effect appears only in the elastic deformation stage of cyclic loading unloading bending. The Holmquist–Johnson–Cook damage constitutive model and Weibull distribution were used to establish the heterogeneous granite model. And the three-point bending of the model under cyclic loading and unloading was simulated to disclose the crack growth mechanism of rock. The study may provide some references for rock instability control in geotechnical engineering construction.

scholarly journals Experimental Study on Mechanical Properties and Acoustic Emission Characteristics of Water Bearing Sandstone under Stable Cyclic Loading and Unloading

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Xinzhan Qin ◽  
Yu Zhou ◽  
Manchao He
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Cyclic Loading ◽  
Water Content ◽  
Coal Mines ◽  
Surrounding Rock ◽  
Emission Characteristics ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading ◽  
Pumped Storage

Due to the adjustment of energy structure, a large number of coal mines are abandoned. Considering the environmental and economic effects, many experts proposed to use the abandoned mine cavern as the reservoir of the pumped storage power station. Furthermore, considering the long-term effects of repeated pumping and drainage and hydrodynamic pressure on the surrounding rock in coal mines, a large amount of sandstone was collected from the Ruineng coal mine in Yan’an city to carry out a series of laboratory tests. Through uniaxial compression testing of rock samples with different water content rates, combined with acoustic emission (AE) analysis, the strength softening and macrodeformation characteristics are obtained, and the influence of water content on acoustic emission characteristics is clarified. The mechanical properties of water bearing rock under cyclic loading and unloading experiments with varying upper limits are obtained using a triaxial test system, and the precursory information of rock failure is captured, providing significant guidance for stability analysis and instability warning for surrounding rock in pumped storage power stations.

scholarly journals Creep Structure Effect of Layered Rock Mass Based on Acoustic Emission Characteristics

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Huichen Xu ◽  
Yong Zhang ◽  
Chengwei Zhao ◽  
Chengyu Miao ◽  
Xiaoming Sun
Keyword(s):  
Acoustic Emission ◽  
Rock Mass ◽  
Inclination Angle ◽  
Stress Level ◽  
Rock Sample ◽  
Structural Effect ◽  
Emission Characteristics ◽  
Structural Effects ◽  
Layered Rock ◽  
Layered Rock Mass

Investigating the creep structural effect of layered rock mass is of great practical and theoretical significance. In this paper, taking the Muzhailing tunnel as an example, structure effect of layered rock mass based on acoustic emission characteristics has been analyzed. The study shows that creep parameters of layered rock mass are significantly influenced by structural effects, and the overall creep variable is small. The creep deformation of layered rock mass includes transient creep and steady-state creep at a low stress level. At a higher stress level, when the long-term strength of the rock sample is reached, the deformation increases rapidly, and the accelerated creep occurs in a very short period of time. The creep equation of the structural effects of layered rock mass was established based on the experimental results. Acoustic emission characteristics are analyzed during creep experiment; the study shows that the energy released at the time of initial loading and destruction accounted for most of the total energy. The initial energy release increased first and then decreased with the increase in inclination angle; as the inclination angle increased, the cumulative energy when the rock sample was damaged first decreased and then increased. The structural effect on the main frequency value at the time of failure mainly reflected in the trend that the main frequency value first increased and then decreased as the inclination angle increased. Based on the above analysis, we can recognize the structural effects of layered rock mass and provide the necessary parameters for on-site support.

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