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 Research on Acoustic Emission of Granite under Uniaxial Compression and Splitting Tensile

2012 ◽  
Vol 232 ◽  
pp. 24-27
Author(s):  
Zong Zhan Li ◽  
Jun Lin Tao ◽  
Yi Li
Keyword(s):  
Compressive Strength ◽  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Loading Rate ◽  
Testing Machine ◽  
Peak Stress ◽  
Uniaxial Compression Test ◽  
Peak Strain ◽  
Ae Energy

This paper makes the acoustic emission of granite under uniaxial compression and splitting tensile test by electro-hydraulic testing machine and AE .We studied the relationship of uniaxial compressive strength and splitting tensile strength with the loading rate and AE characteristics of granite .The results show that uniaxial compressive strength and peak strain raise with loading rate, the AE energy gradually increases and get maximum in the 30% of the peak stress in the process of uniaxial compression test, and in the splitting tensile AE energy generates in the initial loading and gets maximum when the granite brittle fracture.

Damage Evolution Analysis of Calcareous Mudstone with Different Water Content under Uniaxial Compression

2010 ◽  
Vol 168-170 ◽  
pp. 1388-1395
Author(s):  
Ming Ji ◽  
Nong Zhang ◽  
Feng Gao
Keyword(s):  
Acoustic Emission ◽  
Water Content ◽  
Uniaxial Compression ◽  
Damage Evolution ◽  
Testing Machine ◽  
Strain Curve ◽  
Peak Stress ◽  
Damage Evolution Equation ◽  
Emission Activity ◽  
Hydraulic Servo

Uniaxial compression and acoustic emission experiments of calcareous mudstone with different water content were carried out by using microcomputer controlled electro-hydraulic servo compression testing machine control system of YAW series equipped by coal-rock acoustic and electric data acquisition system of CTA-1-type. Mchanical properties and acoustic emission law of calcareous mudstone were studied. It is concluded from experiment result that rock’s elastic modulus and compressive strength both decrease with increase water content but peak stress shows the opposite trend. It is also found that calcareous mudstone is brittleness with low water content but when water content reaches saturation, calcareous mudstone presents plastic features. Acoustic emission curve fits well with stress-strain curve: acoustic emission activity begins intensifying when stress reaches 70% of peak stress, correspondingly, acoustic emission is up to maximum at peak stress. Based on Weibull hypothesis and acoustic emission experiment, damage law of water bearing calcareous mudstone is researched and damage evolution equation with time variable is advanced.

scholarly journals Acoustic Emission Characteristics of Compressive Deformation and Failure of Siltstone under Different Water Contents

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Lei Chen ◽  
Jian Zhao ◽  
Zhiyang Zheng
Keyword(s):  
Acoustic Emission ◽  
Water Content ◽  
Count Rate ◽  
Water Saturation ◽  
Peak Stress ◽  
Liaoning Province ◽  
Open Pit ◽  
Deformation And Failure ◽  
Deformation Phase ◽  
Water Saturated

The uniaxial compression and acoustic emission (AE) monitoring of siltstone specimens in the Gongchangling open-pit iron mine in Liaoning Province was conducted by evaluating the effects of three water saturation levels: dry, natural, and water-saturated. The siltstone AE characteristics were analyzed according to water content; the relationship between the AE characteristics and the growth and expansion of siltstone cracks was subsequently discussed. Research results indicated the following: siltstone specimens had distinctly different mechanical properties and AE characteristics according to water content; as the water content increased the compressive strength and elasticity modulus of specimens decreased. In the compacting phase of specimens under compression, the AE count rate of the water-saturated specimen was relatively small and the events were relatively stable. In the linear-elastic deformation phase, the AE count rate of the dry specimen increased sharply, reaching approximately 400 times/s. In the plastic yield deformation phase, the peak value of the AE count rate of the dry specimen ranged between 955 and 1,068 times/s, whereas that of the water-saturated specimen only attained a range of 635 to 782 times/s. In the failure phase, the time to reach the peak stress value of the dry specimen was increased as compared to that of the AE count rate.

Uniaxial Compression with Acoustic Emission Experimental Study on Rock Damage Process

2012 ◽  
Vol 204-208 ◽  
pp. 173-176
Author(s):  
Jing Hong Liu ◽  
Xiao Hua Liu ◽  
Wen Han
Keyword(s):  
Acoustic Emission ◽  
Crack Propagation ◽  
Uniaxial Compression ◽  
Failure Process ◽  
Structure Stability ◽  
Uniaxial Compression Test ◽  
Concrete Material ◽  
Deformation And Failure ◽  
Disaster Assessment ◽  
Contrast Analysis

Acoustic emission technique is an important technique for monitoring crack propagation and failure process of rock, coal and concrete material. A uniaxial compression test with acoustic emission monitoring on coal and rock samples’ deformation and failure process were carried out. Failure precursor information of rock, coal and concrete material were studied through contrast analysis the experiment result include acoustic emission signals, strain, load correlation of sample inner crack propagation to failure process. The test provided necessary data to further understand on rock burst failure disaster. The test result provides a theoretical basis for further application of acoustic emission for prediction coal rock dynamic disaster, assessment rock and concrete structure stability and study rock concrete material failure process mechanism.

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.

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 Investigation on Acoustic Emission Kaiser Effect and Frequency Spectrum Characteristics of Rock Joints Subjected to Multilevel Cyclic Shear Loads

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Zhiqiang Hou ◽  
Changhong Li ◽  
Zhengyang Song ◽  
Yonggang Xiao ◽  
Chen Qiao ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Frequency Spectrum ◽  
Rock Joints ◽  
Displacement Curve ◽  
Kaiser Effect ◽  
Cyclic Shear ◽  
Shear Damage ◽  
Spectrum Characteristics ◽  
Felicity Ratio

Rock joints have obvious acoustic emission (AE) Kaiser effect and Felicity effect under multilevel cyclic shear conditions. The TFD-20H/50J rock shear apparatus was used to carry out cyclic loading and unloading joint shear tests, and the acoustic emission parameters and frequency spectrum characteristics of the whole shearing process were analyzed. The results show that, under the cyclic loading, the shear stress-displacement curve forms several cyclic hysteresis loops, and the number of loops increases with the increase of normal stress. With the cycles increase, the shear damage gradually increases, and the Felicity ratio gradually decreases. The Felicity ratio at the final shear failure moment is about 0.94~0.99. The ratio of the RA value (rise time/amplitude) and the average frequency value (RA-AF) is used to classify the cracking mode of the joint sample. There are two AE crack signal types (tensile type and shear type) during shear damage. The peak frequency is displayed as high, medium, and low three frequency bands, which are distributed in the range of 0~35 kHz, 35~122 kHz, and 122~300 kHz, respectively. Both low-frequency and high-frequency signals account for less than 10%, and medium-frequency signals account for more than 90%. The research of the AE monitoring signals of multilevel shear behaviors can help understand the shear-friction mechanisms of rock joints.

scholarly journals Acoustic emission response characteristics of anthracitic coal under uniaxial compression

2020 ◽  
Author(s):  
Feng Du ◽  
Kai Wang ◽  
Guojun Zhang ◽  
Gongda Wang ◽  
Qian Zhang ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Wave Velocity ◽  
Coal Sample ◽  
Compression Process ◽  
Deformation And Failure ◽  
Response Characteristics ◽  
Fracture Evolution ◽  
Anthracite Coal ◽  
Coal Deformation

Abstract The damage evolution of coal is accompanied by the generation of acoustic emission (AE) signal. Through the analysis and research of AE response characteristics of coal deformation and failure, it is helpful to reveal the initiation, propagation and fracture evolution of micro cracks in coal. In this work, taking the anthracite coal as research object, the basic mechanical parameters of coal samples were obtained by ultrasonic tests and uniaxial compression experiments. Meanwhile, the AE response characteristics of coal samples during uniaxial compression were obtained through AE experiments. The results show that when the density is low, the wave velocity of coal sample decreases with the increase of density. When the density is higher than a certain value, the wave velocity of coal sample increases with the increase of density. Through the measurement of ultrasonic wave velocity, it is found that there are some non-uniformity and anisotropy in raw coal samples. The distribution of ring count, energy count and AE events with time in uniaxial compression process is approximately normal distribution. The AE events are concentrated in the elastic stage and yield stage, and the energy amplitude of AE events is higher in the plastic stage. Compared with the ring count and energy count, the AE events have good positioning function, which can better reflect the evolution of internal cracks in coal samples during uniaxial compression.

scholarly journals Acoustic Emission Response Characteristics of Anthracitic Coal under Uniaxial Compression

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Haiyan Wang ◽  
Gongda Wang ◽  
Guojun Zhang ◽  
Feng Du ◽  
Ji Ma
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Wave Velocity ◽  
Coal Sample ◽  
Compression Process ◽  
Deformation And Failure ◽  
Response Characteristics ◽  
Fracture Evolution ◽  
Anthracite Coal ◽  
Coal Deformation

The damage evolution of coal is accompanied by the generation of acoustic emission (AE) signal. Through the analysis and research of the AE response characteristics of coal deformation and failure, it is helpful to reveal the initiation, propagation, and fracture evolution of microcracks in coal. In this work, taking the anthracite coal as research object, the basic mechanical parameters of the coal samples were obtained by ultrasonic tests and uniaxial compression experiments. Meanwhile, the AE response characteristics of coal samples during uniaxial compression were obtained through AE experiments. The results show that when the density is low, the wave velocity of the coal sample decreases with the increase of density. When the density is higher than a certain value, the wave velocity of the coal sample increases with the increase of density. Through the measurement of ultrasonic wave velocity, it is found that there is some nonuniformity and anisotropy in raw coal samples. The ring counts, energy counts, and AE events with time in uniaxial compression process have approximately normal distribution. The AE events are concentrated in the elastic stage and yield stage, and the energy amplitude of AE events is higher in the plastic stage. Compared with the ring counts and energy counts, the AE events have a good positioning function, which can better reflect the evolution of internal cracks of coal samples during uniaxial compression.

scholarly journals An Experimental and Numerical Study on Acoustic Emission in the Process of Rock Damage at Different Stress Paths

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Dongxu Liang ◽  
Nong Zhang ◽  
Haoyu Rong
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Numerical Study ◽  
Rock Damage ◽  
Construction Design ◽  
Cyclic Loading And Unloading ◽  
Damage Process ◽  
Loading And Unloading ◽  
Loading Methods ◽  
Damage Processes

The study of the damage process of rock under external loads is good guidance for geotechnical construction design. The differences in rock damage processes and damage modes under different stress paths are rarely reported. To explore the effects of stress paths on rock damage processes, uniaxial compression experiments under three stress paths were conducted. Numerical simulation is also used to simulate the rock acoustic emission (AE) and fracture process. The results of the study indicate that the maximum acoustic emission events are at the peak of stress, and fractures are mainly formed at this stage. The peak of AE energy occurs before the peak of AE events. The damage pattern and fragmentation size of the rock are related to the way the stresses are loaded. It is noticed that there is appearance of a quiet period of AE events prior to the production of significant cracks. Minor damage to the rock is accompanied by the generation of bright white spots in the specimen, which is due to the high tensile or shear stress in the units. When the stress in these units exceeds their strength, the units break down and tiny cracks appear. As the external load increased, the cracks developed and penetrated, and the specimen was damaged. Under cyclic loading and unloading, the number of AE events increased significantly compared with the controlled displacement and controlled stress loading methods, and the radius of the AE circle became larger and the energy also increased, which indicates a greater degree of destruction of the rock under cyclic loading and unloading. The results of the study are of reference significance for rock crack propagation and fracture mode influenced by stress conditions and provide some guidance for construction design under different working conditions.

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