scholarly journals Use of Acoustic Emission for the Detection of Brittle Rock Failure under Various Loading Rates

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Hai-qing Shuang ◽  
Shu-gang Li ◽  
Lang Liu ◽  
Gao-feng Chen ◽  
Ki-Il Song
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Damage Mechanics ◽  
Loading Rate ◽  
Uniaxial Compression Test ◽  
Internal Damage ◽  
Loading Rates ◽  
Initial Damage ◽  
Natural Rock ◽  
Positioning Technique

Acoustic emission has a direct correspondence to the internal damage of a material. To determine the effects of the loading rate on the mechanical properties of rock, the initial damage was characterized using the acoustic emission technique when a uniaxial preloading was imposed on a cylindrical rock sample. On this basis, the uniaxial compression test was conducted on sandstone that contains initial damage induced under a range of loading rates. The effects of the initial damage and loading rate on the mechanical properties of rock were analyzed. The uniaxial preloading generated randomly distributed microcracks in the natural rock. The results showed that the acoustic emission and positioning technique can characterize accurately the damage and its position due to preloading. The development of microcracks was found to be strongly dependent on the loading rate. Moreover, the loading rate accelerated the degradation of the rock strength. The effects of the loading rate and initial damage on the mechanical properties of rock are a complicated coupled process. From the experimental test result, a constitutive equation was constructed based on the damage mechanics.

scholarly journals Acoustic Emission Features of Anthracite under the Influence of Loading Rate

2021 ◽  
Vol 45 (5) ◽  
pp. 393-397
Author(s):  
Xiaohua Jin ◽  
Jiyu Zheng
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Brittle Failure ◽  
Energy Analysis ◽  
Loading Rate ◽  
Deformation And Failure ◽  
Loading Rates ◽  
Energy Accumulation ◽  
Acoustic Emitter ◽  
Uniaxial Compressive Stress

Loading rate is an important impactor of the mechanical properties, as well as the deformation and failure mode of coal and rock. Using an RMT-301 rock mechanics tester and a Soft Island acoustic emitter, uniaxial compression and acoustic emission (AE) tests were carried out on coal samples under different loading rates. The results show that uniaxial compressive stress-strain curves of the rock samples each consist of four segments: compaction, elasticity, yield, and failure. As the loading rate increased from 0.01mm/s to 0.02mm/s, the peak strength rose, the post-peak deformability dropped, the brittle failure features of anthracite became more obvious, more AE events took place, and AE frequency increased. Energy analysis shows that, the faster the loading rate, the larger the AE count, the faster the energy accumulation, but the fewer the total energy accumulation.

scholarly journals Mechanical Properties of Bump-Prone Coal with Different Porosities and Its Acoustic Emission-Charge Induction Characteristics under Uniaxial Compression

2019 ◽  
Vol 2019 ◽  
pp. 1-18 ◽  
Author(s):  
Xin Ding ◽  
Xiaochun Xiao ◽  
Xiangfeng Lv ◽  
Di Wu ◽  
Jun Xu
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Quantitative Description ◽  
Volumetric Strain ◽  
Geological Structure ◽  
Uniaxial Compression Test ◽  
Theoretical Derivation ◽  
Initial Damage ◽  
Charge Induction

Discreteness of mechanical property affected by the intimal damage, which emerged with various degrees of material composition and geological structure, is the difference in porosity macroscopically. Although various porosities directly affect fracture activity, damage evolution and mechanical behaviour of coal bring on the bump-prone assessment error, and disaster happened “ahead of time” in deep underground energy source exploration, little research to date has focused on them. In this paper, the mechanical properties of bump-prone coal samples with different porosities were studied by uniaxial compression test and the initial damage caused by gangue and organic fracture in coal observed by CT. The result indicated that the evolution of coal strength and the logarithm of porosity were expressed by a linear negative correlation and the elastic modules decreased with the initial damage increased. A new quantitative description of damage variables is established by theoretical derivation to reflect the process of cracks formation and expiation in coal, based on volumetric strain and initial porosity. According to the Mohr–Coulomb principle, the effective stress of coal sample with higher the porosity is more likely to reach the shear strength and destruction. The amplitudes and accumulation of AE energy and charge pulse indeed vary with the stress loading stages and strength. The frequency of AE waveform is dominated in three bands (1∼50 kHz, 100∼150 kHz, and 175∼200 kHz) and that of charge induction had one frequency band 1∼100 Hz, and the amplitudes of time domain and main frequency components increased with stress improved. Both of them originated from cracks and belong to homologous signals, crack development bound to be accompanied by stress wavelet, not necessarily free charge; meanwhile, charge pulse being emerged means there must be cracks interaction and the acoustic emission signals are generated prior to charge induction.

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.

scholarly journals Study of Acoustic Emission and Mechanical Characteristics of Coal Samples under Different Loading Rates

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Huamin Li ◽  
Huigui Li ◽  
Baobin Gao ◽  
Dongjie Jiang ◽  
Junfa Feng
Keyword(s):  
Acoustic Emission ◽  
Elasticity Modulus ◽  
Loading Rate ◽  
Peak Stress ◽  
Test System ◽  
Strong Impact ◽  
Peak Strain ◽  
Compression Tests ◽  
Loading Rates ◽  
The Relationship

To study the effect of loading rate on mechanical properties and acoustic emission characteristics of coal samples, collected from Sanjiaohe Colliery, the uniaxial compression tests are carried out under various levels of loading rates, including 0.001 mm/s, 0.002 mm/s, and 0.005 mm/s, respectively, using AE-win E1.86 acoustic emission instrument and RMT-150C rock mechanics test system. The results indicate that the loading rate has a strong impact on peak stress and peak strain of coal samples, but the effect of loading rate on elasticity modulus of coal samples is relatively small. When the loading rate increases from 0.001 mm/s to 0.002 mm/s, the peak stress increases from 22.67 MPa to 24.99 MPa, the incremental percentage is 10.23%, and under the same condition the peak strain increases from 0.006191 to 0.007411 and the incremental percentage is 19.71%. Similarly, when the loading rate increases from 0.002 mm/s to 0.005 mm/s, the peak stress increases from 24.99 MPa to 28.01 MPa, the incremental percentage is 12.08%, the peak strain increases from 0.007411 to 0.008203, and the incremental percentage is 10.69%. The relationship between acoustic emission and loading rate presents a positive correlation, and the negative correlation relation has been determined between acoustic emission cumulative counts and loading rate during the rupture process of coal samples.

Loading Rate Effects during Indentation on Strength of Glass

2018 ◽  
Vol 768 ◽  
pp. 8-12
Author(s):  
Xiu Min Gao ◽  
Yi Wang Bao ◽  
Guang Lin Nie
Keyword(s):  
Acoustic Emission ◽  
Work Stress ◽  
Brittle Material ◽  
Loading Rate ◽  
Time Effect ◽  
Spherical Indentation ◽  
Loading Rates ◽  
Local Strength ◽  
Rate Effects ◽  
Testing Approach

The spherical indentation combined with acoustic emission was used to evaluate the local strength of glass, which is a nondestructive testing approach. However, stress time effect on the local strength of glass during spherical indentation has not been studied before. In the present work, stress time effect was investigated by examining the local strength of unstrengthened and strengthened glass at different loading rates. It is discovered that the local strength of glass increased greatly with the loading rate, which confirmed the time dependence of the fracture on glass. As a typical brittle material, the discreteness of strength date of glass measured by spherical indentation was also analyzed to evaluate the strength of glass correctly.

scholarly journals Acoustic Emission Characteristics and Failure Mechanism of Fractured Rock under Different Loading Rates

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Yongzheng Zhang ◽  
Gang Wang ◽  
Yujing Jiang ◽  
Shugang Wang ◽  
Honghua Zhao ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Failure Mechanism ◽  
Strain Energy ◽  
Loading Rate ◽  
Fractured Rock ◽  
Acoustic Emissions ◽  
Biaxial Compression ◽  
Particle Model ◽  
Energy Rate ◽  
Loading Rates

To study the loading rate dependence of acoustic emissions and the failure mechanism of fractured rock, biaxial compression tests performed on granite were numerically simulated using the bonded particle model in Particle Flow Code (PFC). Uniaxial tests on a sample containing a single open fracture were simulated under different loading rates ranging from 0.005 to 0.5 m/s. Our results demonstrate the following. (1) The overall trends of stress and strain changes are not affected by the loading rate; the loading rate only affects the strain required to reach each stage. (2) The strain energy rate and acoustic emission (AE) events are affected by the loading rate in fractured rock. With an increase in the loading rate, AE events and the strain energy rate initially increase and then decrease, forming a fluctuating trend. (3) Under an external load, the particles within a specimen are constantly squeezed, rotated, and displaced. This process is accompanied by energy dissipation via the production of internal tensile and shear cracks; their propagation and coalescence result in the formation of a macroscopic rupture zone.

scholarly journals Acoustic Emission and Failure Modes for Coal-Rock Structure under Different Loading Rates

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Ning Wang ◽  
Yingqian Xu ◽  
Dengyuan Zhu ◽  
Nan Wang ◽  
Benfu Yu
Keyword(s):  
Acoustic Emission ◽  
Energy Release ◽  
Failure Modes ◽  
Loading Rate ◽  
Failure Process ◽  
Coal Mass ◽  
Transient Growth ◽  
Loading Rates ◽  
Rock Structure ◽  
Coal Rock

Coal bump refers to a sudden catastrophic failure of coal seam and usually causes serious damages to underground mining facilities and staff. Considering the combined coal-rock structure for coal bumps, failure process and acoustic emission (AE) characteristics of combined coal-sandstone samples under different loading rates were studied by uniaxial compression tests, and three basic failure modes and bump proneness for coal-rock structure were obtained. The following conclusions are drawn: (1) when loading rate was relatively low, plastic deformation of coal mass fully developed, while surface cracks of coal mass was not apparent and slip along the transfixion crack occurred in the postpeak stage; (2) with the increase in loading rate, surface tensile cracks developed into splitting cracks at the end of the prepeak stage and throughout the postpeak stage, and brittle failure finally happened due to the release of nonlinear step-shaped energy or one-time strain energy release of upper rock mass, resulting in the damage of internal bearing structure and weakening of bearing capacity; (3) the deformation and failure process of combined samples showed obvious phases, and corresponding AE energy release rate could be divided into periodic linear growth and transient growth, while the cumulative energy of AE events has multiple peak points and transient growth with the increase of loading rate; (4) it was demonstrated that two distinct frequency bands existed in AE events, which were about 50 kHz and 150 kHz, and the distribution of AE events near 50 kHz was larger and stronger, representing the main frequency range of cracks in coal mass. According to the damage characteristics and AE parameters for combined samples, an brittle model for coal-rock structure with mutation characteristics was proposed, and three basic failure modes for the combined structure with the increase of loading rate were progressive shear failure, splitting failure, and structural failure, respectively.

The Influence of Loading Rate on the Interfacial Fracture Toughness of Carbon Fiber-Metal Laminates Based on Magnesium Alloy

2011 ◽  
Vol 328-330 ◽  
pp. 1373-1376 ◽  
Author(s):  
Gong Zhi Zhu ◽  
Chang Liang Zheng ◽  
Xiao Feng Lu
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Magnesium Alloy ◽  
Carbon Fiber ◽  
Loading Rate ◽  
Interfacial Fracture ◽  
Interfacial Fracture Toughness ◽  
Fiber Metal Laminates ◽  
Loading Rates ◽  
Fiber Metal

Glass fiber reinforced aluminum alloy laminates, such as ARALL, GLARE are used widely for aeronautics and astronautics industry with excellent mechanical properties such as high specific strength, specific Young’s Modulus, high damage tolerance, high resistance to fatigue crack growth and good impact resistance. In order to obtain better mechanical properties, aluminum alloy plates and glass fibers were replaced by magnesium alloy plates and carbon fibers to get carbon fiber-metal laminates based on magnesium alloy. Single cantilever beams were used to examine the influence of loading rate on the interfacial fracture toughness of carbon fiber-metal laminates based on magnesium alloy. The results show that crack propagation is stable at low loading rates whereas unstable at high rates. And loading rates have slight influence on interfacial fracture toughness at low rates range from 1mm/min to 1000mm/min. The fracture toughness at high rates in impact tests is greater than at low rate.

scholarly journals Research on Acoustic Emission and Electromagnetic Emission Characteristics of Rock Fragmentation at Different Loading Rates

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Fujun Zhao ◽  
Yu Li ◽  
Zhouyuan Ye ◽  
Yong Fan ◽  
Siping Zhang ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Loading Rate ◽  
Electromagnetic Emission ◽  
Rock Fragmentation ◽  
Loading Rates ◽  
Peak Intensity ◽  
Wave Forms ◽  
Show Jumping ◽  
Peak Count ◽  
Good Agreement

The relationships among the generation of acoustic emission, electromagnetic emission, and the fracture stress of rock grain are investigated, which are based on the mechanism of acoustic emission and electromagnetic emission produced in the process of indenting rock. Based on the relationships, the influence of loading rate on the characteristics of acoustic emission and electromagnetic emission of rock fragmentation is further discussed. Experiment on rock braking was carried out with three loading rates of 0.001 mm/s, 0.01 mm/s, and 0.1 mm/s. The results show that the phenomenon of acoustic emission and electromagnetic emission is produced during the process of loading and breaking rock. The wave forms of the two signals and the curve of the cutter indenting load show jumping characteristics. Both curves have good agreement with each other. With the increase of loading rate, the acoustic emission and electromagnetic emission signals are enhanced. Through analysis, it is found that the peak count rate, the energy rate of acoustic emission, the peak intensity, the number of pulses of the electromagnetic emission, and the loading rate have a positive correlation with each other. The experimental results agree with the theoretical analysis. The proposed studies can lead to an in-depth understanding of the rock fragmentation mechanism and help to prevent rock dynamic disasters.

scholarly journals Energy Analysis Method for Uniaxial Compression Test of Sandstone under Static and Quasi-Dynamic Loading Rates

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Zhixi Liu ◽  
Guangming Zhao ◽  
Xiangrui Meng ◽  
Ruofei Zhang ◽  
Dong Chunliang ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Uniaxial Compression ◽  
Compression Test ◽  
Elastic Energy ◽  
Loading Rate ◽  
Uniaxial Compression Test ◽  
Input Energy ◽  
Analysis Method ◽  
Compression Tests ◽  
Loading Rates

To investigate the energy evolution characteristics of sandstone under static-quasi-dynamic loading rates (1.0 × 10−3, 5.0 × 10−3, 1.0 × 10−2, 5.0 × 10−2, and 1.0 × 10−1 mm/s), the uniaxial compression tests, the uniaxial cyclic loading-unloading tests, and the uniaxial incrementally cyclic loading-unloading tests were conducted under five different loading rates. Through analysis of the elastic energy of the uniaxial cyclic loading-unloading test and the uniaxial incremental cyclic loading-unloading test, show that the impact of the loading rate and the cycle numbers on the elastic energy is less. Hence, we can deem that when the loads of the uniaxial incremental cyclic loading-unloading test and the uniaxial compression test are equal, the elastic energy of the two also equals. The energy in the uniaxial compression tests analyzed by the uniaxial incrementally cyclic loading-unloading test show that elastic energy increased linearly when the input energy increased under different loading rates. Through the linear energy storage law and the uniaxial incremental cyclic loading and unloading test, it is possible to analyze the energy in the uniaxial compression test at any loading rates. The results show that the greater the loading rate, the greater the peak elastic energy and peak input energy. But when the load is equal, the greater the loading rate, the smaller the input energy and elastic energy. Compared with traditional methods, the new energy analysis method is accurate and simple. Meanwhile, based on energy dissipation, the damage of rock during uniaxial compression tests was studied.

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