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.

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 The Effect of High Loading Rate on the Behaviour and Mechanical Properties of Coal-Rock Combined Body

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Fengqiang Gong ◽  
Hao Ye ◽  
Yong Luo
Keyword(s):  
Incident Energy ◽  
Loading Rate ◽  
Peak Stress ◽  
High Loading ◽  
Peak Strain ◽  
Rate Range ◽  
Loading Rates ◽  
High Loading Rate ◽  
Coal Rock ◽  
Second Peak

In order to investigate the high loading rate effect on the behaviour and mechanical properties of coal-rock combined body, the dynamic compressive tests were conducted by using the Split-Hopkinson Pressure Bar (SHPB) device under the loading rate range from 2.7×105 MPa/s to 4.0×105 MPa/s. The stress-strain curves, dynamic peak stress and strain, elastic modulus, and energy distribution law of coal-rock combined body under different loading rates were analyzed and discussed. The results show that the dynamic stress-strain curves of coal-rock combined body have a double-peak feature under high loading rate range, which can be divided into the initial bearing stage, the bearing decline stage, the bearing enhance stage, and the unstable stage. The first peak stress of the coal-rock combined body is independent of the loading rate, while the dynamic compressive strength (the second peak stress) and dynamic peak strain (the second peak strain) have a strong loading rate effect and will generally increase linearly with the loading rate. The first and second elastic moduli of coal-rock combined body are not sensitive to the loading rate. With the increase of the loading rate, the incident energy and reflective energy of coal-rock combined body increase rapidly, while the change of transmitted energy is very small. The absorption energy ratio of the coal-rock combined body shows a good linear law with the incident energy under different loading rates.

Effect of Dynamic Loading on Mechanical Properties of Concrete

2012 ◽  
Vol 568 ◽  
pp. 147-153
Author(s):  
Ji Wei Deng ◽  
Chang Wu Liu ◽  
Jian Feng Liu
Keyword(s):  
Elastic Modulus ◽  
Loading Rate ◽  
Concrete Strength ◽  
Test System ◽  
Dynamic Loads ◽  
Structural Safety ◽  
Peak Strain ◽  
Compression Tests ◽  
Sensitive Material ◽  
Stress Strain

Concrete structures have to bear dynamic loads in daily work, strength and deformation characteristics of concrete under dynamic loads differ from the characteristics under static loads, and this difference may become a key factor to restrict the structural safety under certain conditions. Using the MTS815 test system, the dynamic uniaxial compression tests of concrete specimens were conducted. The mechanical characteristic parameters of strength, elastic modulus, peak strain and the stress-strain curves at different loading rates of concrete specimens have been studied. The results reveal that concrete is a rate-sensitive material, as a small loading rate may lead to the rapid growth of strength; the variation rule of peak strain is not obvious with the increase of loading rate, thus the peak strain can be regarded as a fixed value in actual projects; the higher the loading rate is, the greater the concrete strength and the elastic modulus are; the elastic modulus increases essentially due to the improvement of structural stiffness; concrete specimens with the same mix proportion have similar stress-strain curves and the loading rate has little effect on the shape of the curve.

scholarly journals Influence of Decoupled Charge Structure and Filler on the Blasting Effect

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Yiping Zhang ◽  
Yi Luo ◽  
Sipeng Wan ◽  
Yingxiang Tian ◽  
Huanchao Ding ◽  
...  
Keyword(s):  
High Speed ◽  
Peak Stress ◽  
Test System ◽  
Peak Strain ◽  
Charge Structure ◽  
Changing Trend ◽  
Decoupling Coefficient ◽  
Geometric Elements ◽  
The Relationship ◽  
Selection Of

This study compared models of specimens with different filler media and decoupled charge structures in terms of the blasting effect. The test system combined a high-speed camera and high-speed static strain test analyzer. A physical model of a concrete single-borehole decoupled charge structure was designed to study the geometric elements of the blasting funnel, flyrock launch velocity, peak strain values, and distribution of the gravel lumpiness. The experimental results showed that for the same decoupling coefficient, when expandable polystyrene foam (EPS) was used as the filling medium, the radius, depth, and volume of the blasting funnel of the model specimen were larger, the flyrock launch velocity was slower, the peak stress of the specimen was higher, and the distribution of gravel lumpiness was more even. The relationship between the experimental index and the decoupling coefficient follows the changing trend of first increasing and then decreasing or first decreasing and then increasing. With air and EPS as the filling media, the concrete model specimens could achieve optimal blasting effects at decoupling coefficients of 1.83 and 1.69, respectively. The results confirm the feasibility and practicability of using EPS as a filler and can provide guidance and an experimental basis for the selection of the decoupling coefficient and filling medium in blasting engineering.

scholarly journals Application and Effect of Loading Rates on Coal Sample Failure

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Genwei Li ◽  
Shuaifeng Lu ◽  
Sifei Liu ◽  
Jing Liu ◽  
Peng Shi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Shear Failure ◽  
Loading Rate ◽  
Coal Pillar ◽  
Test System ◽  
Tensile Failure ◽  
Compression Tests ◽  
Pillar Stability ◽  
Loading Rates ◽  
The Stability

In order to evaluate the coal pillar stability in recovery of residual room pillars under different mining rates, this paper studies the influence of loading rate on the mechanical properties of the coal body. The uniaxial compression tests of coal samples in Yangcheng area at different loading rates were carried out with the MTS815 electrohydraulic servo rock mechanics test system. The stress-strain curves and the evolution characteristics of AE signals were analyzed. At same time, the mechanism of damage and failure of specimens are also discussed. The results show the following. (1) With the increase in loading rate, the ultimate stress and ultimate strain of specimens decrease first and then increase. (2) Loading rate has a significant effect on the stability adjustment of specimens. With the decrease in loading rate, the earlier the stress adjustment is, the larger the adjustment range is, and the failure mode changes from shear failure to tensile failure. (3) In addition, when the loading rate increases, the AE evolves from continuous dense to discrete catastrophe, which indicates that the failure of the sample at a larger loading rate is sudden, which is not conducive to the maintenance of the stability of the coal pillar. (4) Finally, the failure mechanism of the specimen structure under different loading rates is obtained, and the improvement measures for the effect of mining velocity of working face on the stability of coal pillar are put forward. The results reveal the loading rate effect of mechanical properties of coal and provide a reference for controlling the stability of the residual coal pillar.

Comparison Analysis on the Mechanical Properties of HSC and NSC after the Action of High Temperatures

2014 ◽  
Vol 1014 ◽  
pp. 49-52
Author(s):  
Xiao Ping Su
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
High Temperatures ◽  
High Strength Concrete ◽  
Elasticity Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
High Strength ◽  
Peak Strain ◽  
Strength Concrete

With the wide application of high strength concrete in the building construction,the risk making concrete subject to high temperatures during a fire is increasing. Comparison tests on the mechanical properties of high strength concrete (HSC) and normal strength concrete (NSC) after the action of high temperature were made in this article, which were compared from the following aspects: the peak stress, the peak strain, elasticity modulus, and stress-strain curve after high temperature. Results show that the laws of the mechanical properties of HSC and NSC changing with the temperature are the same. With the increase of heating temperature, the peak stress and elasticity modulus decreases, while the peak strain grows rapidly. HSC shows greater brittleness and worse fire-resistant performance than NSC, and destroys suddenly. The research and evaluation on the fire-resistant performance of HSC should be strengthened during the structural design and construction on the HSC buildings.

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.

Tests on Effects of Loading Rate on Modulus and Strength of Sandstone

2014 ◽  
Vol 1065-1069 ◽  
pp. 214-218
Author(s):  
Chun Hui Zhang ◽  
Hong Liang Yue ◽  
Lai Gui Wang
Keyword(s):  
Compressive Strength ◽  
Linear Relationship ◽  
Uniaxial Compression ◽  
Loading Rate ◽  
Strength Degradation ◽  
Peak Strength ◽  
Exponential Relationship ◽  
Loading Rates ◽  
Average Modulus ◽  
The Relationship

For studying on the effects of loading rate on modulus and strength of sandstone, uniaxial compression experiment of the samples, from Balikun mine, was performed at different loading rates. The influence of loading rate on average modulus, uniaxial compressive strength and post-peak strength degradation angle was analyzed, and the results indicate that:: The average modulus of sandstone samples increases with loading rate increasing; the both almost obey linear relationship. The peak strength of sandstone grows with the increase of loading rate; there is an approximately exponential relationship between the two. With loading rate increasing, the post-peak strength degradation angle decreases; the relationship between the both is approximately exponential.

scholarly journals ACOUSTIC EMISSION AND DAMAGE CHARACTERISTICS OF ANTHRACITE UNDER DIFFERENT CONDITIONS

2021 ◽  
Vol 55 (2) ◽  
pp. 213-218
Author(s):  
Jiyu Zheng ◽  
Xiaohua Jin ◽  
Kunyun Tian ◽  
Yinbo Zhou
Keyword(s):  
Acoustic Emission ◽  
Coal Sample ◽  
Characteristic Curve ◽  
Great Influence ◽  
Acoustic Emissions ◽  
Slow Increase ◽  
Loading Rates ◽  
The Relationship ◽  
Damage Characteristic ◽  
Peak Count

Acoustic emission (AE) can be used to observe the process of coal fracture propagation. Based on a press and acoustic-emission platform, the damage and acoustic-emission characteristics of anthracite with different loading rates, water amounts and sizes were studied. The results show that there is less acoustic emission in the initial compression stage of coal; acoustic emission is more active in the transition from elastic deformation to plastic deformation, which is manifested in the following aspects: the faster the loading rate, the higher is the number of acoustic-emission events; the peak count of acoustic emissions of a saturated-coal sample is significantly lower than that of a natural-coal sample. Coal samples and large coal samples emit even more sounds. Based on the normalization of acoustic-emission counts, the relationship between damage variables and stress-strain is studied, and it is characterized by an initial slow increase, followed by a rapid increase; however, different factors have a great influence on the damage-characteristic curve. The research results have a certain guiding significance for the coal and rock disaster prediction.

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