scholarly journals Effect of cyclic wetting–drying on tensile mechanical behavior and microstructure of clay-bearing sandstone

2021 ◽  
Author(s):  
Pingye Guo ◽  
Juan Gu ◽  
Yi Su ◽  
Jiong Wang ◽  
Zhanwen Ding
Keyword(s):  
Tensile Strength ◽  
Acoustic Emission ◽  
High Speed ◽  
Mineral Content ◽  
Emission Characteristics ◽  
Single Cycle ◽  
Strength Tests ◽  
Crack Propagation Process ◽  
Emission System ◽  
Penetration Time

AbstractThe understanding of the weakening mechanism of tensile strength of rock subjected to cyclic wetting-drying is critical for rock engineering. Tensile strength tests were conducted on a total of 35 sandstone specimens with different wetting-drying cycles. The crack propagation process and acoustic emission characteristics of the tested samples were obtained through a high-speed camera and acoustic emission system. The results indicate that the tensile strength is observably reduced after cyclic wetting-drying, and the extent of the reduction is not only related to the number of wetting-drying cycle, but also closely related to the clay mineral content of the sample. In addition, as the cycles of wetting-drying increase, the effect of each single cycle on tensile strength get reduced until it becomes constant. Moreover, the crack initiation and penetration time is prolonged as the number of wetting-drying cycle increases, which indicates that cyclic wetting-drying weakens the rock stiffness and enhances the ductility of sandstone. Meanwhile, the acoustic emission characteristics of the tested samples further confirmed the ductile behaviour of the sandstone samples with increasing wetting-drying cycle. Furthermore, through the analysis of the microstructure and mineral composition of the samples with different wetting-drying cycles, it is concluded that the main weakening mechanisms of sandstones containing clay minerals are frictional reduction, chemical and corrosive deterioration.

scholarly journals Effect of cyclic wetting-drying on tensile mechanical behavior and microstructure of clay-bearing sandstone

2020 ◽  
Author(s):  
Pingye Guo ◽  
Gu Juan ◽  
Su Yi ◽  
Jiong Wang ◽  
Zhanwen Ding
Keyword(s):  
Tensile Strength ◽  
Acoustic Emission ◽  
High Speed ◽  
Mineral Content ◽  
Emission Characteristics ◽  
Single Cycle ◽  
Strength Tests ◽  
Crack Propagation Process ◽  
Emission System ◽  
Penetration Time

Abstract The understanding of the weakening mechanism of tensile strength of rock subjected to cyclic wetting-drying is critical for rock engineering. Tensile strength tests were conducted on a total of 35 sandstone specimens with different wetting-drying cycles. The crack propagation process and acoustic emission characteristics were obtained through a high-speed camera and acoustic emission system. The results indicate that the tensile strength is observably reduced after cyclic wetting-drying, and the extent of the reduction is not only related to the number of wetting-drying cycle, but also closely related to the clay mineral content of the sample. In addition, as the cycles of wetting-drying increase, the effect of each single cycle on tensile strength is getting smaller and smaller until becoming constant. Moreover, the crack initiation and penetration time is prolonged as the number of wetting-dry cycle increases, which indicates that cyclic wetting-drying weakens the rock stiffness and enhances the ductility of sandstone. Meanwhile, the acoustic emission characteristics during the experiment further confirmed this phenomenon. Furthermore, through the analysis of the microstructure and mineral composition of the samples with different wetting-drying cycles, it is concluded that the main weakening mechanisms of sandstones containing clay minerals are frictional reduction, chemical and corrosive deterioration.

scholarly journals Effect of cyclic wetting-drying on tensile mechanical behavior and microstructure of clay-bearing sandstone

2020 ◽  
Author(s):  
Pingye guo ◽  
Gu Juan ◽  
Su Yi ◽  
Jiong Wang ◽  
Zhanwen Ding
Keyword(s):  
Tensile Strength ◽  
Acoustic Emission ◽  
High Speed ◽  
Mineral Content ◽  
Emission Characteristics ◽  
Single Cycle ◽  
Strength Tests ◽  
Crack Propagation Process ◽  
Emission System ◽  
Penetration Time

Abstract The understanding of the weakening mechanism of tensile strength of rock subjected to cyclic wetting-drying is critical for rock engineering. Tensile strength tests were conducted on a total of 35 sandstone specimens with different wetting-drying cycles. The crack propagation process and acoustic emission characteristics of the tested samples were obtained through a high-speed camera and acoustic emission system. The results indicate that the tensile strength is observably reduced after cyclic wetting-drying, and the extent of the reduction is not only related to the number of wetting-drying cycle, but also closely related to the clay mineral content of the sample. In addition, as the cycles of wetting-drying increase, the effect of each single cycle on tensile strength get reduced until it becomes constant.. Moreover, the crack initiation and penetration time is prolonged as the number of wetting-drying cycle increases, which indicates that cyclic wetting-drying weakens the rock stiffness and enhances the ductility of sandstone. Meanwhile, the acoustic emission characteristics of the tested samples further confirmed the ductile behaviour of the sandstone samples with increasing wetting-drying cycle. Furthermore, through the analysis of the microstructure and mineral composition of the samples with different wetting-drying cycles, it is concluded that the main weakening mechanisms of sandstones containing clay minerals are frictional reduction, chemical and corrosive deterioration.

scholarly journals The effect of liquid nitrogen cooling on coal cracking and mechanical properties

2018 ◽  
Vol 36 (6) ◽  
pp. 1609-1628 ◽  
Author(s):  
Chengzheng Cai ◽  
Feng Gao ◽  
Yugui Yang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Acoustic Emission ◽  
Liquid Nitrogen ◽  
Wave Velocity ◽  
Count Rate ◽  
Initial State ◽  
Nitrogen Injection ◽  
Strength Tests ◽  
Liquid Nitrogen Cooling

Liquid nitrogen is a type of super-cryogenic fluid, which can cause the reservoir temperature to decrease significantly and thereby induce formation rock damage and cracking when it is injected into the wellbore as fracturing fluid. An experimental set-up was designed to monitor the acoustic emission signals of coal during its contact with cryogenic liquid nitrogen. Ultrasonic and tensile strength tests were then performed to investigate the effect of liquid nitrogen cooling on coal cracking and the changes in mechanical properties thereof. The results showed that acoustic emission phenomena occurred immediately as the coal sample came into contact with liquid nitrogen. This indicated that evident damage and cracking were induced by liquid nitrogen cooling. During liquid nitrogen injection, the ring-down count rate was high, and the cumulative ring-down counts also increased rapidly. Both the ring-down count rate and the cumulative ring-down counts during liquid nitrogen injection were much greater than those in the post-injection period. Liquid nitrogen cooling caused the micro-fissures inside the coal to expand, leading to a decrease in wave velocity and the deterioration in mechanical strength. The wave velocity, which was measured as soon as the sample was removed from the liquid nitrogen (i.e. the wave velocity was recorded in the cooling state), decreased by 14.46% on average. As the cryogenic samples recovered to room temperature, this value increased to 18.69%. In tensile strength tests, the tensile strengths of samples in cooling and cool-treated states were (on average) 17.39 and 31.43% less than those in initial state. These indicated that both during the cooling and heating processes, damage and cracking were generated within these coal samples, resulting in the acoustic emission phenomenon as well as the decrease in wave velocity and tensile strength.

scholarly journals Conformity of Physical Characteristics of Imported Tires with Government Standards: A Case Study

2004 ◽  
Vol 1 (1) ◽  
pp. 1
Author(s):  
N.T. Ratrout ◽  
S. Anwar Basha ◽  
H. I. Al-Abdul Wahhab ◽  
K. A. Al-Ofi
Keyword(s):  
Tensile Strength ◽  
High Speed ◽  
Visual Inspection ◽  
Performance Tests ◽  
Tensile Strength Test ◽  
Dimension Measurement ◽  
Strength Tests ◽  
Speed Performance ◽  
Almost All

The Saudi Arabian Standards Organization, SASO, has established a set of tests that all passenger car tires have to pass in order to be allowed into the Country. These tests are: visual inspection, dimension measurement, bead unseating, tensile strength and elongation, aging, endurance, and high speed performance tests. This paper describes the application of the first five tests on eight different brands of tires that are taken to represent the categories of “frequently failed” and “infrequently failed” tires in the country. The results showed that the dimensions of almost all the tested tires were somewhat different from those documented in the SASO standards. On the other hand, all the tested tires passed the bead unseating and strength tests. All tires in the “frequently failed” category failed the tensile strength test. In contrast, all tires from the “infrequently failed” category passed this test. The average values of the test for these two tire categories were statistically different at a 95% confidence level.  

Monitoring Composite Fiber Failure Using Acoustic Emission System, Vibration Analyzer, and High-Speed Video Recording

2020 ◽  
Vol 56 (12) ◽  
pp. 960-970
Author(s):  
N. A. Makhutov ◽  
V. I. Ivanov ◽  
A. G. Sokolova ◽  
I. E. Vasil’ev ◽  
D. V. Chernov ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
High Speed ◽  
Video Recording ◽  
Composite Fiber ◽  
Fiber Failure ◽  
High Speed Video ◽  
System Vibration ◽  
Emission System
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