scholarly journals Tensile Properties Analysis Of 3D Flat-Knitted Inlay Fabric Reinforced Composites Using Acoustic Emission

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Jiangtao Tan ◽  
Gaoming Jiang ◽  
Guangjun Wu ◽  
Pibo Ma
Keyword(s):  
Acoustic Emission ◽  
Tensile Properties ◽  
Reinforced Composites ◽  
Fiber Breakage ◽  
Damage Mechanisms ◽  
Duration Time ◽  
Ae Energy ◽  
Matrix Fracture ◽  
Interlock Structure ◽  
Cumulative Ae Energy

Abstract In this work, based on the quasi-static tensile test and acoustic emission technology, the tensile properties of two types of three-dimensional flat-knitted inlay fabrics reinforced composites are investigated, and the acoustic emission characteristic parameters of various damage mechanisms are obtained. The transverse tensile process of specimens could be divided into the elastic stage, yield stage, and fracture stage. We found that, compared with the fluctuation of the stress-strain curve in the yield stage, weft insertion yarns in composite with interlock structure broke almost simultaneously, while the composite with plain stitch broke successively. The transverse and longitudinal tensile strength of the composite with interlock structure was 44.70% and 28.63% higher than the composite with plain structure, respectively. The SEM micrographs showed that the damage mechanism of the composites was matrix fracture, fiber-matrix debonding, and fiber breakage. The amplitude ranges of the three damage mechanisms were 50–65 dB, 65–80 dB, and 90–100 dB, respectively, and the frequency ranges were 35–114 kHz, 116–187 kHz, and 252–281 kHz, respectively. Fiber-matrix debonding and matrix fracture had large cumulative AE energy, numerous events, and long duration time, while fiber breakage had the characteristics of large amplitude, high frequency, low cumulative AE energy, few events, and short duration time.

scholarly journals Scale Effect on the Anisotropy of Acoustic Emission in Coal

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Honghua Song ◽  
Yixin Zhao ◽  
Yaodong Jiang ◽  
Jiehao Wang
Keyword(s):  
Acoustic Emission ◽  
Energy Dissipation ◽  
Scale Effect ◽  
Specimen Size ◽  
Exponential Equation ◽  
Volume Number ◽  
Ae Energy ◽  
Negative Exponential ◽  
Ae Counts ◽  
Cumulative Ae Energy

Acoustic emission (AE) in coal is anisotropic. In this paper, we investigate the microstructure-related scale effect on the anisotropic AE feature in coal at unconfined loading process. A series of coal specimens were processed with diameters of 25 mm, 38 mm, 50 mm, and 75 mm (height to diameter ratio of 2) and anisotropic angles of 0°, 15°, 30°, 45°, 60°, and 90°. The cumulative AE counts and energy dissipation increase with the specimen size, while the energy dissipation per AE count behaves in the opposite way. This may result from the increasing amount of both preexisting discontinuities and cracks (volume/number) needed for specimen failure and the lower energy dissipation AE counts generated by them. The effect of microstructures on the anisotropies of AE weakens with the increasing specimen size. The TRFD and its anisotropy reduce as the specimen size increases, and the reduction of fractal dimension is most pronounced at the anisotropic angle of 45°. The correlation between TRFD and cumulative AE energy in the specimens with different sizes are separately consistent with the negative exponential equation proposed by Xie and Pariseau. With the specimen size gain, the reduction of the TRFD weakens with the increasing amount of cumulative absolute AE energy.

Research on damage evolution of deep formation rock based on acoustic emission test

2020 ◽  
Vol 30 (1) ◽  
pp. 145-159
Author(s):  
Yong Tian ◽  
Rangang Yu ◽  
Yin Zhang ◽  
Xinbo Zhao
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Damage Evolution ◽  
Initial Moment ◽  
Damage Development ◽  
Loading Test ◽  
Cyclic Loading Test ◽  
Ae Energy ◽  
Rock Specimens ◽  
Cumulative Ae Energy

The study of rock damage evolution is of great significance in the field of underground engineering. In this paper, the damage development of deep formation rock was quantitatively evaluated by acoustic emission (AE) test. The Young’s modulus of the test rock specimens under ideal intact state was obtained by assuming a linear relationship between the AE rate parameter and the damage variation based on the rate process theory. Through the multi-stage cyclic loading test, the damage parameters corresponding to the peak stress of the previous stage were calculated by using the tangent modulus at the initial moment. The results showed that there was abrupt transition stage of damage development with the linear increase of stress. The damage parameter curves of rock specimens during loading process were obtained by using the method of cumulative AE energy, and the development trend of the curves was analyzed simply by combining the concepts of crack initiation stress and crack damage stress. Comparing the two methods of obtaining damage parameters by using cyclic loading test and cumulative AE energy, the results of them were highly consistent except for some deviation in the initial and final stages.

scholarly journals Acoustic Emission Experimental Research of the Damage Characteristics of Raw Coal under Different Loading and Unloading Rates

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Minbo Zhang ◽  
Li Cui ◽  
Wenjun Hu ◽  
Jinlei Du ◽  
Zhen Zhang ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Practical Significance ◽  
Emission Characteristic ◽  
Strain Rates ◽  
Characteristic Parameters ◽  
Energy Increase ◽  
Damage Models ◽  
Ae Energy ◽  
Ae Counts ◽  
Cumulative Ae Energy

In this study, triaxial load failure experiments of coal samples under different strain rates and different confining pressure unloading rates were carried out using an RTX-1000 rock triaxial apparatus, and the acoustic emission characteristic parameters of a Micro-II acoustic emission imaging acquisition instrument were used to study the acoustic emission characteristics and damage deformation law of coals under different conditions. Damage models were constructed on the basis of the characteristic parameters to analyze the damage law of coal samples. Experimental results show that the acoustic emission (AE) counts and AE energy of the coal samples decrease, but the peak AE counts and peak AE energy increase with the increase in strain rates. The cumulative AE counts decrease from 9902 times to 6899 times, the peak counts increase from 209 times to 431 times, the cumulative AE energy decreases from 6986 aJ to 3786 aJ, and the peak AE energy increases from 129 aJ to 312 aJ. The overall level of the AE count rates and the AE energy of the coal samples decrease, but the peak AE counts and peak AE energy increase with the increase in unloading rates. The cumulative AE counts decrease from 18,689 times to 16,842 times, the peak AE count rates increase from 245 times/s to 535 times/s, the cumulative AE energy decreases from 9846 aJ to 7430 aJ, and the peak energy increases from 257 aJ to 587 aJ. The damage models are constructed on the basis of AE counts, and the comparative experimental and theoretical curves are analyzed to obtain a higher fitness close to 1. The damage threshold increases from 0.30 to 0.50 and from 0.34 to 0.55, and the damage amount increases from 0.50 to 0.60 and from 0.34 to 0.62 with the increase in strain rates and unloading rates. The research results have practical significance for revealing the mechanism of disaster occurrence in actual engineering excavation and proposing engineering measures to prevent coal rock damage and disaster occurrence.

Sign in / Sign up

Export Citation Format

Share Document