Rock brittleness directly affects reservoir fracturing and its evaluation is essential for establishing fracturing conditions prior to reservoir reforming. Dynamic and static brittleness data were collected from silts...Rock brittleness directly affects reservoir fracturing and its evaluation is essential for establishing fracturing conditions prior to reservoir reforming. Dynamic and static brittleness data were collected from siltstones of the Qingshankou Formation in Songliao Basin. The brittle-plastic transition was investigated based on the stress-strain relation. The results suggest that the brittleness indices calculated by static elastic parameters are negatively correlated with the stress drop coefficient and the brittleness index B2, defined as the average of the normalized Young＇s modulus and Poisson＇s ratio, is strongly correlated with the stress drop. The brittleness index B2, Young＇s modulus, and Poisson＇s ratio correlate with the brittle minerals content; that is, quartz, carbonates, and pyrite. We also investigated the correlation between pore fluid and porosity and dynamic brittle characteristic based on index B2. Pore fluid increases the plasticity of rock and reduces brittleness; moreover, with increasing porosity, rock brittleness decreases. The gas-saturated siltstone brittleness index is higher than that in oil- or water-saturated siltstone; the difference in the brittleness indices of oil- and water-saturated siltstone is very small. By comparing the rock mechanics and ultrasonic experiments, we find that the brittleness index obtained from the rock mechanics experiments is smaller than that obtained from the ultrasonic experiments; nevertheless, both decrease with increasing porosity as well as their differences. Ultrasonic waves propagate through the rock specimens without affecting them, whereas rock mechanics experiments are destructive and induce microcracking and porosity increases; consequently, the brittleness of low-porosity rocks is affected by the formation of internal microcrack systems.展开更多
In this research,a series of biaxial compression and biaxial fatigue tests were conducted to investigate the mechanical behaviors of marble and sandstone under biaxial confinements.Experimental results demonstrate tha...In this research,a series of biaxial compression and biaxial fatigue tests were conducted to investigate the mechanical behaviors of marble and sandstone under biaxial confinements.Experimental results demonstrate that the biaxial compressive strength of rocks under biaxial compression increases firstly,and subsequently decreases with increase of the intermediate principal stress.The fatigue failure characteristics of the rocks in biaxial fatigue tests are functions of the peak value of fatigue loads,the intermediate principal stress and the rock lithology.With the increase of the peak values of fatigue loads,the fatigue lives of rocks decrease.The intermediate principal stress strengthens the resistance ability of rocks to fatigue loads except considering the strength increasing under biaxial confinements.The fatigue lives of rocks increase with the increase of the intermediate principal stress under the same ratio of the fatigue load and their biaxial compressive strength.The acoustic emission(AE)and fragments studies showed that the sandstone has higher ability to resist the fatigue loads compared to the marble,and the marble generated a greater number of smaller fragments after fatigue failure compared to the sandstone.So,it can be inferred that the rock breaking efficiency and rock burst is higher or severer induced by fatigue loading than that induced by monotonous quasi-static loading,especially for hard rocks.展开更多
[ Objective] The aim was to study on influence of ultrasonic on broken effect of foodborne polluting strains. [Method ] Escherichia coli, Staphylococcus aureus, and Aspergillus niger in different concentrations were t...[ Objective] The aim was to study on influence of ultrasonic on broken effect of foodborne polluting strains. [Method ] Escherichia coli, Staphylococcus aureus, and Aspergillus niger in different concentrations were tested in different ultrasonic powers and times for the broken effects.[ Result ] Eschedchia coil and Staphylococcus aureus were more sensitive to ultrasonication and the broken rates were as high as 96%. Aspergillus niger, however, was not so sensitive and the broken rate was only about 40%. The optimum parameters, including ultrasonic power, ultrasonic time and OD, of Escherichia coli were 600 W, 14 rain and 0.997, of Staphylococcus aureus were 600 W, 15 min and 1.440, and of Aspergillus ni- ger were 700 W, 20 min and 0.893, respectively. [ Conclusion] The research provided references for application of ultrasonic technology in food sterilization.展开更多
The performances of fme-crystalline zirconia ceramics in workpiece ultrasonic vibration grinding （WUVG） and conventional grinding （CG） with diamond wheel were researched. The effects of WUVG and CG on material rem...The performances of fme-crystalline zirconia ceramics in workpiece ultrasonic vibration grinding （WUVG） and conventional grinding （CG） with diamond wheel were researched. The effects of WUVG and CG on material removal rate, grinding forces, surface roughness and microstructure of zirconia ceramic were investigated. Experimental results indicated that： （1） The material removal rate （MRR） in ultrasonic grinding process is two times as large as that of in conventional grinding. The material removal rate increases with increasing grinding depth in both ultrasonic grinding and conventional grinding. （2） The ultrasonic vibration grinding force is lower than that of conventional grinding force, and the increase of the worktable speed leads to a decrease of the grinding force, while the grinding force increases with larger grinding depth in both WUVG and CG. （3） The surface of ultrasonic vibration grinding has no spur and build-up edge and its surface roughness is smaller than that of CG significantly. Surface quality of WUVG is superior to that of conventional grinding, it is easy for ultrasonic vibration grinding that material removal mechanism is ductile grinding.展开更多
基金financially supported by Jiangsu Specially-Appointed Professors ProgramThe Fundamental Research Funds for the Central Universities(No.2016B13114)
文摘Rock brittleness directly affects reservoir fracturing and its evaluation is essential for establishing fracturing conditions prior to reservoir reforming. Dynamic and static brittleness data were collected from siltstones of the Qingshankou Formation in Songliao Basin. The brittle-plastic transition was investigated based on the stress-strain relation. The results suggest that the brittleness indices calculated by static elastic parameters are negatively correlated with the stress drop coefficient and the brittleness index B2, defined as the average of the normalized Young＇s modulus and Poisson＇s ratio, is strongly correlated with the stress drop. The brittleness index B2, Young＇s modulus, and Poisson＇s ratio correlate with the brittle minerals content; that is, quartz, carbonates, and pyrite. We also investigated the correlation between pore fluid and porosity and dynamic brittle characteristic based on index B2. Pore fluid increases the plasticity of rock and reduces brittleness; moreover, with increasing porosity, rock brittleness decreases. The gas-saturated siltstone brittleness index is higher than that in oil- or water-saturated siltstone; the difference in the brittleness indices of oil- and water-saturated siltstone is very small. By comparing the rock mechanics and ultrasonic experiments, we find that the brittleness index obtained from the rock mechanics experiments is smaller than that obtained from the ultrasonic experiments; nevertheless, both decrease with increasing porosity as well as their differences. Ultrasonic waves propagate through the rock specimens without affecting them, whereas rock mechanics experiments are destructive and induce microcracking and porosity increases; consequently, the brittleness of low-porosity rocks is affected by the formation of internal microcrack systems.
基金Projects(51774326,41807259)supported by the National Natural Science Foundation of ChinaProject(MDPC201917)supported by Mining Disaster Prevention and Control Ministry Key Laboratory at Shandong University of Science and Technology,China。
文摘In this research,a series of biaxial compression and biaxial fatigue tests were conducted to investigate the mechanical behaviors of marble and sandstone under biaxial confinements.Experimental results demonstrate that the biaxial compressive strength of rocks under biaxial compression increases firstly,and subsequently decreases with increase of the intermediate principal stress.The fatigue failure characteristics of the rocks in biaxial fatigue tests are functions of the peak value of fatigue loads,the intermediate principal stress and the rock lithology.With the increase of the peak values of fatigue loads,the fatigue lives of rocks decrease.The intermediate principal stress strengthens the resistance ability of rocks to fatigue loads except considering the strength increasing under biaxial confinements.The fatigue lives of rocks increase with the increase of the intermediate principal stress under the same ratio of the fatigue load and their biaxial compressive strength.The acoustic emission(AE)and fragments studies showed that the sandstone has higher ability to resist the fatigue loads compared to the marble,and the marble generated a greater number of smaller fragments after fatigue failure compared to the sandstone.So,it can be inferred that the rock breaking efficiency and rock burst is higher or severer induced by fatigue loading than that induced by monotonous quasi-static loading,especially for hard rocks.
文摘[ Objective] The aim was to study on influence of ultrasonic on broken effect of foodborne polluting strains. [Method ] Escherichia coli, Staphylococcus aureus, and Aspergillus niger in different concentrations were tested in different ultrasonic powers and times for the broken effects.[ Result ] Eschedchia coil and Staphylococcus aureus were more sensitive to ultrasonication and the broken rates were as high as 96%. Aspergillus niger, however, was not so sensitive and the broken rate was only about 40%. The optimum parameters, including ultrasonic power, ultrasonic time and OD, of Escherichia coli were 600 W, 14 rain and 0.997, of Staphylococcus aureus were 600 W, 15 min and 1.440, and of Aspergillus ni- ger were 700 W, 20 min and 0.893, respectively. [ Conclusion] The research provided references for application of ultrasonic technology in food sterilization.
基金Supported by the Henan Extraordinary Ability of China (No.0421001200)
文摘The performances of fme-crystalline zirconia ceramics in workpiece ultrasonic vibration grinding （WUVG） and conventional grinding （CG） with diamond wheel were researched. The effects of WUVG and CG on material removal rate, grinding forces, surface roughness and microstructure of zirconia ceramic were investigated. Experimental results indicated that： （1） The material removal rate （MRR） in ultrasonic grinding process is two times as large as that of in conventional grinding. The material removal rate increases with increasing grinding depth in both ultrasonic grinding and conventional grinding. （2） The ultrasonic vibration grinding force is lower than that of conventional grinding force, and the increase of the worktable speed leads to a decrease of the grinding force, while the grinding force increases with larger grinding depth in both WUVG and CG. （3） The surface of ultrasonic vibration grinding has no spur and build-up edge and its surface roughness is smaller than that of CG significantly. Surface quality of WUVG is superior to that of conventional grinding, it is easy for ultrasonic vibration grinding that material removal mechanism is ductile grinding.
