A fatigue failure criterion for predicting the fatigue life of notched orthotropic fiber reinforced plasties (FRP) plates based on the concept of stress field intensity (SFI) near the notch root is subjected to furt...A fatigue failure criterion for predicting the fatigue life of notched orthotropic fiber reinforced plasties (FRP) plates based on the concept of stress field intensity (SFI) near the notch root is subjected to further experiments. The investigation is accomplished by obtaining experimental data on the notched specimens of glass fiber reinforced plastics (GFRP) with edged notches under tension tension cyclic loading. The process of initiation and growth of fatigue damage near the notch root is measured by means of the optic system with a computer controlled display (CCD) camera. The experimental results show that the number of loading cycles required to initiate fatigue damage is governed by the stress field intensity.展开更多
According to geological conditions of No. 3 and No. 4 coal seams （namely A3 and B4） of the Pan＇er coal mine and the parameters of panels 11223, 11224, and 11124 with fully-mechanical coal mining, we built 2D simila...According to geological conditions of No. 3 and No. 4 coal seams （namely A3 and B4） of the Pan＇er coal mine and the parameters of panels 11223, 11224, and 11124 with fully-mechanical coal mining, we built 2D similar material simulation and FLAC3D numerical simulation models to investigate the development of mining-induced stress and the extraction effect of pressure-relief gas with large height and upward mining. Based on a comprehensive analysis of experimental data and observations, we obtained the deformation and breakage characteristics of strata overlying the coal seam, the development patterns of the mining-induced stress and fracture, and the size of the stress-relief area. The stress-relief effect was investigated and analyzed in consideration with mining height and three thick hard strata. Because of the group of three hard thick strata located in the main roof and the residual stress of mined panel 11124, the deformation, breakage, mining-induced stress and fracture development, and the stress-relief coefficient were discontinuous and asymmetrical. The breakage angle of the overlying strata, and the compressive and expansive zones of coal deformation were mainly controlled by the number, thickness, and strength of the hard stratum. Compared with the value of breakage angle derived by the traditional empirical method, the experimental value was lower than the traditional results by 3°-4°below the hard thick strata group, and by 13°-19° above the hard thick strata group. The amount of gas extracted from floor drainage roadway of B4 over 17 months was variable and the amount of gas per month differed considerably, being much smaller when panel 11223 influenced the area of the three hard thick strata. Generally, the stress-relief zone of No. 4 coal seam was small under the influence of the hard thick strata located in the main roof, which played an important role in delaying the breakage time and increasing the breakage space. In this study we gained understanding of the stress-relief mechanism influenced by the hard thick roof. The research results and engineering practice show that the main roof of the multiple hard thick strata is a critical factor in the design of panel layout and roadways for integrated coal exploitation and gas extraction, provides a theoretical basis for safe and high-efficient mining of coal resources.展开更多
The overall objective of this study was to provide guidance for proper design of profile-walled pipe. Data from buried pipe tests on HDPE pipes with thirteen different profiles were included in the study. These tests ...The overall objective of this study was to provide guidance for proper design of profile-walled pipe. Data from buried pipe tests on HDPE pipes with thirteen different profiles were included in the study. These tests were run in the soil cell at Utah State University. Also, parallel plate tests were also completed on the pipe samples. Data from 39 buried pipe tests were analyzed. The buried tests were at 75, 85 and 95 percent of standard Proctor density. This paper summarizes the results of that study and focuses on the tests buried in 85 percent dense soil. In addition to the experimental data, a portion of this paper focuses on finite element analysis results to confirm and extend the results from the physical tests. Design limits are recommended for several dimensionless parameters that describe profile geometry. One of the significant conclusions of this study was that pipes with profiles that perform well when buried in soil also perform well in a parallel plate tests. The identities of the pipe manufacturers are not disclosed, and pipes are only described in terms of basic parameters such as cross-sectional area and area moments of inertia.展开更多
文摘A fatigue failure criterion for predicting the fatigue life of notched orthotropic fiber reinforced plasties (FRP) plates based on the concept of stress field intensity (SFI) near the notch root is subjected to further experiments. The investigation is accomplished by obtaining experimental data on the notched specimens of glass fiber reinforced plastics (GFRP) with edged notches under tension tension cyclic loading. The process of initiation and growth of fatigue damage near the notch root is measured by means of the optic system with a computer controlled display (CCD) camera. The experimental results show that the number of loading cycles required to initiate fatigue damage is governed by the stress field intensity.
基金Acknowledgments This work is supported by the National Nature Science Foundation of China （51374011）.
文摘According to geological conditions of No. 3 and No. 4 coal seams （namely A3 and B4） of the Pan＇er coal mine and the parameters of panels 11223, 11224, and 11124 with fully-mechanical coal mining, we built 2D similar material simulation and FLAC3D numerical simulation models to investigate the development of mining-induced stress and the extraction effect of pressure-relief gas with large height and upward mining. Based on a comprehensive analysis of experimental data and observations, we obtained the deformation and breakage characteristics of strata overlying the coal seam, the development patterns of the mining-induced stress and fracture, and the size of the stress-relief area. The stress-relief effect was investigated and analyzed in consideration with mining height and three thick hard strata. Because of the group of three hard thick strata located in the main roof and the residual stress of mined panel 11124, the deformation, breakage, mining-induced stress and fracture development, and the stress-relief coefficient were discontinuous and asymmetrical. The breakage angle of the overlying strata, and the compressive and expansive zones of coal deformation were mainly controlled by the number, thickness, and strength of the hard stratum. Compared with the value of breakage angle derived by the traditional empirical method, the experimental value was lower than the traditional results by 3°-4°below the hard thick strata group, and by 13°-19° above the hard thick strata group. The amount of gas extracted from floor drainage roadway of B4 over 17 months was variable and the amount of gas per month differed considerably, being much smaller when panel 11223 influenced the area of the three hard thick strata. Generally, the stress-relief zone of No. 4 coal seam was small under the influence of the hard thick strata located in the main roof, which played an important role in delaying the breakage time and increasing the breakage space. In this study we gained understanding of the stress-relief mechanism influenced by the hard thick roof. The research results and engineering practice show that the main roof of the multiple hard thick strata is a critical factor in the design of panel layout and roadways for integrated coal exploitation and gas extraction, provides a theoretical basis for safe and high-efficient mining of coal resources.
文摘The overall objective of this study was to provide guidance for proper design of profile-walled pipe. Data from buried pipe tests on HDPE pipes with thirteen different profiles were included in the study. These tests were run in the soil cell at Utah State University. Also, parallel plate tests were also completed on the pipe samples. Data from 39 buried pipe tests were analyzed. The buried tests were at 75, 85 and 95 percent of standard Proctor density. This paper summarizes the results of that study and focuses on the tests buried in 85 percent dense soil. In addition to the experimental data, a portion of this paper focuses on finite element analysis results to confirm and extend the results from the physical tests. Design limits are recommended for several dimensionless parameters that describe profile geometry. One of the significant conclusions of this study was that pipes with profiles that perform well when buried in soil also perform well in a parallel plate tests. The identities of the pipe manufacturers are not disclosed, and pipes are only described in terms of basic parameters such as cross-sectional area and area moments of inertia.
