On-site investigations consistently show that the rock burst inherent to coal seams varies greatly with coal seam thickness.In this study,impact factors related to coal seam thickness and surrounding rock strength wer...On-site investigations consistently show that the rock burst inherent to coal seams varies greatly with coal seam thickness.In this study,impact factors related to coal seam thickness and surrounding rock strength were analyzed and a corresponding rock burst risk assessment method was constructed.The model reflects the influence of coal seam thickness on the stress distribution of surrounding rock at the roadway.Based on the roadway excavation range,a stress distribution model of surrounding roadway rock is established and the influence of coal seam thickness on rock burst risk is analyzed accordingly.The proposed rock burst risk assessment method is based on the equivalent surrounding rock strength and coal seam bursting liability.The proposed method was tested in a 3500 mining area to find that it yields rock burst risk assessment results as per coal seam thickness that are in accordance with real-world conditions.The results presented here suggest that coal seam thickness is a crucial factor in effective rock burst risk assessment.展开更多
A self-designed setup of modified sloping cooling/shearing process was made to prepare the semisolid Al-3wt%Mg alloy. A three-dimensional simulation model was established for the analysis of preparing the semisolid Al...A self-designed setup of modified sloping cooling/shearing process was made to prepare the semisolid Al-3wt%Mg alloy. A three-dimensional simulation model was established for the analysis of preparing the semisolid Al-3wt%Mg alloy. Through simulation and experiment, it is shown that the sloping angle of the plate greatly affects temperature and velocity distributions, and the temperature and velocity of the alloy at the exit of the sloping plate increase with the increase of the sloping angle. The alloy temperature decreases linearly from the pouring mouth to the exit. The alloy temperature at the exit increases obviously with the increase of pouring temperature. To prepare the semisolid Al-3wt%Mg alloy with good quality, the sloping angle θ=45° is reasonable, and the pouring temperature is suggested to be designed above 650-660℃ but under 700℃.展开更多
In order to optimize the Castex process of AS wire, the systematic experiments have been done for different process parameters with self-made DZJ-II 350 Castex machine. The parameters, such as casting temperature of a...In order to optimize the Castex process of AS wire, the systematic experiments have been done for different process parameters with self-made DZJ-II 350 Castex machine. The parameters, such as casting temperature of aluminum, flow of cooling water, extrusion ratio and the gap between the surface of wheel and that of the mould, have been mainly studied. The results show that with the increase of casting temperature or rotating speed of wheel the measured length of liquid metal zone increases too. However, the length of liquid metal zone decreases with the increase of the flow of cooling water. Moreover, the relationship between the extrusion ratio and the extrusion power is studied.展开更多
基金supported and financed from Special Funds for Basic Research Business Fees of China Academy of Safety Science and Technology(Nos.2016JBKY16,2017JBKY05)National Key Research and Development Program of China(No.2017YFC0804603)Subject of Beijing Science and Technology Commission(No.Z171100002317008)
文摘On-site investigations consistently show that the rock burst inherent to coal seams varies greatly with coal seam thickness.In this study,impact factors related to coal seam thickness and surrounding rock strength were analyzed and a corresponding rock burst risk assessment method was constructed.The model reflects the influence of coal seam thickness on the stress distribution of surrounding rock at the roadway.Based on the roadway excavation range,a stress distribution model of surrounding roadway rock is established and the influence of coal seam thickness on rock burst risk is analyzed accordingly.The proposed rock burst risk assessment method is based on the equivalent surrounding rock strength and coal seam bursting liability.The proposed method was tested in a 3500 mining area to find that it yields rock burst risk assessment results as per coal seam thickness that are in accordance with real-world conditions.The results presented here suggest that coal seam thickness is a crucial factor in effective rock burst risk assessment.
基金This work was financially supported by the National Natural Science Foundation of China (No.50604007)the Natural ScienceFoundation of Liaoning Province, China (No.20062016)
文摘A self-designed setup of modified sloping cooling/shearing process was made to prepare the semisolid Al-3wt%Mg alloy. A three-dimensional simulation model was established for the analysis of preparing the semisolid Al-3wt%Mg alloy. Through simulation and experiment, it is shown that the sloping angle of the plate greatly affects temperature and velocity distributions, and the temperature and velocity of the alloy at the exit of the sloping plate increase with the increase of the sloping angle. The alloy temperature decreases linearly from the pouring mouth to the exit. The alloy temperature at the exit increases obviously with the increase of pouring temperature. To prepare the semisolid Al-3wt%Mg alloy with good quality, the sloping angle θ=45° is reasonable, and the pouring temperature is suggested to be designed above 650-660℃ but under 700℃.
文摘In order to optimize the Castex process of AS wire, the systematic experiments have been done for different process parameters with self-made DZJ-II 350 Castex machine. The parameters, such as casting temperature of aluminum, flow of cooling water, extrusion ratio and the gap between the surface of wheel and that of the mould, have been mainly studied. The results show that with the increase of casting temperature or rotating speed of wheel the measured length of liquid metal zone increases too. However, the length of liquid metal zone decreases with the increase of the flow of cooling water. Moreover, the relationship between the extrusion ratio and the extrusion power is studied.
