In order to simultaneously take the advantages of magnesium and aluminum alloys, AZ80/A1 composite rods were produced using non-equal channel lateral extrusion （NECLE） process at different temperatures. Scanning ele...In order to simultaneously take the advantages of magnesium and aluminum alloys, AZ80/A1 composite rods were produced using non-equal channel lateral extrusion （NECLE） process at different temperatures. Scanning electron microscope （SEM） and energy dispersive spectrometer （EDS） tests as well as the shear punch test were employed to study the quality and strength of the bond between the two alloys. It was found that the process temperature was an important factor affecting the level of interfacial bonding, such that increasing the temperature from 250 to 300℃ has improved the strength by 37% and the thickness of the bond between the layers by 4.5%. Moreover, this temperature rise reduced the maximum required forming load by 13%. However, the hardness tests showed that this increase in the process temperature resulted in 4% decrease in the hardness of the composite bar.展开更多
Non-equal channel lateral extrusion（NECLE） is a new process that can be used to attain higher grain refinement in comparison with equal channel lateral extrusion（ECLE）. The die design for this process was numerica...Non-equal channel lateral extrusion（NECLE） is a new process that can be used to attain higher grain refinement in comparison with equal channel lateral extrusion（ECLE）. The die design for this process was numerically and experimentally studied. After finding a good correlation between the numerical and experimental results, more comprehensive FE analyses were carried out. Different die geometrical parameters were considered and their effects on the induced plastic strain, stress distribution, velocity field and forming load of the process were investigated. It was found that by this process with a suitable set of die geometrical parameters, higher induced effective strain and more homogeneous strain distribution could be achieved in comparison with ECLE operation.展开更多
By introducing a water depth connecting formula, the hydraulic equations in the dividing channel system were coupled and the relation of discharge distribution between the branches of the dividing channels can be yiel...By introducing a water depth connecting formula, the hydraulic equations in the dividing channel system were coupled and the relation of discharge distribution between the branches of the dividing channels can be yielded. In this manner, a numerical model for the confluent channels was established to study the variation of backwater effects with the parameters in the channel junction. The meeting of flood peaks in the mainstream and tributary can be analyzed with this model.The flood peak meeting is found to be a major factor for the extremely high water level in the mainstream during the 1998 Yangtze River flood. Subsequently the variations of discharge distribution and water level with channel parameters between each branch in this system were studied as well. As a result, flood evolution caused by Jingjiang River shortcut and sediment deposition in the entrance of dividing channels of the Yangtze River may be qualitatively elucidated.It is suggested to be an effective measure for flood mitigation to enhance regulation capability of reservoirs available upstream of the tributaries and harness branch entrance channels.展开更多
This study provided a new configuration of the 180-deg round turned channel with a perforated divider, as well as numerically investigated the effect of perforations, including the diameter of perforation and the ange...This study provided a new configuration of the 180-deg round turned channel with a perforated divider, as well as numerically investigated the effect of perforations, including the diameter of perforation and the angel of perforation, on the fluid flow and heat transfer. The numerical results appeared in good agreement with previous experimental data under the same operating conditions. The results indicated that large size and positive angle of perforation changed the fluid flow pattern and the local Nusselt-number distribution fundamentally. It is noteworthy that a more uniform distribution of Nusselt-number was achieved by increasing the diameter of perforation.展开更多
文摘In order to simultaneously take the advantages of magnesium and aluminum alloys, AZ80/A1 composite rods were produced using non-equal channel lateral extrusion （NECLE） process at different temperatures. Scanning electron microscope （SEM） and energy dispersive spectrometer （EDS） tests as well as the shear punch test were employed to study the quality and strength of the bond between the two alloys. It was found that the process temperature was an important factor affecting the level of interfacial bonding, such that increasing the temperature from 250 to 300℃ has improved the strength by 37% and the thickness of the bond between the layers by 4.5%. Moreover, this temperature rise reduced the maximum required forming load by 13%. However, the hardness tests showed that this increase in the process temperature resulted in 4% decrease in the hardness of the composite bar.
文摘Non-equal channel lateral extrusion（NECLE） is a new process that can be used to attain higher grain refinement in comparison with equal channel lateral extrusion（ECLE）. The die design for this process was numerically and experimentally studied. After finding a good correlation between the numerical and experimental results, more comprehensive FE analyses were carried out. Different die geometrical parameters were considered and their effects on the induced plastic strain, stress distribution, velocity field and forming load of the process were investigated. It was found that by this process with a suitable set of die geometrical parameters, higher induced effective strain and more homogeneous strain distribution could be achieved in comparison with ECLE operation.
文摘By introducing a water depth connecting formula, the hydraulic equations in the dividing channel system were coupled and the relation of discharge distribution between the branches of the dividing channels can be yielded. In this manner, a numerical model for the confluent channels was established to study the variation of backwater effects with the parameters in the channel junction. The meeting of flood peaks in the mainstream and tributary can be analyzed with this model.The flood peak meeting is found to be a major factor for the extremely high water level in the mainstream during the 1998 Yangtze River flood. Subsequently the variations of discharge distribution and water level with channel parameters between each branch in this system were studied as well. As a result, flood evolution caused by Jingjiang River shortcut and sediment deposition in the entrance of dividing channels of the Yangtze River may be qualitatively elucidated.It is suggested to be an effective measure for flood mitigation to enhance regulation capability of reservoirs available upstream of the tributaries and harness branch entrance channels.
文摘This study provided a new configuration of the 180-deg round turned channel with a perforated divider, as well as numerically investigated the effect of perforations, including the diameter of perforation and the angel of perforation, on the fluid flow and heat transfer. The numerical results appeared in good agreement with previous experimental data under the same operating conditions. The results indicated that large size and positive angle of perforation changed the fluid flow pattern and the local Nusselt-number distribution fundamentally. It is noteworthy that a more uniform distribution of Nusselt-number was achieved by increasing the diameter of perforation.
