The effects of heat input on the microstructures and mechanical properties of tungsten inert gas （TIG） butt-welded AZ31/MB3 dissimilar Mg alloys joint were investigated by microstructural observations, microhardness...The effects of heat input on the microstructures and mechanical properties of tungsten inert gas （TIG） butt-welded AZ31/MB3 dissimilar Mg alloys joint were investigated by microstructural observations, microhardness testing and tensile testing. The results reveal that with the increase of heat input, the width of welding seam increases obviously and the grains both in the fusion zone and the heat affected zone coarsen during TIG welding process. The tensile strength of butt-welded joint increases with the increase of heat input and the maximum joining strength of 242 MPa is obtained with wedding current of 90 A. However, lots of welding pores occur with the further increase of heat input, which results in the decrease of joining strength. It is experimentally demonstrated that robust joint can be obtained by TIG welding process.展开更多
Attitude adjustment is a key link in the installation process of underwater facilities in deep water.To solve this problem,an omnidirectional spirit level for deep water was developed.The sealing principle of the spir...Attitude adjustment is a key link in the installation process of underwater facilities in deep water.To solve this problem,an omnidirectional spirit level for deep water was developed.The sealing principle of the spirit level and the principle of deep-water pressure resistance are analyzed,and the threaded connection strength is checked.The mechanical simulation verifies that the spirit level can withstand the pressure of 2000 m water depth,and the water pressure test is carried out for 30 min in a 20 MPa hyperbaric chamber.After the experiment is completed,the appearance of the spirit level is intact and there is no leakage.The experiment results show that the deep-water omnidirectional spirit level can be used in the deep sea within 2000 m.展开更多
Conventional vacuum control in a milking system is accomplished by using a vacuum pump, sized for the maximum air flows into the milking system, running at a full speed. The difference between the pump capacity and th...Conventional vacuum control in a milking system is accomplished by using a vacuum pump, sized for the maximum air flows into the milking system, running at a full speed. The difference between the pump capacity and the necessary flow of air is compensated by allowing air to enter the system through a regulator. The solution presented in this paper uses a VFD （variable frequency driver） in order to drive the vacuum pump at a controlled speed, so that the air removed equals the air entering the milking system. The VFD technology is able to adjust the rate of air removal from the milking system, by changing the speed of the vacuum pump motor. The VFD is controlled by a computer using a virtual instrument in order to emulate a PID （proportion integration differentiation） regulator. The tests aimed to evaluate the vacuum regulator characteristics and vacuum stability. A statistical analysis of the experimental results was performed and it showed that there was a significant difference between the experimental results obtained for the two methods of vacuum regulation （with vacuum regulator and VFD controller respectively）. The experimental results proved that the used of the VFD controller led to a higher vacuum stability in terms of the error between the set vacuum value and the achieved values.展开更多
基金Project（51575067） supported by the National Natural Science Foundation of China Project（2012ZX04010-081） supported by the Major and Special Project of Ministry of Science and Technology, China
文摘The effects of heat input on the microstructures and mechanical properties of tungsten inert gas （TIG） butt-welded AZ31/MB3 dissimilar Mg alloys joint were investigated by microstructural observations, microhardness testing and tensile testing. The results reveal that with the increase of heat input, the width of welding seam increases obviously and the grains both in the fusion zone and the heat affected zone coarsen during TIG welding process. The tensile strength of butt-welded joint increases with the increase of heat input and the maximum joining strength of 242 MPa is obtained with wedding current of 90 A. However, lots of welding pores occur with the further increase of heat input, which results in the decrease of joining strength. It is experimentally demonstrated that robust joint can be obtained by TIG welding process.
基金National key R&D Program of China(No.2017YFF0108104)Tianjin key R&D Program(No.20YFZCGX00550)。
文摘Attitude adjustment is a key link in the installation process of underwater facilities in deep water.To solve this problem,an omnidirectional spirit level for deep water was developed.The sealing principle of the spirit level and the principle of deep-water pressure resistance are analyzed,and the threaded connection strength is checked.The mechanical simulation verifies that the spirit level can withstand the pressure of 2000 m water depth,and the water pressure test is carried out for 30 min in a 20 MPa hyperbaric chamber.After the experiment is completed,the appearance of the spirit level is intact and there is no leakage.The experiment results show that the deep-water omnidirectional spirit level can be used in the deep sea within 2000 m.
文摘Conventional vacuum control in a milking system is accomplished by using a vacuum pump, sized for the maximum air flows into the milking system, running at a full speed. The difference between the pump capacity and the necessary flow of air is compensated by allowing air to enter the system through a regulator. The solution presented in this paper uses a VFD （variable frequency driver） in order to drive the vacuum pump at a controlled speed, so that the air removed equals the air entering the milking system. The VFD technology is able to adjust the rate of air removal from the milking system, by changing the speed of the vacuum pump motor. The VFD is controlled by a computer using a virtual instrument in order to emulate a PID （proportion integration differentiation） regulator. The tests aimed to evaluate the vacuum regulator characteristics and vacuum stability. A statistical analysis of the experimental results was performed and it showed that there was a significant difference between the experimental results obtained for the two methods of vacuum regulation （with vacuum regulator and VFD controller respectively）. The experimental results proved that the used of the VFD controller led to a higher vacuum stability in terms of the error between the set vacuum value and the achieved values.
