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Tensile Properties of Aluminum Alloy Bolt-Sphere Joints under Elevated Temperatures
Hongbo Liu,Ao Gu,Zhi-Hua Chen 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.2
Aluminum alloy bolt-sphere joint is one of the major nodes in aluminum alloy space grid structures. It has been applied in many big projects. In this study, computation methods of mechanical properties and bearing capacity of aluminum alloy bolt-sphere joints in fire are proposed by combining experimental research and theoretical analysis. Results demonstrate that: 1) The tensile strength of aluminum alloy bolt-sphere joints in fire is related to the tensile strength of stainless-steel bolt and the tensile strength seal plate joint. 2) The stainless-steel bolt develops two failure modes, namely, breakage failure of cord and pulling-out failure of screw in fire. 3) The seal plate joint in fire has three tensile failure modes, namely, tensile-shearing combined failure of seal plate at the annular compression position, shear failure of seal plate, and tensile failure of the aluminum alloy tube at the seal plate border. 4) The tensile strength of the stainless-steel bolt begins to decrease significantly when the temperature reaches 300°C. 5) The tensile strength of the seal plate joint begins to decrease sharply when the temperature reaches 200°C. 6) The formula to calculate bearing capacity of aluminum alloy bolt-sphere joints in fire is proposed based on experimental results.
The Effect of Impeller Indent Distance on the Performance of Vortex Pumps
Lei DAI,Lei GU,Jun WANG,Xiang AO,Xiaobo ZHU 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.1
Low efficiency is an urgent problem to be solved for vortex pumps due to large number of vortices and backflows. This paper concentrates on the performance improvement of vortex pumps caused by changing the indent distance of the impeller. First, a complete numerical model was established by selecting the optimal length of inlet and outlet and appropriate mesh quantity. Then, the reliability of this model was validated by comparing simulation results with experimental data. Based on this model, the internal flows of vortex pumps with different impeller indent distances were observed in simulations and the fitted curves of head and efficiency were created. Finally, the cause of the performance improvement was demonstrated by analyzing the flow field in vortex pumps.