The influence of the slip mode on the microstructure evolution and compressive flow behavior at different strains in an extruded dilute Mg−0.5Bi−0.5Sn−0.5Mn alloy was analyzed through electron backscatter diffraction,...The influence of the slip mode on the microstructure evolution and compressive flow behavior at different strains in an extruded dilute Mg−0.5Bi−0.5Sn−0.5Mn alloy was analyzed through electron backscatter diffraction,X-ray diffraction,transmission electron microscopy,and hot compression tests.The results showed that at a low strain of 0.05,the basal,pyramidaland<c+a>slip modes were simultaneously activated.Nevertheless,at the middle stage of deformation(strain of 0.1,0.2 and 0.5),theslip mode was difficult to be activated and<c+a>slip mode became dominant.The deformation process between strains of 0.2 and 0.5 was primarily characterized by the softening effect resulting from the simultaneous occurrence of continuous dynamic recrystallization and discontinuous dynamic recrystallization.Ultimately,at strain of 0.8,a dynamic equilibrium was established,with the flow stress remaining constant due to the interplay between the dynamic softening brought about by discontinuous dynamic recrystallization and the work-hardening effect induced by the activation of the basalslip mode.展开更多
The authors introduce a new Large Eddy Simulation model in a channel, based on the projection on finite element spaces as filtering operation in its variationM form, for a given triangulation （Th）h〉0. The eddy visc...The authors introduce a new Large Eddy Simulation model in a channel, based on the projection on finite element spaces as filtering operation in its variationM form, for a given triangulation （Th）h〉0. The eddy viscosity is expressed in terms of the friction velocity in the boundary layer due to the wall, and is of a standard sub grid-model form outside the boundary layer. The mixing length scale is locally equal to the grid size. The computational domain is the channel without the linear sub-layer of the boundary layer. The no-slip boundary condition （or BC for short） is replaced by a Navier （BC） at the computational wall. Considering the steady state case, the authors show that the variational finite element model they have introduced, has a solution （Vh,Ph）h〉O that converges to a solution of the steady state Navier-Stokes equation with Navier BC.展开更多
Oscillation of fluid flow may cause the dynamic instability of nanotubes,which should be valued in the design of hanoelectromechanical systems.Nonlinear dynamic instability of the fluid-conveying nanotube transporting...Oscillation of fluid flow may cause the dynamic instability of nanotubes,which should be valued in the design of hanoelectromechanical systems.Nonlinear dynamic instability of the fluid-conveying nanotube transporting the pulsating harmonic flow is studied.The nanotube is composed of two surface layers made of functionally graded materials and a viscoelastic interlayer.The nonlocal strain gradient model coupled with surface effect is established based on Gurtin-Murdoch's surface elasticity theory and nonlocal strain gradient theory.Also,the size-dependence of the nanofluid is established.by the slip flow model.The stability boundary is obtained by the two-step perturbation-Galerkin truncation-Incremental harmonic balance(IHB)method·and compared with the linear solutions by using Bolotin's method.Further,the Runge-Kutta method is utilized to plot the amplitudefrequency bifurcation curves inside/outside the region.Results reveal the influence of nonlocal stress,strain gradient,surface elasticity and slip flow on the response.Results also suggest that the stability boundary obtained by the IHB method represents two bifurcation points when sweeping from high frequency to low frequency.Differently,when sweeping to high.frequency,there exists a hysteresis boundary where amplitude jump will occur.展开更多
In this paper, steady incompressible micropolar fluid flow through a non-uniform channel with multiple stenoses is considered. Assuming the stenoses to be mild and using the slip boundary condition, the equations gove...In this paper, steady incompressible micropolar fluid flow through a non-uniform channel with multiple stenoses is considered. Assuming the stenoses to be mild and using the slip boundary condition, the equations governing the flow of the proposed model are solved, and closed-form expressions for the flow characteristics （resistance to flow and wall shear stress） are derived. The effects of different parameters on these flow characteristics are analyzed. It is observed that both the resistance to the flow and the wall shear stress increase with the heights of the stenoses and the slip parameter; but decrease with the Darcy number, b^rthermore, the effects of the wall exponent parameter, the cross-viscosity coefficient and the micropolar parameter on the flow characteristics are discussed.展开更多
基金supported by the National Natural Science Foundation of China (No.51901153)Shanxi Scholarship Council of China (No.2019032)+2 种基金Natural Science Foundation of Shanxi Province,China (No.202103021224049)the Shanxi Zhejiang University New Materials and Chemical Research Institute Scientific Research Project,China (No.2022SX-TD025)the Open Project of Salt Lake Chemical Engineering Research Complex,Qinghai University,China (No.2023-DXSSKF-Z02)。
文摘The influence of the slip mode on the microstructure evolution and compressive flow behavior at different strains in an extruded dilute Mg−0.5Bi−0.5Sn−0.5Mn alloy was analyzed through electron backscatter diffraction,X-ray diffraction,transmission electron microscopy,and hot compression tests.The results showed that at a low strain of 0.05,the basal,pyramidaland<c+a>slip modes were simultaneously activated.Nevertheless,at the middle stage of deformation(strain of 0.1,0.2 and 0.5),theslip mode was difficult to be activated and<c+a>slip mode became dominant.The deformation process between strains of 0.2 and 0.5 was primarily characterized by the softening effect resulting from the simultaneous occurrence of continuous dynamic recrystallization and discontinuous dynamic recrystallization.Ultimately,at strain of 0.8,a dynamic equilibrium was established,with the flow stress remaining constant due to the interplay between the dynamic softening brought about by discontinuous dynamic recrystallization and the work-hardening effect induced by the activation of the basalslip mode.
基金Project supported by the Spanish Government and European Union FEDER Grant(No.MTM200907719)
文摘The authors introduce a new Large Eddy Simulation model in a channel, based on the projection on finite element spaces as filtering operation in its variationM form, for a given triangulation （Th）h〉0. The eddy viscosity is expressed in terms of the friction velocity in the boundary layer due to the wall, and is of a standard sub grid-model form outside the boundary layer. The mixing length scale is locally equal to the grid size. The computational domain is the channel without the linear sub-layer of the boundary layer. The no-slip boundary condition （or BC for short） is replaced by a Navier （BC） at the computational wall. Considering the steady state case, the authors show that the variational finite element model they have introduced, has a solution （Vh,Ph）h〉O that converges to a solution of the steady state Navier-Stokes equation with Navier BC.
基金supported by the National Natural Science Foundation of China(Grant No.52172356)Hunan Provincial Innovation Foundation for Postgraduate(Grant No.CX20210384).
文摘Oscillation of fluid flow may cause the dynamic instability of nanotubes,which should be valued in the design of hanoelectromechanical systems.Nonlinear dynamic instability of the fluid-conveying nanotube transporting the pulsating harmonic flow is studied.The nanotube is composed of two surface layers made of functionally graded materials and a viscoelastic interlayer.The nonlocal strain gradient model coupled with surface effect is established based on Gurtin-Murdoch's surface elasticity theory and nonlocal strain gradient theory.Also,the size-dependence of the nanofluid is established.by the slip flow model.The stability boundary is obtained by the two-step perturbation-Galerkin truncation-Incremental harmonic balance(IHB)method·and compared with the linear solutions by using Bolotin's method.Further,the Runge-Kutta method is utilized to plot the amplitudefrequency bifurcation curves inside/outside the region.Results reveal the influence of nonlocal stress,strain gradient,surface elasticity and slip flow on the response.Results also suggest that the stability boundary obtained by the IHB method represents two bifurcation points when sweeping from high frequency to low frequency.Differently,when sweeping to high.frequency,there exists a hysteresis boundary where amplitude jump will occur.
文摘In this paper, steady incompressible micropolar fluid flow through a non-uniform channel with multiple stenoses is considered. Assuming the stenoses to be mild and using the slip boundary condition, the equations governing the flow of the proposed model are solved, and closed-form expressions for the flow characteristics （resistance to flow and wall shear stress） are derived. The effects of different parameters on these flow characteristics are analyzed. It is observed that both the resistance to the flow and the wall shear stress increase with the heights of the stenoses and the slip parameter; but decrease with the Darcy number, b^rthermore, the effects of the wall exponent parameter, the cross-viscosity coefficient and the micropolar parameter on the flow characteristics are discussed.
