In this work, the computational fluid dynamics method is used to study the liquid hydrodynamics behavior in the microchannel without central insert(MC1) and the central insert microchannel(MC2), respectively. The maxi...In this work, the computational fluid dynamics method is used to study the liquid hydrodynamics behavior in the microchannel without central insert(MC1) and the central insert microchannel(MC2), respectively. The maximum deviation between simulation and experiment is 24%. The formations of flow patterns are explained based on contours and force analysis where the flow pattern maps are established by two-phase flow rate. The effects of aqueous phase viscosity and two-phase flow rate on the characteristic sizes of each flow pattern are also explored. Specifically, four unconventional flow patterns are found in MC2, namely the unique droplet flow, the unique slug flow, the unique coarse annular flow and the unique film annular flow. Though the insert occupies part of the channel, the pressure difference in the channel is significantly reduced compared with MC1. Moreover, the insert significantly changes the formation velocity range of each flow pattern, greatly broadens the formation range of annular flow and also has an important influence on the characteristic size of the flow pattern. The organic-phase dimensionless axial size(Lo/W) and the dimensionless radial size(Do/W) of the droplet(slug) are negatively related to the aqueous-phase viscosity(μa) and flow rate(ua). The Do/W of the annular is negatively correlated with μaand positively correlated with organic-phase flow rate(uo). This study provides direct numerical evidence that the insert is key to the formation of bicontinuous phase flow pattern, as well as further strengthens our understanding of the flow characteristics and optimization design of insert microchannels.展开更多
The effective surface treatment method for steel insert composited with Al base metal by expendable pattern casting （EPC） process and the bonding interface between steel insert and Al base metal were investigated.It...The effective surface treatment method for steel insert composited with Al base metal by expendable pattern casting （EPC） process and the bonding interface between steel insert and Al base metal were investigated.It was found that Zn plating on steel insert was effective on improving the bonding property between steel insert and Al base metal in EPC process.Zn is thought to promote the formation of diffusion layer.But almost none content of Zn was observed in the boundary which had been plated on the steel insert.A diffusion layer consisting of Al,Si and Fe was formed at the insert/alloy interface and its hardness was higher than the steel insert as matter of course Al base metal.This layer turned out to be intermetallic compounds of Al-Si-Fe system.Higher pouring temperature promoted the diffusion of Fe into Al alloy,so Fe content in intermetallic layers increased at higher pouring temperature.The layer nearest to steel disappeared due to applied pressure.展开更多
The microstructure and mechanical properties of cast inserted dies for automobile covering components were studied. The results show that the as-cast microstructures of cast inserted dies are composed of pearlite, mar...The microstructure and mechanical properties of cast inserted dies for automobile covering components were studied. The results show that the as-cast microstructures of cast inserted dies are composed of pearlite, martensite, bainite, and austenite; and that the annealed microstructure is granular pearlite. The mechanical properties of cast inserted dies approach that of forged inserted dies. The tensile strength is 855 MPa, the elongation is 16%, the impact toughness is 177 J/cm2, and the hardness after annealing and quenching are HRC 19 and HRC 60-62. In addition, the cast inserted dies have good hardenability. The depth of the hardening zone and the hardness after flame quenching satisfy the operating requirements. The cast inserted dies could completely replace the forged inserted dies for making the dies of automobile covering components.展开更多
基金supported by the National Natural Science Foundation of China(21776180,22108177)the Key Research Development Project of Sichuan Province(21ZDYF4086).
文摘In this work, the computational fluid dynamics method is used to study the liquid hydrodynamics behavior in the microchannel without central insert(MC1) and the central insert microchannel(MC2), respectively. The maximum deviation between simulation and experiment is 24%. The formations of flow patterns are explained based on contours and force analysis where the flow pattern maps are established by two-phase flow rate. The effects of aqueous phase viscosity and two-phase flow rate on the characteristic sizes of each flow pattern are also explored. Specifically, four unconventional flow patterns are found in MC2, namely the unique droplet flow, the unique slug flow, the unique coarse annular flow and the unique film annular flow. Though the insert occupies part of the channel, the pressure difference in the channel is significantly reduced compared with MC1. Moreover, the insert significantly changes the formation velocity range of each flow pattern, greatly broadens the formation range of annular flow and also has an important influence on the characteristic size of the flow pattern. The organic-phase dimensionless axial size(Lo/W) and the dimensionless radial size(Do/W) of the droplet(slug) are negatively related to the aqueous-phase viscosity(μa) and flow rate(ua). The Do/W of the annular is negatively correlated with μaand positively correlated with organic-phase flow rate(uo). This study provides direct numerical evidence that the insert is key to the formation of bicontinuous phase flow pattern, as well as further strengthens our understanding of the flow characteristics and optimization design of insert microchannels.
文摘The effective surface treatment method for steel insert composited with Al base metal by expendable pattern casting （EPC） process and the bonding interface between steel insert and Al base metal were investigated.It was found that Zn plating on steel insert was effective on improving the bonding property between steel insert and Al base metal in EPC process.Zn is thought to promote the formation of diffusion layer.But almost none content of Zn was observed in the boundary which had been plated on the steel insert.A diffusion layer consisting of Al,Si and Fe was formed at the insert/alloy interface and its hardness was higher than the steel insert as matter of course Al base metal.This layer turned out to be intermetallic compounds of Al-Si-Fe system.Higher pouring temperature promoted the diffusion of Fe into Al alloy,so Fe content in intermetallic layers increased at higher pouring temperature.The layer nearest to steel disappeared due to applied pressure.
文摘The microstructure and mechanical properties of cast inserted dies for automobile covering components were studied. The results show that the as-cast microstructures of cast inserted dies are composed of pearlite, martensite, bainite, and austenite; and that the annealed microstructure is granular pearlite. The mechanical properties of cast inserted dies approach that of forged inserted dies. The tensile strength is 855 MPa, the elongation is 16%, the impact toughness is 177 J/cm2, and the hardness after annealing and quenching are HRC 19 and HRC 60-62. In addition, the cast inserted dies have good hardenability. The depth of the hardening zone and the hardness after flame quenching satisfy the operating requirements. The cast inserted dies could completely replace the forged inserted dies for making the dies of automobile covering components.
