黏弹特性对模内微装配成型热流固耦合变形的影响
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摘要
建立了综合考虑二次成型黏弹性熔体充填流动约束环境影响的模内微装配成型过程黏弹性热流固耦合变形机理的理论模型,并通过有限元数值模拟,研究了二次成型熔体黏度对模内微装配成型过程黏弹性热流固耦合变形的影响规律。结果表明,黏弹性热流固耦合作用诱导的预成型微型轴变形的驱动力来源于微装配界面形成的热流固耦合压力和黏性拖曳剪应力,而二次成型熔体流动的弹性正应力对耦合变形具有抑制作用,微装配界面的热流固耦合载荷和微型轴的变形均随着二次充填熔体的黏度增大而增大,减小二次成型熔体黏度有利于提高其微装配加工精度。
In order to solve the key scientific problems in control difficulty of thermal-fluid-structure coupling deformation in mold micro assembly process,a theoretical model was established to describe mechanisms of thermal-fluid-structure coupling deformation in polymer in-mold micro assembly molding process on the basis of the influence of environmental impact on secondary molding viscoelastic melt filling flow. A finite element numerical simulation was also conducted to investigate the effect of secondary molding melt viscosity on the thermal-fluid-structure coupling deformation during the mold micro assembly process. The results indicated that the driving force of the micro shaft deformation induced by the thermalfluid-structure coupling effect was derived from the thermal-fluid-structure coupling pressure and viscous friction drag shear stress on the micro assembly surface. However,the elastic normal stress of secondary molding viscoelastic melt filling flow showed a restraining effect on the coupling deformation. The thermalfluid-structure coupling load and micro shaft coupling deformation increased with increasing secondary molding melt viscosity,which reduced the viscosity of secondary molding melt. This is beneficial to the improvement in processing accuracy of the micro assembly.
In order to solve the key scientific problems in control difficulty of thermal-fluid-structure coupling deformation in mold micro assembly process,a theoretical model was established to describe mechanisms of thermal-fluid-structure coupling deformation in polymer in-mold micro assembly molding process on the basis of the influence of environmental impact on secondary molding viscoelastic melt filling flow. A finite element numerical simulation was also conducted to investigate the effect of secondary molding melt viscosity on the thermal-fluid-structure coupling deformation during the mold micro assembly process. The results indicated that the driving force of the micro shaft deformation induced by the thermalfluid-structure coupling effect was derived from the thermal-fluid-structure coupling pressure and viscous friction drag shear stress on the micro assembly surface. However,the elastic normal stress of secondary molding viscoelastic melt filling flow showed a restraining effect on the coupling deformation. The thermalfluid-structure coupling load and micro shaft coupling deformation increased with increasing secondary molding melt viscosity,which reduced the viscosity of secondary molding melt. This is beneficial to the improvement in processing accuracy of the micro assembly.
引文
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[13]DIRCKX M E.Demolding of Hot Embossed Polymer Microstructures[D].USA:Massachusetts Institute of Technology,2010.
[2]BEJGEROWSKI W.In-Mold Assembly of Multi-Functional Structures[D].USA:University of Maryland,2010.
[3]ISLAM A,HANSEN H,Marh9fer M,et al.Two-component Micro Injection Moulding for Hearing Aid Applications[J].International Journal of Advanced Manufacturing Technology,2012,62(5/6/7/8):605-615.
[4]MICHAELI W,KAMPS T.Micro Assembly Injection Moulding with Plasma Treated Inserts[J].Microsyst Technol,2008,14(12):1 903-1 907.
[5]ATTIA U M,HAUATA M,WALTON I,et al.Creating Movable Interfaces by Micro-powder Injection Moul-ding[J].Journal of Materials Processing Technology,2014,214(2):295-303.
[6]PIOTTER V,PROKOP J,RITZHAUPT H J,et al.Multicomponent Microinjection Moulding-trends and Developments[J].Int J Adv Manuf Technol,2010,47(1/2/3/4):63-71.
[7]STEVE M,DIETMAR D.Micro Assembly Injection Moulding with variothermal Mould Tempering[J].Microsystem Technologies,2017,23(4):1 017-1 025.
[8]周国发,胡舵,刘岑.剪切变稀效应对微型机械模内组装成型流固耦合变形的影响[J].高分子材料科学与工程,2012,28(12):183-186.ZHOU G F,HU D,LIU C.Influence of Shear-thinning on Polymer Micromachine Fluid-Solid Coupling Deformation in In-mold Assmbly Molding Process[J].Polymer Materials Science and Engineering,2012,28(12):183-186.
[9]周国发,王文光,刘岑.过程参数对微型机械模内组装成型流固耦合变形影响[J].塑性工程学报,2012,19(1):107-112.ZHOU G F,WANG W G,LIU C,Influence of Process Parameters on Polymer Micromachine Fluid-solid Coupling Deformation in In-mold Assembly Molding Process[J].Journal of Plasticity Engineering,2012,19(1):107-112.
[10]周国发,王梅媚,张宇.聚合物多相分层流动黏弹性包围机制的数值模拟研究[J].复合材料学报,2014,31(6):1 618-1 625.ZHOU G F,WANG M M,ZANG Y.The Numerical Simulation on the Mechanism of Viscoelastic Encapsulation in Polymer Multiphase Stratified Flows[J].Acta Materiae Compositae Sinica,2014,31(6):1 618-1 625.
[11]RAJAGOPALAN D,ARRMSTRONG R C,BROWN R A.Finite Element Methods for Calculation of Steady Viscoelastic Flow Using Constitutive Equations with a Newtonian Viscosity[J].Journal of Non-Newtonian Fluid Mechanics,1990(36):159-192.
[12]周文彦,周国发.聚合物多层气辅共挤精密成型机制的数值分析[J].复合材料学报,2009,26(3):90-98.ZHOU W Y,ZHOU G F.Numerical Investigation on the Mechanism of Polymer Multilayer Gas Assisted Co-extrusion Precision Molding Process[J].Acta Materiae Compositae Sinica,2009,26(3):90-98.
[13]DIRCKX M E.Demolding of Hot Embossed Polymer Microstructures[D].USA:Massachusetts Institute of Technology,2010.
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