| How to accurately predict and precisely control the thermal-fluid-structure coupling deformation of pre-molded micro-component is a common key scientific and technical problem in the processing production of micro-assembly molding in molds.Based on this key technical problem,a two-way thermal-fluid-structure coupling theoretical model describing the process of in-mold micro-assembly was established,and a numerical simulation platform was constructed for accurate prediction of thermal fluid structure coupling deformation and springback process.Through the combination of theory,simulation and experiment,the relevance theory of molding process parameters--melt rheological properties--two-way thermal fluid coupling effect and deformation was established,and the mechanism of thermal-fluid coupling deformation and rebound was revealed.It lays a scientific theoretical foundation and technical support for accurately predicting and precisely controlling the thermal-fluid-structure coupling deformation in mold,and achieves the following innovation and research conclusions:Based on the thermal-viscoelastic-plastic constitutive model and the two-way thermal-fluid-structure coupling theory,the thermal-fluid-structure two-way coupling theoretical model was established.Through the secondary development and the use of Fluent,MpCCI and Abaqus software,it is the first time to construct the numerical simulation platform for the two-way thermal-fluid-structure coupling process of in-mold micro-assembly molding,which provides theoretical and technical support for accurately predicting the coupling deformation and the rebound process.The relevance theory of molding process parameters--melt rheological properties--two-way thermal fluid coupling deformation was established,and it was found that the thermal-fluid-structure coupling deformation of micro-assembly molding decreases with the increase of the relaxation time of the secondary molding melt.The rheological mechanism that results in this relevance theory is that the driving force of coupling deformation is positively related to the shear viscosity of the melt,and the suppression force is positively correlated with the melt elasticity,while bath driving force and suppression force on micro-assembly surface the melt are positively correlated with relaxation time and the shear viscosity and the storage modulus of the material,so the driving force and restraining force of the assembly surface decrease with the increase of relaxation time,which results in a negative correlation between the coupling deformation and the melt relaxation time.The study shows that the coupling deformation difference predicted by thermal-fluid-structure single-way and two-way coupling method is as high as 26.7%.Therefore,establishing of the two-way thermal-fluid-structure coupling mechanism theory for in-mold micro-assembly molding is the theoretical premise of scientifically predicting coupling deformation.Experimental results show that the values of predicted by two-way thermal fluid solid coupling mechanism theory agree well with the experimental measurements.The research shows that the rebound tendency of coupling deformation increases with the increase of melt injection temperature.When the coupling load of the micro-assembly surface is reduced to zero,a certain amount of elastic deformation still remains inside the micro-axis.The reason for this phenomenon is that although the coupling load of the micro-assembly surface is reduced to zero,the interior of the micro shaft still has a high temperature,and the internal non-uniform temperature field generates thermal stress,which induces a certain elastic deformation.An innovative precision control technology of liquid membrane assisted micro in-mold assembly molding is proposed.The experimental results show that the technology can effectively reduce the coupling deformation by more than 50%,which can achieve precision control of molding process. |
