Theory And Experiment Research On The Multiple Source Heat Conduction Inversion Of The Curing Reaction Mould Heating System

The uniform mould temperature field is very important for the production of high-quality plastic products. Too high temperature of the mould often causes some problems of the plastic products, such as increase of shrinkage rate, decline in the dimensional accuracy, lose in the shine or brightness on the surface, distorted part and difficult demould. While too low temperature of the mould gives a decrease in the viscosity of the plastic melt and an increase in the flow resistance, causing the insufficient filling phenomenon, inadequate prepolymer crosslinking and rough surface, and then the mechanical strength of the plastic products will be affected. However, the heat pipes that are placed independently in the heat plates are the main heat sources of the mould heating system. As the power of the heat pipes, the distance of the pipes between each other and the thermal environment for each pipe are not identical, and there are a wide variety of plastic products and mould structures, so it is rather difficult to design the mould heating system. If the temperature in the mould heating system does not distribute uniformly, the requirements for producing accurate plastic products cannot be met. Unfortunately, so far, there is no mature theory that can be used to guide the designs of the heat intensity or the space distributions of the mould heating system.The solution of heat source intensity of the mould heating system is a typical inverse conduction problem, which is to solve the loading condition of the heat pipes under the given temperature field (in this thesis, the temperature field experiment method is used). On the basis of the multiple source heat conduction inversion theory in the literatures, a simple effective inverse multiple heat source algorithm for the heating system of the curing reaction mould is explored. The theories and method in this thesis can be used as references for the designing of an uniform temperature field.Major innovations of the current thesis are as follows.(1) By studying the heat conduction mechanism of the mould heating system, the heating system is divided into two parts:the internal curing reaction temperature field and the external controllable temperature field. The coupling mathematical model is established on the contact interface by analyzing the boundary conditions. The numerical simulation technique is used to simulate the curing reaction temperature field of the BMC plastic. The obtained internal curing reaction temperature field is used as the load for the numerical simulation of the extern controllable temperature field, so as to complete the coupling temperature field numerical simulation of the mould heating system.(2) According to the heat conduction characteristics of the curing reaction mould heating system, combining with the linear heat conduction superposition principle, the multiple source inversion algorithm for the heat conduction of the mould heating system is proposed. For the ill-posedness of the inversion problem, the square norm is selected to improve the stability and the accuracy of the inverse process.(3) An experimental system is built with a single cavity curing reaction mould and a temperature controlling system. The measured temperature data of the mould cavity are inputten into the heat conduction multiple source inversion algorithm. The heat error sensitivity analysis method is adopted to quantitatively analyze the experimental measurement errors. It provides the basis for improving the heat pipes and the mould manufacturing precision, so as to reduce the experiment errors. The inversion result and the experimental result agrees very well, which indicates that the unreasonable heat source intensity and the heating process are the main causes of the non-uniform temperature field in the mould heating system.(4) According to the uniformity requirement of the target temperature field, the mould heating process is improved. The temperature rising curve of the mould cavity surface is constructed for the secondary inversion. The secondary inversion results show that the uniformity of the mould cavity temperature field has met the requirement and the heating efficiency has been also improved greatly. To verify the generality of the proposed inversion algorithm, a multiple cavity mould is also designed and tested and good inversion results have also been achieved.