| In order to promote large-scale structural aluminum alloy components applied in automotive industry and reduce the vehicle's own weight and fuel consumption and exhaust emissions, it is necessary to explore and develop an advanced forming technology with high efficiency and short process. Under the support of two project, National Science & Technology Pillar Program"Study on Forming Technology and Equipment of Pressure Cast for High Performance Aluminum Alloy and Stamping for High Strength Steel"and Key Project of Science & Technology of Hunan Province"Research and Demonstration of Light-weight Vehicle Key Technology", some works on LPDC process design and forming technology for thin-walled aluminum alloy casting with permanent mould are done.In this thesis, the interfacial heat transfer coefficient during casting solidification is calculated to improve the simulation accuracy of the casting process. Then the LPDC process parameters of A356 aluminum thin-walled component with 1.5mm in thickness are designed and optimized using a combining numerical simulation and optimization technology method. The research results in this thesis are summarized as following:1) The casting-metal mold IHTC has been identified by using two different inverse analysis methods, inverse heat conduction method and neural network model, based on measured temperatures at the various locations of casting. The results show that the IHTC is not a constant and varies with time during the casting solidification. And the IHTC decreases rapidly down when the temperature of casting is between liquidus and solidus curve. However, under solidus curve it is almost invariant and remains a constant. This provides valuable references for setting accurately the boundary condition in numerical simulation process.2) In order to calculate the IHTC more accurately, the model of forward and inverse heat conduction problems for one-dimension is established. The code for the models is also compiled. The compared results between the analytical and numerical simulation solution confirm that the model and compiled code of heat conduction for one-dimension is stable and accurate. Moreover, the effects of some parameters in the inverse heat conduction model on the stability and accuracy of calculation results are also discussed in this thesis. The parameters include the damping factorμ, future time step R and time step△t in the forward heat conduction calculation.3) The interfacial heat flux and heat transfer coefficient of A356 casting on a water cooled copper chill are successfully obtained by using the inverse heat conduction method based on the measured temperatures closer to the interface in the casting after the'equivalent specific heat'method is applied to the forward heat conduction calculation. And it was found that the IHTC varies with time during the casting solidification. The values are in the range of approximately 1200-6200Wm-2K-1 and two peak values exist when the casting temperature is above the solidus temperature because of the released latent heat.4) Considering the poor filling-ability of thin-walled casting in LPDC process, an ANN model combining learning vector quantization (LVQ) and back-propagation (BP) algorithm is proposed in this thesis to map the complex relationship between process conditions and quality indexes of LPDC parts based on the accurate boundary condition, IHTC, in numerical simulation. And the orthogonal array and finite-element method are successfully applied to obtain the training samples for the sake of experimental accuracy and cost saving. Then, a genetic algorithm is implemented to optimize the process.5) By applying the optimized parameters, a thin-walled component with 1.5mm in thickness is successfully prepared. And compared with the casting prepared before process parameters optimized, the quality of casting is obviously improved. Some new results provide the useful guidance for the further study on LPDC technology of aluminum alloy thin-walled component with permanent mould and mass-producing thin-walled aluminum alloy casting applied in automotive industry.
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