Boundary Element Method For The Deformation Simulation Of Plastic Injection Mold

In the injection molding process, the mold deformation under the pressure of thepolymer melt, directly affects the dimensional precision of plastic products. And it alsodetermines the cost and lifetime of the injection mold. The surface load acting on moldcavity is the reaction force of polymer melt, which unevenly and continuously changes. Soit is difficult to apply boundary loads when doing numerical analysis of mold deformation.For what, the existing structural analysis software cannot calculate the mould deformation.But the CAE software for plastic injection molding does not contain structural analysismodule either.In order to solve these problems, this thesis focus on the deformation simulation ofplastic injection mold using boundary element method. The research work was carried outfrom following four aspects.(1) The coordinate transformation and element degradation method were applied toremove the singularity of linear，quadratic triangular and quadrilateral elements.(2) The factors affecting solving accuracy and speed were comprehensively discussed.The numerical results show that discretization error gets lower as the number of elementsincreases. If gauss elimination method was adopted to solve the system of linear algebraicequations, the computational data should be stored in double-precision. And it is better touse quadratic elements for bending deformation.(3) For three-dimensional frictionless contact problem, different formats of boundaryelement method were derivate based on conforming (point-point) discretization andnonconforming (point-surface) discretization.(4) based on the research work above, an injection mold deformation module waspreliminarily realized in injection molding CAE software. Results were compared withthose from ANSYS simulation and experimental data. Due to the same surfacetriangle mesh discretization between the injection mold and plastic products, the pressure field of polymer melts can be directly read form CAE filling analysis results to act onmold cavity. Compared to simulate in ANSYS, it avoids the accuracy loss by there-modeling and data transformation between different software. So the results are moreclose to the experimental data. Besides, the deformation of the mold cavity can be used asan effective supplement to the warpage result from the injection molding CAE software. Itprovides a more comprehensive reference for optimizing the design of injection mold andparameters for injection processing.