Research On Multi-scale Numerical Simulation Method Of Void Evolution Inlarge Forgings

Large forgings manufacturing, the foundation of heavy machinery manufacturing, have played important role in national economy constructions, the development of defense equipment and the establishment of the modern advanced science major device. As we all know, internal defects such as shrinkage cavities and porosity inevitably occur in large ingots during steel casting. The continuity of the material is destroyed by these defects and stress concentration are easy to form during the service, resulting in crack damage. Many studies which is to eliminate internal voids defects in large forgings rely on finite element numerical simulation techniques to analyze the void evolution. However, the void size is far less than the feature sizes of large forgings, so existing numerical simulation there are model difficulties and complex simulation problems and so on. As a result, a multi-scale simulation method which is named as body cell method for void evolution in large ingot is put forward and the use of finite element software MSC.Marc secondary development function develop corresponding finite element software and its analysis model.Body cell method for numerical simulation of void evolution in large ingot includes macro model and cell model. Transfer of nodal and elementary information from the macro-model to the micro-model is the key to connect the two-level. The forging forming of large forgings and the evolution of the internal void defects are analyzed respectively on macroscopic scale and mesoscopic scale. Based on body cell method, the internal void defect of a specific forging is numerical simulated calculation, and the result of void evolution are compared with the published research results and experimental data which verify the accuracy of the analysis result of body cell method.In this dissertation, the key factors of cell model including ratio of side, the node density of void surface and the node density of cell surface are ensured. The single factor cyclical method is used to research on the influence of the factors and a better cell model factors are determined.As the lead to simulation material, artificial voids are prefabricated in lead. Through the upsetting experiment to study the evolution of void defect, and the result of experiment is compared with the simulation calculation result of body cell model method which verify the correct of body cell method. And it can accurately demonstrate the evolution of void defect.