Study On Numerical Simulation Of Aluminum Profile Extrusion Process And Structure Optimization Of Extrusion Die

Aluminum profile extrusion is an efficient precision plastic forming technology. With the development of Chinese economy, the manufacturing, application and consumption of aluminum extrusion profiles have greatly increased. The core technologies of the aluminum alloy extrusion process are the design, manufacture and operation of extrusion dies. In Chinese aluminum extrusion industries, most of die designs still use experience analogies. The success rate of the first die testing is only 50%, which seriously hampers the development of Chinese aluminum extrusion industries. Compared with other metallic plastic forming methods, aluminum alloy extrusion has the characteristics of diverse varieties and short production cycle. Therefore, how to speed up the analysis and modeling process, reduce analysis time and increase computational efficiency mean great significance for introducing the numerical simulation based design method.This paper mainly studies the numerical methods of aluminum extrusion process. Making use of Arbitrary Lagrangian-Eulerian method(ALE), use the weight function to describe the metal flowing process in the die cavity by Eulerian description and to describe the free deformation of extrudates by Lagrangian description. In this way, ALE method can depict complex aluminum profile extrusion steady state process effectively. Finally, comparing the simulation with experiment, the results are with good consistent, feasibility and accuracy of the analysis are proved.The mechanism of buckling in the extrusion forming process is further studied based on F. Halvorsen and T. Aukrust's research, combined with the standard deviation of velocity field evaluation method for outlet velocity field, this paper proposes the relative standard deviation of velocity field (RSDV) evaluation function to replace the standard deviation of velocity field (SDV) as the criterion for stable extrusion forming. According to transient analysis, time- relevant criterion is used and a numerical example to estimate the extrusion stability is shown. Finally, orthogonal design method is carried out to optimize the process parameters of a double T shape profile and to investigate an extrusion industries process and die parameters standardization. Experiment result demonstrates the rationality of the optimized process and it is fit well with the simulation result. It can come to a conclusion that the outlet velocity field criterion could be used as an optimization target to establish extrusion industries standard.This paper puts forward an arc-shape die inlet structure design method for heavy hollow section profiles. Comparing with two traditional design methods without changing any other main factors, such as the distribution of portholes, the shape and the depth of welding room etc, we find that the diversity of hydrostatic stress and the properties of metal forming uniformity in the extruding process between the new method and two regular methods are not obvious, but the work condition is greatly improved From the simulation results, the maximum stress of the arc inlet structure is only 75.0% and 72.3% that of two regular design methods and the total stress is decreased by 10% to 20% respectively, furthermore, the uniformity of stress load distribution is better.A quantitative analysis design method to predict the elastic deformation situation of the die in the working condition by numerical way is put forward. Detail analysis is present for the influence of elastic deformation on profile wall thickness of an asymmetry multi-mandrel die. Finally, compared with experimental results, the accuracy of the simulation method on wall thickness design has been verified. The result can provide a reference for die design and manufacturing. Using this method, the success rate can improve highly and the cost can be cut down.A numerical modeling method based on rigid-viscoplastic finite element method for steady analysis is put forward. The simulation results are fit well with experiments. According to the flowing deformation mechanism and traits, using proper simplification and assumption, both the gird distortion and remeshing of finite element method in the large deformation forming process and the accumulated error due to grid movement can be avoided, so the accuracy can be ensured. Detail analysis of results is carried out. Furthermore, the criterions to judge the reliability of results and the causes of the error are summarized. With a long time of practical application, the availability of this method has been proved in simulating complicated profiles extrusion process. It provides an effective prediction to satisfy the demand of aluminum extrusion delivery, which can optimize die design and improve the die testing success rate.