Finite element analysis of the combined fine blanking and extrusion process.

摘要

The combined fine blanking and extrusion process is such a metal forming process that fine blanking and forward extrusion are carried out on sheet metal material at the same time. There are two typical characteristics in this process, one is the fine blanking whose deformation mechanism is different from conventional blanking; the other is the sheet metal extrusion, which is different from the conventional extrusion.; Even though fine blanking has been used in industry for many years, only limited literature can be found which deals with the theoretical analysis of it. On the other hand, no publications on the theoretical analysis of the sheet metal extrusion have been found. Intensive work should be carried out to reveal the mechanism of both fine blanking process and sheet metal extrusion process, and further the combined fine blanking and extrusion process.; The scope of this thesis is to study the mechanics of fine blanking, sheet metal extrusion, and combined fine blanking and extrusion process one by one with the rigid-plastic finite element method.; All of above processes are typical unsteady ones, especially the fine blanking process in which extremely severe and localized deformation occurs. Therefore, commercial programs can not be used to solve these problems up till now. Owing to this reason, a rigid-plastic finite element program was developed for simulating these processes where remeshing and mesh tracing techniques as well as the golden section method were adopted according to the characteristics of these processes in this thesis. Moreover, a permissible kinematic velocity field was adopted as the initial velocity field for simulating extrusion process successfully.; Results from the simulation included the distorted mesh, the field of material flow, the stress and the strain distributions at various moments of deformation. Results under different deformation conditions such as different blanking clearances, different diameters of the extrusion punch and different slopes of the sloping wall extrusion were obtained, comparisons between the results from different deformation conditions were made. Valuable phenomena were obtained from the simulation and the deformation features were revealed in detail. Based on the simulated results, different deformation models were proposed.; In order to verify the effectiveness of the simulated results, some experiments had been carried out. The method of performing the fine blanking experiment as well as the combined fine blanking and extrusion experiment on the conventional press was developed. Accordingly, the special equipment and the corresponding die set were designed and manufactured for the experiment. With the mesh etching method, the distorted meshes on the meridian plane of the specimens after deformation were obtained from the experiment. In order to calculate the effective strain distribution on the meridian plane of the specimen, large strain analysis technique was adopted and improved. Hardness distributions on the specimens were measured. The fracture on the side of the extruded part was analyzed.; Both the simulated results and the experimental results were discussed. Comparison between the simulated results and the experimental ones showed that the simulated results agreed well with the experimental ones.