528 トラスコアパネルの多段プレス成形性について

Abstract

Many new structure patterns of metal panel are used in modern life such as Truss Core Panel (FigA1) and Honeycomb panel. They are used as flooring or wall material in train, car, aircraft, buildings and so on at present. Beyond the traditional material, the new patterns have lighter weight and harder stiffness. However, difficulty exists for forming the Truss Core Panel. In this research, firstly theoretical forming limitation and simulation result is discussed and compared for tetrahedral truss core panel. Secondly, multi-stage forming method is presented, and the optimum pre-forming punch is decided by simulation model. TCP is a newly devised core panel formed by gluing or welding two same shaped panel pieces which have periodical indents. It has good cost performance due to easy press forming. The height of the core takes the main character for the advantages of TCP. As we know that it's more difficulty to form if the height increasing because of the occurrence of cracks caused by large stretch around the vertex of the triangular pyramid. So the forming limitation must be confirmed. To increase the available height value area of the core, we try a forming method by two procedures (FigA2): (a)A blank is formed to a hemispheric shape till a given height by stretching. (b)Then the blank is formed to triangular pyramid. By applying the explicit FEM, we simulated press forming of truss core panel with single stage or multi-stage and it was shown that we were able to apply to press forming for manufacturing truss core panel with about thickness remaining 70%. This research used ls-dyna to simulate the forming process. Using response surface method we got the optimal half-sphere pre-forming punch, which can improve almost 50% thickness reduction after whole pre-forming against single-stage forming process. By the same method, results shows that using the optimum hemispheric pre-punch can increase the height design range of TCP core about 50% against single-stage in the same situation and constraint.