Elastic-plastic deformation of lightweight core-perforated sheet metal laminates and their optimum design considering strength, rigidity and formability

在这个项目中，夹层金属板与穿孔的核心和皮肤是新开发的轻质壳结构的使用。采用铜夹芯试件，通过单向拉伸、弯曲和拉伸成形等力学试验，研究了该类型板的弹塑性力学性能。通过有限元分析，探讨了该板的弹塑性变形机制和成形极限。（1）通过单轴拉伸试验，研究了夹层板（孔隙体积分数V_f = 17%）、整体铜片和单层穿孔板（V_f = 28%）的塑性流动强度。单孔板的比强度（强度除以板的密度）比整体板低28%，而夹层板仅低5%，夹层板具有优良的抗弯刚度性能，其抗弯刚度是整体板的2.7倍。(2)夹层板的成形极限图（FLD）类似于单层穿孔板的成形极限图。平面应变条件下的极限应变并不比单块板的极限应变小，而平衡双向拉伸条件下的极限应变明显小于单轴拉伸条件下的极限应变。从实验观察，以及有限元模拟，它的结论是，夹层板的断裂将发生作为一个结果，应变局部化在皮肤金属。

In this project, sandwiched metal plates with perforated core and skins are newly developed for the use of lightweight shell constructions. Using copper sandwiched specimens, mechanical properties of elasto-plasticity of this type of plates were examined by performing several mechanical tests such as uniaxial tension, bending and stretch forming. Moreover, the mechanisms of elastic-plastic deformation and the forming limit of this plate were investigated by the finite element analysis. The present findings are summarized as follows:(1) The plastic-flow strength of the sandwiched plate (its volume fraction of voids V_f = 17%), as well as a monolithic copper sheet and a single perforated sheet (V_f = 28 were examined by uniaxial tension tests. For the single perforated sheet the specific strength (= strength divided by the density of the plates) is 28% less than that of the monolithic sheet, while for the sandwich plate it is only 5% less. The sandwich plate has excellent performance in bending rigidity, namely it is as high as 2.7 times of one of the monolithic plate.(2) The forming limit diagram (FLD) of the sandwiched plate is similar to one of the single perforated sheet. The limit strain under plane-strain condition is not so small compared to one of the monolithic sheet, while it under balanced biaxial stretching condition is significantly smaller than that under uniaxial tension. From the experimental observations, as well as the FE simulation, it is concluded that the fracture of the sandwich plate will occur as a result of strain localization at the skin metals.