Influence of microstructure on the mechanical properties and the forming behaviour of very thin metal foils
Influence of microstructure on the mechanical properties and the forming behaviour of very thin metal foils
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DOI：
10.1007/s00170-008-1851-4
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发表时间：
2010-03-01
影响因子：
3.4
通讯作者：
Geiger, M.
中科院分区：
文献类型：
--
作者：
Diehl, A.;Engel, U.;Geiger, M.
由于不断的小型化，对微成形工艺的精确工艺设计的需求正在稳步增加。然而，发生的尺寸效应阻碍了具有传统尺寸的标准板材成形工艺的现有技术在微成形工艺上的转让，如下料、弯曲和拉深。这些尺寸效应一般适用于所有微成形过程，因为表面颗粒份额的影响是特定于过程的，例如在弯曲过程中出现的大应变梯度的影响。发生尺寸效应的一个决定性参数是材料的平均颗粒尺寸与铝箔厚度的比率。对于基于模拟的微成形过程的描述，在有限元模拟中实现与尺寸相关的材料行为是必不可少的。因此，需要可靠地确定尺寸相关的力学性能作为有限元模拟的输入数据，以便为未来微成形过程的理论描述提供广泛的基础数据库。本文通过拉伸试验、胀形试验和基本弯曲试验，讨论了材料微观结构对厚度为25~500微米的金属箔力学性能的影响。指出了金属薄片厚度较小所带来的挑战，并提出了对金属薄片材料特性测试的未来要求。
The demand for accurate process design of microforming processes is increasing steadily due to ongoing miniaturisation. Occurring size effects, however, prevent the transfer of existing know-how of standard sheet forming processes with conventional dimensions like blanking, bending and deep drawing on microforming processes. These size effects are either generally valid for all microforming processes, as the influence of the share of surface grains are process-specific, like the influence of large strain gradients as they appear, e.g. in bending processes. A decisive parameter for the occurrence of size effects is the ratio of material mean grain size to foil thickness. For a simulation-based description of microforming processes, the implementation of size-dependent material behaviour in finite element (FE) simulation is essential. Hence, a reliable determination of size-dependent mechanical properties as input data for FE simulation is needed to provide a broad fundamental database for a future theoretical description of microforming processes. In the present paper, the influence of the material microstructure on the mechanical properties of metal foils with thicknesses ranging from 25 to 500 mu m is discussed based on tensile tests, bulge tests and fundamental bending experiments. Challenges resulting from the small thickness of the metal foils are pointed out, and future demands regarding determination of material characteristics of thin metal foils are presented.