Production and characterization of complex folded cellular structures made of sheet metal

通过折叠平坦的半成品，可以生产三维蜂窝结构。折叠结构可用于各种技术领域，特别是作为两个覆盖片之间的夹层芯材料。夹层结构方法提供了将刚性、大面积构件付诸实施的可能性。与传统的整体式或差动式结构相比，这些组件可以节省大量的重量和材料。如今的蜂窝折叠结构只能由厚度非常小（s 0 ≤ 0.2 mm）的初始材料制成。除了用作夹层结构外，金属板厚的折叠结构在工业上还具有很大的潜力，可用作覆层结构、碰撞和承载结构。金属板制成的蜂窝状折叠芯是基于等距折叠结构的。在初始状态下，通过围绕一个或多个弯曲轴取向（BAO）的局部弯曲工艺将大致平坦的半成品形成为重复的单位单元。根据DIN 8582的弯曲具有特殊的地位，因为局部弯曲轴的形成可以实现工件（这里是芯部）的复杂成形，这可以实现非常特殊的应用和特定于应用的部件设计。该研究项目的目的是生产和表征由厚度大于0.5 mm的铝或钢板制成的复杂蜂窝结构。为此，正在开发一个工作流程，涵盖从几何和结构设计到新开发的生产技术及其技术限制的所有方面，以制造和检查/质量保证由上述厚度范围内的金属板制成的优化结构。特别涉及以下次级目标：- 开发和转让用于折叠较厚板材的分析设计方法-开发用于预结构化板材的方法-开发用于生产折叠夹层芯材的工艺-夹层板机械性能的建模和工艺边界的定义该项目的科学发现一方面可以更精确地估计由金属板制成的折叠结构作为用于二维夹层应用的新型芯材料的潜力，并且另一方面扩展了关于金属板在复杂的、先前未完成的等距成形工艺中的行为和加工的基本知识。

By folding flat semi-finished products, three-dimensional cellular structures can be produced. Folding structures can be used in various technical fields, especially as sandwich core material between two covering sheets. Sandwich construction methods offer the possibility to put rigid, large-area components into effect. These components have considerable weight and material savings compared to conventional monolithic or differential construction methods.Today’s cellular folding structures can only be produced from initial materials with very small sheet thicknesses (s0 ≤ 0.2 mm). In addition to their use as sandwich elements, folded structures with thicker sheet metals offer considerable potential for the industrial use as cladding elements, crash and carrying structures.The cellular folding cores made of sheet metal are based on isometric folded structures. In the initial state, a mostly flat semi-finished product is formed into repeating unit cells by local bending processes around one or more bending axis orientations (BAO). Bending according to DIN 8582 takes an exceptional position, since the formation of local bending axes enables complex shaping of the workpiece (here the core), which enables an extraordinarily application and application-specific component design. The aim of the research project is the production and characterization of complex cellular structures made of aluminium or steel sheet with thicknesses greater than 0.5mm. For this purpose, a workflow is being developed that covers all aspects from the geometric and structural design to the newly developed production technologies and their technological limits to the manufacture and inspection / quality assurance of optimized structures made of sheet metal in the above-mentioned thickness range. The following sub-targets are addressed in particular: - Development and transfer of analytical design methods for folding thicker sheets - Development of methods for pre-structuring sheet metal - Process development for the production of folded sandwich cores - Modelling of the mechanical properties of sandwich panels and definition of process boundariesThe scientific findings of this project on the one hand enable a more precise estimation of the potential of folded structures made of sheet metal as a new type of core material for two-dimensional sandwich applications and on the other hand extend the basic knowledge on the behaviour and processing of sheet metal in complex, previously unfinished isometric forming processes.