No abstract

Continually increasing exhaust emission standards for automobiles and an increasing environmental awareness push design engineers to develop new constructive and material concepts. So-called sandwich panels, consisting of stiff facings and light-weight cores, offer the possibility to combine properties of different materials synergistically. When processing large quantities, as is the case in the automotive industry commonly used manufacturing processes for cutting sandwich panels, like sawing or milling, are not applicable. A common manufacturing process to cut metal sheets in high quantities is shear cutting. However, pre-trials of shear cutting of sandwich panels have shown that it is not possible to achieve flawless cutting surfaces with current process layouts. Characteristic types of failure like high bending of the facings, delamination effects, burr formation and an undefined cracking of the core material were ascertained. Thus, in this study, the influence of cutting parameters, such as the clearance and the punch diameter, on these types of failure is examined. Five different clearances between 0.025 mm and 0.4 mm with two punch diameters, 8 mm and 32 mm, were investigated. In order to compare the influence of different materials, three commercially available sandwich panels were studied. The chosen sandwich panels differ both in the face sheet thickness and the core material. Finally, the shear cutting force is measured to identify a possible correlation between the cutting force and the face bending. As a result, optimal clearances to minimize the face bending are derived. Additionally, the influence of the core stiffness on the cutting force is determined.

New approaches in lightweight design require the use of multi materials like metalpolymermetal composites. Composite materials, especially so-called sandwich panels, offer the possibility to combine properties of different materials synergistically. Shear cutting is one of the commonly used manufacturing processes. However, conventional shear cutting of sandwich panels leads to characteristic types of failure, such as high bending of the facings, delamination effects, burr formation and an undefined cracking of the core material. In the present research, the cutting force requirement and the failure progress for lubricant free shear cutting of metal-polymer-metal composites is studied. Two thermoplastic polymers, an aluminum sheet and an unalloyed steel sheet are combined in order to create different composite materials. Furthermore, the composite materials are cut stepwise to examine the different stages of a cutting process in detail.

Abstract. Metal polymer sandwich sheets consist of materials with drastically different mechanical properties. Due to this fact and because of high local gradients in the cutting zone during the blanking process, traditional process strategies and empirical knowledge are difficult to apply. A finite-element simulation of the shear cutting process is used to predict the necessary force and the geometry of the cutting surface. A fully-coupled ductile damage model is used for the description of the material behaviour. This model considers the influence of shear and compression-dominated stress states on the initiation of damage. Experimental tensile and compression test data is used for the identification of material parameters. The results of the blanking simulation are compared with experimental data. Furthermore, the evolution of the stress state is analysed to gain understanding of the underlying physics. Finally this model enables the prediction of core compression and other quantities such as the acting stresses and corresponding triaxilities, which provide valuable information for the development of analytical models.

Verbundbleche, bestehend aus Metall- und Polymerschichten, haben ein hohes Anwendungspotential. Je nach Schichtaufbau liegen die Vorteile im Bereich des Korrosionsschutzes, des Leichtbaus sowie der Geräuschdämmung. Um das Potential dieser Materialien zu nutzen, müssen die Parameter konventioneller Fertigungsverfahren angepasst werden. Der Fachbeitrag beschreibt den Einfluss wichtiger Parameter auf die Schnittgüte beim Scherschneiden.   Composite sheets, consisting of sheet metals and polymer layers, have high application potential. Depending on the used layers they can be used as corrosion protection, lightweight or sound insulation materials. To exploit the advantages of these materials the parameters of conventional manufacturing processes have to be adapted. In this publication the influence of important parameters on the shear cutting quality is explained.