Influence of machining thin lightweight construction node components from different aluminum alloys on residual stress and microhardness in the outer surface zone

Brüggemann, T.1, a; Biermann, D.1, b; Zabel, A.1, c

1)
Institut für Spanende Fertigung, Technische Universität Dortmund, Baroper Str. 303, 44227 Dortmund

a) brueggemann@isf.de; b) biermann@isf.de; c) zabel@isf.de

Kurzfassung

In the industrial age, the milling operation due to its flexibility plays a central role relating to the workpiece geometry and workpiece material, while ensuring a high surface quality. The milling process is just for the production of complex components and during manufacture of small batches the most important production process. Because of the high milling costs in relation to the total process costs, which are the long process chain owed involves this form of processing enormous improvement potentials. The maximum cutting performance is dependent on both the available spindle speed as well as the process dynamics. While most studies primarily confine process parameters, such as axial feed, feed and cutting speed as the process dynamics influencing factors to consider, among other things, also plays the workpiece geometry an important role. Specially, when machining thin walled workpieces, due to the association of the geometric properties with the dynamic behavior of the workpiece no stable milling can be carried out at high material removal rates. Unfavorable machining strategies in this case result in a negative influence of the surfaces in the form of chatter marks or even deformation of the thin-walled sections. Therefore it is usually necessary to carry out an adjustment of the process parameters, whereby the productivity of the process is no longer guaranteed. For the economical production of such components with respect to the process parameters, appropriate machining strategies can be developed taking into account the geometry and material of the workpiece.

As a part of this research project lightweight nodal connection elements for connecting extruded profiles are optimized. Because of the current geometry there exists a potential for weight reduction by reducing the wall thickness of these components. In addition, the effect of milling on the quality of the bonding zones of these components considering high-strength aluminum alloys has not been adequately researched. As described in the literature, there is a damage of the outer surface layer by machining. Depending on the deformation by overlapping stress states and the hardness of the node at the joining process, the quality of connection of the lightweight structures and the surface characteristics of node elements during the manufacturing are crucially affected. Accordingly, it is important to optimize the machining process of the connection elements.

The aim of this work is to identify the minimum wall thickness for the lightweight connecting elements produced by machining which fulfills the requirements for both feasible and efficient process parameters. Additionally, in context of the joining zone optimization, knowledge is gained with respect to the optimal processing strategy for the workpieces. Based on the results of the investigations, a direct correlation between the changes in the surface zone and the input variables are made, so that the influence of the machining strategy on the surfaces can be documented. Thus, other projects that are concerned with the bonding strength after joining can revert to this database.

Schlüsselwörter

Aluminium, Milling, Residual Stress, Lightweight Structures, Micro Hardness

Veröffentlichung

In: Proceedings of the 13th euspen International Conference, 27.3.-31.3. 2013, Berlin, Germany, S. 68-71