Abstract
Continuously rising demands of legislators require a significant reduction of CO2-emission and thus fuel consumption across all vehicle classes. In this context, lightweight construction materials and designs become a single most important factor. The main engineering challenge is to precisely adapt the material and component properties to the specific load situation. However, metallic car body structures using “Tailored blanks” or “Patchwork structures” meet these requirements only insufficiently, especially for complex load situations (like crash). An innovative approach has been developed to use laser beams to locally strengthen steel crash structures used in vehicle bodies. The method tailors the workpiece hardness and thus strength at selected locations to adjust the material properties for the expected load distribution. As a result, free designable 3D-strengthening-patterns surrounded by softer base metal zones can be realized by high power laser beams at high processing speed. The paper gives an overview of the realizable process window for different laser treatment modes using current high brilliant laser types. Furthermore, an efficient calculation model for determining the laser track properties (depth/width and flow curve) is shown. Based on that information, simultaneous FE modelling can be efficiently performed. Chassis components are both statically and cyclically loaded. Especially for these components, a modulation of the fatigue behavior by laser-treated structures has been investigated. Simulation and experimental results of optimized crash and deep drawing components with up to 55% improved level of performance are also illustrated.
Highlights
Car body structures for small and mid-range segments that are suited for large-scale production are predominantly made of steel or steel intensive constructions [1]
Current investigations aim at the development of an optimization program which combines all design approaches and which automatically calculates the optimum laser track geometry according to the individual requirements. 3.2
The paper shows an approach, how the lightweight potential of steel sheet structures can be significantly increased by a local laser treatment
Summary
Car body structures for small and mid-range segments that are suited for large-scale production are predominantly made of steel or steel intensive constructions [1]. It is necessary to develop novel large-scale technologies for precisely and flexibly adapting the component properties to the localized load situations. In order to design local laser-strengthened structures, especially for complex component geometries or load situations, numerical simulations are mandatory [9] [16]. In this context, the paper shows technical and mathematical possibilities for the determination and the subsequent implementation of required laser track material and dimensional data into FE models. The localized laser-strengthening process can make a valuable contribution to innovative steelbased automotive lightweight designs, improved passive vehicle safety and flexible car body manufacturing. Using already established laser technology for other processes (like welding or brazing), the technique can be integrated into existing large-scale manufacturing processes
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