Gundolf Kopp

Innovative Fahrzeugstruktur in Spant- und Space-Frame-Bauweise

Im Rahmen des Forschungsthemas „Neuartige Fahrzeugstrukturen“ des DLR wird in Stutt gart an der Entwicklung zukunftiger Fahrzeugkonzepte und -strukturen geforscht. Das in diesem Beitrag beschriebene Projekt beschaftigt sich mit der Entwicklung einer innovativen Spant- und Space-Frame-Bauweise. Dabei werden wegweisende Verbesserungen hinsichtlich einer Gewichts reduzierung, einer gesteigerten Sicherheit und innovativen Modularisierungs-strategien erzielt.

Sandwich Lightweight Design in Automotive Usage

State of the Art

Werkstoffe und Bauweisen ermöglichen neue Fahrzeugkonzepte

Werkstoffe undWerkstofftechniken sind eine Schlusseltechnologie fur die Entwicklungsgeschichte der Menschheit. Dabei haben schon „fruhe Ingenieure“ mit den damals verfugbaren/gewinnbaren Materialien kluge Konstruktionen bzw. Bauweisen realisiert. Beispiele dafur sind im WachsausschmelzverfahrenhergestellteBronzenoder ausPergamentblatterngefugte Mumiensarge (siehe Abb. 1).

Dynamic bending behaviour of magnesium alloy rectangular thin-wall beams filled with polyurethane foam

ABSTRACT This study proposes a hybrid structural design concept of polyurethane foam-filled magnesium alloy AZ31B rectangular thin-walled beams which serve as energy absorbing components in automotive applications. Uniaxial tensile and compressive tests, and fracture tests were performed to investigate the material mechanical properties. Dynamic three-point bending tests were performed to study the deformation/fracture modes and energy absorption capacity for the foam-filled AZ31B beams, and to compare these mechanical properties with those for mild steel DC04 beams. Different AZ31B beams were filled with a variation of foam density (0.05, 0.20 and 0.30 g/cm3). It was found that the AZ31B beam filled with 0.20 g/cm3 foam reached the highest specific energy absorption; moreover, it absorbed more energy and reached much higher specific energy absorption than the foam-filled DC04 beam filled with the same foam, although the former one was nearly 54% lighter. The potential advantage of the foam-filled AZ31B beams is possibly associated with the high work hardening rate of AZ31B sheet in compression, which may involve more material in plastic deformation compared with the foam-filled DC04 beams. It has therefore been demonstrated that the hybrid structural design concept of the polyurethane foam-filled AZ31B beam has potential applications in auto-body structures.

Neuartige Leichtbau-Fahrzeugkonzepte durch Hybrid3-Strategie

Motiviert durch die Forderung nach weiterer Reduzierung des Kraftstoffverbrauchs und die Verringerung klimawirksamer Emissionen sind die Anforderungen an moderne Fahrzeugkonzepte hoch und werden weiter steigen. Um zukunftigen Herausforderungen wirtschaftlich begegnen zu konnen, empfiehlt sich die Konstruktion und Entwicklung nach der so genannten „Hybrid3“-Strategie.

New Materials and Construction Methods for Multi-Material Design. Lightweight Construction and Modularity in Future Vehicle Concepts

Besides reducing fuel consumption, the chief motivating factor behind the development of new vehicle structures is the desire to decrease climate-affecting emissions. One approach to addressing this involves reducing the vehicle mass and, as such, the various strategies relating to lightweight construction. Various methods of lightweight construction are used as a basis for deriving the technically relevant criteria for designs and material concepts. The work conducted in this field today centres around the synthesis of construction method and material development with the objective of devising a multi-material-design [1, 2]. Modularisation is an economic approach aimed at shaping the diversification of the vehicle concepts and implementing this effectively [3]. As a result of hybrid and later fuel cell drives, the requirements on the vehicle concepts will continue to grow in future. Modularisation also sometimes opposes the striving for a high level of integration. The modular lightweight concept of the DLR aims at designing powertrain evolutions in a scalable and cost-efficient manner and in a way that retains the concept flexibility or, in some cases, even increases this. These approaches lead to the strategy known as “hybrid3”. This strategy not only involves matching different materials and various construction methods with each other, but also taking account of the integration of functional effects. This entails, for example, optimising the design of thin-walled structural components in terms of their vibratory or acoustic properties with structure- integrated, active materials. Further examples of the approach with “hybrid3” effects could be selectable surfaces or integrated energy conversion. The various development directions are depicted in the form of a roadmap and discussed on the basis of forward-looking examples from the field of vehicle construction.

New Multi-Material Design Concepts and High Integration Light Metal Applications for Lightweight Body Structures

A major motivation for the development of new vehicle structures is, apart from the reduction of fuel consumption, is to decrease emissions which affect the climate. Therefore we also have to look at the reduction of vehicle weight and consequently at various strategies for lightweight construction. In the future steel structure concepts still show lightweight potential. But even more attractive potential for lightweight body in white structures could be realised by new multi-material design concepts and highly integrated light metal applications. Today’s research activities are focussed on the area of multi-material design, with the objective of placing the material with the best properties for the given requirements in the right position. Based on various methods of lightweight construction, techniques and tools, it is possible to find an optimum between lightweight design and costs. These activities will be illustrated by several research examples. One example will be the lightweight concept of the front module developed by the Institute of Vehicle Concepts (DLR) in the European research project -‘Super Light Car’ (SLC). By using aluminium in the front structure and the high pressure die casting strut tower the concept has a weight benefit of 32% compared to a steel reference structure. The methodology for reaching targets and requirements like weight reduction, crash performance and cost targets will be explained. Another example is a concept which is developed in the DLR project ‘Novel Vehicle Structures’. This concept shows the combination of different materials and a new construction method to increase front impact crash performance.

Influence of Corrosive Conditions on the Mechanical Performance of Flow Drill Screw Joints between Light Metals

In this paper, the influence of corrosive conditions on the mechanical performance of Flow Drill Screw (FDS) joints is investigated in greater detail. Different combinations of light metals such as aluminium or magnesium alloys and high strength/stainless steel served as the test material. The joint strength of FDS joints, under quasi-static and cyclic loading, was measured before and after six weeks’ of corrosion climate change testing. Furthermore metallographic sections of the samples were compared in order to evaluate the stage of surface, galvanic and crevice corrosion. To classify the effect of progressing corrosion on the mechanical properties of FDS joints, the following factors are taken into account: corrosion resistance of the materials, joining parameters and the geometry of the joint. For all material combinations there is an apparent change in both the fatigue strength and the failure behaviour after corrosion testing.

Next Generation Car – Lightweight Design Through Function Integration In Vehicle Structures

The „Next Generation Car” (NGC) project combines the research activities of the German Aerospace Center (DLR) in the area of road vehicles. The aim is the development of vehicle concepts and structures, with a high energy efficiency. Under the roof of NGC the DLR develops different vehicle concepts. The concepts have different aims and requirements, e.g. driving distance, number of passengers or maximum speed and should give answers for future vehicle structures. The challenge is to fulfill opposed requirements, e.g. mechanical performance (e.g. crash) and economical values (e.g. costs). At the example of the concept of the „Safe Light Regional Vehicle“ (SLRV) we will show the development of a light and safe body in white (BIW) structure. The BIW realizes special requirements, e.g. packaging, fatigue strength, stiffness and crash performance within a 2 passenger vehicle concept with a mass lower than 500 kg. The BIW design is a sandwich structure with a resulting structural mass of only 90 kg. Simulations indicate that the crash performance is very good, even if the mass of the BIW is so light. The simulations are validated by component crash tests. The result will be shown in this paper.

Next Generation Car — Example of Function Integration at the Light Urban Vehicle (LUV) Vehicle Concept

In times of climate change vehicle emissions have to be reduced clearly. One possibility is to reduce the mass of the body in white using lightweight sandwich structures. The department ‘Lightweight and Hybrid Design Methods’ of the Institute of Vehicle Concepts develops a vehicle body structure by using sandwiches with aluminum top layers and polyurethane foam as core material. For that the foam and the sandwiches were investigated under different load cases, e.g. pressure loading and in-plane tests. In tests with components the high potential of the sandwich materials were shown. On the dynamic component test facility of the institute, vehicle front structures were tested successfully. The results of all investigations regarding sandwich materials, integration of functions (e.g. crash, thermal) in vehicle structures and the concept LUV are developed under the research program of Next Generation Car of the DLR. We will show the development and results of the LUV.