Aluminum Space Frame Research Articles

Developments of Audi Space Frame Technology for Automotive Body Aluminum Construction

With ASF (Audi Space Frame) technology, Audi has completely reinvented the body construction using aluminum as a material and a concept adapted to light metal. ASF technology has undergone developments that efficiently exploit the knowledge accumulated from the efficient use of aluminum alloys, the optimization of casting and profiling processes, to the most appropriate techniques for joining components. The paper analyzes the main technical and technological developments adopted by Audi in designing and manufacturing the aluminum space frame for the car body.

Study on the Quantitative Relationship between Static Stiffness and Modal Parameters of an Aluminum Space Frame

Study on the Quantitative Relationship between Static Stiffness and Modal Parameters of an Aluminum Space Frame

Fixtureless Alignment of Joining Partners within the Assembly of Aluminum Space Frame Structures

Light-weight aluminium space frame structures are frequently used for small-volume products, such as sports cars. The assembly of these products has so far been mainly manual and requires the use of complex and expensive fixtures. To increase the profitability, the research conducted at wbk Institute of Production Science is aiming to achieve an automated, fixtureless assembly of such structures by the use of industrial robots. To achieve the required accuracies regarding the alignment of the joining partners, a new approach based on component-inherent markings has been developed. This article describes the approach for the fixtureless positioning of components and the validation of the marking detection.

Net-Shape Forming of a Roof Joint Node by Thixoforming of A357 Aluminum Alloy for a Low Speed Electric Vehicle

In the present study, process developments for net-shape forming of aluminum roof joint node have been described. These joint node parts were designed for low speed electric vehicles of which operating condition is more moderate than general compact cars. Thixoforming of Al-7%Si-0.5%Mg (A357) alloy has been applied to the net-shape forming of a complex roof joint node to support aluminum space frame structure of low speed electric vehicle. Optimum heating temperature for the A357 billet was between 580 and 585°C corresponding to the semi-solid temperatures showing 20-30% of liquid fraction. An injection speed of around 100mm/s and preheating of die at temperatures of 200~250°C were also necessary conditions to obtain reasonable thixoformed parts.

Spatial alignment of joining partners without fixtures, based on component-inherent markings

Light-weight aluminum space frame structures are frequently used for small-volume products, such as sports cars. The assembly of these products has so far been mainly manual and requires the use of complex and expensive fixtures. To increase the profitability the research conducted at wbk Institute of Production Science is aiming to achieve an automated, fixtureless assembly of such structures by the use of industrial robots. To achieve the required accuracies regarding the alignment of the joining partners, a new approach based on component-inherent markings has been developed. Different tests have already been conducted in order to validate the approach. The test results demonstrate that the approach is suitable for the spatial alignment of components.This article describes the theoretical foundations of the required measurement approach as well as the experimental results.

Crashworthiness of Aluminium Structures - An Illustration Through Scaled Model

The use of aluminium in aerospace structures is predominantly high for being one of the best candidates to achieve light weight with sufficient crashworthiness characteristics. This paper supports the study of aluminium-based vehicle crashworthiness through an aluminium space frame scaled model. Within the limitations of the availability of the extruded tubes, the current study reports about correlation of physical testing and simulation practice along with the visualisation of the crush behaviour of scaled model. An in-house Impact Testing Machine (ITM) is used for testing of the scaled vehicle model. The use ITM is justified using an extruded aluminium tube impact testing and its correlation with finite element simulation. With this confidence the same procedure was used for carrying impact test on scaled vehicle model. The results from physical test and simulation were correlated satisfactorily supporting the simulation procedure. The test results also helped in visualising the crush space behaviour of...

High-Stiffness, Lock-and-Key Heat-Reversible Locator-Snap Systems for the Design for Disassembly

Driven by the moral sense of obligation, legislative and social pressures, manufacturers now consider effective part reuse and material recycling at the end of product life at the design stage. It is a key consideration to use joints that can disengage with minimum labor, part damage, and material contamination. This paper extends our previous work on the design of high-stiffness reversible locator-snap system that can disengage nondestructively with localized heat (Shalaby and Saitou, 2006, “Optimal Heat-Reversible Snap Joints for Frame-Panel Assembly in Aluminum Space Frame Automotive Bodies,” Proceedings of the LCE2006: The 13th CIRP International Conference on Life Cycle Engineering, Leuven, Belgium, May 31–Jun. 2, pp. 411–416; Shalaby and Saitou, 2008, “Design for Disassembly With High-Stiffness, Heat-Reversible Locator-Snap Systems,” ASME J. Mech. Des., 130(12), p. 121701) to include (1) modeling for tolerance stack-up and (2) lock-and-key concept to ensure that snaps only disengage when the right procedure is followed. The design problem is posed as an optimization problem to find the locations, numbers, and orientations of locators and snaps, and the locations and sizes of heating areas, to release the snaps with minimum heat, compliance, and tolerance stack-up. The motion and structural requirements are considered constraints. Screw theory is employed to precalculate the set of feasible types and orientations of locators and snaps that are examined during optimization. Multi-objective genetic algorithm coupled with structural and thermal finite element analysis is used to solve the optimization problem. The method is applied on two case studies. The Pareto-optimal solutions present alternative designs with different trade-offs between the design objectives.

Optimal heat-reversible snap joints for frame-panel assembly in aluminium space frame automotive bodies

This paper presents a method for designing heat-reversible snap joints, locator-snap systems that detach non-destructively by heating a certain location of parts. It is expected to dramatically improve the recyclability of aluminium space frame (ASF) bodies by enabling clean separation of frames and body panels. Extending our previous work on the sequential design of the locators and heating area (Shalaby and Saitou, 2005), the method simultaneously optimises locators, heating area and snaps for ensuring joint detachment with minimum heat and avoiding resonance due to vehicle vibration. A multi-objective genetic algorithm is utilised to search for Pareto optimal design alternatives.

Off-Set Roller Bending of Aluminium Space-Frame

In the proto-type bending machine reported in the previous paper, the Bending Roller was fixed in the same position during bending. Therefore, almost uniform curvature in longitudinal direction was obtained. We improved the machine as the Bending Roller can be moved by a servo motor. By this improvement, we can bend aluminium space-frame into varied curvature in longitudinal direction. The curvature of a bent aluminium space frame is different from the setting curvature calculated from the moving position of the bending roller, because so called spring back occurs. We found out that the abrupt increase of objective curvature causes collapse of the specimen and we cannot obtain the objective curvature. And the sudden decrease of the objective curvature by sudden decrease in position of bending roller cannot be realized because of the outbreak of gap between the bending roller and the bent space-frame. If we avoid the abrupt change of the objective curvature, we can compensate the spring-back and we can get the objective curvature.

Structural analysis and optimization of a low-speed vehicle body

The low-speed vehicle (LSV) is being employed for various usages. The body of the LSV is usually made of the aluminium space frame (ASF) type rather than the monocoque or unitary construction type. The reason is that it is easier to reduce mass efficiently while the required stiffness and strength are maintained. A design flow for the LSV is proposed. Design specifications for structural performances of the LSV do not yet exist. Therefore, they are defined through a comparative study with general passenger automobiles. An optimization problem is formulated by the defined specifications. First, the A-pillar which has an important role in structural performance is selected, and the candidates of reinforcement in the pillar are determined from topology optimization to maximize the stiffness. Based on this, the thicknesses of the cross-sections are determined to minimize the mass of the body while design specifications are satisfied. The optimum solution is compared with an existing design. The optimization process has been performed using a commercial optimization software system, GENESIS 7.0.

332 DLCコーティングダイスを用いたアルミニウムの可変断面押出し(塑性加工の動向とその展開4)

Aluminum space-frame is one of the candidates to be applied to a structure of car bodies in future because of its light weight as well as high strength. To omit the secondary forming process in the production of aluminum space-frame, variable shape extrusion apparatus employing a taper mandrel and four movable dies has been developed and the characteristics of hot extrusion were investigated. As a result, the step mandrel provides good dimensional accuracy due to its bearings which is parallel to the extruding direction. On the other hand, severe pick-up occurred easily on the surface of extrusions by using the step-mandrel. DLC coated dies has a remarkable effect to suppress generation of pick-up even under extrusion temperature of 673K.

Design and Execution of Aluminium Space Frame Advertising Panels and Towers

Space frame modular construction systems are widely employed as a support for advertising panels, mainly for their strength, modularity, and lightness. In recent times, solutions based on aluminium extruded profiles have demonstrated their capability to solve successfully the problem with high corrosion resistance, and low maintenance costs.The space frame systems made with aluminium components allow for a very large set of possible solutions, while unifying the possibility to fix neon filled boxed letters, fabric or solid panels, flags or other advertising devices.Moreover, the system is very light and can be lifted to the building roof and composed without the help of huge cranes and machinery.Very often, the solution of the advertising system atop a commercial centre is defined only few days before the opening of the centre; without designing the centre roof with support points able to resist the very large wind forces that act on the provided panels.In these situations, the capability of the modular systems to adapt their shape and support concept in order to connect the available roof strong points with the panel supporting frame is extremely useful. Therefore, the aluminium modular frame solutions are superior to every other possibility.In this paper, the design of an aluminium space frame is summarized, with reference to a large set of constructed advertising towers and panels. The problem of the evaluation of the wind forces is outlined and useful remarks about the fatigue resistance of aluminium components are drawn.Careful presentation of the design criteria of some outstanding installations gives information about the wide set of problems that these adaptive structures can easily solve.

Bending Performance Analysis of Aluminum-Composite Hybrid Tube Beams

Bending deformation and energy absorption characteristics of aluminum-composite hybrid tube beams have been analyzed for improvement in the bending performance of aluminum space frame by using experimental tests combined with theoretical and finite element analyses. Hybrid tube beams composed of glass fabric/epoxy layer wrapped around on aluminum tube were made in autoclave with the recommended curing cycle. Basic properties of aluminum material used for initial input data of the finite element simulation and theoretical analysis were obtained from the true stress-true strain curve of specimen which had bean extracted from the Al tube beam. A modified theoretical model was developed to predict the resistance to the collapse of hybrid tube beams subjected to a bending load. Theoretical moment-rotation angle curves of hybrid tube beams were in good agreement with experimental ones, which was comparable to the results obtained from finite element simulation. Hybrid tube beams strengthened by composite layer on the whole web and flange showed an excellent bending strength and energy absorption capability.

Campbellology for Ferrari

With the need to save weight, increase performance and reduce costs, in 1996 Ferrari opted to use an all aluminium spaceframe chassis for the 360 Modena car. The design partnership of Ferrari and Alcoa called for a mix of extrusions welded to 12 strategic castings. The present study describes how the foundry process and methods were developed utilising the John Campbell philosophy as a basis for achieving the quality targets for the casting components.

Optimal Subassembly Partitioning of Space Frame Structures for In-Process Dimensional Adjustability and Stiffness

A method for optimally synthesizing multicomponent structural assemblies of an aluminum space frame (ASF) vehicle body is presented, which simultaneously considers structural stiffness, manufacturing and assembly costs and dimensional integrity under a unified framework based on joint libraries. The optimization problem is posed as a simultaneous determination of the location and feasible types of joints in a structure selected from the predefined joint libraries, combined with the size optimization for the cross sections of the joined structural frames. The structural stiffness is evaluated by finite element analyses of a beam-spring model modeling the joints and joined frames. Manufacturing and assembly costs are estimated based on the geometries of the components and joints. Dissimilar to the enumerative approach in our previous work, dimensional integrity of a candidate assembly is evaluated as the adjustability of the given critical dimensions, using an internal optimization routine that finds the optimal subassembly partitioning of an assembly for in-process adjustability. The optimization problem is solved by a multiobjective genetic algorithm. An example on an ASF of the midsize passenger vehicle is presented, where the representative designs in the Pareto set are examined with respect to the three design objectives.

Decomposition-Based Assembly Synthesis of Space Frame Structures Using Joint Library

Abstract This paper presents a method for identifying the optimal designs of components and joints in the space frame body structures of passenger vehicles considering structural characteristics, manufacturability, and assembleability. Dissimilar to our previous work based on graph decomposition, the problem is posed as a simultaneous determination of the locations and types of joints in a structure and the cross sections of the joined structural frames, selected from a predefined joint library. The joint library is a set of joint designs containing the geometry of the feasible joints at each potential joint location and the cross sections of the joined frames, associated with their structural characteristics as equivalent torsional springs obtained from the finite element analyses of the detailed joint geometry. Structural characteristics of the entire structure are evaluated by finite element analyses of a beam-spring model constructed from the selected joints and joined frames. Manufacturability and assembleability are evaluated as the manufacturing and assembly costs estimated from the geometry of the components and joints, respectively. The optimization problem is solved by a multiobjective genetic algorithm using a direct crossover. A case study on an aluminum space frame of a midsize passenger vehicle is discussed.

Decomposition-Based Assembly Synthesis of Multiple Structures for Minimum Manufacturing Cost

An extension of decomposition-based assembly synthesis for structural modularity is presented where the early identification of shareable components within multiple structures is posed as an outcome of the minimization of estimated manufacturing costs. The manufacturing costs of components are estimated under given production volumes considering the economies of scale. Multiple structures are simultaneously decomposed, and the types of welded joints at component interfaces are selected from a given library, in order to minimize the overall manufacturing cost and the reduction of structural strength due to the introduction of joints. A multiobjective genetic algorithm is used to allow effective examination of trade-offs between manufacturing cost and structural strength. A new joint-oriented representation of structures combined with a “direct” crossover is introduced to enhance the efficiency of the search. A preliminary case study with two simplified aluminum space frame automotive bodies is presented to demonstrate that not all types of component sharing are economically justifiable under a certain production scenario.

Mayflower part of GT40 ‘Dream Team’

A British company is playing a key role in the design, development and production of the latest version of Ford’s legendary GT40 ‘supercar’, which will be built using an aluminium space frame structure and skin panels. The GT40 will be a new technology demonstrator, watched closely by Jaguar Cars’ engineers at Whitley, Coventry, UK.

330 Effects of Configurations and Dimensions of CFRP on Impact Strength and Absorbed Energy of CFRP Aluminium-Alloy Hybrid Beams Bonded Adhesively

Aluminium space frame structures have been available to produce the body structures of lightweight automobiles. However, the aluminium alloy beams don't have enough strength under impact bending. In the case, bonding Carbon Fiber Reinforced Plastics (CFRP) adhesively on the beams is effective way to increase the impact strength and the absorbed energy. In the study, the impact strength and the absorbed energy of the hybrid beams consisting of aluminium-alloy and CFRP were investigated analytically and experimentally. In addition, the effects of changing the configurations and dimensions of CFRP on the impact properties of the beams were discussed based on the experimental results. The absorbed energy of the hybrid beams depended on both the thickness and length of the CFRP plates. Therefore, critical dimensions of CFRP must exist in terms of the impact strength of the beams. A simulation method to predict the critical dimensions using FEM was established considering non-liner stress-strain relations and strength of adhesive.

414 可変断面押出しにおけるマンドレル形状の成形品精度への影響(OS 塑性加工)

Recently, the development of aluminum car body which employs aluminium space-frame structure has been paid strong attention in terms of it's light weight as wel as safety preservation . In this study, a novel extrusion equipment, that uses a taper mandrel and four movable dies, was developed to obtain a smooth and valuable cross-section to omit the secondary process of aluminum space frame. By using this equipment, extrusion experiments of aluminum alloy are carried out, and variable shape square pipes with extrusion ratio of 2-10 are produced.