Bitumen heavy layers as in steel vehicles need to be used. Simulation studies have shown that lower stiffness of aluminium must be compensated for. An overall weight reduction of 40% seems obtainable with good acoustic behaviour.
The use phase is the largest energy consumer and source of CO2 emissions. It is about ten times larger than the production phase calculated on the lifetime of the car. The method used gives high credit to recycled material, which makes recycling very profitable and necessary to lower CO2 emissions. The conclusion of this comparison evaluated with the EPS system is that the difference between aluminium and steel over the total life cycle is very small.
Good crash performance can be obtained using profiles in aluminium for the front end of a vehicle. Simulation of the performance gives good agreement and rules have been established to understand where the simulation differs from the real case. The calculation tends to overestimate the stiffness.
Direct Welded Node Design
The calculated figures and diagrams coming from the impact software modules were more precise than expected. Direct welded joint design is consistent with any vehicle package. Static crush-tests confirmed the design of the main energy-absorbing elements was acceptable. The dynamic crash of the front structure confirmed the advantages of using aluminium for energy absorbing reasons. The correlation between calculation and test results was good.
Sheet Node Design
Stamped sheet node design avoids rigid constraints during the assembly process without specific processing of the beams. Sheet nodes exhibit stiffness values comparable to conventional design with a weight saving of 15 to 30% while the impact behaviour was poor. Adhesive bonding has been seen to be the best joining technique to assemble sheet nodes and butt welding is also acceptable.
Cast Node Design, Integration and Repair
Cast nodes have been proven although they are high cost parts. Complicated designs which integrate a number of features such as the hinge reinforcements can be manufactured to fairly good tolerances. The integration of all other vehicle features into a spaceframe vehicle is relatively straightforward with no major concerns regardless of the node technique employed. A set of procedures for damage repair indicate that repair is feasible although more expensive than for steel vehicles.
Design of Hydroformed Front End
The hydroformed front end work showed that this technology can be used for production of structural body parts in aluminium. The main limitation is the low elongation of aluminium which allows only small changes in profile sizes. The parts showed a loss of 7% compared to the steel version with a weight reduction of 7%.
The proposed research is directed at developing design rules for low weight (low CO2 emission) aluminium spaceframe vehicles. The European automotive industry has no experience of designing this type of vehicle and so guide-lines need to be established to enable effective designs to be produced in terms of static and dynamic performance. The project will concentrate on establishing the design potential of aluminium extrusion together with three types of node to give the maximum scope for originality in production vehicles. The major research tasks are:
i) development of design guide-lines for aluminium profile designs,
ii) development of design guide-lines for direct welded nodes,
iii) development of design guide-lines for sheet fabricated nodes,
iv) development of design guide-lines for aluminium cast nodes,
v) development of rules for large scale sub-assemblies,
vi) development of rules for integrating power train, panels and trim into a spaceframe,
vii) establish a system for major damage repair of an aluminium spaceframe,
viii) establish guide-lines for acoustically optimized aluminium related construction,
ix) establish environmental ecobalance for aluminium spaceframe vehicles.
Successful completion of the project will enable the automotive partners to design low weight aluminium spaceframe vehicles with lower CO2 emissions over their lifetime.
Funding SchemeCSC - Cost-sharing contracts
CV31 1TR Leamington Spa