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Long life public service vehicle project study

Objective

The aim of the project is the production of a concept frame call for PSV vehicles in aluminium alloy using adhesive bonding in combination or/not with joining methods.
The main results conclusions to be drawn from the work can be summarized as follows:

- An adhesive bonding technology was developed comprising the optimization of a structural adhesive, TEROKAL 5045, and surface treatment

- Proprietary extruded aluminium alloy sections were developed for the fabrication of a bus framework

- The framework structure meets the requirements of flexural and torsional strength and stiffness normally specified for steel structures

- A 30% weight reduction of the bus structure was obtained

- Durability of bonded joints under cyclic load conditions evaluated with small and large scale specimens met the target of 2 x 10{6} cycles

- Ageing of bonded joints under varying humidity/temperature conditions and salt/spray testing did not impair significantly its strength and impact strength

- The full scale rollover test carried out following in every detail the procedures specified by the ECE Regulation 66.

- The rollover test clearly demonstrated the feasibility of meeting the rollover safety criteria by bus bodies made of the adhesive bonded aluminium extrusions, even when the safety structure is based on the whole body and not on specially reinforced rollbars.

- The reference test concerned the lower (and lighter) version of the Salvador Caetano aluminium vehicle. It was the first of its kind ever, both as regards aluminium as a building material and adhesive bonding as means of putting the structure together.

- Most of what was achieved also represents a 'first-off' matter and hence it is also worthwhile to note that this was achieved using:
- only one set of aluminum extrusions for the pillar, floor rail, cant rail and side with waistrail (i.e. the goal was achieved within the very first attempt both at the component and overall structure levels),
- local reinforcements at the roof corners, thus avoiding a too heavy and expensive cantrail,
- beam and roof joint strength with 5 to 8 times higher strength and energy absorbing capacity than the conventional (non-crashworthy) components typically used in aluminium buses,
- simple seat reinforcement as a significant safety element that enabled the floor rail and side structures to be controlled largely by the normal service conditions, rather than safety.

- The structure in the test behaved very close indeed to the predictions as regards all the main features, i.e.:
- the collapse mode and maximum deformations were very close to those aimed for (i.e. no overdesign) and, indeed, to those predicted;
- the potential problem with adhesive separation at the impacted cant rail occurred at a deformation stage very close to that observed under static tests;
- the second test without the roof corner reinforcements failed the test, as predicted by the preceding analysis.
It is an integrated, multidisciplinary project in that it covers the materials selection, design manufacturing processes and application requirements dictated by relevant international regulations.

- Overall geometry of the structural cell must comply with ECE 36 regulation
- Strength and stiffness must not be less than that currently specified for steel structures
- Aim for a 45 % weight reduction
- Crash resistance in roll-over accidents following regulation ECE 66
- Cell structure durability under fatigue loads and corrosion resistance adequate for long term application (i.e. longer than for current steel structures)
- Ease of manufacturing and cost effective fabrication.

Since the frame design is dominated by the beam sections used and joint performance, the research project will focus on the following objectives :

- design layout of structural frame similar to current practices
- selection of aluminium alloy on the basis of strength, formability and energy absorption
- evaluation of structural adhesives and manufacturing process
- design joints and beam sections for stiffness and strength
- design joints and beam for impact loads (crash resistance)
- design joints and beam sections for fatigue durability
- evaluation of structural cell assembly performance in roll-over test.

The innovative character of the project derives from the following aspects :

- use of adhesive bonding with aluminium alloy in a structural application with stringent requirements of strength, stiffness and crash-worthiness
- development of FEM model for the evaluation of crash-worthiness of components and complete structure with adhesive bonded joints
- modelling of adhesive joints under shear and peel loads
- fatigue durability analysis of bonded aluminium joints durability under alternate climate conditions and exposure to salt spray.

Coordinator

INEGI
Address
Rua Dos Bragas - Feup
4099 Porto Codex
Portugal

Participants (4)

ALUSINGEN GMBH
Germany
CRANFIELD IMPACT CENTRE LTD.
United Kingdom
Address
Wharley End
MK430JR Cranfield,bedford
SALVADOR CAETANO
Portugal
Teroson GmbH
Germany
Address
Hans-bunte-straße 2-4
69123 Heidelberg