Bumper boost for crash protection in lightweight vehicles

Lightweight aluminium cars and trains will no longer need to rely on heavy steel bumper beams and crash boxes for impact protection, thanks to advanced aluminium alloys and casting techniques being perfected at Brunel University London.

The Brunel Centre for Advanced Solidification Technology (BCAST), a global leader in metallurgical casting research, is working closely with foundry partner Sarginsons Industries and others on the development of high-performance cast aluminium alloys as part of the Lightweight Energy Absorbing Aluminium Structures for Transport (LEAAST) project.

Two aluminium alloys have been developed within the project and have proven to be successful in industrial trials, with improved strength and ductility.

The new 6xxx series wrought alloy can provide yield strength and elongation of more than 500 MPa and 10%, respectively. The new 3xx series cast alloy is about three times lighter than steel and, compared with previous alloys, has yield strength of 310 MPa, ultimate tensile strength of 365 MPa and elongation of 10%. This provides a ratio of strength to density that enables parts made from these alloys to absorb the required stresses and deform in a controlled manner under impact.

The three-year, £2.2 million LEAAST project, which began in May 2015, is funded by Innovate UK, and involves 10 industrial partners and research institutions led by Jaguar Land Rover to develop future lightweight aluminium crash management systems for automotive and rail applications.

BCAST, as the only university-level research institution involved in the crash management aspect of the LEAAST project, is working on the development of high-performance wrought and cast aluminium alloys, the recycling of aluminium alloys using melt-conditioned direct chill casting, and the overcasting technology, in which metals with lower melting temperature are cast over higher-melting alloys to optimise weight and performance.

Reducing dependence on steel
Sarginsons Industries, a global leader in lightweight castings, is working with BCAST to develop the high-ductility aluminium alloys using overcasting techniques to demonstrate the potential for both increased crash resistance and weight saving.

Industrial trials at Sarginsons Industries of the BCAST-developed high-performance cast aluminium alloy using a Jaguar Land Rover component

“Lightweight crash management systems are of increasing importance for most forms of ground transport. While at present many automotive original equipment manufacturers have advanced aluminium automotive body designs, they still depend on steel for bumper beams,” said Anthony Evans, Managing Director at Sarginsons Industries in Coventry.

“Delivering fully sustainable and high-ductility alloy is critical for providing the automotive industry with light weighting options to counter the higher-weight battery and hybrid vehicle base loads.”

“The first scale-up trial has just been completed with the new casting alloy being tested in a 400 kilograms melt batch and controlled manufacturing conditions at Sarginsons, and the results are extremely positive. At least a 30% increase in yield strength has been achieved with the new alloy, while maintaining its high ductility.”