Losing the weight requires more than material substitution
Graeme Stewart – Managing Director Vehicle Systems, Ricardo
The game paper-scissors-stone revolves around three items, each of which ‘beats’ one of its counterparts while at the same time being beaten by the other. It’s a simple three-way conundrum that can never really be solved – although that hasn’t stopped mathematicians and game theorists studying it, or Japanese Electronics firm Maspro Denkoh using it to choose whether Christies or Sotheby’s should win the contact to sell its $20 million corporate art collection.
It might be tempting to think of the lightweighting challenge in vehicle engineering in similar terms. The conventional pressed and welded steel monocoque construction favoured by the world’s leading automakers for over half a century clearly has very tangible advantages in terms of practicality and cost. Surely, despite its greater welding and joining challenges, aluminium always beats steel on weight yet gets beaten on cost? And don’t carbon fibre composites beat the both of them hands down on weight, while sending costs through the roof? To view things in such a simplistic manner is of course to vastly overlook the design potential offered by the superior mechanical properties offered, for example, by aluminium, carbon fibre composites, and even ultra-high-strength steel grades.
For the decades when cost and durability were perhaps considered by new product planners to be significantly more important than fuel economy, refinement of the conventional steel bodied construction methods understandably prevailed. In the modern era, however, where fuel economy and CO2 emissions are also taking centre stage, vehicle engineers have the opportunity for the first time in generations to be more innovative in design and engineering, in order to realize the full benefits of the materials that they are now able to use.
We at Ricardo have been involved in many specialist and military projects in recent years where fuel economy has been pushed to the limit and carbon fibre composites have been deployed to provide the ultimate balance between weight saving and robustness. At the other end of the scale we have examined conventional steel structures such as sub-frames, and demonstrated weight savings in the region of 30 percent without compromising any of the performance characteristics by using our leading edge analysis capabilities to redesign structural components to take maximum advantage of the latest grades of steel.
And we are far from alone, as the latest generation of Ford’s iconic F-150 truck demonstrates. A top selling US product for three decades, Ford has redesigned the product to make the very best use of materials in what is the first mass-produced truck in its class featuring a high-strength, military-grade, aluminium-alloy body and bed.
In considering new materials for body and chassis structures, it is crucial to move beyond mere substitution as a means of saving weight, as that will almost always fail to realize the full potential of the new material. We stand at the cusp of a new era where we have a requirement to achieve unprecedented levels of fuel economy, but we also have a wealth of new materials to choose from and we have advanced design and simulation capabilities to explore new avenues in design optimization. As such, in my view there has never been a more exciting time for vehicle engineering.
This view point featured in RQ Q4 2014 - click here to download the full publication.