LIGHT-WEIGHT MAGNESIUM, ALUMINUM IN LINCOLN MKT LIFTGATE CUTS WEIGHT, BOOSTS FUEL ECONOMY
Over the next decade, Ford Motor Company is planning vehicle weight reductions ranging from 250 to 750 pounds that will help it meet stringent fuel economy targets without compromising vehicle safety or durability. One of the ways Ford has reduced mass in its latest offerings is through the use of light-weight materials such as aluminum and magnesium.
The company’s newest addition, the 2010 Lincoln MKT seven-passenger crossover, is the first mainstream North American vehicle to feature a liftgate constructed from a combination of magnesium and aluminum, which makes the liftgate approximately 40 percent lighter than if it was made from standard steel.
Mastering New Materials
Ford’s body structure technical experts, whose research was presented at SAE International’s 2009 World Congress this week, say one of the keys to maximizing fuel economy through the use of advanced materials is the extensive use of computer-aided engineering (CAE) to select the appropriate material and minimize its thickness without sacrificing durability and structural integrity.
CAE modeling proved essential to the challenging design and development of the MKT liftgate – the largest in the company and possibly the largest thin-walled magnesium closure panel in the North American industry. The die casting process enabled the MKT team to fine-tune the part’s shape in a way that wouldn’t have been feasible in a stamped sheet metal part.
Although magnesium raw material cost is a more expensive material than steel, the team determined that an all-steel MKT liftgate would have been too heavy for available power-lift systems to open, and more complicated and expensive to manufacture than one made of magnesium and aluminum.
In addition, the use of magnesium and aluminum afforded more design flexibility than steel, enabling the MKT’s swept-forward bustle-back styling without sacrificing interior rear-seat headroom. Its materials also allowed for a smooth transition from the liftgate to the bumper, which is uncommon in production vehicles.
Right-sizing Power to Weight
Material experts, body and powertrain engineers expect vehicle weight reduction to account for up to 50 percent of future fuel economy improvements, according to the study commissioned by the Aluminum Association. The study participants also said that replacing heavier materials with light-weight materials is nearly as important as hybrid technology for automakers to meet the expected increase in the corporate average fuel economy (CAFE) by 2020.
Weight reduction alone isn’t enough to significantly improve fuel economy. By itself, a 10 percent reduction in weight results in approximately a 3 percent improvement in fuel efficiency. However, if the powertrain is re-matched, the fuel economy improvement increases to roughly 7 percent. Weight reduction combined with powertrain re-matching not only improves fuel economy, but helps maintain overall performance (as compared to a heavier vehicle with a larger engine).
By using magnesium and aluminum instead of steel on the MKT liftgate, the vehicle lost 22 pounds. That, along with other weight saving measures gives the MKT fuel economy among the best in its class.
QUOTES
“The MKT’s liftgate is a breakthrough achieved by our scientific research team, product design team and our supplier, who overcame significant technical challenges to develop it. The use of magnesium and aluminum in the MKT marks a new direction for liftgates and closures in general.” – Randy Frank, Closures Chief Engineer, Ford Product Development
“Because it is cast instead of stamped, we are able to develop variable thicknesses. We did extensive CAE analysis to see how the magnesium would functionally perform in a high impact event and made structural improvements such ribbing for added strength.” – Cindy Wetzel, Design and Release Engineer of Liftgates, Ford Product Development
Tags: 2010 Lincoln MKT, aluminum, Ford, Ford Motor Company, light-weight, Lincoln, magnesium, vehichle weight
