Every time CAF&EACUTE; standards come up for discussion, the debate over the effect weight and size have on occupant safety comes to the fore. "There is this tendency to equate lightweighting and downsizing," says Mike Bull, director of Automotive Technology, Novelis Corp. (Novi, MI; www.novelis.com), "when they are not the same thing in terms of crash performance." Not wanting to be left out of the twin debates over fuel economy and safety, the Aluminum Association (Troy, MI; www.autoaluminum.org) commissioned a study showing how lightweight materials can preserve vehicle size and safety performance while improving fuel economy. "We want to make sure aluminum isn't left out of the debate by having regulators concentrate on weight as the overriding safety factor like they have done in the past," says Tom Gannon, v.p., Sales and Marketing, Novelis.
After selecting the Ford Explorer as the typical SUV, the team created an aluminum version with the same crash pulse as its steel counterpart by calibrating it against the Explorer's actual NCAP (National Crash Assessment Program) results. Five hundred moderately severe crash scenarios were chosen from available crash data and tests were run and calibrated for each. "This gives an apples-to-apples comparison," says Bull. It also prevents the group from picking only those accident types that put aluminum in the best light.
Nearly 900 lb lighter than its steel counterpart, the virtual Explorer's sheet aluminum unibody accounted for 450 lb of that tally. Secondary weight reductions (lighter suspension pieces, smaller engine, etc.) made up the rest. As expected, fuel economy rose while size and safety were undiminished. The cost of this vehicle, however, also rose higher than the $1/lb automakers are willing to spend to reduce weight. "We realize the first generation of a vehicle like this is going to cost the OEM more," says Bull, "but that number will diminish in successive generations."
Bull also believes the difference can be offset by substituting aluminum for steel in an amount equal to the cost of an alternate powertrain. "Aluminum belongs in that discussion," says Bull, "because it offers many of the same fuel economy benefits, but its advantage is available under all driving conditions and for all powertrains. Unfortunately, it's often overlooked." A study comparing these approaches currently is under consideration.