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THE VEHICLE Technologies Office of the U.S. Department of Energy has worked with the Lightweight Materials National Laboratory Consortium in optimizing advanced automotive materials. The March 2018 issue of Tech Briefs summarizes aspects of this work. Here are tidbits from its article, “Pros & Cons of Advanced Lightweighting Materials.”
VTO and LightMAT Efforts. The Lightweight Materials National Laboratory Consortium links ten national labs, including Argonne, Lawrence Livermore, Oak Ridge, and Sandia.
DOE’s Vehicle Technologies Office works with them in activities of lightweight materials development and application. Studies involve advanced material sourcing, cost, engineering, and safety. Other aspects include modeling through computational material science and optimizing end-of-use recycling.
Light Weight = Fuel Efficiency. According to Tech Briefs, a ten-percent reduction in overall vehicle weight can result in a 6 to 8 percent fuel economy benefit: “Replacing traditional steel components with lightweight materials such as high-strength steel, magnesium alloys, aluminum, carbon fibers, and polymer composites can directly reduce the weigh of a vehicle’s body and chassis by up to 50 percent, and therefore reduce a vehicle’s fuel consumption.”
The payoff is particularly beneficial in hybrid electric, plug-in hybrids, and battery electric vehicles. The first two categories inherently add weight and complexity in their dual propulsion. Pure electric vehicles are challenged by battery weight, cost, and range limitations.
High-Strength Steel, as its name suggests, offers more strength and stiffness than traditional varieties of steel. Compared with aluminum, it has advantages of cost, formability, and corrosion protection.
On the other hand, its stamping equipment is more costly and wears out more quickly than those used with conventional steels. Also, there’s an inherent tradeoff of high-strength steel’s ductility and strength that complicates its forming and joining.
Aluminum is a familiar material that has had years of use in aerospace. Its light weight offers as much as a 60-percent savings compared to an equivalent steel component. Aluminum alloys exhibit good stiffness, strength, and energy absorption.
Tradeoffs include complex joining with other materials, possible electrolytic corrosion, and a higher cost than steels.
Magnesium is a special-application star of lightweight metals, offering as much as a 70-percent weight savings. It has high stiffness and strength; it’s also amenable to thin-wall casting of components such as sub-assembly closures, bracing, and brackets.
Magnesium is expensive, however, and has challenges in manufacturing, repair, and recycling. If ignited, for example, its transformation to magnesium oxide is extremely difficult to extinguish. Tech Briefs also notes a “lack of availability from U.S. manufacturers in large quantities to meet automotive needs.”
Carbon Fiber Composites offer high strength and stiffness. Half the weight of steel, they’re four times stronger. What’s more, fiber directionality can be optimized specifically for applications.
These materials appear in high-performance cars, however, according to Tech Briefs, cost and fabrication complexities are “generally too high for use in popular models.”
Titanium is cited by Tech Briefs for its use in “powertrain systems to reduce weight by up to 55 percent” It offers an excellent strength-to-weight ratio, can withstand high temperatures, and is used in engine valves, springs, and other specialized applications.
Tradeoffs include high material costs and formability challenges, neither of which hamper titanium’s widespread use in Formula One and in high-end eyeglass frames. ds
© Dennis Simanaitis, SimanaitisSays.com, 2018