Chrysler/McMaster lightweight materials project focusing on door side impact beam; Al and Mg casting
In October 2013, Chrysler entered a $3.9-million research project supported by the Canadian government to explore ways to leverage the weight-saving properties of aluminum and magnesium alloys for vehicle production. (Earlier post.) The primary academic partner in the project is McMaster University in Ontario, with Ryerson University and CANMET, an agency of Natural Resources Canada, as other partners in the project.
In an update on the progress of the project, Steve Logan, responsible for Advanced Lightweight Programs in Chrysler’s Materials Engineering Group, said that the team is looking at components for body and chassis, and specifically focusing on a door side impact beam.
The team is developing a side impact beam to put into a current production vehicle for evaluation, Logan said. The first part of the project is to develop a casting process to make the part, the second will be testing the part and making any needed modification. Overall, the weight reduction target for the part is about 40%.
The project is exploring two approaches:
Developing a new casting process for a new aluminum alloy McMaster has been working on for several years; and
Developing a casting process to allow the use of an existing Mg alloy that already exists, but that is hard to cast.
It’s a demanding application. Currently, we use a high strength boron-type steel that is hot stamped. High strength materials are harder to form. We could replace that with a high strength aluminum alloy, stamped, but it would be more expensive—which is why we are looking at this project with McMaster. If we could cast it, we wouldn’t have to stamp it, making it easier.—Steve Logan
Chrysler Group currently makes innovative use of both aluminum and magnesium. Every Ram 1500 full-size pickup, the company’s top-selling vehicle, features an aluminum hood; while the SRT Viper supercar features a structural dashboard component that is the largest single piece of magnesium found in any production vehicle.
There is no silver bullet to improve vehicle fuel economy, so Chrysler Group is actively exploring every technology that shows promise. Proliferating the use of strong, lightweight materials such as aluminum and magnesium is among the most promising avenues to reduce the energy demand on vehicle powertrains. Reductions in energy demand are key contributors to improved fuel economy.—Tony Mancina, Head of Chrysler Group’s Automotive Research Development Center
There are a number of factors at play in deciding where to focus on taking out weight, Logan said, including cost, manufacturability, vehicle attributes (e.g., taking weight out in the front end for handling), and legal mandates (e.g., weight classes).
It's very much program-specific and unique. How we decide how much goes into aluminum and magnesium vs. carbon fiber is not particularly clear because it depends on the specific components. We are not doing a whole lot with carbon fiber except on specialty applications; it is still very expensive. While it may save more than aluminum, it’s not a lot more.—Steve Logan
The most bang for the buck on weight reduction comes primarily from the body-in-white (the body structure), Logan said. Taking enough weight out of the body also enables mass compounding benefits—e.g., a lighter car enables the use of a smaller, lighter engine.
Major alterations to the BIW (such as Ford’s embrace of aluminum in the new F-150), however, can entail changes to joining processes, the body shop, the paint shop, and so on. It can be an expensive risk that might not turn out too well if something goes wrong, Logan suggested.
Accordingly, Chrysler is focusing on “the bolt-on applications”, such as on the Dart, which has a number of aluminum chassis components, but without the risk and investment of a major shift, Logan said.
Chrysler is also involved with McMaster on a US Department of Energy (DOE) project to develop lightweight joining process for dissimilar metals—e.g., magnesium to other metals.