Car Wars: Aluminum v. Steel, Episode Two

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This is the second part in a multi-part series. Keep an eye out for the next installments in the coming weeks. You can read the first post here.

Safety has long served as a key buying criteria for consumers looking to purchase a new car. One need only look at Consumer Reports or the Insurance Institute for Highway Safety to see the importance safety plays in consumer purchases of cars. According to Michael Jarouche, Vice President of Global Sales and Marketing for Humanetics, a firm that manufactures crash test dummies, the industry studies and implements safety solutions along one of three areas: passive safety this refers to the safety devices within the car including the sheet metal, car structure, etc., that form the basis of the car’s crash worthiness capability. Passive safety includes the product design elements; for example, good weld nuts, good support, air bags, belts etc. The second area of safety, called “active safety includes design features such as ABS anti-lock brakes and vehicle dynamic control. Active safety has little to no relevance in the discussion of aluminum v. steel within the automotive industry, according to Jarouche. Finally, the area of information safety that includes elements such as devices to monitor the occupant and/or gauge what the driver is doing behind the wheel will not comprise any portion of the analysis on safety either. Instead we will focus our attention solely on “passive safety and the relative performance of aluminum v. steel.

The aluminum industry argument hinges on several concepts as articulated in a recent study:

  • A high strength to weight ratio
  • Larger crush zones “which serve to reduce forces on vehicle occupants in a crash
  • Aluminum structural members can collapse in a predicable manner in severe impacts
  • Better corrosion resistance “minimizes deterioration of the crash energy absorption capabilities over the life of the vehicle
  • On a pound per pound basis, aluminum absorbs 2x as much crash energy as typical automotive steel the argument goes on by stating as vehicles “lighten up aluminum will help with fuel economy, performance and safety

But as that same study points out, “There is little doubt that larger and heavier vehicles provide more safety for their occupants. And therein lies the rub until/unless more vehicles on the road contain aluminum vs. steel, the relative crash worthiness of two like vehicles, one with more aluminum, the other with more steel, will provide the steel car with a safety advantage. Thus, some industry participants have advocated a move toward vehicle to vehicle compatibility that would call on industry to move toward standardization of vehicle weights, ground clearance, bumper height and the shape of the front end. This particular issue encapsulated in an “unintended consequences argument says that knowing heavier cars already exist and make up some proportion of total cars on the road, consumers, in their own self interest, will opt for “heavier and safer car choices thereby perpetuating the problem.

In the meantime, we asked Michael Jarouche to share with us where he thinks this debate will go over the next ten years. “Steel isn’t going away at all although bumpers went from steel to plastic as well as fenders, he continued, “the main body, undercarriage and beams, those are steel made out of steel and I personally believe steel has better energy management over aluminum for these specific applications. He went on to say that steel allows for better stamping and different welding techniques that aid in the energy management process. The core structure for the most part is still steel (and that won’t change).

Next week we’ll walk through the steel industry’s arguments regarding safety as well as take a more technical look at some of the manufacturability and design issues associated with using steel and aluminum.

–Lisa Reisman

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