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Steel the One: Aluminum and Plastics

Fifteen years ago, most of us would have scoffed at the idea of amass-produced, all-aluminum auto, such as the Acura NSX, or a production automobile with exterior plastic panels, such as the Saturn.

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That was then and this is now. The use of
aluminum and plastics has increased dramatically during the last
10 years, and their use is common in the manufacture of today’s
vehicles.

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But what about steel? Is it still the material
of choice by automotive engineers? Does steel have a future role
in automobile manufacturing? If so, what are the steel companies
doing to ensure the future of steel in modern automobiles?

To answer these questions, let’s do a little
role playing. Imagine that you’re a steel-company CEO. You just
ended an eye-opening phone conversation with a fellow steel-company
CEO, and you both realized that aluminum and plastic have gained
– and will continue to gain – market share. "What are we
going to do?" is the question on both of your minds. Do you
wait until there’s a major breakthrough in the use of plastic
or aluminum, which will further erode steel’s marketshare, or
do you dedicate yourself to the goal of enhancing steel’s position
as the premier material for modern automobiles?

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If you choose the latter, how will you accomplish
it?

A consortium of 32 steel companies from 15
countries decided to accomplish it this way: Any steel company
that wanted to participate could join a cooperative venture to
research a "new" steel body design. This consortium
will invest more than $20 million to develop a competitive ultralight-steel
auto body (ULSAB).

The advantages of this joint venture are obvious.
A number of companies with similar interests can pool their financial
resources to tackle a specific problem or investigate the feasibility
of a new concept, and the information is then shared by all participants,
who then decide how their individual companies will apply the
gathered information.

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One of the target goals of this consortium
is to use existing manufacturing technologies and steels. Cutting-edge
manufacturing technologies include: hydroforming, tailored blanking,
weld bonding and laser welding. Steels will include high-strength,
dual-phase and bake-hardened, which are all common to new vehicles.

Another goal of the consortium: The use of
sophisticated manufacturing technologies and steels must not override
the need to meet fuel-economy standards, affordability, safety,
recyclability and durability (keep in mind that most previous
attempts at a lighter-weight, unibody vehicle have increased the
cost of manufacturing).

Phase I and Phase II

Phase I of the ULSAB project, which began
in 1994, is the engineering study. The study is being conducted
by Porsche Engineering Services in the United States, and its
first step was to define the type of vehicle for the study. The
midsize, unibody sedan was chosen, and the benchmark vehicles
include the Acura Legend, BMW 5 Series, Chevrolet Lumina, Ford
Taurus, Honda Accord, Lexus LS400, Mazda 929, Mercedes 190E and
Toyota Cressida. Wheelbase, interior volume and rigidity of these
vehicles became the targets for the ULSAB study.

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The specific goals for Phase I were to create
a conceptual light-weight car structure that:

  • achieves a truly significant weight reduction compared to
    reference vehicles,

  • meets all functional and structural performance targets, and
  • provides concepts in design, analysis, materials and manufacturing
    that are applicable to future vehicle programs.

The ULSAB project also boasts a design that will accommodate a
wide range of exterior-design treatments, which would be a major
breakthrough in the way car companies do business. Imagine five
or six midsize vehicles that all use the same platform – with
only a few aesthetic differences.

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Other manufacturing targets include a reduced number of parts,
and fewer welds and joints. The new structure promises to reduce
the weight of the typical midsize, unibody vehicle by 35 percent
and to improve torsional rigidity by more than 100 percent.

So far, the design work has been performed with the aid of computers.
The design team created a "shell" model, and with the
magic of computers, manipulated the shape of cross sections, increased
or decreased material thickness, redesigned joints and refined
structural details.

The computer-generated model was also fitted with a bumper system,
suspensions, fuel tank, doors and power train. The model was then
subjected to crash simulations – front, rear, side-impact and
roof-crush.

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Some of the innovative parts of the concept engineering include:

  • a front rail that attaches directly to the rocker. This concept
    improves torsional and bending rigidity and optimizes crash performance
    while reducing material thickness of other parts.

  • a hydroformed side roof rail. This provides a stronger connection
    from the A, B and C pillars to the rear shock tower, which produces
    a good load path from front to rear and helps eliminate the need
    for rocker reinforcements.

  • a redesigned hinge-pillar area. The cowl pierces and attaches
    to the A-pillar outer, significantly improving hinge-pillar cowl-joint
    performance.

  • a front shock tower that’s integrated into the skirt, which
    is laser welded to the fender-support rail. The wheelhouse is
    spot welded to the front-rail upper-welding flange and to the
    front rail’s lower flange in the shock-tower area.
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  • a rear shock tower that’s integrated into the rear rail. To
    improve the rigidity of the ULSAB, the body-side inner assembly
    is weld bonded to the body-side outer assembly.

    All these changes to how major components connect are in the concept
    phase – it’ll be interesting to see if these innovative design
    changes can be finalized in both the prototypes and the production
    versions.

    Progress update: As of Oct. 1, 1996, the exterior-styling concept
    (Phase II) was announced for the ULSAB project and will continue
    into early 1998, when demonstration models should be ready. Porsche
    Engineering Services will continue to oversee the project and
    supervise the "bodies in white."

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    Impact on Collision Repair

    While it’s important to understand that the ULSAB project is still
    in its infancy, it’s also vital that we start predicting its impact
    on collision repair:

    1. It’s likely that steel will continue to be the material of
      choice by automotive engineers.

    2. The use and application of high-strength steel will be an
      important part of the ULSAB project – two-thirds of the ULSAB
      is projected to be modern, high-strength steels.

    3. If car companies use five or six midsize vehicles with many
      of the same main structural components, collision repair would
      get a bit easier – using the same vehicle platform would facilitate
      everything from vehicle estimating to repairing the vehicle. On
      the downside, when a totally new vehicle platform goes into full
      production, it takes a while to see how it will actually perform
      in real-life collisions. And with the innovative joints used in
      this platform, there will be a learning curve for reparability.

    New manufacturing technologies being utilized in the ULSAB project
    – and on current vehicle models – will also impact how vehicles
    are repaired.

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    Take hydroforming, for example. The box structure is a basic component
    of many unibody vehicles, but the disadvantage here is that these
    structures are made from a number of individual parts with flanges
    that require welding to join them together. With hydroforming,
    you take a tube and form it into a complex shape, thus eliminating
    multiple parts and welding – and simplifying the manufacturing
    process.

    How does hydroforming work? The process begins with a straight-welded
    round tube, which is bent into a configuration similar to the
    final part by a computerized, numerically controlled bender. The
    bent tube is placed into a forming die, filled with fluid and
    then pressurized. Under pressure, the round tube is forced into
    the shape of the die.

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    The Reality

    With the current available information, it’s difficult to predict
    when the ULSAB project will become reality. What is important,
    though, is that you occasionally review every component of what
    you do – from estimating to straightening, from sectioning to
    welding – for every vehicle you repair.

    One day soon, the ULSAB project is likely to impact how you repair
    vehicles. Be prepared. Staying current and contemplating future
    automotive designs is just as important as opening your shop door
    every morning.

    Fred Kjeld is a contributing editor to BodyShop Business.

    A Spinoff Project

    A spinoff of the ULSAB project is a new design study initiated
    by the North American steel industry to explore steel’s potential
    to reduce the weight and cost of light-duty trucks and sport-utility
    vehicles. Just like the ULSAB project, this study takes a holistic
    design approach to manufacturing a competitive light truck. Basic
    architecture, materials, efficient manufacturing methods, simplified
    assembly and vehicle reparability are all goals of the project.

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    In Production Now …

    As we contemplate the ramifications of the ULSAB project, we can’t
    forget what’s currently in production. If the new Dodge Stratus
    and Chrysler Cirrus are any indication, the application of high-strength
    steel is still in the automotive engineer’s "bag of tricks."

    When introduced, these two vehicles exemplified the greatest use
    of underbody high-strength steel of any production vehicle. Another
    emerging technology also was used to manufacture the front rails:
    tailored blanks. For this process, the left and right engine rails
    are fabricated from two different thicknesses of high-strength
    low-alloy steel, laser welded at the seam and then formed. One
    piece is 1 mm thick, and the other piece is 2 mm thick. Both pieces
    are galvannealed steel.

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