6Concept To Reality Spring 2002

Advanced high-strength

steels (AHSS) have emergedas one of the most

sophisticated

materials available forhighly engineered productdesign.

New LightSteel in aSeeing

By Ron Krupitzer, American Iron and Steel InstituteTed Diewald, Automotive Steel Partnership

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7Concept To Reality Spring 2002

T R E N D S I N T E C H N O L O G Y

OOver the past 20 years, steel – and the North American industry that produces it – hasevolved to a sophisticated level. Today’s steel features improvements in quality anduniformity, and is more versatile than ever before. In addition, steelmakers have investedbillions of dollars to update their equipment as well as to streamline and automate theirprocesses.

Along with this transformation there has been a significant penetration of steel into newmarkets, such as homebuilding, roofing and electrical distribution (utility pole market). Italso has enabled steel to become a more effective product in traditional markets, such asconstruction and automotive.

A Better GradeThe new steel comprises many high-tech products that were not available 25 years ago.

Today’s new steels are stronger, more durable and more formable than ever before, allowingmanufacturers great versatility in applying the new steels to many products. They allow

lighter-weight, more-efficient structures to be built.For example, the new advanced high-strength steels (AHSS) have

emerged as some of the most sophisticated materials available forautomotive production. These advanced materials gain their high-performance properties in strength and formability by incorporatingmultiphase microstructures, which result from precise control ofchemistry and thermal treatment.

The high strength and formability of AHSS work synergistically tooffer vehicle designers more freedom in how they addresscrashworthiness, packaging, styling and mass reduction. UsingAHSS, designers can create safe, affordable, fuel-efficient andenvironmentally responsible automobiles for the general public.

In 1978, steel comprised 59% of a vehicle. Today, it makes up54% of the mass of the vehicle, and high-strength steel is the fastest-

growing lightweight material in automotive design. In years to come, as automakerscontinue to apply advanced high-strength steels, steel will remain the material of choice.

Showcase for AHSSThe newest conceptual vehicle design initiative by the steel industry – the ULSAB-

AVC, for UltraLight Steel Auto Body-Advanced Vehicle Concepts – demonstrates theinnovative use of AHSS in automotive design. The study features two concepts, a 2-doorhatchback for the European market and a 4-door, mid-size sedan for North America – onethat meets the goals of the Partnership for a New Generation of Vehicles. The objectives ofthe ULSAB-AVC program are as follows:

• Anticipated crash safety requirements for 2004• Improved fuel efficiency• Optimized environmental performance• High-volume manufacturability

The UltraLight Steel Auto Body-Advanced Vehicle Concept (ULSAB-AVC)(above) is a virtual car that demonstratesthe innovative use of advanced high-strength steels (AHSS) in automotiveapplications. (Upper left) Tailored blanks,tailored tubes, hydroforming and relatedjoining technologies permit partintegration for a significantly reducedpart count. Thanks to steel, only 81 majorparts are required to build the ULSAB-AVC body structure.

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Final results show that the ULSAB-AVC concepts havethe potential for achieving five-star safety ratings (asadministered by the National Highway TransportationSafety Administration). In addition, fuel consumption forthe North American concept would be 52 to 73 mpg; themanufacturing costs would be $9,200 to $10,200.

The study is a result of collaborative efforts by 35 steelcompanies from around the world. The North American

Steel Company members of the consortium are alsomembers of the Automotive Applications Committee,American Iron and Steel Institute.

In addition to the highly efficient body structure, whichcontains only 81 major parts, the ULSAB-AVC has otherdesign advances, including an innovative front-endmodule, a highly economical powertrain and efficient frontand rear suspension systems. All are aimed at balancing fuelefficiency, environmental performance and safety whilefostering low-cost assembly and ease of servicing.

Advanced high-strength steels make up more than 80%of the ULSAB-AVC body structures while other grades ofhigh-strength steel account for the remaining 20%. Inaddition to the use of advanced, high-tech steels in thebody structures, the concept vehicles feature a range ofsteel grades in other applications including the frontsuspension, wheels, instrument panel beam, fuel tank, seatframes, bumper beams and closures.

ULSAB-AVC includes design and material conceptsfrom consortium research projects on closures andsuspensions. Successful integration of these concepts into acomplete vehicle system confirms the mass-reducing andperformance-enhancing potential of steel.

Five-Star ResultsComputer-simulation tests predict that the ULSAB-

AVC designs would receive “Five Stars” in the U.S.

A SteelResolve

AltairEngineeringutilizes OptiStructin a three-stepprocess for theLightweight SUVFrame Project –defining availabledesign space(top), performingtopologyoptimization(middle) anddeveloping apreliminarydesign concept(bottom).

The Auto/Steel Partnership (A/SP) wasformed in the mid-1980s as the automotiveindustry worked to increase the quality of itsproducts, virtually all of which are made ofsteel. Today, current partners – Daimler-Chrysler, Ford, General Motors, BethlehemSteel Corp., Dofasco Inc., Ispat Inland Inc.,National Steel Corp., Rouge Steel Companyand United States Steel Corp. – are dedi-cated to advancing the application of steel inautomotive.

The partnership provides the venue for in-creased precompetitive cooperative activi-ties. Its vision includes ensuring that steel isthe “competitive material of choice” in achanging automotive market; ensuring thesuccess of member companies by using

inter-company and interindustry cooperativeprograms; and proactively resolving govern-mental regulatory agency requirements andcustomer needs.

Over the years, the partners have under-taken 35 initiatives. Sixteen project teamsare currently in place. Of the 16, three arecharacterized as “focus” projects, eight as“enabler” projects and five as industry “sup-port” projects.

The focus projects were undertaken threeyears ago to evaluate new and proposed ma-terials; to develop application methodologies;and to expedite a 25% mass reduction inLightweight Body Structure, Lightweight Clo-sure Panels and Lightweight Sport Utility Ve-hicle (SUV) Frames. The eight enabler proj-ects address engineering, material propertyand manufacturing process issues that mustbe resolved to allow the lightweighting proj-ects to achieve their stated objectives.

Through a contract awarded by the U.S.Department of Energy, Altair Engineering is

collaborating with the A/SP on the Light-weight SUV Frame Project. Altair will applystate-of-the-art concept design and analyticalmethods, along with advanced manufacturingprocesses and materials, to an existing high-volume frame to achieve an advanced light-weight design that can be adapted to othercommercial SUV platforms. The results ofthe study will demonstrate the lightweight de-sign methodology in a format that can beused by frame designers in OEMs throughoutthe U.S. to improve their designs and to re-duce the weight of the frame system.

What’s more, a rigorous review of ad-vanced manufacturing and materials tech-nologies will be applied to the newly createdarchitecture to develop the most cost- andweight-effective design approach for theframe subsystems. After these are imple-mented into the frame concept, optimizationsoftware will be applied to minimize theweight and to maximize the performance ofthe frame.

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New Car Assessment Program (NCAP) and Side-Impact NCAP crash safety tests, the highest possiblerating in the United States. In addition, the conceptcars would receive the top rating for performanceagainst standards of the Insurance Institute forHighway Safety – as well as receive the equivalent to aFive-Star rating in European NCAP tests.

ULSAB-AVC consortium steel experts provideddynamic strain-rate sensitivity data, which engineersused in their computer crash models. Compared to useof data for static properties, whose application hasbeen standard practice for years, use of dynamic dataprovides more accurate prediction of vehicle crashperformance. Plus, use of such data provided furtheropportunities for engineers to optimize the structuralefficiency of the body design.

ULSAB-AVC engineers, in computer modelingcrash tests, subjected the designs to higher speeds

and/or more severe loads than current standards inseven simulated crash events. They evaluated bodystructure behavior during the tests using such typicalmetrics as the crash pulse at the B pillar and intrusioninto the safety cage. Results validated the capability ofsteel to maintain its position as the material of choicefor safe vehicles. The ULSAB-AVC studyalso demonstrates that the concepts wouldcost no more to build than comparablevehicles.

Virtual SimulationThe application of high-power

computers and sophisticatedsoftware, especially inautomotive, minimizes the needfor engineers to buildhardware prototypes toperform structural analysesand crash tests. In the2002 ULSAB-AVC study,for example, engineers worked withvirtual vehicles, and the results proved to bereadily acceptable to the automotive industry.

Thanks to advancements in software technology,engineers are able to evaluate structural performance in3D, stereoscopic view. In crash analyses, they can see thestructures collapsing under different load conditions. Theresults compute acceleration and other parameterswithout having to build and run a full-size operatingvehicle into the wall.

We see several trends emerging with the new steel.First, with the use of advanced high-strength materials,industry will use less mild steel, resulting in a significantreduction in natural resources and power. Second,industries will use more value-added steel, such as thehigh-strength and advanced high-strength steels. Many ofthese products will be custom-tailored to specificapplications. Third, the material and methods developedin business segments where steel has traditionallyflourished, such as construction and the auto markets, willfind roots in other markets as well. The variouscommittees of American Iron and Steel Institute arecommitted to this further development of steel.

Ron Krupitzer is Senior Director Automotive Applicationsof the American Iron and Steel Institute. Ted Diewald isExecutive Director of the Auto/Steel Partnership.

T R E N D S I N T E C H N O L O G Y

Modernizingthe Industry

Over the past 20 years, the steel industry inNorth America has become the most modern andthe most efficient of any steel industry in the worldtoday. During the past 25 years, North Americansteelmakers have spent $60 billion ($35 billionsince 1995) in modernization.

The industry has retired the old, cumbersomeand inefficient ingot-casting practices, replacingthem with highly technical, computer-controlledcontinuous casters, which are totally enclosedsystems capable of creating semifinished steelproducts in one continuous process. Also, newcomputer-controlled gage and shape controlsystems for rolling and ultramodern continuousannealing and galvanizing lines are now in place.

Together, these investments have led toimprovements in quality and uniformity. Thismodernization effort by steel resulted in the triplingof labor productivity and the elimination of 60million tons of obsolete capacity, far more than theEuropean Union and Japan combined.

Computersimulation crashmodeling showsthat the ULSAB-AVC (Partnershipfor a NewGenerationVehicle-Class)could achieve aFive-Star SafetyRating. The use ofdynamic propertiesfor modelingenhances thesimulationcrashworthinesspredictioncapabilities.

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