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  • 8/22/2019 Lighten Up Automakers Accelerate Efforts to Reduce Vehicle Weight

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    Automakers andsuppliers acc.eleratetheir efforts to reducevehicle weight b yengineering them forgreater use of lighter,stronger materials.by Lindsay Brooke and Harry Evans

    16 MARCH 2009 aei

    Weight reduction is again a prior-ity across the industry, as strict newregulations push for greater vehicleefficiency /C02 reduction in the Ll.S,and Europe. From the smallest fasten-ers to entire vehicle architectures, engi-neers are wringing excess ounces out ofnew components and systems, whilelooking for new ways to lighten up ex-isting designs.The benefits of lightweighting corre-

    late directly to greater fuel economy aswell as to improved vehicle dynamics.Studies have shown that every 10%re-duction in vehicle weight can yield 5 to8%greater fuel efficiency.Dropping 150lb (68kg) on average gives an extra mileof driving range per gallon of fuel con-sumed. In terms ofits effecton carbonemissions, reducing vehicle weight by220lb (100kg) brings a CO2 reduction ofup to 12.5g/km.Automakers have made mass reduc-

    tion part of their vehicle developmentstrategies going forward, while ensuringno sacrifices in safety or durability.Nissan, for example, has pledged toslash average vehicle curb weight by15%through 2015.Ford, as part of itscorporate goal to boost fleet fuel econo-my 40%by 2020,aims to reduce vehicleweight by 240 to 750 lb (109to 340kg),

    Honda's 2009 Insight hybrid usesAHSSandHSSfor the body structure, rather than a highproportion of light metals, in an effort to balancecost, safety, and weight. While the all-new Insight

    could be lighter, Honda isbanking on hybridpropulsion, aerodynamics, and interactive controls

    to help encourage more fuel-saving driverbehavior, rather than extreme massreduction.

    depending on the model.A daunting task for every OEMwill

    be dealing with "mass creep"-the ten-dency to make each new-generationmodel heavier than its predecessor.Mass creep is caused by adding newfeatures, safety equipment, and emis-sions-control content. Consumers alsoexpect new models to be larger andmore commodious than the ones theyreplace."Offsetting extra pounds added by

    new features definitely is a challenge,"noted Matt O'Leary, Chief Engineer onFord's 2009F-150.He said it takes greatattention to detail to achieve mass par-ity between vehicle generations.Genuine mass reductions are a toughertask, one that O'Leary's team accom-plished. The F-150base model, for ex-ample, arrived approximately 100 lb (45kg) lighter than the equivalent '08 mod-el even though it is larger and betterequipped.Last year's all-new Mercedes-Benz

    C-class sedan was that company's firstnew model that was not heavier thanits predecessor, despite growing in sizeand feature content. Ditto for the cur-rent Mazda2, which last year came in220lb (100kg) lighter than the previ-ous model.

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    4,5004,059

    ~ 4,000e~c f. . . .~ 3,500~- ed 3,000

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    Today's mass-reduction efforts likelywill not be as swift or dramatic as thosethat transformed the U.S.passenger-carfleet 30years ago. Back then, the domes-ticmakers launched bold vehicle-down-sizing programs tomeet the new CAFEregulations. Their massive shift frombody-on-frame to unibody structures,from V8engines to V6s, and from rear-wheel drive to front drive, was com-bined with smaller platforms-wheel-bases were shortened by an average 7 in(178mm).

    Thenet result was an average 1000-lb(454-kg)reduction in U.S.passenger ve-hicle curb weight, with an equally sharpjump in fuel efficiency.(Critics claimed italso compromised occupant safety.)Suppliers were incentivized to aid thecause: Inthe early 1980s,General Motorspaid back its suppliers $1for everypound trimmed from their products.

    A recent shift in the North Americanfleet mix is again precipitating a drop inaverage curb weights. Itis due to thecollapse of the full-size SUVsegment,the rise in unibody crossovers, and afalloff in non-commercial pickup sales,explained Dick Schultz, ProjectConsultant with Ducker Worldwide,which analyzes automotive materialsaei-online.org

    trends and technologies."In the past five years, we've lost a

    whole lot of real big vehicles, asAmerican consumers traded their 14-mpg, 5000-lb (2268-kg)CadillacEscalades for 24-mpg, 4000-lb (1814-kg)Buick Enclaves or even smaller cross-overs," said Schultz, a veteran metal-lurgist.

    In 2004, average U.S.market curbweights peaked at 40181b (1823kg),Schultz noted, with 42%of productionbeing body-on-frame vehicles. Theaver-age 2009U.S.market vehicle weighs3755lb (1703kg), with only 25%of theproduction mix being full frame. Theresulting average weight reduction inrecent years: about 260 lb (118kg). Andas the accompanying graph reveals, thedecline in vehicle mass is expected tocontinue through 2020.

    "Inthe next decade, wewon't see theaverage unibody vehicle getting toomuch smaller-the U.S.will pretty

    Mass ReductionSpecial Report

    Forecast

    much continue to bea C- andD-segment market although somemak-ers will bring inA- and B-classcars forspecific regions," Schultz explained.

    North America, it should benoted,offers the most opportunity for signifi-cant mass reductions due to its tradi-tiona I large-vehicle fleet mix.

    Given those assumptions, it will beup to designers, engineers, and materi-als experts to further reduce averagevehicle mass to the 3500-lb (1588-kg)average forecast for the 2020NorthAmerican fleet by Ducker Worldwide.That is a drop of about 255lb (116kg)from the '09 average.

    ae; MARCH 2009 17

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    Lighten up!

    Aluminum's successFor automakers, the path to vehiclemass reduction requires a systems strat-egy, say experts."It's a delicate balance matching theoverall vehicle weight against improvedpowertrain efficiencies, the body, andthe interior," said Matthew Zaluzec,Ford's Manager of Materials Research.The lightweighting technologies cur-

    rently in Ford's labs will apply to ve-hicles from 2012-25,he said. "We're notinventing new materials, but rather ap-plying the right materials that are costcompetitive," Zaluzec explained.The system and materials mix Ford

    has adopted for its vehicle mass-reduc-tion plan centers on using increasingpercentages of advanced high-strengthsteels (AHSS) for the body-in-white.Aluminum and magnesium will beused for closures and, depending on thevehicle program, for various structuraland chassis applications such as magne-sium radiator supports and suspensionsystems. The mixed-material strategy isfundamentally similar to those of othermajor OEMs."Lightweighting is never for free,"Zaluzec asserted. "We've done alumi-num-intensive vehicles, including the

    current Jaguar XJ8and the Ford GT su-per car. There's a major up-front invest-ment in manufacturing process," hesaid. There is also an ongoing debateabout value proposition.On the merits of its curb weight

    alone, the XJ8appears to make a strongcase for going the all-aluminum route.The 2009 base model, its body-in-whitea matrix of 5000-series-alloy stampings,castings, and extrusions, and 6000-seriesalloy exterior panels, tips the scales at3770lb (1710kg). That's 580lb (263 kg)lighter than the base Lexus LS460,a pre-dominantly steel-bodied competitorwith comparable powertrain specifica-tions. It is also the lightest sedan in itssegment.However, the Jag's 16/25 mpg U.S.EPA fuel economy rating is essentiallyidentical to the Lexus' 16/24 mpg. Inanera where even a luxury vehicle's CO2footprint increasingly ranks near the topof purchase considerations, a costly andcomplex rivet-bonded aluminum bodyshell might present a challenging busi-ness case.Not if you are Audi, however. As theindustry's volume leader in aluminum-18 MARCH 2009 aei

    12%

    ~ 4.5% 5.1%~ 3.9%

    2.0% 2.11c

    Based on 3,600Ibs. of curb weight

    10%50 Years of Uninterrupted Growth is Within Reach

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    8%

    6%4%

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    6.9%6.1%

    Honda is alreadyover 10%aluminum weightper vehicle in 2008

    -- HistoricaForeca:sr--O%+ - - - , - -~ - - -~ - - , - - - -~ -~ -~ - - -~ - _+- - -~ -~ - _,Calendar Year 1970 1975 1980 1985 1990 1995 2000 2005 2009 2010F 2015F 2020F

    I _ _ . _ Aluminum Share as Percentage of Curb Weight I

    Aluminum's value as a mass-fighter ~ll continue to grow through more closure-panelapplications, including doors,'~nd,a continued c~:lquest of chassisand powertrain' c om pon en ts . :~~ ' ","') ; '1 '~'~~i'\ (1 c 1!"'.' ', 1 ~ 1 r : . , < j N t ; i , I i j i J " i ~ , : ~ ~ ; ' f ; : !1 ! ; ' { " ' 1 i k ~ ' " u ~ ,~ ~ "

    structure vehicles since the break-through A8 in the 1980s, Audi haspushed ahead with its lightweightspaceframe technology, now used onthe TT, TT Roadster, A8, R8, andLamborghini Gallardo.The latest ASF (Audi Space Frame)architecture introduced on the 2008 TTmodels is an aluminum/steel hybridthat cuts weight by around 100 kg (220lb) compared to the previous all-steelstructure. The company estimates thereduced weight will decrease fuel con-sumption by 0.7 mpg.The construction features aluminumextrusions and castings, with a mix ofsheet-aluminum and steel exterior pan-els and closures, and steel structuralelements. The frame sections vary intype, size, and thickness depending onload, and although the side sills on theTT Coupe and Roadster are visuallysimilar aluminum extrusions, theRoadster's sill features thicker internalribbing to provide the added torsionalrigidity needed by the open-top car.There is also a steel bulkhead behindthe Roadster's seats that joins the steelsubframe that extends from the B-pillarto the rear of the car. The TT Coupe andRoadster both use steel doors with ex-truded-aluminum side-impact beams.The Roadster also employs a steel deck-lid while the Coupe uses aluminum.The remaining Class-A exterior panelsare stamped aluminum sheet.The Coupe body shell weighs 455 lb

    (206kg), of which 309lb (140 kg) is alu-minum-68% of the total by weight.High-strength steel makes up the re-maining 32%.Audi engineers claim stat-ic torsional rigidity is increased 66%compared with the previous structure.The steel content in the rear of the carsis also used to balance weight distribu-tion, for improved handling.Tojoin the dissimilar metals, Audicontinues to invest in the sophisticated,costly tools and processes to make ithappen in volume. The processes in-clude punch riveting and adhesivebonding, which eliminates galvaniccorrosion.Audi is readying the next-generation

    mixed-metals body architecture for itsMY2011A6 platform. Dubbed ASF-U, itwill offer a claimed 50% reduction inbody shell weight and 50% greaterstructural rigidity compared with thecurrent A6. Further use of steel rein-forcements with new joining processesare expected.The company is committed to apply-ing ASF-II up and down the productportfolio to increase manufacturingscale and thus lower investment costs.

    Lessons learned on the high-cost A2program will be useful in driving thetechnology down market into the A3and even smaller future models. AndASF-II applied to the large Q7 crossoverSUV potentially could save up to 660 lb(300kg).The use of aluminum sheet for clo-

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    Lighten up!

    Investigatingaluminum con rodsThe push for greater vehicle efficiencyhas advanced materials researchers ex-ploring light-metals applications in vari-ous powertrain reciprocating cornpo-nents. Forged aluminum connecting rodswere used successfully for 50 years inmass-produced British motorcycle en-gines and are popular in drag-racingcircles. Today they are under develop-ment at Peak, the supplier of aluminumcylinder liners for Honda V6 engines.

    According to Peak North AmericaPresident Bill McCall, con rods forged inPeak'sproprietary Dispal 5232 alloy offera l-Ib (O.S-kg) mass reduction perunit-6 Ib(3 kg) total in a six-cylinderengine-compared to conventional pow-der-metal steel con rods. Concerns re-garding aluminum's fatigue limit in thishigh-stress application are addressed inthe component geometries and theDispal material properties.

    McCall noted that techniques forprecision-fracturing (cracking) the bigend are being investigated. Peak proto-typed aluminum con rods for Honda'srecently canceled V8 engine program.

    L indsay Brooke

    20 MARCH 2009 ae;

    sure panels continues to grow.According to The AluminumAssociation, the number of closure pro-grams globally has risen from 231 in2006to 263programs in 2009,a 14%gain. Hoods and decklids offer a 40 to50%weight savings over the compa-rable steel part-and being large panelsthey are logical targets for cuttingweight.In 2009, a record 22.3%of vehicle

    production will have an aluminumhood. "Every year, aluminum gainsabout one market-share point in hoods,"noted Schultz. "We think that applica-tion will be 35%by 2020.""Approximately half of Ford vehicles

    already have aluminum hoods andmore are on the way," commentedZaluzec. "Now we're doing R&Donaluminum doors-a traditional steelapplication," he revealed. "I won't saywhen we're going to put them into pro-duction, but they're part of our overallweight-reduction strategy."As a percentage of average vehicle

    curb weight, aluminum reaches an all-time high at 8.7%in 2009-about 326 Ib(148kg) of all product forms per NorthAmerican light vehicle. Steady growthis expected in suspension and drivelinecomponents, along with a final assaulton the remaining 25%of engine cylinderblocks still in cast iron. Experts expectaluminum's percentage of average curbweight to exceed 10%in 2020."Powertrain improvements alonewill not be enough to get automakers to

    the necessary fuel economy improve-ments that are going to be expected,"said Buddy Stemple, Chairman ofTheAluminum Association's Auto andLight Truck Group. "With the currentstate of the industry, aluminum will besignificant in key automotive decisionsconcerning fuel economy and mass re-duction overall."ToStemple's point, Toyota will

    launch the first production aluminum-based wiring harness, on its MY2011Yaris subcompact. The harness, to besupplied by Sumitomo ElectricIndustries, will be nearly 40%lighterthan conventional copper wire and isexpected to be less expensive. That is apotential boon toB-segment and smallervehicles that inherently are not ladenwith excess mass. However, it comeswith a compromise--the aluminum har-ness also will be up to 25%larger in di-ameter than a copper-based harness.

    AHSS hitsprime timeCharging fast and furiously into thebody structure arena are AHSS, includ-ing martensitic, boron, and dual-phasematerials. And they get materials guruslike Ford's Zaluzec plenty excited overtheir potential."We're talking 500MPa and above in

    tensile strength for some of them,"Zaluzec exclaimed. "AHSS allows us t

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    te favorably with aluminum from thendpoint of cost and weight savings.and Bepillars. door beams, those kindparts which essentially look like alu-num extrusions. Their geometriesd to work well with those advancedAHSS generally are not expected to bejor candidate for closures or largey parts in the future, the experts reck-

    . Even the 980-grade dual-phase steelsnot offer the mass savings of alumi-for closure applications.

    "The fundamental rule is even theseanced steels are going to cost lessn the equivalent aluminum part-only in rare exceptions can they savemuch weight. So engineers balance itout," Schultz observed.The most AHSS-intensive vehicle for2009 in terms of body content isW's X6. The D-segment crossovers 32%AHSS in its body-in-white andures, according to the Duckerldwide study. The Altima is also atAHSS, but the larger X6containsre pounds of the steels.Lincoln's 2010MKT large crossovery structure contains about 16%

    Itis one of Ford's leading ve-es in terms of lightweight materialstent and the company's highest inth America."The 16% doesn't seem like muchpared with the X6's 32%, but Ford'sde a lot of progress in a very short," Schultz opined. The F-150 alsotains 16%AHSS, high content for ay-on-frame vehicle."We consider BMW and Honda to be'poster children' for production ap-ation of advanced high-strength ma-als," Schultz said. "Both companiesthe most amount of AHSS and alu-num per vehicle." He reasoned thattwo automakers cannot be labeled asg in anyone materials camp."If you're pushing the materials-nology envelope, you're using alu-num; you're using high-strength mar-itic, boron, or dual-phase steels; and're using magnesium. In my view,W and Honda are probably 10 yearsad of some of the other OEMs in this," he noted.Honda's 2010 Insight hybrid sedan iser and weighs more than its alumi--intensive predecessor introduced1999. The company opted for a vari-of AHSS and HSS grades to meety structure, occupant safety, and

    Mass Reduction -Special Report l1li

    cost targets. A main bogey was to keepdevelopment costs down so the Insightwould be one of the most affordablehybrids on the market."We're using high-strength steelmore than any other tool in our holster,"a company insider told AEr.Ron Krupitzer, Vice President of

    Automotive Applications at AlSI, com-mented that "Honda is more value-ori-ented, and on a mass-vs.-power rating,Honda is good. Itcomes down to priori-ties, and Honda has stuck to steel."Keeping hybrid and electric vehicle(EV) curb weight to a reasonable level is

    a delicate balance, engineers note. Theadded weight of the electric drivetrainand batteries means both vehicle massand cost are critical. Itis worth notingthat Toyota's new-generation Prius, andthe Chevrolet Volt being readied for late2010 production, use primarily steelbody structures. Niche and premium-market entries, such as Tesla's EV road-ster and Fisker Automotive's plug-inhybrid sports sedan, are engineeredwith relatively high aluminum content.To meet the anticipated growing de-mand for AHSS, the steel industry isworking on adding manufacturing ca-pacity. But the key to optimizing theexcellent characteristics of AHSS (andunlocking more vehicle applications) islearning how to use them."We don't need many more new

    steels," noted Zaluzec. "What we needinstead are further engineering work informing and joining, and recovery on thecurrent parts." He and other experts noteAHSS has different springback character-istics, making it a challenge to form com-plex geometries consistently.Schultz echoed Zaluzec: "What theauto industry needs is to perfect ways

    to weld the dual-phase, and to form themartensite and the boron, and predictthe tooling so we don't have to have dietryouts for two months on every part,"he said.As an example, Benteler and Magnalearned how to make boron beams

    without excessive scrap using the hotstamping process. This has sparkedhuge interest in boron beam applica-tions at the OEMs. Volkswagen hasswitched 100% of its bumper beams toboronAHSS."The [beams] resemble toothpickscompared with the old beams they'rereplacing," Schultz noted. "They onlyweigh 7 or 81b; they have 1400MPa ten-sile strength. Fantastic. The suppliers'mastering of the hot-forming processmade a big difference," he said. (As acounterpoint, Honda recently switchedits Civic bumper beams to aluminum.)In their drive to optimize vehicle

    mass and structural integrity, engineersare using pia-mimetic topology model-ing tools in their body development ac-tivities. These tools help identify whichbody-in-white zones have the higheststrain and help determine critical-loadpaths on the vehicle.Chrysler'S Knowledge-BasedEngineering group, in collaborationwith MBtech, Mercedes' ResearchGroup, and AISI, created a proprietaryprocess with the so-called "bionic" toolsthat allows engineers to accelerate theuse of AHSS in new bodies-in-white.

    "Itallows you to peel away weightwhere you don't need it," BillGrabowski, Director of Body CoreEngineering, told AEr. He predicts asmuch as 120lb (54 kg) could be shedfrom the body-in-white through bio-mimetic topology.

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    Lighten up!

    Shuffling the DECSwith a lightweight seatSeating giant Lear is readying a new seating systemfor 2010 productionthat will offer significantly lower mass per seat set, aswell asgreater com-fort and lower environmental impact. This illustration isthe first publicview of the Dynamic Environmental Comfort Seat, known asDECS.

    According to Ash Galbreath, Director of Advanced Materials,DECS' radical design features a three-layer sandwich of variousfoam materials to perform structural, comfort, and tactile tasks.The bottom layer attached to the lightweight hydroformed seatframe ismolded in semi-structural expanded polypropylene(EPP)foam. EPPcan be produced in a range of hardnesses,allowing Lear to replace the traditional stamped steel anti-submarining pan, heavy wire mesh, and various metalbrackets and clips.

    DECS'middle layer is in Lear'ssoy-oil-en-hanced BioFoam; it provides occupant com-fort and support in combination with thetop layer of polyester foam. DECS'multi-material construction is fully recyclable, andits foam structure weighs approximately halfthat of conventional seat-cushion sets.

    Competitors J CI,Magna, and Faurec ia alsoare developing lightweight seating solutions.

    L indsay Brooke

    Chrysler vehicles currently employapproximately 20-30%HSS. Grabowskiindicated that total will rise to 60% by2012, with AHSS content of up to 30% inbody shells expected to arrive by 2010.New apps formagnesium, plasticsThe liftgate inner panel in Lincoln's 2010MKT crossover, along with the front ra-diator apertures in the MKT and '09F-150,signal Ford's intention to increaseits deployment ofmagnesium alloysacross its vehicle lines moving forward.Other makers are following similarpaths. With high specific strength andthe lowest density among all structuralalloys, magnesium offers big potential instructural applications where systemsmass reduction is critical. And magne-sium's traditional price premium is be-ing offset by stringent fuel-efficiencystandards in many global regions.On the MKT, the cast-magnesiumliftgate inner panel is combined withan aluminum outer. The mag part wasspecified to help keep the primarilysteel-bodied vehicle within its weight-class target. According to MKT ChiefEngineer Ron Heiser, it saves morethan 20 lb (9 kg) compared with astamped steel panel. It is supplied byMeridian Magnesium Products and is22 MARCH 2009 aei

    claimed to be one of the largest singlemagnesium parts currently in automo-tive production.Meridian also supplies GM with the

    industry-first magnesium front cradleintroduced on the 2007Corvette. Die castin AE44 alloy,it provides a 35%mass sav-ings over the previous aluminum cradle.GM engineering management is pleasedwith the results and is currently conduct-ing a demonstration program for magne-sium use in other load-bearing areas.A major driver for the increased use

    of magnesium alloys in automotive ap-plications has been refinements in alloyprocessing and composition, with newapproaches to component design. Anewcomer attracting the auto industry'sattention is T-Mag Casting Technology.The Adelaide, Australia-based companyis demonstrating a patented permanent-mold magnesium casting machine thatintegrates melting and casting opera-tions into a single manufacturing cell.According to Fred Nader, Director of

    u.s. Operations for Team AustraliaAutomotive, representing T-Mag, theprocess is capable of handling small tomedium sized components in complexgeometries including sports-type roadwheels and engine cylinder blocks. Cycletimes are faster than using comparablealuminum gravity-cast permanent moldprocesses, Nader said. "And the equip-

    ment produces to near-net shape forminimized machining-there'S less than5%process scrap," he noted.T-Mag is collaborating in the United

    States Council for Automotive Research(USCAR) High Integrity MagnesiumAutomotive Castings (HIMAC) researchproject to develop new permanent-moldprocess technologies using a lower con-trol arm as its initial proof-of-conceptpart.While it may appear that most of themajor gains in lightweighting are ex-pected to come from the metals indus-try, that is clearly not the case. Plasticsand composites suppliers have turnedup their R&D, and the results of theirefforts are omnipresent in 2009-10 ve-hicles. The average vehicle containsmore than 330 lb (150kg) of plastic, andeach pound of it supplants 2-31b (up to1.4 kg) of primarily metals.[For a recent review of innovative,

    mass-reducing plastics engineering onnew vehicle components and systems,please see "Prize-winning plastics,"December 2008AEI, p.22.]Another area receiving much focus isnew solutions for NVH attenuation with-

    in the vehicle structure. Jim Federico,Global Vehicle Line Executive for GM'smidsize cars, notes the new lightweightacoustic damping mats being deployedacross GM's global product portfolio.The mats, known as liquid-appliedsound deadener (LASD), were pioneeredon the T900 truck program."The savings is in multiple poundsper vehicle," Federico told AEI. "We'recurrently migrating this technology tofloorpans and bulkheads" of GM's newGlobal Epsilon, Lambda, and Theta-based products, with future applicationsto come, he said.From an overall vehicle standpoint,the addition of 300 lb (136kg) of ad-

    vanced and ultra high-strength flat rolledsteels, and 50 lb (23 kg) of aluminum inall product forms-plus increased use ofstructural plastics and magnesium-willbe needed to help the OEMs drive curbweight down another 250 lb (113kg) by2020."It's imperative that materials suppli-ers stay the course in terms of promoting

    and technically supporting material sub-stitution during these difficult times forthe OEMs and their suppliers," Schultzof Ducker Worldwide intoned. "If theeffort is not sustained, the goals outlinedabove will not be achieved." aei

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