(748111576) Keynote Paper F 2003 Lightweight Forming

8/18/2019 (748111576) Keynote Paper F 2003 Lightweight Forming

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M an uf a ctur ing o f Lightweight Co ponents b!Metal "oring

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2/23

Manufacturing of Lightweight Components by Metal Forming

M. Kleiner 1

(2), M. Geiger 2

(1), A. Klaus1

1Chair of Forming Technology, Dortmun !ni"ersity, Germany

2Chair of Manufacturing Technology, !ni"ersity #rlangen$%urem&erg, Germany

A&stractDue to constantly increasing ecological concerns an emans for higher 'erformance, lighteight construc$tion is a ey factor to success mainly in the trans'ortation sector &ut also in general engineering, machine$tools, an architecture. This 'a'er eals ith current an future contri&utions of forming technology to themanufacture of lighteight com'onents an structures. As esign, materials, an manufacturing 'rocessesha"e to &e consiere integrati"ely, it is 'ointe out hich issues arise in the 'rouction of loa aa'te e$signs an using high strength materials. Frame an shell structure conce'ts as ell as their relate forming'rocesses are 'resente. Finally, fiels of further research are ientifie.

Keyors*

Metal forming, material 'ro'erty, lighteight construction

1 INTRODCTION

+n moern trans'ortation engineering, the a''lication of lighteight com'onents is a central challenge. Due toeconomical an ecological reasons as ell as to im'ro"e'rouct 'ro'erties, a mass reuction is necessary. Thisin"ol"es a''roaches from ifferent engineering isci$'lines. Therefore, lighteight construction can &e efineas an integrati"e construction techni-ue using all a"ail$a&le means from the fiel of esign, material science,

an manufacturing in a com&ine ay to reuce themass of a hole structure an its single elements hile atthe same time the functional -uality is increase.

/ighteight construction is crucial here mass is criticalto ena&le the 'rouct function lie in aeronauticala''lications. +n case of masses su&0ect to acceleration,lighteight com'onents can increase the 'rouct'erformance e.g. allo higher re"olutions ith lighter cranshafts. Dri"ing comfort an safety can &e increasehen uns'rung masses are reuce lie in a car chassis.

At least, reucing masses im'ro"es the fuel con$sum'tion. (Figure 1)

Much effort is &eing 'ut into the e"elo'ment of light$

euce fuel consum'tion +ncrease comfort

eight com'onents an structures in automoti"e a''lica$tions. Firstly, lighteight construction eals ith the useof light materials. For eam'le, the tailgate of the 3ols$agen /u'o consists of a magnesium cast inner 'art ithan aluminum outer 'anel although se"ere corrosion is$sues ha"e to &e consiere 415. DaimlerChrysler uses amaintenance$free ceramic isc &rae system in thes'orts car 6/ thus eliminating 27g of uns'rung masshich significantly increases 'rouct costs 425.

6econly, lighteight construction eals ith ifferentesign strategies. For eam'le, the !/6A6 stuy eam$ine chassis esign 'ossi&ilities 'ro"iing ifferent le"elsof sus'ension comfort, costs an eight 485 (Ta&le 1).Concerning the &oy structure of trains or cars, framean shell structures can &e ifferentiate. 9oth esignstrategies are commonly line to a s'ecific material*aluminum in the case of frame structures 4:5, steel in thecase of shell structures 4;5. Therefore, ifferent manufac$turing emans arise using ifferent esign strategies 45Mass

sa"ing 4>5Unsprung mass Tist&eam < 82

#na&le function +ncrease 'erformance 6trut ? lins 2 2;

Dou&le ish&one 7 1@

Multi$lin 87 8("s. aluminum &enchmar)

/otus uni-ue 22 8:Critical mass Masses subject ("s. ou&le ish&one)

to acceleration

Figure 1* ur'ose of lighteight com'onents.Ta&le 1* Cost an mass sa"ings ith

ifferent sus'ension esigns 485.


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Figure 2* /ighteight heels mae ofaluminum, steel, an magnesium (from left toright) 4@, B5.

Rm

> 93 .8 11.2 :.: @.@

Con"entionally, to$'iece steel heels are manufacture&y ee' raing of the is, 'rofile rolling of the rim, an

3 E > 94 1:.@ 27.: @.< 17.<

a su&se-uent &olting or eling o'eration to 0oin &oth'arts. This heel ty'e co"ers less than half of the marettoay. Customers eman heels ith a larger iameter an tires ith a smaller cross section. Therefore, heels&ecome hea"ier thus aggra"ating the a&o"e mentione'ro&lems 45. The further e"elo'ment of forming tech$nology ena&les the o'timie manufacture of lighter heels mae of aluminum, magnesium, or e"en steel(Figure 2).

As a technology for large$scale 'rouction es'ecially for automoti"e a''lications, metal forming 'ro"ies eminent'ossi&ilities for the cost effecti"e manufacture of light$eight com'onents. A"antages lie or harening anloa a0uste material orientation offer aitional 'oten$tial for lighteight constructions.

This 'a'er focuses on the interrelations &eteen light$eight construction an metal forming. =hat are therelate challenges to manufacturing 'rocesses an hichcontri&utions can &e gi"enE

/ooing at material s'ecific issues of metal forming,common 'ro&lems, an res'ecti"e manufacturing 'roc$esses in section 2, the use of steel an aluminum as ellas the recent use of magnesium for lighteight com'o$nents are iscusse. 6ection 8 eals ith lighteightstructures an the manufacture of their 'articular or$'ieces. Frame an shell structures are iscusse ini$"iually, folloe &y as'ects of 0oining &y forming. Finally,the fiel of further research is ientifie (section :).

! FORMIN" OF LI"#T$%I"#T M&T%RI&L'

+n a material &ase a''roach to the manufacture of lighteight com'onents, the use of light metals ee'ingthe same or'iece geometry reuces the com'o$nents eight. Although the ensity of aluminum is a thirthat of steel, aluminum has only a thir of the strengthan tensile moulus. As the use of light metals must notecrease 'rouct 'ro'erties, specific material 'ro'ertiesshoul &e taen into account (Ta&le 2).

The tensile moulus is metal e'enent an cannot &echange &y alloys or graes. An increase in s'ecificstiffness as neee e.g. for structural automoti"e a''lica$tions can therefore only &e achie"e &y larger hollo

> Density 4g m$8

5, E Tensile moulus 4Ga5,R m Tensile strength 4% mm

$25

(1)6'ecific strength 417

<% mm g

$15

(2)6'ecific stiffness 417

% mm g

$15

(8)Dent resistance 417

<%

12mm

2g

$15

(:)6hell stiffness 417

@%

18mm

@8g

$15

Ta&le 2* Material 'ro'erties.

!nfortunately, a 'rogress in alloy e"elo'ment in termsof higher strength alays results in loer nominal strainat fracture thus limiting their forma&ility 4115*

? steel* strength increases from 2;7 Ma u' to1777 Ma &ut strain ecreases from :;> on to12>H

? aluminum* strength from 1;7 Ma u' to ;87 Ma &ut

strain from 87> on to 17>H? magnesium* strength from 277 Ma u' to 8B7 Ma &ut

strain from 27> on to @>.

As a conse-uence, high strength alloys necessitatehigher forces in forming o'erations as ell as more rigi'resses an more ear resistant tools. The latter can &eachie"e &y ceramic inserts for forging 412, 185 or ee'raing o'erations 41:5, for eam'le.

At the same time, the lo uctil ity restrains esign 'ossi$&ilities. +n orer to o&tain lighteight com'onents, thematerial istri&ution is crucial. The material use shoul&e istri&ute ieally accoring to the loa a''lie to thecom'onent. ecent e"elo'ments em'loy more anmore to'ological o'timiation using &ionic methos 41;5.

+n an iterati"e esign 'rocess, material is ae to acom'onent here re-uire ue to the loa, an materialis remo"e here it is o&solete. This 'rocess can &ecom'are to the groth of a &one or a tree.

Casting 'rocesses offer ieal 'rere-uisites to manufac$ture com'le com'onents esigne &y con"entional or &ionic methos. Disa"antages can &e foun in the ma$terial structure lie the eistence of 'ores an in the lim$ite choice of cast alloys ith loer yiel stresses com$'are to rought alloys (Ta&le 8). +n contrast to casting

Material Cast alloy =rought alloy +ncrease

cross sections. elating the strength of a material to itsensity, high strength steel (I66) an in 'articular

stainless steel &ecome lighteight construction materialscom'are to some aluminum alloys. De'ening on theactual alloy an grae, steel an aluminum are lieise

Aluminum AlCu:TiMg

827$:27

Magnesium AJ1 T<2:7$877

AlJn;,;MgCu

;87

AJB7A T;8:;$8B7

2


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semi$finishe 'roucts re-uire increase 'rocess nol$ege, the o&ser"ation of ifferent material &eha"iors, anthe e"elo'ment of esignate aa'ti"e forming 'roc$esses an tools 41@, 1B, 1, 275.

Iigh strength &ut lo uctile materials use for light$eight com'onents moreo"er aggra"ate the 'ro&lem of limite material istri&ution o'tions. +n orer to a"oi this,some solutions are at han incluing*

? forming at ele"ate tem'eratures,

? incremental forming,

? su'er'lastic forming, an

? thioforming.

Elevated temperatures

Forming at ele"ate tem'eratures loers forces anincreases uctility as aitional sli' 'lanes are acti"ate,es'ecially for magnesium 4215. Moreo"er, higher tem$'eratures ecrease s'ring &ac hich is an im'ortantissue using high strength materials. 9ut ith the tem'era$ture &eing a sensiti"e factor in forming o'erations, 'roc$ess 'arameter inos ha"e to &e carefully o&ser"e inorer to o&tain re'rouci&le results.

Incremental forming +ncremental forming 'rocesses are characterie &y asuccessi"e local forming of the or'iece instea of forming the hole or'iece at one time. =hile s'inningallos the manufacture of rotationally symmetric hollo'roucts, the incremental sheet forming (+6F) 'rocessan its eri"ati"es allo the manufacture of com'leasymmetric sha'es 422, 28, 2:5. =ith shear forming asell as +6F, "ery high strains com'are to con"entionalstretching or ee' raing 'rocesses can &e achie"e(Figure :) 42;, 2


5/23

'ossi&le &y the use of stainless steel. Iere, a &um'er &eam esign o'timiation introuce &eas into thecross section that ha"e to &e ee' ran (Figure ;). Thisre-uire for a material ith higher forma&ility &ut alloea smaller sheet thicness to &e use ue to higher strength an a larger cross section area. At the sametime, the high uctility can a&sor& aitional crash en$ergy. 6imulate ro' toer test e"aluate the crash 'er$formance of the o'timie esign. +n effect, to maintainthe same 'erformance as con"entionally esigne&um'er, a eight reuction of 27> as achie"e usingstainless steel A+6+ 871/ in col ore conition C1777.4:7, :15

For many years, fuel tans for 'assenger cars ha"e &eenmae of 'lastic &y the &lo mouling 'rocess, account$ing for a&out @7> of all tans 'rouce. +t allos themanufacture of com'le sha'es re-uire ue to com'le'acage limitations. 9ut legislation emans ero emis$sion of hyrocar&on from tans hich 'lastics use at'resent o not meet. 9esies iffusion tightness,stainless steel on the other han 'ro"ies high corrosionresistance, outstaning forma&ility, an high strengthcom'are to mil steel. 6till, the manufacture of such acom'le sha'e coul only &e achie"e &y the intense

use of finite element simulation. +n many o'timiationste's,

? the &est suiting forming 'rocesses using con"entionalan hyro mechanical ee' raing,

? ae-uate 'arameters in the "ery small 'rocess ino,as ell as

? tool an or'iece esign

ere achie"e. As a result, the stainless steel tan is27> lighter hile 'ro"iing :> more ca'acity than thecon"entional 'lastic tan ue to smaller all thicness(Figure


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flos in the miler 'art of the &lan. Therefore, ifferenttool conce'ts for tailore &lans are necessary.

The flei&le rolling 'rocess on the other han allos the'rouction of &lans ith almost ar&itrary thicness is$tri&utions in the rolling irection &y "arying the rolling ga'.Iere&y, multi'le local sheet thicnesses can &e ieallyaa'te to the loa. Due to or harening in the flei&lerolling, the yiel stress increases accoring to the cross$section reuction (Figure B). A''lying a ome height test

using a hemis'herical 'unch, tailor rolle &lans (T9)ith a thicness transition length a&o"e :7mm reachethe same ome height as a regular &lan. This is a greata"antage com'are to tailor ele &lans ue touctility reasons mentione a&o"e 4:;5.

Manufacture from such T9, first 'rototy'e a''licationsan e"en a mass$'rouce 'art are eamine. A eightreuction of 2;> com'are to a regular sheet asreache for a Mercees$9en #$class cross mem&er (Figure ). This 'art has &een stam'e successfully fromT9 ith thicnesses of 7.Bmm an 1.2;mm in toolsoriginally esigne for T=9. +n orer to ne"erthelessmatch the s'ecific tools, the shortest 'rouci&le thic$ness transitions ere chosen. An o'timal lighteightesign oul ha"e &een achie"e if longer, loa$aa'te

transitions ere use that then, hoe"er, oul ha"ere-uire a ne tool set. 41, :;5

For the manufacture of a &um'er mae from stainlesssteel T9, the air &ening on a 'ress &rae an the'rofile &ening on a three$roll$&ening machine asin"estigate (Figure 17). +nhomogeneous s'ring&ac ue

to a continuously "arying sheet thicness (1.72$1.22mm)an strength re-uire an ini"iually esigne ie. !singa regular 'unch, local "ariations of the ie height 'reset a"arying 'unch is'lacement in orer to com'ensate thematerial &eha"ior. Furthermore, for short transitions, asegmente ra'i tooling ie as manufacture &y laser cutting "$sha'e lamellas that ere ini"iually aa'te.

Con"entional steel heels are still the chea'est in themaret (a&out 27 !6O), com'are to cast aluminum

heels (a&out :7 !6O) or e"en forge aluminum heels(a&out @7 !6O). The isa"antage of hea"ier steelheels can &e com'ensate &y a &etter material istri&u$tion in the rim an the use of high strength alloys. A "ary$ing thicness o"er the rim can either &e achie"e &yfloforming or the use tailore stri's.

=hile s'inning the rim, a efine seamless thicnessistri&ution can &e manufacture &y a raial motion of theforming tool toars the manrel thus reucing the allthicness (Figure 11). +n an a''lication for a 1;< &aseheel of a mi sie car, the rim as manufacture from a2.2mm thic sheet, ith a s'un thinne area of 1.;;mmthicness using a microalloy steel (Figure 12). This re$uces the eight of the heel &y 27>. 4@5

9y the use of tailore stri's (narro tailore ele&lans ith multi'le thicnesses) rolle into a tu&ular sha'e, a similar eight reuction can &e achie"e uner economical conitions 4:85.

!orging

=ith the im'ro"e material structure of forge or$'ieces, the forming technology 'ro"ies a"antages o"er com'eting cutting 'rocesses. #s'ecially for the 'rouc$tion of &e"el gears, forge com'onents offer higher strength an 'recision accuracy that lea to a 'oer ensity im'ro"e &y 2;> com'are to con"entionallymachine gears as

? the grain flo in the forme teeth is 'arallel to the loairection (Figure 18),

? no fi&res are o'en in areas of high loa,

? an ieal contact 'attern can &e achie"e as all a'eesof all gears of the ifferential are in the eact same'oint, an

7.B7 mm

1.2; mm

Figure * Cross mem&er mae fromtailor rolle &lan 41B5.

1.2; mmoller

ollerhousing

Manrel

Dri"e ring

oller fee

reform

Materialflo

Flo$forme tu&e

Cross mem&er Figure 11* Floforming 4:


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the cutting clearance for the ho&&ing of the s'lines. Thisrun$out length is necessary for machining &ut not for forming. As a conse-uence, the cutting clearance can &ea"oie thus sa"ing aitional eight an s'ace (Fig$ure 1:). 4:@, :B5

The technological, ecological, an economical &enefits of forge gears ha"e le to a &roa maret. 9ut the gearsre-uire a 'recision forging 'rocess to meet the re-uiretolerances. This is usually achie"e &y a hot forging an

a su&se-uent col coining o'eration. +n orer to a''lythis forming technology to helical gears, a ie nol$ege of the essential 'rocess "aria&les is necessary ueto the more com'le tooth geometry an the higher sur$

alloy #%$A=@7;;$T@@ e.g. shos a yiel stress of


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fi&rous microstructure can &e 'reser"e in the material. As a conse-uence, the mechanical strength is 17>higher alloing for more lighteight com'onents. 4;85

A further alternati"e to hot forging is the arm forging atintermeiate tem'eratures. 6o'histicate heat treatmentscan &e a"oie as the forming 'rocess uses solutiontreate an ater -uenche aluminum thus &eing in soft&ut inee unsta&le conition. +n arm forging, flostresses are reuce an forma&ility increase. 6till a

'recision forming is 'ossi&le since the loer tem'era$tures com'are to hot forging mae it easier to ahere toclose tolerances. =ith a 'ro'er flo control, &etter me$chanical 'ro'erties can &e o&taine &y 'reser"ing thematerial orientation. 4;:5

Although the forming of aluminum 'ro"ies the 'ossi&ility

Figure 1lighter 4;;5 than con"entional steel heels. /ess esignrestrictions, 'ersonal istinction, an the s'orting imageof a lighteight com'onent are 'ro&a&ly of more concernfor the consumer. Aluminum heels mae from sheetmetal &lans in the same ay as con"entional steelheels are lighter &ut unfortunately loo the same hichleas to serious mareting 'ro&lems.

Forge aluminum heels on the other han 'ro"ie morefreeom of esign com'are to non$cast heels. Ai$tionally, forging sa"es 1;> eight com'are to castaluminum heels, ue to im'ro"e material structure,high strength alloy, an or harening. +n case of coaches ith eight or trucs ith tel"e heels, se"eralhunre g can &e easily sa"e. 4;;5

Tailored "lanks

Although tailor ele &lans (T=9) offer &oth 'otentialeight an cost &enefits, the continuous el$line anthicness ifference in T=9 can often result in ifficultyin stam'ing. This 'ro&lem is more se"ere in aluminum&ecause of its limite forma&ility as com'are ith ty'icalraing$-uality steels. Aitionally, eling of steel T=9tens to increase the strength of the el material hichhel's 're"ent failure in the el uring forming. Alumi$num T=9 o not e'erience this increase in strength antherefore may ha"e a greater tenency to fail in the el4;


9/23


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Iomologous tem'erature 7.2<7.82

Figure 27* Acti"ation of aitional sliing 'lanes for magnesium at ele"ate tem'eratures 4@85.

cally more a"ance aluminum alloys su'ersee theuse of magnesium. 4@25

=ith a ensity of 1.@:gmS, magnesium is a''roi$mately 8;> lighter than aluminum. 9ut ue to the close'ace heagonal (c'h) crystal lattice structure at roomtem'erature, magnesium 'ro"ies only lo uctility for col forming o'erations. At tem'eratures a&o"e 22;PC,aitional sliing 'lanes are acti"ate thus increasinguctility an loering the yiel stress, &esies the con$"entional tem'erature effect on uctility an yiel stress(Figure 27). 4@85

Furthermore, isa"antages of magnesium com'rise'oor cree' resistance at tem'eratures a&o"e a&out177PC as ell as corrosion. Iere,

? chemical corrosion ue to en"ironmental influence e.g.salt,

? electro$chemical corrosion ue to a high electro nega$ti"ity com'are to aluminum an steel leaing to se"ere'ro&lems in 0oining, an

? stress cracs corrosion ue to "ariations in stress

are of main concern.

%e"ertheless, the 'rouction of magnesium automoti"e'arts is currently e'eriencing a ra'i groth hich re$sults mostly from high 'ressure ie castings accountingfor ;> of the 127,777 tons magnesium orlie yearlyuse (num&ers &y 2777). 6o far, only a limite num&er of ifferent alloys is a"aila&le com'are to aluminum alloys.

Therefore, much effort is &eing unertaen in alloy e$"elo'ment im'ro"ing material 'ro'erties es'ecially con$cerning higher cree' resistance at ele"ate tem'eratures4@:5 or the increase of forma&ility &y the introuction of lithium as an alloying element 4@;5. =rought alloys on theother han i not e'erience this ramatic groth al$though they generally offer &etter mechanical 'ro'ertiesthat can e"en &e enhance &y ae-uate heat treatment.Iere, AJB7A an JK


11/23

B7

Ierenguel /acom&e $

of the heels

877 Ieating one* ca. 22;P C

Cooling one* ca. 1;7P C

use ere mae of cast magnesium, 27> of car&oncom'osite, an 17> are forge magnesium heels. 6till,

unch

117

unch* ca. 1;7P C

Cooling 'late

+nsultating 'late

Die (resistance

heating)

9lanholer

the eman for forge heels rises ue to their eight

(resistance

heating)

+nsultating 'late

Cooling 'late

(resistance

heating)+nsulating 'late

Cooling 'late

illar

Figure 2@* A''lication of forge magnesiumheels in motorcycle racing 4B:, B;5.

Material rocess =eight in g el. =eight

Figure 2;* artially heate ee'$raing tool 4@8, @@5.6teel 6tam'ing,

rim rolling(1:.2)

1177>

&lan ith fine grains an a sta&ilie structure (Fig$ure 2:). 4B2, B75

Aluminum Casting B.;

As col forming of magnesium is harly realistic, ee'raing of magnesium sheet also has to &e carrie out at

Aluminum Forging,rim rolling

(@.2)1

;1>

ele"ate tem'eratures. Due to the significant sensiti"ity Magnesium Casting 8.$:.2 2B.;>

of forma&ility to tem'erature, 'artially heate &lan hol$ers are a&le to control the forming 'rocess "ery accu$rately es'ecially for com'le geometries. +n straightflange areas, mainly raial stretching ith less true strainoccurs. The corners are ominate &y an o"erla''ing of

Magnesium Forging,floforming

Car&onCom'osite

8.2$8.; 28.

2. 27.:>

raial stretching an aitionally a tangential com'res$sion ith high true strains thus re-uiring higher forma&il$ity. Iere, a 'artially heate tool set 'ro"ies a suit$a&le tem'erature istri&ution an therefore a istri&ution

Ta&le :* Com'arison of


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of forging the heel isc an flo$forming the rim fromthe flange of the isc. 9oth 'rocess ste's ha"e to &ecarrie out at tem'eratures a&o"e 22;PC. The flo$forming itself runs in three ste's* s'litting u' the flange,flo$forming the rim, an cali&rating the rim contour.De'ening on the re-uire material 'ro'erties, the heelcan afterars &e sta&ilie, age, or heat treate. Af$terars, the heel is machine &y turning the face siesan the rim, milling the s'oes, an rilling the "al"e holeas ell as coating an 'ainting (Figure 2@ right). As a

conse-uence, the magnesium forge heel at a eightof 8.2g is 1g lighter than the cast "ersion 4B2, B;5. nlythe car&on com'osite heel is yet another 17> lighter 4B85.

!(4 Titanium

A'art from con"entional an commonly use lighteightmetals, "arious other ne materials offer the 'otential for lighteight com'onents that re-uire forming o'erationsan a''ro'riate 'rocess nolege. First of all, titaniumis use in etreme a''lications that concern lighteightas'ects. Furthermore, sanich an foam materials&ecome more an more a"aila&le.

Titanium offers su'reme 'ro'erties hich amongst oth$

ers inclue? a ensity near half that of steel,

? highest strength,

? corrosion an high tem'erature oiation resistance,an

? a moulus of half that of steel.

!nfortunately, titanium is etremely e'ensi"e ith a&out87$127 !6O 'er g com'are to a&out 1 !6O 'er gcar&on steel ('rices for sheet metal &lans). Therefore,titanium is only consiere in lighteight a''licationshere eight sa"ing yiels an outstaning economical&enefit lie in the aeros'ace inustry, an ege in com'e$tition lie in motors'ort, or a 'rouct "alue lie for 'ros$

thesis ue to its tissue com'ati&ility. +n motors'ort, tita$nium is ieal for 'roucts in the ehaust system, s'rings,connecting ros, 'istons, "al"es, an many more. As aconse-uence, such items ha"e &ecome a"aila&le com$mercially.

+n the aeros'ace inustry, titanium 'roucts are ielyuse &ut not so much for lighteight reasons. +n the mainstructure of the Air&us A8878:7, titanium only accountsfor @> of the eight, in contrast to the engine heretitanium is the main material in terms of "olume (Fig$ure 2B left) 4B:5. This is first an foremost ue to its highstrength at high tem'eratures e"en com'are to %i$&ase su'eralloys. Furthermore, in the a''lication of ahelico'ter rotor hea, titanium is use for its highestura&ility uner ynamically changing loas (Figure 2B

right) 4B;5.The material 'ro'erties an forming &eha"ior of titaniumalloys are ell ocumente in many research stuies

Figure 2B* Titanium a''lications in

the aeros'ace inustry 4B:, B;5.

carrie out to su''ort the aeros'ace inustry. This in$clues most of all the manufacture of s'herical "esselshere 6F is commonly use e.g. for satellite or rocettans 4B


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Concepts and semi#finished products

+n most cases of the a&o"e mentione a''lications,straight semi$finishe 'roucts are 0oine to com'lestructures. As steel is much chea'er than other metalsith almost ientical s'ecific 'ro'erties, those structuresare nearly all mae of steel. +n contrast, in the case of trans'ortation a''lications, cur"e 'rofiles an tu&es arenecessary ue to aeroynamics, structural 'ro'erties,an esign reasons. Iere, a commercially ri"en com'e$

tition of materials has e"elo'e. Con"entional steel shellstructures are &eing re'lace &y aluminum frame struc$tures. Achie"e eight sa"ings o"er eisting structuresare accreite to the em'loye lighteight material. At acloser loo, hoe"er, each ne esign generation islighter than the one &efore. Therefore, rather the im$'ro"e esign than the actual material is accounta&le.

+n contrast to automoti"e shell structures, only sim'legeometries are use in frame structures. +n many a''li$cations, most of the mem&ers are tu&es ith roun or rectangular cross sections. =ele roun tu&es are "erycommon in ale tu&es, &icycle frames, garen chairs, or si stics. #true tu&es are use in sim'le s'aceframes lie the 9M= C1 (Figure 87). !nfortunately, they

may sho "ariations in all thicness of u' to 27>.Therefore, a su&se-uent col raing is a''lie to ai$tionally yiel closer tolerances an &etter mechanical'ro'erties. At least, seamless tu&es offer &est mechani$cal 'ro'erties. Due to high cost, they only account for asmall maret segment lie in helico'ter laning "ats,ri"e shafts, or hyraulic 'i'es. 4;5

+n automoti"e a''lications, single hollo etrusions 're$"ail. #s'ecially in lo "olume 'rouctions lie 'rototy'esor niche cars, more an more s'ace frame &oy$in$hites are mae from aluminum etrusions (Figure 81)4:5. This is mainly ue to the fact that etrusions offer ecellent cross section esign 'ossi&ilities to inclueaitional functions together ith the mere structural'ro'erty of high moment of area inertia 4 of hich are cause &y the tooling 45. Therefore, aeight sa"ing of 8;> to com'ara&le cars is only e$

'ecte at a cost increase of 1;> for a 'rouction "olume

Figure 87* Tu&ular frame structure of the 9M= C1.

Figure 81* rofile &ase frame structureof the Ferrari F8


14/23

rical tu&es that, hoe"er, can &e 0oine to tailore tu&esith ifferent all thicnesses, materials, or material'ro'erties.

The iscontinuous secon "ariant uses sheet metal&lans &eing &ent in three ste's on a 'ress &rae intoo'en tu&es that are su&se-uently laser ele. Due toloer tooling an in"estment cost, this 'rocess offers aneconomical &enefit at loer &atch sies. Aitionally, for a &etter loa aa'tation, conical tu&es can &e manufac$

ture. 9y the use of tailore &lans, this technology isalso suita&le for the 'rouction of tailore tu&es. Fur$thermore, the 'rocess can &e a''lie to materials liestainless an high strength steel, aluminum, or titanium.4, 1715

dvances in forming technolog$

+n contrast to the sheet metal half shells of con"entionalcar &oy manufacture, the aluminum 'rofiles alreaysho a high stiffness. Therefore, the hanling e-ui'mentcannot assure efine ga' geometries &y a''lying forcesto the or'iece. As a 'rere-uisite for automate alumi$num eling, a maimum ga' of a''roimately a thir of the all thicness is re-uire. +n case of the aluminumetrusions of the Aui AB, taing into consieration han$

ling tolerances an eling istortion, straight ancur"e 'rofiles must meet the re-uire contour toler$ances of W7.8mm. As con"entional 'rofile manufacturerscannot fully reach this re-uirement ue to limitations inthe etrusion 'rocess an &ening e"iations cause &ys'ring&ac, cur"e an e"en straight 'rofiles in somecases ha"e to &e cali&rate e'ensi"ely &y hyroforming.

Achie"ements in forming technology &y increasing theaccuracy of cur"e 'rofiles contri&utes to lighteightforming &ecause aitional cost es'ecially in lo "olume'rouction 're"ent lighteight com'onents to &e eco$nomically manufacture an use throughout the maret.

9y em'loying cur"e tu&es, sim'le &ening o'erationscan &e integrate into the hyroforming 'rocess. Al$though the tu&e might rinle in the cur"ature raius

uring 're$&ening hile closing the ie, this effect iseliminate &y the main hyroforming 'rocess ste'. 4B,

ing of structural 'rofiles an tu&es uses a 'olyurethanematri. A "ertically a0usta&le rigi roll 'resses the or$'iece against the matri casing. The elastic matri e$forms an thus &ens the or'iece. 9y a longituinalmo"ement of the casing, a cur"ature is manufactureo"er the length of the or'iece. A "ariation of the rolla0ustment an of the forces a''lie on each sie of theroll results in a "aria&le 8D cur"ature. The maimumlength of the cur"e or'iece is hoe"er limite &y the

length of the matri casing. 41785+n con"entional stretch &ening, the accuracy of sha'ecan &e im'ro"e &y an aa'ti"e 'rocess control. !sually,the s'ring&ac is taen into account in the tool esign sothat the 'rofiles are o"er$&ent. =ith the assume s'ring$&ac, the esire sha'e is achie"e. 9ut "ariations in the&ening &eha"ior resulting from ifferent all thicnessesas ell as -uenching or heat treatment conitions maylea to "arying s'ring&ac &eha"ior. 9y measuring thea''lie forces o"er the tool mo"ement uring the first&ening 'hase, the material an s'ring&ac &eha"ior can&e estimate. As the s'ring&ac is also etermine &ythe aial tensile stress, an aa'tation of the tensile forceto the estimate s'ring&ac &eha"ior im'ro"es the sha'eaccuracy of the &ent 'rofile (Figure 88). 417:, 185

An inno"ati"e etrusion 'rocess "ariant 417;5 'roucescur"e 'rofiles irectly at the 'ress. The stran eitingfrom the ie is inserte into a guiing tool. 9y mo"ing thetool to a numerically controlle lateral 'osition, a resultingforce is a''lie to the 'rofile. As a conse-uence, the'rofile eits the ie in a roune sha'e (Figure 8: left).

The forming mechanism consists of to effects that tae'lace (Figure 8: right)*

? A''lie on the stran o"er the istance of the guiingtool from the ie, the lateral force leas to a resultingmoment on the material flo insie the ie. This mo$ment leas to 'ressure stresses on the inner sie, antensile stresses on the outer sie of the 'rofile.

?

The lateral force leas to a higher surface 'ressure onthe &earing an there&y a higher friction force on theinner sie of the 'rofile. The loer surface 'ressure on

rofileDri"e

Clam's

Tool Dri"es'inle

1775

Com'le 8D &ening of tu&es an 'rofiles re-uires ne'rocess technology. ne a''roach uses a fie tool an

oint /oacells

y

Iyraulic

a mo"ea&le ie. The ie is 'ositione in si aes &y a

'arallel inematics that is etermine &y the re-uire&ening s'ace an resulting &ening forces. 9y "aria&lya0usting the ie 'osition to the aial fee of the tu&e, theor'iece can &e &ent in a "aria&le 8D sha'e (Fig$ure 82). 41725

Another inematic a''roach in flei&le 2D an 8D &en$

Ta&le cyliner

Figure 82* Com'le 8D &ening of tu&es 41725.

Figure 88* Aa'ti"e stretch &ening 417:, 185.


15/23

Figure 8:* rocess 'rinci'le rouning uring etrusion.

the outer sie of the 'rofile leas to a loer frictionforce.

9oth effects result in a "elocity 'rofile of the material flothat is ifferent from con"entional straight etrusion. Thematerial "elocity on the inner sie of the 'rofile is loer than on the outer sie. This causes the 'rofile to eit theie in a roune sha'e. As a conse-uence, rouning

uring etrusion is not a &ening 'rocess. eferring toD+% B;B


16/23

As this 'rocess maes use of sheet metal &lans, it isalso 'reestine for the manufacture of hollo lighteightcom'onents as su&structures (Figure 8< right) or larger shell structures.

.(! 'hell structures

+n contrast to frame structures use for small$ an me$ium$lot 'rouction, shell structures for automoti"e car &oy a''lications are esta&lishe for large$lot 'rouction.+n contrast to casting 'rocesses, only forming technology

is a&le to 'ro"ie large thin alle hollo com'onentsith a surface -uality suita&le for outer sin 'anels.

As the material 'rice accounts for a&out ;7> of the total"ehicle cost at large$lot 'rouction 4175, steel is com$monly use. =ith the nee for eight reuction 'articu$larly in the front of the car, more e'ensi"e materials liealuminum an e"en magnesium are consiere for sheetmetal a''lications. Although 'ro"iing the same s'ecificstrength an stiffness, their loer ensity results in ahigher sheet thicness at the same eight 'er area thusconsiera&ly increasing s'ecific ent resistance an shellstiffness. Due to this shell relate material 'ro'erties,eight sa"ings of aroun ;7> com'are to steel an27> com'are to aluminum can &e achie"e using mag$

nesium in a''lications ithout strength re-uirement liefront hoos, trun lis, an oors 4@5. =hereas in crashrele"ant com'onents lie a 9$'illar &ottom reinforcementcontri&uting to crashorthiness es'ecially in 'olecrashes, ultra high strength steel graes lie C B77 incase of the DaimlerChrysler 6$class cou'e are em'loye41125.

Different stuies ha"e &een carrie out to in"estigate thefeasi&ility of ultra lighteight car &oies. =hile the!/6A9 consortium 'ro'agates the mono$use of steel(Figure 8@ left) 41185, For e"elo'e the 2777 as anall$aluminum car &oy in a shell structure esign (Fig$ure 8@ right) 4:, 11:5.

=ith the eman to ecrease costs in lighteight struc$tures, sheet metal 'arts ha"e to &ecome larger (Fig$ure 8B) as

Figure 8@* Full steel an full aluminumcar &oy conce'ts 4118, :5.

? 0oining 'rocesses an auiliary 0oining 'arts ecrease,

? logistics an finishing o'erations get easier, an

? the 'rocess chain &ecomes shorter. 4112, 11;5

9y this on the other han, the or'ieces an their re$s'ecti"e forming 'rocesses are getting more com'lean ifficult not only ue to the sie &ut also &ecause of the use of tailore &lans. =hereas &efore, 'arts of if$ferent thicnesses ere 0oine in the assem&ly, no

single 'arts consisting of ifferent all thicnesses areuse as semi$finishe 'roucts (Figure 8) 41185.

From the material use, s'ecific forming 'ro&lems arisein ee' raing an relate 'rocesses. +n aluminumconce'ts, close attention has to &e 'ai to the s'ecificforming &eha"ior of aluminum. As'ects lie aa'teraing e'th, larger raii, an a homogenous fee areto &e taen into consieration. 411;5

Furthermore, aluminum is etremely sensiti"e to surfaceefects cause mainly &y its high ahesion tenency anthe e'osit of or'iece sarf. nce the lu&rication filmiscontinues, aluminum instantly aheres to the toolsurface. 6u&se-uently, this leas to groo"es anscratches on the or'iece as ell as to an increase in

tool ear. Aitionally, ue to the sensiti"ity of aluminumto slight changes in the cutting clearance, the cutting'unch can generate sarf that is 'resse into the or$'iece surface. The use of moern tool coatings, toola0ustment, an lu&ricants hel's to 're"ent high scra'rates. 41125

Also in the 'rocessing of steel sheets, the use of highstrength graes leas to significant challenges as higher tool stresses result. +n orer to 're"ent rinling, the&iner has to a''ly higher forces causing rele"ant toolear an maing 'remium tool material, tool coatings, or e"en the use of ceramic inserts necessary. The highstrength of the material is also res'onsi&le for an in$crease in s'ring&ac that has to com'ensate &y a 'ro$gress in the use of F#M$simulations 411


17/23

Define area of an elastic segment

a &! in1 !

in2 ! Ain8

Figure :1* Different multi'oint &lanholers 4121, 1225.

! ! ! 9I 9I2 2

87 mm

Figure :7* Dee' raing of unfoame sanich sheet(to' an mile) 41275, ee' raing of foam using

co"er sheets (&ottom) 4


18/23

!

oint

Tool

F6=

Figure :8* Friction stir eling 'rocess 'rinci'le (left)an ee' ran F6= 'art (right) 4T=+5.

a''lie. oining &y forming is an alternati"e to esta&$lishe resistance or arc eling techni-ues es'ecially incase of limite fusion ela&ility. Mechanical eling'rocesses lie stir an inertia friction eling ha"ea"antages as a soli state 'rocess, clinching anri"eting are also a''lica&le to hy&ri structures 412B5, anelectro$magnetic forming in aition 'ro"ies a high"elocity an contact free forming 'rinci'le.

!riction stir %elding

De"elo'e &y T=+, friction stir eling (F6=) uses a

ear resistant rotating tool hich mo"es along the 0oint&eteen to com'onents. The tool shouler &eing inclose contact ith the surface 'lastifies the material &e$neath hile the tool 'in tra"erses through the 0oint linethus creating heat &y friction (Figure :8 left). As a soli'hase 'rocess, F6= o'erates &elo the melting 'oint of the or'iece material. +t can el all aluminum anmagnesium alloys, incluing 0oining issimilar alloys anthose materials that cannot &e con"entionally fusionele such as aluminum$lithium alloys. %o shieling gasor filler is re-uire. Material 'ro'erties of ele alumi$num alloys sho tensile strength similar to the 'arentmaterial after heat treatment although full elongation isnot restore. 412, 1875

As the el seam still shos goo forma&ility an energy

a&sor'tion for crashorthiness, F6= sheet metal &lanscan &e easily use as tailore &lans for ee' raing(Figure :8 right) or s'inning 41815.

Inertia friction %elding

6'inles as a chassis com'onent ser"e as the maininterface &eteen non$ri"en heels an the sus'ensionsystem. Traitionally, s'inles are manufacture &y

? machining a single$'iece steel forging or

? 0oining a machine steel shaft to an iron s'inle.

The s'inle &oy, hoe"er, can &e 'rouce in alumi$num ith a 87> eight reuction hile maintaining allstructural re-uirements. +nertia friction eling as e$amine as an alternati"e 0oining metho. +n this 'rocess,

one com'onent is hel stationary hile the secon isrotate at a controlle "elocity. The faying surfaces con$tact each other uner the a''lie 'ressure an createheat. The aluminum s'inle &oy &ecomes 'lastic at theinterface, filling the ga' to the shaft. 4182, 1885

Electro#magnetic forming

+n electro$magnetic forming, the energy of a 'ulse mag$netic fiel is use ith a contact free tool to 0oin metalsith a goo electrical conucti"ity, such as aluminum.The suen ischarge of a high "oltage ca'acitor through a tool coil causes the generation of an intensemagnetic fiel insie the coil. This magnetic fiel in$creases ithin a fe microsecons u' to its maimum sothat, in turn, an ey current in the or'iece is inuce

generating a secon magnetic fiel re"ersely irecte tothe tool coil fiel. The forces acting &eteen tool coil an

Figure ::* #lectro$magnetic forming tool coil ith or'iece (left) an ifferent

0oining 'rinci'les (right) 418;, 18


19/23

At the same time, more com'le sha'es ill ha"e to &emanufacture &y forming 'rocesses as a conse-uence of an integrati"e lighteight construction. nly or'ieceshich are ieally aa'te to the gi"en loa istri&utionan hich use the &est material a"aila&le ill succee inlighteight construction. Forming 'rocesses here illha"e to ensure feasi&ility. Furthermore, in orer to attaino'timal loa aa'tation of 'rouci&le or'ieces, a com$&ine 'rouct an 'rocess esign &y means of finite

element simulation or the use of &ionic methos is fa"or$a&le.

This inclues concurrently the use of more com'lesemi$finishe 'roucts lie tailore or hy&ri 'arts. Io$e"er, those 'roucts re-uire an increase 'rocessnolege an the o&ser"ation of ifferent material &e$ha"iors. Iere, aa'ti"e 'rocesses an tools an the yetincreasing use of simulation softare is a"antageous.

3ariations in manufacturing 'rocesses lea e.g. for e$true 'rofiles to

? "ariations of a&out W17> in all thicness &ecause of the etrusion 'rocess an

? "ariations of a&out W17> in material 'ro'erties &e$cause of the -uenching conitions.

Designing a lighteight or'iece, these "ariations ha"eto &e o&ser"e as a orst case assum'tion hence gi"ingaay 'otential 27> of eight sa"ing. 9y achie"ing closetolerances in manufacturing 'rocesses an in the 'reic$tion of the or'iece &eha"ior e.g. effects of ifferencesin or harening, aitional lighteight 'otential can &eacti"ate. This also relates to increasing emans for close$tolerance semi$finishe 'roucts accom'anie &ythe necessary nolege of the s'ecific 'rouct history.The nee for high accuracy forming faces a steaygroth also ue to other reasons an therefore &ecomesgroingly rele"ant. Ioe"er, it 'rere-uisites a''ro'riatemoeling as ell as the ac-uisition of more eact an&etter suiting material 'ro'erties.

Finally, the reuction of com'onent eight alone ill not&e sufficient in the future as the &enefit of less eightusually oes not 0ustify the often associate increase of cost. n the one han, the reuction of cost e.g. &yshorter or more flei&le 'rocess chains is crucial. Mean$hile, es'ecially ultra lighteight com'onents re-uireflei&le 'rocesses as they are generally manufacture insmallest &atch sie ue to their limite a''lica&ility. nthe other han, ae "alue &eyon the mere reuctionof eight ill legitimie the use of moreso'histicate

&ility can ecrease maintenance costs if 'rolonge ar$ranties are consiere.

7 CLO'IN"R%M&R8'

Forming technology can su&stantially contri&ute to light$eight construction. This 'a'er escri&es necessitiesan functional as'ects if lighteight construction as ellas the common 'ro&lems in manufacturing lighteight

materials, semi$finishe 'roucts, com'onents, anstructures. +t is 'ointe out ho loa aa'tation is thecentral ey to success. Therefore, a ie range of solu$tions are iscusse in orer to o"ercome limitations informing. Iere, inno"ati"e 'rocesses 'lay a ma0or role.Finally, fiels of 'otential further research are ientifiean iscusse.

*&C8NO$L%D"%M%NT

The authors oul lie to gi"e s'ecial thans to the fol$loing 'ersons ho ha"e contri&ute to this 'a'er (C+mem&ers enote &y X*

%. 9ayX

#.DoegeX

I. Flegel

F. Ga&rielliX

. GrocheX

. esietX

M. KiuchiX

. Ko''X

.

%euge&auerX K.

saaaX

K.6iegertX

R%F%R%NC%'

415 6chrecen&erger, I., /auien, G., 2777, DasKorrosionsschutone't er Aluminum$Magnesium$Iy&rihecla''e es 3= /u'o.roceeings Fortschritte mit Magnesium im Au$tomo&il&au, 9a %auheim, D, :1$;7.

425 Gao, ., 2777, Ceramic matri com'ositesfor is &raes an their manufacturing tech$nologies. roceeings @th +nternat. 6ym'. Ce$ramic Materials an Com'onents for #ngines,

A''lications in #nergy, Trans'ortation an #n"i$

ronment 6yst., Goslar, D, 18$1.485 .ulsas .o r g.

4:5 Jengen, K.$I. "on, 2772, Aluminum the light&oy material. roceeings of %e A"ances in9oy #ngineering, ia Aachen, D.

4;5 %.%., !ltralight 6teel Auto&oy A"ance 3ehi$cle Conce'ts (!/6A9$A3C) .ulsa& $a"c .o r g.

4


20/23

1, To'ology o'timiation of large real orlstructures, %AF#M6 =orl Congress, %e'ort+, !6A.

41


21/23

%e e"elo'ment of thermomechanical'rocessing (TM) an high "olume 'rouctionaluminum heel sus'ension arms. roc. of

ATTC#, 3ol. 8, Manufacturing, Automoti"e ?Trans'ortation Technology, 9arcelona, #, 6A#$, 3ol. $8


22/23

4:5 Al&erti, %., Forcellese, A., Fratini, /., Ga&rielli,F., 1B, 6heet Metal Forming of Titanium9lans !sing Flei&le Meia. Annals of theC+ :@1, 21@$227.

4;5 %.%., /eicht un och sta&il, +ntelligente /eicht$&auone'te mit Aluminumrohren. Gesamt"er$&an er eutschen Aluminuminustrie. .aluin fo .e 2: .h tml.

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Documents

(748111576) Keynote Paper F 2003 Lightweight Forming