Using Selective Laser Sintering to produce Scaled Structural Models

Transcription

1 Procding of th SEM Annual Cfrnc Jun 1-4, 29 Albuqurqu Nw Mxico USA 29 Socity for Exrintal Mchanic Inc. Uing Slctiv Lar Sintring to roduc Scald Structural Modl Cook, W R* and Tolin, R A; Th Univrity of Shffild Burgut, R L, John, D and Vanard, G J C; Airbu Fathrt, C A; Cardiff Univrity *Dartnt of Mchanical Enginring, Th Univrity of Shffild, Shffild, S1 3JD, ENGLAND; ail: [email protected] ABSTRACT: Colx or n-linar Finit Elnt Analy ar by thir vry natur uncrtain. It i dirabl thrfor to validat xrintally any rult thu roducd. Traditial thod of roducing tructural odl ar, howvr, both low and xniv, rducing th nubr of validatd dign cycl which ay b coltd for a givn ti and cot. An additiv layr anufacturing thod known a Slctiv Lar Sintring (SLS) i thu uggtd a a thod for roducing cald tructural odl both raidly and at low cot. Th odl would b analyd uing uitabl xrintal tchniqu, uch a Digital Iag Corrlati, undr rducd load drivd uing dinial analyi thod. It i th ai of th currnt work to dtrin th otntial accuracy of tructural analy coltd uing cald odl roducd by SLS. To thi nd, th dirctial rorti of a co SLS atrial wr accuratly dtrind, in additi to th ffct of th obrvd orthotroy th xrintal analyi of a hol in a finit lat in tni. Furthr, th uitability of roducing SLS odl of tiffnd anl for buckling analy ha bn dtrind by xrint. 1. NOMENCLATURE a D d E G O 12 P P cr P cr,1 P cr,2 S E S w w ε ε f ε 1,VM,ax ε 2,VM,ax θ ν σ ax,1 σ ax,2 σ UTS hol diatr ditorti rror cific ditorti rror Young odulu (ubcrit dnot dircti) har odulu (ubcrit dnot lan) orthotroy load critical buckling load critical buckling load of rototy critical buckling load of odl Young odulu cal factor gotric cal factor lat width train train to failur axiu v Mi train in th rototy axiu v Mi train in th odl angl btwn atrial 1-dircti and th dircti of loading (off-axi angl) Poi ratio axiu tr in th rototy axiu tr in th odl ultiat tnil trngth

2 2. INTRODUCTION Finit lnt analy (FEA) ctain crtain inhrnt uncrtainti. Evn auing th virtual odl ha bn ctructd corrctly and uitabl boundary cditi and load alid, th accuracy of th oluti i till ctraind by th tchniqu itlf [1]. Dicrtizati, th divii of th virtual odl into th finit lnt rquird to colt an analyi, will alway liit th roluti of analyi (of articular ccrn in ara of high train gradint uch a at crack ti and har cornr). In cific ituati, accuracy ay alo b lot du to rounding rror in th athatical odl caud by th u of nubr with finit rcii (known a atrix illcditiing). In afty-critical indutri (tho with an oftn high art cot and low failur tolranc, uch a th aroac, rail and nuclar indutri), uncrtainti in FEA ay lad to th nd for dvlt tt uing rototy cont to vrify th nurical analy. Th ovrall dign roc ti and cot would thu b incrad du to th lg lad ti aociatd with rlativly xniv traditial rototying thod uch a CNC achining. Thi incra in ti and cot lad to a rducti in th nubr of dign itrati which ay b coltd in a givn cycl, thu rducing dign quality. In th wort ca cnario, failur of th dign at a lat tag in th roc, and th nd for xniv and ti cuing rdign [2], ay rult. A thod for raidly and accuratly roducing colx tructural odl of rototy dign would thrfor b of grat u. Additiv layr anufacturing (ALM) i th gnric tr for a grou of tchnologi that bgan to rg in th lat 198, dignd to build cont dirctly fro CAD data without th nd for art-cific tooling, through th layr-by-layr additi of atrial [3]. Such tchnologi how otntial for roducing colx tructural odl for dvlt tting at a fracti of th ti and cot of traditial rototying tchniqu, articularly a th a CAD odl ud for FEA ay alo b ud for odl roducti. On of th ot oular ALM tchniqu, known a lctiv lar intring (SLS), i cidrd to how articular roi for tructural odl roducti du to th wid rang of atrial it i abl to roc [4-7]. Th lctiv lar intring aaratu (figur 1) cit of: a owdr bd and fd hor, hatd to within a fw dgr of th intring tratur of th owdr; a lvlling dvic (ithr a blad or a countr-rotating rollr); a CO 2 lar, ctrollabl in th horiztal (xy-) lan by canning otic and working in th 25-1 W rang; and a ctrol coutr. At th tart of a build, th ba of th owdr bd i locatd layr thickn (btwn.1 and.25 ) blow th ri of th owdr bd. A layr of owdr i thn rad ovr th bd by th lvlling dvic, having bn rlad by th rlvant fd hor. Th lar thn ratr can th cro cti of th art to b built, hating and intring th owdr to for a olid layr. Th ba of th owdr bd thn indx down by a ingl layr thickn, and th roc ratd. Th lar owr i ctrolld uch that ubqunt layr will alo b intrd to tho rcding. Unintrd owdr act to uort th art during th build, and ay b rovd aftr colti and cooling of th build. Prviou tudi hav hown that art built by ALM tchniqu ay xhibit ignificant lvl of orthotroy and ridual tr [8-1], although no colt tudi of th orthotroy of any SLS atrial xit in th litratur. It ha alo bn hown that oiti within th build volu ay hav an ffct of th rorti of th atrial roducd [8], and a uch SLS art ay b inhoognou. Thu, uing SLS odl to vrify nurical analy of rototy aud to b iotroic, hoognou and ridual tr-fr by dinial odlling thod [11] will lad to inaccuraci in th analyi, known a ditorti rror. It i th ai of th -going tudy to dtrin th currnt uitability of SLS to Figur 1: th lctiv lar intring (SLS) aaratu, howing th aaratu x- (rcoating) and z- (vrtical) dircti. Th aaratu y- dircti i orthogal to th, into th lan of th ag.

3 roduc cal d tructural odl for xxrintal validati v of finit lnt analy by dinial odlling thod. To thi nd, th dirctial chanical rorti of a co gla-filld g o olyaid SLS S atrial h hav bn fou und. Th lv l of ditortio rror caud by varying g lvl of o odl orthotro y th ana alyi of a c co tr rair ro ototy, a finiit lat with a hol in t ni, hav bn dtr ind nuriccally, and iilar lat odl builtt by SLS and analyd xrintally. A cd d co aroac a trructur, a r rinforcd an nl, ha alo o bn roduccd by SLS and a ttd in n cori n, and th r ult coarrd to th F FEA of th a tructur THE DIRECTIONA D AL MECHANIICAL PROPE ERTIES OF DURAFORM D GF d tn il cin n cratd ovr two build d In total, 34 dogb w wr ud to dtrin th h chanica al rorti of DuraFor G [7] whn roducd GF n a Sintrta ati HiQ latfor [12 2], b both roducd d by 3D Sytt Inc. Th firt build (hown in figurr 2 citd of 72 ci 2) n cratd d aralll to th t z-dirctio (vrtically, rndicular to t th layr lan), and 36 cin n c cratd in botth th x- and y-dircti (horiztally, ( in th lan of o to th rcoating dirctio th layr, a aralll and rndicular r rctivly). Th cd build citd of cin n a arrangd a in i th firt, lu 16 cin angld d at 45 to th h lan of th la ayr to allow w th har odulu of th atrial to b b f found a dccribd by J [13]. All cin wr ttd A d in tni to failur at a cro ha ad d of 2 /in. Fro th firt build, b 18 of th t z-dirctio cin w wr lctd d and allow d to ag fo or 43 day in u unctrolld ( (abint) c nditi. All of o th raining cin n f fro both builld wr tt d within 7 da ay of build co olti, an nd w wr tord in n a dry and da ark nvir nt rior to t ting. Z X Y Figur 2: 144 off dogb b tnil cin (build 1).. Showing th 72 7 vrtical ciin and 72 horizztal cin n (36 x-dirctio and 36 y-dir cti). Analy yi and dic cui Fro figur 3 and tabl 1, it ay b n F that th atrial i tranvrly y iotroic in Young odulu. You ung odulu in th horizztal (x- and d y dircti vari by 2..5% and.7% y-) % for build 1 a and 2 rcctivly, whr a in th z-dircti it i 1 1.5% and 1.1% lowr than th horizo tal an for b build 1 and 2 rctiv ly. Th at rial ay b hown to b iilarly tran vrly iotrroic in train n to failur. Th tranvr ly iotroic rorti ar a would b xctd a for a art roduccd in a layr-b by-layr fahi, and ar furthr cffird by th f fact that th har oduli in zx- and zy-lan arr STRESS / MPa Exal tr-train roffil for x-, y- and z-dirctio E, and z-dir cti (agd) cin fro f build 1 ar a hown in n figur 3. Th h lack of d find linar latic and n-linar n ccti of th tr-train rofil rvvntd th y yild tr off th atrial fro bing dtrind, d an nd forcd You ung odulu u E to b dffind a th gradint g of cin th rofil at train ε =. Ultiat U tnil trngth σuts and train n to failur ε w wr dtrin nd for ach U f in n th uual annr. Th an and tandard dviati of th x-, y- and z-dircti ro orti for bo oth build a and th z-dir cti agd cin fro o build 1 ar hown in tabl 1, algid th ro orti quot d by th anufacturr.. Poi ratio ν wa found to b qual in all dircti, with h ν =.36 for build 1 and ν 45 =.37 for bu uild 2. Th h har oduli G dtrind d f build 2 w for r qual in th h zx- and zyy-lan, with h 4 Gzx = Gzy = GPa, butt diffrnt in th xy-lan, z-dirctio (agd) 35 w Gxy = 1.6 GPa. with z-dirctio 3 y-dirctio 25 x-dirctio STRAIN Figur 3: xal tr -train rofil for x-, y- and z-dircti z atrial, and d z-dircti (ag gd) atrial.

4 qual and diffrnt fro that in th xy-lan. Th ultiat tnil trngth ay b n to b or gnrally orthotroic, thought to b caud in o way by th rcoating roc. Howvr, a it i th intnti to u th SLS art for odlling tructur rforing in th latic rgi, thi i cidrd of low iortanc. In co with th uual dfiniti of th riary atrial ax in a unidirctial fibr rinforcd cooit (anothr tranvrly iotroic atrial) [13], th atrial 1-dircti i to b cidrd aralll to th SLS aaratu z-axi (th n-tranvr dircti; aralll to th fibr dircti in a cooit), with th 2- and 3- dircti bing intrchangabl and aralll to th SLS aaratu x- and y-dircti. Thi aignnt of riary atrial ax allow th orthotroy of th atrial O 12 to b dtrind, with Tabl 1: th dirctial rorti of DuraFor GF, including global an rorti and tho quotd by th anufacturr. BUILD 1 BUILD 2 E / GPa σ UTS / MPa x-dirn MEAN tandard dviati y-dirn MEAN tandard dviati z-dirn MEAN tandard dviati z-dirn (agd) MEAN tandard dviati x-dirn MEAN tandard dviati y-dirn MEAN tandard dviati z-dirn MEAN tandard dviati ε f O 12 E1 = 1 E 2 (3-1) GLOBAL UN-AGED MEAN MANUFACTURER S QUOTED [7] whr E 1 i th Young odulu in th 1-dircti, and E 2 th Young odulu in th 2-dircti (idntical to that in th 3-dircti for tranvrly iotroic atrial). Thu, ot unidirctial fibr rinforcd cooit atrial will dilay oitiv orthotroy, whra DuraFor GF dilay orthotroy of -.15 (or -1.5%) and -.11 (or -1.1%) for build 1 and 2 rctivly (taking E 2 to b th an of th horiztal Young oduli). It i alo clar fro figur 3 and tabl 1 that th ag of th cin ha an iact th rforanc of th atrial, with rducti of 21% and 44% in Young odulu and ultiat tnil trngth and an incra of 7% in train to failur aftr 43 day in abint cditi. Subqunt work, roritary of th ALM Grou at Airbu, ha hown thi aging to b du to oitur aborti and ay b coltly rovd by toring cin in a dry nvirnt. Significant variati in th atrial rorti fro build-to-build ay alo b obrvd, with an avrag rducti in all rorti of 1% fro build 1 to build 2. No chang wr ad to th roc aratr ud to crat build 1 and 2, howvr, in th intrvning riod routin aintnanc wa carrid out th aaratu. Th larg variati in atrial rorti caud by th aintnanc rocdur how th uctibility of roc outut to vn all chang in inut, a ud xtnivly to otii th SLS roc by tatitical thod [14-18]. Bcau th rorti of th atrial roducd by SLS ar likly to drift ovr ti, it i rquird to roduc and tt a all run of dogb (3 in ach of th x-, y- and z-dircti) with ach build ctaining odl for xrintal tructural analyi. Howvr, in ordr that nurical tudi of th ditorti rror caud by uing tructural odl ad fro DuraFor GF could b coltd, it wa ncary to choo t of rorti to rrnt th SLS atrial. It wa dcidd to u th rorti dtrind fro build 2, a it wa ly in build 2 that th har oduli of th atrial wr alo dtrind. Thu, th colt t of latic atrial rorti for DuraFor GF ud for th raindr of th tudi wa:

5 E 1 = 3.9 GPa E2 = E3 = 4.3 GPa G12 = G13 = 1.3 GPa (3-2) G 23 = 1.6 GPa ν = ν = ν = DISTORTION ERRORS AROUND HOLES IN PLATES A finit lat with a hol in tni rrnt a ilificati of a larg rang of tructural fatur. In ordr to dtrin th uitability of SLS to accuratly odl uch fatur in atrial aud to b iotroic, th ffct of variou lvl of orthotroy O 12, fro (iotroic) to.4 (4%), th axiu v Mi quivalnt train in th lat hown in figur 4 wa dtrind by finit lnt analyi. Th hol diatr to lat width ratio a/w wa varid fro to.725. Th atrial off-axi angl θ, th angl btwn th loading dircti and th atrial 1-dircti, wa alo varid, btwn and 9. Th odlling ditorti rror D (th dviati fro th iotroic rototy rult) for any givn orthotroic (odl) ca wa dfind a D ε ε ε 2, VM,ax 1, VM,ax = (4-1) 1, VM,ax whr ε 2,VM,ax wa th axiu v Mi train in an orthotroic (odl) lat, and ε 1,VM,ax th quivalnt rult for th iotroic (rototy) ca. E 1 wa aintaind ctant at 74 GPa, with E 2 and E 3 (th through-thickn Young odulu) bing varid according to th orthotroy for any givn ca. Poi ratio and har odulu in all lan wr aintaind a.3 and 28.5 GPa rctivly. Th atrial rorti thu dfind rrnt an idalid for of odl orthotroy, xrd ly in dirctial Young oduli, with th rototy ca bing a lat ctructd fro iotroic aluiniu alloy 224 (alu-224). Figur 4: th hol-in-lat cin, alo howing th atrial off-axi angl θ. It wa found that th odlling ditorti rror D varid aroxiatly linarly with O 12 for all valu of θ and a/w (xal givn in figur 5), which allowd th ndinial cific odlling ditorti rror d to b dfind a D d = (4-2) O 12 Th cific odlling rror d wa thn lottd againt th atrial off-axi angl θ for all valu of a/w. It wa found that for all valu of a/w, th variati of d with θ followd th a aroxiat for (hown a th dahd lin in figur 6 for a/w =.5,.35 and.725), with axiu cific ditorti rror occurring at θ = 9. Th axiu cific ditorti rror for any θ could thn b lottd againt a/w (figur 7). A lot of thi for would allow th xrintal analyt to dtrin th axiu ditorti rror that would b xctd fro odlling an iotroic rototy lat uing an orthotroic odl with O orthotroy (a/w)=.5 (a/w)=.375 (a/w)= % ditorti rror Figur 5: howing th linar variati of ditorti rror with orthotroy for thr lat gotri, with atrial off-axi angl θ = 9. All hol iz and off-axi angl howd a iilarly linar variati u to O 12 =.4.

6 cific ditorti rror, d (a/w) =.5, DuraFor GF (a/w) =.35, DuraFor GF (a/w) =.725, DuraFor GF (a/w) =.5, idalid orthotroy (a/w) =.35, idalid orthotroy (a/w) =.725, idalid orthotroy d (ax) thta / dg a/w Figur 6: howing variati of cific ditorti rror with off-axi angl for thr lat gotri. Includ rult for idalid orthotroy (orthotroy xrd ly in th Young odulu), and for th colt dirctial rorti of DuraFor GF It ay b n fro figur 7 that for DuraFor GF, with O , th axiu ditorti rror D that would b xctd whn odlling an iotroic lat i around -7% (th axiu train in odl would b 7% lowr than in rototy). Thi ditorti rror i cidrd to b within th bound of noral xrintal rror. Siilar nurical analy wr thn carrid out uing th colt SLS atrial data dtrind rviouly. For th ca, ε VM,ax for DuraFor GF (th odl) wa coard with that for th iotroic alu-224 (th rototy), with th odl tnil load bing cald by a factor 1/S E =.52 (th ratio of E 1 for DuraFor GF, 3.9 GPa, to th Young odulu for alu- 224, 74 GPa). Th rult ar hown a th olid lin figur 6, and it ay b n that ditorti rror fro th idalid orthotroic odl ar, in all ca, gratr than tho fro th DuraFor GF odl. 1t rincial train, FEA 2nd rincial train, FEA 1t rincial train, xrintal 2nd rincial train, xrintal ditanc fro hol cntr / Figur 7: howing th variati of axiu cific ditorti rror (for all θ) with lat gotry, for lat with idalid orthotroy (orthotroy xrd ly in Young odulu). For DuraFor GF, O , axiu ditorti rror D = -7% train In ordr to validat th finit lnt analy ud, thr hol-in-lat cin wr cratd by SLS, gotrically cald by th factor S w Figur 8: validati of th hol-in-lat FEA. Showing 1 t and 2 nd rincial train alg th trant A A, dtrind by finit lnt analyi and xrint (DIC), for S w =.8, a/w =.28, θ =.

7 =.8,.5 and.3. Th hol diatr to lat width ratio a/w wr t to.28,.75 and.5, and th atrial off-axi angl θ to, 45 and 9, rctivly. A grou of 9 dogb tnil cin wa alo roducd in th a build a th lat, with 3 dogb roducd aralll to ach of th riary atrial ax. Each odl wa loadd in tni to failur, with th train fild bing dtrind by 3-dinial digital iag corrlati (DIC) at variou intrvning load. Th 1 t and 2 nd rincial train alg th trant A A (figur 4) wr thn lottd for th DIC (xrintal) and corrding FEA (nurical) analy (xal hown a figur 8 for S w =.8, a/w =.28, θ = ). Th nurical analy ud atrial rorti dtrind fro th 9 tnil dogb roducd with th lat. Clo corrlati wa notd btwn th nurical and xrintal rult. 5. MODELLING REINFORCED COMPRESSION PANELS Th buckling bhaviour of rinforcd anl i of articular intrt to th aroac ctor, a uch of th tructur of an aircraft ay b cidrd to b a or colx for of a il rinforcd cori anl. Howvr, th buckling and ot-buckling bhaviour of vn il rinforcd anl tructur i xtrly colx [19] and a uch, a rquirnt to rfor xrintal analy of th tructur xit for both aircraft dign and for or cific rarch tudi. Th ability of SLS to raidly and accuratly roduc odl of cori anl i thrfor of ccrn to th currnt tudy. Th anl that wa cidrd for analyi i hown a figur 9. Th nd of th anl wr ctraind to iulat a builtin nd cditi. An ignvalu finit lnt analyi of th anl wa coltd in ordr to find th aroxiat critical buckling load P cr,1 for an iotroic aluiniu alloy 224 rototy anl (E = 74 GPa, Poi ratio ν =.3). Siilar analy wr thn coltd uing th atrial rorti dtrind rviouly for DuraFor GF, with th critical odl buckling load thn cald by th ratio of th Young odulu for alu-224 to E 1 for DuraFor GF (S E = 19.2). Th atrial off-axi angl θ (th angl btwn th loading dircti and th atrial 1-axi, in th lan of th lat) wa again varid fro to 9. Th ditorti rror D wa dfind a D P P Figur 9: th rinforcd cori anl cin, howing th atrial off-axi angl θ, and th tiffnr and lat cont of th anl. cr,2 cr,1 = (4-1) Pcr,1 whr P cr,2 i th buckling load rdictd for th iotroic alu-224 rototy anl by th cald DuraFor GF odl. Figur 1 how th variati of th ditorti rror in critical load (xrd a a rcntag) with th atrial off-axi angl for th rinforcd anl. It ay b n that th axiu ditorti rror whn odlling th rototy anl with DuraFor GF i l than 7%. Again, thi ditorti rror i cidrd to b within th liit of noral xrintal rror. In ordr to validat th rult, a ri of anl at variou cal and atrial off-axi angl wa roducd. Howvr, th ridual tr cratd in cont built by SLS nur that th roc i n-otial for accuratly roducing % ditorti rror thta / dg Figur 1: howing th variati of ditorti rror with atrial off-axi angl for a DuraFor GF anl, dtrind by finit lnt analyi.

8 larg flat lat. Thi i articularly tru whn uch lat hav fatur of diffrnt thickn attachd to th, uch a th tiffnr of th rinforcd anl. All of th anl roducd thu far hav ctaind cidrabl lvl of war roval fro th build volu, lading to th to and botto dg of th lat bing n-aralll to anothr (th anl twitd about th axi of loading). Annaling th anl at a tratur of 75 C for 1 hour rovidd th oluti to a ignificant xtnt; howvr, anl tratd in thi annr till Figur 11 (clockwi, fro abov): buckling attrn of anl (θ = ) at th critical load, fro xrint; th xrintal t-u, howing buckling anl hld in gri (alo roducd by SLS) and th loading rig; and buckling attrn of corrding anl dtrind by ignvalu finit lnt analyi. Vry littl agrnt btwn th buckling attrn fro xrint and fro FEA i vidnt. ctaind initial irfcti larg nough to cau unxctd attrn of buckling during cori tt (figur 11). 6. DISCUSSION, OR THE ART OF PRODUCING SCALED MODELS BY SLS Th ditorti rror caud by th orthotroy of DuraFor GF hav bn hown by finit lnt tudi to b within th bound of noral xrintal rror, cidrd to b around 1%, whn odlling iotroic rototy hol in finit lat in tni and rinforcd buckling anl. It i thought that iilar lvl of ditorti rror would xit for th odlling of othr iotroic rototy tructur. In thory, thrfor, it i oibl to roduc, by SLS, cald odl of tructural rototy for u in xrintal validati of finit lnt analy. Howvr, cidring ly th latic orthotroy of th SLS atrial ignor a nubr of othr ccrn in th roducti of accurat odl. Th ccrn includ th n-linarity of th SLS atrial and th dinial accuracy of odl roducd by SLS: clarly, diffrnc in th bhaviour of DuraFor GF to whatvr atrial it i aiing to iitat, and any diffrnc in th ha of a odl to that of th rototy, will lad to furthr ditorti rror in th analyi. If it i aud that th finit lnt analyi to b validatd i ly ccrnd with latic bhaviour, and again uing aluiniu alloy 224 a th odlld atrial, it ay b hown that th n-linarity of th SLS atrial will hav littl ffct th xrintal analyi. Th Young odulu cal factor S E, th ratio of th Young odulu of th rototy atrial (alu-224) to that of th odl atrial (DuraFor GF), i If th rototy includd ak tr σ ax,1 qual to th yild tr of alu-224, around 23 MPa, th quivalnt ak tr in th DuraFor GF odl σ ax,2 would b σ ax,2 1 = σ = 12. MPa (5-1) S E ax,1

9 It ay b n fro figur 3 that th axiu tr in th odl would thrfor b wll within th linar rgi of un-agd DuraFor GF, and thu no ditorti rror would b caud by th n-linar bhaviour of th atrial in th ca. Th difficulti in roducing dinially accurat cald odl of crtain for by SLS ar, unfortunatly, hardr to ovrco. Larg flat lat of th ty of for found xtnivly in lightwight tructur uch a aircraft ar articularly difficult to roduc accuratly, although any tructur ay rnt robl cific to it ha. Th lo of dinial accuracy ar caud by th hrinkag of th atrial during intring and thn cooling, lading to ridual tr and ditorti [1]. Rducing uch ditorti i no an fat: th SLS roc ha or than 5 inut aratr which ay affct th outut of th roc, fro layr thickn and lar ba d to hatch acing and art bd tratur, any of which intract in colx annr [17]. Th rci annr in which th roc aratr affct outut ar till oorly undrtood, and a a rult orator xrinc i invaluabl whn attting to build accurat art. Achiving citntly high-quality odl in any ALM roc i oftn dcribd a or of an art than a cinc by xrincd ur. It i likly that difficulti in roducing uitably accurat art will b th ajor liitati in uing SLS to roduc tructural odl of crtain ty. It wa hown that it i oibl to rduc th war of art by annaling, howvr lvl of ditorti larg nough to affct th xrintal analy till raind. Alo, th nd to colt cdary roc to rar a odl for analyi rov o of th attracti of ALM for roducing tructural odl in th firt lac. Thr ay b othr way around thi robl, though: initial attt to build uch allr cal vri of th rinforcd cori anl (S w =.5) hav t with or ucc. Th allr art dilay cidrably l waring and achiv bttr dinial accuracy than thir largr countrart. Howvr, at iz uch a thi th thickn of th lat i of a iilar ordr to th lar ba diatr, and aroaching that of th layr thickn. It i unknown if thi will hav a dtrintal ffct th accuracy of th odl, and to what lvl uch gotric caling ay b takn whilt aintaining accuracy. Th futur ccrn of th tudy will includ invtigati th liit of gotric caling, and SLS roc aratr otiiati to furthr rduc orthotroy and irov dinial accuracy. 7. CONCLUSIONS A tudy of th uitability of uing th SLS roc and DuraFor GF to roduc cald tructural odl for validati of FEA i -going. Currntly, th following cclui ay b drawn: o DuraFor GF whn rocd by SLS i tranvrly iotroic, with Young odulu in th 2- and 3- dircti bing around 1% gratr than in th 1-dircti. Th atrial 1-dircti i aralll to th SLS aaratu z-dircti. Th atrial dgrad with ag du to oitur aborti, with a rducti in Young odulu and ultiat tnil trngth of around 2% and 45% rctivly aftr 43 day tord in abint cditi. o Th atrial rorti of Durafor GF ak it uitabl for th roducti of tructural odl, with ditorti rror caud by orthotroy of l than 1%. o Th difficulti of roducing dinially accurat art by SLS i likly to b th ajor liiting factor uing th roc to roduc tructural odl, although attt ar to b ad to rduc lvl of war in art to uitabl lvl. 8. REFERENCES 1. Cook R D, Malku D S, Plha M E, Witt R J, Cct and Alicati of Finit Elnt Analyi (4th diti), John Wily & S, Nw York, Ld, O'Brin E W, Pr-tt analyi uing trolithograhy and hotolatic coating, Procding of th 25 SEM Annual Cfrnc and Exoiti Exrintal and Alid Mchanic, Portland, OR, Unitd Stat,. 1631, Jacob P F, Strolithograhy and othr RP&M Tchnologi, Arican Socity of Mchanical Enginr (ASME) Pr, Nw York, Bourll D L, Marcu H L, Barlow J W, Baan J J, Slctiv lar intring of tal and craic, Intrnatial Journal of Powdr Mtallurgy, vol. 28 (4), , 1992.

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