Differentiable Distance Spaces.pdf

19th cirp international conference on life cycle engineering, berkeley, 2012 material substitution for automotive applications: a comparative life cycle analysis laura marretta1, rosa di lorenzo1, fabrizio micari1, jorge arinez2, and david dornfeld3 1 dipartimento di ingegneria gestionale, chimica, informatica e meccanica, university of palermo, italy 2 manufacturing systems research laboratory, general motors r steel; automotive life cycle; recycling 1 introduction recently, environmental considerations in manufacturing have become increasingly important as many industries seek to develop sustainable solutions for industrial applications. in particular, a strong interest towards low environmental impact solutions and technologies has arisen in the automotive industry 1, 2. transportation in general represents 27% of the global us emissions by economic sector, where the specific contribution from light duty vehicles is as high as 59% among all the transportation modes 3. moreover, the use phase has the greatest impact throughout a typical vehicle life cycle 4. lightweight materials and the necessary manufacturing processes and technologies to produce them have become one of the most important strategies to improve the overall “eco-efficiency” in automotive applications, for example 9 g of carbon emissions might be saved per km by reducing the vehicle weight by 100 kg 5. in this paper, we use the term “eco-efficiency” as coined by the world business council for sustainable development (wbcsd) 6 which defines the idea of producing goods and services at a lower consumption of resources and correspondingly lower amounts of waste and pollution. lightweight manufacturing technologies may enable the capability to draw thinner blanks by smoother deformations, even while using low formability materials. hydroforming, superplastic and incremental forming may therefore allow significant weight reductions over conventional stamping technologies 7. hot stamping has also been performed to enhance formability of automotive materials to get lighter components 8. moreover, innovative solutions as using tailored blanks have been widely employed to intelligently place mechanical properties by hybrid materials or thickness through an automotive part 9. beside lightweight technologies, low density materials enable a significant weight reduction, leveraging lower consumptions in the use phase of a vehicle life cycle. currently, magnesium alloys 10, titanium alloys 11, and in particular advanced high strength steels (ahss) and aluminum alloys are of interest for the transportation industry due to their high fuel saving potential 5, 10, 12, 13, 14. a 6% to 8% fuel savings can be realized for every 10% reduction in weight from substituting steel with aluminum and each kg of aluminum replacing 2 kg of steel will save 20 kg of co2 over the typical life time of a vehicle 7. for design equivalence, the thickness ratio between aluminum and traditional steel blanks for structural applications may be approximately 1.5, but the weight reduction would still be about 50% 15. despite these differing attributes, the eco-efficiency of any material or technology ought to be analyzed over an entire life cycle, as each phase is sometimes characterized by significantly different environmental impact: saving fuel in the use phase, and accordingly greenhouse gases emissions, may mean for instance increase the environmental effect from manufacturing or material acquisition. for example, aluminum alloys provide lightweight benefits the use phase in automotive applications, aluminum possesses requires relatively large amounts of energy for raw material extraction and processing. to produce 1 ton of aluminium 1.9 tons of alumina are required which means in turn 4.2 tons of bauxite and 13,000-18,000 kwh/ton aluminium produced 4. in 16 a life cycle assessment of an australian automotive component details higher aluminium energy consumption, global warming potential (gwp), and acidification potential (ap) in the production phase with respect to other automotive materials. similar results are reported in 7. furthermore, higher manufacturing energy is consumed compared to traditional steels due to their formability issues 17. a cradle-to-grave life cycle analysis is then useful to map the eco-efficiency of using aluminum alloys instead of traditional automotive materials to evaluate if indeed there is an advantage when all the life cycle factors of aluminum components are considered. in this paper, a life cycle analysis is proposed to compare the use of the aa5250 alloy and a draw quality (dq) steel for automotive applications (using gabi4 18). a cradle-to-grave analysis was carried out and the environmental impact was broken down by phases. mapping both material life cycles by environmental impact is then possible thereby addressing improvement directions and highlighting possible strategies in the use of such light weight alloys. the aluminum leveraging effect through the component life cycle was calculated as incremental greenhouse gases per life cycle phase comparing aluminum over steel. moreover, as suggested by the first cradle-to-grave analysis, a recycling strategy was considered as a possible scenario in the aluminum lifecycle. aluminum is a highly recyclable with secondary and primary aluminum having the same properties. the content of recycled aluminum in body-in-white 62 app use cou pro hig 2 the ide bou ass suc a c the com ext use ana and and tab by ste acc low tho low req occ wh alu add ste sof life par dep the mo for ga dis sce dat the foll sum 200 plications is still ed for automotive uld effectively le oduct use phase h initial processi comparativ e first important ntification of the undaries that de sessment, differe ch as cradle-to-g comparison betw eir life cycle is mponents life cy traction, primary e phase and re alysis of two dif d a hood (figure d the aa5052 alu figure 1: cad ble 1 reports eac material 17. in el it is possible to cordingly, a mor wer weight implie ough aluminum h wer strain harden quired to get th curs in general, hen compared to minum fender a ds +15 kwh/ve ps required to m ftware gabi4 was cycle of each rticular, as the pendent, the pow erefore the avera oreover, only the in the use phase soline was cons tance of 200,0 enarios were not ta were weighte e lcia (life c owing impact ca mmed to obtain 01 eco-score: a 0%-11% while e components 8 everage aluminu and improve its ng energy requir ve cradle-to- step of any life goal of the stud etermine its sco ent classification gate, gate-to-gate ween two differen sought. in thi ycle are account y shaping proce cycling are all i fferent automotiv e 1). a draw qua uminum alloy (aa d model of the an ch components particular, by us o save up to the re efficient use es less input m has lower yield s ning exponent oft he same shape which increases traditional autom dds +10 kwh/v ehicle. namely, manufacture the s used to evaluat component by environmental wer grid location age u.s. power weight induced e of the investiga sidered as fuel, f 000 km (55% c considered in th ed and normalize cycle impact a ategories were a global enviro abiotic depletion about 15% of s 8. an extensive ums low-weight s eco-efficiency rements. -grave analy e cycle assessm dy and the definit ope. based on t ns of life cycle a e, to name a cou t automotive ma is manner, all ted for. in partic esses, manufact included within ve components, ality cold rolled c a) were evaluate nalyzed automotiv weight and man sing aluminum in 40% of weight ( of raw material aterial. on the strength than tra ten increases the . in addition, h s its forming ene motive materials, vehicle, while th such energy ac e same final geo te the environme y the two differ impact from en n was specified grid source mix fuel consumptio ated components for the commonly city / 45% hig he present analys ed in gabi by us assessment) me considered indiv onmental score n (adp kg sb- secondary steel recycling strateg attributes in th and overcome it ysis ment (lca) is th tion of the system the scope of th assessment resu uple. in this pape aterials throughou phases of eac ular, raw materia turing processes a cradle-to-grav namely a fende carbon steel (dq ed in this analysis ve parts 17. nufacturing energ n lieu of traditiona %). is achievable a other hand, eve aditional steels, it e number of shot higher springbac rgy requirements , the design of th e aluminum hoo ccounts for all th ometry. the lc ental impact of th rent materials. i nergy is locatio to be in the us x was considered on was accounte s according to 9 y used life drivin hway) 9 (othe sis). sing cml2001 a ethod. thus, th vidually and the referred as cm eq), acidificatio is gy he ts he m he ult er, ut ch al s, ve er q) s. gy al as en ts ts ck s. he od he ca he in on s, d. ed 9. ng er as he en ml on potential ( phosphate- eq), ozone eq), photo eq). in part integrates a weight kg mfg. energy mj tab the enviro neglected h be used. s material sub a different s over the cha 2.1 aa50 a diagram in figure 2, study. sinc the entire li to-grave an fi the percen impact cate proportions well (percen figure 3: 0.0 (ap kg so2-e -eq), global wa e layer depletio ochemical ozone ticular, the cml all the above men h aa d 10.57 17 126 7 ble 1: input mate onmental impact here, as the sam uch assumption bstitution is hypo setting of the pro ange of the man 052 aluminum c of the gabi mod which is the sam ce aluminum pri fe cycle invento alysis igure 2: gabi mo ntage contributio egory is shown in on average wer ntages are from n environmental im 5% 14.62% 52.89% eq), eutrophica rming potential ( on potential (od e creation pote 2001 eco-score ntioned impact c ood dq % 7.75 -40% 72 +75% rial and energy r t from dies an me manufacturing is justified by th othesized in a ma ocess paramete ufacturing system case study del for the alumin me for both the h mary production ry was therefore odel of the alumin ons to the enviro figure 3 for the re observed for t normalized and w mpact breakdown a (a e ( g p y o p p c ( 10.76% 10.37% 11.31% l. marr ation potential (gwp 100 years dp, steady state ntial (pocp kg is a synthetic ind ategories. fender aa dq 2.82 4.26 82.8 46.8 requirements 17 nd tooling syste g system was as he consideration anufacturing env rs/steps may be m. num case study hood and the fen n is a long proce e included in suc num case study. onmental impact hood alone, but he fender compo weighted data). n from aluminum acidification potential ap) eutrophication potentia ep) global warming potential (gwp 100 years) ozone layer depletion potential (odp) photochem, ozone creation potential pocp) retta et al. (ep kg s kg co2- kg r11- g ethene- dex which % -35% +77% 7. ems was sumed to n that if a ironment, e possible is shown nder case ess chain, ch cradle- t of each the same onents as m usage. al n ma glo cor em 0.3 cat t to a b sum allo the and from crit aim in pur form the by and ins allo sta form with the use pro tho aterial substitutio obal warming rresponds to 53% missions, while, fo 31 kg phosphat tegories are repo impact catego adp kg sb-eq ap kg so2-eq ep kg phospha gwp kg co2-e odp kg r11-eq pocp kg ethe table 2: emission address strateg breakdown by lif mmarizes the e owing further disc figure 4: alu e total impact fro d 2.3e-10 for the m the raw mate tical one, followe med to improve th order to reduce rpose, non con mability of alum e same time 19. smoother mecha d allowing the us tance, incremen ow material savi mping technolo ming processes h traditional dee e energy required ed in primary omising energy s ough the fender is p 0e+00 cml2001 eco s hood fender hood mat product proce fender 2 cml 2001 e 0e+00 on for automotive potential is % of the total we or instance, eutr te-eq. the det orted in table 2. ory (cml2001) ate-eq eq q ne-eq ns of aluminum c ies in material u fe cycle phases environmental im cussion. minums cml ec om aluminum usa e fender case st rial extraction an ed by the use p he efficiency in m e the consumptio nventional stamp inum alloys whil a more efficient anical deformatio se of thinner blan ntal forming proc ings of up to 10 ogies 20. hyd 22 allow using ep drawing opera d by aluminum r production and saving scenario f s four times light material production and processing 2e-103e-10 score mate use eol terial tion and essing 2e+00 eco score 3e+00 mfg e applications: a noteworthy as eighted and norm rophication poten ailed emissions hood 1.58 1.47 0.308 275 4.5e-006 0.304 components by im sage for automo s provides more mpact of the tw co-score by life c age is about 7.5 tudy, but in any nd processing is phase. it sugges material use sho on of input mat ping technologie le performing we t use of material ons enabled by s nks for a given fi cesses of alumi 0% when compa roforming 21 g thinner blanks ations. it bears c recycling is muc processing an for aluminum usa ter than the hood mftus 5e-10 material production mft use eol erial production an usmfg 05e+006 comparative lif s 275 kgco2e malized aluminum ntial is as high a s calculations b fender 0.479 0.46 0.0849 83.8 2.35e-006 0.0849 mpact category. otive components insight: figure wo vehicle part cycle phase. e-10 for the hoo case, the impac s indeed the mos sts that strategie ould be addresse terial. for such es may increas eight reduction a could be pursue such technologie nal geometry. fo num component ared to traditiona and superplast s when compare consideration tha ch lower than tha nd thus yields age. finally, eve d, the difference seeol 6e-108e-10 n and processing nd processing eolse 6e+00 8e+00 fe cycle analysis eq m as by s, 4 ts od ct st es ed a se at ed es or ts al ic ed at at a en in terms of remarkable 2.2 draw figure 5 sh proportions observed a simply show are reported figure 6 impact adp kg ap kg s ep kg p gwp k odp kg pocp table 3 an overview figure 7 (d to significa primary pro significant s heavily con therefore, strategy tow applications to carry out cycle. more primary pro 0,06 s environmental i . w quality (dq) c hows the gabi m amongst the again between th ws the results of d in table 3. figure 5: gabi m 6: environmenta category (cml g sb-eq so2-eq phosphate-eq kg co2-eq g r11-eq kg ethene-eq 3: emissions of s w of steel emis ifferent axis scal ntly different we oduction of alu source of emissi ntributes to thei while efficiency wards a more su s, weight reductio for steel compo eover, impact fr oduction. 11 48% % 19% impact from m old rolled carb model for the dq emissions cate he steel hood an f the hood case model of the stee al impact breakdo l2001) ho 1.3 0.5 0.4 21 2.86e 0.3 steel components ssions by life cy les are necessar eight of the two minum compon ions, the use ph ir cradle-to-grav in material use stainable use of on seems to be t nents with lower rom steel recyc % 5% 17% acid eutr (ep glo (gw ozo pote pho cre manufacturing is bon steel case s steel case stud egories by impa nd fender. thus, study. emission el case study. own from steel us ood fen 32 0.3 513 0.1 436 0.1 10 56 e-006 1.36e 363 0.08 s by impact categ ycle phases is ry in figures 4 a components). w ents result in t hase of steel com ve environmenta e seems to be f aluminum for au the most promisi environmental im ling is about 23 dification potential (a rophication potential p) bal warming potenti wp 100 years) one layer depletion ential (odp) otochem, ozone ation potential (poc 63 s not as study y. similar act were figure 6 ns details sage. der 352 64 06 6.7 e-006 894 gory. shown in and 7 due while the the most mponents al impact. the best utomotive ing action mpact life 3% of its ap) l ial cp) 64 l. marretta et al. figure 7: steels cml eco-score by life cycle phase. it has been observed that the usage of advanced high strength steel (ahss) in automotive applications allows production of even 25% lighter automotive steel components 8. by combining good formability features with good mechanical properties, as with ahss, it is possible to manufacture thinner blanks for a given final geometry while satisfying necessary performance requirements. 3 comparison of the results the comparison of the cml eco-score between aluminum and steel components is reported by life cycle phase in figures 8 and 9, respectively for the hood and the fender case studies (different axis scales are necessary due to significantly different weight of the two components). figure 8: comparison of the results (hood case study). figure 9: comparison of the results (fender case study). these results indicate that aluminum, either in the hood or the fender case study, has globally higher environmental impact than steel. while the total environmental impact from steel usage is respectively 6.5e-10 and 1.7e-10 for the hood and the fender case studies, aluminums impact is 7.5e-10 for the hood and 2.3e-10 for the fender. also, despite enabling a significant lowering of the environmental burden in the use phase, the impact from aluminum primary production and manufacturing phase negatively balances such advantages as fuel saving. to better understand how significant the advantage or disadvantage of using aluminum might be, a leverage effect index (le %) was formulated as follows: 100* impact(aa) impact(aa)impact(dq) le = (1) this le index effectively quantifies the potential reduction (if positive) or increase (if negative) in the total emissions of each life cycle phase, which relates to the usage of aluminum alloy over traditional draw quality steel to the manufacture of a given automotive component. figure 10 shows the leverage effect enabled by aluminum usage in both the automotive applications. figure 10: leverage effect by alumi