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Reduction of Die Wear and Structural Defects of Railway Screw Spike Heads Estimated by FEM



Jackeline Alcázar 1, Germán Abate 1,2, Nazareno Antunez 1,2, Alejandro Simoncelli 1,2, Antonio J. Sánchez Egea 3 , Daniel Martinez Krahmer 1,2 and Norberto López de Lacalle 4,*



1 Faculty of Engineering, Universidad Nacional de Lomas de Zamora, Juan XXIII y Camino de Cintura, Buenos Aires 1832, Argentina; jalcazar@ingenieria.unlz.edu.ar (J.A.); gabate@inti.gob.ar (G.A.); nantunez@inti.gob.ar (N.A.); asimoncelli@inti.gob.ar (A.S.); dmartinez@inti.gob.ar (D.M.K.)

2 Center for Research and Development in Mechanics, National Institute of Industrial Technology (INTI), Avenida General Paz 5445, Buenos Aires 1650, Argentina

3 Department of Mechanical Engineering (EEBE), Universitat Politècnica de Catalunya, Av. D’Eduard Maristany, 16, 08019 Barcelona, Spain; antonio.egea@upc.edu

4 Department of Mechanical Engineering, University of the Basque Country, Escuela Superior de Ingenieros Alameda de Urquijo s/n., 48013 Bilbao, Spain

* Correspondence: norberto.lzlacalle@ehu.eus



Citation: Alcázar, J.; Abate, G.; Antunez, N.; Simoncelli, A.; Egea, A.J.S.; Krahmer, D.M.; López de Lacalle, N. Reduction of Die Wear and Structural Defects of Railway Screw Spike Heads Estimated by FEM. Metals 2021, 11, 1834. https://doi.org/10.3390/ met11111834

Academic Editors: Koh-ichi Sugimoto and Badis Haddag

Received: 26 September 2021 Accepted: 12 November 2021 Published: 15 November 2021



Abstract: Railway spike screws are manufactured by hot forging on a massive scale, due to each kilometer of railway track needing 8600 spike screws. These components have a low market value, so the head must be formed in a single die stroke. The service life of the dies is directly related to the amount of energy required to form a single screw. The existing standard for spike screws specifies only the required tolerances for the head dimensions, particularly the angle of the hub faces and the radius of agreement of the hub with the cap. Both geometrical variables of the head and process conditions (as-received material diameter and flash thickness) are critical parameters in spike production. This work focuses on minimizing the energy required for forming the head of a railway spike screw by computational simulation. The variables with the highest degree of incidence on the energy, forging load, and filling of the die are ordered statistically. The results show that flash thickness is the variable with the most significant influence on forming energy and forming load, as well as on die filling. Specifically, the minimum forming energy was obtained for combining of a hub wall angle of 1.3◦ an as-received material diameter of 23.54 mm and a flash thickness of 2.25 mm. Flash thickness generates a lack of filling at the top vertices of the hub, although this defect does not affect the functionality of the part or its serviceability. Finally, the wear is mainly concentrated on the die splice radii, where the highest contact pressure is concentrated according to the computational simulation results.

Keywords: screw spike; hot forging; die wear; defects; computational simulation



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1. Introduction

The railway transport system is one of the main transport systems used worldwide, and railways transport both people and cargo. Its importance is due to its strong influence on many countries’ social, economic, and industrial development [1]. Many components of the railway system require forging, such as railway wheels, axles, crankshafts, large and small connecting rods, disk brakes, chassis components, connection couplings, and sleeper screws [2]. These parts require superior strength and toughness [3], given their demanding service conditions. A critical component of the railway track is spike screws. These parts are mass-produced because 8600 of them are used for each kilometer of track [4]. These components are manufactured by forging, which involves a press [5], dies [6], and a lubrication system [7].

The spike screws connect the rails to the sleepers and, together with the pads, elastic clips and guide plates constitute the fastening system [8]. The spike screw links the parts



Metals 2021, 11, 1834. https://doi.org/10.3390/met11111834



https://www.mdpi.com/journal/metals



Metals 2021, 11, 1834



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of the track and has a safety aspect since the failure of these parts in service conditions can cause accidents. These failures, caused mainly by the spike screw fracture, can result from over-tightening, under-tightening, or fatigue [9]. Faria et al. [9] studied the spike screws commonly used by the Brazilian railway sector due to their recurrent failures of these parts during service conditions. A computational simulation helps to propose screw spikes geometries modifications that can result in improved theoretical fatigue resistance. Moreover, Moreira et al. [4] deployed experimental tests and computational simulation intending to improve the screw behavior in fatigue conditions, proposing changes in the material and the thermal treatments of the spike screws. The spike screws are manufactured in two steps, firstly by heating one part of the blank to forge the head of the screw. Then, the other part is heated to create the thread by rolling using three dies. It is a standard procedure used by the forging industry in Argentina [10]. Some tests have been done by heating both sides of the blank and forming the two sides of spike screws simultaneously, thus increasing productivity. For example, Gontarz et al. [11] developed a mechanical press that forges the head at each end of the blank (double configuration) and then synchronizes this equipment with a linear wedge forging machine that threads the body of both screws. In the end, that machine could manufacture two pieces at a time. Regarding the internal defects produced by the wedge forging machine, Van Hai and Hong Hue [12] studied a hot tapping process of AISI 1045 spike screws because their internal defects can significantly reduce their fatigue strength. They were able to reproduce the defects as mentioned above by computational simulation, a situation that enables them to carry out a future improvement on the design of mechanical testing of these components.

The energy consumption to form this kind of component directly impacts die wear [13]. It is one of the reasons why the blockers are used in forging processes [14,15]. However, blockers are not always possible to apply due to the low market price of these parts. Due to these limitations, different manufacturing options must be sought, like the one suggested by Hu et al. [16]. They proposed a multi-objective optimization approach on A309 aluminum alloy through the design of experiments, simulation and hydraulic press forming. They found that by combining the operational parameters, the lifespan of the dies could be increased by 23.5% compared to the original process condition. Additionally, replacing the forging dies significantly impacts the process costs, which can reach up to 30% [17]. In particular, wear is responsible for 70% of die failures during service conditions [18]. Many studies have focused on reducing the friction and wear conditions to increase the lifespan of the die. For example, Behrens et al. [19] studied the relationship between surface topography and wear. Accordingly, they fabricated a series of similar dies, whose final surfaces were obtained by turning, milling, and blasting. After forming 500 forged gearwheel specimens by each method, they determined that the slightest geometrical deviation was achieved with the milled die, while the most significant deviation occurred in the turned die [19]. Likewise, Krawczyk et al. [20] studied surface thermal softening in forging dies. They measured surface temperatures in the order of 600 ◦C, which produced a softening up to a depth of 0.3 mm. The thermal impact led to a decrease in the die hardness, which causes accelerated wear due to abrasion and plastic deformation.

The German company Hirschvogel [21], which specializes in the forging of parts for the automotive sector, details the reasons why it is very important to simulate forging processes: reducing the time of research and development, early detection of failure zones, a decrease of the cutting weight, a better understanding of the process, among others. In this way, the general procedure is to design the forging parts in CAD programs and then study the mechanical behavior with finite element simulation programs. The objective is to calibrate the process to reduce design failures or defects in the material due to excessive deformations. Once manufactured, the component’s mechanical properties are studied and its surface properties are analyzed by non-destructive testing to find cracks, folds, or other defects. In this sense, Prabhu et al. [22] analyzed forged parts for the aeronautical sector by combining simulation and experimental techniques to carry out its development. After producing parts with the adjusted process, they did not present surface defects and



Metals 2021, 11, 1834



other defects. In this sense, Prabhu et al. [22] analyzed forged parts for the aeronautical

sector by combining simulation and experimental techniques to carry out its development. After producing parts with the adjusted process, they did not present surface3 odfe1-1 fects and their mechanical properties were 10% higher than those specified in the technical

drawing. Additionally, Behrens and coworkers [23] developed a finite element model de-

stchreiibrinmgescchaalneibcaelhpavroioprertotiebsewinecroer1p0o%rahteidghinertothcaonmtmhoesrecisapl esociffitwedarienuthseedtetcohsnimicaulladtreatwhiensge. pArdodceitsisoensa,lglyi,vBeenhtrheensinafnludecnocweoorfksecrasl[e23fo] rdmevaetiloonpeodnafrfiinctitioenelaenmdenmt amteordiaell dfleoswcriibninfogrsgcianlge dbieehcaavviiotrietso. be incorporated into commercial software used to simulate these processes, givenGtehneerinalfllyu,etnhceevoaflsidcalteiofnoromf athtieonmoecnhfarnicitciaolnbaenhdavmioarteorfiacloflmopwoninenfotsrgininrgaidlwieacyavliintieess,. such Gasentheerasllpyi,ktehescvraelwidsa,trioeqnuoifreths ecommepchliaanniccealwbiethasvpioecriofifccroemguploantieonnts.iTnhreailewgaisylalitnioens, essutcahblaisshtehsethspeikneomscirneawl sd,imreeqnusiiroens scoamndpltioalnercaenwceitshfosrpethciefihcurbegaunlgalteio, nhsu.bTthoeclaepgirsaladtiiuosn, aenstdabthlieshsteasrtihnegnmomateinriaalld’simdieanmseiotenrs. Tanhde atoimleroafntcheis froersetahrechuisbtaondgele,phenubthteo hcaeapdrafodrimus-, ianngdptrhoecsetsasrbtiynghomt-aftoerrgiainl’sgdwiaitmheetxepr.eTrihmeeanimts toof dtheitseremseinaercthheisgtoeodmeeptreinc cthoemhbeinadatfiornmthinagt gpernoecreastsebs ythheolto-fworegsitnegnwerigtyh eaxnpdecriomrreenlatstetothdeectoernmtaicnteptrheessgueroems oetbrtiacincoedmbiynacotimonputhta-t

tgioenearlastiems uthlaetilown ewsittehnheirgghyearnwdecaorrarerelaatseatht ethceohnetaacdt opfretshseusrpesikoebstacirneewdsbmyecaosmurpeudtawtiiothnaal 3sDimsuclanti.oTnhweirtehfohrieg,htehriws weaorrakr’esaisnadtuthsterihaelaidntoefrethste isspiokpetismcriezwinsgmtehaesuenreedrgwyittho afo3rDmsctahne. hTehaedreofof rae,spthiiksewscorekw’s,inwdhuicshtriiaslainptreoredsut cist opf tloimwizminagrktheet venaleurgeydtuoefotormitsthmeahsesapdrofdauscptiiokne rsecqreuwir,ewmheincth. iIsnathpirsodseuncsteo, fitloiws pmosasrikbeltevtaoluperodduuecteosiatsfemraasils fparsotdenuecrtsiotnharetqcuoimrepmlyenwt.itIhn ctuhirsresnent sre,giut liastpioonsssiabnledtocapnrobdeufcoermsaefde rwailthfaastepnroercsestshatht acot mrepdluycwesitphrcoudrurectnitornegcouslatst,ioin-s carnedasceasnthbeelfiofermofetdhewditihesa, apnrodcreesdsuthceast erenderugcyescopnrosudmucptitoionnc. osts, increases the life of the dies, and reduces energy consumption.

2. Materials and Methods 2. Materials and Methods 22..11.. DDiimmeennssiioonnaannddTToolleerraanncceess ooff tthhee SSccrreeww SSppiikkee rL7raa0i7ill1rs20o.TT1aSTh2hdtihaisSsrniastwwdaiwlanoosrd.rordkTkarakrhaadfiiitfsmmeoawrcfssuthoettosororektasahffnonoooraatcnglluyfyianoszznergeegsattitlohhnyhneegzeihainitnnnehgflaafeldultuyhheoezenenfiacnfctdeohgereotoomhfsffpetithntihfhkegoeeertpotmssorclpoelireinreckragweeansnpsscscreucooesrsfsceepewtdphrserssefesooesuhrfensefntetaahtdsidentienf(htnoFhetriihaengdfeguIaRIrs(tRFehAteieA1MngarMuian-)rF.ig-elAFrTo1tTAhhaaiT)deLs. Tpharist cpaanrtbceadnibveiddeidviidnetodtiwntooptwarotsp: harutbs:ahnudbcaanpd. Tcahpe.sTtahnedsatradnidzaedrdmizeeadsumreeamseunretsmoefntthseosef tphaerstes opfatrhtse ohfeathdeahnedatdheainrdretshpeeicrtrivesepteocletirvaencteoslearraenscheoswarneisnhFoiwgunrein1bF,igeuxtrreac1tbe,defxrtormacttehde fIrRoAmMth-FeAITRALM7 -0F1A2 TStLan7d0a1r2d.Standard.



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CAD dCiAmDensdioimnse(nmsimo)ns (mm) 22–23



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Combining the two hub angles and the two hub and cap joint radii, four die geometries of the screw head can be obtained, as shown in Figure 2. These combinations required a dimensional increase of 1.4% of their cavities due to steel shrinkage [24]. The die for the bottom was the same in all cases.



Metals 2021, 11, 1834



Combining the two hub angles and the two hub and cap joint radii, four die geometries of the screw head can be obtained, as shown in Figure 2. These combinations required a dimensional increase of 1.4% of their cavities due to steel shrinkage [24]. The die f4oorf t1h1e bottom was the same in all cases.



Combination 1 20



Combination 2 20



R2.5 23



R5 23



Lower Die



Combination 3 21



Combination 4 21



R5 22



R2.5 22



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be out of tolerance.

2.2. Material of the Screw Spike



2.2. TMabatleer2ialshofotwhes SthcreeawvSepraikgee chemical composition by weight of the samples analyzed.



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found in screw spikes. Table 2. Chemical composition of the material of the tested screw spikes.



Table 2. Chemical composition of the material of the tested screw spikes.



Sample



%C



%Mn



%Si



%P



%S



ScrewSasmpipkele 0.31 ± 0%.02C 0.71 ± 0%.06Mn 0.17 ± 0.0%6 Si <0.010 %P



<0.00%9 S



Screw spike 0.31 ± 0.02 0.71 ± 0.06 0.17 ± 0.06



< 0.010



< 0.009



Table 3. Mechanical properties of SAE 1030 [25]. Table 3. Mechanical properties of SAE 1030 [25].



Material Material SAE 1030 SAE 1030



YieYlideldS(MtSrPterane)nggthth (MP34a5) 345



UUlStltitrmiemnaagttetehTT(eMennPssiaill)ee Streng5th50(MPa)

550



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BrHinaredBlnlrieHnsesalr(lHdnBe) ss (1H79B) 179



2.3. DOE of the FEM Analysis

A factorial Design of Experiments (DOE) was carried out, resulting from eight computational simulations of the head forming process, which arise from combining the four die geometries with two diameters of the as-received material. Table 4 shows the sixteen variants computed when considering two flash thicknesses.



Metals 2021, 11, 1834



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ege. .time. TTaTabblaeTlbTeT5alaea5.bbb.C5lleCl.eoeCo5n55.nvo..CvneCCerovogronengenrvvengvenecerrecngrgegceaeenanncaccealneyelayasalninsynsaiasaltliyolystyossetsiioseisstteattotsoabotbelaeieslsbsisthtslataihabsmbbhlmliliesismeshhhsemhimsmnihengeiesgsnshchghociinoinncngndgogdnicctciodiotoninotndidndsoii.stnitit.iosioo.nnnsss...

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FFooFrFcrooceFrreFcco(eoet(r)t(rc(t)ce)te)(t()t) 111555881.8.555.18515.588.5.5 SSimiSmiumSulSiaulmiatmlSitauoiitmutionlmialunoaetlniat(moithiotmno)ienmnet(itehm(imh)(e)he)(h(h)) 444..22.42.244.2.2

EEleElemElmleEeeEmlenelneetmnstmntsestesnntsts 222333,200,37072,676023673,06,07766



118181811.89..19918.9811.9.9 55.56.566.655.6.6 77171575581887571815588



(*()*(()**))(*(*)) (*(*()**)*(()**(**)*)) 111.15.115.1.55111.5.5 1177.17.771.17177..77.7 2233,202,33072,7600237673,606,07766 4466,45,6504,045466006,550,0500000



1188717.82.17218.1288777..2.22 1155.19.591.915155.9..99 111,1,1171,761116711,16,11777666



(*()*()T*T)h(hTe(*(*)*eh)s)TeiTsTmihhsmheeiumeulssaisilummatiilmtoauiuotnlulianaoltfaitnofoitouinfounofnnuodfduonftonudhtudnhetndehtsdhetsteothsophsettpoeocspprcstiorttccoiperrtpieritctireeocririronitioneot(nern2(ir(20oi2(o0n20hn0h)h(2()hw20w)0ihtwiihtt)hhi)wtaahwapiptaiprhtrohropoaggragrropeerpgrsesorsseogososgrfsofer1fes1o9s19f.6s9.o16%.of96%.f.1%6(.19*%.(9*.*6)(..*6%T)(*%*h)T.*e.T()h*(shTe*i)*emhs)TeisuTmihlsmhaeiutmeuilsoasilunmatiilmtoafiuoontuluinaolnatnditoiotnhne stop fofoufuonnudfdconftroudhitutnheetnrdehsidoetstonthsophe(tp2oecs0prcsthoitrtco)ipertpwerictirieocritirohntineota(ern2(pir20oir(o0on2hng0h)(r2()ehw20sw)0sihtwioht)fhi)wta7hwa.4pita%iprhtohr.poagragroperpgresorseogsosgrsoferfes7os7.f4s.o74%of.%4f.7%.7.4.4%%. .



TThTheehTmeTTmhehhmeeceechemmhmcaaheneencaicchinhhcaaiaalacnnlanpiilcpicrcaaepralelsrlsppespsrrcserecoessorcssrosecrcreoscropsreorprosreporensensodpspdnospodsnotnsodntdosdtasotsaot6aot63ao306a603at360t063o3to0ft0fooctfcfatoapccofpaafppaccaiaataipccytpiiyattawcyycwitiwwytihytiihtwthwahaiatirahtorhrodoradodaldrellroeenoldnnegdggntlhettlghhentnohgoofgtffoht11hf100o01o0f00f011m000m000, pmmpempmermare,matpmr,wauapmtaeau,mretccrameaurrrcarse,aaarrtcw,1auentnrwau1narkakcwr5eakncssrse0rhsashakw1ahnaswas◦1nfaakhCf15taktfssa501trssrhaf0a15hartn°a1d10adaC°rfd15diCtafi°u50tuditrCa0suhrsaani°ausoedn°CaoddCfsiodnsfui1ahtfodu1has7tne1f7shn5etoda715ehodrfm5s7efmtsh1f5htmmr1hh7esmeim7eha5cem,5atrs,eammisrh,aaonmfharen,nmfdeinramadfcaicra,dnctr,oiatdsfcoaienrfttosnnrfriadstficnoiodrtctcskcnoraitctoiooaiekreosecnkoenfsteofnrekrtftfceeriofercfowfqoikerofciefukeieqeiarecfeeqeneusfifnniufeqtrfecsitcnreucnwieeyeqtinwetceqnaucynowanuastyefcstsoeanwys3o0nfswesc0.foac3eyt4sarsyf3t0easp[o03tas1ormfs0esp8rafe03tp].smr30t..0pm4aT0.0Ta4.srmh.[.srTph41e0[pT.ehm108.[mmTh4s8.e]14.e.eh]8a.[m.TTe1v][tmTT.1he8haamh8rThe]atlei.e]utehasa.merTeeslmteiTreeshtasivehraeltcvimaetelosateavlrseetlmuprileeamauiteevmlaeelvuesr-almtasf-aeletrtulse-mouuemmres-esccoomcmoecmetcohfoemrfemorfoelmriemobfmrfrtroahtohmretmyehleitolbhtifhlbreitarebhalrrielyrabiybrsoyoraofarffotrytwyhfthoeatoefhrfseetoshtoffhseotfoewtrfswtsomawoarfteferawtedrwfeiaofuaorfrmeroemrfmcofemoaredrrdeimbumdioumeineumddmsicuitcauemarcembralbo–rcobcsnaatnorerbsnebtsoeltosneitnneles–ltest–eslettsr–eetaselect–lelet–sileisotnleitnneteietnlderltiaureniacnrrtctiaetintecorigtroaniacnohctdniotdoiutodunrwniurndiorndguirgnukrgriininnggg. hhooht towhtwThowoorttkrdowkiwrenikotnogeirgnrr.kkm.gTiniT.onignTog.deo.dTetTdetohetoeeerdtmrdetemyretimpetnienreeirmenmotehitfnihetnsehteteetytehtyphtlepyeetpeotoyteoybfpfpoesefetsueotseosfteelfesldetstotledoeetbeuolbelrteboitunoeusbgeusbeedteshdueudedsdsueseduirdmiurndirnduguignulratgrihttnihientogehgnsetisshtmi,hsmeiceumhsulsieaulmiamtmlitauoiiutocnlialnaosatl,snit,oaicsochnn, nheacsse,hmly,mceicshmciehecaseimalcmwlailciecaralel aannaanlylaycasnlaesnyaressalrseylwiysewsedwersseroeweurwceecateracbreraeyirrceircaedsiadprerodarioueriuoekdtdutboobtyopuybusttyipstbcpasbayparylkrsaeksprmopkaoparipotsrkikptscioitcaooipalcnpltaeitelmscicmpaeailmesilecseitmissormisooniisisnosscnsipsooipopesnpecnyctserstp(corpOteosrecEcsoctcoSsrtoprco-opssypscpyc(oayOo(prOpk(EyOyESs(ES-pO(s-OSepsE-cpEasStpaSrr-kors-akspmrspkapsearpestrkpeeckctrserstpcmorpteomrecomoctedmrte-roe-oelmm-Qee-4cAtaeAcatuberrubctAarlgrreermulbgeerrermatAcrlegneTaoMDdeoecatAurambtnedeotrarvuefbd.trlautirrgtnasdde.oanrlhApmetigrecemtrmnehAide.laeaeietihlendonlaaenhAs)aeQtnnadMoit.esd)t.QgblanetiMent.d.e4rnhAtiDs)elQitaM,i4nrthA.eneeDrlaeeaThciul4aaerBgs)eDTQchsauaeMi.s)rneQshraeMTaic.soaieur4rustnDnsmihmsoai4anrfiDrinnakimieTgicmfisouidpnneTpiancsgnheumapnfrsgaekhnuialrtgFisorigpnee,nnhnatinso,imloaftnnhsngeame,niBeBtgafnrpnieenhttgaBso,nmurpadriastgentetouBrfdanrgeeissnnhtitu,Fmannakrinsdnnhrs,eeFwmaBnukonpastegieeoBtunoFm,tenrrkdriitesusrlumkdnP,rrioaisteiranuulman,FmBenikkrrAeraitFminkBolmkn,oituenstaisucotoitceiBunrokrrieguectotainerlmrn,ieiemugensnrarlmnn,otssPBsketsanregteosiB,ssPkn,teiwrtiunsoines,soteiuonsPriwtAsegeotscondso,siAwcegersnon.sleArcesPosntiwamooigesPnre,stsAAcrrboi,soessurseereoeriwbosoeeiscmotnsertiswsAccririenmscoeAs,scecaenentaseoie,eomsarAlsscrataeiasrroesAlro,rea)tcaoevdrbesiremeAirlsrcceogrbeimoeaosiosyr,caeogdnmecsorerb,inranAldrmeeoegtoigarAolrsoifbtdacmefrtbnriy,orsibucoitreogbittnaIoaatnouoeoigoibdtNrimohetannm)rfadyutmreoittra)eIaanTotyoittbtRarptinooi)hotboanufIyooitntioAvlofau-nnoieotootnreMavnfios)erIsatrnynMosts)NasemavrIfeyotot,senNaimriootsoeoInf,oTcfiiomasNatvNrfynofofTáhnp,vIttfimyseInlnih-fpTIieMssselNaItdoryMf-esiie,NpahplrIimMncfse,sft-TfimeiltaeyhfMosITtfkehwptIooyeShcoerhps-(ItefoielcfáfOemeBMhr-sofeieelfáonMmcfsefsesreurstfnoapfseáieehsmc1tosfefcapoelhtinocriseo9rfdncaoifktcefáapieroimoos7laikfofácswemndt(soselino2uainBesdks(eapionso-slBsfnacpiuetdAs(AicscoonfcwaitBukdiocrecoasailwfskSieorudeu(nlervfcnowieTdB(wfennerrensorasfBowfssMueerrosnceosiswlu,eeswfcloresrdwosfflaoAAodreaeeondfefsEsAsbelanmwvfoe.riurodsfowfAlvrraegoiuooA1esnssereleavioesiucnds6lfesdlAriadnaoc-fo-os5A,sdnlseaov-i-tetius,fc,sdlvriiuaro--nn,tttreaioihhhnceeasdlic--sdeeel,s)--,.

method was applied using the visible water technique. The final cleaning of the samples was done each time in two stages: washing with solvent and brushing and then drying with a hot air projector. The drying temperature was below 70 ◦C and a Magnaflux penetrant liquid type SKL-WP with a penetration time of 15 min was used, while the excess liquid was removed by spraying. The developer used was wet non-aqueous SKC-S2.



Metals 2021, 11, 1834



in some of the available samples of spike screws. According to IRAM NM ISO 1972-ASTM E 165, the method was applied using the visible water technique. The final cleaning of the samples was done each time in two stages: washing with solvent and brushing and then drying with a hot air projector. The drying temperature was below 70 °C and a Magn6aofflu11x penetrant liquid type SKL-WP with a penetration time of 15 min was used, while the excess liquid was removed by spraying. The developer used was wet non-aqueous SKC-S2.

Two spike screws were scanned, one manufactured from a worn matrix and the other withTowutoaspppikareesnctrewwesarwmeraerkscsa, unnsiendg, aonsterumcatunurefdacltiugrhetd3fDrosmcaannweorr(nHmP,aBtrairxcaenlodntah,eSpotahiner). wSuitbhsoeuqtuaepnptlayr,eantstwuedayrwmaasrkcsa,rruiseidngouatsttorudcetuterremd ilnigehtth3eDmsecaasnunreerm(HenPt, dBeavrciaetlioonna,wSipthainre)-. wtrsaSTArfsoetenuephaesNctdbetruteothiecseOlseetetrdputxsVqeitlCttcosruooiAraeulAbaetitlsslzncthsptDtaetsttweooildatnyoohdntCe,etilbesresoaAdeuettscsaidsiDsfcotugirieuaanrnonttnldrdieemgleddteuyrisozmMssptweeoifhigoirxdnlinaeonntngusremticdasotucoGtaiicahsmnnbtdtOriehggnrtep(hMiergtvevMueeedeacltrGaIaricolmonnutsotOmiiuiisevirootnMptrspaenneetebuoaioscm1Itflpt(tndah5vstopsts,heeieinpmootAoeredrrefsnuretpdtciiwamalnol-tdaanvlngasitltcansiiiorenvovl1ieefumna5ektotew(l,s,hfuZuisAMmeewa.leeaardsmipeatecsdirodhosoee(l,frranZifteinBtsasadehvukcuni,eawtrs,ecoSelsMpnueermp,-roaaBavoaeetsniaduefnndelAdreteu)vindatidaeBarhoceps,elohesv.upsSxia,aAplfayftaaAatfeiincierindortnecdgognts)aeer,PtwBndphAaaotpienrritrxleenhdgAystaaeroipN)tnnen.hopsgdOtnepiTlnVosetPhaehatcAafess)te--.

33.. RReessuullttss TThhee ccoommppuuttaattiioonnaall ssiimmuullaattiioonnss ffoorr tthhee ddiiffffeerreenntt ggeeoommeettrriiccaall--ddiimmeennssiioonnaall ccoommbbiinnaa--

ttiioonnss aanndd pprroocceessss vvaarriiaabblleess uusseedd ffoorr hheeaadd ffoorrmmiinngg aarree ppeerrffoorrmmeedd.. TThhee ffoorrmmiinngg eenneerrggyy,, ffoorrmmiinnggloloaaddssanadndcocnotnactat cptrepsrseusrseusr,eths,etmheatmrixatfirlilxinfgil,lainngd, tahnedaptpheeaarapnpceeaorafndceefeoctfsd(feofledcst)s p(floalydas)crpulacyialarcorleuciniatlhreolsecrienwthsepiskcerepwrodspuickteiopnr. oPdeuncettiroann.t Pineknsetvrearnifit eindktshevearpipfieeadrathneceaopfdpeefaercatnscaetothf edesfuercftascaetathnedstuhrefawceoranndartehaes wwoerrne eavreaalus awteedrebeyva3lDuastceadnbnyin3gDanscdanvnailnidgaatendd wvaitlhidtahteeddewsiirthedthCeAdDespiraerdt.CAD part.

33..11.. Computational SSiimmuullaattiioonnss

UUssiinngg aa 22..2255 mmmm tthhiicckk bbuurrrr cchhaannnneell rreessuulltteedd iinn aa llaacckk ooff fifilllliinnggaatttthheehhuubbvveerrttiicceessiinn aallll ccaasseess.. Figure 3 sshows the ssimmulation of that lack of pprrooppeerr fifilllliinngg aatt tthhee ccoorrnneerr oofftthhee hheeaadd ooff tthhee ssppiikkee.. All simulatioonnss uusseedd 11..5500 mmmm bbuurrrr cchhaannnneell tthhiicckknneessss sshhoowweeddccoommpplleettee fifilllliinngg ooff tthhee ffoorrmmiinngg ddiiee..



FFiigguurree33.. SSccrreeww ssppiikkee wwiitthh aa vveerrtteexx uunnddeerrfifillllffoorr22..2255mmmmbbuurrrrccaannnneell..

FFiiggures 4 and 5 shhooww tthheeccoorrrreessppoonnddiinnggbbooxxpplolotstsfoforrloloadadanadndeneenregrygyrerseuslutsl,tss,esgergergeagtaetdedbybyhehaedadananglgel,e,hhuubbtotoccaapprraaddiuiuss,,ffllaasshhtthhiicckknneessss,, aanndd startiingg material diameter, rreessppeeccttiivveellyy..TThheefoformrmininggeenneregrgyyananddfofromrminignglolaodadasaas faufnucnticotnioonf ohfeahdeaadngalnegalendanhdubhutob Metals 2021, 11, x FOR PEER REVIEWctoapcarpadriaudsiushsoswhonwonsoigsniigfinciafinctandtifdfeifrfeenrceensc.eAs.dAdditdioitnioanllayl,ltyh,ethceomcobminbaintiaotnioonf oefnenrgeyr7gayosfaa1s2 faufnucnticotnioonfohfehaedaadnagnleglperpesrensetsntassalisglhigthdtifdfeifrfeenrecnecien itnhethaevaevraegraegoef oafbaobuotu9t.29%.2.%.



Box plot - Force (t), Energy (kJ)



Box plot - Force (t), Energy (kJ)



1.30



4.29



2.5



5.0



Force (t)



Energy (kJ)



200



4.0



Force (t)



Energy (kJ)



200



4.0



175 3.5

150



125



3.0



175 3.5

150



125



3.0



100 2.5

75



100 2.5

75



50 1.30



2.0 4.29

Head angle



50 2.5



2.0 5.0

Radius corner splice



Figure 4. Box plots for geometric parameters according to the standard. Figure 4. Box plots for geometric parameters according to the standard.



Box plot - Force (t), Energy (kJ)



Box plot - Force (t), Energy (kJ)



Force (t) 200



1.50



2.25



Energy (kJ)



4.0



200



Force (t)



23.54



24.06



Energy (kJ) 4.0



175



175



Metals 2021, 11, 1834



150



125



3.0



150



125



3.0



100 2.5

75



100 2.5

75



50 1.30



2.0 4.29

Head angle



50 2.5



2.0 5.0

Radius corner splice



Figure 4. Box plots for geometric parameters according to the standard.



7 of 11



Box plot - Force (t), Energy (kJ)



1.50



2.25



Force (t)



Energy (kJ)



200



4.0



175 3.5

150



125



3.0



100 2.5

75



50 1.50



2.0 2.25

Flash



Box plot - Force (t), Energy (kJ)



23.54



24.06



Force (t)



Energy (kJ)



200



4.0



175 3.5

150



125



3.0



100 2.5

75



50 23.54



2.0 24.06 Starting material diameter



FFigiguurree55..BBooxxpplloottssffoorr tthhee aannaallyyzzeedd pprroocceessss ppaarraammeetteerrss..

AAddddititioionnaalllyly, ,ththeestsatatitsitsitciacal laannaalylysissisoof fththeecocommbbininataitoinonofoffofromrminigngeneenregrygyanadndfofromrmin-g loinagd lroeagdarrdeignagrdfliansgh ftlhaischknthesicsksnheosws sshvoewrys svigenryifisciagnntifdicifafnetrednicffeesr.eInncpesa.rtIincuplaarrt,iacsultahri,ckaesr tthheicflkaesrhthiseuflsaesdh, itsheusleodw,etrhethleowloeardthaendloeandeargnyd reenqeurgiryedretqoufiorermd ttohfeohrmeadth.eMhoeraedo.vMero, rteh-e doivamer,ettehreodfiathmeeatesr-roefcethiveeads-mreacteeirviaeldpmreasteenritaslaplroewseenrtsimaploawcteirnimthpeapcrtoicnetshs,eapltrhooceusgsh, ailtt-is dheonuogtehditthiastdaesnthoeteddiatmhaettearsinthceredasiaems, ebtoetrhilnocardeaasneds,ebnoetrhgyloinadcreaansde.eAnnerAgyNiOnVcrAeaasnea. lAysnis wAaNs OpeVrAforamnaeldystoisewvaaslupaetrefomromreedptroeceivseallyuathteeminoflrueepnrceeciosfeelyacthhepianrfalumeentceer oofnetahcehlopaadraamn-d eenteerrgoynvtahleuelosaudsianngdtheneepr-gvyalvuaeluwesithusain0g.0t5hleevpe-vl oalfuceonwfiitdhenac0e..0T5 hleevreelsoufltcsoonffitdheenAceN. OThVeA arreesulislttsedofinthTeaAbNleO6.VA are listed in Table 6.



TTaabblele66. .RReessuultlstsoofftthheepp--vvaalluueeffoorrtthheeaannaallyyzzeedd ffoorgging parameters.



Factor Factor

Head angle HubHteoHadcuaabpntrgoaldeciaups radius As-reAcesiv-reedcmeiavteedriaml datiaemriaetledr iameter

Flash tFhliacskhnetshsickness



LoadL(ot)ad (t) 0.233

00..2536390.569 0.0000.000 0.0000.000



p-Valupe-Value EnEenregrygy(k(Jk)J) 0.000 0.5005..5015010 0.000.0000 0.00.0000



TThheeAANNOOVVAAeexxhhiibbiittss tthhaatt bbootthh tthhee ffllaasshh tthhiicckknneessssaannddtthheeaass--rreecceeiviveeddmmaateterirailalddi-iaammeetteerrhhaavveeaassiiggnniifificcaanntt iinnflfluueennccee oonn tthhee llooaadd aanndd eenneerrggyy vvaalluueessaannddtthheehhuubbaannggleleththaatt ininflfulueenncceesstthheeffoorrmmiinngg eenneerrggyy.. OOnn tthhee ccoonnttrraarryy,, tthhee hhuubb ttoo ccaapp rraaddiiuussddooeessnnoottiinnfflluueennccee Metals 2021, 11, x FOR PEER REVIEWtthheerreessppoonnssee vvaarriiaabblleess.. TToo ddeetteerrmmiinnee tthhee oorrddeerr ooff iinnfflluueennccee,, FFiigguurree66 sshhoowwsstthheeP8Paoarfreet1ot2o ddiaiaggrraammssffoorrffoorrcceeaanndd eenneerrggyy..



Pareto Chart of the Standardized Effect (response in Force (t), Alfa = 0.05) 2.20

Flash



Pareto Chart of the Standardized Effect (response in Energy (kJ), Alfa = 0.05) 2.20

Flash



Starting material diameter



Starting material diameter



Term Term



Head angle



Head angle



Radius corner splice



Radius corner splice



0



5



10



15



20



25



Standardized Effect



0



5



10



15



20



Standardized Effect



FFiigguurree66..IInnflfluueennccee oorrddeerr ooff tthhee ooppeerraattiinngg ppaarraammeetteerrss oonnllooaaddaannddeenneerrggyyoofftthheeffoorrmmininggpprroocceessss. .

TThhee PPaarreettoo ddiiaaggrraammssrreessuultlstsininddiciactaetethtahtatthethfeorfmorimnginlogaldoashdoswhsowthse tfholelofwolilnogwiinn-g ifnlfluuenecnec:ef:laflsahshthtihcikcnkensesssfoflolollwowededbybythteheasa-sr-erceecievivededmmataetreirailalddiaimameteetre.r.WWhhilieleththeefoformrminingg eenneerrggyypprreesseennttss tthhee ffoolllloowwiinngg oorrddeerr ooff iinnfflluueennccee:: ffllaasshhtthhiicckknneessss,,tthheeaass--rreecceeiviveeddmmaateteriraial l ddiiaammeetteerr aanndd,,aalslsoo, ,huhbu-bto-t-oc-acpapradraiudsi.uNs.otNe tohtaettwhahtenwuhseinngutshienlgartgheestlaarsg-reescteaivse-rdemceaivtee-d mriaatledriiaaml deitaemr, ei.tee.r,,2i4.e.0.,62m4.0m6, mfomld,sfaopldpseaarpepdedaruerdindgutrhiengpltahseticplfaosrtmicinfogrmsiminuglastiimonul(atthiiosn was a finding that we had not visualized on the screw spikes samples). Figure 7 shows

how these folds are created during the forming process.



Metals 2021, 11, 1834



Figure 6. Influence order of the operating parameters on load and energy of the forming process. Figure 6. Influence order of the operating parameters on load and energy of the forming process.

The Pareto diagrams results indicate that the forming load shows the following influeTnhcee: Pflaarsehtothdiciakgnreasms fsorlleoswuletds ibnydtihcaeteast-hreactetihveedfomrmatienrgiallodadiamsheotwers. Wthheifleoltlhoewfionrgmiinn-g fleuneenrcgey: fplaresshetnhtisctkhneesfoslfloolwloiwngedorbdyerthoef ains-flrueceenicvee:dflmasahtethriiaclkdnieasms,ettheer.aWs-rheicleeitvheedfomram8toeifnr1iga1l edneiarmgyetperreasnendt,satlhsoe,fhoullbo-wtoin-cgaporrdaedriuosf.iNnfoluteenthcaet: fwlahsehnthuisciknngetshse, tlharegaess-traesc-erievceedivmedatmeraiatel driiaaml detiearmaentder,,ail.seo.,, h24u.b0-6tom-cmap, froalddisusa.pNpeoateretdhadtuwrihnegntuhseinpglatshteiclafrogremsitnags-sriemceuivlaetdiomn a(tthe-is riwalasdiaamfinetdeirn,gi.eth.,a2t4w.0e6 hmamd ,nfootldvsisaupapliezaerdedonduthreinsgcrtehwe pslpaiskteics fsoarmmpinlegs)s.iFmiguularteio7ns(hthowiss w(thhaoiswsawtfhainsesdaeifinfnogdldtihnsagatrtwehacetrehwaaetdehdnaoddtunvroiintsuvgiatslhuizeaelfidozreomdniontnhgetphsercosrcceerwsesw.spsipkieksessasammppleles)s.).FFigiguurree77 shows hhooww tthheessee ffoollddss aarre created during the forming process.



FFigiguurree77. .SSeeqquueenncceeoofffofoldldfoforrmmaatitoionnaattththeeccaappooffththeehheeaaddooffththeessccrerewwspspikikee. . Figure 7. Sequence of fold formation at the cap of the head of the screw spike.

SSeevveerraallssaammpplleessooffssccrreewwssssppikikeesswweerreeaannaalylyzzeeddwwitihthppeenneetrtraannttininkksstotovvaalildidaateteththee ccoommpSpueuvtateatritoaiolnnsaaal mlsismpimlueuslalotaiftoisnocsnr.seF.wiFgsiugsruperie8ke8dsedwmeemorneosntarsnatartealysteztshedethrweesirtuehlstupoletfntoehftertahpneetnpieentnrkaesntrttoainnvtkaislnisdkhsaotswehtionhwge ctohinmegcptihurcetuactlaiiorrcn-usahllaasrpi-msehduaflpoaetldidoonfonsl.dtFhoiegnucatrhepe8ocfdatpehmeofoscnthrseetwrsa.ctreeswth. e result of the penetrant inks showing the circular-shaped fold on the cap of the screw.



Metals 2021, 11, x FOR PEER REVIEW



9 of 12



FFFiiggiguuurreree88.8. F.FFooollddldssseexexxpppooossesededdbbbyyypppeenenneetetrrtaratatiitnningggiinninkkksssooonnntthhtheeeccacapappoooffftthhtheeesscscrcreerweww.. . IInn FFiigguurree 99,,iittiisssshhoowwnnininddeteatialitlhteheprporgorgersessosfothf ethceoncotancttapctrepsrseusrseudriestdriibsturtibiountiionnthine

tdhieffedrieffnetrpenhtapsehsaosfesthoef ftohremfoinrmg pinrgocpersos.ceAsts.thAetsttheepsotefpthoefhtheaedhefoardmfionrgm, iint gca, nit bceansebeensteheant tthhaetotuhteeroudtiearmdeitaemr oeftetrheofmtahteermiaaltfierrisatlmfiarsktesmcaoknetsacctowntiatchttwheitshidthese osfidthese otofotlhinegtocoalvinitgy. cTahveithyi.gThheesthciognhteascttcpornetsascutrperiessfsouurnedisaftotuhnedraadtituhseorfaadgiureseomfeangtrbeeemtweenetnbtehtwe ceaepn athnedctahpe ahnedadthoef htheeadscorefwthsepsickree.wThspeimkea.xTimheummacxoimntuacmt pcroenstsaucrtepsrwesesruerfeosuwnderteofboeunindtthoeboerdinerthoef o8r8d4eMr oPfa8, w84hMilePtah,ewyhieilledtshtereyssieoldf astqruesesnochf eadqaunedncthemedpaenreddtAemISpIeHre1d3 AsteISeIl Hat1435sHteReCl awt 4a5s H12R8C0 MwPasa 1[2268]0. MPa [26].



Figure 9. CCoonnttaacctt pprressure along the forming process of the head of the screw spike.

3.2. Screw Spike Surface Scanning The surfaces were scanned to determine the geometric deviations and validate the

results of the simulations. Accordingly, Figure 10a exhibits the geometrical deviations of



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Figure 9. Contact pressure along the forming process of the head of the screw spike.

33.2.2. .SSccrreewwSSppikikeeSSuurrfafacceeSSccaannnniningg TThheessuurrfafacceesswweerreessccaannnneeddtotoddeetetermrminineeththeeggeeoommeetrtircicddeevviaiatitoionnssaannddvvaalildidaateteththee

rreessuultlstsoofftthheessiimmuullaattiioonnss.. AAccccoorrddiinnggllyy,, FFiigguurree1100aaeexxhhibibitistsththeeggeoeommetertirciacladl edveivaitaiotinosnos f otfhtehheehaedaodfoafsacrsecwrewspiskpeikfoerfmoremd eind ainn aunnwunowrnomrnatmriaxtcrioxnccoernncienrgnitnhge CthAeDCAwDithwthitehmthienmiminuimmudmimdeinmsieonnsaiol tnoallertaonlecreasn. cFeigs.urFeig1u0rbes1h0obwsshtohwe gsetohme egteroicmaledtreivcaialtdioenvsiaotfiothnes hoefatdheof haeasdcroefwa sspcrikewe fsoprimkeedfoirnmaedwinoranwmoartnrimx awtriitxhwreitshperecstpteoctthteo tChAe DCAwDithwitthhethmeinmiminuimmumdidmimenensisoinoanlaltotoleleraranncecse.s.FFigiguurere1100ccccoommppaarreess tthhee ddeevviiaattiioonnss bbeettwweeeenn tthhee twtwoopprervevioiouuss ssccaannnneeddssaammppleless(F(Figiguurere1100aa,b,b).).FFininaalllyly, ,FFigiguurere1100ddccoorrrerespspoonnddsstotoththeewwoornrnaacctutuaal lccaavvitiyty foforrmmininggththeehheeaaddooffaassccrerewwspspikikee. .



FFigiguurere101.0T.hTeh3eD3sDcasncaimnaigmeasgweesrewaenraelyazneadlywzietdh GwOitMh GInOspMecItnorsptoecdteotrertmo idneettehremdiinmeetnhseiodnia-l dmeveinatsiioonnbaeltdweeveniastaiomnpbleestwforemenedsaomn npelewsafnodrmweodrnodniense. w and worn dies.

InInththeessccrreewwssppikikee, ,ththeewweeaarrzzoonneessaarerefofouunnddininththeecceenntrtaral lppaartrtoof fththeessidideewwaalllslsoof fththee hhuubbaannddtthhee hhuubb ttoo ccaapp rraaddiiuussoofftthheessccrreewwspspikikee(s(eseeeFiFgiugruere101b0)b. )T. hTishirsegreiognioins wishwerheetrhee the material first makes contact with the die cavity. Additionally, it is where the highest contact pressures occur during forming, according to the results obtained from the finite volume simulation. The contact pressures, associated with the magnitude of the load and forming energy, inversely depend on the flash dimensions (thickness and length) [27]. In particular, for lower flash thickness, higher plastic strain is determined in the simulation and, therefore, higher forming energy per cycle is assessed; consequently, higher wear of the die is expected. Figure 11 shows the maximum contact pressure regarding the flash thickness and segmented by wear zones (radius and hub face).

Since the deviations of the worn zones are negative, the plastic deformation of the die hub is reducing its size, as shown in Figure 10d. Other aspects of railway tracks manufacturing are related to hole and drilling quality, similar to other cases and applications, so in further research the hole quality will be also investigated [28].



Metals 2021, 11, 1834



tact pressures occur during forming, according to the results obtained from the finite volume simulation. The contact pressures, associated with the magnitude of the load and forming energy, inversely depend on the flash dimensions (thickness and length) [27]. In particular, for lower flash thickness, higher plastic strain is determined in the simulation and, therefore, higher forming energy per cycle is assessed; consequently, higher wear of the die is expected. Figure 11 shows the maximum contact pressure regarding the10floafs1h1 thickness and segmented by wear zones (radius and hub face).



FFiigguurree 1111.. MMaaxxiimmuumm ccoonnttaacctt pprreessssuurree rreellaatteedd ttoo tthhee flflaasshh tthhiicckknneessss aanndd mmoosstt ddeeggrraaddeedd aarreeaass..

4. Conclusions udmofifeaaacihntrSTuuacirhbnioilincnwissegcawlrtuayehordseesriuopkrdcniefiekslnovae:gcitauesictdstirseoetssnowisozhneboo,yflmaetschiaonsenmhidmwopdwiouzrrntiinnallitginzinootgFnhniqaeeglusuesaranilermieet1ryug0n,lydsea.igtrmiOaeotqitnilhuva.erierTr,teohatdhseopeftroeheprceslturamsslcotetasiftcsarseladhsifeolaofwwnormdartmyhiantapergtpaifoolctihknlclesaootwmhifoeitannahnsdge-, so in further research the hole quality will be also investigated [28]. 1. The wear is mainly focused on the die splice radii, where the highest contact pressure 4. Conisclcuosnicoennstrated according to the computational simulation results. Specifically, the

Tsthhcaeisndnwieeodrrakwdfoiourcnsu.hseeasdosnshmoiwniemdiazitnrgantshfeereonfemrgayterreiqaul oirnedthfeosridmeewtaalllfsoorfmthineghtuhbethoewaadrdosf a2.railwThaey mspaiiknefsaccrteowr thbyatcaofmfecptusttahteiolnoaaldsaimndulfaotrimonin. Tgheenerergsuylitss tshheoflwasthhethfoiclklonwesins,gwmhaicinh concluitssiovnaslu: e depends on the initial setup. Specifically, the minimum forming energy 1. Twhaeswoebatrains emdafionrlycfoomcubsiendinognathheudbiewsapllicaenrgaledioi,fw1.h3e◦r,eathsteahrtiignhgesmt caotenrtiaacltdpiraemsseutreer

iosfc2o3n.c5e4ntmramte,danacdcoardfliansgh ttohitchkenceosms opfut2a.2ti5onmaml s.imTuhliastifloanshretshuilctks.nSepssecgifeincaelrlayt,etshae slcaacnknoefdfiwllionrgnahtetahdestoshpovweertdicaestroafntshferhoufb,maaltheroiualghonthtihsedseifdeecwt daollessonfotthaeffheucbt tthoewfuanrdctsiothnealditiye oraf dthiuesp. art or its serviceability. 23. TAhne masa-irnecfeaicvtoedr thmaattaefrfieacltsdtihaemleotaedr aindthfoermhiignhgeernrearnggyeisotfhedfilmasehnsthioicnkanl etsosl,ewrahniceh, i2ts4.v0a6lume mde,ppernoddsuocnesthfeolidnistioanl sethtueph. eSapdeccifaipcaallnyd, thinecmreiansiemsutmhefoernmeringgy ebnyeragtylewaasst o1b8t%ai,nwedhifcohr icnocmrebaisneisntghae hpurobbwabailllitaynogflefaoiflu1r.3e°o, fatshteardtineginmaastehroiratlednieadmteimteer.of 23.54 mm, and a flash thickness of 2.25 mm. This flash thickness generates a lack of filling Authoart Cthoentroipbuvteiorntisc:eCsoonfctehpetuhaulizba,taioltnh, oNu.Lg.hd.Lth. aisnddeDf.eMct.Kd.;omesetnhotdoalfofegcy,tAth.Se.,fGu.nAc.taiondnaAl.iJt.yS.Eo.f; expertihmeepnatarlttoesrtist,sJ.sAe.r,vAic.Se.aabnidlitGy.A.; formal analysis, all authors (J.A., G.A., N.A., A.S., A.J.S.E., 3D..M.KA.nanads-Nre.Lce.div.Le.)d; imnvaetsetrigialtidonia, malleateurthionrsth(Je.Ah.i,gGh.eAr.,rNan.Ag.e, Ao.fSd., iAm.Je.Sn.sEi.o, Dna.Ml t.Kol.earnadncNe.,L2.d4..L0.6); resoumrcmes,, pDr.oMd.Kuc. easnfdolNd.sLo.dn.Lt.h; ewhreitaindgc—aporaignidnailndcrreaaftsepsretphaeraetnioenrg, yJ.Aby., aDt.Mlea.Kst. 1a8n%d ,Aw.Jh.Si.cEh.; writiningc—rereavsieeswthaendpreodbiatibnigl,itaylloafuftahiloursr;esoufptehrevidsiioeni,nAa.Js.Sh.oEr. taenndedNt.iLm.de.L. .; project administration, D.M.K. and N.L.d.L.; funding acquisition, N.L.d.L. and D.M.K. All authors have read and AagurteheodrtoCtohnetrpiubbultiisohnesd: vCeorsnicoenpotuf athliezamtiaonnu, sNcr.iLp.td. .L. and D.M.K.; methodology, A.S., G.A. and AFu.Jn.Sd.Ein.;ge: xTpheirsimwoenrktailstseusptsp, oJ.rAte.d, Aby.S.thaenSdeGrr.aAH.;úfonrtmeraplraongaralymsis(G, aelnlearuatlhitoatrsde(J.CAa.t,aGlu.Any.,aN) r.eAf.e,rAen.Sce., Anu.Jm.S.bEe.r, D(U.MPC.K-.LaEn-d30N4 .(L2.0d1.L8.))); ainnvdesbtyigtahtieonA,earlolnaauuthtiocrssA(Jd.Av.a,nGc.eAd.,MNa.Anu.,fAac.Stu.,rAin.Jg.SC.Ee.n, Dte.rM(C.KF.AaAnd). NTh.La.ndk.Ls .a);lsroesaoreurgcievse,nDto.Msp.Ke.ciaanl dagNre.eLm.de.Ln.t; IwNrTiIt-inFagc—ulotryigoifneanl gdinraefetripnrgepoafrBaitliboano, aJ.nAd.,toDu.Mni.Kve.rasintdy group grant IT 1337-19.

Institutional Review Board Statement: Not applicable.

Informed Consent Statement: Not applicable.

Data Availability Statement: Data sharing is not applicable.

Acknowledgments: The authors acknowledge Mariano Fernández Soler for providing the spike screw samples, María Emilia Boedo for helping with the chemical analysis, Aurelio Martins Dos Santos for performing the liquid penetrant tests, and Facundo Riu for the drawings.



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Conflicts of Interest: All the authors who sign this manuscript do not have any conflict of interest to declare. Furthermore, the corresponding author certifies that this work has not been submitted to or published in any other journal.

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