Page - 54 - in 3D Printing of Metals

Metals 2017,7, 91 In thepresentworkaredescribedthepropertiesof the individualelementsusedfor theformation of the lattice structures. The identification of properties was therefore carried out on elements that correspond to real geometric conditions as for the lattice structures. It is of major interest to determine the properties of individual bars integrated into specialized applications. This is particularly interestingforapplicationswheretherodswithinacomponentshowdifferentorientations to the load (seeFigure1) and the structuralparameters cannotbecomparedwith typical scaffolds (as shown in the literature). Therefore, the strut elements are considered in thiswork. The strut elements form thebasis for load-bearingporous structures.Variations in the geometry of the test specimenaswellas in themanufacturingprocesscanbeexcludedhere. Inadditiontocharacterizing productionqualityandsurfacequalityof the individualstruts, selectedmechanicalpropertieswere determined. Thesamplesweremanufacturedusingadditivetechnologieswithvariationsindimension (variations in theheight/diameter ratio)andalso installationspaceorientation. Selective lasermelting andelectronbeammeltingwere the twomanufacturingprocessesusedtoprovidethepossibility to comparebothmethods.Furthermore, thedirectionaldependenciescanberepresentedwithreference to theproperties. Figure1.Exemplaryrepresentationofpartofapelviswithanacetabularcup. Thesurface isprovided with a load bearing porous structure. The load bearing structure consists of a layer of repeating structuralelements. Thesmallestelement inanycase is therod. Previous works comparing the two manufacturing methods mentioned above refer to test specimenswithgeometricdimensions that greatlydiffer from thoseof the individual elements of thegridstructures [38]. Inaddition, the focus isalwaysplacedondeterminingsuchproperties that wouldpresuppose tensile loading. Simonelli etal. [39] studiedthe tensilepropertiesofSLMTi6Al4V specimens in three directions consisting of 2000, 200 and 60 layers. Qiu et al. [40] examined the tensilepropertiesofTi6Al4Vspecimens indimensions thatarenot relevant insmall latticestructures. Aloadsituationthatoften isof interest inbiomedicalapplications is thepressure load(forexample, inorthopediccases). Thepresentworkthereforestudiesthemechanicalpropertiesofthemanufactured test specimensunderanappliedpressure load. The aim was to characterize the individual struts macroscopically, microscopically and mechanically. The results obtained shall be used to gain a better understanding of the behavior of the individualelements. Theresultscanbetransferred intomedicalapplications. Theseprimarily includethestructuralareas for implantsconstructedfromgridelements. 2.MaterialsandMethods 2.1. PartsDesignandConfiguration The specimens formechanical testingwithin this studywere designedusingCADsoftware (PTCCreo,Version2.0,ParametricTechnologyCorporation,Needham,MA,USA).Thesamplesare showninFigure2. Thesinglestrutspecimenconsistsofabaseareaandatoparea. Theseareasare importantassupportsduringpartmanufacturingandforreworking(facecuttingtoobtaintwoparallel surfaces) after additivemanufacturing. Inboth areas, there arepunched-out clearances to reduce 54