Book Description

The objective of this work is to experimentally validate thermal andmechanical finite element models of metallic parts produced usingadditive manufacturing (AM) processes. AM offers advantages overother manufacturing processes due the fact that it can produce netand near-net shapes directly from a digital drawing file. Parts canbe produced on a layer by layer basis by melting wire or powdermetal using a laser or an electron beam. The material then cools andsolidifies to form a fully dense geometry. Unfortunately the largethermal gradients cause a buildup of residual stress often takingparts out of tolerance or causing failure by cracking ordelamination. To successfully reduce distortion and residual stressin metallic AM parts without expensive and time consuming trial anderror iterations, an experimentally validated physics based model isneeded.In this work finite element (FE) models for the laser directedenergy deposition (LDED), the Electron Beam Directed Manufacture(EBDM) process, and the Laser Powder-Bed Fusion (LPBF) process aredeveloped and validated. In situ distortion and temperaturemeasurements are taken during the LDED processing of both Ti-6Al-4Vand Inconel 625. The in situexperimental results are used in addition to post-process residualstress measurements to validate a thermo-mechanical model for eachalloy. The results show that each material builds distortiondifferently during AM processing, a previously unknown effect thatmust be accounted for in the model. The thermal boundary conditionsin the model are then modified to allow for the modeling of the EBDMprocess. The EBDM model is validated against in situ temperature anddistortion measurements as well as post-process residual stressmeasurements taken on a single bead wide Ti-6Al-4V wall build.Further model validation is provided by comparing the predictedmechanical response of a large EBDM aerospace component consistingof several thousand deposition tracks to post-process distortionmeasurements taken on the actual part. Several distortion mitigationtechniques are also investigated using an FE model. The findings areused to reduce the maximum distortion present on the largeindustrial aerospace component by 91~\%. Finally, the modeling workfor the LDED and the EBDM processes is extended to Laser Powder-BedFusion (LPBF) processing of Inconel718. The necessary boundary conditions and material properties toinclude in the models are identified by comparing the model with insitu experimental results.