Metal additive manufacturing techniques such as the powder-bed systems are developing as a novel method for producing complex components. This study uses synchrotron-based X-ray microtomography to investigate porosity in electron beam melted Ti-6Al-4V in the as-built and post-processed state for two different powders. The presence of gas porosity in the starting powder was shown to correlate to porosity in the as-built components. This porosity was observed to shrink after a hot isostatic press treatment, but grow following a subsequent heat treatment. Crystal plasticity simulations were used to observe the effects of various observed pore sizes on mechanical behavior under loading. IMPACT STATEMENTThis work combined µSXCT and crystal plasticity simulations to characterize porosity through each processing stage of EBM Ti-6Al-4V. Gas porosity was detected in the as-HIPed state, and growth was observed after subsequent heat treatment.

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FE Robustness: comparing sheet metal forming variation and finite element models AIP Conf. Proc. 712, 958 (2004); Abstract. New forming technologies based on compliant "discrete-die" reconfigurable tooling are available for production of sheet metal parts, but there is a need for a formalism that can accurately predict the three-dimensional shape of the required tooling, a priori. An optimized tooling design algorithm has been developed based on a methodology that uncouples the effects due to springback and those due to the compliance of the polymeric layer. A springback compensated die shape is initially predicted for the case of stretch forming over smooth rigid dies based on an iterative approach using the finite element method. The tooling design algorithm is based on an inverse springback approach that uses the elastic-plastic stress state prior to unloading to elastically deform the sheet in a direction opposite to springback. A procedure has been developed to improve the convergence behavior of the inverse springback approach utilizing an interpolation scheme. The interpolation scheme uses prior iterations to predict the desired die shape by fitting spatially varying quadratic relationships between the tool shape and the part shape error histories. The optimized tooling design algorithm is extended to compliant dies by developing a method that corrects the die shape for polymer through the thickness compression. The algorithm is applied to stretch forming of large-scale airframe skin parts commonly found in aerospace structures. Two shapes are investigated, a 90-inch radius cylindrical cap and a 90inch radius spherical cap.