TY - CONF A1 - Mishurova, Tatiana A1 - Artzt, Katia A1 - Bruno, Giovanni A1 - Requena, Guillermo A1 - Haubrich, Jan T1 - Subsurface residual stress analysis in Ti-6Al-4V additive manufactured parts by synchrotron x-ray diffraction N2 - Synchrotron X-ray diffraction is a powerful non-destructive technique for the analysis of the material stress-state. High cooling rates and heterogeneous temperature distributions during additive manufacturing lead to high residual stresses. These high residual stresses play a crucial role in the ability to achieve complex geometries with accuracy since they can promote distortion of parts during manufacturing. Furthermore, residual stresses are critical for the mechanical performance of parts in terms of durability and safety. In the present study, Ti-6Al-4V bridge-like specimens were manufactured additively by selective laser melting (SLM) under different laser scanning speed conditions in order to compare the effect of process energy density on the residual stress state. Subsurface residual stress analysis was conducted by means of synchrotron X-ray diffraction in energy dispersive mode for three conditions: as-built on base plate, released from base plate, and after heat treatment on the base plate. The quantitative residual stress characterization shows a correlation with the qualitative bridge curvature method. Computed tomography (CT) was carried out to ensure that no stress relief took place owing to the presence of porosity. CT allows obtaining spatial and size pores distribution which helps in optimization of the SLM process. High tensile residual stresses were found at the lateral surface for samples in the as-built conditions. We observed that higher laser energy density during fabrication leads to lower residual stresses. Samples in released condition showed redistribution of the stresses due to distortion. T2 - 12th ECNDT 2018 CY - Göteborg, Sweden DA - 11.06.2018 KW - Additive manufacturing KW - Selective laser melting KW - Residual stress KW - Synchrotron X-ray diffraction KW - Ti-6Al-4V PY - 2018 UR - http://cdn.ecndt2018.com/wp-content/uploads/2018/05/ecndt-0213-2018-File001.pdf SP - 1 EP - 8 AN - OPUS4-45217 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bruno, Giovanni T1 - An assessment of bulk residual stress in selective laser melted in 718 N2 - Having been introduced almost two decades ago, Additive Manufacturing (AM) of metals has become industrially viable for a large variety of applications, including aerospace, automotive and medicine. Powder bed techniques such as Selective Laser Melting (SLM) based on layer-by-layer deposition and laser melt enable numerous degrees of freedom for the geometrical design. Developing during the manufacturing process, residual stresses may limit the application of SLM parts by reducing the load bearing capacity as well as induce unwanted distortion depending on the boundary conditions specified in manufacturing. The residual stress distribution in IN718 elongated prisms produced by SLM was studied non-destructively by means of neutron (bulk) and laboratory X-ray (surface) diffraction. The samples with different scanning strategies, i.e. hatching length, were measured in as-built condition (on a build plate) and after removal from the build plate. While surface stress fields seem constant for AB condition, X-ray diffraction shows stress gradients along the hatch direction in the RE condition. The stress profiles correlate with the distortion maps obtained by tactile probe measurements. Neutron diffraction shows bulk stress gradients for all principal components along the main sample directions. We correlate the observed stress patterns with the hatch length, i.e. with its effect on temperature gradients and heat flow. The bulk stress gradients partially disappear after removal from the baseplate. Together with surface scan utilizing a coordinate-measuring machine (CMM), it is possible to link the stress release to the sample distortion. We finally propose an explanation of those stress profiles based on the deposition strategy. T2 - ECRS10 CY - Leuven, Belgium DA - 09.09.2018 KW - Residual stress KW - Influence of rheology modifying admixtures on hydration of cementitious suspensions PY - 2018 AN - OPUS4-45997 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -