TY - JOUR A1 - Andrade, C. A1 - Saucedo, L. A1 - Rebolledo, N. A1 - Cabeza, S. A1 - Meinel, Dietmar T1 - X-Ray computed tomography and traditional analysis of a capillary absorption test in cement pastes N2 - Water absorption testing has the attraction of being simple, relatively quick and use water as a fluid which is the key substance in the possible concrete deterioration. However, in spite of the advantages its application has remained empirical, except for the testing of resistance to frost, through the identification of the critical degree of saturation. Rilem TC-116 studied this test, among others, for the characterization of concrete resistance against transport through the concrete pore network. Results indicated a low discriminating ability of the absorbency for qualifying concrete resistance and then, it seemed necessary to try to move forward by making the link between the absorption testing and the concrete pore microstructure. In the present work, thanks to the X-Ray computed tomography, it is described the evolution of the water front in three paste-specimen with different w/c ratios (different pore radius distributions). The observations allowed us to deduce that all the pores start to fill simultaneously, but the bigger ones fill quicker and rise less. The saturation degree is measured along the height of the sample, showing that each pore size has a different rate which becomes constant after the first hour. Washburn’s equation was applied to the progressive advance of the water front, resulting in a pore radius much smaller than the one expected. KW - Capillary absorption KW - Pore size distribution KW - X-ray CT KW - Gravimetry PY - 2020 DO - https://doi.org/10.1016/j.cemconcomp.2020.103634 VL - 113 SP - 103634 PB - Elsevier Ltd. CY - London AN - OPUS4-51487 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Orth, Anthony T1 - Sensitivitätstest für ausgewählte X-Ray CT Prüfkörper N2 - Industrial X-Ray computed tomography (XCT) is an alternative procedure to tactile coordinate measuring machines (CMM) for dimensional measurement as it has the advantage to be able to measure internal and external features. However, the uncertainty determination according to the standard VDI/VDE 2630 Part 2.1 is both complex and resource consuming. The procedure could be simplified with the help of computer simulations if a suitable digital replica of the XCT machine is available. The project CTSimU2 has the aim of establishing a guideline for evaluating the applicability of such a digital replica. In this context, the work presented here focuses on: determining the sensitivity of two specimens, on several modelling parameters; determining the significance of the modelled parameters; and estimating the sensitivity of the specimens measurands. The approach was to determine the effects of selected parameters and parameter interactions on dimensional measurands of the specimens by simulation. These effects were determined by varying the parameters in accordance with a D-optimal experimental design, with 83 runs for 10 parameters. The measurands were distances, flatness of fitted planes, cylindricities of fitted cylinders, and testing of modular transfer function on edges. By definition the effects are linked to the coefficients of the statistical model – multiple linear regression – related to the design criterion. The results yielded good models with high regression coefficients. The models for distances were dominated by the geometrical parameters, whereas parallelism and flatness responded more to x-ray parameters. The results have shown that both specimens are necessary to test the digital replica. T2 - DGZfP Jahrestagung 2024 CY - Osnabrück, Germany DA - 06.05.2024 KW - X-ray CT KW - Dimensional Measurements KW - Simulation KW - Specimen Sensitivity KW - DoE PY - 2024 AN - OPUS4-61797 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mishurova, Tatiana A1 - Fritsch, Tobias A1 - Jahn, Anne A1 - Pavasaryte, Lina A1 - Bruno, Giovanni T1 - Quantitative surface quality evaluation by X-ray Computed Tomography N2 - The poor surface quality is one of the challenges in powder based additive manufacturing (AM) techniques. It limits the application of the components in as-manufactured condition and requires the post-processing machining techniques, increasing costs and diminishing the advantage of the free form fabrication. It is important to characterize the surface roughness of the part as it might affect the tolerances and the mechanical behavior of the material. For the AM components the usage of classic characterization techniques becomes very challenging and even impossible, when internal channels, fine and complex shapes structures are under investigation. In such cases, X-ray Computed Tomography (XCT) is the only tool to evaluate the structure inside nondestructively. In this work, the application of surface quality analysis workflow using high-resolution XCT is presented. The analysis of surface topography includes the quantitative characterization of “re-entrant” surface features. This characterization is based on the evaluation of the triangulated surface generated based on the XCT data and was compared with conventional surface roughness parameters (e.g., Sa and Sz). The strength of the presented workflow is the application on arbitrary surfaces without geometrical limitations allowing real as-build investigation. This will be discussed on the example of both, simple cylindrical struts to present the principals, and the application to the Triply Periodic Minimal Surface (TPMS) structures. The analysis of the struts allows conclusions about the influence of down-skin and up-skin on surface quality. The results indicate that the surface quality is a factor of 2 worse for a build angle of 30° compared to an up-right build (90°). The investigation of TPMS structures is focused on the optimization of process parameter of geometrically complex samples regarding the surface quality. The challenge was an automated and user-independent comparison of several TPMS structures. The correlation of surface quality with process parameters (e.g., Laser power, laser velocity) is presented. T2 - ASTM ICAM 2024 CY - Atlanta, GA, USA DA - 28.10.2024 KW - Additive manufacturing KW - X-ray CT KW - Surface texture PY - 2024 AN - OPUS4-61515 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fardan, Ahmed A1 - Fazi, Andrea A1 - Peng, Ru Lin A1 - Mishurova, Tatiana A1 - Thuvander, Mattias A1 - Bruno, Giovanni A1 - Brodin, Håkan A1 - Hryha, Eduard T1 - Fine-Tuning Melt Pools and Microstructures: Taming Cracks in Powder Bed Fusion—Laser Beam of a non-weldable Ni-base Superalloy N2 - Powder Bed Fusion – Laser Beam (PBF-LB) of high γ’ strengthened Ni-base superalloys, such as CM247LC, is of great interest for high temperature applications in gas turbines. However, PBF-LB of CM247LC is challenging due to the high cracking susceptibility during PBF-LB processing (solidification cracking) and heat treatment (strain age cracking, mostly caused by residual stresses). This study focuses on understanding the impact of process parameters on microstructure, residual stresses and solidification cracking. Laser power (P), speed (v) and hatch spacing (h) were varied while the layer thickness (t) was fixed. The melt pool size and shape were found to be key factors in minimizing solidification cracking. Narrower and shallower melt pools, achieved using a low line energy density (LED = P/v ≤ 0.1 J/mm), gave low crack densities (0.7 mm/mm2). A tight hatch spacing (h = 0.03 mm) resulted in reduced lack of fusion porosity. Electron backscatter diffraction investigations revealed that parameters giving finer microstructure with 〈100〉crystallographic texture had low crack densities provided they were processed with a low LED. Atom probe tomography elucidated early stages of spinodal decomposition in the as-built condition, where Cr and Al cluster separately. The extent of spinodal decomposition was found to be affected by the LED and the hatch spacing. Samples with low LED and small hatch spacing showed higher degrees of spinodal decomposition. X-ray diffraction residual stress investigations revealed that the residual stress is proportional to the volumetric energy density (VED = P/(v. h. t)). Although low residual stresses can be achieved by using low VED, there is a high risk of lack of fusion. Hence, other parameters such as modified scan strategy, build plate pre-heating and pulsed laser mode, must be further explored to minimize the residual stresses to reduce the strain age cracking susceptibility. KW - Additive manufacturing KW - X-ray CT KW - Non-weldable superalloy KW - Solidification cracking PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-597340 DO - https://doi.org/10.1016/j.mtla.2024.102059 SN - 2589-1529 VL - 34 IS - 102059 SP - 1 EP - 16 PB - Elsevier B.V. AN - OPUS4-59734 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Voloskov, Boris A1 - Mishurova, Tatiana A1 - Evlashin, Stanislav A1 - Bruno, Giovanni A1 - Sergeichev, Ivan T1 - Influence of artificial and process-induced defects on very high cycle fatigue characteristics of 316L stainless steel produced by laser powder bed fusion N2 - This study investigates the impact of artificially embedded defects on the very high cycle fatigue (VHCF) of 316L stainless steel produced by laser powder bed fusion (PBF-LB) technology. Each specimen contains a single embedded artificial defect of 180 μm or 350 μm in diameter, positioned at specific distances from the surface (ranging from 350 μm to 1200 μm). The defect position and size are quantified by X-ray computed tomography. Following VHCF testing, the fracture surfaces of the specimens are examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) with electron diffraction analysis. The results demonstrate that the fracture surfaces predominantly display a fish-eye fracture type, with a fine granular area (FGA) surrounding the internal defects, typical for VHCF. The FGAs dimensions including thickness are estimated by means of microscopy analysis. However, despite the presence of relatively large artificial defects, cracks sometimes initiate from much smaller process-induced defects closer to the surface than the artificial ones. In conclusion, our study quantifies the relationship between the probability of crack initiation from artificial defects and the distance of the artificial defect from the specimen’s surface. KW - Additive manufacturing KW - X-ray CT KW - Porosity PY - 2025 DO - https://doi.org/10.1016/j.msea.2024.147571 VL - 920 SP - 1 EP - 13 PB - Elsevier B.V. AN - OPUS4-62117 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -