ÚK-odbor reverzního inženýrství a aditivních technologií

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Comparative analysis of microstructure, mechanical, and corrosion properties of biodegradable Mg-3Y alloy prepared by selective laser melting and spark plasma sintering
(KeAi Communications, 2024-04-27) Minárik, Peter; Zemková, Mária; Šašek, Stanislav; Dittrich, Jan; Knapek, Michal; Lukáč, František; Koutný, Daniel; Jaroš, Jan; Král, Robert
This work explored possibilities of biodegradable magnesium alloy Mg-3Y preparation by two modern powder metallurgy techniques - spark plasma sintering (SPS) and selective laser melting (SLM). The powder material was consolidated by both methods utilising optimised parameters, which led to very low porosity ( -0.3%) in the SLM material and unmeasurably low porosity in the SPS material. The main aim of the study was the thorough microstructure characterisation and interrelation between the microstructure and the functional properties, such as mechanical strength, deformability, and corrosion resistance. Both materials showed comparable strength of -110 MPa in tension and compression and relatively good deformability of -9% and -21% for the SLM and SPS materials, respectively. The corrosion resistance of the SPS material in 0.1 M NaCl solution was superior to the SLM one and comparable to the conventional extruded material. The digital image correlation during loading and the cross-section analysis of the corrosion layers revealed that the residual porosity and large strained grains have the dominant negative effect on the functional properties of the SLM material. On the other hand, one of the primary outcomes of this study is that the SPS consolidation method is very effective in the preparation of the W3 biodegradable alloy, resulting in material with convenient mechanical and degradation properties that might find practical applications. (c) 2024 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ) Peer review under responsibility of Chongqing University
DoE Approach to Setting Input Parameters for Digital 3D Printing of Concrete for Coarse Aggregates up to 8 mm
(MDPI, 2023-04-27) Vespalec, Arnošt; Podroužek, Jan; Koutný, Daniel
This paper is primarily concerned with determining and assessing the properties of a cement-based composite material containing large particles of aggregate in digital manufacturing. The motivation is that mixtures with larger aggregate sizes offer benefits such as increased resistance to cracking, savings in other material components (such as Portland cement), and ultimately cost savings. Consequently, in the context of 3D Construction/Concrete Print technology (3DCP), these materials are environmentally friendly, unlike the fine-grained mixtures previously utilized. Prior to printing, these limits must be established within the virtual environment's process parameters in order to reduce the amount of waste produced. This study extends the existing research in the field of large-scale 3DCP by employing coarse aggregate (crushed coarse river stone) with a maximum particle size of 8 mm. The research focuses on inverse material characterization, with the primary goal of determining the optimal combination of three monitored process parameters-print speed, extrusion height, and extrusion width-that will maximize buildability. Design Of Experiment was used to cover all possible variations and reduce the number of required simulations. In particular, the Box-Behnken method was used for three factors and a central point. As a result, thirteen combinations of process parameters covering the area of interest were determined. Thirteen numerical simulations were conducted using the Abaqus software, and the outcomes were discussed.
Experimental study on time dependent behaviour of coarse aggregate concrete mixture for 3D construction printing
(Elsevier, 2023-04-20) Vespalec, Arnošt; Podroužek, Jan; Boštík, Jiří; Miča, Lumír; Koutný, Daniel
This experimental study analyses coarse aggregate-containing and coarse aggregate-free materials from the perspective of additive manufacturing. The primary objective is to identify, through a series of experiments, the fundamental equations that characterise material behaviour at early ages in order to formulate a digital material model. During the research, a previously unreported phenomenon, namely the contradictory development of Young's modulus and cohesion, was observed. In addition, the sensitivity of buildability to changes in material properties was discussed and demonstrated with a motivating example using a spatiotemporal simulation of 3Dprinted concrete.
Interface Behavior and Interface Tensile Strength of a Hardened Concrete Mixture with a Coarse Aggregate for Additive Manufacturing
(MDPI, 2020-11-15) Vespalec, Arnošt; NOVÁK, JOSEF; Kohoutková, Alena; Vosynek, Petr; Podroužek, Jan; Škaroupka, David; Zikmund, Tomáš; Kaiser, Jozef; Paloušek, David
3D concrete printing technology (3DCP) is a relatively new technology that was first established in the 1990s. The main weakness of the technology is the interface strength between the extruded layers, which are deposited at different time intervals. Consequently, the interface strength is assumed to vary in relation to the time of concrete casting. The proposed experimental study investigated the behavior of a hardened concrete mixture containing coarse aggregates that were up to 8 mm in size, which is rather unusual for 3DCP technology. The resulting direct tensile strength at the layer interface was investigated for various time intervals of deposition from the initial mixing of concrete components. To better understand the material behavior at the layer interface area, computed tomography (CT) scanning was conducted, where the volumetric and area analysis enabled validation of the pore size and count distribution in accordance with the layer deposition process. The analyzed CT data related the macroscopic anisotropy and the resulting crack pattern to the temporal and spatial variability that is inherent to the additive manufacturing process at construction scales while providing additional insights into the porosity formation during the extrusion of the cementitious composite. The observed results contribute to previous investigations in this field by demonstrating the causal relationships, namely, how the interface strength development is determined by time, deposition process, and pore size distribution. Moreover, in regard to the printability of the proposed coarse aggregate mixture, the specific time interval is presented and its interplay with interface roughness and porosity is discussed.
Microstructure of Selective Laser Melted Titanium Lattices and In Vitro Cell Behaviour
(Tanger, 2021-09-15) Hernandez Tapia, Laura Guadalupe; Carranza-Trejo, Azalia Mariel; Kashimbetova, Adelia; Tkachenko, Serhii; Koledová, Zuzana; Koutný, Daniel; Malý, Martin; Čelko, Ladislav; Montufar Jimenez, Edgar Benjamin
Selective laser melting (SLM) is a metal additive manufacturing technology that allows the fabrication of complex near-net-shape titanium parts. Among possible applications, titanium is important for the biomedical sector, in particular for orthopaedics due to its low elastic modulus, biocompatibility, high mechanical strength and corrosion resistance. Several studies show the structural properties and mechanical behaviour of titanium lattices that in parallel exhibited the porosity, mechanical strength and elastic modulus of trabecular bone. However, less attention has been devoted to study the biological response to titanium parts fabricated by SLM. Therefore, this work aimed to fabricate commercially pure titanium lattices by SLM and study the behaviour of bone-forming cells cultured on the lattices. The results show that Saos-2 osteoblast-like cells proliferated and covered the entire available surface of the titanium lattices becoming confluent and quiescent. The activity of alkaline phosphatase and the production of extracellular calcium deposits confirmed the growth of viable and mature osteoblasts. The cytocompatibility of the titanium lattices is an additional advantage that adds to the possibility to mimic the porosity and mechanical properties of bone by computer-aided design and subsequently implement the lattice fabrication by SLM, fitting the requirements of individual patients and, consequently, offering a broad range of new bone repair alternatives in orthopaedics. Keywords: selective laser melting, titanium, microstructure, osteoblast, cytocompatibility.

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