Iskanje po katalogu digitalne knjižnice

Opis: The main aim of the study was to analyse the strain rate sensitivity of the compressive deformation response in bulk 3D-printed samples from 316L stainless steel according to the printing orientation. The laser powder bed fusion (LPBF) method of metal additive manufacturing was utilised for the production of the samples with three different printing orientations: 0◦ , 45◦ , and 90◦ . The specimens were experimentally investigated during uni-axial quasi-static and dynamic loading. A split Hopkinson pressure bar (SHPB) apparatus was used for the dynamic experiments. The experiments were observed using a high-resolution (quasi-static loading) or a high-speed visible-light camera and a high-speed thermographic camera (dynamic loading) to allow for the quantitative and qualitative analysis of the deformation processes. Digital image correlation (DIC) software was used for the evaluation of displacement fields. To assess the deformation behaviour of the 3D-printed bulk samples and strain rate related properties, an analysis of the true stress–true strain diagrams from quasi-static and dynamic experiments as well as the thermograms captured during the dynamic loading was performed. The results revealed a strong strain rate effect on the mechanical response of the investigated material. Furthermore, a dependency of the strain-rate sensitivity on the printing orientation was identified.
Ključne besede: 3D printing, laser powder bed fusion, 316L stainless steel, printing direction, split Hopkinson pressure bar
Objavljeno v DKUM: 20.03.2025; Ogledov: 0; Prenosov: 2
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Opis: The increasing adoption of 2D/3D laser line sensors in industrial and research applications necessitates accurate and efficient simulation tools for tasks such as surface inspection, dimensional verification, and quality control. This paper presents a novel algorithm developed in MATLAB for simulating the measurements of any 2D/3D laser line sensor on STL CAD models. The algorithm uses a modified fast-ray triangular intersection method, addressing challenges such as overlapping triangles in assembly models and incorporating sensor resolution to ensure realistic simulations. Quantitative analysis shows a significant reduction in computation time, enhancing the practical utility of the algorithm. The simulation results exhibit a mean deviation of 0.42 mm when compared to real-world measurements. Notably, the algorithm effectively handles complex geometric features, such as holes and grooves, and offers flexibility in generating point cloud data in both local and global coordinate systems. This work not only reduces the need for physical prototyping, thereby contributing to sustainability, but also supports AI training by generating accurate synthetic data. Future work should aim to further optimize the simulation speed and explore noise modeling to enhance the realism of simulated measurements.
Ključne besede: 2D/3D laser line sensor, profilometry, simulation, point cloud, measurement generation, STL, Matlab
Objavljeno v DKUM: 10.01.2025; Ogledov: 0; Prenosov: 9
Celotno besedilo (8,99 MB)
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Opis: The synchronization of chaotic systems has garnered considerable attention across various fields, including neuroscience and physics. Particularly in these domains, synchronizing physical systems such as laser models is crucial for secure and rapid information transmission. Consequently, numerous studies investigate the synchronizability of different laser networks by establishing logical network frameworks. In this study, we employed a minimal universal laser (MUL) model designed to capture the essential dynamics of an actual laser model within just three dimensions. Within the network model of MUL systems, we introduced the linear diffusive function of neighboring nodes' fast variables into the feedback term of the lasers, with models arranged in a global network structure. Our examination of synchronization within the constructed MUL network utilized master stability functions and the time-averaged synchronization error index. The findings suggest that while the network fails to achieve complete synchrony, it exhibits various synchronization phenomena, including cluster synchronization, chimera states, extreme events, and multistability. These results shed light on the complex dynamics underlying the synchronization of chaotic systems in networked environments, offering insights relevant to numerous applications across diverse fields.
Ključne besede: minimal universal laser model, synchronization, extreme events
Objavljeno v DKUM: 16.12.2024; Ogledov: 0; Prenosov: 4
Celotno besedilo (5,68 MB)
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Opis: The selective laser melting (SLM) process for manufacturing metals continues to be challenging in terms of achieving the maximum metallurgical properties that the process can provide. There are a variety of manufacturing parameters in the process that have individual characteristics, and when combined with other variables, the characteristics can be varied. However, in this study, the two most important manufacturing parameters, namely build direction and laser power, were considered to investigate their effects on density and tensile properties. Previously, the best scanning speed, hatch spacing, and layer thickness were determined, which directly affect the volumetric energy density in the SLM process. In this study, three different orientations and three different laser powers were selected, namely the X, Y, and Z directions and 55 W, 75 W, and 95 W laser power, respectively. Significant differences in product density were observed for the samples fabricated in the different orientations and with the different laser powers. The specimens fabricated in the Z direction always exhibit higher strength and ductility, which are significantly different from the specimens fabricated in the X and Y directions, while the laser power was 75 W and 95 W, respectively
Ključne besede: cobalt-chromium alloy, orientation, density, tensile strength, ductility, selective laser melting
Objavljeno v DKUM: 25.09.2024; Ogledov: 0; Prenosov: 8
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Opis: It is well known that Selective Laser Melting (SLM) does not provide the same mechanical properties in all directions of the part. This is due to the microstructural grain orientation and pore shape in SLM products. Therefore, depending on the direction of the pressure applied to the SLM product, a different manufacturing orientation is required to achieve the best mechanical properties. Changing the microstructural grain orientation is difficult through SLM, but a process to reduce the size and number of the pores can be discovered through different combinations of manufacturing parameters. In prosthodontics, pressure is usually applied in the vertical direction, which leads to compression and bending of crowns with bridges. The compressive load can be easily absorbed in the crowns, but the bending force has a significant effect here. Therefore, a product with high tensile strength and high ductility is needed to survive longer. Considering these requirements, this study determined the best parameters for laser processing by SLM method to reduce porosity and improve mechanical strength and ductility of Co-CrW-Si alloy products. The result is a relative product density of 100% for cubic specimens and a yield strength, ultimate tensile strength, and elongation at break of the tensile specimens of 900 MPa, 1200 MPa, and 15%, respectively, obtained in specimen build-up in the Z direction with a laser power of 60 W and a scanning speed of 450 mm/s. Eventually, the best orientation for the production of dental prosthetic elements using the SLM process was determined.
Ključne besede: cobalt-chromium alloy, dental implant, density, tensile strength, ductility, selective laser melting
Objavljeno v DKUM: 03.07.2024; Ogledov: 78; Prenosov: 12
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