Tomas Bata University in Zlín
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The effect of 3D printing orientation on tensile behaviour and fracture mechanisms of Inconel 718
No full textThe manuscript aims to study the effect of 3D printing orientation on the tensile behaviour and fracture mechanisms of samples made of Inconel 718. Components of metals using additive manufacturing techniques are crucial in applications where safety, reliability, and trouble-free operation are essential. Therefore, it is vital to study and understand the behaviour of 3D-printed components under various loading types and predict potential failures. The EOS Nickel Alloy IN718 material sheet provides tensile properties of heat-treated samples (per AMS 5664 procedure) built exclusively in the Z direction. Consequently, the authors extended the investigation to include the tensile behaviour of 3D-printed samples in seven basic orientations within the 3D printing machine's workspace. For this purpose, the mechanical properties of Inconel 718 alloy samples manufactured using Direct Metal Laser Sintering (DMLS) technology were subjected to uniaxial tensile stress. The samples underwent heat treatment according to the AMS 5664 procedure, with solution annealing and aging temperatures determined using a pseudo-binary phase diagram calculated with Thermo-Calc® software. Post-tensile tests and fracture surface observations were conducted to identify the main failure modes. Microstructural and morphological analyses of 3D-printed INCONEL 718 samples were carried out using light optical microscopy (LOM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) textural analysis. Phase diagrams indicate expected phases such as γ-phase (FCC_A1), δ-phase (NbNi3_D0A), γ’’-phase (Ni3Ti_D024), Laves phase (C14_Laves), and γ’-phase (FCC_L12). Solution annealing was performed above 940 °C while aging treatment was done at temperatures below 800 °C to allow precipitation of γ’ and γ’’ phases. The δ phase also forms during aging. Fractographic examination of the tensile fractures indicated a predominantly quasi-ductile failure mechanism, with fine-sized dimples observed. In the XZ-oriented samples, the measured yield strength was 11 % higher compared to the Z-oriented samples and the yield strength was more than 12 % higher. The difference in mechanical properties between the Z orientation (Rp0.2 = 1284 MPa and Rm = 1429 MPa) and the XZ orientation (Rp0.2 = 1436 MPa and Rm = 1613 MPa) can be mainly attributed to the texture in the XZ sample and its more equiaxed grain structure compared to the Z sample.Ministry of Education, Science, Research and Sport of Slovak Republic [APVV-19-0550, KEGA 032TUKE-4/2022, KEGA 042TUKE-4/2025
The use of low-frequency current fluctuations in measuring the mobility of holes in the MEH-PPV polymer
No full textA diagnostic method based on the evaluation of low-frequency current fluctuation spectra is presented. When measuring the current through a p-type MEH-PPV sample, the occurrence of fluctuation is observable which can be measured with an AC amplifier. A model has been proposed that proves that the fluctuations originate from the interaction between the valence band and the band gap traps. The mean value of the amplitudes of these fluctuations increases linearly with decreasing frequency with a slope from which the product of mobility and lifetime of current carriers µpτp = (9 ± 3) × 10−15 cm2V−1 was obtained. The hole lifetime of (0.27 ± 0.01) ns was evaluated from the luminescence relaxation using the time-correlated single photon counting (TCSPC) technique. The mobility value (3 ± 1) × 10−5 cm2 V−1s−1 calculated using the above methods was compared with the mobility 1.8 × 10−5 cm2 V−1s−1 determined by the CELIV method (Charge extraction by linearly increasing voltage) and good agreement was obtained.University Institute at Tomas Bata University in Zlin from the DKRVO funds; Centre of Polymer Systems from the DKRVO funds [RP/CPS/2024-28/007
Inelastic fluid models with an objective stretch rate parameter
No full textThis paper presents an extension to the Generalized Newtonian Fluid (GNF) model, where the effects of different flow modes can be discerned. While existing GNF models have proven valuable in simulating processes like molding and extrusion, they often struggle to differentiate between distinct flow modes such as planar extension and simple shear. To address this challenge, we propose a modified GNF model that integrates an objective flow-type parameter, aiming to refine flow characterization. Emphasis is placed on defining the flow-type parameter to be able to transcend viscometric flows, remain frame-indifferent, quantify deformation magnitude, and differentiate between diverse flow modes. Inspired by the new advances in vortex identification in turbulent flow, we introduce a new stretch rate tensor and a new stretch rate parameter that are derived from the real Schur form of the objective velocity gradient tensor. These elements are embedded into the constitutive modeling of non-Newtonian fluid flow. The resulting model is employed to fit polymer melt data from the literature, demonstrating excellent fitting to combined shear and extension data. The basic model uses 5 to 6 parameters for data fitting, and further enhancement may be achieved by incorporating other extracted information of the stretch rate tensor.National Science Foundation of USA [1927651]; Grant Agency of the Czech Republic [24-11442S
Gender inequality in adult education: a comparative study of four adult learning systems
Full text linkThis study explores gender-related inequality in participation in Adult Education and Training (AET) in four countries with vastly different adult learning systems and support measures for women’s AET. Our examination of the data from an original international survey conducted in 2022 has found that the participation of men and women clearly differs among types of AET. Despite the frequently reported equal gender participation rates, the presented findings show that men participate more in job-related and employer-sponsored non-formal education (NFE), while women manage to develop more general skills in non-job-related and non-employer-sponsored NFE. Furthermore, our findings reveal that the primary reasons for participation in NFE are remarkably similar between men and women and, therefore, cannot be used as a source of explanation for different participation patterns. In addition, the extent of gender inequality in job-related and employer-sponsored NFE across countries exhibits minimal variation. All this implies that countries with vastly different adult learning systems currently display a degree of similarity in gender inequality regarding NFE, which could be determined more by characteristics of the labor market than the welfare regime
Sheet forming via Limiting Dome Height (LDH) test: Influence of the application of lubricants, location and sheet thickness on the micro-mechanical properties of X8CrMnNi19-6-3
Full text linkThis work is concerned with forming, specifically deep drawing, and its influence on the micro-mechanical properties of sheet metal. In practice, there are several applications in which fractions can occur due to weak spots in the deep-drawn sheet metal, especially after long-term use. The deep drawing process was carried out on BUP–600 machines using the LHD (Limiting Dome Height) method, which uses a forming tool with a diameter of 100 mm and bead groove. Sheet metals X8CrMnNi19-6-3 (1.4376) with thicknesses of 1, 1.5, and 3 mm were selected for this process. To study the effect of a lubricant on the formability of the sheet metal, deep drawing without and with a lubricant was compared. An FEM analysis was conducted to identify critical points in the deep drawing process, and the results were later compared with real results. The analysis was conducted using the AutoForm program. The micro-mechanical properties of these points were subsequently examined. The specified points on the formed part showed significant differences in their micro-mechanical properties, suggesting a higher strength but also less resistance to fractures. The difference in micro-mechanical properties (indentation and Vickers hardness) in points that were not deep-drawn and points located in critical areas was up to 86%. Significant changes in behavior were found in the indentation modulus and plastic/elastic deformation work as well. This study demonstrates the significant effect of the use of a lubricant in achieving the deep drawing of the sheet metal. The application of a lubricant resulted in a 33% increase in drawing range compared to drawing without lubrication. This study has a significant influence on the deep drawing of sheet metals in practice, showing the fundamental influence of the lubricant on the drawing process and also showing the problem of critical points that need to be eliminated.Project TBU in Zlin Internal Grant Agency [IGA/FT/2024/003]TBU in Zlin Internal Grant Agency, (IGA/FT/2024/003
Titanium-immobilized layered HUS-7 silicate as a catalyst for photocatalytic CO2 reduction
Full text linkUtilizing photocatalytic CO2 reduction presents a promising avenue for combating climate change and curbing greenhouse gas emissions. However, maximizing its potential hinges on the development of materials that not only enhance efficiency but also ensure process stability. Here, we introduce Hiroshima University Silicate-7 (HUS-7) with immobilized Ti species as a standout contender. Our study demonstrates the remarkable photocatalytic activity of HUS-7 in CO2 reduction, yielding substantially higher carbonaceous product yields compared to conventional titanium-based catalysts TS-1 and P25. Through thorough characterization, we elucidate that their boosted photocatalytic performance is attributed to the incorporation of isolated Ti species within the silica-based precursor, serving as potent photoinduced active sites. Moreover, our findings underscore the crucial role of the Ligand-to-Metal Charge Transfer (LMCT) process in facilitating the photoactivation of CO2 molecules, shedding new light on key mechanisms underlying photocatalytic CO2 reduction.Large Research Infrastructure ENREGAT [LM2023056]; Czech Science Foundation [GA CR 21-24268 K]; Research Infrastructure NanoEnviCz - Ministry of Education, Youth and Sports of the Czech Republic [LM2023066]; European Union's Horizon 2020 project SAN4Fuel [HORIZON-WIDERA-2021-ACCESS-03-01: 101079384]; European Union under the REFRESH - Research Excellence For Region Sustainability and High-tech Industries project via the Operational Programme Just Transition [CZ.10.03.01/00/22_003/0000048]; Grant program "Support for Science and Research in the Moravia-Silesia Region 2022" [RRC/12/2022]; JSPS KAKENHI Grant [22H01868]European Union's Horizon 2020 project SAN4Fuel, (101079384, HORIZON‐WIDERA‐2021‐ACCESS‐03‐01); Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT, (LM2023066); European Commission, EC, (CZ.10.03.01/00/22_003/0000048); Grantová Agentura České Republiky, GAČR, (GA CR 21‐24268 K); Japan Society for the Promotion of Science, JSPS, (22H01868
Flow-induced defects during metal injection molding: Role of powder morphology
No full textOwing to the quality issues of highly filled compounds used in metal injection molding, the current research is focused on intercepting flow-induced inhomogeneities in multiphase compounds resulting from the segregation of metal powder particles from (typically) three/four-component polymer binders, resulting in an unacceptable porosity of the final sintered metal parts. A recently developed nondestructive approach for quantifying the extent of these flow-induced defects was employed to study the effect of the size and shape of water- and gas-atomized 17-4PH stainless steel powders on segregation. This method combines scanning electron microscopy/energy dispersive x-ray spectroscopy with an in-house analytical tool. The results show a higher tendency of coarser particles (D-50 of 20 mu m) for flow-induced defects, while an irregular shape (water-atomized particles) reduces this unwanted phenomenon.Ministerstvo Scaron;kolstv, Mldezcaron;e a Tecaron;lovchovy10.13039/501100001823 [RP/CPS/2024-28/005, RP/CPS/2024-28/003]; Ministry of Education, Youth and Sports of the Czech Republic-DKRV
Assessing pediatric gait symmetry through accelerometry and computational intelligence
Full text linkThis paper focuses on the use of wearable sensors to acquire and process motion data, which is essential for monitoring physiological movement and identifying gait disorders. It is particularly relevant in pediatrics, neurology, and rehabilitation. The research evaluates body motion symmetry in children using accelerometric data, taking into account factors such as age, diagnosis, and gender. Signals were recorded from 35 children (average age 10.8 years) using mobile sensors and were analyzed using digital signal processing techniques and classification methods. The proposed methodology includes data acquisition by smartphone sensors, wireless data export to a remote drive, and data processing through a graphical user interface. The highest classification accuracy of walking features, at 92.0%, was achieved with a two-layer neural network. The findings underscore the effectiveness of these tools in rehabilitation, fitness monitoring, and neurological studies.Ministry of Health, Czech Republic - conceptual development of research organization [00064190]; European Union (EU) [CZ.02.01.01/00/22_008/0004590]; Operational Programme Johannes Amos Comenius - European Structural and Investment Funds; Czech Ministry of Education, Youth and Sports [CZ.02.01.01/00/22_008/0004596]Ministry of Health, MOH; Fakultní Thomayerova nemocnice, FTN, (00064190); European Commission, EC, (CZ.02.01.01/00/22-008/0004590); Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT, (CZ.02.01.01/00/22-008/0004596, SENDISO - CZ.02.01.01/00/22_008/0004596
H∞ loop-shaping continuous-time controller design for nonlinear HDD systems: A reduced-order approach using Hankel-Norm approximation
Full text linkThis study presents the development and examination of a streamlined H∞ loop-shaping continuous-time controller tailored for nonlinear Hard Disk Drive (HDD) systems. Using the Hankel-norm approximation technique, the complexity of the controller is systematically reduced, emphasizing preserving the system's efficacy while enhancing computational efficiency. The dynamics of the HDD system and the performance of the proposed controller are investigated through MATLAB simulations. The effectiveness of the controller is quantitatively measured by employing the ITAE (Integral of Time multiplied by Absolute Error) criterion. The results indicate that a controller of the 10th-order provides a desirable compromise between maintaining robust control and minimizing disturbances and noise without significant loss in performance. This method illustrates the capacity for implementing more straightforward controllers in complex HDD systems, paving the way for their application in precision-critical industrial settings.Internal Grant Agency of Tomas Bata University in Zlin [IGA/CebiaTech/2024/001]Univerzita Tomáše Bati ve Zlíně, UTB, (IGA/CebiaTech/2024/001); Univerzita Tomáše Bati ve Zlíně, UT
Unraveling the internal drivers of pharmaceutical company performance in Europe: A DEMATEL analysis
Full text linkResearch background: Internal business factors are vital to how a company achieves its goals. The present study of internal drivers of pharmaceutical company performance is very insightful, as it has the potential to boost further competitiveness, it may allow health authority personnel to have guidelines to make strategic decisions, as well as inspire investor confidence, ensure regulatory compliance and performance benchmarking, and support talent acquisition and retention. In addition, it can identify the important internal factors that need to receive more priority