CTU Open Journal Systems (Czech Technical University, Prague / České vysoké učení technické v Praze)
Not a member yet
4735 research outputs found
Sort by
NMM 2023 Nano & Macro Mechanics
No full textThe 14th conference Nano & Macro Mechanics was held in Prague, in September 14, 2023.
The main objective of the conference is to bring together researchers, students and engineers devoting their work to comuting and experimental mechanics in different areas of engineering applications on a common platform.
The conference key topics were following:
Testing of buildings materials at the nano, micro, mezzo and macro levels.
Destructive and non-destructive methods for determining the mechanical properties of building materials.
Relationships between material parameters.
Computational and experimental dynamics and mechanics.
Material research for steel, buildings materials, glass, woods, textiles, and composites.
Analyses of constructions.
Computational methods for analyses of constructions and materials.
Scientific comittee:Tomáš PlachýPavel TesárekPavel PadevětPetr BittnarAleš JíraJan VorelBořek PatzákMichal Šejnoha
Local organizing comittee:Petr BittnarTomáš PlachýPavel PadevětPavel TesárekOndřej ZobalZdeněk Prošek
Guarantor of the peer review process:Pavel Padevět
Guarantor of the language editing:Tomáš Plach
Laboratory verification of the properties of recycled fine aggregates and the effect of different replacement percentages on concrete properties
Get PDFThis research work deals with the issue of laboratory testing of commonly available recycled fine aggregates, namely concrete recyclate, mixed recyclate and brick recyclate. Their geometrical properties: granulometric composition and fine particle content, including physical properties: bulk density and water absorption are investigated. The tests themselves are carried out according to available standards, which are currently mainly standards for testing natural aggregates, and it is necessary to assess the suitability of these tests for recycled aggregates as well. The results found for concrete recyclates confirm the use of these standards to obtain the properties mentioned, but the bulk density and absorption tests are inconclusive in the case of mixed and brick recyclates. Subsequently, test concrete specimens were produced in which natural fine aggregate and concrete recyclate were substituted at 33, 66 and 100 %. A series of tests were performed on the hardened concrete: bulk density, absorption, porosity and compressive strength. From the results obtained, the use of concrete recyclate in concretes with the replacement of natural fine aggregate at 33% is suitable, without a significant reduction in the observed properties
Substrate effect in the evaluation of elastic modulus of thin PVD coatings from nanoindentation
Get PDFThe comparison of nanoindentation results on reactive HiTUS TiZrHf+ME-Ny (ME = Nb, V, Ta and VNbTa) and reactive DCMS NbMoTaW coatings showed that the influence of substrate stiffness is still not fully eliminated in the evaluation of indentation modulus. To obtain comparable results by keeping the systematic error resulting from the existing evaluation procedures the same, nanoindentation should be performed using the same test parameters, a method for depth profile acquisition, a data evaluation procedure, and coatings with similar thicknesses on the same type of substrate. Applying these rules to nanoindentation on TiZrHf+ME-Ny coatings showed that the addition of ME = Nb, V, Ta, and VNbTa caused some degradation of mechanical properties indicating negligible or even negative “cocktail effect”
Estimation of mechanical properties of neutron-irradiated 08Ch18N10T steel from hardness testing
Get PDFThrough-thickness Vickers hardness of a neutron-irradiated small segment of the core barrel made from 08Ch18N10T austenitic stainless steel was characterized experimentally and results were compared to ones simulated numerically with assumption of Ludwik’s form of hardening equation and neutron dose dependent material parameters according to work of Sorokin. Simulated values of hardness trace the lower bound of scattered experimental data. Based on the same material input data and on the correlation with measured hardness profile, increase of the material yield strength of the core barrel due to reactor operation was estimated
Analysis on the effect of buried depth-initial water content of the tunnel in expansive rock
Get PDFThere are countless engineering disasters induced by expansive strata in the tunnel project. Nowadays, most of the research focuses on the basic characteristics of expansive rock and soil, while the influence about coupling buried depth and different initial water content of surrounding rock on the tunnel lining is still rarely involved. Based on the principle of temperature and humidity equivalence, this paper discusses the behavior of rock as well as the mechanical properties of lining under the interaction of different buried depth and initial water content by using FLAC3D numerical simulation. It was found that the initial water content show an obvious effect on the evolution about the plastic area of rock compared with the buried depth of the tunnel. For shallow tunnels with a water content of less than 10 %, the plastic zone of the vault will penetrate to the surface after water absorption and expansion. Under the coupling effect, buried depth inhibits the development of the plastic zone to a certain extent. For different initial water contents of the surrounding rock, the displacement of the tunnel adds with the burial depth. The swelling of rock will significantly reduce the safety of the primary support, and when the burial depths of the tunnel increase to 150 m, the security coefficients of some primary support structures are less than 2, which does not meet the need in standard. The safety factor of secondary support is mainly influenced by the expansion force, not the ground pressure (represented by buried depth). The findings may be valuable reference for the analysis as well as evaluation of the security as well as stability of tunnels in expansive mudstone
UTILIZATION OF 3D SCANNING IN BURN ANALYSIS AND IDENTIFICATION
Get PDFEffective burn scar treatment requires objective measurement of burn severity and progression, and 3D scanning technologies could offer a valuable alternative to the current clinical assessments. This article discusses the use of 3D scanning to determine the area and extent of burns. The study involves a comparison of twelve burns in six patients using two CAD software. The article deals with the methodology of scanning burns, and subsequently describes in detail the methodology of determining the area of burns from a 3D scan. Methodologies for burn scanning and determining burn area from 3D scans were detailed, emphasizing the innovation\u27s potential in surpassing traditional assessment methods like the Rule of nine and Palm method estimation. Twelve burns were scanned at least twice, allowing comparison of the burn area before and after a certain period of healing. The study revealed that 3D scanning provides an accurate approach to measuring burn areas, with minimal differences observed between software. Meshmixer software emerged as the preferred tool due to its intuitive features, underscoring the potential of 3D scanning to improve burn assessment and treatment planning. This approach enables the use of 3D scans to determine individual treatment according to the progression of healing, and at the same time opens up the possibilities of using 3D scans to design burn orthoses
Optical emission spectroscopy of breaking arc plasma between consumable electrodes
Get PDFThe investigation focuses on the optical emission spectroscopy of plasma generated by breaking arc between single-component Cu and composite Cu-W electrodes manufactured using shock sintering technology at temperature of 750°C. The electrodes were subjected to arc currents of 4, 50, and 104 A. Optical emission spectroscopy with high spectral and temporal resolution was employed to investigate the plasma with copper and tungsten vapour admixtures. The temporal evolution of temperature in the plasma was determined by the Boltzmann plot technique based on the emission intensities of Cu I spectral lines. Temporal evolution of electron densities were determined from the full width at half maximum of Cu I 515.3 nm spectral line. These initial plasma parameters integrated over the volume of breaking arc were utilized to calculate the temporal evolution of plasma compositions and contents of metal vapours admixtures in discharge gap
Drivers, instruments and challenges of knowledge and technology transfer in the automotive sector
Get PDFThis study comprehensively analyzes the drivers, instruments, and challenges that facilitate knowledge and technology transfer (KTT) in the automotive sector. The review was conducted with a focus on the regions of the Czech Republic and the German Free State of Saxony. It examines the evolving landscape of the automotive industry from a KTT perspective, driven by motivators of the three key stakeholders: government, academia, and the industry. The study explores how KTT expedites the adoption of safer, cleaner, more economical, and sustainable technologies in this sector. Key instruments from KTT intermediaries are highlighted, and their challenges and obstacles are discussed. A best practice case study involving the interplay of the three stakeholders is presented
ELICITATION WITHIN EHTA: POTENTIAL EFFICACY OF MELATONIN MEDICATION FOR STEMI PATIENTS WITH DETECTED HIGH RISK OF REPERFUSION VENTRICULAR FIBRILLATION DURING PCI
Get PDFPatients with acute ST-segment elevation myocardial infarction (STEMI) have a high risk of ventricular fibrillation. The aim of the study is to determine an unknown parameter of the new diagnostic cardiology technology model created within eHTA, effectiveness of intravenous administration of high doses of melatonin (4mg/kg) before/during PCI as protective medication in STEMI patients with a diagnosed by new technology high risk of ventricular fibrillation at reperfusion using expert elicitation. Ten experts took part in the elicitation and filled out prepared questionnaire, which included experimental evidence for antiarrhythmic action of melatonin, including cellular mechanisms. They expressed their opinions on the potential effectiveness of medication using numerical method and also answered questions about the suitability of the dosage, adverse effects and the risk-benefit ratio. Experts\u27 answers to the main research question were weighted based on their experience. Elicitation revealed the effectiveness value of 71.82% for the tested medication. Eighty percent of experts agreed that the dose is adequate, that side effects will be minimal, and that the benefits of such therapy outweigh possible risks. Results of this study will be applied for eHTA of novel diagnostic technology in cardiology and will help its manufacturer to evaluate the clinical effectiveness of the technology, find the right direction to complete the design and development of medical device, achieve optimal efficiency, present the concept and find investors, prepare for clinical evaluation, CE certification and inclusion to reimbursement system
Tribo-technological features of laser powder bed fusion process: scratch and wear resistance of AlSi10Mg aluminium alloy
Get PDFMechanical systems, regardless of their complexity, very often require that different parts must move relative to each other by sliding their surfaces, therefore appropriate tribological properties are needed. This request appears particularly evident for components fabricated through Metal Additive Manufacturing processes, due to their typical high surface roughness. In the current study, the Laser Powder Bed Fusion technique with optimized parameters is used to produce samples made of AlSi10Mg alloy. Their tribo-technological properties are investigated through progressive load scratch and dry ball-on-plate wear tests. Along with a global characterization, a local analysis has been performed to identify any variations induced by the building direction. The friction coefficient and the wear rate are generally higher than as-cast specimens. Finally, local trends suggest that the central parts of the samples average offer higher resistance to wear and scratch than the outer areas