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Dynamics of a cantilever beam with piezoelectric sensor: Experimental study
Kolman, Radek; Kylar, Jaromír; Kotek, Vojtěch; Cimrman, Robert; Musil, Ladislav
2023 - anglický
Online and real-time sensing and monitoring of the health state of complex structures, such as air-craft and critical parts of power stations, is an essential part of the research in dynamics. Several types of sensors are used for sensing dynamic responses and monitoring response changes during the operation of critical parts of complex systems. The piezoelectric (PZ) materials belong to one group of electroactive materials, which transform mechanical deformation into an electrical response. For example, PZ ceramics or PVDF foils are employed for online sensing of the time history of mechanical deformation. Experimentally obtained response of a cantilever beam structure with a glued PZ sensor is the case of interest in this contribution. During the transient problem of the beam loaded by suddenly interrupted load due to the weight of a mass at the end of the beam, the time history of normal velocity at a point on the beam surface has been measured by a laser vibrometer and parallely, the output voltage on the PZ sensor has been measured by an electric device. The experimental data in the case of the first eigen-frequency is in good agreement with the value given by the formulae from the theoretical modeling of free vibration of a linear beam.
Klíčová slova:
dynamics of beam-like structure; piezo-electric material; sensing of dynamic response; structural Health Monitoring; laser vibrometer measurement
Dokument je dostupný na externích webových stránkách.
Dynamics of a cantilever beam with piezoelectric sensor: Experimental study
Online and real-time sensing and monitoring of the health state of complex structures, such as air-craft and critical parts of power stations, is an essential part of the research in dynamics. Several ...
Experimental and numerical investigation of the frequency-modal properties of the switch box
Zolotarev, Igor; Pešek, Luděk; Bula, Vítězslav; Šnábl, Pavel; Gabriel, Dušan; Mračko, Michal; Masák, Jan
2023 - anglický
The research is linked to increase of seismic resistivity of data board switch boxes. Therefore we deal with numerical modelling of the box for finding the hot spots and designing appropriate modifications. This paper deals with numerical and experimental frequency-modal properties of the switch box and mutual comparison for numerical model validation.
Klíčová slova:
modal analysis; natural frequencies; eigen-modes of vibration
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Experimental and numerical investigation of the frequency-modal properties of the switch box
The research is linked to increase of seismic resistivity of data board switch boxes. Therefore we deal with numerical modelling of the box for finding the hot spots and designing appropriate ...
Calibrated finite volume method-based simulation framework for laser shock peening
Isoz, Martin; Gruber, Pavel; Schmidt, Jaroslav; Kubíčková, Lucie; Štefan, Jan; Kaufman, Jan; Brajer, Jan; Gabriel, Dušan
2023 - anglický
Modern and highly competitive industry seeks components with high strength and fatigue resistance. Both of these properties may be improved by peening of the component surface and the standard peening processes, such as the shot peening, are widely used in both automotive and aerospace industries. The laser shock\npeening (LSP), i.e. hardening of the material surface by a laser-induced shock wave, is a modern alternative to the standard peening. Concurrently, the industrial applications of LSP are promoted by recently emerged affordable high power-density lasers. However, the nascent LSP applications are still mostly a trial-and-error\nprocesses based on an extensive experimental testing. Consequently, we focused on a highly application-driven development of a framework for LSP modeling, and the internal workings and results of which are the focus of the present contribution.
Klíčová slova:
laser shock peening; modeling; finite volume method; OpenFOAM
Dokument je dostupný na externích webových stránkách.
Calibrated finite volume method-based simulation framework for laser shock peening
Modern and highly competitive industry seeks components with high strength and fatigue resistance. Both of these properties may be improved by peening of the component surface and the standard peening ...
Mixing characteristics of a magnetically driven Rushton turbine in an unbaffled stirred tank reactor
Idžakovičová, Kristýna; Haidl, Jan; Gebouský, Ondřej; Isoz, Martin
2023 - anglický
The standard and well-researched stirred vessel configuration comprises a tank equipped with one or more impellers positioned in the vessel’s axis and multiple wall-mounted baffles preventing the central vortex creation. However, particular industries, such as biotechnology, have an increased need for a sterile environment that often results in the usage of atypical stirred vessel configurations. An example of a commonly equipped atypical stirred vessel is an unbaffled stirred tank with an eccentric magnetically driven impeller. However, there is only a little knowledge about the mixing characteristics of such designs. In this work, we list experimental results for both the standard and atypical stirred vessel configurations. Furthermore, we present a CFD model of the atypical configuration. The model is used to calculate its mixing characteristics that are subsequently compared against our experimental results. It is shown that for the liquid height (H) to the vessel diameter (T) ratio H/T ≲ 1.2, the characteristics of both the standard and atypical designs coincide. For higher liquid heights (i) the characteristics of the atypical design decrease dramatically, and (ii) the characteristics estimates based on approaches developed for the standard configuration become unreliable.
Klíčová slova:
stirred vessel; eccentric impeller; unbaffled tank; CFD; OpenFOAM; experiment
Dokument je dostupný na externích webových stránkách.
Mixing characteristics of a magnetically driven Rushton turbine in an unbaffled stirred tank reactor
The standard and well-researched stirred vessel configuration comprises a tank equipped with one or more impellers positioned in the vessel’s axis and multiple wall-mounted baffles preventing the ...
Engineering Mechanics 2023
Radolf, Vojtěch; Zolotarev, Igor
2023 - anglický
The proceedings contains papers presented at the 29th International Conference on Engineering Mechanics, which has been held in OREA Resort Devět Skal in Czech Republic under auspices of the Czech Society of Mechanics and being a part of IFTOMM (The International Federation for the Promotion of Mechanism and Machine Science) activities. As it corresponds with character of the conference, this proceedings consists of several topic oriented parts: Biomechanics, Fluid mechanics, Dynamics, Fracture mechanics, Mechatronics, Reliability of structures, Mechanics of solids, Technological processes, Thermodynamics. The volume represents a well-balanced overview of theoretical, numerical and experimental work on fundamental and applied studies.
Klíčová slova:
biomechanics; dynamics; mechatronics; fluid mechanics; mechanics of solids; fracture mechanics
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Engineering Mechanics 2023
The proceedings contains papers presented at the 29th International Conference on Engineering Mechanics, which has been held in OREA Resort Devět Skal in Czech Republic under auspices of the Czech ...
Přehledná dokumentace vrubů vyrobených technologií laserového vypalování do potrubních těles v rámci projektu TK01030108 (NEMENUS)
Štefan, Jan
2023 - český
Tato technická zpráva byla zpracována v rámci projektu DP_04_02_04: Výzkum aplikovatelnosti moderních SHM (Structural Health Monitoring) systémů pro zvýšení spolehlivosti a ekonomičnosti provozu jaderných elektráren (stávajících, nových i malých modulárních reaktorů). Účel této zprávy spočívá v přehledné dokumentaci zkušeností s technologií laserového vypalování, která byla v letech 2020 až 2022 úspěšně aplikována v rámci předchozího projektu TAČR TK01030108 (projekt NEMENUS) pro výrobu vrubů do potrubních zkušebních těles, a která může být dle předpokladů s výhodou využita také v experimentálním programu stávajícího projektu. Informace shromážděné v tomto dokumentu napomohou při specifikaci zadání poskytovateli této služby (spol. ATG, s. r. o.), a při optimalizaci parametrů laseru pro daný účel. This technical report has been prepared within the project DP_04_02_04: Research of applicability of modern SHM (Structural Health Monitoring) systems for increasing reliability and economic efficiency of nuclear power plant operation (existing, new and small modular reactors). The purpose of this report is to provide an overview documentation of the experience with laser technology, which has been successfully applied in the previous TAČR project TK01030108 (NEMENUS project, 2020 and 2022) for the production of notches into pipe test specimens, and which is expected to be advantageously used also in the experimental program of the current project. The information gathered in this document will help in the specification of the assignment to the provider of this service (ATG, s.r.o.), and in the optimization of the laser parameters for the purpose.
Klíčová slova:
material testing; high-cycle fatigue; laser technology
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Přehledná dokumentace vrubů vyrobených technologií laserového vypalování do potrubních těles v rámci projektu TK01030108 (NEMENUS)
Tato technická zpráva byla zpracována v rámci projektu DP_04_02_04: Výzkum aplikovatelnosti moderních SHM (Structural Health Monitoring) systémů pro zvýšení spolehlivosti a ekonomičnosti provozu ...
Measurements on Turbine Cascade KOBRA
Luxa, Martin; Hála, Jindřich; Šimurda, David
2023 - anglický
The report contains results and evaluation of aerodynamic measurement on a blade cascade representing the section imitating the conical stream line in the last rotor row of a gas trubine under considerable off-design condition. The research report contains detailed specifications of the measured model, overview of the results of the optical measurements (interferometry, schlieren method in Toepler configuration) and pneumatic measurements (traversing with five hole conical probe downstream the cascade).
Klíčová slova:
turbine cascade; turbine off-design condition; tarnsonic flow
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Measurements on Turbine Cascade KOBRA
The report contains results and evaluation of aerodynamic measurement on a blade cascade representing the section imitating the conical stream line in the last rotor row of a gas trubine under ...
The influence of first CNN layer initialization on training convergence
Krejsa, Jiří; Věchet, Stanislav; Chen, K.S.
2023 - anglický
During evaluation of convolution neural networks on the task of sign language single hand alphabet classification we have discovered that in small but not negligible number of cases the training of the network does not converge at all. This paper investigates the problem that we believe is independent of the application. While the true cause of training divergence was not discovered, we can offer the reader an easy solution from practical point of view – initialization of the first CNN layer using pretrained networks parameters.
Klíčová slova:
convolution neural networks; training; initialization
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
The influence of first CNN layer initialization on training convergence
During evaluation of convolution neural networks on the task of sign language single hand alphabet classification we have discovered that in small but not negligible number of cases the training of ...
Post-processing the results of the topology optimization with the level set technique
Ježek, Ondřej; Kopačka, Ján; Gabriel, Dušan
2023 - anglický
Topology optimization (TO) has come to the fore with the development of 3D printing. The most commonly used method is SIMP, a density-based approach, which outputs a per-element constant density field and thus requires post-processing to obtain the shape. Conventional post-processing methods extract optimized topologies in the form of brep models. It yields only C0 continuous geometries, which are usually not suitable for downstream applications such as prototyping, design validation, and design exploration. In this paper, we present a new post-processing method based on the level set principle that overcomes common post-processing issues, such as the lack of smoothness.
Klíčová slova:
topology optimization; post-processing; level-set; signed distance function
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Post-processing the results of the topology optimization with the level set technique
Topology optimization (TO) has come to the fore with the development of 3D printing. The most commonly used method is SIMP, a density-based approach, which outputs a per-element constant density field ...
Modelling of pulse-triggered running waves on a blade cascade
Šnábl, Pavel; Pešek, Luděk
2023 - anglický
An experimental cascade of five NACA 0010 blades with pitch degrees of freedom is excited by a moment pulse to one of the blades. Depending on the flow conditions, such as wind speed and the angle of attack of the wind on the blades, the vibration of the excited blade is transmitted by the wind to the other blades. This can result in a running wave that diminishes over time or in a flutter running wave. A simplified spring-mass-damper model with inter-blade connections and non-linear van der Pol dampers is tuned to match experimentally obtained stability curves and tested to see if it can qualitatively model the response of the cascade to the pulse excitation.\n
Klíčová slova:
pulse-triggered running waves; blade cascade; NACA 0010
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Modelling of pulse-triggered running waves on a blade cascade
An experimental cascade of five NACA 0010 blades with pitch degrees of freedom is excited by a moment pulse to one of the blades. Depending on the flow conditions, such as wind speed and the angle of ...
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