No (11867)
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Applications of blade vibration measurements in the laboratory of rotational laser vibrometry
Maturkanič, Dušan; Procházka, Pavel; Hodboď, Robert; Mekhalfia, Mohammed Lamine; Voronova, Evgeniya
2023 - English
The Laboratory of Rotational Laser Vibrometry was established at the Institute of Thermomechanics AS CR, v.v.i. in 2015 and the first experiments were started the following year. The measurements are intended for the research of vibration of rotating blades. The paper includes a summary of measurement results using a special turbine model and their consequences in theoretical research, as well as measurements with a real compressor of aircraft engine and comparison with computational analysis. The paper also describes the complex system for measurement and analysis.
Keywords:
laboratory; turbine; blade; vibration; precision method
Available at various institutes of the ASCR
Applications of blade vibration measurements in the laboratory of rotational laser vibrometry
The Laboratory of Rotational Laser Vibrometry was established at the Institute of Thermomechanics AS CR, v.v.i. in 2015 and the first experiments were started the following year. The measurements are ...
The effect of the backfill on the integrity of a buried pipeline upon heavy-duty vehicle crossings
Gajdoš, Lubomír; Šperl, Martin; Slížková, Zuzana; Drdlová, M.
2023 - English
The aim of this work was to determine stresses in the wall of a buried empty gas pipeline caused by the weight of backfill as well as by heavy-duty vehicles crossing the pipeline, and, on their basis to assess the applicability of protective sleeves. A buried pipeline with zero internal pressure of transported medium (empty pipeline) differs from an unburied pipeline by the vertical load due to the weight of the backfill which causes an ovalness of the circular cross section of the pipeline. This leads to the rise of through-wall bending stresses with the tensile stress at the outside surface at the 3 and 9 o´clock positions and compressive stress at the inside surface. At the 6 and 12 o´clock positions the stresses are tensile at the inside surface and compressive at the outside surface. The current depth of soil cover above gas pipelines is 0.5 m. For pipes DN500, t ~ 6.5 mm the through-wall bending stress is found to be σb ≈ ±10 MPa. In comparison with the yield stress of pipeline material, this stress is negligible. The situation is changed when heavy-duty vehicles cross the pipeline. For example, when a MAN truck with the mass load 3270 kg acting on a single wheel of the front axle crosses this pipeline, the pressure transmitted to the pipe will cause the through-wall bending stress σb ≈ ±76 MPa. This stress is superimposed to that of the backfill to give the total value ±86 MPa. When dead loads, imposed by backfill cover, together with live loads, caused by truck-wheel loads, are excessive a crushing of side walls of the pipeline and/or ring buckling of the pipe cross section can happen.
Keywords:
gas pipeline; pressure; buried pipeline
Available at various institutes of the ASCR
The effect of the backfill on the integrity of a buried pipeline upon heavy-duty vehicle crossings
The aim of this work was to determine stresses in the wall of a buried empty gas pipeline caused by the weight of backfill as well as by heavy-duty vehicles crossing the pipeline, and, on their basis ...
Experimental evaluation of aluminothermic welds
Zeman, L.; Valach, J.; Zlámal, P.; Krčmářová, N.; Koudelková, Veronika; Zeman, J.
2023 - English
The article presents a study of the mechanical processes occurring during the aluminother-mic reaction using experimental methods (strain gauges, digital image correlation, thermography,scanning electron microscopy, profilometry). The aluminothermic reaction is a highly efficient weldingmethod due to its exothermic behaviour, however, it places considerable demands not only on thewelding technique, but also on the capabilities of the experimental methods used - these limitationsare also discussed in the article. The aluminothermic reaction is associated with the formation of alocalised heat source with a time evolution dictated by the technological procedure, which manifestsitself in heat propagation to the surrounding weld material. The unequal evolution of the temperaturefield is the fundamental cause of the appearance of the heat affected zone or local deformations orsurface curvature, which was the focus of the experimental methods deployed above and the results ofwhich are shown in the article.
Keywords:
aluminothermic reaction; train gauges; hardness; profilometry; scanning electron microscope
Available at various institutes of the ASCR
Experimental evaluation of aluminothermic welds
The article presents a study of the mechanical processes occurring during the aluminother-mic reaction using experimental methods (strain gauges, digital image correlation, thermography,scanning ...
Fast continuous in-situ XCT of additively manufactured carbon fiber reinforced tensile test specimens
Glinz, J.; Maurer, J.; Holzleitner, M.; Pace, F.; Stamopoulos, A.; Vopálenský, Michal; Kumpová, Ivana; Eckl, M.; Kastner, J.; Senck, S.
2023 - English
The reinforcement of fused filament fabricated (FFF) components with continuous fibers allows for high versatility in the design of mechanical properties for a specific application’s needs. However, the bonding quality between continuous fibers and the FFF matrix material has high impact on the overall performance of the composite. In a recent study [1], additively manufactured (AM) continuous fiber reinforced tensile test specimens have been investigated regarding the effect of amount and material of the embedded continuous fibers on tensile strength and AM build quality. During these tensile tests, a sudden reduction in tensile stress, which most likely was not related to actual rupture of continuous fibers, was noticeable. Since X-ray computed tomography (XCT) scans were performed only prior to and after the tensile testing, a detailed investigation on the origin of these drops in tensile stress was not possible. Within this work, we will expand upon these findings and present results of fast on-the-fly in-situ investigations performed on continuous carbon fiber reinforced specimens of the same AM build. During these investigations, specimens are loaded under the same conditions while fast XCT scans, with a total scan time of 12 seconds each, were performed consecutively. The resulting three-dimensional image data reveals internal meso- and macro-structural changes over time/strain to find the cause of the aforementioned reduction in tensile stress.
Keywords:
additive manufacturing; composites; X-ray computed tomography; in-situ tensile testing
Available at various institutes of the ASCR
Fast continuous in-situ XCT of additively manufactured carbon fiber reinforced tensile test specimens
The reinforcement of fused filament fabricated (FFF) components with continuous fibers allows for high versatility in the design of mechanical properties for a specific application’s needs. However, ...
Acta Polytechnica CTU Proceedings. Vol. 42 (2023)
Kytýř, Daniel; Doktor, T.; Zlámal, Petr
2023 - English
The YSESM symposium provides a forum for young researchers and engineers, PhD students and students dealing with subjects of experimental mechanics. The Symposium concentrates on current work in all areas of experimental research and its application in solid and fluid mechanics. The topic will particularly concern to: Conventional and Advanced Experimental Methods in Solid and Fluid Mechanics, Non-Destructive Testing and Inspection, Measurements in Material Science, Computer Assisted Testing and Simulation, Engineering Design Simulation, Hybrid Methods, Experimental Techniques – Numerical Simulation, Optical Methods and Image Processing, Measurements in Biomechanics, Sensor Techniques for Micro- and Nano-Applications, Measurement Methods for Forensic Engineering.
Keywords:
experimental mechanics; fluid mechanics; mechanics of solids
Available at various institutes of the ASCR
Acta Polytechnica CTU Proceedings. Vol. 42 (2023)
The YSESM symposium provides a forum for young researchers and engineers, PhD students and students dealing with subjects of experimental mechanics. The Symposium concentrates on current work in all ...
Analyzing stochastic stability of a gyroscope through the stochastic Lyapunov function
Náprstek, Jiří; Fischer, Cyril
2023 - English
The text delves into the application of first integrals in the construction of Lyapunov functions for analyzing the stability of dynamic systems in stochastic domains. It emphasizes the distinct characteristics of first integrals that warrant the introduction of additional constraints to ensure the essential properties required for a Lyapunov function. These constraints possess physical interpretations associated with system stability. The general approach to testing stochastic stability is illustrated using the example of a 3-degrees-of-freedom system representing a gyroscope.
Keywords:
stochastic stability; Lyapunov function; first integral; gyroscope
Available at various institutes of the ASCR
Analyzing stochastic stability of a gyroscope through the stochastic Lyapunov function
The text delves into the application of first integrals in the construction of Lyapunov functions for analyzing the stability of dynamic systems in stochastic domains. It emphasizes the distinct ...
Novel embedding resins for 3D-SEM
Šlouf, Miroslav; Pavlova, Ewa; Strachota, Beata; Strachota, Adam; Nebesářová, Jana; Týč, Jiří; Krzyžánek, Vladislav; Skoupý, Radim
2022 - English
The report contains the detailed analysis of novel embedding resins for 3D-SEM.
Keywords:
novel embedding resins; 3D-SEM microscopy; higher e-beam resistance
Available at various institutes of the ASCR
Novel embedding resins for 3D-SEM
The report contains the detailed analysis of novel embedding resins for 3D-SEM.
Autonomous vehicles lane detection using particle filters
Věchet, Stanislav; Krejsa, Jiří; Chen, K.S.
2022 - English
Lane detection belongs among many others crucial tasks which an autonomous vehicles traveling in urban roads need to take care of. We present a lane detection method which uses particle filters combined with visual information from onboard camera to control the vehicles direction. Our initial experiments shows promising results as applied and tested in urban roads with focus on real-time data processing.
Keywords:
mobile robot; signal processing; measurement
Available at various institutes of the ASCR
Autonomous vehicles lane detection using particle filters
Lane detection belongs among many others crucial tasks which an autonomous vehicles traveling in urban roads need to take care of. We present a lane detection method which uses particle filters ...
5th International Percid Fish Symposium, Percis V 2022
Holubová, Michaela
2022 - English
The publication contains scientific abstracts from the international conference.
Keywords:
abstracts; conference; fish
Available at various institutes of the ASCR
5th International Percid Fish Symposium, Percis V 2022
The publication contains scientific abstracts from the international conference.
Mobile Robot in the Elevator: What Floor Am i On?
Krejsa, Jiří; Věchet, Stanislav; Chen, K.S.; Havelka, M.; Černil, M.
2022 - English
Wheeled mobile robots in multiple stories buildings have to use elevator to access arbitrary floor of the building. To do so, the control system must be able to detect and access elevator controls and also determine on which floor the elevator stopped. The paper deals with the latter problem, using the fusion of relative floor change detected by onboard accelerometer and absolute floor number detected by the processing of elevator information screen panel image acquired by onboard camera. Bayesian filter is used for data fusion and convolution neural network for image processing. Field tests resulted in 97% correct detection.
Keywords:
mobile robot; elevator floor determination; Bayesian filtering
Available at various institutes of the ASCR
Mobile Robot in the Elevator: What Floor Am i On?
Wheeled mobile robots in multiple stories buildings have to use elevator to access arbitrary floor of the building. To do so, the control system must be able to detect and access elevator controls and ...
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