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PL
W pracy podjęto tematykę wyznaczania parametrów modalnych i tłumienia laminatów przemysłowych stosowanych do celów konstrukcyjnych. Eksperymentalną analizę modalną przeprowadzono dla pięciu materiałów laminowanych typowych dla zastosowań przemysłowych. Uzyskane wyniki pozwalają na identyfikację częstości drgań własnych i postaci własnych drgań oraz współczynników tłumienia modalnego, na podstawie których podano zalecenia ich zastosowania w projektowaniu konstrukcji.
EN
The study deals with determination of modal parameters and damping of industrial laminates used for constructional purposes. The experimental modal analysis was performed for five laminated materials typical for industrial applications. Obtained results allow identifying natural frequencies and modal shapes of vibrations as well as modal damping factors, based on which the recommendations of their applications in structural design were given.
PL
Praca prezentuje analizę konstrukcji modelowego elektrowibratora z magnesami trwałymi. Analiza została przeprowadzona na przygotowanych przestrzennych modelach obliczeniowych z wykorzystaniem narzędzi do obliczeń MES i CFD firmy Autodesk. W wyniku przeprowadzonych badań symulacyjnych określono trwałość łożyskowania, wytrzymałość wału, konstrukcji wirnika i kadłuba, wyznaczono częstości drgań własnych wirnika i kadłuba oraz przeprowadzono analizę termiczną maszyny. Wykonana analiza pozwoliła na ocenę nowej konstrukcji elektrowibratora na etapie modelu, przed wykonaniem rzeczywistej maszyny.
EN
The structure analysis of the permanent magnet electro vibrator model is presented in the work. The analysis was carried out on prepared spatial computational models using Autodesk’s MES and CFD calculation tools. As a result of the simulation tests, bearing durability, shaft, rotor and body structure strength, the rotor and body vibrations frequencies, and thermal analysis of the machine was carried out. The analysis made possible to evaluate the new design of the electro vibrator at the model stage before the actual machine was made.
3
Content available remote Diagnostics of turbine blades, based on estimation of frequency response function
EN
The aim of the study is to propose a diagnostics method based on blade’s vibration model in frequency domain. Amplitude spectrum A(ω) and phase spectrum φ(ω) have been experimentally identified which define transfer function G(jω) = P(ω) + jQ(ω) and their real P(ω) and imaginary Q(ω) parts. Transfer function G(jω) and resulting frequency, amplitude, phase characteristics and real P(ω) and imaginary Q(ω) parts are parts of blade’s diagnostics model. Changes in those characteristics are directly related to changes in the technical condition of the blades. It has been noticed that small changes in the technical condition cause large changes in frequency characteristics, which proves their usefulness in the diagnosis process.
PL
Celem badania jest zaproponowanie metody diagnostycznej opartej na modelu drgań łopatek w dziedzinie częstotliwości. Zidentyfikowano eksperymentalnie widma ampli-tudowe A(ω) i fazowe φ(ω), które definiują transmitancję operatorową G(jω) = P(ω) + jQ(ω) oraz jej rzeczywiste P(ω) oraz urojone Q(ω) części. Transmitancja operatorowa G(jω) i wynikająca z niej częstotliwość, amplituda, charakterystyka fazowa oraz rzeczywiste P(ω) i urojone Q(ω) części są częściami modelu diagnostycznego łopatki. Zmiany w tych charakterystykach są bezpośrednio związane ze zmianami w stanie technicznym łopatek. Zauważono, że małe zmiany w stanie technicznym powodują duże zmiany w charakterystykach częstotliwościowych, co świadczy o ich przydatności w procesie diagnostycznym.
EN
Purpose: Curved box-girder bridges offers an excellent solution to the problems associated with traffic congestion. However, owing to their complex geometry, they are subjected to shear lag, torsional warping and cross-sectional distortion, which must be assessed in their study and design. Furthermore, the dynamic behaviour of curved bridges adds to the complexity of the issue, emphasizing the importance of studying free vibration. The purpose of this study is to numerically model the concrete curved box-girder bridge considering torsional warping, distortion and distortional warping effects and to identify key parameters that influence the free vibration response of the box-girder bridge by validating it with experimental and analytical studies. Design/methodology/approach: The concrete bridge is numerically modelled by means of computationally effective thin-walled box-beam finite elements that consider torsional warping, distortion and distortional warping, which are prominent features of thinwalled box-girders. The free vibration analysis of the concrete curved box-girder bridge is performed by developing a finite element based MATLAB program. Findings: The identification of critical parameters that influence the free vibration behaviour of curved thin-walled concrete box-girder bridges is one of the main findings of the study. Each parameter and its effect has been extensively discussed. Research limitations/implications: The study limits for the preliminary design phase of thin-walled box-girder bridge decks, where a complete three-dimensional finite element analysis is unnecessary. The current approach can be extended to future research using a different method, such as finite element grilling technique on multi-span curved bridges having unequal span. Originality/value: The current research implements a finite element formulation in combination with thin-walled beam theory, where an extensive parametric study is conducted on the free vibration behaviour of a concrete thin-walled box-girder bridge, while also accounting for their complex structural actions. The validity of the given numerical formulation is demonstrated by a comparison of the natural frequencies found experimentally. The study carried out will be of great importance for engineers to help them anticipate the modal characteristics of a curved concrete thin-walled girder bridge, which will further be useful for evaluating their dynamic response analysis.
EN
The article presents the results of the experimental verification of the deep hole boring bar tool model. The aim of the work was to obtain a verified boring bar tool model, which in further scientific research will be a starting point for creating a prototype of a tool with a new design, in which dynamic properties will be improved. The research was divided into two stages. In the first stage, modal studies of the model and the real object were carried out. The obtained discrepancy between numerical and experimental results below 8% allows to state that the model is characterized by dynamic properties occurring in the real boring bar. In the second stage of the research, static tests were carried out. The object was loaded with forces of 98.6 N, 195.0 N, 293.8 N. The obtained slight discrepancy in the results of numerical and experimental tests below 3% allows to state that the model reflects the static properties of the real boring bar. The high convergence of the theoretical and experimental results allows for the conclusion that the numerical model has been verified positively.
EN
The microstructure of some components which operate in high-temperature conditions (e.g. boiler components, turbine blades used in gas power plants, jet engines and reactors) is subjected to changes in long run, which leads to a degradation in the mechanical properties of these components and consequently, reduces their lifecycle. Therefore, it is so useful to detect the changes in the microstructure of these parts during their operation, employing an easy, fast and non-destructive method to determine their remaining life. In this study, we evaluate the effects of the microstructural changes on natural frequencies and the damping coefficient of CK35 steel, employing the experimental modal test. We aim to use the method for power plant components, if it has significant effects. To do so, we applied spheroidization heat treatment on CK35 steel samples having a primary structure of ferrite-pearlite for 24 and 48 hours. Then, we carried out the experimental modal test on samples having different metallurgical structures, but with the same dimensions and weights. According to the findings, the spherical ferrite-carbide particles in the ferrite structure increase the natural frequencies and damping coefficient. These tests show that the structural changes in this type of steel result in slight changes in the values of natural frequencies; however, it significantly changes the damping frequencies.
7
Content available remote Badanie modalne zamodelowanego elementu metalowego o strukturze kratownicowej
PL
Współczesne konstrukcje kratownicowe są projektowane, aby sprostały wymogom wytrzymałościowym niezagrażającym bezpieczeństwu ich użytkowania. Może to spowodować fakt, że wpływ drgań na konstrukcję kratownicową narażoną na działanie sił poziomych, jak też sił poprzecznych spowodowanych działaniem wiatru może być niebezpieczny dla bezpiecznego użytkowania (np.: konstrukcje mostowe). Uznając potrzebę doskonalenia oceny ich stanu, jak również współczynników bezpieczeństwa, wykonano badania destrukcji zamodelowanego elementu przęsła mostowego za pomocą metody teoretycznej analizy modalnej.
EN
Contemporary truss structures must maintain appropriate strength requirements for safe use. This may result in the fact that the influence of vibrations on a truss structure exposed to horizontal forces as well as transverse forces caused by wind may be dangerous for safe use (e.g. bridge structures). Recognizing the need to improve methods of testing truss elements for the purpose of assessing their condition as well as assessing the safety factors in this work, an attempt was made to examine the destruction of the modelled bridge span element using the theoretical modal analysis method.
8
Content available Digital Twin For Fatigue Analysis
EN
The main design parameters that impact the fatigue of components are geometry, material and loading. Simulation with Finite Element Analysis (FEA) and tests on a vibrating table are often used to understand the dynamic behaviour of components and thus validate those items. Accelerated tests are used for the mission profile and test definition, as described in GAM-EG-13, MIL-STD-810F and RTCA DO-160E. The shock response spectrum (SRS) and the extreme response spectrum (ERS) allow for a comparison of the power spectrum density (PSD) and the acceleration factor applied in terms of fatigue severity through the fatigue damage spectrum (FDS). In addition, the hypothesis of linear damage accumulation enables the combination of several events for specifying a mission profile. Ultimately, the mission profile, which represents a usage that might span over several years, can be reduced to a shorter duration with a damage extraction technique. This is particularly useful for the definition of vibrating table specifications. An advantage of the virtual vibrating table is the reduction of the number of prototypes and the understanding of failure modes. To achieve this objective, finite element analysis in the frequency domain (harmonic analysis) is used and the structural stress response is evaluated with a PSD loading. A statistical model of rainflow allows assessing the damage on the components. The presentation also shows the effects of the damping factor on damage results. To achieve accurate results and define a Digital Twin, the correlation between test results and the finite element analysis is fundamental. Experimental modal analysis, based on the measured acceleration responses, helps to validate calculated modal frequencies and to assess the damping for each mode. This study shows the importance and the sensitivity on damping of the structural response, and in turn on fatigue.
EN
The subject of the paper is an experimental study on girder-borne sound pressure emission. The sources of excitation are hammer and modal shaker. The structure researched is simply supported steel plate girder of the size: 7.95 m x 1.5 m. The study covers acceleration and sound pressure level measurements (SPL), and SPL estimation based on the accelerations measured. The correlation factor for higher estimation accuracy in lower frequency bands is proposed.
PL
Przedmiotem artykułu jest eksperymentalne badanie emisji ciśnienia akustycznego generowanego przez dźwigar blachownicowy. W badaniach jako źródło wymuszenia zastosowano młotek i wzbudnik modalny. Badana konstrukcja jest swobodnie podpartym stalowym dźwigarem blachownicowym o wymiarach: 7,95 m x 1,5 m. Badania obejmują pomiary przyspieszeń i poziomu ciśnienia akustycznego. Następnie oszacowano poziom ciśnienia akustycznego na podstawie zmierzonych przyspieszeń. Dokładność oszacowania zwiększono przyjmując współczynnik korelacji w pasmach niskich częstotliwości.
EN
In the paper, the results of investigations on the location of generating units most affecting the angular stability of a large power system (PS) are presented. For their location, the eigenvalues of the PS model state matrix associated with electromechanical phenomena (electromechanical eigenvalues) were used. The eigenvalues were calculated on the basis of the analysis of the disturbance waveforms of instantaneous power of the generating units operating in the PS. The used method of calculating eigenvalues consists in approximation of the disturbance waveforms of generating units by the waveforms being the superposition of modal components. The parameters of these components depend on the sought eigenvalues and their participation factors. The objective function was defined as the mean square error between the approximated and approximating waveforms. To minimize it, a hybrid algorithm, being a combination of genetic and gradient algorithms, was used. In the instantaneous power waveforms of generating units most affecting the PS angular stability, the least damped or undamped modal components dominate. They are related to eigenvalues with the largest values of real parts. The impact of individual modal components on the disturbance waveforms of subsequent generating units was determined with the use of participation factors and correlation coefficients of electromechanical eigenvalues.
EN
Acoustic barriers which are positioned along traffic lanes are designed to protect the surroundings from excessive noise. Such structures are to reverberate, diffract and damp the propagating acoustic waves. However, this method of shielding has some disadvantages which include constraint visibility and structure-born noise. The interaction between traffic-caused movement of air mass and acoustic barriers may generate infra noise waves. That is undesirable and should be estimated. The authors undertook the research to diagnose the plausible side effect of structure-born noise of such barriers because it may influence human body (Kasprzak, 2014). As a mechanical structure, the acoustic barrier is characterized by mechanical parameters which, in the field of modal analysis, are made up of natural frequencies, damping factors and mode shapes. In this paper the authors investigated the acoustic pressure distribution in the neighborhood of a real acoustic barrier in the scope of infra noise propagation. The methods of modal analysis were used to identify natural frequencies of the barrier and dominating frequencies of propagating waves in the far field. The correlation between observed vibration and acoustic signals is presented.
EN
The presented work considers the issue of the usefulness of alternative methods aimed at quickly and effectively identifying the local damage to the thin-walled composite load-bearing structures. Two ways of identifying destruction were considered, based on the assumption that the damage that occurs during operation causes local changes in the system rigidity. The first method is based on strain gauges. It consists of embedding strain gauges in the structure at the stage of composite production and monitoring of deformation during its life cycle. The second of the concepts under consideration is based on modal analysis, carried out using a modal hammer. On the example of the plate band, experimental studies supported by numerical analysis were carried out. The obtained research results and numerical analyses allowed for the formulation of a number of conclusions, mainly in terms of focusing on further research.
EN
Plate-like structures with attached piezo-patch elements are widely used in marine, aerospace and civil infrastructure applications to power small devices with low power demand or used for monitoring of vibration structures. In order to assess the feasibility of an energy harvesting system to generate power output from a harvester, an accurate electromechanical model of the piezo-patch harvester attached to a 2D structure in modal coordinates is required. Taking into account this fact, this study is focused on the analysis of the piezoharvester orientations on the SFSF (Simply Supported-Free-Simply Supported-Free) plate undergoing forced dynamic excitation. The results obtained from the numerical analysis of a smart structure led to determining quasi-optimal piezo-harvester location on the structure, and next, to determining a multi-mode representation of the equivalent circuit model. The experimental set-up carried out on the lab stand properly verified the parameters of the ECM model. Finally, the proposed approach can be used for the structural health monitoring of vibration of some 2D mechanical structures like the front wall of a dishwasher.
EN
The literature describes acoustic levitation phenomena with the utilization of air squeeze film between the vibrating inducer and the lifted object. The objective of the study is to determine the shape of the inducer with vibration characteristics that would allow the levitation of an object of the assumed geometry. In this paper, the influence of the dimension ratio of the inducer on the frequency of the first mode of vibration was presented. CFD calculations for a selected dimension series were performed with the goal of the determination of lifting conditions. The data obtained from the analysis will be used to manufacture an inducer that will serve as an experimental verification for the fluid dynamics calculation.
PL
W literaturze opisywane jest zjawisko lewitacji akustycznej z wykorzystaniem efektu wyciskania powietrza ze szczeliny między drgającym wzbudnikiem a unoszonym obiektem. Celem badań jest znalezienie takiego kształtu wzbudnika, którego charakterystyka drgań pozwalałaby na lewitację obiektu o założonej geometrii. W opracowaniu określono wpływ wymiarów wzbudnika na kształt oraz częstotliwość jego pierwszej postaci drgań własnych. Dla wybranego przypadku wykonano symulacje CFD w celu określenia warunków unoszenia. Uzyskane wyniki analiz posłużą do wykonania wzbudnika w celu przeprowadzenia weryfikacyjnych badań eksperymentalnych.
15
Content available remote The reasons for hybrid light pole failures – an analytical study
EN
This paper presents the results of a durability analysis of a hybrid light pole. The developed model includes a supporting structure of a pole with photovoltaic panels, a wind turbine and a boom with a light case. Due to various operating conditions, these poles may be characterised by a different configuration of the mutual spatial distribution of individual components. This results in a large diversity in the analysis results, hence the fact that the research was performed for the selected configuration variant for which the most unfavourable operating conditions were forecasted. In order to reveal potential stress concentration areas, a series of structural analyses was applied using the finite element method. As part of the work, changes to the supporting structure of the pole were proposed and to confirm the possibility of improving the resistance of the structure, additional analyses were conducted.
PL
W pracy przedstawiono wyniki modelowych badań wytrzymałościowych hybrydowego słupa oświetleniowego. W opracowanym modelu uwzględniono konstrukcję nośną słupa wraz z panelami fotowoltaicznymi, turbiną wiatrową oraz oprawą oświetleniową. Ze względu na zróżnicowane warunki eksploatacyjne słupy te mogą charakteryzować się odmienną konfiguracją wzajemnego przestrzennego rozmieszczenia poszczególnych komponentów. Powoduje to duże zróżnicowanie wyników analiz, stąd badania przeprowadzono dla wytypowanego wariantu konfiguracji, dla którego prognozowano najbardziej niekorzystne warunki eksploatacji. W celu ujawnienia potencjalnych miejsc koncentracji naprężeń zastosowano szereg analiz konstrukcji metodą elementów skończonych. W ramach pracy zaproponowano zmiany w konstrukcji nośnej słupa oraz przeprowadzono analizę potwierdzającą możliwość poprawy odporności konstrukcji.
PL
W artykule omówiono drgania własne osłony wału turbiny napędowej silnika lotniczego PZL-10W. Zasadniczym celem pracy było zidentyfikowanie modelu modalnego osłony, składającego się z częstotliwości własnych, współczynników tłumienia i postaci drgań. Wykonano eksperyment modalny osłony nieuszkodzonej oraz pękniętej w eksploatacji w celu zbadania zmiany właściwości dynamicznych na skutek uszkodzenia. Ustalono zbieżność otrzymanych wyników na podstawie przyjętych miar niedopasowania. Wyznaczono błąd względny częstotliwości własnych oraz podobieństwo postaci drgań na podstawie wskaźnika MAC.
EN
In the paper the natural vibrations of the PZL-10W aircraft engine turbine shaft shield are discussed. The goal was to identify a shield modal model consisting of natural frequencies, damping factors and forms of vibration. A modal experiment of undamaged and cracked shield in operation was performed to examine the change in dynamic properties due to damage. The convergence of the results obtained was determined on the basis of adopted mismatch measures. The relative error of natural frequencies and the similarity of the vibrations were determined on the basis of the MAC indicator.
EN
For the ERc 1400-30/7 type bucket wheel excavator (BWE) used in various Romanian open pit mines, a virtual model of the boom was constructed in SolidWorks. On this model, the variable in time forces acting during the excavation process were simulated, and the time history analysis (time response) was performed. This dynamic time response analysis was performed for excavation of homogenous material only, considering the damping as being of Rayleigh’s type, where the damping matrix is a linear combination of the mass and stiffness matrices. Based on the conducted analysis, the displacements of the boom during excavation were observed.
EN
The paper deals with the modal analysis and frequency response analysis of a bucket wheel excavator (BWE) boom, obtained by simulation, based on a virtual model of an existing BWE boom. The boom, which generally is realized as a spatial truss, is the most vulnerable subsystem of the BWE, being submitted to severe operational loads characterized by very pronounced cyclical, dynamic and stochastic variability. This vulnerability is the consequence of its shape and constructive parameters and the nature, source and character of the external exciting loads to which it is exposed. The classical approach recommended by standards and norms cannot predict the occurrence of failures caused by vibration, which produces fatigue due to the load’s cyclical variability and the deformation produced by resonant vibration of some constitutive elements. As exciting load we considered the operational forces acting on the bucket wheel. In this manner we can take into account the constructive features - with modal analysis, and the vibration regime - with frequency response analysis. The proposed method is useful both in the design phase of new load-bearing structures of truss type subjected to high-variability forces, and also in refurbishment or improvement phases of the existing structures of this kind.
19
Content available remote Eksperymentalna analiza modalna hybrydowej belki z polimerobetonu zbrojonego
PL
W artykule przedstawiono wyniki eksperymentalnej analizy modalnej innowacyjnej belki wykonanej z materiału kompozytowego zbrojonego prętami stalowymi. Badania miały na celu porównanie właściwości dynamicznych tego rodzaju hybrydowego połączenia do profilu stalowego wypełnionego kompozytem i belki w całości wykonanej z kompozytu.
EN
The paper presents results of experimental modal analysis of hybrid composite beam reinforced with steel rods. The purpose of the research was comparison dynamic properties of this type of connection composite material and steel to steel profile filled with polymer concrete and beam made entirely of composite.
EN
The article presents results of both experimental and FEM model-based investigations on chatter phenomena that occur in the end milling process. On the basis of chatter symptoms observed during machining, the mechanism of its occurrence has been identified. Then, a FEM model has been built to indicate machine tool elements responsible for loss of stability. Afterwards, experimental modal analysis has been conducted in order to validate the FEM model. Finally, on the basis of the validated model, the structural changes have been proposed and applied in the real object resulting in increased stability.
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