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1

Model analysis of worm gear pair system using finite element analysis

Barshikar Raghavendra Rajendra, Baviskar Prasad R., Patil Milind M., Dube Anil S., Dhore Vishal J.

International Journal of Applied Mechanics and Engineering

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2024

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Vol. 29, no. 2

1--15

EN

Spur gear, helical gear, worm gear, and bevel gear are all important components in industrial applications such as vehicles, pushes, conveyors, elevators, bowl mill, rolling mills, ribbon blender, machine tools, aeroplanes, and windmills. When various types of defects, such as wear, tooth breakage, corrosion, and scratches on bearings, appear in gearboxes, normal machine function may be abruptly terminated. As a result, output and dependability suffer. As a result, several quality tracking and evaluation approaches have been adopted by companies. Finite element analysis (FEA) is one of the approaches. This research paper presents the FEA of a ribbon blender worm gear pair by using Ansys 18.0 to identify the weak gear of the worm gear pair, natural frequency, and deformation. Proe-5 utilized for creation of three-dimensional geometry of threaded worm and toothed worm wheels, as well as other related elements such as shafts and bearings. Steel is used for the worm, shaft, and bearing, whereas bronze is used for the worm wheel. Ansys 18.0 is implemented to carry out worm gear pair model analysis. The results demonstrate that the worm wheel had the most deformation when compared to the worm, and that the natural frequency is greater than the operational frequency of the worm gear pair. The findings of the research study, worm wheel deteriorate early than worm, model analysis plays a significant role in vibration monitoring of worm gear pair, and this work is valuable for further fault analysis of ribbon blender worm gearbox utilising vibration response.

2

Analyzing frequency response analysis experimentally for bone healing detection: examining the potential of vibrational evaluations

Kadhim Abbas Jawad, Aubad Mohammed Jawad, Al-Juboori Ameen M.

Diagnostyka

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2024

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Vol. 25, No. 3

art. no. 2024315

EN

Assessment of bone healing is essential for efficient orthopedic treatment. This work investigates the feasibility of assessing frequency response experimentally for bone healing detection, with a particular emphasis on the use of vibrational assessments. Detailed experimental studies were carried out to determine the ability of frequency response analysis to assess bone healing. Mechanical excitation was delivered to cracked bone samples at various frequencies, and the vibrational responses of the displacement and accelerations were measured. The experimental setting includes testing five samples, to cover a wide range of possibilities. The obtained vibrational, such phase, magnitude, and coherence, were examined to find common patterns and changes linked with the healing process. The results showed that frequency response analysis has the potential to identify bone healing, as unique vibrational responses were seen in healed samples under cyclic load for different turns (0, 1000, 2000, 3000, and 4000). The findings demonstrate the sensitivity of vibrational evaluations in capturing the mechanical properties and healing condition of bone tissue. Furthermore, the presence of cracks impacts both structural integrity and natural frequency. Natural frequency decreases as the number of cycles increases. The highest frequency reduction occurred at the first mode shape and maximum cycle number, indicating considerable fracture behaviour changes. Natural frequency can be used to assess bone health; higher stiffness and frequency are associated with smaller crack size.

3

A parametric study of higher-mode natural frequencies of composite stiffened cylindrical shell with cut-out

Chaudhuri Puja Basu, Sahoo Sarmila, Mitra Anirban

Engineering Transactions

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2023

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Vol. 71, iss. 1

81--109

EN

A finite element-based dynamic study of cut-out borne composite cylindrical shells reinforced with stiffeners is conducted. Isoparametric shell element with eight nodes and beam element with three nodes are used to study the mode-frequency behavior of shells with varied edge conditions. Anti-symmetric angle-ply laminates of two, four and ten layers with varying lamination angles are considered. Ten-layer laminates are investigated further as they exhibit better performance in fundamental frequency than two and four-layer laminates. The reduced integration method is adopted to find the shell element’s stiffness and mass matrices and the subspace iteration method is used for the eigenvalue solution of free vibration formulation. Natural frequencies for the first five modes are considered. The effects of fiber orientation angle (θ), degree of orthotropy (E11/E22), and width/thickness ratio (b/h) on the natural frequency are determined through numerical studies. It is revealed that vibration behavior strongly depends on both the number and arrangement of boundary constraints.

4

Effects of non-classical boundary conditions on the free vibration response of a cantilever Euler-Bernoulli beams

Afras Abderrachid, El Ghoulbzouri Abdelouafi

Diagnostyka

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2023

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Vol. 24, No. 1

art. no. 2023107

EN

In this article, the problem of the free vibration behavior of a cantilever Euler-Bernoulli beam with various non-classical boundary conditions, such as rotational, translational spring, and attached mass is investigated. For describing the differential equation of the system. An analytical procedure is proposed firstly, and a numerical method based on the differential transform method DTM is developed in order to validate the obtained results. A parametric study for various degenerate cases is presented with the aim to analyze the influence of rotational stiffness, vertical stiffness, and mass ratio on the free vibration response of the beam, particularly on its modal characteristics. The results show that the non-classical boundary conditions significantly affect the natural frequency and mode shapes of the studied beam system in comparison to the case of a classical boundary conditions such as Simply supported, clamped-clamped, etc. The comparison between the obtained results based on the proposed analytical solution and numerical scheme, and those available in the literature shows an excellent agreement.

5

Effect of icing as a non-structural mass on the variation of natural frequency of a lightweight lattice structure

Kowalski Wiesław, Richter Mateusz, Tokarczyk Katarzyna

Archives of Civil Engineering

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2023

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Vol. 69, nr 4

37--53

EN

This paper analyzes the effect of additional masses for lattice structures on the nature of changes in the natural frequencies of the structure. An attempt to mathematically describe this nature and the scale of the effect with a known thickness of the icing layer was also made. The discussion concerns a structure with a sacred purpose - the Gate of the Third Millennium, located in the Lednickie Fields, in the Kiszkowo Municipality, Gniezno Poviat. The icing of structural bars (frost, rime) is treated as a source of additional masses, although the origin of non-structural mass is of secondary importance for the analysis in question. The analysis was carried out by Finite Element Method (FEM) modeling of the structure, assuming a single-parameter variation of its mass (that is, the additional mass of all elements of the test object varies proportionally to a single parameter, which is the outer surface of the element on which the ice layer is deposited). By solving the vibration eigenproblem for successive models, representing different intensities of icing of the object, the values of successive frequencies and descriptions of the corresponding eigenmodes were determined. The results obtained allow us to formulate a postulate that the possibility of a change in the mass of the analyzed object resulting from icing or other causes should be taken into account in strength analyses, wherein the dynamic properties of the structure play an important role, such as in assessing the susceptibility of the structure to dynamic loads.

PL

W pracy dokonano analizy wpływu dodatkowych mas dla konstrukcji typu kratownicowego na charakter zmian częstotliwości drgań własnych tej konstrukcji. Przeprowadzono też próbę matematycznego opisu tego charakteru oraz skali wpływu przy znanej grubości warstwy oblodzenia. Rozważania dotyczą budowli o przeznaczeniu sakralnym - Bramy Trzeciego Tysiąclecia, zlokalizowanej na Polach Lednickich w gminie Kiszkowo w powiecie gnieźnieńskim. Jako źródło dodatkowych mas traktowane jest oblodzenie prętów konstrukcyjnych (szron, szadź), jakkolwiek pochodzenie masy niekonstrukcyjnej ma dla przedmiotowej analizy znaczenie drugorzędne. Analizy dokonano w drodze modelowania Metodą Elementów Skończonych (MES) konstrukcji, przyjmując założenie o jednoparametrycznej zmienności jej masy (to znaczy, że dodatkowa masa wszystkich elementów badanego obiektu zmienia się proporcjonalnie do jednego parametru, którym jest powierzchnia zewnętrzna elementu, na której odkłada się warstwa lodu). Rozwiązując zagadnienie własne drgań dla kolejnych modeli, reprezentujących różne intensywności oblodzenia obiektu, wyznaczono wartości kolejnych częstotliwości i opisy odpowiadających im postaci drgań własnych. I tak, przyrost grubości warstwy lodu na powierzchniach, od 0 do 1 cm spowodował redukcję wszystkich wyznaczonych (dziesięciu podstawowych) częstotliwości drgań własnych o co najmniej 11%. Grubość oblodzenia 2 cm wpływa na redukcję częstotliwości, jak wyżej, o ok. 22% zaś 4 cm warstwa oblodzenia oznacza redukcję przedmiotowych częstotliwości powyżej 39%. Są to istotne wartości, z punktu widzenia zastosowań technicznych. Uzyskane wyniki pozwalają na sformułowanie postulatu, aby w analizach wytrzymałościowych, w których istotną rolę odgrywają właściwości dynamiczne konstrukcji, np. w ocenie podatności konstrukcji na obciążenia dynamiczne, uwzględniana była możliwość zmiany masy analizowanego obiektu wynikająca z oblodzenia lub z innych przyczyn.

6

Assessment of the impact of the number of girders on the dynamic behaviour of Geiger dome

Obara Paulina, Solovei Maryna

Archives of Civil Engineering

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2023

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Vol. 69, nr 3

597--611

EN

In this paper, the dynamic behaviour of the tensegrity domes is explored. The consideration includes all cable structures called Geiger domes, i.e., two cases of configurations (with a closed and open upper section) and two variants of the nature of a dome (regular and modified) are taken into account. Particularly, the impact of the number of girders on the natural frequencies is analysed. A geometrically quasi-linear model is used, implemented in an original program written in the Mathematica environment. The results confirm that the number of girders affects the number of infinitesimal mechanisms. However, the dynamic behaviour does not depend on the number of mechanisms. The most important is the nature of a dome and the type of load-bearing girder. Especially, the behaviour of Geiger domes with a closed upper section is specific. In this case, not only the frequencies corresponding to the infinitesimal mechanisms depend on the prestress. There are additional frequencies that depend on prestress. The number of them, and the sensitivity on the initial prestress changes, depends on the number of girders. Generally, for the same number of girders, the natural frequencies of regular domes are higher than for the modified ones.

PL

W artykule zbadano zachowanie dynamiczne kopuł Geigera. W sposób szczególny przeanalizowano wpływ liczby dźwigarów nośnych na częstotliwość drgań własnych. Analizie poddano dwa typy dźwigarów nośnych tj. z zamkniętą (typ A) oraz otwartą (typ B) górną częścią dźwigara. Dodatkowo wzięto pod uwagę dwa typy geometrii kopuły (zwykłą i zmodyfikowaną). Przedstawione rozważania odpowiadają na następne pytania tj. czy jest możliwa kontrola liczby mechanizmów poprzez zmianę liczby dźwigarów nośnych? Jaki typ kopuły (zwykła czy zmodyfikowana) jest łatwiejszy do kontroli? Czy zachowanie kopuł z taką samą liczbą mechanizmów infinitezymalnych jest podobne? Czy liczba częstotliwości drgań własnych, zależnych od wstępnego sprężenia, jest równa liczbie nieskończenie małych mechanizmów? Analiza potwierdziła, że liczba dźwigarów nośnych ma wpływ na liczbę nieskończenie małych mechanizmów. Jednak zachowanie dynamiczne kopuł zależy głównie od geometrii kopuły oraz od typu dźwigara nośnego, a nie od liczby mechanizmów.

7

Evaluation of sand p–y curves by predicting both monopile lateral response and OWT natural frequency

Amel Douifi, Djillali Amar Bouzid, Subhamoy Bhattacharya, Nasreddine Amoura

Studia Geotechnica et Mechanica

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2022

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Vol. 44, nr 1

66--81

EN

Extending the use of the p–y curves included in the regulation codes API and DNV to design large-diameter monopiles supporting offshore wind turbines (OWTs) was unsuccessful as it resulted in an inaccurate estimation of the monopile behavior. This had prompted many investigators to propose formulations to enhance the performances of Winkler model. In this paper, two case studies are considered. A case consisting of an OWT at Horns Rev (Denmark) supported by a monopile in a sandy soil was studied first. Taking the FEA using ABAQUS as reference, results of WILDOWER 1.0 (a Winkler computer code) using the recently proposed p–y curves giving design parameters were plotted and evaluated. In order to see the ability of proposed p–y curves to predict the monopile head movements, and consequently the first natural frequency (1st NF), a second case study consisting of a monopile supporting an OWT at North Hoyle (UK) was selected. The monopile head stiffness in terms of lateral, rocking, and cross-coupling stiffness coefficients, necessary for the 1st NF, were computed using both ABAQUS and WILDPOWER 1.0. Comparisons with the measured 1st NF showed that with the exception of one p–y model, none of other proposed Winkler methods is able to predict accurately this parameter.

8

Study the internal cracks effect on vibration of laminated composite square plates

Hassan M.S., Rashid Z.H., Sarhan R.A.

Archives of Materials Science and Engineering

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2022

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Vol. 116, nr 1

28--33

EN

Purpose: The study of cracks behaviour in a composite plate is of significant importance in the dynamics of the Mechanical parts in order to avoid design failures due to resonance or high amplitude vibrations. Design/methodology/approach: In this paper, a square glass-epoxy composite plate is adopted. The plate has four layers with symmetric and asymmetric lamination. Assuming the cracks are profound as defects. The results were obtained by using a numerical solution of mechanical APDL from ANSYS. Findings: It has been found for different boundary conditions that the rank of natural frequencies is decreased by increasing the crack ratio due to the reduction of the plate’s stiffness, whereas the crack direction has no mentioned effect for a small angle of rotation. Research limitations/implications: The accuracy of results is verified by comparing a single case of the current work with other previous investigations. value: Evaluate the influence of the crack length ratio, angle of the crack rotation, boundary conditions and lamination angles on the natural frequencies of the square composite plate with glass-epoxy materials.

9

Design and analysis of cementless hip-joint system using functionally graded material

Asiri Saeed

Archive of Mechanical Engineering

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2022

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LXIX, nr 1

129--146

EN

Functionally Graded Materials (FGM) are extensively employed for hip plant component material due to their certain properties in a specific design to achieve the requirements of the hip-joint system. Nevertheless, if there are similar properties, it doesn’t necessarily indicate that the knee plant is efficiently and effectively working. Therefore, it is important to develop an ideal design of functionally graded material femoral components that can be used for a long period. A new ideal design of femoral prosthesis can be introduced using functionally graded fiber polymer (FGFP) which will reduce the stress shielding and the corresponding stresses present over the interface. Herein, modal analysis of the complete hip plant part is carried out, which is the main factor and to date, very few research studies have been found on it. Moreover, this enhances the life of hip replacement, and the modal, harmonic, and fatigue analysis determines the pre-loading failure phenomena due to the vibrational response of the hip. This study deals with the cementless hip plant applying the finite element analysis (FEA) model in which geometry is studied, and the femoral bone model is based in a 3D scan.

10

Natural frequency and critical velocities of heated inclined pinned PP-R pipe conveying fluid

Mohmmed J. H., Tawfik M. A., Atiyah Q. A.

Journal of Achievements in Materials and Manufacturing Engineering

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2021

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Vol. 107, nr 1

15--27

EN

Purpose: The flow velocity and pressure of fluid flowing through a pipeline can cause the vibration of pipes, and consequently result in the modification in natural frequency via fluid-structure interaction. The value of the natural frequency of a component when approaches the excitation force to a certain degree, a severe resonance failure may occur. Hence, avoiding the resonance failure of a pipe subjected to complex conditions is an essential issue that requires to be solved urgently in the engineering field. This work treats the transverse vibration for flexible inclined heated pipe, made of polypropylene randomcopolymer (PP-R), conveying fluid assuming pinned connections at the ends. The pipe was placed at different support angles and subjected to variant temperatures. Design/methodology/approach: The inclined pipe is modelled as Euler-Bernoulli beam taking into account its self-weight, temperature variation, inclination angle, aspect ratio, and internal fluid velocity. The integral transforms method, which includes the finite Fourier sine and the Laplace transforms, was used to develop an analytic solution to the modified equation of motion and the analytical expressions for dual natural frequencies of the pipefluid interaction system were computed. Findings: The proposed solution technique via finite Fourier sine and Laplace transforms offers a more convenient alternative to calculate the dynamic characteristic of pipes conveying fluid. The obtained results showed that the dynamical behaviour of pipe–fluid system is strongly affected by fluid flow velocity, degree of inclination, temperature variation, and aspect ratio of the pipe in transverse modes. Research limitations/implications: This work focuses on fundamental (first) mode in the most discussions. Practical implications: It was revealed that the thermal effects in the pipe are a very important factor and more significant in comparison with the internal fluid velocity and the inclination angle has a larger impact on vibration characteristics at a higher aspect ratio. The findings can be useful for the design of engineering components. Originality/value: Determining the combining effect of inclination angle, aspect ratio, and thermal loading on vibration characteristic of the pipes conveying fluid by using an improved analytic solution to the modified equation of motion via mixed of finite Fourier sine and Laplace transforms.

11

Natural frequencies of FG plates with two new distribution of porosity

Merdaci Slimane, Mostefa Adda Hadj, Khayal Osama M. E. S.

International Journal of Applied Mechanics and Engineering

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2021

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Vol. 26, no. 2

128--142

EN

The functionally graded plates (FGP) with two new porosity distributions are examined in this paper. In this work the plate is modeled using the higher-order shear deformation plate principle. The shear correction variables are neglected. To evaluate the equations of motion, the Hamilton method will be used herein. Therefore, the free vibration analysis of FG plate is developed in this work. For porous smart plates with simply-supported sides, natural frequencies are obtained and verified with the established findings in the literature. The impact of the porosity coefficient on the normal frequencies of the plate for various thickness ratios, geometric ratios, and material properties was investigated in a thorough numerical analysis.

12

A Study on Dynamic Behavior of Natural Draft Cooling Tower Considering the Effect of Soil-Structure Interaction

Chitrahalli Lingaraju Mahesh Kumar, Kotagi Girisha Shwetha, Bhaktanakatte Channabasappa Shanthappa, Karigowda Manjunatha

Civil and Environmental Engineering Reports

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2021

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Vol. 31, no. 4

17--32

EN

In this present era, the technology in advanced construction has developed to a very large extent. Some parts of the constructions are still in the improving stage which includes cooling tower construction. Hyperbolic cooling towers are large, thin shell reinforced concrete structures which contribute to power generation efficiency, reliability, and to environmental protection. Cooling towers use evaporation of water to eject heat from processes such as cooling the circulating water used in oil refineries and in power plants. Nowadays in many thermal power plants, we can see the cooling tower. So, preserving this industrial structure is an effort to save the cooling tower from dangerous earthquakes. The present-day cooling towers are exceptional structures in view of their sheer size and complexities. Present paper deals with the study of dynamic response that is modal analysis, seismic analysis of the two different cooling towers varying the H/t ratio and thicknesses with fixity at the base boundary condition, and the soil is modelled as raft for the effect of soil-structure interaction using the direct approach. In this paper, hyperbolic cooling towers are modelled using ANSYS software, which is a finite element software. Results show that the soil-structure interaction effect significantly modifies the earthquake behavior of hyperbolic cooling towers.

13

Stability and vibrations of micro-nonhomogeneous plate band resting on elastic subsoil

Chalecki Marek, Jemielita Grzegorz

Archives of Civil Engineering

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2021

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Vol. 67, nr 1

403--424

EN

The paper presents a procedure of calculation of natural frequencies and critical buckling forces of a micro-nonhomogeneous plate band resting on nonhomogeneous elastic subsoil and having any given boundary conditions. The band consists of N parts - cells - called elements, having a constant width l = L/N. Each band element consists of three parts - subelements with variable widths. The two of these subelements are matrix, the third - inclusion placed symmetrically relative to the matrix. Each band element is built of two isotropic materials. The matrix and inclusion bands have the stiffness and mass per area unit as well as they rest on the subsoil. The model has been derived with use of the classical displacement method. The stiffness matrix of any band element and then the band stiffness matrix have been built. An appropriate computer program has been written to calculate natural frequencies and critical buckling forces. A number of tests have been performed to check the working of the program and several calculative examples has been presented in the paper.

PL

W pracy przedstawiono sposób obliczania częstości drgań własnych i wyznaczania wartości sił krytycznych mikroniejednorodnego pasma płytowego o dowolnych warunkach brzegowych, spoczywającego na niejednorodnym podłożu sprężystym. Pasmo składa się z N części - komórek, zwanych elementami, o stałej szerokości l = L/N. Każdy element pasmowy składa się z trzech części - subelementów o zmiennych szerokościach. Dwie z nich są osnową, trzecia zaś wtrąceniem symetrycznie położonym względem osnowy. Każdy element pasmowy składa się z dwóch izotropowych materiałów. Pasma osnowy i wtrącenia mają pewne sztywności i masy na jednostkę powierzchni oraz spoczywają na podłożu o pewnej sztywności. Do wyznaczenia częstości drgań własnych i wartości krytycznych zastosowano metodę przemieszczeń. Zbudowano macierz sztywności dowolnego elementu pasmowego, a następnie macierz sztywności pasma. Ułożono odpowiedni program na wyznaczenie częstości drgań własnych i sił krytycznych ze względu na wyboczenie. Wykonano szereg testów sprawdzających działanie programu i podano szereg przykładów obliczeniowych.

14

Dynamic response of the Stuttgart TV Tower measured by classical instruments and GPS technology

Breuer Peter, Chmielewski Tadeusz, Górski Piotr

Archives of Civil Engineering

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2021

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Vol. 67, nr 1

7--38

EN

This paper compares the measurement results of dynamic characteristics, including natural frequencies, damping ratio, and wind-induced responses of the Stuttgart TV Tower (TV Tower), obtained by Lenk in 1959 using classical instruments with those obtained by the authors a few decades later using Global Positioning System (GPS). The objective of this paper was to monitor the response of the TV Tower under wind loading, which is an important tool for the validation of its design, construction, and structural health. During the authors’ GPS measurements, weak and moderate wind speeds occurred most of the time. Only in 2007, the stronger wind observed (90 < V < 100 km/h) at the head of the TV Tower (H=157 m), which caused displacements in the decimetre range. Further measurements in 2011 were carried out, using additional GPS receivers with a higher data rate. The results achieved by the GPS prove that the cross-wind response was larger than the along-wind component for all ranges of wind speed, which occurred during the measurement periods, i.e. from 2002 to 2015. The authors of this paper extended Lenk’s results, by the static and along-wind components, confirmed the first natural frequency, and damping ratio, evaluated by the Random Decrement technique. Mounting a GPS receiver, on the steel antenna mast tip, enabled detection of the second natural frequency fs2 = 0.800 Hz, which is the frequency of the mode shape of the TV Tower steel antenna mast. Lenk did not measure this frequency.

PL

Wieża telewizyjna w Stuttgarcie została oddana do użytkowania w dniu 5 lutego 1956 roku. Konstrukcja wieży składa się z dwóch części: (a) trzonu żelbetowego z głowicą o wysokości 161 m i (b) stalowego masztu antenowego o wysokości 56 m. Całkowita wysokość wieży to 217 m. Średnica zewnętrzna trzonu żelbetonowego wynosi 10,8 m u podstawy trzonu i 5,04 m w górnej części trzonu (poniżej głowicy trzonu). Grubość ściany trzonu zmienia się od 60 cm do 19 cm. W latach 1953-1954 Leonhard zaproponował koncepcję i projekt wieży telewizyjnej. Biuro projektowe Pieckert zaprojektowało system konstrukcyjny. Koncepcję wieży telewizyjnej, jej układ konstrukcyjny, wszystkie założenia do obliczeń statycznych, oszacowanie nakładów finansowych i pierwsze pomiary osiadań fundamentów podane zostały w jednej z prac Leonhardta. W tej pracy zasugerowano także potrzebę pomiaru odpowiedzi wieży telewizyjnej na działanie wiatru. Jako pierwszy dokonał tego Lenk w 1959 roku. W latach 1977 i 1995 stwierdzono pionowe pęknięcia w żelbetowym trzonie wieży, które następnie zostały naprawione. Przyczyny tych pęknięć wyjaśniono jako konsekwencje promieniowania słonecznego i dobowych zmian temperatury powietrza działających na trzon wieży telewizyjnej, wywołujących deformacje płaszcza trzonu. Naprężenia termiczne spowodowały zmienną w czasie „owalizację” trzonu wieży, która z biegiem lat doprowadziła do zmęczenia materiału, czego skutkiem były wyraźnie widoczne podłużne pęknięcia po przeciwnych stronach trzonu wieży telewizyjnej. Autorom niniejszego artykułu nie są znane wcześniejsze pomiary charakterystyk dynamicznych wieży telewizyjnej związane z naprawą powstałych pęknięć. W związku z tym, w 1999 roku autorzy przeprowadzili pierwszą serię pomiarów przemieszczeń wierzchołka wieży telewizyjnej z zastosowaniem techniki satelitarnej GPS. Metodologia pomiarów była podobna do metodologii stosowanej przez innych badaczy. Na tej podstawie autorzy potwierdzili możliwość zastosowania systemu GPS do monitorowania przemieszczeń statycznych, quasi-statycznych i dynamicznych oraz do określania podstawowych charakterystyk dynamicznych (częstotliwości drgań własnych i współczynników tłumienia drgań) istniejących dużych konstrukcji w skali naturalnej. Autorzy cyklicznie monitorowali przedmiotową wieżę telewizyjną do roku 2015. Jednak pomimo podjętego wysiłku w celu zebrania dodatkowych danych pomiarowych, niestety w 2013 i 2015 r. nie było możliwości pomiaru przemieszczeń wieży telewizyjnej pod wpływem silnego wiatru. Niemniej jednak autorzy dokonali analizy danych pomiarowych zgromadzonych w latach 2002, 2005, 2006, 2007, 2008 i 2011, które obejmowały pomiary w zakresie prędkości wiatru od małej do dużej. W dniach 18-19 stycznia 2007 r. w pobliżu wieży zarejestrowano porywy wiatru o prędkości 26 m/s, co spowodowało jej przemieszczenia w zakresie decymetrów.

15

Modal characterization of sandwich skew plates

Pavan-Kumar Dhotre, Srinivasa Chikkol V.

Acta Mechanica et Automatica

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2021

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Vol. 15, no. 3

143--153

EN

The current work focuses on the experimental and finite element free vibration studies of laminated composite sandwich skew plates. The comparison was made between the experimental values obtained by the Fast Fourier transform (FFT) analyzer and a finite el-ement solution obtained from CQUAD8 finite element of The MacNeal-Schwendler Corporation (MSC) / NASA STRucture Analysis (NAS-TRAN) software. The influence of parameters such as aspect ratio (AR) (a/b), skew angle (α), edge condition, laminate stacking sequence, and fiber orientation angle (θ°) on the natural frequencies of sandwich skew plates was studied. The values obtained by both the finite el-ement and experiment approaches are in good agreement. The natural frequencies increase with an increase in the skew angle for all giv-en ARs.

16

Experimental evaluation of the effects of structural changes on the vibration properties of ck35 steel

Yazani Navid Moshtaghi

Acta Mechanica et Automatica

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2021

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Vol. 15, no. 2

53--57

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.

17

Optimization of fundamental natural frequency of structures using VPL on the example of truss towers

Wirowski Artur

Vibrations in Physical Systems

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2020

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Vol. 31, nr 2

art. no. 2020229

EN

The work describes the use of VPL to optimize fundamental natural frequency of structures based on the example of steel lattice towers. For this purpose, a universal programming tool in Python using FEM was created, which allows the optimization of any bar structure in terms of its natural frequency. The capabilities of the tool are illustrated in several examples. It has been shown that by changing the tower geometry it is possible to obtain its higher spatial rigidity with a small increase in mass, it is possible to control the frequencies and forms of natural vibrations. Finally, the possibilities of further development of VPL applications in optimization of fundamental natural frequency of constructions and generative architecture were discussed.

18

Residual life estimation of healthy and cracked composite beam using experimental and numerical modal analysis methods

Ramprasad Gedela, Ramakrishna Shinigam

Journal of Mechanical and Energy Engineering

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2020

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Vol. 4, No 2

127--134

EN

Preventive maintenance is beneficial to minimize unexpected breakdowns in industries with continuous production. Composite structures are used for naval applications like ship hulls and marine propellers. In most of the industries, composite structural health analysis using experimental and numerical model are available for damage detection and estimate the residual life of composite beams. The present work is focusses on identification of damage and estimate residual life of composite healthy and cracked beams. Free vibrational analysis is carried out on composite beam made of Glass fiber reinforced polymer (GFRP) with a different crack orientation. A Fast Fourier Transform (FFT) spectrum analyzer associated with engineering data management (EDM) software utilized for experimental analysis to detect presence of damage in cracked composite beam. Finite element method (FEM) software called Analysis of composite pre/post (ACP) available in ANSYS R3 is used to compare the natural frequency results of healthy composite beam with cracked composite beam with different ply orientations. For validation of numerical modal evaluation, the consequences acquired from ANSYS R3 Finite element analysis (FEA) software are in comparison with experimental results received by impact hammer method. The fatigue life of a damaged composite beam is estimated the use of “Hwang and Han’s” fatigue life equation.

19

Hybrid sandwich panels: a review

Sandeep S. H., Srinivasa C. V.

International Journal of Applied Mechanics and Engineering

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2020

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Vol. 25, no. 3

64--85

EN

A high specific stiffness, high specific strength, and tailoring the properties for specific application hale attracted the attention of the researchers to work in the field of laminated composites and Sandwich structures. Rapid use of these laminated composites and Sandwich structures necessitated the development of new theories that suitable for the bending, buckling and vibration analysis. Many articles were published on free vibration of beams, plates, shells laminated composites and sandwich structures. In this article, a review on free vibration analysis of shear deformable isotropic beams, plates, shells, laminated composites and sandwich structures based on various theories and the exact solution is presented. In addition to this, the literature on finite element modeling of beams, plates, shells laminated composites and sandwich structures based on classical and refined theories is also reviewed. The present article is an attempt to review the available literature, made in the past few decades on free flexural vibration response of Fiber Metal laminated Composites and Sandwich panels using different analytical models, numerical techniques, and experimental methods.

20

Impact of Whip Roller Parameters on Warp Dynamic Loads for 3D Fabrics Made on a Four-Comb Warp-Knitting Machine

Michalak Andrzej, Kuchar Maciej, Mikołajczyk Zbigniew

Autex Research Journal

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2020

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Vol. 20, no. 1

73--77

EN

The most advantageous geometry of the warp feeding system was determined from the viewpoint of compensating temporary changes in the warp length during the technological cycle of a four-comb warp-knitting machine. Dynamic simulations of the feeding system were carried out for 3 different lengths of the shift of the slider with a guide bar – designating variants (series) of the cross-sectional sizes of the 3D knitted fabrics. The courses of instantaneous warp tensions during the operating cycle of the warp-knitting machine were presented. Limit dynamic loads of the warp were determined and presented as a function of natural frequency of the whip roller. Based on the criterion of the smallest dynamic loads of the warp, the optimum natural frequencies of the whip roller were determined. In the analyzed range of the whip roller parameters, they are 3–6 times greater than the operation frequency of the warp-knitting machine.