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Analiza mostów wiszących w opracowaniach Stephena Timoshenki

Dąbrowiecki Krzysztof

Nowoczesne Budownictwo Inżynieryjne

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2022

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Nr 2

86--88

PL

29 maja 2022 r. minie 50 lat od śmierci Stephena Timoshenki, amerykańskiego naukowca ukraińskiego pochodzenia, autora znanych prac z teorii sprężystości, teorii stateczności sprężystej, wytrzymałości materiałów oraz mechaniki budowli. Tym artykułem chcę przypomnieć czytelnikom mniej znany wkład tego wybitnego uczonego w teorię mostów wiszących.

2

Analiza modalna narzędziem mechaniki stosowanej w identyfikacji stanu budowli

Żółtowski M.

Logistyka

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2014

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nr 6

PL

Istnieje potrzeba ciągłego doskonalenia metod badania drganiowego elementów budowlanych i całych konstrukcji narażonych na destrukcję. Wprowadzane do budownictwa nowe materiały i technologie oraz nowe rozwiązania konstrukcyjne, umożliwiają zwiększenie wydajności i jakości wytworów, lecz towarzyszą im często groźne i duże obciążenia dynamiczne. Nowe narzędzia w tym obszarze badań dotyczą możliwości wykorzystania metod analizy modalnej, a także nowoczesnego pozyskiwania i przetwarzania procesu drganiowego. Do oceny jakości inżynierii produkcji konstrukcji i elementów murowych wykorzystuje się ostatnio wiele różnych estymatorów drganiowych, które stanowią podstawę nowych metod badawczych (analiza modalna) co stanowi podstawę rozważań tej pracy.

EN

There is a need for continuous improvement of vibration testing methods of building elements and whole structures exposed to destruction. Introduced for building new materials and technologies and new engineering solutions for performance and quality creations, but often accompanied by severe and large dynamic loads. New tools in this area of research relate to the possibility of use of modal analysis method, as well as a modern acquiring and processing of vibration process. To assess the quality of the design and manufacturing engineering masonry recently used a number of different estimators of vibration, which are the basis a new research methods (modal analysis) as a basis for discussion of this work.

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Analytical solution of the time fractional Fokker-Planck equation

Sutradhar T., Datta B. K., Bera R. K.

International Journal of Applied Mechanics and Engineering

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2014

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Vol. 19, no. 2

435--440

EN

A nonperturbative approximate analytic solution is derived for the time fractional Fokker-Planck (F-P) equation by using Adomian’s Decomposition Method (ADM). The solution is expressed in terms of Mittag-Leffler function. The present method performs extremely well in terms of accuracy, efficiency and simplicity.

4

Boundary conditions in models of power plant components under thermal loading

Okrajni J., Twardawa M.

Archives of Materials Science and Engineering

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2013

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Vol. 62, nr 1

28--35

EN

Purpose: The main purpose of the work is the description of conditions of fatigue process of power plant components working under mechanical and thermal loading. The work focuses on the chosen component characteristics. The issue of influence of the heat transfer conditions on the component surface on stresses changes in time has been discussed. Design/methodology/approach: The FEM modelling method has been used to describe the behaviour of the chosen component. The models have been validated on the basis of temperature measurements during operation period. Findings: It has been shown that the determination of the effects induced by unsteady conditions of start-up and shut-down of installations requires application of unconventional methods of research and analysis of their results. In such a case, a methodology can be applied consisting in combining the methods of computer modelling of temperature fields with temperature measurements in selected points of the component. Research limitations/implications: The presented analysis is the part of the complex investigation method which main purpose is increasing the accuracy of the thermo-mechanical fatigue process description. In such situation the investigations curried out in the work give the model approach and data for the comparison the real behaviour with the predictions. However the work is focused only on the chosen component and chosen characteristics of loading. Practical implications: The method of the chosen component behaviour analysis used in the paper could be useful in the practical cases when the real components mechanical behaviour would be analysed and their fatigue life would be assessed. Originality/value: The main value of this paper is the own method of the mechanical behaviour analysis of the power plant components. This method includes FEM modelling and assumption that the heat transfer coefficient should be treated as dependent on time. The material stress-strain behaviour has been treated as the local phenomenon that could be modelled.

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Stephen Timoshenko - ojciec mechaniki stosowanej (okres emigracyjny). cz. 2

Dąbrowiecki K.

Nowoczesne Budownictwo Inżynieryjne

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2010

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Nr 4

70-72

PL

W numerze 1 (22) "Nowoczesnego Budownictwa Inżynieryjnego" z 2009 r. ukazała się pierwsza część materiału poświęconego prof. Stephenowi Timoshence (Stiepanowi Prokofiewiczowi Timoszence) 1878.1972, światowej sławy specjaliście w dziedzinie mechaniki stosowanej Artykuł ten opisywał działalność profesora w okresie przedemigracyjnym. Jednak najwięcej szeroko znanych prac naukowych napisał i opublikował, będąc na emigracji w Stanach Zjednoczonych i właśnie tego okresu jego życia i działalności dotyczy poniższy artykuł.

6

Parameter identification of a full-car model for active suspension design

Guida D., Nilvetti F., Pappalardo C. M.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 40, nr 2

138-148

EN

Purpose: A method for identifying parameters of a full-car model for active suspension design Design/methodology/approach: The method is based on ERA/OKID identification procedure developed by Juang [1]. Findings: Numerical results show a good agreement with real system parameters. Research limitations/implications: Results show that this method works well only with a high signal-to-noise ratio. Practical implications: This method can be used as an aid to active suspension design. Originality/value: This procedure has been tested on the full-car model of suspension system in two cases: a) full-state measurements; b) not full-state measurements.

7

Life and operational safety of power systems and chemical plants

Okrajni J.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 43, nr 1

38-63

EN

Purpose: The problem addressed in the paper is the description of an effort and durability of components under the conditions of mechanical and thermal interactions. The problems of proper material testing methods have been shown as the important part of the components life assessment methodology. Design/methodology/approach: The FEM modelling has been used to determine the stress and strain fields in the components and to describe their behaviour under mechanical and thermal loading. Findings: An appropriate models description has been developed. So far, experimental verification of the usefulness of the model description to determine the stress and strain patterns in particular object and for chosen operation conditions has been made. Research limitations/implications: The developed description should be useful in problems of behaviour predictions of high temperature components and their durability assessment under different mechanical and thermal loadings in industry practical applications. Originality/value: The method, which more precise description of power industry components behaviour makes possible have been shown in the work. The work is addressed to researchers interested in problems of component behaviour prediction under different loadings that we can meet in the operation practice and to power industry engineering maintenance staff.

8

Graphs different category of subsystem as models to synthesis of transverse vibrating beam - system

Buchacz A.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 43, nr 2

644--650

EN

Purpose: of this paper is modeling by different categorygraphs and analysis of vibrating clamped - free beam as subsystem of transverse vibrating beam-system by the exact and approximate methods and creating the hypergraphs of the beams in case of presented methods of analysis. Design/methodology/approach: was to nominate the relevance or irrelevance between the characteristics obtained by considered methods - especially concerning the relevance of the natural frequencies-poles of characteristics of considered beam. The main subject of the research is the continuous clamped - free beam with constant cross sections as a subsystem of transverse vibrating beam - system. Findings: this approach is fact, that approximate solutions fulfill all conditions for vibrating beams and can be introduction to synthesis of these systems modeled by different category graphs. Research limitations/implications: is that linear continuous transverse vibrating clamped-free beam is considered. Practical implications: of this study is the main point is the introduction to synthesis of transverse vibrating continuous beam-systems with constant changeable cross-section. Originality/value: of this approach relies on application approximate methods of analysis of clamped - free beam and modeling the one of transformed hypergraph.

9

Dry friction of bearings on dynamics and control of an inverted pendulum

Guida D., Nilvetti F., Pappalardo C. M.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 38, nr 1

80-94

EN

Purpose: Investigation of dry friction parameters on the control system of a cart pendulum. Design/methodology/approach: A geometrical approach has been used to analyze the influence of bearing friction on the cart-pendulum dynamics. This approach was developed by one of authors in the paper “ Influence of the Variation between Static and Kinetic Friction on Stick-Slip Instability” pubblished by WEAR 1993. Findings: Relations that allow us to evaluate how the friction parameters of bearings influence the performances of the control system of a cart-pendulum. Research limitations/implications: The “a priori knowing” of friction parameters is the intrinsic limitation of this method. Originality/value: A novel methodology for designing of more effective control systems.

10

Computer models of steam pipeline components in the evaluation of their local strength

Okrajni J., Essler W.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 39, nr 1

71-78

EN

Purpose: The paper discusses the issue of modelling the heating and cooling processes of T-pipes in a power plant pipeline in the start-up conditions of a boiler. The main purpose of this work is the description of the mechanical behaviour of power plant components working under mechanical and thermal loading and validation of the computer modelling methods. Design/methodology/approach: The FEM modelling has been used to describe the local stress-strain behaviour of the chosen component. Findings: The reasons for the presence of high and variable in time temperature gradients in the components of the main steam pipeline include, among other things, variable values of the coefficient of heat transfer between the pipeline material and the medium flowing inside it, which, at this stage of boiler operation, may change its state. Unsteady operation of a pipeline, especially in case of subsequent boiler start-ups, may induce thermal stresses which exceed the values of allowable stress in components of complex shapes. Research limitations/implications: The possibility of applying the durability criteria currently assumed in standards still requires justification and confirmation in laboratory and industrial conditions to be closer to the real components behaviour. In such situation the presented analysis is the part of the complex investigation method which main purpose is increasing accuracy of the TMF process description and thermo-mechanical life assessment. Practical implications: The calculations carried out may constitute a basis for developing a material test parameters which would bring closer the fatigue conditions appearing locally in the analysed components. The method of stress-strain behaviour analysis used in the paper could be useful in the practical cases when the real components mechanical behaviour would be analysed. Originality/value: The main value of this paper is the own method of the mechanical behaviour analysis of the power plant component. This method includes the temperature fields analysis taking into account the boundary conditions based on the operation parameter data and the thermoplastic material model. The material stress-strain behaviour has been treated as the local phenomenon, that could be modelled by FEM.

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Analysis of probability as an impulse to synthesis of a beam-system represented by hypergraphs

Buchacz A.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 38, nr 1

72-79

EN

Purpose: of this paper is to analyze vibrating beam by an exact and approximate methods and to create hypergraphs of the beam in case of two methods of analysis. Design/methodology/approach: was to nominate the relevance or irrelevance between the characteristics obtained by the considered methods - especially concerning the relevance of the natural frequency-poles of beam characteristics. The main subject of the research is a continuous free beam as a subsystem of vibrating beam-system with constant cross sections. Findings: this approach is that approximate solutions fulfil all conditions for vibrating beams and can be an introduction to synthesis of these systems modelled by hypergraphs. Research limitations/implications: linear continuous flexibly vibrating free beam is considered Practical implications: of this study is mainly the introduction to synthesis of flexibly vibrating continuous beam-systems. Originality/value: of this approach is about application of approximate methods of analysis of a beam and modelling the one of transformed hypergraph.

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Stephen Timoshenko - ojciec mechaniki stosowanej (okres przedemigracyjny). cz. 1

Dąbrowiecki K.

Nowoczesne Budownictwo Inżynieryjne

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2009

|

Nr 1

86-88

PL

Życiorys "ojca mechaniki stosowanej" Stephena Timoshenki. W artykule przedstawione zostały jego losy do roku 1922, kiedy to opuścił na stałe Europę i wyemigrował do Ameryki.

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Thermo-mechanical fatigue conditions of power plant components

Okrajni J.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 33, nr 1

53-61

EN

Purpose: The main purpose of this work is the description of the mechanical behaviour of power plant components working under mechanical and thermal loading that cause the thermo-mechanical fatigue fracture in selected areas of the component surfaces. Design/methodology/approach: The computer modelling has been used to describe the local stress-strain behaviour of the chosen component. Findings: The values of variable in time temperature strains and stresses in selected points of the power plant header were determined. The points were located at the edges of holes through which water steam is supplied and carried away, where under use conditions the presence of cracks can be observed. That stresses and mechanical strains caused by the influence of a non-uniform temperature field may be significantly higher in comparison with the stresses and strains caused by the pressure inside the analysed component. Tensile thermal stresses of high values are created especially under conditions of sudden cooling during unsteady work of a power unit. Research limitations/implications: The possibility of applying the durability criteria currently assumed in standards still requires justification and confirmation in laboratory and industrial conditions to be closer to the real components behaviour. In such situation the presented analysis is the part of the complex investigation method which main purpose is increasing accuracy of the TMF process description and thermo-mechanical life assessment. Practical implications: The calculations carried out may constitute a basis for developing a material test parameters which would bring closer the fatigue conditions appearing locally in the analysed components. The method of stress-strain behaviour analysis used in the paper could be useful in the practical cases when the real components mechanical behaviour would be analysed. Originality/value: The main value of this paper is the own method of the mechanical behaviour analysis of the power plant component. This method includes the temperature fields analysis taking into account the boundary conditions based on the operation parameter data and the thermoplastic material model. The material stress-strain behaviour has been treated as the local phenomenon, that could be modelled by FEM.

14

Longitudinal vibrations of mechanical systems with the transportation effect

Buchacz A., Żółkiewski S.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 32, nr 1

29-36

EN

Purpose: this thesis purpose is a new way of modelling systems working with high speeds of mechanisms. Systems are analyzed with taking into consideration the rotational movement and with criterions of using materials with high flexibility and high precision of work. The dynamical analysis was done with giving into consideration the interaction between working motion and local vibrations. During the motion a model is loaded by longitudinal forces. Design/methodology/approach: equations of motion were derived by the Lagrange method, with generalized coordinates and generalized velocities assumed as orthogonal projections of individual quantities of the rod and manipulators to axes of the global reference frame. Findings: the model of longitudinally vibrating systems in plane motion was derived, after that the model can be transformed to the dynamical flexibility of these systems. Derived equations are the beginning of analysis of complex systems, especially can be used in deducing of the substitute dynamical flexibility of multilinked systems in motion. Research limitations/implications: mechanical systems vibrating longitudinally in terms of rotation were considered in this thesis. Successive problem of the dynamical analysis is the analysis of systems in spatial transportation and systems loaded by transversal forces. Practical implications: effects of presented calculations can be applied into machines and mechanisms in transportation such as: high speed turbines, wind power plant, water-power plants, manipulators, aerodynamics issues, and in different rotors etc. Originality/value: the contemporary analysis of beams and rods were made in a separate way, first working motion of the main system and next the local vibrations. A new way of modelling took into consideration the interaction between those two displacement. There was defined the transportation effect for models vibrating longitudinally in this paper.

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Investigation of flexibly vibrating subsystem of mechatronic system

Buchacz A.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 34, nr 1

55-62

EN

Purpose: of this paper is to investigate the transients of characteristics of vibrating beams obtained by the exact and approximate methods and to answer to the question – if the method can be used to nominate the characteristics of mechatronic systems. Design/methodology/approach: was to nominate the relevance or irrelevance between the characteristics obtained by considered methods – especially concerning the relevance of the natural frequencies-poles of characteristics of mechanical part of mechatronic system. The main subject of the research is the continuous vibrating beam. Findings: this approach is fact, that approximate solutions fulfill all conditions for vibrating beams and some conditions only, particularly for vibrating beams as the subsystems of mechatronic systems. Research limitations/implications: is that linear continuous flexibly vibrating beam is considered. Practical implications: of this study is the main point is the analysis and the examination of flexibly vibrating discrete-continuous mechatronic systems which characteristics can be nominated with approximate methods only. Originality/value: of this approach relies on the comparison of the compatibility of the characteristics of the mechatronic and mechanical systems with demanded accuracy, nominated with approximate method.

16

Exact and approximate analysis of mechanical and mechatronic systems

Buchacz A.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 33, nr 1

47-52

EN

Purpose: of this paper is to compare the transients of characteristics obtained by the approximate method and exact one and to answer to the question – if the method can be used to nominate the characteristics of mechatronic systems. Design/methodology/approach: was to nominate the relevance or irrelevance between the characteristics obtained by considered methods – especially concerning the relevance of the pole values of characteristics. The main subject of the research is the continuous torsionally vibrating bar considered as a mechanical subsystem of the mechatronic system. Findings: this approach is fact, that approximate solutions fulfill all conditions for vibrating bars and some conditions only, particularly for flexibly vibrating beams. Research limitations/implications: is that linear continuous torsionally vibrating bar is considered. Practical implications: of this study is the main point is the analysis and the examination of torsionaly vibrating continuous mechatronic systems which characteristics can be nominated with similar methods only. Originality/value: of this approach relies on the comparison of the compatibility of the characteristics of the mechatronic and mechanical systems with demanded accuracy, nominated with similar method.

17

Dynamical flexibility of the free-free damped rod in transportation

Żółkiewski S.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 35, nr 1

71-78

EN

Purpose: of this thesis is derivation of dynamical flexibility of the free-free rod system in transportation. The well-known problem of dynamical analysis of systems in rotational transportation was developed in this work to systems with taking into consideration damping forces. Design/methodology/approach: The dynamical flexibility method was used to analysis of the free-free rod’s vibrations. Mathematical models derived in previous articles were used to derivation of the dynamical flexibility. Considerations were done by the Galerkin’s method. Findings: There were considered systems in rotational motion treated in this thesis as main transportation. Dynamical characteristics in form of dynamical flexibility as function of frequency and mathematical models were presented in this work. Research limitations/implications: Analyzed systems were simple linear homogeneous not supported rods. Working motion was limited to plane rotational motion. Future works would consider complex systems and nonlinearity. Practical implications: of derived dynamical characteristics can easily support designing process and can be put to use in stability analysis and assigning stability zones. Thank to derived mathematical models the numerical applications can be implemented and some calculations can be automated. Originality/value: Analyzing models are rotating flexible free-free rods with taking into consideration the damping forces.

18

Crack arrest saturation model under combined electrical and mechanical loadings

Bhargava R. R., Setia A.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 37, nr 2

544-548

EN

Purpose: The investigation aims at proposing a model for cracked piezoelectric strip which is capable to arrest the crack. Design/methodology/approach: Under the combined effect of electrical and mechanical loadings applied at the edges of the strip, the developed saturation zone is produced at each tip of the crack. To arrest further opening of the crack, the rims of the developed saturation zones are subjected to in-plane cohesive, normal uniform constant saturation point electrical displacement. The problem is solved using Fourier integral transform method which reduces the problem to the solution of Fredholm integral equation of the second kind. This integral equation in turn is solved numerically. Findings: The expressions are derived for different intensity factors and energy release rate. A qualitative analysis of the parameters affecting the arrest of opening of the crack and fatigue crack growth with respect to strip thickness and material constants are presented graphically. Research limitations/implications: The investigations are carried out by considering the material electrical brittle. Consequently, the zones protrude along the straight lines ahead of the crack tips. And further, the small scale electrical yielding conditions are used. Practical implications: Piezoelectric materials are widely getting used nowadays, even in day to day life like piezoelectric cigarette lighter, children toys etc. And, its advance used in technology like transducers, actuators has been already in progress. So, the aspect of cracking of piezoelectric materials are of great practical importance. Originality/value: The piezoelectric material under the combined effect of electrical and mechanical loadings gives the assessment of electrical displacement which is required to arrest the crack. The various useful interpretations are also drawn from the graphs.

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Analysis of complex damped longitudinally vibrating systems in transportation

Żółkiewski S.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 36, nr 2

176-183

EN

Purpose: of this thesis is dynamical analysis of complex systems in transportation. Analyzed systems are composed of rotatable rods. Transportation was defined as main motion of rods and the overall system. Design/methodology/approach: The dynamical flexibility method is a leading methodology for dynamic analysis of considered systems. For solving equations of motion to dynamical flexibility the Galerkins method was used. Findings: There were considered systems consisted of rods. Rods are rotated first round the origin of global reference frame simultaneously, the attached point and further ones round the end of the previous one. Charts of dynamic characteristics, in a form of dynamic flexibility as function of frequency and mathematical models were shown in this article. Research limitations/implications: All multi-body systems components were simple linear homogeneous rods, the first one as the fixed rod and next ones treated as free-free rods. Transportation was limited to plane rotational motion round the Z axis of global reference frame. Future works would consider complex systems with geometrical and physical nonlinearity. Practical implications: of presented analysis are derivation of multi-body rod systems of dynamic flexibility. Dynamic flexibility can be used in designing process. Presented mathematical models may be used for implementation in numerical applications and for automating some calculations in this type of systems. Originality/value: In the mathematical model the damping forces were taken into consideration and the dynamic flexibility of complex systems was derived.

20

Spectral element modelling of the thermally induced vibration of an axially moving plate

Lee U., Kwon K.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 26, nr 1

65-72

EN

Purpose: To develop a spectral element model for accurate prediction of the dynamic characteristics of an axially moving thin uniform plate subjected to sudden thermal loadings on its surfaces. Design/methodology/approach: First, we have derived the governing equations of motion by using the Hamilton's principle. Secondly, we have used the wave solutions, which satisfy the governing equations of motion in the frequency domain, as the frequency-dependent shape functions to formulate the spectral element matrix by using the variational approach. Thirdly, the extremely high accuracy of the spectral element model has been evaluated by comparing the dynamic responses obtained by the spectral element analysis with the results obtained by using the conventional finite element analysis. Findings: It has been numerically shown that the present spectral element model provides very accurate dynamic responses of an axially moving uniform plate by treating the whole plate as a single finite element, regardless of its length. Practical implications: Numerical investigations have shown that the thermally induced vibration characteristics of an axially moving plate depends on the duration and frequency characteristics of externally applied thermal loadings as well as its moving speed. Originality/value: The paper is the first to develop the spectral element model for the axially moving plates subjected to thermal loadings. The present spectral element model can be applied to the galvanized steel strip passing through a hot zinc tank, for instance.