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Документ Analysis of Geometrically Nonlinear Vibrations of Functionally Graded Shallow Shells of a Complex Shape(Marcílio Alves, 2017) Awrejcewicz, Jan; Kurpa, Lidiya; Shmatko, T.Geometrically nonlinear vibrations of functionally graded shallow shells of complex planform are studied. The paper deals with a power-law distribution of the volume fraction of ceramics and metal through the thickness. The analysis is performed with the use of the R-functions theory and variational Ritz method. Moreover, the Bubnov-Galerkin and the Runge-Kutta methods are employed. A novel approach of discretization of the equation of motion with respect to time is proposed. According to the developed approach, the eigenfunctions of the linear vibration problem and some auxiliary functions are appropriately matched to fit unknown functions of the input nonlinear problem. Application of the R-functions theory on every step has allowed the extension of the proposed approach to study shallow shells with an arbitrary shape and different kinds of boundary conditions. Numerical realization of the proposed method is performed only for one-mode approximation with respect to time. Simultaneously, the developed method is validated by investigating test problems for shallow shells with rectangular and elliptical planforms, and then applied to new kinds of dynamic problems for shallow shells having complex planforms.Документ Applicatin of R-functions Theory to Nonlinear Vibration Problems of Laminated Shallow Shells with Cutouts(NTU "KhPI", 2016) Kurpa, Lidiya; Timchenko, Galina; Osetrov, AndreyIn present work an effective method to research geometrically nonlinear free vibrations of elements of thinwalled constructions that can be modeled as laminated shallow shells with complex planform is applied. The proposed method is based on joint use of R-functions theory, variational methods and Bubnov-Galerkin procedure. It allows reducing an initial nonlinear system of motion equations of a shallow shell to the Cauchy problem. The mathematical formulation of the problem is performed in a framework of the refined first-order theory. The appropriate software is created within POLE-RL program system for polynomial results and using C+ + programs for splines. New problems of linear and nonlinear vibrations of laminated shallow shells with cutouts are solved. To confirm reliability of the obtained results their comparison with the ones obtained using spline-approximation and known in literature is provided. Effect o f boundary condition on cutout is studied.Документ Application of R-Functions Theory to Study Parametric Vibrations and Dynamical Stability of Laminated Plates(Точка, 2013) Kurpa, Lidiya; Mazur, Olga; Tsukanov, IgorThe problem of nonlinear parametric vibrations and stability analysis of the symmetric laminated plates is considered. The proposed method is based on multimode approximation of displacements and solving series auxiliary linear tasks. The main feature of the work is the application of the R-functions theory, which allows investigating parametric vibrations of plates with complex shape and different boundary conditions.Документ Application of the R-Functions Method for Nonlinear Bending of Orthotropic Shallow Shells on an Elastic Foundation(NTU "KhPI", 2016) Kurpa, Lidiya; Lyubitska, KaterynaGeometrically nonlinear behavior of orthotropic shallow shells subjected to the transverse load and resting on Winkler’s foundation is investigated. On base of the R-function theory and variational methods problem's solution for shells with complex plan form is proposed. The algorithm to finding upper and lower critical loads is developed. The stress-strain state of shallow shells with the complex planform is investigated including different boundary conditions, properties of material and elastic foundation.Документ Application of the R-Functions Theory to Problems of Nonlinear Dynamics of Laminated Composite Shallow Shells and Plates: Review(NTU "KhPI", 2016) Kurpa, LidiyaA review of studies performed using the R-functions theory to solve problems of nonlinear dynamics of plates and shallow shells is presented. The systematization of results and studies for the problems of free and parametric vibrations and for problems of static and dynamic stability is fulfilled. Expansion of the developed original method of discretization for nonlinear movement equations on new classes of nonlinear problems is shown. These problems include researches of vibrations of antisymmetric laminated cylindrical and spherical panels; laminated composite shallow shells with variable thicknesss of the layers; functionally graded (FG) shallow shells and others. The basic issues that arise when using RFM are described. The future prospects of using the theory of R-functions for solving problems of nonlinear dynamics of plates and shallow shells with complex form are formulated. First of all this is an algorithms development and creation of the associated software to apply multi-modes approximations; improvement of approximation tools for nonlinear problems; investigation of the cracked functionally graded shallow shells; FG panels under thermal environments; parametric vibrations, static and dynamical stability of the multilayered and FG plates and shells.Документ Dynamical instability of laminated plates with external cutout(Elsevier Inc., 2016) Awrejcewicz, Jan; Kurpa, Lidiya; Mazur, OlgaA method to study dynamical instability and non-linear parametric vibrations of symmetrically laminated plates of complex shapes and having different cutouts is proposed. The first-order shear deformation theory (FSDT) and the classical plate theory (CPT) are used to formulate a mathematical statement of the given problem. The presence of cutoutses sentially complicates the solution of buckling problem, since the stress field is non-uniform. At first, a plane stress analysis is carried out using the variational Ritz method and the R-functions theory. The obtained results are applied to investigate buckling and parametric vibrations of laminated plates. The developed method uses the R-functions theory, and it may be directly employed to study laminated plates of arbitrary forms and different boundary conditions. Besides, the proposed method is numerical-analytical, what greatly facilitates a solution of similar-like non-linear problems. In order to show the advantage of the developed approach, instability zones and response curves for the layered cross- and angle-ply plates with external cutouts are constructed and discussed.Документ Dynamical stability and parametrical vibrations of the laminated plates with complex shape(Marcílio Alves, 2013) Kurpa, Lidiya; Mazur, Olga; Tkachenko, VictoriaThe problem of nonlinear vibrations and stability analysis for the symmetric laminated plates with complex shape, loaded by static or periodic load in-plane is considered. In general case research of stability and parametric vibrations is connected with many mathematical difficulties. For this reason we propose approach based on application of R-functions theory and varia-tional methods (RFM).The developed method takes into ac-count pre-buckle stress state of the plate. The proposed ap-proach is demonstrated on testing problems and applied to laminated plates with cutouts. The effects of geometrical pa-rameters, load, boundary conditions on stability regions and nonlinear vibrations are investigated.Документ Free vibration analysis of FGM shell with complex planform in thermal environments(Wydawnictwo Politechniki Łódzkiej, 2019) Awrejcewicz, Jan; Kurpa, Lidiya; Shmatko, TetyanaSummary. In the present study free vibrations of FGM shallow shells of an arbitrary planform in thermal environment are investigated via R-functions method (RFM). First-order shear deformation theory of shallow shells is employed. Material properties are assumed to be temperature-dependent and expressed as nonlinear functions of temperature. The generic material properties are not only functions of temperature, but also functions of thickness direction. It is supposed that material properties vary through thickness according to a power-law distribution of the constituent’s volume fraction. The developed method is based on the combined applications of the R-functions theory, variational Ritz’s method. A comparison of the obtained results with available ones is carried out for rectangular plates and shallow shells. Vibration of shell panels with complex planform and different boundary conditions including mixed ones are studied. Solution structures and related admissible functions for shells with complex planform have been constructed by the R-functions theory. The effect of the temperature rise, geometry of the shell, material properties and constituent volume fraction index is examined.Документ Geometrical analysis of vibrations of functionally graded shell panels using the R-functions theory(London Calling, 2017) Shmatko, T.; Kurpa, Lidiya; Bhaskar, AtulAn approach for investigation of geometrically nonlinear vibrations of functionally graded shallow shells and plates with complex planform is proposed. It combines the application of the R-functions theory (RFM), variational Ritz’s method, the procedure by Bubnov-Galerkin and Runge-Kutta method. The presented method is developed in the framework of the first–order shear deformation shallow shell theory (FSDT). Shell panels under consideration are made from a mixture of ceramics and metal. Power law of volume fraction distribution of materials through thickness is chosen. Investigation of nonlinear vibrations of functionally graded shallow shells and plates with arbitrary planform and different types of boundary conditions is carried out. Test problems and numerical results have been presented for one-mode approximation in time. Effect of volume fraction exponent, geometry of a shape and boundary conditions on the natural frequencies is brought out.Документ Geometrically non-linear vibration and meshless discretization of the composite laminated shallow shells with complex shape(NTU "KhPI", 2010) Kurpa, LidiyaTo study the geometrically non-linear vibrations of the composite laminated shallow shells with complex plan form the approach, based on meshless discretization, is proposed. Non-linear equations of motion for shallow shells based on the first order shear deformation shell theories are considered. The discretization of the motion equations is carried out by method based on expansion of the unknown functions in series for which eigenvectors of the linear vibration obtained by RFM (R-functions method) are employed as basic functions. The factors of these series are functions (generalizing coordinates) depending on time. Due to applying the basic variational principle in mechanics by Ostrogradsky-Hamilton the corresponding system of the ordinary differential equations by Euler is obtained The non-linear ordinary differential equations are derived in terms of amplitudes of the vibration modes. The offered method is expounded for multi-modal approximation of unknown functions. Backbone curves of the spherical shallow shell with complex plan form are obtained using only the first vibration mode by the Bubnov-Galerkin method. The effects of lamination schemes on the behavior are discussed.Документ Investigating geometrically nonlinear vibrations of laminated shallow shells with layers of variable thickness via the R-functions theory(Elsevier Inc., 2015) Awrejcewicz, Jan; Kurpa, Lidiya; Shmatko, T.A novel numerical/analytical approach to study geometrically nonlinear vibrations of shells with variable thickness of layers is proposed. It enables investigation of shallow shells with complex forms and different boundary conditions. The proposed method combines application of the R-functions theory, variational Ritz’s method, as well as hybrid Bubnov–Galerkin method and the fourth-order Runge–Kutta method. Mainly two approaches, classical and first-order shear deformation theories of shells are used. An original scheme of discretization regarding time reduces the initial problem to the solution of a sequence of linear problems including those related to linear vibrations with a special type of elasticity, as well as problems governed by non-linear system of ordinary differential equations. The proposed method is validated by the investigation of test problems for shallow shells with rectangular planform and applied to new vibration problems for shallow shells with complex planforms and variable thickness of layers.Документ Investigation of Geometrically Nonlinear Vibrations of Laminated Shallow Shells with Layers of Variable Thickness by Meshless Approach(Точка, 2013) Kurpa, Lidiya; Shmatko, T.Geometrically nonlinear vibrations of laminated shallow shells with layers of variable thickness are studied. Nonlinear equations of motion for shells based on the first order shear deformation and classical shells theories are considered. In order to solve this problem we use the numerically-analytical method proposed in work [1]. Accordingly to this approach the initial problem is reduced to consequences of some linear problems including linear vibrations problem, special elasticity ones and nonlinear system of ordinary differential equations in time. The linear problems are solved by the variational Ritz’ method and Bubnov-Galerkin procedure combined with the R-functions theory [2]. To construct the basic functions that satisfy all boundary conditions in case of simply-supported shells we propose new solutions structures. The proposed method is used to solve both test problems and new ones.Документ Investigation of the parametric vibration of the orthotropic plates subjected to periodic in plane forces by multi-modal approximation and R-functions method(NTU "KhPI", 2010) Awrejcewicz, Jan; Kurpa, Lidiya; Mazur, OlgaThe original method of studying parametric vibrations of orthotropic plate with complex shape is proposed. Suggested approach is based on combined application of variational methods and the R-functions theory. Using the proposed method and developed software the regular and chaotic regimes of T-shaped plate are analyzed.Документ Investigation of the Parametric Vibrations of Laminated Plates by RFM(NTU "KhPI", 2016) Kurpa, Lidiya; Mazur, Olga; Tkachenko, VictoriaThe R-functions theory is applied to study free vibration and dynamic instability of the symmetrically laminated plates subjected to combined static and periodic axial forces. It is assumed that subcritical state of the plate may be inhomogeneous. Theoretical formulation is made on the classical plate theory (CTP). The developed approach is based on combined application of Ritz’s method, Galerkin procedure, R-functions theory and Bolotin’s method. The buckling, instability zones and response curves for laminated plate with different external cutouts are presented and discussed. Effects of plate geometrical parameters, parking of layers, mechanical characteristics of the material on buckling, natural frequencies and parametric resonance are also studied.Документ Investigation of the stress-strain state of the laminated shallow shells by R-functions method combined with spline-approximation(WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2011) Awrejcewicz, Jan; Kurpa, Lidiya; Osetrov, AndreyThe bending behavior of the laminated shallow shells under static loading has been studied using the R functions theory together with the spline-approximation. Formulation is based on the first order shear deformation theory. Due to usage of the R-functions theory the laminated shallow shells with complex shape and different types of the boundary conditions can be investigated. Application of the spline-approximation allows getting reliable and validated results for non concave domains and domains with holes. The proposed method is implemented in the appropriate software in framework of the mathematical package MAPLE. The analysis of influence of certain factors (curvature, packing of layers, geometrical parameters, boundary conditions) on a stress-strain state is carried out for shallow shells with cut-outs. The comparison of obtained results with those already known from literature and results obtained by using ANSYS are also presented.Документ Large amplitude free vibration of orthotropic shallow shells of complex shapes with variable thickness(Marcílio Alves, 2013) Awrejcewicz, Jan; Kurpa, Lidiya; Shmatko, T.The present formulation of the analysed problem is based on Donell’s nonlinear shallow shell theory, which adopts Kirch-hoff’s hypothesis. Transverse shear deformations and rotary inertia of a shell are neglected. According to this theory, the non-linear strain-displacement relations at the shell midsurface has been proposed. The validity and reliability of the proposed approach has been illustrated and discussed, and then a few examples of either linear or non-linear dynamics of shells with variable thickness and complex shapes have been presented and discussed.Документ Multi-modal geometrical non-linear free vibrations of composite laminated plates with the complex shape(NTU "KhPI", 2010) Kurpa, Lidiya; Budnikov, N. A.Geometrically non-linear free vibrations of the composite laminated plates are investigated using new multi modal approach to discretization of motion equations . The non-linear governing equations for laminated plates are derived by Hamilton’s principle using first-order shear deformation theory. Due to proposed algorithm of the discretization all unknown functions except of transverse displacement are eliminated and governing equations are reduced to system of ordinary differential equations in time by the Bubnov-Galerkin procedure. The expansion of all unknown functions in the truncated Fourier series is performed using the eigenfunctions of the linear vibration problems and solutions of the sequence of elasticity problems. All auxiliary problems are solved by RFM (R-functions method).Документ Nonlinear vibration of orthotropic shallow shells of the complex shape with variable thickness(Wydawnictwo Politechniki Łódzkiej, 2011) Awrejcewicz, Jan; Kurpa, Lidiya; Shmatko, T.Early R-functions theory [1] combined with variational methods have been applied to linear [2] and nonlinear vibration problems [3,4] of the shallow shells theory of the constant thickness. In the present study, we first apply R-functions theory in order to investigate the geometrically nonlinear vibrations of orthotropic shallow shells of complex shape with variable thickness. Mathematical formulation is made in the framework of classical geometrically nonlinear theory of thin shallow shells. For a discretization of the original system in time, approximation of unknown functions is carried out by using a single mode approach. In order to construct a system of basic functions, the proposed algorithm includes sequence of the linear problems such as finding eigen functions of the linear vibrations of shallow shells with variable thickness and auxiliary tasks of the elasticity theory. The linear problems are solved by the R-functions method. The developed approach allows reducing the original problem to the corresponding problem of solving nonlinear ordinary differential equations (ODEs), whose coefficients are presented in analytical form. In order to solve the obtained system of ODEs the Bubnov-Galerkin method is applied. The proposed algorithm is implemented within an automated system POLE-RL [1]. Numerical examples of large-amplitude flexible vibrations of shallow orthotropic shells with complex shape and variable thickness are introduced demonstrating merits and advantages of the R-functions method. Comparison of the obtained results regarding shells with rectangular plans with the other methods confirms the reliability of the proposed method.Документ Nonlinear vibrations of functionally graded shallow shells of a complex planform in thermal environments(CongressLine Ltd., Hungary, 2017) Awrejcewicz, Jan; Kurpa, Lidiya; Shmatko, TatianaGeometrically nonlinear vibrations of FGM shallow shells of an arbitrary planform subjected to thermal environment are investigated with the use of R-functions theory and variational methods. Nonlinear firstorder shear deformation shallow shells are employed. Material properties are assumed to be temperaturedependent and varying along the thickness direction accordingly to Voigt’s law. The developed method is based on the combined applications of R-functions theory, variational Ritz’s method, procedure by Bubnov-Galerkin, and Runge-Kutta’s approach. The effect of the temperature rise, geometry of the shell, and constituent volume fraction index is examined. A comparison of the obtained results with available ones is also carried out for rectangular plates and shallow shells.Документ Nonlinear vibrations of shallow shells and thin plates of arbitrary shape(Springer, Dordrecht, 2005) Kurpa, Lidiya; Pilgun, Galina