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This paper considers oscillations of systems with a single-degree-of-freedom (SDOF) including fractional derivatives. The system is assumed to be an unforced condition. A general solution procedure that can be effectively applied to various types of fractionally damped models, where damping is defined by a fractional derivative, in engineering and physics is proposed. The nonlinearity of the mentioned models contains not only damping but can also consist of acceleration or displacement. This study proposed a new general model that includes but not limited to modified fractional versions of the well-known linear, quadratic, Coulomb and negative damped models. The method of multiple time scales is performed to obtain approximate analytical solutions. The solution, the amplitude, and the phase in the applications are plotted for various fractional derivative parameter values. In order to confirm their validity, our results for the case of the fractional derivative parameter equal to one are compared with others available in the literature. • A general model for nonlinear fractional systems is developed. • Modified fractionally versions of the well-known damped models have been proposed. • The efficiency of the proposed novel model has been demonstrated with applications. • The solution with the Fourier series is also applicable to fractional models. • The fractional derivative parameter variation affects the damping and the stiffness. [ABSTRACT FROM AUTHOR]

In this paper, we introduced response analysis and controlling the nonlinear vibration of van der pol duffing oscillator subject to parametric and external excitations by connecting the nonlinear integral positive position feedback (NIPPF). The controller combines the characteristics of the positive position feedback controller (PPF) and integral resonant control (IRC) and these controllers are viewed in a blocked scheme for the closed-loop system (system under control). The analytical solution and all resonance cases are obtained by applying the multiple time scales perturbation method (MSPM). The stability analysis is studied using the frequency response equations at the supposed worst resonance case. For numerical simulation, the system is examined before and after connecting the NIPPF controller using Matlab software program (package ode45). The influences of different parameters are examined numerically for the vibrating system and controller. The approximate analysis is confirmed with numerical simulation outcomes. Finally, making a comparison with previously related published work.

The internal resonance of a two degree-of-freedom mechanical system with all typical (quadratic and cubic) geometric nonlinearities is studied, limiting to the case of free dynamics. The Multiple Time Scale method is used to provide an analytical, closed form, approximation of the backbone curves. The cornucopia of different possible behaviours that can been obtained by varying the nonlinear stiffnesses is discussed in depth, illustrating them with some examples and verifying with numerical simulations. Some partially unexpected or relevant behaviours are highlighted, and some hints on how to exploit the proposed results to design nonlinearly tailored systems are given. [ABSTRACT FROM AUTHOR]

• A conditional equivalence between two multi-scale approaches to cable nonlinear dynamics is proposed. • For empirical functions, boundary effects in two formulations are nearly equivalent for medium and large inclinations. • Quantitative and qualitative differences between the two approaches are found for small boundary motion inclinations. • A new shape function is constructed, leading to an exact equivalence of the two formulations as regards boundary effects. • The theoretical framework is validated and shown to be computationally efficient by the finite difference method. A nonlinear cable excited by an inclined boundary motion, termed as cable's moving boundary problem, is attacked by two different perturbation approaches, i.e., the boundary modulation formulation and the quasi-static drift formulation. The former transforms the boundary motion into a weak modulation on cable's high-order dynamics, while the latter introduces a hybrid mode expansion using an empirical drift shape function. In both formulations, the inclined boundary motion induces three different excitation effects, i.e., longitudinal direct, vertical boundary kinematic, and high-order parametric, all of which being characterized by the parametric modulation factors. Detailed comparative studies indicate that the modulation factors in the two formulations are exactly equivalent to each other only if a new drift shape function, well defined in the boundary modulation formulation, is used for the quasi-static drift formulation. In contrast, the empirical shape functions lead only to an approximate equivalence for intermediate/large boundary motion inclinations. Moreover, for small inclinations, the two formulations induce possible quantitative and qualitative differences. The approximate analytical framework is validated and shown to be computationally efficient, by comparison with the finite difference method. [ABSTRACT FROM AUTHOR]

• Nonlocal strain gradient modeling for sandwich plates are presented. • Nonlinear vibration modeling with bi-nonlocal terms are obtained. • Higher-order theories are used to study small-scale parameters simultaneously. • This paper studies symmetric and also antisymmetric sandwich plates. • Non-uniform behaviors are reported in studying the effects of varying small-scale parameters. In this paper, a new model for studying the effects of small-scale parameters simultaneously, on large amplitude vibrations of sandwich plates is developed using the higher-order nonlocal strain gradient theory. Considering the higher-order theories for capturing the size effects of nanostructures results in a set of nonlinear partial differential (PD) equations, including bi-nonlocal terms. By employing Hamilton's principle, the equations of motion for symmetric and anti-symmetric sandwich plates are derived based on the classical plate theory. The partial nonlinear differential equations of motion are reduced to an ordinary differential equation for transverse vibrations of nanoplates using the Galerkin's method. An analytical solution procedure is employed to obtain the closed-form frequency equation as a function of the vibration amplitude, small-scale parameters and sandwich layers elasticity, density and thickness coefficients. Numerical results are presented in order to investigate the sandwich layers coefficients on nonlinear vibrational behavior of nanoplates as same as small-scale parameters and the amplitude of vibrations. It is found that the vibration amplitude plays the main role in nonlinear vibrational behavior of nanoplates in which, nonlinear frequency and its ratio to linear frequency will be increased by increasing it. Moreover, there are non-uniform behaviors by increasing the sandwich layers coefficients and small-scale parameters. In addition, in the case of large amplitude vibrations, effects of sandwich layers' coefficients and small-scale parameters on the nonlinear frequency and its ratio to linear frequency will become more noticeable. In order to validate the present solution procedure, the results are compared with those obtained from molecular dynamics simulations, the higher-order nonlocal strain gradient theory and the higher-order shear deformation plate theory. Image, graphical abstract [ABSTRACT FROM AUTHOR]

This study aims at investigating the nonlinear dynamic behavior of microscale carbon nanotube reinforced (CNTR) composite Euler–Bernoulli beams with a non-uniform cross-section, based on a modified couple stress theory (MCST). The nonlinear partial differential equations (PDEs) of motion are established based on the Von-Karman nonlinear strain–displacement relationship and Hamiltonian principle. The coupled PDEs are reduced to a single PDE, by neglecting the effects of the axial inertia and considering two different types of boundary conditions (i.e. clamped–clamped and clamped–free). At the same time, the single PDE is reverted to a nonlinear ordinary differential equation (ODE) by means of the Galerkin approach, and it is solved by using a semi-inverse method and the method of multiple time scales (MTS) for a free and forced vibration analysis, respectively. A large systematic numerical analysis is here performed to check for the sensitivity of the nonlinear response of CNTR composite beams to different boundary conditions and reinforcement parameters, with useful scientific insights for further computational investigations on the topic. • The nonlinear dynamic behavior of microscale carbon nanotube beams is analyzed. • A modified couple stress theory is combined to Von-Karman nonlinearities and Hamiltonian principle. • A semi-inverse and multiple time scales methods are applied to solve the nonlinear problem. • A sensitivity analysis is performed for different boundary conditions and reinforcement parameters. [ABSTRACT FROM AUTHOR]

In this paper, modified multiple time scale (MTS) method is employed to solve strongly nonlinear forced vibration systems. The first-order approximation is only considered in order to avoid complexicity. The formulations and the determination of the solution procedure are very easy and straightforward. The classical multiple time scale (MS) and multiple scales Lindstedt-Poincare method (MSLP) do not give desire result for the strongly damped forced vibration systems with strong damping effects. The main aim of this paper is to remove these limitations. Two examples are considered to illustrate the effectiveness and convenience of the present procedure. The approximate external frequencies and the corresponding approximate solutions are determined by the present method. The results give good coincidence with corresponding numerical solution (considered to be exact) and also provide better result than other existing results. For weak nonlinearities with weak damping effect, the absolute relative error measures (first-order approximate external frequency) in this paper is only 0.07% when amplitude A = 1.5 , while the relative error gives MSLP method is surprisingly 28.81%. Furthermore, for strong nonlinearities with strong damping effect, the absolute relative error found in this article is only 0.02%, whereas the relative error obtained by MSLP method is 24.18%. Therefore, the present method is not only valid for weakly nonlinear damped forced systems, but also gives better result for strongly nonlinear systems with both small and strong damping effect. [ABSTRACT FROM AUTHOR]

We address the nonlinear free vibration, superharmonic and subharmonic resonance response of homogeneous Euler–Bernoulli beams resting on nonlinear viscoelastic foundations, under a moving mass and an abrupt uniform temperature rise. The nonlinear differential equation of motion stemming from the Hamiltonian principle and Finite Strain Theory is discretized according to a Galerkin decomposition method, and is solved by means of a multiple time scale method. A comparison between the Finite Strain theory and the Von-Karman approach is discussed, accounting for the effect of temperature rise, linear and nonlinear coefficients of the elastic foundation on the nonlinear vibration history and phase trajectory. At the same time, we check for the sensitivity of the frequency response of the system in superharmonic and subharmonic resonance for different input parameters, namely, location, velocity, and magnitude of the moving load, temperature rise and elastic foundation. • Finite strain-based theory of Euler–Bernoulli beam. • Nonlinear free vibration, superharmonic and subharmonic resonance. • Nonlinear viscoelastic foundation in thermal conditions. • Beams subjected to a moving mass loading. [ABSTRACT FROM AUTHOR]

The frequency response curves of a non-uniform beam undergoing nonlinear oscillations are determined analytically by the multiple time scale method, which provides approximate, but accurate results. The axial inertia in neglected, and so the equations of motion are statically condensed on the transversal displacement only. The nonlinearity due to the stretching of the axis of the beam is considered. The effects of variable cross-section, of variable material properties and of the distributed axial loading are taken into account in the formulation. They have been illustrated by means of two examples and are also compared with existing results. The main result of this work is that the effects of any type of non-uniformity can be detected by simple formulas. [ABSTRACT FROM AUTHOR]

This work investigates the dynamics of a hinged–simply supported beam with an axial spring in the neighbourhood of a 3:1 internal resonance between two successive transversal vibration modes. Multiple time scale method is applied to the analytical model of the planar extensible-shearable beam with associated boundary conditions, and a second order approximate solution is obtained. The phenomena that we investigate occur on the resonant branch of the frequency response curve around the main natural frequency, and consists of a localized extra (bent) peak on that branch. Also some detached branches have been theoretically detected in the neighbourhood of this extra peak. The analytical frequency response curves are analysed extensively and have been compared with finite element numerical simulations, finding an overall good agreement. Stability of the analytical solutions is checked by computing the eigenvalues of the Jacobian matrix and looking at the sign of their real part. Strain energies due to flexural, axial, shear deformability and axial spring are determined and compared between each other to ascertain their relative importance. • Analytical and numerical studies on nonlinear dynamics of a beam–spring system. • 3:1 internal resonance between two successive transversal vibration modes. • The energy exchange between flexural modes with axial motion as a carrier. • Longitudinal BC can control hardening/softening dichotomy of nonlinear responses. • Detached solutions appear due to coupled longitudinal–transversal interactions. [ABSTRACT FROM AUTHOR]