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This paper investigates the vibrational behavior of a system which consists of two free–free Timoshenko beams interconnected by a nonlinear joint. To model the bolted lap joint interface, a combination of the linear translational spring, linear and nonlinear torsional springs, and a linear torsional damper is used. The governing equations of motion are derived using the Euler–Lagrange equations. The reduced-order model equations are obtained based on Galerkin method. The set of coupled nonlinear equations are then analytically solved using the harmonic balance approach and numerical simulation. A parametric study is carried out to reveal the influence of different parameters such as linear and nonlinear torsional spring, linear translational spring, and linear torsional damper on the vibration and stability of the bolted lap joint structure. It is shown that the effect of the nonlinear torsional spring on the response of the system is significant. Interestingly, it is observed that in the presence of the nonlinear spring the softening behavior could be changed to hardening behavior. In addition, the effects of the different engineering beam theories on the modeling of the substructures are studied and it is observed that considering the effect of the rotary inertia and shear deformations is significant. In addition, it is observed that neglecting each of them can yield completely wrong interpretations of the system behavior and incorrect results.

The present paper deals with free vibration analysis of laminated composite skew plates with and without cut-outs. The experimental investigation along with numerical simulation has been presented in this paper for complete understanding of the dynamic behaviour of laminated skew plates with cut-out. Glass fibre-reinforced laminated composite plates have been prepared by resin infusion process using vacuum bagging technique in the laboratory for experimental analysis. The experimental studies have been carried out on skew composite plates with varying size of cut-out placed at the centre. The numerical analysis has been carried out by developing a computer code in MATLAB. Special attention is drawn on the formulation of mass matrix by considering effect of rotary inertia. The results obtained by the finite element formulation using nine-noded isoparametric plate-bending elements are validated by comparing the results from relevant published literature. The numerical and experimental data are then compared for experimental verification of present investigation. The consistency of mode shapes between experimental and numerical investigations is checked by using modal assurance criteria.

The nonlinear axial-lateral-torsional free vibration of the rotating shaft is analyzed by employing the Rayleigh beam theory. The effects of lateral, axial and torsional deformations, gyroscopic forces and rotary inertia are taken into account, but the shear deformations are neglected. In the new developed dynamic model, the nonlinearities are originated from the stretching of beam centerline, nonlinear curvature and twist and inertial terms which leads to the coupling between the axial, lateral and torsional deformations. The deformed configuration of the cross section of the beam is represented by the axial and lateral deformations, also the geometry of the beam in the deformed configuration is represented by Euler angles. A system of coupled nonlinear differential equations is obtained which is examined by the method of multiple scales and the nonlinear natural frequencies are determined. The accuracy of the solutions is inspected by comparing the free vibration response of the system with the numerical integration of the governing equations. The effect of the spin speed and radius-to-length ratio of the rotating shaft on the free vibrational behavior of the system is inspected. The study demonstrates the effect of axial-lateral-torsional coupling on the nonlinear free vibrations of the rotating shaft.

A procedure for deriving the complete equations of motion to compute an isolator’s displacement due to strong ground motion is applied to structures isolated with friction pendulum systems. The resulting equations, which contain the vertical inertia forces, were studied to estimate the influence of these forces on the isolator’s behavior. The nonlinear equation is solved employing the technique of successive approximations. The results obtained showed that the influence of the vertical inertia forces on structural response is negligible for the case of a long-distance ground motion, while becoming significant for a near-source ground motion. On the other hand, very small values of the isolator’s radius R cause an increase of the aforementioned influence.

In this paper, primary resonances of a cantilever flexible shaft carrying a rigid disk at its free end (overhung rotor) are investigated. Unbalance forces due to eccentricity and disk skew are simultaneously considered, and the shaft has initially static deflection due to the rotor’s weight which causes asymmetry in the equations of motion. The rotor has large amplitude vibrations, which lead to nonlinearities in curvature and inertia. In the model, rotary inertia and gyroscopic effects are included, but shear deformation is neglected. The method of multiple scales is applied to the discretize differential equations of motion. It is shown that the static deflection creates second-order nonlinear terms and near the primary resonances only the forward modes are excited. With considering the gravity, the inertial nonlinearities become stronger near the primary resonances. So, gravity decreases the hardening effect, and the nonlinear system tends to a linear system. It is concluded that the gravity effect has a softening effect. By using this property of gravity, a relation between weight and external forces is derived, in which by applying this relation the jumping phenomenon is eliminated. Numerical examples are presented, and the result is verified by numerical simulations.

In this study, vibration characteristics of a tapered laminated thick composite plate have been investigated using finite element method by including the shear deformation and rotary inertia effects. The governing differential equations of motion of a tapered laminated thick composite plate are presented in the finite element formulation based on first-order shear deformation theory for three types of taper configurations. The effectiveness of the developed finite element formulation in identifying the various dynamic properties of a tapered laminated thick composite plate is demonstrated by comparing natural frequencies evaluated using the present FEM with those obtained from the experimental measurements and presented in the available literature. Various parametric studies are also performed to investigate the effect of taper configurations, aspect ratio, taper angle, angle ply orientation and boundary conditions on free and forced vibration responses of the structures. The comparison of the transverse free vibration mode shapes of the uniform and tapered composite plates under various boundary conditions is also presented. The forced vibration response of a composite plate is investigated to study the dynamic response of tapered composite plate under the harmonic force excitation in various tapered configurations. It is concluded that the dynamic properties of laminated thick composite plates could be tailored by dropping off the plies to yield various tapered composite plate.

Piezoelectric inertia motors use the inertia of a body to drive it by means of a friction contact in a series of small steps. It has been shown previously in theoretical investigations that higher velocities and smoother movements can be obtained if these steps do not contain phases of stiction (“stick-slip” operation), but use sliding friction only (“slip-slip” operation). One very promising driving option for such motors is the superposition of multiple sinusoidal signals or harmonics. In this contribution, the theoretical results are validated experimentally. In this context, a quick and reliable identification process for parameters describing the friction contact is proposed. Additionally, the force generation potential of inertia motors is investigated theoretically and experimentally. The experimental results confirm the theoretical result that for a given maximum frequency, a signal with a high fundamental frequency and consisting of two superposed sine waves leads to the highest velocity and the smoothest motion, while the maximum motor force is obtained with signals containing more harmonics. These results are of fundamental importance for the further development of high-velocity piezoelectric inertia motors.

In this paper, a continuous model for flexural vibration of beams with a vertical edge crack including the effects of shear deformation and rotary inertia is presented. The crack is assumed to be an open-edge crack perpendicular to the neutral plane. A quasi-linear displacement filed is suggested for the beam, and the strain and stress fields are calculated. The governing equation of motion for the beam has been obtained using Hamilton principle. The equation of motion is solved with a modified weighted residual method, and the natural frequencies and mode shapes are obtained. The results are compared to the results of similar model with Euler–Bernoulli assumptions and finite element model to confirm the advantages of the proposed model in the case of short beams.

In this paper, formulation of the thin cylindrical shell via the modified couple stress theory by taking account of shear deformation and rotary inertia is obtained. To do this, the study developed the first shear deformable cylindrical shell theory by considering the size effects via the couple stress theory and the equations of motion of shell with classical and non-classical boundary conditions were extracted through Hamilton’s principle. In the end, as an example, free vibrations of the single-walled carbon nanotube (SWCNT) were investigated. Here, the SWCNT was modeled as a simply supported shell, and the Navier procedure was used to solve the vibration problem. The results of the new model were compared with those of the classical theory, pointing to the conclusion that the classical model is a special case of the modified couple stress theory. The findings also demonstrate that the rigidity of the nano-shell in the modified couple stress theory compared with that in the classical theory is greater, resulting in the increase in natural frequencies. In addition, the effect of the material length scale parameter on the vibrations of the nano-shell in different lengths and thickness was investigated.

In this paper, an efficient thin-walled Timoshenko laminated beam subjected to variable forces is developed for the coupled stability and free vibration analyses. First, the analytical technique is employed to present the thin-walled laminated beam theory considering the transverse shear and the restrained warping induced shear deformation and the rotary inertia based on the orthogonal Cartesian coordinate system. The displacement field of thin-walled cross section is introduced based on the inclusion of second-order terms of finite rotation and the potential energy corresponding to the semitangential moments and the kinetic energy with rotary inertia effects are derived. The equations of motion are derived from the Hamilton’s principle, and the explicit expressions for displacement parameters are presented based on generalized power series expansions of displacement components. Finally, the exact (i.e., with arbitrary precision) static and dynamic stiffness matrices are determined using the force-displacement relations. Numerical examples are carried out focusing attention in the validation of the present theory with respect to other available results.

A new analytical solution for free lateral vibration of a rotating Timoshenko shaft with various boundary conditions is presented in this paper. Gyroscopic and rotary inertia effects, as well as the couplings associated with the shear deformation in Timoshenko shaft, are considered in the equation of motion. Both forward and backward undamped natural frequencies can be obtained for simply supported (S-S), clamped-clamped (C-C), clamped-simply (C-S), clamped-free (C-F) and clamped-guided (C-G) boundary conditions using state-space approach. A centrifugally induced axial force, which is produced as a result of Poisson’s ratio, is also included in the equation of motion. The effect of this axial force on the lateral natural frequencies is investigated as the rotational speed increases. Numerical results and illustrative examples are given and comparisons are made between the results of the present method and those of the previous works.

A spectral finite element method is proposed to investigate the stochastic response of an axially loaded composite Timoshenko beam with solid or thin-walled closed section exhibiting bending–torsion materially coupling under the stochastic excitations with stationary and ergodic properties. The effects of axial force, shear deformation (SD) and rotary inertia (RI) as well as bending–torsion coupling are considered in the present study. First, the damped general governing differential equations of motion of an axially loaded composite Timoshenko beam are derived. Then, the spectral finite element formulation is developed in the frequency domain using the dynamic shape functions based on the exact solutions of the governing equations in undamped free vibration, which is used to compute the mean square displacement response of axially loaded composite Timoshenko beams. Finally, the proposed method is illustrated by its application to a specific example to investigate the effects of bending–torsion coupling, axial force, SD and RI on the stochastic response of the composite beam.

Dynamic stability behavior of the shear-flexible composite beams subjected to the nonconservative force is intensively investigated based on the finite element model using the Hermitian beam elements. For this, a formal engineering approach of the mechanics of the laminated composite beam is presented based on kinematic assumptions consistent with the Timoshenko beam theory, and the shear stiffness of the thin-walled composite beam is explicitly derived from the energy equivalence. An extended Hamilton’s principle is employed to evaluate the mass-, elastic stiffness-, geometric stiffness-, damping-, and load correction stiffness matrices. Evaluation procedures for the critical values of divergence and flutter loads of the nonconservative system with and without damping effects are then briefly introduced. In order to verify the validity and the accuracy of this study, the divergence and flutter loads are presented and compared with the results from other references, and the influence of various parameters on the divergence and flutter behavior of the laminated composite beams is newly addressed: (1) variation of the divergence and flutter loads with or without the effects of shear deformation and rotary inertia with respect to the nonconservativeness parameter and the fiber angle change, (2) influence of the internal and external damping on flutter loads whether to consider the shear deformation or not.

In this study, free vibration analysis of a uniform, rotating, cantilever Timoshenko beam featuring bending–bending-torsion coupling is performed. To the best of the authors’ knowledge, there is no explicit formulation in open literature for rotating Timoshenko beams featuring bending–bending-torsion coupling. Therefore, in this study, derivation of the kinetic and the potential energy expressions for the mentioned beam model is carried out in a detailed way by using several explanatory tables and figures. The parameters for the hub radius, rotational speed, rotary inertia, shear deformation and bending–bending-torsion coupling are incorporated into the energy expressions. The governing differential equations of motion are obtained by applying the Hamilton’s principle to the derived energy expressions and solved using an efficient mathematical technique, called the differential transform method. The natural frequencies are calculated, and comparisons are made with the results in open literature. Consequently, it is observed that there is a good agreement between the results, which validates the accuracy of the derived formulation and the built beam model.

Free transverse vibration and buckling of a double-beam continuously joined by a Winkler elastic layer under compressive axial loading with the influence of rotary inertia and shear are considered in this paper. The motion of the system is described by a homogeneous set of two partial differential equations, which is solved by using the classical Bernoulli–Fourier method. The boundary value and initial value problems are solved. The natural frequencies and associated amplitude ratios of an elastically connected double-beam complex system and the analytical solution of the critical buckling load are determined. The presented theoretical analysis is illustrated by a numerical example, in which the effect of physical parameters characterizing the vibrating system on the natural frequency, the associated amplitude ratios and the critical buckling load are discussed.

This paper deals with the eigenfrequencies of flexural vibration of a homogeneous rotor model which includes shear, rotary inertia and the gyroscopic effect. A formula for the critical speeds of this rotor has also been found. It appears that the effect of these factors is smaller when the critical speed increases and the ratio of slenderness of a rotor decreases.