Stability of motion of a two-mass system with nonlinear friction

This paper concerns the motion of different elastically coupled masses. One of the masses is subjected to a motive force, while the other mass is acted upon by friction. The motive force decreases linearly, while friction changes nonlinearly. The differential equations of motion are derived and are reduced to the standard form (after Bogolyubov). The averaging method is used to find steady-state solutions, one of which agrees with the exact steady-state solution of the initial system of equations. It is found that the actual conditions of stability of the steady-state solution are differ greatly from the conditions calculated on the basis of avaraged equations. These differences are due to the difference in the degrees of the characteristic Rouse-Hurwitz polynomials calculated on the basis of the initial and averaged equations. The analytical results are illustrated by modeling on a microcomputer. S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev; Regional Scientific Research and Experimental Design Institute, Kiev, Ukraine. Translated from Prikladnaya Mekhanika, Vol. 35, No. 8, pp. 94–100, August, 1999.     

Evaluation of autooscillation parameters in two-mass systems with dey friction

A system of two differential equations is used to describe the motion of a two-mass system subject to a constant force and viscous and dry friction. The relationship between dry friction and the relative sliding force is expressed in terms of an odd nonmonotonic function with a discontinuity of the second kind. The averaging method is used for analytical analysis. The initial system of differential equations is transformed into a system with rapidly rotating phase by introduction of special variables. Partical solutions of the first approximation equations are obtained, and their stability studied. S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev. Translated from Prikladnaya Mekhanika, Vol. 32, No. 8, pp. 87–94, August, 1996.     

Nonlinear vibration of a two-mass system with nonlinear stiffnesses

An analytical approach is developed for nonlinear free vibration of a conservative, two-degree-of-freedom mass–spring system having linear and nonlinear stiffnesses. The main contribution of the proposed approach is twofold. First, it introduces the transformation of two nonlinear differential equations of a two-mass system using suitable intermediate variables into a single nonlinear differential equation and, more significantly, the treatment a nonlinear differential system by linearization coupled with Newton’s method and harmonic balance method. New and accurate higher-order analytical approximate solutions for the nonlinear system are established. After solving the nonlinear differential equation, the displacement of two-mass system can be obtained directly from the governing linear second-order differential equation. Unlike the common perturbation method, this higher-order Newton–harmonic balance (NHB) method is valid for weak as well as strong nonlinear oscillation systems. On the other hand, the new approach yields simple approximate analytical expressions valid for small as well as large amplitudes of oscillation unlike the classical harmonic balance method which results in complicated algebraic equations requiring further numerical analysis. In short, this new approach yields extended scope of applicability, simplicity, flexibility in application, and avoidance of complicated numerical integration as compared to the previous approaches such as the perturbation and the classical harmonic balance methods. Two examples of nonlinear two-degree-of-freedom mass–spring system are analyzed and verified with published result, exact solutions and numerical integration data.     

Dynamics of a particle with friction and delay

We are interested in the motion of a simple mechanical system having a finite number of degrees of freedom subjected to a unilateral constraint with dry friction and delay effects (with maximal duration $\tau >0$). At the contact point, we characterize the friction by a Coulomb law associated with a friction cone. Starting from a formulation of the problem that was given by Jean-Jacques Moreau in the form of a second-order differential inclusion in the sense of measures, we consider a sweeping process algorithm that converges towards a solution to the dynamical contact problem. The mathematical machinery as well as the general plan of the existence proof may seem much too heavy in order to treat just this simple case, but they have proved useful in more complex settings.     

Analysis of a self-excited system with dry friction

A new approach to the modelling of systems in flow-induced self-excitation is presented. An elastically supported body situated in a channel carrying a flowing medium is analysed and the effect of additional dry friction is investigated. It is shown that in some flow velocity intervals several steady solutions of the mathematical model (locally stable equilibrium positions and steady vibrations) can exist. Their domains of attraction are determined.     

The dynamical nature of a backlash system with and without fluid friction

We study the dynamics of a simple system with backlash and impacts. Both the presence or the absence of fluid friction is considered. The fluid friction is modeled by a fractional derivative, but it is also shown how an inhomogeneous time scale, although not arising from a fractional differential equation, may lead to some features similar to fractional solutions.     

Experimental investigation of a single-degree-of-freedom system with Coulomb friction

This paper presents an experimental investigation of the dynamic behaviour of a single-degree-of-freedom (SDoF) system with a metal-to-metal contact under harmonic base or joined base-wall excitation. The experimental results are compared with those yielded by mathematical models based on a SDoF system with Coulomb damping. While previous experiments on friction-damped systems focused on the characterisation of the friction force, the proposed approach investigates the steady response of a SDoF system when different exciting frequencies and friction forces are applied. The experimental set-up consists of a single-storey building, where harmonic excitation is imposed on a base plate and a friction contact is achieved between a steel top plate and a brass disc. The experimental results are expressed in terms of displacement transmissibility, phase angle and top plate motion in the time and frequency domains. Both continuous and stick-slip motions are investigated. The main results achieved in this paper are: (1) the development of an experimental set-up capable of reproducing friction damping effects on a harmonically excited SDoF system; (2) the validation of the analytical model introduced by Marino et al. (Nonlinear Dyn, 2019. https://doi.org/10.1007/s11071-019-04983-x) and, particularly, the inversion of the transmissibility curves in the joined base-wall motion case; (3) the systematic observation of stick-slip phenomena and their validation with numerical results.     

Hopf bifurcations in a predator-prey system of population allelopathy with a discrete delay and a distributed delay

A delayed Lotka?CVolterra predator-prey system of population allelopathy with discrete delay and distributed maturation delay for the predator population described by an integral with a strong delay kernel is considered. By linearizing the system at the positive equilibrium and analyzing the associated characteristic equation, the asymptotic stability of the positive equilibrium is investigated and Hopf bifurcations are demonstrated. Furthermore, the direction of Hopf bifurcation and the stability of the bifurcating periodic solutions are determined by the normal form theory and the center manifold theorem for functional differential equations. Finally, some numerical simulations are carried out for illustrating the theoretical results.     

Resonant processes in a mechanical self-oscillatory system with delay

A calculation method for a mechanical system with delay in quasi-harmonic oscillatory conditions is proposed as the first-order approximation, on the assumption that the dry sliding-friction force is approximated polynomially by a finite number of components of the Taylor-series expansion; Pisarenko's hypothesis is adopted in taking energy dissipation into account. Ukrainian Transportation University, Kiev, Ukraine. Translated from Prikladnaya Mekhanika, Vol. 35, No. 2, pp. 90–97, February, 1999.     

Metastability and chaoslike phenomena in nonlinear dynamic buckling of a simple two-mass system under step load

Summary The nonlinear dynamic buckling based on the global response of a nonlinear autonomous dissipative or non-dissipative system with two degrees of freedom is studied in detail. Attention is focused on the unstable branch of the complementary path whose significant role on the mechanism of dynamic buckling is revealed for the first time in the literature. Theoretical results associated with distinct properties of the Jacobian matrix, verified and supplemented numerically, brought into light various new phenomena for certain values of the control parameter such as dynamic buckling of statically stable systems, metastability phenomena for loads much higher than the dynamic buckling loads, and sensitivity to initial conditions and to damping.

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Metastabilität und chaosähnliche Phänomene des nichtlinearen dynamischen Knickens eines einfachen Zwei-Masse-Systems unter Treppenlast

Übersicht Anhand der globalen Antwort eines autonomen, dissipativen oder nicht-dissipativen Systems mit zwei Freiheitsgraden auf eine stufenförmige Last werden detaillierte Studien zum nichtlinearen dynamischen Knicken angestellt. Die Betrachtung richtet sich besonders auf den instabilen Zweig des komplementären Lastpfades, dessen Bedeutung für das dynamische Knicken hier zum ersten Mal aufgezeigt wird. Die theoretischen und numerischen Ergebnisse, die mit bestimmten Eigenschaften der Jacobi-Matrix verknüpft sind, enthüllen für bestimmte Werte des Kontrollparameters verschiedene neue Phänomene wie das dynamische Knicken von statisch stabilen Systemen, Metastabilität für Lasten weit über der dynamischen Knicklast und Empfindlichkeit auf Anfangsbedingungen und Dämpfung.

     

Estimation of Lyapunov exponents for a system with sensitive friction model

Mathematical modelling and numerical analysis of a vibrating system with dry friction is presented. Three qualitatively different friction characteristics are considered. One of them is an example of so-called sensitive friction characteristic. Their influence on the dynamics on the attractor of the friction oscillator is investigated through bifurcational analysis. This analysis is supported by Lyapunov exponents estimated using approach for the systems with discontinuities. Theoretical background for such a synchronisation-based method of determining the largest Lyapunov exponent is explained. The results obtained through the proposed approach approximate the LLE with a good precision.     

Interaction of rotational and vibrational motions in a flywheel system with a friction clutch

Translated from Prikladnaya Mekhanika, Vol. 32, No. 3, pp. 86–94, March, 1996.     

Dynamics analysis of a non-smooth Filippov pest-natural enemy system with time delay

In this paper, we propose a non-smooth Filippov system that describes the interaction of the pest and natural enemy with considering time delay, which represents the change in the growth rate of natural enemies before it is released to prey on pests. When the number of the pest is below the threshold, no control is applied; otherwise, control measures will be adopted. We discuss the stability of the equilibria and the existence of Hopf bifurcation. The results show that the Hopf bifurcation occurs when the time delay passes through some critical values. By applying the Filippov convex method, we obtain the dynamics of the sliding mode. The solutions of the system eventually tend toward the regular equilibrium, the pseudo-equilibrium or a standard periodic solution. Numerical simulations show that time delay plays an important role in local and global sliding bifurcations. We can obtain boundary focus bifurcations from boundary node bifurcations by varying time delay. Furthermore, touching, buckling and crossing bifurcations can be obtained frequently by increasing time delay. The results can provide some insights in pest control.