Abstract. The chaotic dynamics of the contact interaction of two beams described by the thirdapproximation hypothesis (the Pelekh--Sheremetyev model) are studied in the paper. There is a small clearance between the beams. One of the beams is subjected to the action of a transversal harmonic load. Contact pressure is determined by Kantor's method. The mathematical model of the beam structure taking into account the geometric nonlinearity and contact interaction. The system of partial differential equations reduces to the ordinary differential equations by the finite differences method with the approximation of the second order. The resulting system is solved by the Runge-Kutta methods of various orders. The chaotic vibrations of two beams were investigated by the methods of nonlinear dynamics. The reliability of the obtained results was grounded. The Lyapunov exponents are calculated by three different algorithms -Kantz, Wolf, Rosenstein. The 2D and 3D phase portraits and the Fourier power spectra, the Poincaré pseudo section were constructed. The phenomenon of frequency synchronization has been detected.Keywords -Contact interaction, 3d approximation beam, nonlinear dynamics, finite difference method, Runge-Kutta methods, geometric nonlinearity.
IntroductionBeams and beam structures are widely used in modern industry, machine building, rocket engineering, etc. Often such structures are subjected to various external dynamic influences. The study of nonlinear dynamics and contact interaction of beam structures is a very important issue at the present stage development of science. In the Russian and foreign scientific literature we can find a large number of works devoted to the study of Euler-Bernoulli [1], Timoshenko [2], Peleh-Sheremetev [3, 4] beams models, but there are no papers on the contact interaction of beams of third-order. A third-order mechanics model is used in this paper. The hypothesis of the third approximation is commonly called the Reddy hypothesis [5] in the foreign literature. But this theory was first described in [6]. It was shown in [4]. The Pelekh-Sheremetev hypothesis makes it possible to maximize the model to a threedimensional and to obtain the most accurate results. In 1964 two Ukrainian scientists M.P. Sheremetev and B.L. Pelekh [6] proposed a third-order theory. This theory was applied to the calculation of beams of plates and shells in publications [7]. Twenty-seven years later, in the works of Levinson [8] and Reddy [5,9], this model was reopened. Thus, the following situation has developed. In the Russian scientific press and in publications of scientists from several countries of Eastern Europe, the approximation of the deflection function by a polynomial of the third degree is associated with the names of M.P. Sheremetev and B.L. Pelekh. In the other works this theory is called the ReddyLevinson theory. We will adhere to the historical name -the Pelekh-Sheremetev model. The equations describing the dynamic processes are very difficult, so it is not possible to find an analytica...