Abstract

Perpetual points have been defined in mathematics recently, and they arise by setting accelerations and jerks equal to zero for nonzero velocities. The significance of perpetual points for the dynamics of mechanical systems is ongoing research. In the linear natural, unforced mechanical systems, the perpetual points form the perpetual manifolds and are associated with rigid body motions. Extending the definition of perpetual manifolds, by considering equal accelerations, in a forced mechanical system, but not necessarily zero, the solutions define the augmented perpetual manifolds. If the displacements are equal and the velocities are equal, the state space defines the exact augmented perpetual manifolds obtained under the conditions of a theorem, and a characteristic differential equation defines the solution. As a continuation of the theorem herein, a corollary proved that different mechanical systems, in the exact augmented perpetual manifolds, have the same general solution, and, in case of the same initial conditions, they have the same motion. The characteristic differential equation leads to a solution defining the augmented perpetual submanifolds and the solution of several types of characteristic differential equations derived. The theory in a few mechanical systems with numerical simulations is verified, and they are in perfect agreement. The theory developed herein is supplementing the already-developed theory of augmented perpetual manifolds, which is of high significance in mathematics, mechanics, and mechanical engineering. In mathematics, the framework for specific solutions of many degrees of freedom nonautonomous systems is defined. In mechanics/physics, the wave-particle motions are of significance. In mechanical engineering, some mechanical system’s rigid body motions without any oscillations are the ultimate ones.

Highlights

  • Perpetual points (PPs) have been defined in mathematics recently [1]. e PPs of a dynamical system are obtained by setting accelerations and jerks of the equations of motion of a mechanical system equal to zero for nonzero velocities

  • The analytical solutions in the exact augmented perpetual manifolds and their augmented perpetual submanifolds for six types of forces are determined. e analytical results are examined with numerical simulations in three examples, and they are in very good agreement

  • E significance of this outcome is that the many different mechanical systems, in the exact augmented perpetual manifolds with the same characteristic differential equation, have the same general solution, independent of the type of system, and upon the external forcing can lead to particlesingle-frequency or multiple frequencies’ standing wave or motion directed single-frequency or multiple frequencies’ wave motions

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Summary

Introduction

Perpetual points (PPs) have been defined in mathematics recently [1]. e PPs of a dynamical system are obtained by setting accelerations and jerks of the equations of motion of a mechanical system equal to zero for nonzero velocities. In [19, 20] with proved theorems, the PPs in linear unforced natural mechanical systems are associated with rigid body modes/motions, and they form the perpetual manifolds. E perpetual manifold’s definition extended in [22] to the augmented perpetual manifolds defined by the state space of the solutions of external forced mechanical systems motions that all the accelerations are equal but not necessarily zero. E state spaces, with the solutions that all generalized coordinates are equal and the velocities are equal, are called exact augmented perpetual manifolds Based on these new definitions, a theorem written in [21] and proved in [22] defines the conditions for exact augmented perpetual manifolds solutions of mechanical systems. A shaft in torsional motion with a nonlinear energy sink attachment, examined through finite element model, is the second example. e third example is a five-degrees-of-freedom mechanical system

Theory
Corollary
Conclusions
Structural Matrices for Finite Element Formulation
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