Abstract
This article presents a novel chiral structure, consisting of Euler–Bernoulli beams connected to gyroscopic spinners.Anew type of boundary condition is introduced, which is referred to as a gyrohinge. In this system, flexural waves are coupled with rotational motion.Time-harmonic conditions are derived by assuming small nutation angles of the spinners. It is shown that the eigenfrequencies of a finite beam with gyro-hinges at one or both ends change dramatically with the moments of inertia and the spin and precession rates of the spinners. The formulation is then extended to elastic beams with periodically-spaced gyro-hinges, whose dispersion properties are investigated in detail. In particular, it is shown how stop-bands and standing modes are affected by the introduction of gyroscopic spinners at the junctions. It is also demonstrated that a periodic system composed of beams connected by gyro-hinges represents a good approximation of a gyrobeam, a theoretical structural element consisting of an elastic beam possessing a continuous distribution of stored angular momentum. The gyricity coefficient of a gyrobeam is then interpreted in terms of the physical parameters of the system of beams with gyroscopic spinners. This article opens a new perspective on the design and practical implementation of chiral mechanical systems.
Highlights
Chiral elastic systems have attracted increasing interest from the research community in recent years, due to their special dynamic properties
The theory of gyro-elastic beams is based on an elegant formulation, but it presents a serious drawback for the purpose of practical construction: the gyricity parameter appearing in the equations of motion is not defined in terms of physical quantities
The article is organised as follows: in section 2, we present the equations of motion of the gyroscopic spinner and the elastic beam in the transient regime
Summary
This article presents a novel chiral structure, consisting of Euler–Bernoulli beams connected to gyroscopic spinners. A new type of boundary condition is introduced, which is referred to as a gyrohinge. In this system, flexural waves are coupled with rotational motion. The formulation is extended to elastic beams with periodically-spaced gyro-hinges, whose dispersion properties are investigated in detail. It is shown how stop-bands and standing modes are affected by the introduction of gyroscopic spinners at the junctions. It is demonstrated that a periodic system composed of beams connected by gyro-hinges represents a good approximation of a gyrobeam, a theoretical structural element consisting of an elastic beam possessing a continuous distribution of stored angular momentum. This article opens a new perspective on the design and practical implementation of chiral mechanical systems
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