Generation of harmonic waves in beams using boundary excitation. (August 2019)

• Record Type: Journal Article
• Authors: Kumar, Aman; DasGupta, Anirvan
• Is Part Of: International journal of mechanical sciences. Volume 159(2019)
• Page Start: 234
• Page End: 245
• Publication Date: 2019-08
• Subjects: Boundary excitation -- Normal modes -- Traveling waves -- Harmonic waves -- Boundary stiffness; Mechanical engineering -- Periodicals; Génie mécanique -- Périodiques; Mechanical engineering; Maschinenbau; Mechanik; Zeitschrift; Periodicals; 621.05
• DOI: 10.1016/j.ijmecsci.2019.05.021
• Languages: English
• ISSNs: 0020-7403

Abstract

Highlights: A novel form of boundary excitation generates a simple harmonic travelling wave. An insight into the role of natural modes of the beam on wave generation is presented. An optimum boundary stiffness results in a better harmonic wave generation. The existence of a critical material loss factor in case of internally damped beams is observed. The basic result is validated using finite element simulation. Graphical abstract: Abstract: A novel approach for generating transverse harmonic waves in beams with boundary excitation is proposed. The excitation ansatz at the two boundaries involves certain unknown amplitudes and phases. For a desired harmonic wave in the beam, the problem of determination of the corresponding excitation amplitudes and phases is posed as a nonlinear minimization problem, which is subsequently solved by a standard random search algorithm. This basic analytical model is validated using a 3D-FEM model developed in ANSYS. A concept of modal participation is introduced to estimate the theoretical best harmonic wave that can be produced in a beam, and compare with that actually achieved. Fixing a beam on to the actuators may result in support stiffening. Interestingly, it is found that an optimal boundary stiffening can improve traveling wave generation. The analysis of the effect of internal dissipation shows the existence of a critical material loss factor which relatively suppresses the generation of harmonic waves at a given frequency. The effect of beam length and pre-tension on wave generation is also studied.