A study of multi-acoustic black holes considering suitability of attachment positions for suppressing low-frequency vibrations on large motor

Abstract

Vibrations generated from machinery in various industries, such as the automotive, aerospace, and shipbuilding industries, must be suppressed for developing low-vibration and low-noise systems. High-frequency vibrations can be easily controlled via damping treatments; however, controlling vibrations in the low-frequency range generated from large machinery is a major challenge. In general, a substantial amount of damping material is required for suppressing low-frequency vibrations. This is unsuitable when developing low-cost, lightweight, and eco-friendly systems. To overcome the limitations, effective methods are required for suppressing these low-frequency vibrations. In this study, an effective method was proposed for suppressing vibrations in the low-frequency range using multiple acoustic black holes (multi-ABHs) considering the suitability values of the attachment positions, which were determined by flexural wave propagation and interactions between the multi-ABHs and structures. The suitability values of the attachment positions are proposed as non-dimensional parameters that are calculated using the structural intensity and mode superposition methods. For validating the proposed method, the vibration suppression characteristics were analyzed using a steel plate. The analyzed cases were categorized into six groups according to the suitability values of the attachment positions of the multi-ABHs. The largest reduction in vibrations was observed when the multi-ABHs were attached to the location with the highest suitability in the six cases. Finally, the multi-ABHs were applied to a large 2-pole motor considering the suitability values of the attachment positions, and the dominant vibrations at 60, 120, and 180 Hz frequencies were suppressed.