Dynamic characterizations of underwater structures using non-contact vibration test based on nanosecond laser ablation in water: Investigation of cavitation bubbles by visualizing shockwaves using the Schlieren method

Naoki Hosoya, Itsuro Kajiwara, Koh Umenai

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

A pulsed-laser ablation method for non-contact experimental vibration analysis of completely submerged underwater structures is proposed. Although impact testing with an impulse hammer is commonly used for vibration analysis due to its simplicity, impact testing has limited use in underwater conditions. An input-detection-free frequency response function measurement in water will greatly contribute to the development of high-precision and high-speed positioning autonomous underwater vehicles, underwater vehicle-manipulators, underwater robots, submarines, etc., which are used in dangerous conditions (e.g., deep oceans, under ice, and nuclear reactor plants). To achieve these high-performance underwater systems, vibrations due to hydrodynamic parameters (such as added mass, buoyant force, drag force, and damping coefficient) should be suppressed, and vibration tests should be conducted on the actual equipment submerged in water. The proposed method yields the frequency response function by applying a pulsed-laser-ablation excitation force to an underwater structure and measuring the output using a laser Doppler vibrometer. Because the direction, strength, and effective duration of the pulsed-laser-ablation force are essentially constant, this force can be estimated by measuring these properties in advance. Hence, the proposed method realizes input-detection-free frequency response function measurements in underwater conditions.

Original languageEnglish
Pages (from-to)3649-3658
Number of pages10
JournalJVC/Journal of Vibration and Control
Volume22
Issue number17
DOIs
Publication statusPublished - 2016 Oct 1

Keywords

  • cavitation bubble
  • frequency response function
  • laser ablation
  • modal analysis
  • non-contact vibration test
  • Underwater structure

ASJC Scopus subject areas

  • Automotive Engineering
  • Materials Science(all)
  • Aerospace Engineering
  • Mechanics of Materials
  • Mechanical Engineering

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