Non-contact vibration tests with detection-free input based on pulsed-laser ablation for underwater structures

Naoki Hosoya, Shuichi Yahagi, Itsuro Kajiwara

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

This paper proposes a method of a non-contact experimental vibration analysis for underwater structures by pulsed-laser ablation. The impact testing with impulse hammer is used widely for vibration analysis due to the simplicity of the apparatus. However, the impact testing has limitations in use in underwater condition because of contact method by the experimenter. The proposed method yields the frequency response functions by applying apulsed-laser- ablation excitation force to the structure and measuring the output using a laser Doppler vibrometer. Since the direction, strength and effective duration of the pulsed-laser-ablation force are essentially constant, this force can be calibrated by measuring these properties in advance. Therefore input-detection-free frequency response function measurements can be realized. The method is validated by comparing frequency response functions obtained using laser excitation with FEM. Additionally, the frequency response function obtained in underwater conditions shows that the natural frequency decreases and the amplitude is attenuated by comparing with frequency response function in air conditions.

Original languageEnglish
Pages (from-to)2426-2437
Number of pages12
JournalNihon Kikai Gakkai Ronbunshu, C Hen/Transactions of the Japan Society of Mechanical Engineers, Part C
Volume78
Issue number791
DOIs
Publication statusPublished - 2012

Fingerprint

Underwater structures
Laser ablation
Pulsed lasers
Frequency response
Impact testing
Vibration analysis
Laser excitation
Hammers
Natural frequencies
Finite element method
Lasers
Air

Keywords

  • Frequency Response Function
  • Laser Ablation
  • Laser Measurement
  • Modal Analysis
  • Non-Contact Vibration Testing
  • Pulsed-Laser-Ablation Excitation Force
  • Underwater Structure

ASJC Scopus subject areas

  • Mechanical Engineering
  • Mechanics of Materials
  • Industrial and Manufacturing Engineering

Cite this

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title = "Non-contact vibration tests with detection-free input based on pulsed-laser ablation for underwater structures",
abstract = "This paper proposes a method of a non-contact experimental vibration analysis for underwater structures by pulsed-laser ablation. The impact testing with impulse hammer is used widely for vibration analysis due to the simplicity of the apparatus. However, the impact testing has limitations in use in underwater condition because of contact method by the experimenter. The proposed method yields the frequency response functions by applying apulsed-laser- ablation excitation force to the structure and measuring the output using a laser Doppler vibrometer. Since the direction, strength and effective duration of the pulsed-laser-ablation force are essentially constant, this force can be calibrated by measuring these properties in advance. Therefore input-detection-free frequency response function measurements can be realized. The method is validated by comparing frequency response functions obtained using laser excitation with FEM. Additionally, the frequency response function obtained in underwater conditions shows that the natural frequency decreases and the amplitude is attenuated by comparing with frequency response function in air conditions.",
keywords = "Frequency Response Function, Laser Ablation, Laser Measurement, Modal Analysis, Non-Contact Vibration Testing, Pulsed-Laser-Ablation Excitation Force, Underwater Structure",
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N2 - This paper proposes a method of a non-contact experimental vibration analysis for underwater structures by pulsed-laser ablation. The impact testing with impulse hammer is used widely for vibration analysis due to the simplicity of the apparatus. However, the impact testing has limitations in use in underwater condition because of contact method by the experimenter. The proposed method yields the frequency response functions by applying apulsed-laser- ablation excitation force to the structure and measuring the output using a laser Doppler vibrometer. Since the direction, strength and effective duration of the pulsed-laser-ablation force are essentially constant, this force can be calibrated by measuring these properties in advance. Therefore input-detection-free frequency response function measurements can be realized. The method is validated by comparing frequency response functions obtained using laser excitation with FEM. Additionally, the frequency response function obtained in underwater conditions shows that the natural frequency decreases and the amplitude is attenuated by comparing with frequency response function in air conditions.

AB - This paper proposes a method of a non-contact experimental vibration analysis for underwater structures by pulsed-laser ablation. The impact testing with impulse hammer is used widely for vibration analysis due to the simplicity of the apparatus. However, the impact testing has limitations in use in underwater condition because of contact method by the experimenter. The proposed method yields the frequency response functions by applying apulsed-laser- ablation excitation force to the structure and measuring the output using a laser Doppler vibrometer. Since the direction, strength and effective duration of the pulsed-laser-ablation force are essentially constant, this force can be calibrated by measuring these properties in advance. Therefore input-detection-free frequency response function measurements can be realized. The method is validated by comparing frequency response functions obtained using laser excitation with FEM. Additionally, the frequency response function obtained in underwater conditions shows that the natural frequency decreases and the amplitude is attenuated by comparing with frequency response function in air conditions.

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