Nonlinear ultrasonic stimulated thermography for damage assessment in isotropic fatigued structures

Gian Piero Malfense Fierro, Danielle Calla, Dmitri Ginzburg, Francesco Ciampa, Michele Meo

Research output: Contribution to journalArticle

27 Citations (Scopus)
164 Downloads (Pure)

Abstract

Traditional non-destructive evaluation (NDE) and structural health monitoring (SHM) systems are used to analyse that a structure is free of any harmful damage. However, these techniques still lack sensitivity to detect the presence of material micro-flaws in the form of fatigue damage and often require time-consuming procedures and expensive equipment. This research work presents a novel “nonlinear ultrasonic stimulated thermography” (NUST) method able to overcome some of the limitations of traditional linear ultrasonic/thermography NDE-SHM systems and to provide a reliable, rapid and cost effective estimation of fatigue damage in isotropic materials. Such a hybrid imaging approach combines the high sensitivity of nonlinear acoustic/ultrasonic techniques to detect micro-damage, with local defect frequency selection and infrared imaging. When exciting structures with an optimised frequency, nonlinear elastic waves are observed and higher frictional work at the fatigue damaged area is generated due to clapping and rubbing of the crack faces. This results in heat at cracked location that can be measured using an infrared camera. A Laser Vibrometer (LV) was used to evaluate the extent that individual frequency components contribute to the heating of the damage region by quantifying the out-of-plane velocity associated with the fundamental and second order harmonic responses. It was experimentally demonstrated the relationship between a nonlinear ultrasound parameter (βratio) of the material nonlinear response to the actual temperature rises near the crack. These results demonstrated that heat generation at damaged regions could be amplified by exciting at frequencies that provide nonlinear responses, thus improving the imaging of material damage and the reliability of NUST in a quick and reproducible manner.

Original languageEnglish
Pages (from-to)102-115
Number of pages14
JournalJournal of Sound and Vibration
Volume404
Early online date27 May 2017
DOIs
Publication statusPublished - 15 Sep 2017

Keywords

  • Laser vibrometer
  • LDR
  • Nonlinear ultrasound
  • Thermography
  • Thermosonics

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Acoustics and Ultrasonics
  • Mechanical Engineering

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