Solodov, Igor; University of Stuttgart; Germany
Solodov, I.; University of Stuttgart; Germany
Session: Composite Material - UT 2
Time: 13:30 - 13:50
Traditional ultrasonic methods of Non-Destructive Testing (NDT) consider attenuation and scattering of high-frequency (MHz range) ultrasound as the primary effects of its interaction with defects. The efficiency of acoustic wave-defect interaction relevant to damage detection and imaging can also be quantified by the amplitude of the defect vibration for given amplitude of a driving wave. The increase in local vibration of the damaged area is a key factor for enhancing efficiency and sensitivity of the so-called derivative effects in acoustic wave-defect encounter. They include e.g. nonlinear, thermal, acousto-optic, etc. responses also applied for NDT and acoustic imaging of damage. These secondary effects are normally relatively inefficient so that the corresponding NDT techniques require an elevated acoustic power and stand out from conventional acoustic NDT counterparts for their specific instrumentation particularly adapted to high-power ultrasonics.
In this presentation, a new approach to NDT and imaging of damage in composites is discussed based on frequency-selective acoustic activation of defects by means of Local Defect Resonance (LDR). A frequency match to the damage resonance provides an efficient energy delivery from the wave directly to the defect. Unlike the resonance of the entire specimen, LDR NDT addresses the impact of the defect severity to its own resonance response, which is far stronger and identifies (even possibly quantifies) the damage by its resonant response clearly distinguished and independent of the rest (intact) part of the specimen. The objective of the talk is to demonstrate that the frequency- and spatially-selective activation of defects via the concept of LDR is the way to boost efficiency and sensitivity of diagnostic imaging of damage by using derivative NDT methodologies. Multiple case studies to be considered include resonant imaging of various defects in composite materials via laser vibrometry, thermosonics, and nonlinear acoustic techniques.