(ScienceDirect, 2024-04) John Kiprotich Birir, Michael James Gatari , Mohamed Subair Syed Akbar Ali and Prabhu Rajagopal
Detection of defects located close to design features such as welds and supports remains a
challenge in guided
ultrasonic wave inspection, primarily due to the
diffraction limit. Although
metamaterial based approaches hold promise, the best previous work in this regard required
placing a sensor right above the defect location to achieve resolution. Here, a novel angled channel
metamaterial concept is proposed to overcome this limitation, thus permitting placing of a sensor
at an offset from the defect location. The concept is demonstrated and discussed using simulations
validated by experiments. It is shown that sub-wavelength resolution of crack-like defects is
possible using the angled channel
metamaterial offset by a distance of up to half the
wavelength. The
operating
physics of this problem is further discussed using simulations and analysis,
bringing out the
strengths and limitations of the proposed technique, highlighting the benefits for
guided wave screening of hidden regions.
