Time domain characteristics for sub-wavelength defect in one-dimensional structure

The characteristics for sub-wavelength defect have been theoretically investigated through time domain simulation. The calculation is based on a one-dimensional structure which contains copper and water. The reflected ultrasonic signal for different frequencies is obtained. The normalized mean steady-state pressure is oscillating periodically when the ratio of defect size and wavelength changes from 0.0025 to 1. These results can be used to determine the sub-wavelength defect characteristics such as material and size from the wave magnitude and oscillating periods in ultrasonic testing.