Ultrasonic phase imaging of multilayred structures

Abstract

In case of thin laminates internal structure ultrasonic inspection, phase information is not widely used due to the masking effect of frontal face echo. The differential signal extraction (DSE) method allows to eliminate the masking effect of frontal echo and, in addition to this, gains the information from internal structure of investigated object. In publication DSE result was visualized directly and superior result was obtained. It was also offered to use the commonly used power spectra investigation. This type of investigation also exposed good results. This paper deals with phase information exploration for subsurface defects imaging in order to achieve the resolution better than wavelength of ultrasonic signals used for investigation. Phase information use can be applied at new value, if this type of processing is applied on DSE result. As side effect, coating thickness can me measured with high accuracy. All processing is done not on through transmission, but reflected signal, so the single-side inspection is available in this case. The absolute thickness measurement procedure still has to be developed and relative accuracy evaluated.