Non-Destructive Testings (NDT) are used to verify products quality without modifying their characteristics and performances. At present, automatic devices are available to individuate the position of a defect inside a solid structure. However, no technique is available to determine automatically the defect type. NDT on steel samples by means of ultrasounds is here analyzed. This technique is based on the reflection of an ultrasonic signal, due to presence of a possible defect. Two kinds of defects (non-metallic inclusions and porosities) have been investigated. The signal reflected by the defect has been studied by means of frequency analysis. It has been observed that some spectra characteristics are the same for the same kind of defect. This result is not available by using only a time domain analysis. A simple mathematical model has been found by correlating experimental results. Defects dimensions have been found out to be strictly correlated with spectra (- 6dB) frequency bandwidth. Correlation depends on the kind of the investigated defect.
Frequency Analysis for ultrasonic NDT Defect Recognition
COTANA, Franco;ROSSI, Federico;FILIPPONI, MIRKO
2003
Abstract
Non-Destructive Testings (NDT) are used to verify products quality without modifying their characteristics and performances. At present, automatic devices are available to individuate the position of a defect inside a solid structure. However, no technique is available to determine automatically the defect type. NDT on steel samples by means of ultrasounds is here analyzed. This technique is based on the reflection of an ultrasonic signal, due to presence of a possible defect. Two kinds of defects (non-metallic inclusions and porosities) have been investigated. The signal reflected by the defect has been studied by means of frequency analysis. It has been observed that some spectra characteristics are the same for the same kind of defect. This result is not available by using only a time domain analysis. A simple mathematical model has been found by correlating experimental results. Defects dimensions have been found out to be strictly correlated with spectra (- 6dB) frequency bandwidth. Correlation depends on the kind of the investigated defect.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
