Metrological Aspects of the Time of Flight Diffraction Technique (ToFD) Used in Nondestructive Testing (NDT) by Ultrasound

Abstract

The Non-Destructive Testing (NDT) are widely used in industry. Among the main NDT techniques, the most used are based on the use of ultrasound. One of these is the Time of Flight Diffraction Technique (ToFD). The ToFD is based on the use of two angle transducers placed in parallel on the same surface at a fixed distance from one another, known as Probe Center Separation (PCS). The PCS seeks the focus of sonic waves in a part of the inspected point on which to characterize, however, the beam is not totally reaches the workpiece to be inspected. Therefore, it is believed that with the variation of PCS, the piece may be completely inspected. Therefore, it was tested whether, by varying the PCS is possible to minimize the dead zone, increasing the reliability of inspection. It was concluded that the variation of PCS in ToFD technique has direct influence in the identification of discontinuities near the surface or near the bottom of the piece. It was evident that for surface discontinuities the lowest PCS is more effective, whereas for discontinuities near the bottom, larger PCS are most efficient. Metrology is the base of this research of technological development.

Key-words
Non-destructive testing; Ultrasound; ToFD; Metrology; Probe Center Separation (PCS)