Process for detecting the position of defects in metal bars

A process for detecting the presence and position of defects in metal bars, comprising:

• detecting the velocity v of longitudinal sound propagation in a metal bar having the same structural composition as the one under examination, by reference to stored data or by striking with a percussion device a metal bar of known length L at one end, detecting with a piezoelectric sensor the fundamental frequency f and the harmonic frequencies and calculate, with a calculating device, the velocity v from the formula f=v/2L;
• detecting the Fourier spectrum of an intact, defect-free metal bar having the same structural composition and the same length as the metal bar under examination, by reference to stored data or by analyzing the fundamental frequency f and the harmonic frequencies by a spectrum analyser, electrically coupled to said piezoelectric sensor;
• acquiring the Fourier spectrum of the metal bar under examination, by striking with the percussion device the metal bar of know length L at one end, detecting with the piezoelectric sensor the fundament frequency f and the harmonic frequencies, and analysing the fundamental frequency f and the harmonic frequencies by the spectrum analyser, electrically coupled to said piezoelectric sensor;
• comparing by the spectrum analyser the two Fourier spectrums obtained and identifying the presence of any extra spectral lines present and due to the presence of defects in the metal bar under examination;
• and
• if said extra spectral lines are present:
• identifying the fundamental frequency f of said extra spectral lines by the spectrum analyser;
• applying with the calculating device the formula f=v/2x to the extra spectral lines present in the Fourier spectrum of the metal bar under examination in order to obtain a distance x of said defects from one end of the bar under examination, the velocity v of sound propagation and the fundamental frequency f being known.