Influence of material type on attenuation in ultrasonic testing of welded joints

Abstract

U ovom radu provedeno je ultrazvučno ispitivanje zavarenih spojeva i etalonskih uzoraka izrađenih od konstrukcijskog čelika S355J2+N i nehrđajućeg čelika X10CrNi18-10. Svaki materijal imao je po jedan zavareni spoj i jedan etalon s provrtima promjera 3 mm na različitim dubinama. Cilj rada bio je usporediti prigušenje ultrazvučnih valova između različitih materijala i frekvencija. Ispitivanja su provedena konvencionalnom metodom odjeka pomoću kutnih sondi od 60°, pri frekvencijama od 2 MHz i 4 MHz. Kalibracija je izvedena DAC metodom, a mjerenja su temeljena na usporedbi reflektiranih signala s referentnom krivuljom osjetljivosti. Rezultati pokazuju da je prigušenje izraženije u nehrđajućem čeliku, osobito pri višoj frekvenciji, što je u skladu s njegovom mikrostrukturom i normom HRN EN ISO 22825. Konstrukcijski čelik pokazao je manji gubitak intenziteta, uz bolju čitljivost signala. Zaključno, rad potvrđuje značaj materijala i frekvencije u ultrazvučnom ispitivanju te važnost pravilne kalibracije sustava za pouzdanu detekciju unutarnjih nepravilnosti.This paper presents ultrasonic testing of welded joints and reference samples made from structural steel S355J2+N and stainless steel X10CrNi18-10. Each material included one welded joint and one reference sample with 3 mm side-drilled holes at different depths. The aim of the study was to compare ultrasonic wave attenuation between the materials at different frequencies. Testing was conducted using the conventional pulse-echo method with 60° angle probes, at frequencies of 2 MHz and 4 MHz. Calibration was performed using the DAC (Distance Amplitude Correction) method, and signal evaluation was based on comparison with the reference sensitivity curve. Results show significantly higher attenuation in stainless steel, especially at higher frequency, which aligns with its austenitic microstructure and the requirements of standard HRN EN ISO 22825. Structural steel showed lower signal loss and clearer reflections. In conclusion, the study confirms the influence of material type and probe frequency on ultrasonic testing, as well as the importance of proper system calibration to ensure reliable detection of internal discontinuities