The non-destructive testing method based on acoustic emission is very well established and allows the detection and the location of defects on various structures including pressure tanks. Acoustic waves can be generated at discontinuities as cracks and, in some situation, at stress raisers due to notches, especially if plasticity occurs. The experimental activity we present aims at tuning the interpretation of AE signals so that a proper classification can be done distinguishing whether the acoustic event is due to a plastic front or an active crack. We loaded in three point bending flat rectangular specimens of steel sheet extracted from the tank manufacturing process just before the calendering stage. Experiments were conducted monitoring the load, the displacement and the AE signal for a flat specimen and for a notched one, loaded cyclically. The load is kept always positive so that at the bottom side (where the notch is located) the stress is always in traction. According to this experiment set-up we observe that for the un-notched specimen no relevant AE signal are recorded. For the notched one AE signals at the beginning of the experiment become relevant only in the case of a load high enough to induce plastic strains at the notch root. We have furthermore observed that during cyclic loads AE activities remain self-similar and related to the plasticity advance as far as no damage occurs. After some plastic cycles, a consistent evolution (with a substantial increment in the number of hits) is registered and becomes more and more intense; this observation matches very well with a crack nucleation and evolution to a fully developed crack. According to what we have observed, it seems that AE signal allows to detect and monitor not only existing crack and their evolution, but also high plastic strain at stress raiser and the onset of crack nucleation.
Biancolini, M.e., Brutti, C., Chiappa, A., & Salvini, P. (2019). Artificial pre-cracking of tanks test samples for AE detection tuning. Paper presented at 1st EPERC International Conference.
|Autori:||Biancolini, Me; Brutti, C; Chiappa, A; Salvini, P|
|Titolo:||Artificial pre-cracking of tanks test samples for AE detection tuning|
|Nome del convegno:||1st EPERC International Conference|
|Data di pubblicazione:||apr-2019|
|Settore Scientifico Disciplinare:||Settore ING-IND/14 - Progettazione Meccanica e Costruzione di Macchine|
|Tipologia:||Intervento a convegno|
|Citazione:||Biancolini, M.e., Brutti, C., Chiappa, A., & Salvini, P. (2019). Artificial pre-cracking of tanks test samples for AE detection tuning. Paper presented at 1st EPERC International Conference.|
|Appare nelle tipologie:||02 - Intervento a convegno|