The topic of this master's thesis is the study of the possibility of monitoring the structural integrity of adhesively bonded joints. Adhesive joints have become popular in structural applications due to their characteristics: possibility of lightweight design, ability to join dissimilar materials, avoidance of stress concentrations and a uniform load distribution. The joints were manufactured using two adhesives: 3M Scotch-Weld 9323 and 3M Scotch-Weld 7260. The study of adhesive joints was performed using Double Cantilever Beam (DCB) specimens subjected to mode I static loading. Digital Image Correlation (DIC) and Acoustic Emission (AE) were used to study the crack propagation in DCB specimens. Acoustic Emission (AE) was chosen because of its property to be able to acquire the signal arriving from a damage source located within the joint and by means of different localization methods nd the location of the damage. A preliminary study on the AE parameters was performed to understand the influence of burst signals on those parameters. Pattern recognition algorithms such as the Self-Organizing Map (SOM) was used to divide the meaningful AE data from environmental noise. Such picking strategies were considered: Akaike Information Criterion (AIC), Baer and Kradolfer picker, Threshold adapted to maximum amplitude signal. The most suitable was found to be the AIC picker. Digital Image Correlation (DIC) was used to compare the localization data emerging from the AE sources. The results showed that acoustic emission is able to identify and locate the onset of plastic deformation, which opens new possibilities in terms of fi eld measurements.
L'argomento trattato in questa tesi di laurea magistrale è lo studio della possibilità di monitoraggio dell'integrità strutturale dei giunti adesivi. I giunti adesivi sono diventati popolari nelle applicazioni strutturali grazie alle loro caratteristiche: possibilità di design leggero, capacità di unire materiali dissimili, evitare l'effetto intaglio e una distribuzione uniforme del carico. I giunti adesivi sono stati realizzati utilizzando due adesivi: 3M Scotch-Weld 9323 e 3M Scotch-Weld 7260. Lo studio dei giunti è stato eseguito utilizzando provini di doppia trave a sbalzo (DCB) sottoposti a carico statico di modalità I. Digital Image Correlation (DIC) e Emissione acustica (AE) sono stati utilizzati per studiare la propagazione delle cricche nei provini DCB. L'Emissione Acustica (AE) è stata scelta per la sua proprietà di poter acquisire il segnale proveniente da una sorgente di danno localizzata all'interno del giunto e tramite opportuni metodi di localizzazione individuare la posizione del danneggiamento. E stato eseguito uno studio preliminare sui parametri AE per comprendere l'influenza dei segnali burst su tali parametri. Algoritmi di pattern recognition come la Self-Organizing Map (SOM) sono stati utilizzati per dividere i dati dell'AE signi cativi dal rumore ambientale. Sono state considerate tali strategie di prelievo: Akaike Information Criterion (AIC), Baer e Kradolfer picker, Threshold adattato al segnale di massima ampiezza. Il più adatto è risultato essere il AIC picker. Digital Image Correlation (DIC) è stata utilizzata per confrontare i dati di localizzazione emersi dalle fonti di AE. I risultati hanno mostrato che l'emissione acustica è in grado di identi care e localizzare l'inizio della deformazione plastica, aprendo nuove possibilità in termini di misurazioni sul campo.
An acoustic emission approach to monitor crack propagation in adhesive joints under mode I
Drobiazko, Mykola
2020/2021
Abstract
The topic of this master's thesis is the study of the possibility of monitoring the structural integrity of adhesively bonded joints. Adhesive joints have become popular in structural applications due to their characteristics: possibility of lightweight design, ability to join dissimilar materials, avoidance of stress concentrations and a uniform load distribution. The joints were manufactured using two adhesives: 3M Scotch-Weld 9323 and 3M Scotch-Weld 7260. The study of adhesive joints was performed using Double Cantilever Beam (DCB) specimens subjected to mode I static loading. Digital Image Correlation (DIC) and Acoustic Emission (AE) were used to study the crack propagation in DCB specimens. Acoustic Emission (AE) was chosen because of its property to be able to acquire the signal arriving from a damage source located within the joint and by means of different localization methods nd the location of the damage. A preliminary study on the AE parameters was performed to understand the influence of burst signals on those parameters. Pattern recognition algorithms such as the Self-Organizing Map (SOM) was used to divide the meaningful AE data from environmental noise. Such picking strategies were considered: Akaike Information Criterion (AIC), Baer and Kradolfer picker, Threshold adapted to maximum amplitude signal. The most suitable was found to be the AIC picker. Digital Image Correlation (DIC) was used to compare the localization data emerging from the AE sources. The results showed that acoustic emission is able to identify and locate the onset of plastic deformation, which opens new possibilities in terms of fi eld measurements.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/177412