Non Destructive Surface and Sub-surface Material Analysis using Scanning SQUID Magnetic Microscope

Adamo, Maria (2008) Non Destructive Surface and Sub-surface Material Analysis using Scanning SQUID Magnetic Microscope. [Tesi di dottorato] (Inedito)

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Abstract

Non Destructive Testing (NDT) based on magnetic technique for the investigation of surface and sub-surface material properties is carried out using a room-temperature sample Scanning Magnetic Microscope. The performances of such instrument are well suited in the field of non destructive evaluation, thanks to the good combination of the spatial resolution and the magnetic field sensitivity of its own superconducting magnetic sensor. The aim of this work is to show the capability and the advantages of the NDT technique based on Superconducting Quantum Interference Device (SQUID) sensors. We start by describing our Scanning SQUID Microscope in terms of its performances, the different non destructive techniques we can apply to perform the measurements, and the efforts we have done to improve its capability to detect weak magnetic field variations. Two main applications are presented. On of this is based on the high magnetic field sensitivity of the SQUID sensor at low frequencies, and it consists to excite the sample with an alternating magnetic field (AC). This technique is applied to detect subsurface flaws in paramagnetic samples, for instance, in multilayer structures of aeronautical interest. The other field of application concerns the capability of the sensor to detect, with high spatial resolution, the direct magnetic field (DC) distribution on ferromagnetic samples, due to their residual magnetization. In this way, we can visualize magnetic domain structures of ferromagnetic particles. This capability is also exploited to evaluate the changing of magnetic field distribution in proximity of crack initialization on structural steels, subjected to fatigue cycles.

Tipologia di documento:Tesi di dottorato
Parole chiave:SQUID, Non Destructive Evalaution, Scaning SQUID Microscope
Settori scientifico-disciplinari MIUR:Area 02 Scienze fisiche > FIS/07 FISICA APPLICATA (A BENI CULTURALI, AMBIENTALI, BIOLOGIA E MEDICINA)
Area 02 Scienze fisiche > FIS/01 FISICA SPERIMENTALE
Coordinatori della Scuola di dottorato:
Coordinatore del Corso di dottoratoe-mail (se nota)
Abbate, Giancarloabbate.na.infn.it
Tutor della Scuola di dottorato:
Tutor del Corso di dottoratoe-mail (se nota)
Sarnelli, Ettore
Cristano, Roberto
Stato del full text:Accessibile
Data:29 Novembre 2008
Numero di pagine:167
Istituzione:Università degli Studi di Napoli "Federico II"
Dipartimento o Struttura:Scienze Fisiche
Tipo di tesi:Dottorato
Stato dell'Eprint:Inedito
Scuola di dottorato:Ingegneria Industriale
Denominazione del dottorato:Nuove Tecnologie per Materiali, Sensori ed Imaging
Ciclo di dottorato:XXI
Numero di sistema:3338
Depositato il:13 Novembre 2009 15:59
Ultima modifica:09 Giugno 2010 14:14

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