摘要:

This paper proposes an RFECT probe equipped with a superconducting shield to shorten the distance between the exciter and the detector of the probe. Numerical simulations are carried out in axisymmetric configurations to clarify the effect of superconducting shield. The results of simulations imply that superconducting shields have advantages over a copper shield in its shield effect especially when the exciter is driven at a low frequency. An RFECT probe equipped with the superconducting shield is designed and fabricated with the aid of the numerical simulations. Experimental results confirm that the presence of superconductor shield shortens the distance between the exciter and the detector of the RFECT probe. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570164

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The authors have devised a new eddy current surface probe that generates minimal lift‐off noise and provides phase information on depth of flaws. The probe comprises a tangential exciting coil and two tangential detecting coils. The authors expect that the new probe will make eddy current testing more reliable in detecting flaws and more quantitative in evaluating depth of flaws than the conventional probes. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570165

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Magnetic sensors based on Giant Magnetoresistance (GMR) and Spin‐Dependent Tunneling (SDT) effects have high, frequency‐independent sensitivity. The small size and low power consumption of these sensors allow them to be used in multiple‐sensor arrays facilitating rapid scanning of an area in a single pass rather than raster scanning. This paper discusses the use of GMR and SDT sensors in NDE testing of surface cracks and features, deep cracks, and hole‐edge cracks as well as progress in X‐Y GMR sensors and multiple‐sensor arrays. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570166

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

In this paper we present theoretical analysis which gives the possibility to determine optimum excitation frequencies in eddy current examination of thick aluminum plates. A computer controlled non‐destructive testing system and a probe with a magnetoresistive sensor were utilized in laboratory tests. Experiments with specimens containing hidden cracks were carried out for a wide spectrum of frequencies. The optimum operating frequencies achieved from the experiments are in a very good agreement with those obtained by using theoretical analysis. Application of the optimum frequencies makes it possible to detect shallow cracks located on the reverse side of the specimens. Detection of a 15 &percent; crack in a 10 mm thick plate made of aluminum and a 20 &percent; crack in a 20 mm thick plate has been confirmed. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570167

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The model‐based inversion tools for eddy current signals have been developed by the novel combination of neural networks and finite element modeling for quantitative flaw characterization in steam generator tubes. In the present work, interpretation of experimental eddy current signals was carried out in order to validate the developed inversion tools. A database was constructed using the synthetic flaw signals generated by the finite element modeling. The hybrid neural networks of a PNN classifier and BPNN size estimators were trained using the synthetic signals. Experimental eddy current signals were obtained from axisymmetric artificial flaws. Interpretations of flaws were carried out by feeding experimental signals into the neural networks. The results of interpretations were excellent, so that the developed inversion tools would be applicable to the interpretation of experimental eddy current signals. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570168

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Several approaches to using combined near‐field microwave NDT techniques, utilizing open‐ended rectangular waveguides, and embedded modulated scatterer technique (MST) for the determination of the dielectric properties of a material have been investigated in the past. A technique currently under investigation involves using the ratio of dynamic forward‐ and reverse‐biased reflection coefficients, measured at the aperture of the waveguide. One important aspect of this method is that the ratio of reflection coefficients is not a function of the relative location or polarization of MST probe to the waveguide. Formulation of the ratio of dynamic reflection coefficients is presented, as well as preliminary measurements showing the coherent ratio of reflection coefficients to be relatively constant as a function of location in free‐space. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570169

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We report an imaging technique for various samples using a near‐field scanning millimeter‐wave microscope (NSMM) by using a standard tunable rectangular waveguide at operation frequencyf= 60GHz. By monitoring the change ofQ‐factor in the near field zone as the probe scanned over the object, we obtain quantitative images of the sample. By proper tuning process and using proper probe‐tips, we could improve sensitivity and a spatial resolution to better than 500 nm for the patterned YBa2Cu3Oythin films on MgO substrates. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570170

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We describe a near‐field scanning microwave microscope which uses a high‐quality dielectric resonator with a tunable screw. The operating frequency isf= 4.5 GHz. The probe tip is mounted in a cylindrical resonant cavity coupled to a dielectric resonator. By tuning the tunable screw coming through the top cover, we could improve sensitivity, signal‐to‐noise ratio, and spatial resolution to better than 1.5 &mgr;m. To demonstrate the ability of local microwave characterization, the surface resistance of metallic thin films has been mapped. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570171

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Detection of corrosion precursor pitting on metallic surfaces under various coatings and on bare metal is of keen interest in evaluation of aircraft fuselage. Near‐field microwave nondestructive testing methods, utilizing open‐ended rectangular waveguides and coaxial probes, have been used extensively for detection of surface flaws in metals, both on bare metal and under a dielectric coating. This paper presents the preliminary results of using microwave techniques to detect corrosion precursor pitting under paint and primer, applique and on bare metal. Machined pits of 500 &mgr;m diameter were detected using open‐ended rectangular waveguides at V‐Band under paint and primer and applique, and on bare metal. Using coaxial probes, machined pits with diameters down to 150 &mgr;m on bare metal were also detected. Relative pit size and density were shown on a corrosion‐pitted sample using open‐ended rectangular waveguides at frequencies of 35 GHz to 70 GHz. The use of Boeing’s MAUS™ scanning systems provided improved results by alleviating standoff variation and scanning artifact. Typical results of this investigation are also presented. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570172

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Reinforced concrete structures provide a highly alkaline and protective environment for steel bar reinforcements. The protective environment is destroyed upon the introduction of chloride ions, allowing for corrosion if moisture and oxygen are present. Microwave nondestructive testing is one method to detect chloride in cement‐based materials. A comprehensive understanding of how chlorides are deposited in mortar that is exposed to cyclical salt water soaking and oven drying is desired. Modeling is a necessary component of this process. This paper presents the modeling process using mixing models and possible salt distributions in conjunction with a multi‐layer code that provides simulated results. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570173

出版商:AIP    

年代:1903

数据来源: AIP