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[en] This training and reference manual was assembled to provide those involved in eddy current testing with both the fundamental principles of the technique as well as the knowledge to deal with often complicated test results. A non-rigorous approach is used to simplify complex physical phenomena. Emphasis is placed on proper choice of test frequency and signal interpretation. Defect detection and diagnosis receive particular attention. Design and construction of probes are covered extensively since probes play a key role in eddy current testing. The advantages and limitations of various probe types are discussed. Electromagnetic theory, instrumentation, test methods and signal analysis are covered. Simplified derivations of probe response to test parameters are presented to develop a basic understanding of eddy current behaviour. Eddy current signals are presented on impedance plane diagrams throughout the manual since this is the most common display on modern, general purpose instruments. The use of Σphase lagΣ in signal analysis is covered in detail. To supplement theory, practical examples are presented to develop proficiency in performing inspections, and to illustrate how basic principles are applied to diagnose real signals
[en] Highlights: • Ferrite microhardness of thermally aged Z3CN20.09M at 380 °C increases with aging time. • Charpy impact energy decreases and tends to saturate after 9000 h. • Eddy current testing was used to evaluate the embrittlement of thermally aged Z3CN20.09M. • Correlations between the eddy current amplitude and Charpy impact energy and ferrite microhardness were obtained.
[en] It is often necessary to define test conditions in eddy current testing, in consequence rules and laws allowing a rapid choice of these conditions are welcome. The similarity law, given by Forster, using the reduced frequency f/fg, allows extrapolation of results from an object to one another, if these two objects are similar (i.e. all their dimensions are proportional). In a particular case, often met, a law going further is given to describe, in a sole way, eddy current behaviour using the reduced frequency in all thin tubes (internal to external diameter ratio between 0.85 to 1). For instance working at f/fe=2 defines the same verification leading to identical results, whatever the nature, the diameter or the thickness may be, if the tubes are thin. A diagram is given and a slide-rule, based on this principle, has been realized
[fr]Le praticien des controles par courants de Foucault est souvent amene a definir les conditions de l'examen qu'il effectue: il est donc avide de regles et de lois lui permettant rapidement le choix de ces conditions. La loi de similitude enoncee par Forster permet, par utilisation de la frequence reduite f/fg, d'extrapoler les resultats d'un objet a un autre, a condition que ces deux objects soient semblables (toutes leurs cotes proportionnelles). Dans un cas particulier tres courant, on met en evidence une loi allant beaucoup plus loin, puisque l'utilisation de la variable reduite f/fe decrit de maniere unique le comportement des courants de Foucault dans tous les tubes minces (rapport des diametres interne et externe variant de 0,85 a 1): travailler a f/fe=2. par exemple, definit donc un meme controle conduisant a des resultats identiques, quels que soient la nature, le diametre ou l'epaisseur des tubes, a condition que ceux-ci restent minces. On donne une abaque et une regle a calcul a ete construite sur ce principe
[en] The authors propose a new eddy current probe inducing uniform eddy current in the test material. The features of the probe are self-differential, lift-off noise free, and self-nulling in principle. The experimental results have shown that the probe has a promising possibility of applying eddy current testing to weld zones.
[en] The progress of the ECT probe with micro magnetic sensor becomes possible to apply to various applications. The detection of micro metallic bead used for electric packaging has been reported in this paper. We proposed micro ECT probes with meander coil as exciter and spin-valve giant magneto-resistance (SV-GMR) as receiver. Micro metallic bead(solder ball) with the diameter of 0.25 to 0.76 mm is used as a measuring object. We discuss the detection and alignment of metallic bead by using ECT technique
[en] Full-text: Pulsed eddy current (PEC) is an advance Non-destructive testing that is widely used in multiple industries for surface and subsurface defect detection. Normally, the conventional features extractions are conducted based on time to peak and peak value response. However, signals extraction could be a confusing for a thin specimen because times to peak for both surface and subsurface defects are occurred at almost similar time. This paper introduced the application of confirmatory Factor Analysis for defect categorizing for stainless steel thin plate. Through this statistical method, two categories of defects namely surface and subsurface defects are clearly to be distinguished between one to another. (author)
[en] The eddy current probe was designed for the test of fin tubes that have uneven outer and inner surfaces to enhance the efficiency of heat emission. Because of the surface roughness of the fin tube, it needs much care to detect flaws in the tube employing eddy current test(ECT). We made ECT probes with different coil lengths and performed eddy current test using these probes for artificially flawed specimens. By the fast Fourier transform and digital filtering, signals from these probes were processed to characterize frequency spectra. From the analysis of eddy current signals and their frequency spectra, we concluded that, for the effective testing of the tubes with the fins of 1mm pitch, 4mm coil length gave the highest S/N ratio
[en] This study is based on the studying, designing and manufacturing of eddy current probes for industry applications. The main tasks of this study include: i) Describes the overview and classification of eddy current probes (which can be classified into three categories based on the mode of operation: absolute eddy current probe, differential eddy current probe and reflect eddy current probe); ii) Describes the three methods of probe designing and manufacturing (including experimental, analytical and numerical designs); iii) Describes the designing and manufacturing of eddy current probes for industry applications, which based on experimental and analytical methods. Based on this study, we have successfully manufactured some current probes (including absolute eddy current probe, differential eddy current probe and reflect eddy current probe) for surface and tube inspections. (author)
[en] In continuous steel billet casting, keeping the mold level steady is one of the most important technologies for maintaining steel quality. In this study, a eddy current level meter which measures the level of the continuous mold has been developed, based on the principle of electromagnetic induction. The measured error was minimized by the characterization of distance amplitude curve at 50 kHz, AC 12 Vpp. The use of the eddy current sensor with the correction of a log-amplifier showed that the resolution of the measurement was within 0.5mm on the period of level 0-100 mm and 1.0 mm on the period of level 100-250 mm. The eddy current level meter with associated the electronic device was installed in a continuous caster 1 M/C, Gwangyang, POSCO works and measured the level of the continuous mold.
[en] Remote field eddy current testing (RFECT) with through-wall transmission characteristic is being applied to pipes ranging from small tubes of heat exchanger to natural gas supply pipelines. Cast iron pipes with nominal diameter of 100mm are used primarily as the waterline pipes. The leakage of water occurs due to defects in the pipes caused by vibration of automobiles and corrosion. But, the use of direct inspection methods such as insertion of inspection equipment inside the pipelines has been limited due to its lack of economical efficiency. Economical development of inspection equipment is possible since RFECT method can be easily employed for system integration and quantitative evaluation of both inside and outside defects. In this study, the development of underground pipeline inspection system was tarried out by using RFECT method in consideration of the characteristics of waterline network. This paper specifically describes the design and production of RFECT pipeline inspection pig using centralizer mechanism, development of remote field eddy current signal acquisition and processing software, and review of RFECT system operation procedures