Eddy current meaning,ford kuga lleva cadena o correa de distribucion nueva,what to put in a diaper bag first aid kit 7dtd - You Shoud Know

admin | Category: What Cause Ed | 03.04.2014
The basic principle behind standard EC testing involves placing a cylindrical coil, which is carrying an alternating current, close to the test piece.
Variations in the electrical conductivity or magnetic permeability of the test object or the presence of flaws will change the flow patterns of the eddy currents and there will be a corresponding change in the phase and amplitude of the measured current. EC testing can be used to inspect physically complex shapes and to detect small cracks on or near the surface of a test piece. The eddy current method is based on the principle of generating circular electrical currents (eddy currents) in a conductive material.
The eddy currents will always go the easiest way, and if cracks exist in the material, the current will go around the crack. The eddy currents are flowing beneath the surface of the material with the highest density close to the surface. Eddy current array (ECA) is a nondestructive testing technology that provides the ability to electronically drive multiple eddy current coils, which are placed side by side in the same probe assembly. Complex shapes can be inspected using probes customized to the profile of the part being inspected.
Over the years, probe technology and data processing have advanced to the point where eddy current testing is recognized as being fast, simple, and accurate.
The phenomenon of eddy currents was discovered by French physicist Léon Foucault in 1851, and for this reason eddy currents are sometimes called Foucault currents.
Foucault built a device that used a copper disk moving in a strong magnetic field to show that eddy currents (magnetic fields) are generated when a material moves within an applied magnetic field. Eddy current testing began largely as a result of the English scientist Michael Faraday's discovery of electromagnetic induction in 1831. In 1879, another breakthrough was made when another English scientist, David Hughes, demonstrated how the properties of a coil change when placed in contact with metals of different conductivity and permeability. Beginning in 1933, in Germany, while working for the Kaiser-Wilhelm-Institute, Professor Friedrich Förster adapted eddy current technology to industrial use, developing instruments for measuring conductivity and for sorting mixed-up ferrous components. EC-Works originates from the oldest branch roots in Germany and is specialised in the NDT-services business. Various materials could be checked, like carbon steel, stainless steel, duplex, alloy or other conductive materials. Compared to single-channel eddy current technology, eddy current array technology provides the following benefits: Drastically reduces inspection time. Eddy current array and conventional eddy current technology share the same basic principle. Eddy current array (ECA) technology provides the ability to electronically drive multiple eddy current coils placed side by side in the same probe assembly.
Most conventional eddy current flaw detection techniques can be reproduced with an ECA inspection.


The OmniScan™ ECA test configuration supports 32 sensor coils (up to 64 with an external multiplexer) working in bridge or transmit-receive mode.
The technology can be used to detect flaws in conducting materials or to measure the distance between a sensor and a conducting material. The current in the coil generates a changing magnetic field, which produces eddy currents in the test piece.
This is achieved by the use of a coil connected to an alternating current generator driving an alternating magnetic field (primary field). This change of eddy current flow also can be detected by monitoring the impedance of the coil and is mainly used for detection of cracks. The depth of penetration of the eddy currents depends on the conductivity and permeability of the material and the frequency of the alternating field. Each individual eddy current coil in the probe produces a signal relative to the phase and amplitude of the structure below it. Eddy currents are fields of alternating magnetic current that are created when an alternating electric current is passed through one or more coils in a probe assembly. The technology is now widely used in the aerospace, automotive, petrochemical, and power generation industries for the detection of surface or near-surface defects in materials such as aluminum, stainless steel, copper, titanium, brass, Inconel®, and even carbon steel (surface defects only). Faraday discovered that when a magnetic field passes through a conductor (a material in which electrons move easily)-or when a conductor passes through a magnetic field-an electric current will flow through the conductor if there is a closed path through which the current can circulate.
However, it was not until the Second World War that these developments in the transmitting and receiving of electromagnetic waves were put to practical use for materials testing. In 1948, Förster founded his own company in Reutlingen, a business based on eddy current testing that continues to this day. EC-Works, the company's name tells it quite shortly, operates eddy current inspections and develops new technologies and applications. The two coils (red) were pulled over the defect and the typical signal appeared on the screen.
Special probes allow to detect inside cracks from outside, depending on the material and wall thickness.
Data acquisition is performed by multiplexing the eddy current coils in a special pattern to avoid mutual inductance between the individual coils. With the benefits of single-pass coverage, and enhanced imaging capabilities, ECA technology provides a remarkably powerful tool and significant time savings during inspections. The operating frequency ranges from 20 Hz to 6 MHz with the option of using multiple frequencies in the same acquisition. The measurement does not require the tested object to be in direct contact with the test equipment. Variations in the phase and magnitude of these eddy currents are monitored using a second coil (search coil) or by measuring changes to the current flowing in the primary coil (excitation coil).


The technique is also used for measuring electrical conductivity and the thickness of coatings. At high frequencies the eddy currents concentrate at the surface, while with lower frequencies deeper regions within the material are penetrated. This data is referenced to an encoded position and time and represented graphically as a C-scan image. When the probe is linked with the part under inspection, the alternating magnetic field induces eddy currents in the test part.
The expert knowledge and practical experience of more than 35 years eddy-current services enables them to their unique position in the international NDT-market.
If a defect appears in the effective area, the eddy current have to take a different way, this changes the impedance of the coil and the operator see the changes on his screen (Z1-Z2). When the coil is placed over a conductive part, opposed alternating currents (eddy currents, in red) are generated. A coil in air is not influenced by eddy currents, but moving the coil towards an electrical conductive sample results in a signal, which can be used for distance measurement, e.g.
Most conventional eddy current flaw detection techniques can be reproduced with ECA inspections; however, the remarkable advantages of ECA technology allow improved inspection capabilities and significant time savings. Discontinuities or property variations in the test part change the flow of the eddy current and are detected by the probe in order to make material thickness measurements or to detect defects such as cracks and corrosion.
Many advances were made throughout the 1950s and 1960s, especially in the aircraft and nuclear industries.
There have been many recent developments in eddy current testing, leading to improved performance and the development of new applications. It is also applicable to detect subsurface corrosion and to determine the thickness of conductive sheets.This effect is used mainly for non-ferromagnetic material. Eddy current testing is now a widely used and well-understood inspection technique for flaw detection as well as for thickness and conductivity measurements. Due to the high permeability of ferromagnetic material the standard eddy current method here is limited to the region close to the surface.
There exist extended methods to inspect e.g the subsurface of thick-walled  ferromagnetic pipes or plates.



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