The eddy current method is based on the principle of generating circular electrical currents eddy currents in a conductive material. The test equipment consists of a generator ac power supply, a test coil and recording equipment, e. Eddy current testing can be used for a wide range of applications, and is often applied for surface crack detection and material sorting. Conformable eddy current sensor arrays permit examination of planar and nonplanar materials but usually require suitable fixtures to hold the sensor array near the surface of the material of interest, such as a layer of foam behind. Understand the theory and principles upon which eddy current testing et examination is based.
Several other methods such as remote field testing rft, flux leakage and barkhausen noise also use this principle. Which of the following is not a probe configuration used in eddy current testing. Eddy current testing level 1 certified personnel shall neither be responsible for the choice of test method or technique to be used, nor for the interpretation of the test results. Available from the national technical information service. This paper includes an overview of the fundamentals and main variables of eddy current testing.
In fact, one of the major advantages of eddy current inspection is that probes can be custom designed for a wide variety of applications. This was supplied by a large fan and cowling which provided airflow over the engine at. Eddy current testing technology 1st edition be exceptional 9 7 8 0 9 9 1 7 0 9 5 2 6. A standardized procedure for eddycurrent testing of stainless steel, thinwalled nuclear fuel element cladding tubes p. Lecture notes 23 eddy currents in conductors conductors, by definition, contain free electrons i. We have the most extensive experience, and we develop the highest quality ect inspection products. Since eddy current power winds up as heat, the transformer will eventually get hot possibly so hot it could be destroyed, if it has not been designed properly. Eddy current testing is one of the most extensively used nondestructive techniques for inspecting electrically conductive materials at very high speeds that does not require any contact between the test piece and the sensor. Eddy current array eca eddy current testing ect internal rotary inspection system iris long range ut lrut guided wave. The tubes in this machine were tested for normal wear patterns using accepted test methods for eddy current inspections. These methods and a few others are briefly described below. This is often also referred to as electromagnetic braking. Assessment of eddy current testing for the detection of.
The following suggested repair actions are based on accepted industry standards. This image is produced not by light but by scanning it with an eddy current probe containing an sdt sensor. A brief description of ndt techniques page 8 in the direct method a high amperage current is passed through the subject and magnetic flux is generated at right angles to the current flow. Notice the spike in the eddy current signal, confirming that there is a defect in the component. Nondestructive testing ndt is a mechanism used by engineers to detect defects in materials and structures, either during manufacturing or while in service. Zetec is the industry leader for costeffective eddy current testing ect in complex applications. High product reliability and quality in metal processing are the main concerns throughout the volume. The possibility does exist that tubes could contain defects andor leaks which are not detectable, such as those at or near the tube end. An introduction to eddy current testing from the ndendt resource center. Buckley pdf, 429 kb eddy current testing at level 2, international atomic energy agency, vienna, 2011 pdf 5. This important and growing industry is involved in applying these. Introduction basic principles history of et present state of et. The current in the coil generates circulating eddy currents in the specimen close to the surface and these in turn affect the current in the coil by mutual induction.
The eddy current testing programmed instruction series is two volumes which provide the background material you will need before you perform actual eddy current testing. Objective liquid penetrant processes are nondestructive testing methods for detecting discontinuities that are open to surface. Elangovan we are pleased to bring out our fully revised new edition of non destructive testing of materials book for engineering and technology studies. Which of the following is not a mandatory component in a basic eddy current test apparatus. The discovery by oersted of the magnetic action of an. This is achieved by the use of a coil connected to an alternating current generator driving an alternating magnetic field primary field. Eddy current losses in transformer windings and circuit wiring. Figure 4 the saj eddy current dynamometer used for engine testing. Magnetic field induces currents eddy currents in test specimen. Nondestructive techniques based on eddy current testing mdpi. Non destructive testing eddy current testing, wirbelstrom.
In eddy current testing, a coil carrying an ac current is placed close to the specimen surface, or around the specimen. Astm e3052 standard practice for examination of carbon steel welds using eddy current array. Experience is based on the actual hours worked in the specific method. Typically, the methods used are ultrasonics, radiography, magnetic particle, eddy current, dye penetrant and visual methods. Eddy current testing permits crack detection in a large variety of conductive materials, either ferromagnetic or. Manual for the s yllabi contained in iaeat e cd o c628. The impedance change is also affected by excitation frequency effect of xl or 2. Eddy current technique is an important electromagnetic non. Furthermore, the relative severity of a discontinuity may be indicated, and a rejection level may be set with respect to the magnitude of. Eddy current inspection is one of several ndt methods that use the principal of electromagnetism as the basis for conducting examinations.
These high frequency effects are caused by the magnetic field resulting from current flow in transformer windings and circuit wiring. Eddy current testing hareesha n g, dept of aero engg, dsce 2 3. Phased array ultrasonic testing paut pulsed eddy current pec remote visual inspection rvi remotefield testing rft. Rao 9 et al investigated the basics of eddy current testing. In this study the amount of the pearlite content is analyzed using the eddy current testing response. Eddy current techniques in ndeeddy current techniques in nde lalita udpa nondestructive evaluation laboratory department of electrical and computer engineering miccg s euvesyhigan state university east lansing, mi 48824 wcndt p f w k h d b a il 15 2012wcndt preconference workshop. Note that cracks must interrupt the surface eddy current flow to be detected. Astm e2884 17 standard guide for eddy current testing of. They may be effectively used in the inspection of both ferrous and nonferrous metals and on nonporous, nonmetallic materials, such as ceramics, plastics and glass. Here a small surface probe is scanned over the part surface in an attempt to detect a crack. Introduction eddy current inspection is one of several methods that use the principal of electromagnetism as the basis for conducting examinations. Rao nondestructive evaluation division metallurgy and materials group indira gandhi center for atomic research kalpakkam 603 102, tn, india email.
Eddy current probes are available in a large variety of shapes and sizes. This is the basis of eddy current testing, by monitoring the voltage across the coil in such an arrangement we can detect changes in the material of interest. Eddy current techniques in ndeeddy current techniques in nde. Eddy current testing is an inspection method that can be used for a variety of purposes including the detection of cracks and corrosion, material and coating thickness measurement, material identification and, in certain materials, heat treatment condition. Inspecting turbine dovetails with eddy current array technology. Bhattacharya thinwalled nuclear fuel cladding tubes made of aisi 316 stainless steel have been examined by eddycurrent testing. Visual and optical testing vt visual inspection involves using an inspectors eyes to look for defects. Ndt methods may be divided into groups for the purposes of these notes. Eddy currents are fields of alternating magnetic current that are created when an alternatin. Successful completion of these two volumes is dependent on prior completion of 5330. Therefore the current flow should be in the same line as the suspected defect. This book covers the latest syllabus prescribed by anna university, chennai for mechanical, mechatronics, aeronautical, automobile students of all engineering.
Eddy current testing can be used on all electrically conducting materials with a reasonably smooth surface. High quality eddy current testing solutions for complete inspections. Training and experience hours required for certification. Eddy current probe configuration the main components of an eddy current probe for nondestructive testing are a pancaketype coil and a wheatstone bridge of gmr or sdt sensors see figure 1.
A standardized procedure for eddycurrent testing of. In this video i use lenz law to explain how eddy currents form when a piece of metal passes through a magnetic field. Principle ec testing works on the principles of electromagnetic induction. Nondestructive techniques based on eddy current testing. During power measurements it necessary to provide sufficient cooling air to the engine to avoid overheating. Eddy current testing eddy current testing is particularly well suited for detecting surface cracks but can also be used to make electrical conductivity and coating thickness measurements. Download non destructive testing of materials by dr. Eddy current ec testing is a no contact method for the inspection of metallic parts.
This paper is intended to provide insight into these phenomena so that improved high fre. Eddy current nde is commonly used in the inspection of conducting samples. In this technique, a coil also called probe or sensor is excited with sinusoidal alternating current frequency, f, 50 hz5 mhz, 100 ma. The physics properties of electricity current flow & ohms law induction & inductance. 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.
Eddy current testing technology eclipse scientific. Eddy current testing ect is one of the techniques employed in ndt 3, 4. Nondestructive testing eddy current basic principles. Robotizing eddy current array to find stresscorrosion cracks in stainless steel canisters. The process relies upon a material characteristic known as electromagnetic induction. Eddy current probes are classified by the configuration and mode of operation of the test coils. Nuclear regulatory commission office of nuclear regulatory research washington, dc 205550001. Assessment of eddy current testing for the detection of cracks in cast stainless steel reactor piping components pacific northwest national laboratory u. Falling under ect, pulsed eddy current pec utilizes magnetic field to be directed into a conductive tested sample for. Et flat surface inspection tube inspection metal sorting conductivity coating thickness crack detection principles of eddy current testing standard depth of penetration standard depth of penetration where the eddy current is 1e 37% of its surface value the standard depth of penetration in mm is given by the formula.
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