Eddy current generation enhancement using ferrite for electromagnetic acoustic transduction

Eddy currents are generated in an electrically conducting surface as a step in electromagnetic acoustic transduction (EAT). In eddy current testing, wire coils are often wound onto a ferrite core to increase the generated eddy current. With EAT, increased coil inductance is unacceptable as it leads to a reduction in the amplitude of a given frequency of eddy current from a limited voltage source, particularly where the current arises from capacitor discharge. The authors present a method for EAT where ferrite is used to increase the eddy current amplitude without significantly increasing coil inductance or changing the frequency content of the eddy current

Depth of penetration effects in eddy current testing

The simple depth of penetration equation used for most eddy current calculations does not take into account the effect of the size of the coil or the effect of flaw morphology. The work described in this paper describes use of the CIVA eddy current model to investigate this effect and some experimental investigations. Knowledge of this effect is important in examination of thin sections with eddy currents. Two examples of this are the small sections required to be inspected in laser metal deposition, and welds in thin sections joining dissimilar metals such as copper and aluminium for electrical connections

Handbooks describe eddy current techniques used in nondestructive testing of metal parts and components

Handbooks describe eddy current techniques used in nondestructive testing of metal parts and components

Система вихрострумової дефектоскопії

The eddy current nondestructive testing of metal products is widely used in various industries. There are eddy current control techniques takes a significant place in energy sector. Current work presents the eddy current flaw detection system. Implementation of this eddy current flaw detection system will solve a wide range of problems of eddy current flaw

Technique for temperature compensation of eddy-current proximity probes

Eddy-current proximity probes are used in turbomachinery evaluation testing and operation to measure distances, primarily vibration, deflection, or displacment of shafts, bearings and seals. Measurements of steady-state conditions made with standard eddy-current proximity probes are susceptible to error caused by temperature variations during normal operation of the component under investigation. Errors resulting from temperature effects for the specific probes used in this study were approximately 1.016 x 10 to the -3 mm/deg C over the temperature range of -252 to 100 C. This report examines temperature caused changes on the eddy-current proximity probe measurement system, establishes their origin, and discusses what may be done to minimize their effect on the output signal. In addition, recommendations are made for the installation and operation of the electronic components associated with an eddy-current proximity probe. Several techniques are described that provide active on-line error compensation for over 95 percent of the temperature effects

Minimizing the effect of probe-to-metal spacing in eddy current testing

"January 8, 1959."Two titles published in one volume. "Reduction of probe-spacing effect in pulsed eddy current testing" by Donald L. Waidelich and "Minimizing the effect of probe-to-metal spacing in eddy current testing" by C.J. Renken Jr. and D.L. Waidelich

Pulsed eddy current non-destructive testing

The article is devoted to the development of an experimental model of the information-diagnostic system of eddy current flaw detection and analysis of its work. A technique for processing experimental data and presenting the results obtained is considered. It is shown that the use of eddy current flaw detection with transducer pulsed excitation mode in combination with digital processing of information signals based on the discrete Hilbert transform can substantially supplement the known eddy current method of NDT by analyzing such signal parameters as the frequency of natural oscillations, peak amplitude value, signal decrement. The proposed technique for processing the signals of an eddy current transducer has been tested using the example of processing the eddy current flaw detection signals in problems of testing an aluminum plate with cracks of different depths

Study of eddy current probes

The recognition of materials properties still presents a number of problems for nondestructive testing in aerospace systems. This project attempts to utilize current capabilities in eddy current instrumentation, artificial intelligence, and robotics in order to provide insight into defining geometrical aspects of flaws in composite materials which are capable of being evaluated using eddy current inspection techniques

NDE: An effective approach to improved reliability and safety. A technology survey

Technical abstracts are presented for about 100 significant documents relating to nondestructive testing of aircraft structures or related structural testing and the reliability of the more commonly used evaluation methods. Particular attention is directed toward acoustic emission; liquid penetrant; magnetic particle; ultrasonics; eddy current; and radiography. The introduction of the report includes an overview of the state-of-the-art represented in the documents that have been abstracted

Eddy current testing of AGR fuel cladding

The scope of the presented study was to investigate feasibility of Eddy Current Testing (ECT) for detection in storage of inter-granular attack (IGA) cracking and general clad thinning of irradiated fuel cladding from Advanced Gas-cooled Reactors (AGR). The impact of the storage environment, particularly the effect of immersion in water compared to measurements in air, has also been investigated. A miniature EC probe was developed to induce eddy currents in a pin and to read out EC response. The transducer was robotically moved along the AGR pin and multi-frequency EC responses were acquired using a spectrum analyser. Main results of the experimental investigation are the following: even very small artificial defects such as short EDM notches of depth of 100μm produce distinguishable EC response; localised clad thinning of depth of 100μm and above produces considerable EC response levels; effect of water environment on the EC response is negligible; effect of anti-stacking grooves on the EC response is considerable