Remote Field Eddy Current Method Research Articles

Study on Inspection for Small Diameter Tubes Using Pulsed Remote Field Eddy Current Method

Study on Inspection for Small Diameter Tubes Using Pulsed Remote Field Eddy Current Method

Detection of Fiber Fracture in Unidirectional CFRP by Remote Field Eddy-Current Testing

Detection of fiber fracture in unidirectional carbon-fiber-reinforced polymer (CFRP) using the conventional eddy-current method is difficult due to the low electrical conductivity of the material. This article explores the possibility of detecting fiber fracture using the remote field eddy-current method. A remote field eddy-current probe consisting of an excitation coil and a reception coil is designed and optimized. The experimental results show that the signal of scanning the probe over fiber fracture has a dual-valley characteristic and the distance between the two minima is identical to the distance between the coil axes. This characteristic of signal is analyzed by studying distributions of eddy current (EC) using a finite-element analysis. A comparison of the testing results of the remote field EC probe and the conventional EC probes demonstrates the superiority of the remote field EC method in detecting fiber fracture in unidirectional carbon-fiber-reinforced polymer.

Numerical simulation of non-destructive remote field eddy current testing of rolled metal tubes

The distinctive feature of remote field eddy current method is the ability of detecting defects on the external (with respect to the eddy current transducer) side of the tested object, which is impossible for the classical eddy current method due to the limited eddy current penetration depth. The basics of the method were considered, the distinctive features were presented, and the advantages and disadvantages of remote field eddy current testing of metals were pointed out. A numerical simulation with the subsequent analysis of the obtained results has been carried out, the probe design for remote field eddy current testing is given. The influence of various factors on the change in the added voltage of the eddy current probe in the presence of a defect in the external wall of the tube was considered. Expressions that determine the optimal ratio of the diameters of the probe and the tested product were obtained. The values of the test parameters and the limiting wall thickness of the tested ferromagnetic product were determined.

Performance Estimation of a Remote Field Eddy Current Method for the Inspection of Water Distribution Pipes

Remote Field Eddy Current (RFEC) technology allows the in situ inspection of metallic water distribution pipes. RFEC tools provide the location and magnitude of corrosion defects on the inspected pipes. The capacity of an RFEC tool to detect corrosion defects is evaluated in this paper by comparing its results with those obtained from the analysis of computed tomography (CT) scan images of the inspected pipes. Localization and characteristics of defects identified with the RFEC tool and from the CT scan images were compared for six cast iron pipes. An original method is proposed for the analysis of the CT scan images from which wall thickness losses were estimated by using the basic principle that the attenuation coefficient of X-rays in a homogenous material is a linear function of its density. The results show that the RFEC tool is able to localize most of the defects identified from the analysis of CT scan images. These findings reveal that the tested RFEC probe provided reliable information on the main corrosion defects, and thus on the general structural integrity of the inspected pipes.

Finite element modeling for simulating remote field flaw detection in aircraft frame

The remote field eddy current (RFEC) technique, conventionally used for inspecting ferromagnetic pipes has been adapted for the detection of defects that are located deep in thick aluminum plates. This paper presents three dimensional (3D) numerical modeling of the RFEC flaw detection in metallic plates. In the RFEC method the pickup coils are located far apart which leads to a large volume to be modeled. A method involving partitioning of the volume in the 3D finite element model for the RFEC detection of defects, is demonstrated.

Remote-field eddy current signal representation : Atherton, D.L.; Mackintosh, D.D.; Sullivan, S.P.; Dubois, J.M.S.; Schmidt, T.R. Materials Evaluation, Vol. 51, No. 7, pp. 782–789 (Jul. 1993)

While conventional reflected impedance eddy current testing (ET) techniques are limited by skin depth considerations to near surface defects, the RFEC (remote field eddy current) technique exploits skin effects. The RFEC method is a through-wall inspection technique. Only the field which has made a double transit of the pipe wall is detected. The skin depth equation can be used to predict the approximate effect of metal loss on the RFEC signal. Metal loss effectively reduces the shielding so that the attenuation and phase lag of the field is less. A method of analyzing RFEC defect signals is therefore to compare the signals with the phase and amplitude in uncorroded pipe. RFEC probes are used for inspecting ferromagnetic and nonferromagnetic tubulars for corrosion and, since eddy current detectors are generally well suited to crack detection, there is considerable interest in their potential to detect stress corrosion cracking in pipelines. Here the authors first of all summarize the impedance plane representation and scope monitor displays customarily used for conventional exploring coil ET probes in tubes. They then present the normalized voltage plane and monitor displays that are most appropriate for RFEC probes. They discuss the similarities and differences between the preferred monitormore » displays.« less

Remote-field eddy current signal analysis in small-bore ferromagnetic tubes : Mackintosh, D.D.; Atherton, D.L.; Sullivan, S.P. Materials Evaluation, Vol. 51, No. 4. pp. 492–495,500 (Apr. 1993)

A simple method for obtaining the depth of metal-loss defects in small bore ferromagnetic tubes by using the remote-field eddy current method is described. Research and analysis were carried out using a probe equipped with a solenoidal detector coil coaxial with the pipe, scanning uniform-depth metal-loss defects shorter than the overall probe length. On a voltage plane polar plot, which is similar to the voltage plane used in conventional eddy current analysis, the variations in signal amplitude and phase caused by metal loss trace out an elongated loop known as a defect-signal trace. The angle and length of the trace reveal the dimensions of the defect. The outside angle between the defect-signal trace and a line from the origin through the point representing no metal loss indicates the depth of metal loss. The length of the defect-signal trace indicates the cross-sectional area of metal loss. The experimental results are explained with reference to the skin-depth equation.