Pulsed Eddy-Current Measurements of Corrosion and Cracking in Aging Aircraft

1997 ◽  
Vol 503 ◽  
Author(s):  
J. C. Moulder ◽  
J. A. Bieber
Keyword(s):  
Eddy Current ◽  
Current System ◽  
Fatigue Cracks ◽  
Single Frequency ◽  
Pulsed Eddy Current ◽  
Wide Range ◽  
Lift Off ◽  
Hidden Corrosion ◽  
Time Gating

ABSTRACTPulsed, or transient eddy-current methods are an effective tool for quantitative characterization of hidden corrosion and cracking in multi-layer aircraft structures. Eddy currents are the method of choice for this task, since they penetrate multiple layers of metal, whether or not the layers are mechanically bonded. The pulsed eddy-current technique is an important advance over conventional eddy-current methods because it rapidly acquires data over a wide range of frequencies, thereby providing more information than a conventional, single-frequency eddy-current instrument. We have combined a pulsed eddy-current instrument with a portable two-axis scanner to produce an instrument capable of rapidly scanning aircraft lap splices in situ, producing pseudo-color images that reveal hidden corrosion or cracking. A unique feature of time-domain eddy-current data is the ability to selectively filter clutter from the image by time-gating the pulsed signal. Time-gating permits the user to select the inspection depth, thereby eliminating interference from upper layers, air gaps, lift-off variation and fasteners. By using a theoretical model of the pulsed eddy-current system, it is possible to interpret the data quantitatively, yielding quantitative maps of corrosion damage. Some of the same advantages of the pulsed eddycurrent technique apply to the characterization of hidden fatigue cracks as well, although the tieory for crack signals is less advanced.

UTILIZING ULTRASONIC AND PULSED-EDDY CURRENT TECHNOLOGIES TO MAP THE LOCATION OF FIBER-OPTIC CABLE AND CLAMPS: A CASE STUDY

2021 ◽  
Author(s):  
Roddy Hebert ◽  
◽  
Rojelio Medina ◽  
JC Pinkett ◽  
Tyler Costa ◽  
...  
Keyword(s):  
Eddy Current ◽  
Fiber Optic ◽  
Current System ◽  
Value Added ◽  
Fiber Optic Cable ◽  
Ultrasonic Scanning ◽  
Service Companies ◽  
Pulsed Eddy Current ◽  
Wide Range ◽  
Great Insight

In an ongoing attempt to learn more about subsurface conditions before and during production, service companies and operators have explored a wide range of technologies. One technology, that allows for transmission of subsurface data back to the surface, is the installment of fiber optic cable behind casing. Fiber optic cable not only provides subsurface data conditions affecting production, but it serves as a highway for data transmission in seismic surveys, as well as, monitoring production information itself along the entire length of the cable. We will expand on methods used to preserve this installment of the fiber optic cable by identifying its location behind casing. Circumferential ultrasonic scanning techniques have been used for many years to inspect the casing itself, and cement behind the first string of casing. These techniques offer a better inspection of channeling, or partial vertical void in cement behind first string of casing, than just your standard radial cement bond tool. Cement and Casing Inspection have been useful services of the ultrasonic scanning services, but it isn’t without limitations, whereas this scanning tool has a shallow depth of investigation. Traditionally, standard cement bond logs are used in conjunction with the circumferential ultrasonic scanning services to examine the bond index, and to offer some additional understanding of the cement bond to casing, as well as cement to formation bond. In that shallow ultrasonic scan, is where this publication will demonstrate the value added of locating the fiber optic cable, but it is not without some uncertainty. To reduce some of that uncertainty, a pulsed-eddy current system, which uses an arm-mounted pad sensor that contacts the inside of the first casing string, utilizes pulsed-eddy current technology to accurately locate the position of the fiber optic cable mounting clamps. Detecting the location of the clamps, offers great insight into oriented perforation, but as this publication will demonstrate, the fiber optic cable can meander in between those clamps. The circumferential ultrasonic scanning service offers visibility of the meandering of that fiber optic cable, in between clamps, and when used in combination with the pulsed-eddy current system, this creates an integrated service that reduces the probability of perforating the installment of the fiber optic cable. Purpose of this paper, will be, to demonstrate the use of the impedance data, gained from the circumferential ultrasonic scanning tool, in combination with the fiber optic clamp location from the pulsed-eddy current tool, to locate the fiber optic flatpack between clamp locations. However, there are limitations in the location of the fiber flatpack, as in, gaps between flatpack and casing, and/or lack of cement coverage. The final product will include the depth location of clamps, station degrees of fiber loop, degrees of fiber flatpack location, and level of confidence by interval shading. This information will give customers greater confidence in the execution of oriented perforation procedures, without damaging fiber optic cable flatpack.

scholarly journals The Effects of Lift-Off from Wall Thinning Signal in Pulsed Eddy Current Testing

2012 ◽  
Vol 17 (4) ◽  
pp. 298-301 ◽  
Author(s):  
Duck-Gun Park ◽  
C.S. Angani ◽  
M.B. Kishore ◽  
C.G. Kim ◽  
D.H. Lee
Keyword(s):  
Eddy Current ◽  
Eddy Current Testing ◽  
Current Testing ◽  
Pulsed Eddy Current ◽  
Wall Thinning ◽  
Lift Off

An approach to reduce lift-off noise in pulsed eddy current nondestructive technology

2014 ◽  
Vol 63 ◽  
pp. 1-6 ◽  
Author(s):  
Yating Yu ◽  
Yue Yan ◽  
Fei Wang ◽  
GuiYun Tian ◽  
Dejun Zhang
Keyword(s):  
Eddy Current ◽  
Pulsed Eddy Current ◽  
Lift Off

scholarly journals Lift-off Invariant Inductance of Steels in Multi-Frequency Eddy-Current Testing

2021 ◽  
Author(s):  
Mingyang Lu ◽  
Xiaobai Meng ◽  
Ruochen Huang ◽  
Liming Chen ◽  
Anthony Peyton ◽  
...  
Keyword(s):  
Eddy Current ◽  
High Accuracy ◽  
Eddy Current Testing ◽  
Current Testing ◽  
Pulsed Eddy Current ◽  
Working Frequency ◽  
Lift Off ◽  
Ferromagnetic Steels ◽  
Point Of Intersection ◽  
Steel Properties

Eddy current testing can be used to interrogate steels but it is hampered by the lift-off distance of the sensor. Previously, the lift-off point of intersection (LOI) feature has been found for the pulsed eddy current (PEC) testing. In this paper, a lift-off invariant inductance (LII) feature is proposed for the multi-frequency eddy current (MEC) testing, which merely targets the ferromagnetic steels. That is, at a certain working frequency, the measured inductance signal is found nearly immune to the lift-off distance of the sensor. Such working frequency and inductance are termed as the lift-off invariant frequency (LIF) and LII. Through simulations and experimental measurements of different steels under the multi-frequency manner, the LII has been verified to be merely related to the sensor parameters and independent of different steels. By referring to the LIF of the test piece and using an iterative inverse solver, one of the steel properties (either the electrical conductivity or magnetic permeability) can be reconstructed with a high accuracy.

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