44934 Junger, M.; Brook, C. Beginner 's guide to principles, sensor selection and evaluation techniques for magnetic flux leakage testing British Journal of Nondestructive Testing, Vol. 32, No. 10, pp. 513- 515 (Oct. 1990)

This is the second part of a Beginner's Guide on electromagnetic techniques with particular emphasis on sensors and evaluation. This paper is concerned with magnetic flux leakage techniques. Principles of operation of the two major methods of flux leakage testing will be briefly described and as with Part 1 emphasis will be given to the practical selection of coil configuration in which there have been recent developments.

A.A/.72 Atherton, D.L. Developments in magnetic inspection techniques for pipelines CSNDT Journal, Vol. 11, No. 1, pp. 28-35, (Jan.-Feb. 1990)

Magnetic flux leakage inspection techniques are described in this paper as a means of nondestructively testing the vast lengths buried gas transmission pipelines in environmental and safety, reasons but also as a means of determining maximum operating pressure and throughput and stabilizing economic considerations. A circumferential array of magnetic flux leakage anomaly detectors is fitted in a pipeline device called a "pig" for in-service inspections, which responds to defects, such as corrosion, in the pipe wall. Stress is highlighted as a dominant parameter governing magnetic behaviour in the steel pipe walls.

43729 Atherton, D.L.; Jaadish, C.; Laursen, P.; Storm, V.; Ham, F.; Scharfenberger, B. Pipeline inspection tool speed alters MFL signals Oil and Gas Journal, Vol. 88, No. 5, pp. 84-86 (29 Jan. 1990)

Defects in oil and gas pipelines can be detected using magnetic flux leakage (MFL) signals while using in-line inspection tools. The velocity of the inspection tool is found to be related to defect - induced signals. Precise experimental measurement of magnetic leakage flux distributions were made with an MFL anomaly detector in place of the usual inspection tool. Initial results are presented from detailed maps of defect - induced MFL patterns made at different relative tool velocities for various defect penetrations.

43728 Hanasaki, K.; Tsukada, K.; Fufinaka, Y. Predictions of magnetostatic leakage fields a round P.W.S. ropes by 3-D dynamic relaxation method Nondestructive Testing and Evaluation for Manufacturing and Construction. Edited by H.L.M. dos Reis. pp. 381-392. Hemisphere Publishing Corporation, (1990). ISBN 0-89116-926-1

Parallel Wire Strand (P.W.S.) ropes are used as major elements in suspension roofings and suspension bridges. The authors are developing as new magnetic testing machine for P.W.S. ropes, which consists of a leakage flux detector assembly with Hall-effect sensors and two exciting solenoid coils set co-axially with the rope to be inspected. In this paper, the numerical modeling is described and the predictions by the code are compared with the results obtained from the experiments of inspecting the P.W.S. rope with artificial defects.

43233 Udpa, L.; Lord, W. A search-based imaging system for electromagnetic nondestructive testing IEEE Expert, Vol. 4, No. 4, pp. 18-26 (Winter 1990)

This paper considers the magnetostatic leakage field method of nondestructive testing, commonly used to inspect steel billets for use in the steel, nuclear power or aerospace industries. The problem of flaw reconstruction from test specimen interiors, using the probe response signal, is addressed. The finite-element model is used to solve the forward problem. This first formulates defect reconstruction as a parameter estimation problem. A search procedure is the initiated which uses an algorithm to search for the optimal solution. The algorithm can be modified at several places, including the representation of problem state space, state transition rules, use of heuristic information, transition probability matrices, and choice of a relevant search procedure.

42492 Atherton, D.L. Magnetic inspection is key to ensur ing safe pipelines Oil and Gas Journal, Vol. 87, No. 32, pp. 52,53,56,58,61 (7 Aug. 1989)

This paper considers the advantages and limitations of two magnetic techniques for inspecting buried natural gas pipelines. The safety and economic considerations are also covered. Magnetic flux leakage anomaly detectors offer in-service inspection via inspection pigs. These are excellent for detecting corrosion but offer little sensitivity to cracks. Allowance must be made for stress to ensure accuracy. Remote field eddy current techniques

ND T Abstracts

allow sUess-corrosion cracks to be detected. Operation limitations of each technique are noted and some existing solutions detailed.

41310 Compiled by Commission V of the International Institute of Welding Handbook on the magnetic examination of welds The Welding Institute, UK, 52 pp. (1987) ISBN 0 85300195 2

Covers the basics of magnetic flux leakage testing, and the capabilities and limitations of its application to the detection of surface and near-surface defects in welds.

41307 Zamloot, G. Improved nondestructive testing of 60 mm M720 mortar projectile magnetic flux leakage inspection system of M720 mor ta r Army Armament Research Development and Engineering Centre, Dover, New Jersey (United States) AD-A196060/8/GAR, 34 pp. (Aug. 1988)

The objective of this project was to provide basic outline drawings (BOD) for the concept design and specifications of an automated magnetic flux leakage inspection system (AMFL1S) for detecting anomalies/flaws within the projectile body of the 60 mm mortar. The inspection of mortar projectile body for anomalies was performed by magnetic particle inspection (MPI) followed by visual inspection before and after painting the projectile using normal light. MPI cannot indicate the depth of a crack (anomaly). The item tested was rotated in the field of a magnet and was magnetically saturated. In the absence of defects (discontinuities), the magnetic flux lines (saturated) continue to be contained and flow within the interior of the test item. If any defects were present, they forced some of the flux lines to flow external to the surface of the test item producing a leakage field.

41305 Luz, H. Further development of the high-power alternating-field leakage-flux method for sensitive surface crack testing of black material Proceedings of the 12th World Conference on Non-Destructive Testing, Amsterdam (Netherlands), 23-28 Apr. 1989, Vol. 2, pp. 891-895. Edited by J. Boogaard and G.M. van Dijk, Elsevier, 1989.

The high-power alternating-field leakage-flux method (HP-ALF) is described in this paper. It is particularly suitable for sensitive surface crack testing of black materials and is used for automatic testing of hot-rolled tubes. The HP-ALF method has led to up to a factor of 3 in improvements in detection performance for surface crack flaws, which has proved especially useful in the automobile industry. Contrary to earlier assumptions, residual background noise is produced by magnetic inhomogeneities near to the material surface which are not adequately saturated magnetically because of their depth, rather than by surface roughness and scale.

41107 Bubeck, E.; Geweke, W.; Paweiletz, R. Transversal flaw testing of seamless tubes - a new test system Proceedings of the 12th World Conference on Non-Destructive Testing, Amsterdam (Netherlands) 23-28 Apr. 1989, Vol. 2, pp. 1331-1333. Edited by J. Boogaard and G.M. van Dijk, Elsevier, 1989.

The new leaka~ flux test system for ferromagnetic tubes of diameter 1" - 7" shows an excellent flaw detectability due to the optimized construction of the transmitter system with its magnetic circle, probes and test heads. The modem test electronics is controlled manually and/or via computer interface. This and further features like function control, signal storage and automatic sensitivity balance makes the whole system reliable and cost-efficient for those tube manufacturers who sell high quality products.

41100 Uetake, I.; lto, H.; Saito, T. Quanti tat ive evaluation of defects by magnetic leakage flux testing using a sensor composed of multiple magnetic elements Proceedings of the 12th World Conference on Non-Destructive Testing, Amsterdam (Netherlands) 23-28 Apr. 1989, Voi. 1, pp. 293-298. Edited by J. Boogaard and G.M. van Dijk, Elsevier, 1989.

A change of sensor lift-off distance and the oblique angle of surface defects causes uncertainty in estimating defect sizes. This paper reports that a sensor composed of two Hall elements is useful to remove these difficulties.

40892 Edwards, C. A study of magnetic particle inspection University of Hull (United Kingdom), Ph.D. Thesis, (Oct. 1986)

Magnetic Particle Inspection (MPI) reveals flaws in ferromagnetic

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