E-NDE

Minkov.D. and Shoji.T., Third International Workshop E NDE 97, Workshop Digest, pp.76-77... 

Due to their high costs, weight and size conventional NDE ultrasonic transducers are not suited for active SHM applications. However, novel 1-3 composite transducers such as piezo fiber composites (PFC) are adapted quite well to SHM applications. They can be used for passive as well as for active methods i.e. as transmitters and receivers for ultrasonic waves. PECs are small, lightweight and extremely robust and thus can be structurally embedded for e-NDE purposes in a large number. 

Arzhaev A T, Kiselyov V.A., Bougaenko S E., Strelkov B.P, Badalyan VG, Vopilkin, A.Kb. Safety significance of Augur-4.2 on-site applications at RBMK NPPs. In NDE Techniques Capability Demonstration and Inspection Qualification, U. EstorffandP. Lematre (Eds ), 1997, pp, 251-259. 

There have been numerous efforts to inspect specimens by ultrasonic reflectivity (or pulse-echo) measurements. In these inspections ultrasonic reflectivity is often used to observe changes in the acoustical impedance, and from this observation to localize defects in the specimen. However, the term defect is related to any discontinuity within the specimen and, consequently, more information is needed than only ultrasonic reflectivity to define the discontinuity as a defect. This information may be provided by three-dimensional ultrasonic reflection tomography and a priori knowledge about the specimen (e.g., the specimen fabrication process, its design, the intended purpose and the material). A more comprehensive review of defect characterization and related nondestructive evaluation (NDE) methods is provided elsewhere [1]. 

In contrast to a direct injection of dc or ac currents in the sample to be tested, the induction of eddy currents by an external excitation coil generates a locally limited current distribution. Since no electrical connection to the sample is required, eddy current NDE is easier to use from a practical point of view, however, the choice of the optimum measurement parameters, like e.g. the excitation frequency, is more critical. Furthermore, the calculation of the current flow in the sample from the measured field distribution tends to be more difficult than in case of a direct current injection. A homogenous field distribution produced by e.g. direct current injection or a sheet inducer [1] allows one to estimate more easily the defect geometry. However, for the detection of technically relevant cracks, these methods do not seem to be easily applicable and sensitive enough, especially in the case of deep lying and small cracks. 

R. Coulette, E. Lafond, F. Lepoutre, D. Balageas, M.-H. Nadal and C. Gondard, Laser ultrasonics NDE of two-layered samples . Review of Progress in Quantitative Nondestructive Evaluation, Vol 17, edsD. O. Thompson and D. E. Chimenti (Plenum, New York, 1998), to be published. 

In wide sectors of industry there is a growing need of inspection methods which go without liquid coupling media. The excitation of bulk and surface waves by means of air-coupled ultrasonic probes is therefore an attractive tool for NDE. This is tme e.g. for the rapid scanning of large composite structures in the aerospace industry [1]. In other cases, the use of liquid couplants is prohibitive like the thickness measurement of powder layers. 

Recent conferences held on the subject of NDE in Civil Engineering, e.g. NDE-CE 1993,... 

D. P. Thompson and D. E. Chimenti, eds.. Review ofiProgress in Quantitative NDE, Vol. 8, Plenum Press, New York, 1989 "Nondestmetive Testing and Quahty Control," Metals Handbook, 9th ed., Vol. 17, ASM, Metals Park, Ohio, 1989 Non-destructive Testing Handbook, American Society for Non-destmetive Testing, Columbus, Ohio, 1986. 

T. Leon-Salamanca and D. E. Bray, "Ultrasonic Measurement Of Residual Stress In Steels Using Critically Refracted Longitudinal Waves (L j )," R j". NDE 6(4) 1995 (in press). 

The organization responsible for providing the NDE (VT, RT, UT, PT, or MT) shall be in compliance with ASTM E 1212 and ASME BPV Code Section V, Article 14 (Examination System Qualification). 

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