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The Journal's focus is on Nondestructive Testing (NDT) and Ultrasonic Testing (UT) in particular
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|This Month's Introduction|
One article related to NDT for concrete is "The Impact-Echo Method" by
M. J. Sansalone and W. B. Streett. In conjunction with this article we
are pleased to introduce this month Mr. Streett, who will serve as a
coordinator for comments on concrete for the February 1998 Forum of
NDT.net. He is now our Virtual Session Chairman.
|NDT - Method|
This Month's Articles
Assessment of the Deterioration of Concrete in NPP - Causes, Effects and Investigative Methods
This report briefly discusses actual and potential deterioration processes and their causes based upon several years of investigative work on concrete structures in Scandinavia, including NPP and provides some input for development of practical inspection procedures. Some common deterioration processes are highlighted to bring attention to the need for inspection. A more detailed study of chloride attack and reinforcement corrosion is presented, and finally a summary is given of state-of-the-art technologies for in-situ testing.
Peter Shaw, Aimin Xu
The Impact-Echo Method
Impact-echo is an acoustic method for nondestructive evaluation of concrete and masonry, invented at the U.S. National Bureau of Standards (NBS) in the mid-1980's, and developed at Cornell University, in Ithaca, New York, from 1987-1997. This article provides a brief description of the method, information about test equipment manufactured by Impact-Echo Instruments, LLC of Ithaca, New York, a description of a new book about impact-echo, and a list of case studies describing a variety of applications. In December of 1997 the American Society of Testing Materials (ASTM) approved a new standard entitled, "Standard Test Method for Measuring the P-Wave Speed and the Thickness of Concrete Plates Using the Impact-Echo Method." This standard will appear in the 1998 Annual Book of ASTM Standards. The article provides 48 References of the Impact-Echo Book.
Mary J. Sansalone and William B. Streett
Check also the Forum Discussion
This document at the NIST server provides a brief introduction to the principles of the impact-echo method. A list of impact-echo publications is provided for those requiring more information.
|Simulation of Ultrasonic Flaw-detection in Concrete with a varying Percentage of Air Inclusions |
The elastic wave-propagation of ultrasonic signals in concrete with varying percentage of air inclusions is simulated in two dimensions using finite-difference-methods. Snapshots of the wave explain their different behaviour in several kinds of inhomogenous models with varying contrasts in their elastic parameters. The received A- and B-Scans show the negative influence of size-effects and air inclusions on the data and the induced problem to detect a flaw inside the concrete.
E. Burr, N. Gold, C.U. Grosse, H.-W. Reinhardt
Application of a modified SAFT-algorithm on synthetic B-scans of coarse grained materials |
In Non-destructive-testing the Synthetic Aperture Focussing Technique is frequently used for getting an image of the investigated specimen from ultrasonic-data. It is shown that the algorithm can be modified in a simple way to get better results for imaging purposes.
E. Burr, C. Große, H.-W. Reinhardt
Non-Destructive Determination of Stiffness of Asphalt Concrete|
An Example of our NDTnet '97 CD-ROM Archive. The aim of this project is to determine material stiffness of solids with large inhomogeneities. We are using structural wave propagation to get the global material stiffness. Material stiffness of asphalt concrete depends on the frequency and the temperature. We examine these influences for different asphalt concrete compositions. by A. Hochuli and M.B. Sayir, ETH Zürich.
NDTnet Back Issue: Our April '97 issue focused on Ultrasonic Testing in Civil Engineering.|
In this month we had 9 papers of the International Symposium NDT-CE '95 and much more.
| Diagnostics of fatigue cracks in aero-engine compressor rotor blades |
Most dangerous to operational use of aircraft engines are fatigue cracks that nucleate at locations with difficult access for testing. Ultrasonic surface waves were applied using digital flaw detector SOFRATEST and special probe heads were developed for primary laboratory examinations. To discriminate between fatigue cracks and those coming from blade geometry Fast Fourier Transform of signals was applied. Basing on this analysis blade inspection procedures were developed and implemented in practice, to allow the remained safe life prediction.
B. Zajac, Air Force Institute of Technology, Warszawa (PL)
Inspection Techniques for Detecting
Corrosion Under Insulation |
Corrosion under insulation (CUI) is difficult to find because of the insulation cover that masks the corrosion problem until it is too late. It is expensive to remove the insulation, particularly if asbestos is involved. There are a number of methods used today to inspect for corrosion under insulation. The main ones are profile radiography, ultrasonic spot readings, and insulation removal. The other method now available is real-time X-ray. Real-time X-ray has proven to be a safe, fast and effective method of inspecting pipe in plant operations.
Michael Twomey, CONAM Inspection Inc
Nondestructive testing of stress states by X-ray methods in Poland |
Nondestructuctive testing of stress states in samples and products are performed by different methods. Among them are well-known X-ray methods called X-Ray Tensometry. This paper describes: the outline of development of stress states testing by X-ray methods in Poland and the scientific literature main by books in this branch in Poland.
D. Senczyk, K Lis, Poznan University of Technology, Poznan (PL)
|Wire cable testing using high resolution magnetic induction [D]|
The high resolution magnetic-inductive test method described here supplements the results achieved by conventional test methods. Initial experience with the new method has produced surprisingly good results. Up till now additional tests using radiographics have not been necessary. The ability to differentiate between damage caused by corrosion and wire fractures in fully sealed cables has been improved. A decisive step has been made to increase safety in aerial cableways. In the following sections the two previously used test procedures are described and this new imaging method is introduced.
August Haller, EMPA Dübendorf . See also our News Flash "All Articles of the joint German-Austrian-Swiss NDT Journal are online".
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News Archive '98
News Archive '97
News Archive '96
NDT Methods for Flaw Detection during Welding |
The final ultrasonic TOFD trials of the BRITE-EURAM II project 'NDT Methods for Flaw Detection During Welding' took place in Oct 1997. The aim of the trials was to demonstrate NDT using TOFD whilst welding was taking place - i.e. the ultrasonic probes were to be placed a short distance behind the weld torch. The trials successfully demonstrated the techniques and methods developed during the four year study to undertake NDT during welding.
Check also the Forum Discussion
How Tekron Services use the Impact-Echo Technology
The 1998 Nondestructive Testing Industry Directory
The web site of The British Institute of NDT has recently been updated
DACH Zeitung - Fachbeiträge Online
Job open at Lawrence Livermore Laboratory NDT Division
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Review of Last Month's Topics
Plus 66 Matches for search Conference or Symposium and 64 Matches for search Concrete or Infrastructure in the NDT Newsgroup from 1997 to Jan 1998