NDT.org : Information : Newsletters : NDTech Newsletter #15

NDT TESTING TIPS FROM NDTECH - NEWSLETTER #15 - March 2000 



This issue of the Newsletter includes: 



1. Digital Radiography: A Technology Whose Time Has Come 

2. Publications 

3. "Sniffers" Expand Law Enforcement's Ability To Detect Explosives And Narcotics 



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The NDTech Newsletter is published periodically by NDTech, a consulting firm offering nondestructive

testing, services, and instruments. This newsletter is distributed by email and covers brief descriptions of

some useful but less publicized radiographic, ultrasonic, penetrant, magnetic particle, and other NDT

methods. You will automatically receive the newsletter, at no cost. If you wish to be removed from the

NDTech Newsletter, simply reply with "Remove" as the subject. 



To find out more about NDTech and its nondestructive testing consulting services and instrumentation,

visit the NDTech website at http://www.ndtech.net/ 

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1. Digital Radiography: A Technology Whose Time Has Come 



Film-based radiography has a long history and in many respects is an excellent imaging tool. In particular,

film has excellent spatial resolution and, an area detector, supports rapid imaging of inspection objects. On

the other hand, film requires photographic development which can be inconvenient and time consuming,

and may preclude recording changes in objects that occur even moderately rapidly. Film also exhibits a

tradeoff between contrast and dynamic range, making it impossible to image some objects with good

contrast over their full range of attenuation. Film also requires photographic equipment that can be

inconvenient and time consuming, and film processing also poses an enviromental problem. 

The emergence of large, fast computer systems and sophisticated image processing software coupled with

the development of solid-state detectors have made digital imaging and real-time radiography both

attractive and feasible, helping propel digital radiography to a position of prominence in aerospace and

other industry applications. Contrast enhancement, spatial filtering, and other image processing can be

performed digitally, and solid-state detectors offer a wide dynamic range. Digital radiography avoids many

of the drawbacks of film radiography. Combining digital radiography with sophisticated and flexible image

processing can provide image quality that in some respects rivals or surpasses that of film. 

Digital radiography produces an image similar to a traditional medical X-ray, with internal features

superimposed in the image. Such images are called projection radiographs because they show a plane

view of the object, with internal features superimposed on the image. 

In digital radiography, data is collected by moving the X-ray source and detectors linearly along the entire

length of the object; alternately, the object can be moved past the stationary source and detectors-similar

to the technique used by airport baggage inspection systems. Narrow lines of X-ray attenuation data are

collected at brief time intervals. The X-ray measurements are then digitized and displayed as a

two-dimensional image. 

A digital radiography image is also similar to a real-time radiography image, although it has a much higher

contrast resolution. This resolution is due to the type of the detectors that are used, which allows as many

as 65,000 intensity (gray) levels to be present in the image. 

Four major classes of X-ray detector systems are used in digital radiography: 



1. X-ray intensifier tube fluoroscopy system: These systems are widely used in medical and industrial

radiographic applications. Vacuum tube intensifier systems convert X-ray photons into light photons with

a phosphor screen. The light photons are then converted to electrons by a photocathode, and the

electrons are then accelerated to thousands of eV. These accelerated electrons are then focused onto an

output phosphor screen and are converted back to light photons to provide an image. The image is viewed

through a lens with a television camera. 

2. X-ray phosphor/vacuum tube low-level-light camera system: These systems do not require image

intensification. The X-ray phosphor does not need to be in a vacuum tube and can even be shaped over

the object. Gadolinium oxysulfide is activated with terbium, a phosphor with a very high X-ray absorption

cross section. Image isocon camera are used with this system since charge-coupled device (CCD) camera

without cooling to have not produced sufficient sensitivity. 

3. Linear array scanner system: This system utilizes an X-ray phosphor such as transparent CdWO4 or

CsI single crystals in direct contact with a semiconductor photodiode array. The crystals are cut into

pieces and become discrete pixels in the system. The object is scanned through the fan beam/detector

system, and a computer constructs a line-by-line image. A collimated fan beam/detector system

significantly reduces X-ray scatter compared to noncollimated beams and will produce very accurate

images. 

4. Fiber-optic CCD system: A fiber-optic scintillator (FOS) faceplate is used to detect the X-rays and is

made with a luminescent fiber core. The core fibers in the faceplate are 10mm to 20mm in diameter.

When exposed to X-rays, scintillation in each fiber is channeled to the face of the plate, providing a very

sharp image plane that can be bonded directly to a CCD array. The FOS/CCD system offers high X-ray

absorption and improved image acquisition time over typical linear array detection system. This system

can be made lightweight and rugged for scanning of large aerospace structure. 



In addition to these four imaging system that have been used over the past several years for digital

radiography, a new flat panel imaging device has recently been developed to meet the needs of the

extremely large medical digital X-ray imaging market. The major distinguishing feature of this new

technology is that electrons are produced directly by the interaction of the X-ray radiation with a flat panel

of material such as amorphous silicon (amSi) or amorphous Selenium (amSe), and the electrons are

directly collected and processes. There are no scintillation or other conversion processes. 

With any method of digital radiography, image quality is a direct indication of the ability of a radiographic

process to record images that are representative of the test piece. The quality of a radiographic image can

be defined as the ability of the image to reflect the spatial variations in the attenuation of X-rays by the

examined object. In practice, several factors can degrade the object, including: 1) finite source size, 2)

geometric and spatial resolution, 3) beam scatter, 4) screen or detector absorption and emission

efficiency, and 5) object motion. 

The nondestructive evaluation (NDE) uses of digital radiography are varied, including corrosion detection

in aircraft and aerospace systems, metal casting process control, evaluation of advanced composites,

failure analysis of electrical and electromechanical components, inspection of rocket motors, monitoring

containers of weapons-grade plutonium for deterioration, and inspection of welds. 

Compared to film radiography, digital radiography technology offers imaging without wet-film processing,

shorter exposure times, a larger dynamic range, and digital imaging. These features, combined with instant

image retrieval and a tolerance for exposure time, offer advantages in field radiography. Recent

advancements in digital radiography have provided X-ray images heretofore unobtainable with

radiographic techniques. 

The rapid increase in available data from detector system will require advanced digital hardware and

software to access and manipulate the data. New robotic hardware is also critical in the automation of

more sophisticated production processes. New software will be required for automated evaluation. With

the development of such technology will come radiographic systems capable of automated inspection and

evaluation of such critical defect features as cracks, voids, disbonds, and corrosion in aircraft and

aerospace vehicles. 

Advanced digital radiography will play a key role in the NDE of future aerospace components as

automated X-ray inspection of in-process manufactured items provides quality control capabilites not

previously possible. Digital radiography will also play a key role in the inspection of aircraft for cracking

due to stress corrosion. Other applications of digital radiography will emerge as the technology grows and

is proven in practice. 

For more information about digital radiography, please contact NTIAC: 

NTIAC 

415 Crystal Creek Drive, Austin, TX 78746 

Phone: (800)NTIAC-39/(800)684-2239 

(512)263-2106 

Fax: (512)263-3530 

Email: mailto://ntiac@access.texas.gov 

Website: http://www.ntiac.com 



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2. Publications 



Nondestructive Testing Handbook,3rd Edition, Vol. 2:Liquid Penetrant Testing-Noel A. Tracy

(technical editor) and Patrick O. Moore (editor). The handbook outlines the principles, equipment,

materials maintenance, methodology, and interpretation skills necessary for liquid penetration testing. The

third edition adds new sections on filtered particle testing of aerospace composites, quality control of

down hole oil field tubular assemblies, and probability of detection, and considers new regulations on CFC

fluids throughout the text. 

This book is available from the American Society for Nondestructive Testing at http://www.asnt.org. It is

priced at $181.25 worldwide, $135.00 for ASNT members. This book was published in September 99. 



Nondestructive Characterization of Materials IX, Vol.497-Robert E. Green, Jr. (editor). This book is

a collection of technical papers presented at the 9th International Symposium on Nondestructive

Characterization of Materials held June 28 through July 2, 1999 in Sydney, Aulstralia. The papers,

representing the latest developments in nondestructive characterization of materials, are organized by

topic: acoustic emission, electrical, laser ultrasound, magnetic, multiple techniques, optical, thermal,

ultrasonics, vibrational, and X-ray, neutrons, positrons, protons. 

This book is available from the American Insitute of Physics at http://www.aip.org or from

http://www.bn.com. It was published in December 1999 and has 732 pages. The book is priced at

$185.00. 



1st International Conference on Barkhausen Noise and Micromagnetic Testing Conference

Proceedings. The interest and involvement of researchers and the commitment of those who pursue the

industrial applications of the Barkhausen noise method have been equally important in elevating the

method to its high level today. The papers included in these proceedings cover the theory of the physical

phenomenon of the magnetic Barkhausen effect and the practical applications of micromagnetic testing. 

These proceedings are available from America Stress Technologies, 267 Kappa Dr., Pittsburgh, PA

15238-2817, USA; Fax:(412)963-7552. They are available in either book or CD form and cost $40.00. 





Nondestructive Testing (NDT) Market Research Reports. Based on questionnaire responses from

over 550 end users, these texts provide information regarding online versus offline testing, NDT spending

by end users , and more. Each volume covers a different aspect of the NDT industry: Vol.1-The U.S.

Market for Film-based Radiography Equipment and Supplies; Vol.2-The U.S. Market for Non-Film

Radiography:Radiography, Digital Radiography, Computed Radiography, and Computed

Tomography;Vol.3-The U.S. Market for Industrial Eddy Current Testing Equipment and Other

Electromagnetic Methods;Vol.4-The U.S. Market for Industrial Ultrasonic Testing Equipment and

Acoustic Emission Equipment;Vol.5-The U.S. Market for Magnetic Particle Testing and Liquid Penetrant

Testing Equipment and Supplies for Industrial NDT;Vol.6-Unabridged composite of Volumes 1 through

5;Vol.7-The U.S. and Canadian Market for Nondestructive Testing Services; and Vol.IR-The U.S.

Market for Commerical & Military Infrared Imaging and Infrared Thermometry Equipment. 

These volumes are available from Maxtech International, Inc. 202 Stillson Rd., Fairfield, CT

06432-3227,USA. Phone:(203)362-0165. Website- http://www.maxtech-intl.com. 



Ultrasonic Waves in Solid Media-Joseph L. Rose. Ultrasonic wave techniques, used increasingly in

areas ranging from nondestructive inspection of materials to medical diagnosis, evolved from basic

physical principles of wave mechanics. This book brings together basic physics and modern applications.

The author explains the physical principles of wave propagation and then relates them to ultrasonic wave

mechanics and the more recent guided wave techniques used to inspect and evaluate aircraft, power

plants, and pipe-lines in chemical processing plants. Among the topics covered are wave propagation in

plates, rods, hollow cylinders, and multiple layers in solid and composite materials; reflection and

refraction;surface and subsurface waves; and horizontal shear wave propagation. 

This book can be found at http://www.cup.org. The book is priced at $90.00 and has 472 pages. It was

published in August 1999. 



Nondestructive Testing, Annual Book of ASTM Standards, Vol.3.03-American Society for Testing

and Materials. This volume contains over 150 standards for performing nondestructive testing of

engineering materials, structures and assemblies to detetc flaws and characterize materials properties. The

main subject divisions for the test methods and analytical procedures included in the book are

Radiography, Magnetic Particle and Liquid Penetrant Examination, Acoustic Emission, Ultrasonic,

Electromagnetic, and Leak Testing. 

A more detailed summary as well as the book can be found at http://www.astm.org. The book is priced at

$123.00 in North America, $135.00 elsewhere and has 1,074 pages. It was published in November 1999. 



Nondestructive Testing Radiography (Programmed Instruction Handbook Series)-Robert W. Smilie

and George Pherigo(editor). This series includes books on the following topics: Film Handling and

Processing, Making Radiographs, Origin and Nature of Radiography, Radiation Safety, Radiography

Equipment, and Nondestructive Testing. 

This book series can be found at http://www.amazon.com and http://www.bn.com. The series is priced at

$92.50 and had 1,362 pages. It was published in December 1999. The individual topic can also be found

at http://www.bn.com for $18.50 each. 





Flaw Detection and Characterization in Heat Exchanger Tubing-Kenji Krzywosz and Larry Cagle,

Jr. As a collaborative project between Materials Technology Institute (MTI) and the EPRI NDE Center,

an evaluation of nondestructive evaluation techniques was conducted using realistic heat exchanger tubing

mockups in order to assess the inspection capabilities of the various techniques to detect and size tubing

flaws. The evaluation involved seven participating vendors utilizing nine different examination techniques.

Mockups were made of nonmagnetic and ferromagnetic tubing. The techniques evaluated included laser

optic, eddy current, remote field eddy current, IRIS ultrasonic, flux leakage, and NERASON ultrasonic.

Performance of the individual techniques is ranked based pre-established criteria. 

This report will be available in May 2000 from MTI Publications. They can be contacted at

mailto:mtiadmin@mti-link.org. The report is priced at $40.00 for nonmembers. 



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3. "Sniffers" Expand Law Enforcement's Ability To Detect Explosives And Narcotics 



Researchers at the Department of Energy's Sandia National Laboratories have developed a handcarried

device that, like a trained police dog, could sniff out the faint odors of drugs and bombs ar airports,

border crossings, military installations, and schools. The portable device is a miniaturized version of an

explosives-detecting walk-through portal Sandia developed for the Federal Aviation Administration (FAA).

The portal, which blows a puff of air over a airplane passenger and checks for minute levels of explosives

in the airflow, might soon be seen at U.S. airports as a security-screening tool. 

Recent improvements in the portal's underlying chemical preconcentrator technology are enabling

ever-smaller sniffing tools. Miniaturization of the preconcentrator allows the development of smaller

detection tools that are portable, cheap, sensitive, and fast. 

For more information about the portable air sniffer, contact Kevin Linker, mailto:kllinde@sandia.gov. 



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Copyright © 1999 NDTech. 













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