NDTech Newsletter #11

Bolt Elongation Measurement System

The NAVSEA Underwater Ship Husbandry program has fostered development of numerous systems that allow ship maintenance, inspection and repair tasks to be performed without dry-docking. One such task is the replacement of propeller blades on cruisers and destroyers fitted with controllable, reversible pitch propellers (CPP). These blades, which weigh tip to 6,000 pounds, are each held in place with eight large bolts that are stretched to produce over 100,000 pounds preload on each bolt.

This ultrasonic system is used to measure bolt elongation on the order of 0.010 inches, with accuracy and repeatability better than ± 00005 inches. Although the CPP blade bolts arc manufactured with a flat-bottomed hole for measuring elongation with a dial indicator, conventional measuring systems have proved unreliable for use underwater. The current system measures changes in the bolts' length by reflecting ultrasound off the hole's flat bottom, and is straightforward in theory. However, attaining the required accuracy, and surviving use in the underwater environment poses a reasonable challenge. The current design accounts for salinity and temperature variations, geometrical repeatability during installation, and is extremely robust.

This article was taken from the United States Navy Coastal Systems Station

Diving and Life Support Division. For more information about their typical

projects visit their website at http://www.ncsc.navy.mil/CSS/Dept/A50/Dsb/index.htm.

*From NTIAC Newsletter, Vol. 23 #24.

Kennedy Space Center Interactive Training for NDE

The Kennedy Space Center (KSC) has a web interactive training site for nondestructive evaluation as it pertains to NASA. They are currently offering three different NDE courses. All of the courses are targeted toward NASA employees and other interested in the topics. Below is a list of the three classes along with a short description of each.

• Introduction to Nondestructive Evaluation: This section covers visual inspection, liquid penetrant testing, magnetic particle testing, eddy current testing, ultrasonic testing and radiographic testing. This training does not count toward certification. It is to be used as an overview and explanation of these methods.

Prerequisites: None.

• Introduction to Radiography: This section covers the science of radiography, its advantages and limitations, applications at KSC, safety precautions, equipment, and radiographic film processing and interpretation.

Prerequisites: Introduction to Nondestructive Evaluation course.

• Introduction to Ultrasonic Testing: This section covers ultrasonic testing used at KSC and the basic theory of ultrasonic testing.

Prerequisites: Introduction to Nondestructive Evaluation course or equivalent knowledge.

Since the course is offered over the internet there are certain computer requirements necessary to run the training programs. First, the computer must have an active X capable browser such as Internet Explorer (3.0 or higher) or Netscape (3.0 or higher) that is JAVA capable. Also, Adobe Acrobat Reader and Shockwave for Director 5.0 are necessary.

To get more information on the program, please visit http://pointcast.ksc.nasa.gov/wit/. The site gives general information about the program, a catalog, registration information, and tools. It is also the access point for training.

*From NTIAC Newsletter, Vol. 23 #24.

Vision Testing Guidelines for NDE Operators

Nondestructive testing has advanced at an incredible pace recently with technological developments, but for some methods of testing, no matter how good the equipment, the final analysis comes down to the ability of the operators eyes. Operators not only need to have good visual acuity to be able to detect flaws, but methods such as penetrant testing and magnetic particle testing require the ability to differentiate colors. Unfortunately, in the field of NDE, there are currently no set exams or guidelines for visual acuity or color vision deficiency.

Visual acuity is commonly tested using either the Snellen test or the Jaeger test. The Snellen test is what most people think of when talking about eye tests. It consists of a chart with rows of letters with varying sizes. The targeted result of this test is 20/20 vision. Similarly, the Jaeger test has rows of sentences with varying text size.

To detect color vision deficiency, two tests can be used. The more common test is called the Ishihara Test. This test uses a series of charts with "hidden" symbols. A symbol, such as a letter or a number, is made of small dots of a color and surrounded by a circle made of small dots of another color. The subject is asked to find the hidden symbol. Another test is called the City University Color Vision Test. This test has a circle of one color surrounded by four different colors. The object of the test is to determine which surrounding color matches the inner dot best.

Although all four of the above tests are very useful, they do not meet the needs of the NDE community. The Snellen test would be useful if there were set qualifications for NDE personnel. For instance, pilots have a vision standard set at 20/20, or at least correctable to 20/20. As for the color deficiency tests, they only reveal if there is a problem distinguishing between two colors The problem in NDE often lies in determining a specific edge line or contrast. A person could fail thc Ishihara test, but still be able to fulfill his/her job requirement. Tests and standards need to be developed that are specific to the NDE community. It is crucial to the reliability and the reputation of the profession.

Currently, Lavender International Nondestructive Testing in the UK is developing tests for both visual acuity and color differentiation related to NDE. The tests will cover testing in both white and black light conditions. According to the owner of the company, Stephen Lavender, their product should be on the market soon. To contact them, visit their website at www.lavender-ndt.com.

NDE operator's vision will continue to be a consequential issue until vision testing guidelines are developed and become standard practice. It is vital far NDE leaders to take up this challenge and lead NDE to new levels of reliability.

*From NTIAC Newsletter, Vol. 23 #24.

DOD Inspection Needs

The Department of Defense currently has several pressing NDE inspections needs. The solutions to these problems must allow field inspections on parts that have been removed from service.

Kinks and Reduced Tensile Strength in Strength Members (Ropes) of Tethers: These tethers are constructed of a polymer hose filled with: electric cables, oil, a primary strength member, and other smaller ropes for added safety. The tethers fail because small kinks in the primary strength member, which is made of Kevlar rope, reduce tensile strength as much as 50%. The sectional Kevlar ropes can be 100-200 ft. per section with an overall length extending thousands of feet, and must be inspected with the overall tether intact.

Reinforcing Cord Degradation/Breakage in Polyurethane Hose: The DoD uses polyurethane hoses that are longitudinally reinforced with 26 Kevlar cords equally spaced around the hose. Accumulated damage and breaking of the reinforcing cords can lead to failure of the hose. These cords run parallel to each other for the length of the hose. 1-lose diameter ranges from approximately 1" to 3", with wall thickness approximately 0.1". The Kevlar reinforcing cords are embedded at hose midwall, and have diameter of 0.030-0038" - Overall hose length can be hundreds of feet.

Crack Detection in Polymer Protective Coverings: Cracks in rigid polymer coverings can allow degradation of the metallic substrate. The coverings are cylinders with outside diameter just over one inch and thicknesses from 0.030-0.040". A quick, reliable method for detecting such cracks is desired.

Please contact NTIAC if you are aware of solutions to the above problems.

HIGHLIGHTED LINK

NTIAC has added a new link to their website: http://www.tfhrc.gov/hnr20/nde/splash.htm. This is a link to the Federal Highway Administration's NDE Validation Center. The website has information about their staff, current projects, and laboratory facilities.

For more links, visit their website at http://www.ntiac.com/links/.

Additional entries have been placed in the NTIAC database since last issue. The total number of citations available to the NDE community is now close to 57,000.

NTIAC

Texas Research Institute Austin, Inc.

415 Crystal Creek Drive

Austin, TX 78746

Phone: (800) 684-2239 or (512) 263-2106

Fax: (512) 263-3530

Email: ntiac@access.texas.gov

Website: http://www.ntiac.com

*From NTIAC Newsletter, Vol. 23 #24.

New NTIAC Publications

NTIAC has completed a series of new special publications which will be available for purchase from NTIAC soon. These publications, which include State-of-the-Art Reports and Technology Assessments, cover a variety of technical topics of current interest in the area of NDE.

State-of-the Art Reports

$75 U.S./$85 International

NTIAC-SR-98-O1 Neutron Radiography by Harold Berger and Frank Iddings NTIAC-SR-98-02 Heat Damage in Graphite Epoxy Composites: Degradation, Measurement, and Detection by George Matzkanin and George Hansen

NTIAC-SR-98-03 NDE of Hidden Corrosion by George Matzkanin and Jacob Easter

NTIAC-SR-98-04 NDE of Cracks in Aircraft by Jacob Easter and George Matzkanin

Technology Assessments

$55 U.S./$65 International

NTIAC-TA-98-01 Laser Ultrasonics by James Wagner and James Spicer NTIAC-TA-98-02 NDE of Process Control of Polymer Matrix Composites by Tom Yolken

The following two publications are nearing completion and will be available by Fall 1999.

NTIAC-TA-98-03 Micro-Electromechanical Systems (MEMS) for NDE of Navy Aircraft by Russell Austin and George Matzkanin

NTIAC-TA-98-04 Magnetic Particle Inspection: Capabilities and Problems by Lydon Swartzendruber

To order any of the above publications, or for more information, please contact:

Shelly Clark

NTIAC

Phone: (800) 684-2239 or (512) 263-2106

Fax: (512) 263-3530

Email: clark@ntiac.com

Website: http://www.ntiac.com

*From NTIAC Newsletter, Vol. 23 #24.

Computer Network for Distribution of Radiographic Images

The network would also be used for training in radiography.

John F. Kennedy Space Center, Florida

The Radiographic Imaging Performance Support System (RIPSS) is a developmental computer network intended to serve as (1) a central electronic archive for the storage, retrieval, and analysis of radiographic images generated in nondestructive evaluation (NDE) laboratories at Kennedy Space Center and (2) a

system for training users in radiographic techniques and in the analysis and interpretation of radiographic images. The archival, analytical, and training subsystems are being developed concurrently and integrated to the extent possible to take advantage of synergies among them and thereby maximize the potential to enhance the performances of both NDE learners and practicing NDE professionals.

The RIPSS would supplant the present system, in which there is no central archive, and in which both analysis and training are impeded by the need to distribute original radiographic films for comparison. The RIPSS (see figure) would include a scanner and a database server computer, which would store the digitized information from the original radiographic films, making it unnecessary to handle the films after scanning them. Storage of the image information in electronic form would reduce the cost of distribution, provide some redundancy for protection against loss, provide systematic means for preventing access by unauthorized users, arid enable the use of automated,

computational techniques for retrieval and analysis.

The subsystems for storage, retrieval, and analysis of images would incorporate object-oriented data structures and internet-based multimedia formats for efficiency in development and deployment. Large multi-media files (for example, files containing images with text and audio annotations) could be accommodated. Advanced file-management features would be provided: One particularly notable feature of this type is the query by image contents (QBIC), which can be implemented with commercially available software. For example, if a specific section of pipe were tested on several occasions and its radiographic image scanned into the system on each occasion, then subsequent retrieval of one of the images would facilitate access to all like images. The software would find all images of segments of pipe having the same bend. The search could be narrowed by use of various parameter filters. This feature could be an excellent tool for the comparative analyses that are often performed in analyzing radiographic images.

The training subsystem of the RIPSS is based partly on the Kennedy Space Center developed 'Web Interactive Training" where: the capabilities afforded by the Internet and by state-of-the-art multimedia data-presentation techniques are exploited to deliver training from a server computer to client desktop computers on demand. Training can be interactive, and interactivity can be exploited to provide for testing and recording of a trainee's progress. The fully developed RIPSS would enable a trainee or other user to visually inspect a radiograph and to click on a section containing a discontinuity suspected to represent a defect. Underlying image-map coordinates would direct the user to a page that would describe the discontinuity and present case-study information about the radiograph. The user interface for both training and routine use in inspection of parts would be the same.

This work was done by Alexander H. Ladd, formerly of I-NET Inc., and David Metcalf of Merrimac Interactive Media Corporation for Kennedy Space Center. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com under the Information Sciences category.

Inquiries concerning rights for the commercial use of this invention should be addressed to the Technology Programs and Commercialization Office, Kennedy Space Center, (407) 867-6373. Refer to KSC-12000.

If you are a regular user of NIST's website at http://www.nist.gov, you will find a pleasant surprise on your next visit. If you haven't tried out the site before, however, now is a great time to get acquainted. An improved, more user-friendly NIST homepage is now in operation. New features include a site index, an upgraded search engine, a "hot news" section, a link to NIST atomic time and up-front connections to NIST's four major programs, including Measurement and Standards laboratories, the Advanced Technology Program, the

Manufacturing Extension Partnership, and the Baldrige Quality Program.

A special section, entitled "NIST and You," helps online visitors explore the agency's nearly 100&emdash;year&emdash;old history, get answers to frequently asked questions, take a virtual walk through the world of timekeeping, and learn how NIST is connected to everyone's daily life.

The new homepage also links users to the latest information about the more than 100 major conferences held at NIST each year.

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Testing Corrosion Prevention in Reinforced Concrete

John F Kennedy Space Center Florida

An accelerated-testing method has been developed for evaluating the effectiveness of various measures taken to prevent the corrosion of steel reinforcing bars ("rebars") cast into concrete. Such measures can include chemical admixtures incorporated into the concrete, coatings, penetrants, modified concretes, new reinforcing materials, and corrosion-inhibiting chemicals that migrate after being applied. The method is an improvement of standard G 109-92 of the American Society for Testing and Materials (ASTM). In preparation for testing, concrete blocks are cast with rebars inside, along with any appropriate corrosion inhibitor(s). Holes are drilled into the blocks for measurement of electrical potentials at interior locations; other holes are drilled to promote intrusion of saltwater. During exposure of a block to a saltwater or other corrosive environment, electrical potentials are measured at rebars as well as in holes. Corrosion currents are also measured, and polarization resistances are determined. Optionally, potentials can be applied to accelerate corrosion. At the end of a test, the blocks are broken for visual examination of the rebars.

This work was done by Rupert U. Lee of Kennedy Space Center and Joseph J. Curran of Dynacs Engineering Co., Inc. For further information, access the Technical Support Package (TSP) free online at http://www.nasatech.com under the Materials category.