Non-Destructive Testing Guide

Basic Principles of Ultrasonic Testing

2008-05-09T12:31:00.000-07:00

Ultrasonic Testing (UT) uses high frequency sound energy to conduct examinations and make measurements. Ultrasonic inspection can be used for flaw detection/evaluation, dimensional measurements, material characterization, and more. To illustrate the general inspection principle, a typical pulse/echo inspection configuration as illustrated below will be used.

A typical UT inspection system consists of several functional units, such as the pulser/receiver, transducer, and display devices. A pulser/receiver is an electronic device that can produce high voltage electrical pulses. Driven by the pulser, the transducer generates high frequency ultrasonic energy. The sound energy is introduced and propagates through the materials in the form of waves. When there is a discontinuity (such as a crack) in the wave path, part of the energy will be reflected back from the flaw surface. The reflected wave signal is transformed into an electrical signal by the transducer and is displayed on a screen. In the applet below, the reflected signal strength is displayed versus the time from signal generation to when a echo was received. Signal travel time can be directly related to the distance that the signal traveled. From the signal, information about the reflector location, size, orientation and other features can sometimes be gained.

Ultrasonic Inspection is a very useful and versatile NDT method. Some of the advantages of ultrasonic inspection that are often cited include:

It is sensitive to both surface and subsurface discontinuities.
The depth of penetration for flaw detection or measurement is superior to other NDT methods.
Only single-sided access is needed when the pulse-echo technique is used.
It is highly accurate in determining reflector position and estimating size and shape.
Minimal part preparation is required.
Electronic equipment provides instantaneous results.
Detailed images can be produced with automated systems.
It has other uses, such as thickness measurement, in addition to flaw detection.

As with all NDT methods, ultrasonic inspection also has its limitations, which include:

Surface must be accessible to transmit ultrasound.
Skill and training is more extensive than with some other methods.
It normally requires a coupling medium to promote the transfer of sound energy into the test specimen.
Materials that are rough, irregular in shape, very small, exceptionally thin or not homogeneous are difficult to inspect.
Cast iron and other coarse grained materials are difficult to inspect due to low sound transmission and high signal noise.
Linear defects oriented parallel to the sound beam may go undetected.
Reference standards are required for both equipment calibration and the characterization of flaws.

The above introduction provides a simplified introduction to the NDT method of ultrasonic testing. However, to effectively perform an inspection using ultrasonics, much more about the method needs to be known. The following pages present information on the science involved in ultrasonic inspection, the equipment that is commonly used, some of the measurement techniques used, as well as other information.

Electromagnetic Testing - (ET)

2008-03-14T01:41:00.000-07:00

Eddy current, penetrating radar and other electromagnetic techniques are used to detect or measure flaws, bond or weld integrity, thickness, electrical conductivity, detect the presence of rebar or metals. Eddy current is the most widely applied electromagnetic NDT technique. The eddy current method is also useful in sorting alloys and verifying heat treatment. Eddy current testing uses an electromagnet to induce an eddy current in a conductive sample. The response of the material to the induced current is sensed. Since the probe does not have to contact the work surface, eddy current testing is useful on rough surfaces or surfaces with wet films or coatings.

Eddy Current Testing

In standard eddy current testing, a circular coil carrying an AC current is placed in close proximity to an electrically conductive specimen. The alternating current in the coil generates a changing magnetic field, which interacts with the test object and induces eddy currents. Variations in the phase and magnitude of these eddy currents can be monitored using a second ’search’ coil, or by measuring changes to the current flowing in the primary ‘excitation’ coil. Variations in the electrical conductivity or magnetic permeability of the test object, or the presence of any flaws, will cause a change in eddy current flow and a corresponding change in the phase and amplitude of the measured current. This is the basis of standard (flat coil) eddy current inspection, the most widely used eddy current technique.

Barkhausen Noise Analysis (BNA)
Barkhausen Noise Analysis (BNA) method, also referred to as the Magnetoelastic or the Micromagnetic method is based on a concept of inductive measurement of a noise-like signal, generated when magnetic field is applied to a ferromagnetic sample. After a German scientist Professor Heinrich Barkhausen who explained the nature of this phenomenon already in 1919, this signal is called Barkhausen noise.

Ground Penetrating Radar (GPR) Ground penetrating radar is a nondestructive geophysical method that produces a continuous cross-sectional profile or record of subsurface features, without drilling, probing, or digging. Ground penetrating radar (GPR) profiles are used for evaluating the location and depth of buried objects and to investigate the presence and continuity of natural subsurface conditions and features.Ground penetrating radar operates by transmitting pulses of ultra high frequency radio waves (microwave electromagnetic energy) down into the ground through a transducer or antenna. The transmitted energy is reflected from various buried objects or distinct contacts between different earth materials. The antenna then receives the reflected waves and stores them in the digital control unit.

Magnetic Resonance Imaging (MRI) Magnetic resonance imaging (MRI) is an imaging technique used primarily in medical settings to produce high quality images of the inside of the human body. MRI is based on the principles of nuclear magnetic resonance (NMR), a spectroscopic technique used by scientists to obtain microscopic chemical and physical information about molecules.

Microwave InspectionMicrowave (or short-pulse radar) inspection techniques involve the transmission and reflection of relatively low frequency (often around 1 GHz) electromagnetic (EM) waves in various materials. The term ground penetrating radar (GPR) is often used to describe microwave inspection systems for locating utility lines below ground and mild steel rebar in concrete decks/pavements. Microwave inspection exploits the principle that dielectric properties of various materials affect the transmission and reflection of EM waves in those materials.

Distance Amplitude Correction (DAC)

2007-12-04T10:05:00.000-08:00

As mentioned previously, as a result of beam spread and attenuation, echo heights observed from equivalent defects decrease with increased distance. Consequently, a technique known as distance amplitude correction (DAC) is commonly employed to adjust signals generated at different distances for comparison purposes. This technique consists of generating a DAC curve that essentially indicates that a smaller echo at a greater distance may have similar properties to a larger echo at a lesser distance.
With straight beam transducers, blocks with flat bottom-hole specimens typically are used to generate the DAC curve. However, generating the same curve with an angle transducer is typically completed using a specimen with side-drilled holes. Regardless of the technique used to generate a DAC curve, the material used in the calibration block should be the same as the material in the test specimen due to potential differences in attenuation characteristics.
Figures 15a and 15b conceptually illustrate how a DAC curve would be generated for an angle beam transducer. In figure 15a, a side-drilled hole is shown in a test block that can be scanned with four different scanning patterns. Note that one could double the number of points on the DAC curve by using a second equivalent side-drilled hole at a different depth. When the echo signals are plotted together, the DAC curve shown in figure 15b results. This curve is referred to as "100 percent DAC." This means that for an equivalent defect in the test specimen, the echo signal will fall on this line. Smaller or larger defects in the test specimen will lie below or above the 100 percent DAC curve, respectively. The most accurate way to assess these defects is to repeat the DAC curve generation with a series of diameter holes. The result will be a series of curves that should allow for more accurate defect assessment. figures..

Neutron Radiography

2007-11-27T11:27:00.000-08:00

Neutron radiography provides a very efficient tool for investigations in the field of non - destructive testing as well as for many applications in fundamental research. A neutron beam penetrating a specimen is attenuated by the sample material and detected by a two dimensional imaging device. The image contains information about material and structure inside the sample because neutrons are attenuated according to the basic law of radiation attenuation. Contrary to X – rays, neutrons are attenuated by some light materials, as i.e. hydrogen, boron and lithium but penetrate many heavy materials. Neutrons are able to distinguish between different isotopes and neutron radiography is an important tool for studies of radioactive materials.
At the Atominstitute der österreichischen Universitäten (ATI) neutron radiographic investigations are performed for more then 35 years. The detectors mainly used are converter / film assemblies. However, these detectors are limited regarding their sensitivity, dynamic range and linearity. Due to rapid development of detector and computer technology as well as deployments in the field of digital image processing, new technologies are nowadays available which have the potential to improve the performance of neutron radiographic investigations enormously. Therefore, the aim of this work is to identify and develop two and three dimensional digital image processing methods suitable for neutron radiographic and tomographic applications, and to implement and optimize them within data processing strategies.

REAL TIME X-RAY INSPECTION

2007-11-26T12:51:00.000-08:00

Background
X-ray inspection is an invaluable part of Ford’s Materials Technology Centre as it strives to develop new materials and components for tomorrow’s cars. Since the removal of the open X-ray system, large lead-lined room, and wet plate film-processing laboratory from the Materials Science Department in 1999, X-ray inspection has been outsourced on an ad-hoc basis. However, since acquiring one of the latest developments in real-time X-ray inspection technology, the HMX 225 ST from X-Tek Systems last year, the department has not only reduced the cost of having to send components and systems to external test houses, but is expanding the use of X-ray non-destructive testing (NDT) in automotive inspection across a broad range of applications.
How Dependent is Ford on X-Ray Inspection?
The quality and quantity of X-ray inspection work Ford are now completing is a quantum leap ahead of what they were achieving before. The old X-ray room was used about four to six times a year for projects lasting for between one and two weeks, while the real-time X-ray system is used virtually every day. The time spent using the system is highly dependent on the aim of the investigation, material type and number of components, but typically most investigations are completed within one to two days if a few components are being inspected and computed tomography is not required.
Advantages of Computer Controlled X-Ray Inspection Equipment
A key feature of the HMX 225 ST system is image quality The microfocus X-ray system uses a very finely focused X-ray beam, with a focal spot size of less than 5 microns required for the generation of high magnification and high resolution images. Furthermore, unlike wet film technology, no chemical development is needed so images can be acquired in a fraction of the time and artificial features cannot be introduced during the development process.
What Materials Can be Analysed by X-Ray Inspection
The range of materials and components that Dunton deals with every day includes metal castings, metal sheet, powertrain components, polymers (including leather, seating, interior and exterior plastics), rubber, fasteners, chemicals, fluids, paints, and advanced materials, such as carbon fibre, composites and adhesives. Until recently many components were routinely sectioned on arrival in the department to allow detailed visual inspection. Now, in a growing number of cases, Ford engineers are using the X-ray system to carry out faster and more cost-effective test inspections.

Nondestructive testing (NDT)

2007-11-25T15:09:00.000-08:00

Nondestructive testing (NDT) are noninvasive techniques to determine the integrity of a material, component or structure or quantitatively measure some characteristic of an object. In contrast to destructive testing, NDT is an assessment without doing harm, stress or destroying the test object. The destruction of the test object usually makes destructive testing more costly and it is also inappropriate in many circumstances.

NDT plays a crucial role in ensuring cost effective operation, safety and reliability of plant, with resultant benefit to the community. NDT is used in a wide range of industrial areas and is used at almost any stage in the production or life cycle of many components. The mainstream applications are in aerospace, power generation, automotive, railway, petrochemical and pipeline markets. NDT of welds is one of the most used applications. It is very difficult to weld or mold a solid object that has no risk of breaking in service, so testing at manufacture and during use is often essential.

While originally NDT was applied only for safety reasons it is today widely accepted as cost saving technique in the quality assurance process. Unfortunately NDT is still not used in many areas where human life or ecology is in danger. Some may prefer to pay the lower costs of claims after an accident than applying of NDT. That is a form of unacceptable risk management. Disasters like the railway accident in Eschede Germany in 1998 is only one example, there are many others.

For implementation of NDT it is important to describe what shall be found and what to reject. A completely flawless production is almost never possible. For this reason testing specifications are indispensable. Nowadays there exists a great number of standards and acceptance regulations. They describe the limit between good and bad conditions, but also often which specific NDT method has to be used.

The reliability of an NDT Method is an essential issue. But a comparison of methods is only significant if it is referring to the same task. Each NDT method has its own set of advantages and disadvantages and, therefore, some are better suited than others for a particular application. By use of artificial flaws, the threshold of the sensitivity of a testing system has to be determined. If the the sensitivity is to low defective test objects are not always recognized. If the sensitivity is too high parts with smaller flaws are rejected which would have been of no consequence to the serviceability of the component. With statistical methods it is possible to look closer into the field of uncertainly. Methods such as Probability of Detection (POD) or the ROC-method "Relative Operating Characteristics" are examples of the statistical analysis methods. Also the aspect of human errors has to be taken into account when determining the overall reliability.

Personnel Qualification is an important aspect of non-destructive evaluation. NDT techniques rely heavily on human skill and knowledge for the correct assessment and interpretation of test results. Proper and adequate training and certification of NDT personnel is therefore a must to ensure that the capabilities of the techniques are fully exploited. There are a number of published international and regional standards covering the certification of competence of personnel. The EN 473 (Qualification and certification of NDT personnel - General Principles) was developed specifically for the European Union for which the SNT-TC-1A is the American equivalent.

The nine most common NDT Methods are shown in the main index of this encyclopedia. In order of most used, they are: Ultrasonic Testing (UT), Radiographic Testing (RT), Electromagnetic Testing (ET) in which Eddy Current Testing (ECT) is well know and Acoustic Emission (AE or AET). Besides the main NDT methods a lot of other NDT techniques are available, such as Shearography Holography, Microwave and many more and new methods are being constantly researched and developed.

NDT Applications and Limitations

NDT Method	Applications	Limitations
Liquid Penetrant	used on nonporous materials can be applied to welds, tubing, brazing, castings, billets, forgings, aluminium parts, turbine blades and disks, gears	need access to test surface defects must be surface breaking decontamination & precleaning of test surface may be needed vapour hazard very tight and shallow defects difficult to find depth of flaw not indicated
Magnetic Particle	ferromagnetic materials surface and slightly subsurface flaws can be detected can be applied to welds, tubing, bars, castings, billets, forgings, extrusions, engine components, shafts and gears	detection of flaws limited by field strength and direction needs clean and relatively smooth surface some holding fixtures required for some magnetizing techniques test piece may need demagnetization which can be difficult for some shapes and magetizations depth of flaw not indicated
Eddy Current	metals, alloys and electroconductors sorting materials surface and slightly subsurface flaws can be detected used on tubing, wire, bearings, rails, nonmetal coatings, aircraft components, turbine blades and disks, automotive transmission shafts	requires customized probe although non-contacting it requires close proximity of probe to part low penetration (typically 5mm) false indications due to uncontrolled parametric variables
Ultrasonics	metals, nonmetals and composites surface and slightly subsurface flaws can be detected can be applied to welds, tubing, joints, castings, billets, forgings, shafts, structural components, concrete, pressure vessels, aircraft and engine components used to determine thickness and mechanical properties monitoring service wear and deterioration	usually contacting, either direct or with intervening medium required (e.g. immersion testing) special probes are required for applications sensitivity limited by frequency used and some materials cause significant scattering scattering by test material structure can cause false indications not easily applied to very thin materials
Radiography Neutron	metals, nonmetals, composites and mixed materials used on pyrotechnics, resins, plastics, organic material, honeycomb structures, radioactive material, high density materials, and materials containing hydrogen	access for placing test piece between source and detectors size of neutron source housing is very large (reactors) for reasonable source strengths collimating, filtering or otherwise modifying beam is difficult radiation hazards cracks must be oriented parallel to beam for detection sensitivity decreases with increasing thickness
Radiography X-ray	metals, nonmetals, composites and mixed materials used on all shapes and forms; castings, welds, electronic assemblies, aerospace, marine and automotive components	access to both sides of test piece needed voltage, focal spot size and exposure time critical radiation hazards cracks must be oriented parallel to beam for detection sensitivity decreases with increasing thickness
Radiography Gamma	usually used on dense or thick material used on all shapes and forms; castings, welds, electronic assemblies, aerospace, marine and automotive components used where thickness or access limits X-ray generators	radiation hazards cracks must be oriented parallel to beam for detection sensitivity decreases with increasing thickness access to both sides of test piece needed not as sensitive as X-rays

The Science of Nondestructive Testing

2007-11-25T03:33:00.000-08:00

Science seems to play an every increasing role in our society. The products that we buy and produce are becoming more technical and, therefore, jobs are becoming more technical. It is important to develop a good understanding of basic science. The materials at the links below have been developed to introduce some of the important scientific principles that are used in nondestructive testing. The materials were originally designed for middle and high school students, but students of all ages may find them useful for a review of information that may have become fuzzy or been forgotten with time.

NDT is a growing, high tech, exciting career field, filled with opportunities. This page is designed to provide information about careers in NDT.

If you have an interest in starting a career in the field of nondestructive testing, take the link below to our education section. You will learn which high school classes will best prepare you for college NDT programs. You can also learn what your education options are and where you can find NDT classes and programs.

TCR to exhibit and present a paper at 4MENDT in Bahrain

2007-11-24T15:40:00.000-08:00

TCR Engineering Services and its associate companies will be exhibiting at the Fourth Middle East Nondestructive Testing Conference and Exhibition (4MENDT 2007) which is being held at the Gulf International Convention Center, Kingdom of Bahrain from December 2 to 5, 2007. This event is being organized by the Saudi Arabian Section of the American Society for Nondestructive Testing (SAS-ASNT) and the Bahrain Society of Engineers.

TCR Engineering Services (A leading ISO 17025 accredited independent materials testing laboratory) and TCR Advanced Engineering Services from India, TCR Kuwait and TCR Arabia from Saudi Arabia will be based in stall # H07 at the exhibition.

TCR will showcase its NDT services at the exhibition including Automated UT using the Time of Flight Diffraction (ToFD), Ultrasonic Testing, Magnetic Particle Testing, Helium Leak Testing, Dye Penetrant, Magnetic Flux Leakage (MFL), Positive Material Identification (PMI), In-situ Metallography (Metallographic Replication), Pre and Post Weld Heat Treatment (PWHT) and more. Senior level representatives from TCR will be on-hand at this event to answer and respond to all technical and commercial inquiries.

The theme for this conference is "Advanced NDT Solutions: Challenges and Implementations." The conference and exhibition will focus on the challenges of identifying, developing and implementing of advanced NDT technologies on the petrochemical industry facilities. The highlight of the Fourth Middle East Nondestructive Testing Conference and Exhibition will be the informative keynote address and plenary lectures by distinguished international figures in the field of NDT.

Mr. V.K. Bafna, Managing Director of TCR Engineering Services and Mr. Paresh Haribhakti will be presenting a paper at this conference on "In-Situ Metallography for Plant Health Assessment Studies and Failure Investigation."

As an NDE technique, In-situ metallography is considered important for assessing the health of the equipment, which operates under different plant conditions. The acceptance of in-situ microstructure assessment is from the fact that industry needs safe, trouble free and productive operations by adopting to predictive maintenance approach. The in-situ metallography has the strength to meet these requirements. Critical components of Oil and Petrochemical refineries, Power generation units, Fertilizers, Chemical industries are subjected to the variety of hostile environments that necessitates microstructure assessments to monitor in-service degradation.

The paper presented will allow a plant manager to understand the in-situ metallography technique in detail and assist them in conducting real-time component condition monitoring and health assessments.

Details of the event is posted at http://www.tcreng.com/newsroom/4mendt.pdf.

For more information about analytical and material testing facilities at TCR Engineering Services and her associate companies in Mumbai, Vadodara, Navi Mumbai, Saudi Arabia, Kuwait, and USA, please visit www.tcreng.com.

Certification Requirements

2007-11-24T01:49:00.000-08:00

There are a number of organizations that have produced documents that recommended or specify the minimum qualifications for certification. The following is a partial list of documents pertaining to the certification of NDT personnel in the US.
SNT-TC-1A, The American Society for Nondestructive Testing, Recommended Practice, Personnel Qualification and Certification in Nondestructive Testing.
ATA-105 Aviation Transport Association, Guidelines for Training and Qualifying Personnel in Nondestructive Testing Methods.
AIA-NAS-410 , Aerospace Industries Association, National Aerospace Standard, NAS Certification and Qualification of Nondestructive Test Personnel.
ISO 9712, International Organization for Standards, Nondestructive testing -- Qualification andcertification of personnel.
The education and work experience requirements for the various specification are common or similar. Typical requirements are summarized in the table below for qualification levels I and II. Please consult the certification documents to assure that information is correct for your situation.

NDT Jobs

2007-11-24T00:57:00.000-08:00

Nondestructive testing is most needed application in engineering. NDT includes usefull methods like oil analysing, liquid analysing, fuluorescant penetrant method, dye penetrant method, magnetic inspection, radiographic inspection, ultrasonic testing, eddy current method and leak testing. This methods takes place in different tests, some for surface tests and some for inherit tests. Aerospace, Construction, Oil Gas Chemical Pipelines, Power & Nuclear rail, Marine are some fields that needed NDT. If you are interested in NDT, dont forget there are NDT jobs all around the world. Just become an NDT Inspecter, get certificate, and make a good career.

Magnetic Particle Testing - (MT)

2007-11-20T13:59:00.000-08:00

What MT can do?
•Magnetic particle testing is an NDT method for detecting discontinuities that are primarily linearand located at or near the surfaceof ferromagneticcomponents and structures.
•Ferromagnetic metals:–Metals that are strongly attracted to a magnet and can become easily magnetized such as iron, steel, nickel, and cobalt•Onlyferromagnetic materials can be effectively inspected by MT.

Materials according to Magnetic Property
•Ferromagnetic
•Paramagnetic
–Paramagnetic materials are attractedto magnetic fields; do not retain any magnetization in the absence of an externally applied magnetic field; Al, Ca, Pt, Mg, U, O, some stainless steels, ..
•Diamagnetic
–Diamagnetic materials will be weakly repelledby a magnetic field; water, DNA, most organic compounds such as petroleum and some plastics, and many metals such as mercuryand gold
•Nonferromagnetic
–Do not react to a magnetic field; majority of metals and other nonmetallic materials

Magnetic particle inspection (MPI) is used for the detection of surface and near-surface flaws in ferromagnetic materials. A magnetic field is applied to the specimen, either locally or overall, using a permanent magnet, electromagnet, flexible cables or hand-held prods. If the material is sound, most of the magnetic flux is concentrated below the material's surface. However, if a flaw is present, such that it interacts with the magnetic field, the flux is distorted locally and 'leaks' from the surface of the specimen in the region of the flaw. Fine magnetic particles, applied to the surface of the specimen, are attracted to the area of flux leakage, creating a visible indication of the flaw.

The materials commonly used for this purpose are black iron particles and red or yellow iron oxides. In some cases, the iron particles are coated with a fluorescent material enabling them to be viewed under a UV lamp in darkened conditions.

What is Radiographic Testing (RT)

2007-11-11T10:26:00.000-08:00

Radiographic Testing (RT)

Baker Testing offers industrial non-destructive testing services (NDT) in the laboratory as well as NDT field inspection using X-ray or Isotope radiography. For industrial x-ray field work, on-site film developing is available. With Baker Testing's state-of-the-art mobile darkroom fleet, our highly-qualified technicians deliver film and issue field inspection reports prior to departure from the job site.

Using the latest industrial x-ray equipment, skilled radiographers can provide high quality images using x-ray tubes or gamma ray isotopes such as Iridium 192 and Cobalt 60. From circuit boards and medical devices, to steel fabrications up to eight inches thick, Baker Testing can examine internal structures for code disposition or analysis with resolution sensitivity up to one percent of specimen thickness on a wide variety of materials and applications.

Radiographic (RT) Certifications Certified NDT staff is available.
Baker Testing maintains ANST Level III certified technicians and NAS Level III certified technicians
ASNT-TC-1A Level III
NAS 410 Level III

Ultrasonic testing (UT) of cementitious materials

2007-10-29T01:45:00.000-07:00

Abstract
Based on Biot’s theory of wave propagation in suspensions the utilization of the
ultrasound technique for the analysis of the setting and hardening of cementitious
materials became very popular over the last years. This is well documented in
numerous papers (for instance: SAYERS & DAHLIN [1993], BOUTIN & ARNAUD
[1995] or D’ANGELO ET AL. [1996]). The Institute of Construction Materials at the
University of Stuttgart - namely Prof. Dr.-Ing. H.-W. Reinhardt - started its
comprehensive research activities in the year of 1991. The most recent result of
this project is the development of an ultrasound device. It is shown in detail that
the method, applied to mortar materials, is able to document and analyze the
setting and hardening process continuously in a way that could not be achieved by
conventional techniques such as the vicat-needle test, the penetrometer test, the
slump test, or rheologic testing methods.

Introduction
Continuous research activities over the last decade are the basis for an ultrasound technique for measurements on time-dependent material properties that has been
developed at the Institute of Construction Materials, University of Stuttgart, under
the direction of Professor Dr.-Ing. H.-W. Reinhardt. This resulted in a measuring
device to investigate the hardening process of cementitious materials in terms of
material properties and quality control as well as in a patent specification which
was passed for registration under number 198 56 259.4 [1999] at the german
patent office (Deutsches Patent- und Markenamt, München). Numerous papers

[GROSSE & REINHARDT 1994; REINHARDT & GROSSE 1996; REINHARDT ET AL.
1996; REINHARDT ET AL. 1999; GROSSE & REINHARDT 1999a] describe the
evaluation of a suitable and applicable measuring technique.
Following the requirements of construction chemicals laboratories, a measuring
system was developed. In the following paragraphs the physical background as
well as some of the specifications are described. At the end some preliminary
results are shown, giving an impression of future applications.

Motivation and physical background
Modern concrete technology faces several challenges:
• there is a great demand by the design engineer for high-strength concrete,
high-performance concrete, fibre concrete;
• contractors are demanding for highly workable concrete, self-levelling
concrete, slip formed concrete, retarded mixes;
• there is less workmanship on the construction site available;
• there is increasing quality required for durable concrete structures in an
agressive environment.

The materials producers have a basket full of admixtures and additions which are
deemed to affect the fresh or the hardened state of concrete. The user is sometimes
inclined to combine various products in order to achieve the maximum success.
However, not all mixtures lead to the expected result.
An advanced process technology needs proper control by reliable and - as much
as possible - objective measurements. A possible solution is the ultrasound
technique, where amplitude-, velocity- and frequency-variations depending on the
age of the mortar can be observed during the hardening process. The property of
cementitious materials are changing from a suspension to a solid during the
stiffening process caused by the hydratation of the cement-matrix. Biot’s theory
[BIOT 1956] describes the physical properties of this class of materials in an
adequate way, as was shown by own measurements [BOHNERT 1996]. Based on
this approach, using wave propagation theory, it became obvious that ultrasound
experiments measuring elastic waves in through-transmission are able to characterize the material during the stiffening process. Although the whole
waveform is representing the material properties, for quantitative analysis
techniques some parameters have to be extracted out of the signals recorded by a
measuring device. Parameters that are easy to determine are the velocity
(extracted by measuring the onset time of the signals knowing the travelpath of
the wave), the energy (calculating the integral sum of the wave amplitudes) and
the frequency content (using Fast-Fourier-Transform techniques). One has to keep
in mind that there are, of cause, also several other parameters that can be used.
Even though one single wave parameter could be sufficient to characterize the
material, the reliability of the method in increased by evaluating more than one.
In the following the application of the method in a certain field of interest is
shown.
Specifications for mortar measurements
The ultrasonic testing device freshmor 1 was developed at the University of
Stuttgart, Institute of Construction Materials. It enables the observation of the
setting and hardening process of mortar by means of ultrasonic throughtransmission.
Ultrasonic velocity and transmitted energy are the parameters that
are evaluated. The testing device, shown in figure 1, consists of a personal
computer with an A-D-conversion card, an ultrasonic generator, a mould with an
ultrasonic emitter/transducer pair and cables and connectors.
Since mortar contains no aggregates, the size of the mould could be reduced
significantly compared to former measurements on concrete materials
[REINHARDT ET AL. 1999]. The advantages are a better handling of the mould, a
smaller amount of material lost during the measurement, as well as less waste
causing additional costs.
The shape of the mould was designed to meet the following specifications:
• Robustness (using the mould repeatedly in laboratories),
• easy handling and fast replacement of specimen material,
• suppression of interferring waves through the walls of the container,
• mounting for piezoelectric transducers with reproducable coupling to the
tested material.
Fig. 1: Set-up for the mortar experiments showing the mould (rubber foam and PMMA-walls) and
the transducers.
An emitter-receiver pair of broadband conical transducers were chosen, which are
sensitive in a frequency range of 20 to 300 kHz. The conical shape of the
transducers enables the possibility of point-to-point measurements.
The signals measured during the stiffening process are recorded by an A/Dconcersion
device consisting of a fast A/D-transientrecorder PC-card controlled
by an IBM-compatible PC. On the emitting side, the signals are produced by an
US-generator via the conical transducer in time intervalls defined by the user.
Apart from the hardware, a lot of efford was made to bring the software in a userfriendly
laboratory-suited state. The software consists of three parts including the
control and monitor software used during the data acquisition, the extraction of
wave parameters used for the material characterization and the data analysis
software.
A list of software features was widely discussed with our research partners:
• Data acquisition and parameter extraction during a routine test as well as a
step-by-step parameter extraction in certain special applications (unknown
products or product components),
• waveform acquisition and recording with adequate amplitude resolution,
• automatic onset time picking with the highest reliability,
• flexible measurement intervals according to different periods of interest for
different admixtures,
• automatic processing of the signals including velocity and energy evaluation
during and after the test,
• extraction of additional material relevant parameters such as initial and final
setting time of the mortar.
Under the auspices of Professor Dr.-Ing. H.-W. Reinhardt the authors worked
together to meet all requirements including hardware and software as described in
the following.
Experimental setup and first results
Not all steps of the development can be described in detail. It was an iterative
process of finding a suitable shape for the mould. The final container has two
walls of PMMA and a U-shaped rubber foam. According to the description in the
patent specification [1999].
Some effort had to be done to fulfill all requirements regarding the software. An
important feature was the implementation of a dynamic software amplifier, which
was realized to enhance the amplitude resolution. The ultrasound waves travelling
through the mortar are highly attenuated in the beginning right after mixing. The
signal in the hardenend state, is however several decades higher in amplitude.
This significant increase in amplitude is a problem when using a device with 12-
bit hardware amplitude resolution without a gain ranging method.
To determine automatically the onset times of the compressional waves and
therefore the velocities with highest reliability, a special picking algorithm must
be used. Well-known algorithms using the crossover of signals above a given
threshold are not applicable in this case, because, for the given data, they were
tested with errors of over 100 percent in relation to the onset times. We have
developed a software called FreshCon which uses a combined energy-frequency
approach solving this problem. The algorithm was very well tested in numerous
applications and gives reasonable results even if the signal-to-noise ratio is low.
An example is shown in figure 2. A description of the software can be found in
GROSSE & REINHARDT [1999b].
Fig. 2: Example of an unfiltered US-signal in FreshCon using the semiautomatic picking mode.
For the final data analysis we used a comercially available software tool called
Origin (from MicroCal), which we have considerably modified with import
filters, templates, and macros. To give an impression of it‘s capabilities, figure 3
shows a typical sheet of data evaluation. The solid line is the calculated
compressional wave velocity depending on the age of mortar and the dotted line
shows the energy.
Fig. 3: Data analysis using the FreshMor-templates in the Origin-software. The straight lines at 2 h
39 min and 5 h 30 min give the values of the initial and final setting time of the material.
The operator is able to give a title for the sheet according to the tested material or
the date and time. In addition he may extract automatically the values of the initial
and final setting time of the mortar marked by two straight lines at certain ages.
Import and export of data as well as the print and documentation options are using
the latest MS-Windows standards including OLE-features for test documentation
with standard text processors.
First results
The first measurements have been conducted to test the reproducability of the data
curves. For these experiments, mortar mixtures consisting of a standard sand,
standard grain-size (∅ 0-2 mm) and water-to-cement ratio (no admixtures) have
been chosen. Three identical mixtures were tested – one after another. For the
mixing process itself we stood to the standard procedure for prisms according to
DIN EN 196-1, including a compaction time of two minutes. During this vibration
of approximately 0.7 mm horizontal amplitude, the mould was slowly be filled –
we learned that the devaporation of the material is important for proper and reliable results. Due to the time necessary for compaction and connection to the
US-device, the first data can be recorded after approximately 10 minutes. The
graphs in figure 4 demonstrate that the reproducability of the velocity and the
energy data are reasonable. Choosing standard settings for these test measurements,
the repetitive data acquisition interval was set to 10 minutes. For all
experiments described in this paper, the waveforms were averaged of five single
measurements, that is why every data point of the velocity and energy curves
represents five recordings. This procedure enhences the reproducability
condiderably. The variations at the end of the curves at later ages result from the
lower resolution according to shorter traveltimes in the hardenend material.

Fig. 4: Reproducibility test evaluate velocity and energy curves of three mortar mixtures of the same
kind.

Some preliminary results from experiments using the same mixture with different admixtures are shown as an example in figure 5. The curves represent the bandwith of tested materials showing the behaviour of the velocity as a function of the hardening age. Compared to the material without admixtures the velocity rises earlier when an accelerator is added to the mortar, and later when an air entrainer is added. The curve for the retarder starts at a higher velocity level due to the stabilizer containing the retarding additive. These test results should give an impression about the capabilities of this technique to investigate and classify a hardening material. Special mixtures as well as newly designed admixtures are able to be characterized in a new andpromising way.Fig. 5: Velocity (sligthly smoothed) versus age of mortar for 4 different mixtures.

Conclusions and acknowledgements
The ultrasonic device presented in this article is able to extract automatically
certain parameters of US waves recorded continously during the setting and
hardening of mortar materials. The resulting curves describe the material
behaviour and are related closely to the hydration process of the mortar. These
curves are linked to the elastic properties and give a comprehensive picture of the
stiffening process in a way that was not accessible before. Future applications in
industrial laboratories have to show, what kind of benefits are brought up by
recording the material properties of suspensions during hardening. Anyway, it is
obvious that this technique gives a clearer and more detailled insight than the
standard procedures that are measuring only one single parameter at certain
stiffness stages.
It is expected that the industrial use of this method will feedback in a further
improvement of the technique examining mortar materials. On the basis of these
experiences, the existing apparatus for concrete investigations will also be improved to enable measurements in-situ. It should be concluded, that apart from
this, the US-device will be modified for measurements on different other materials
such as polymers, ceramics or even starch.
The presented work is the result of a scientific project where many scientist and
students took part. The authors like to thank Jochen Fischer [1991], Nicole
Windisch [1996], Iris Kolb [1997] and Jens Bohnert [1996] for their
contributions. A very special thank-you is expressed by the authors to Prof. Dr.-
Ing. H.-W. Reinhardt for the initiation of this project, innumerable discussions
and his proficient and detailed help in all kind of problems. Without his efforts
and inertia, this research would not have been possible.

Quality Inspector

2007-09-17T00:24:00.000-07:00

Requirements

First and last off inspection of production units (including in-process checks).
NDT testing (desirable).
CMM programmer or operator (advantageous).
IT skills (necessary).
A clear commitment to high quality standards and attention to detail.
Ability to promote quality policy within the business.
Manufacturing background with proven track record.
To develop new and existing methods of measurement wherever appropriate.
Maintain calibration schedule.
Support the production supervisor in meeting production schedule requirements.
To develop confidence in operators to discuss quality matters.
Teamwork skills, problem solving.
To promote continual improvements.
To train in other inspection functions to fully support the quality structure.
Improve the quality of information to identify root cause and corrective action.
Health & Safety awareness.
Ability to read engineering drawings.

Programme Managers

2007-09-17T00:19:00.000-07:00

Responsibilities including:

personal delivery of training courses and invigilation
management and leadership of a team, staff motivation and development
planning, management, resourcing and scheduling of programme delivery
development of updated high quality materials and methods of delivery
business development and marketing
pricing, budgeting and profitability
liaison with overseas subsidiaries on delivery and business development
strategic contribution to the Training & Exams management team.

Offshore NDT Information

2007-09-11T01:26:00.000-07:00

* The oil and gas industry, with its numerous offshore platforms and extensive network of pipelines, is a significant user of NDT technologies necessary to assess the structural integrity of these installations. Underwater testing of welds in pielines is regularly performed for crack detection using visual, magnetic, electromagnetic, ultrasonic or radiographic techniques.

Qualified welder (SMAW,SAW)

2007-09-11T01:18:00.000-07:00

*Piping and structural welding.

Welding inspector

2007-09-11T01:16:00.000-07:00

*Welder qualification inspection for all process.Responsible for visual inspection, film interpretation, mechanical testing, nondestructive testing and reporting.
*Performed duties on projects throughout Worldwide for all types of testing and fabrication works.Inspecting welder training and qualification testing, process piping, storage tank, boiler & pressure vessel, structurl welding per international code/standard.

Assistant manager

2007-09-11T01:14:00.000-07:00

Assistant managerSenior welding inspector / NDT inspector NDT Level IIPersonnel for testing programs

*Performed NDT inspections, radiographic film interpretation and reporting at project sites.Supervised welder and inspector.
*Conducted welder testing and qualifications. Participated in marketing and preparation of proposals.

Deputy manager (NDT/welding Q.C.)

2007-09-11T01:13:00.000-07:00

*Responsible for NDT operations and welder testing and training.
*Conducted welder and pipe filter qualification tests and welding procedure qualifications.Performed radiographic film interpretation, reporting and UT, MT, PT inspector and nondestructive testing.
*Assigned to marketing and preparation quotations.

Managing director

2007-09-11T01:08:00.000-07:00

*Manage all NDT operations and welding inspectors,

*Responsible for management of Welder Testing & Training programs, business development and marketing, budgeting and bidding.
*Provision of Welding Consultance & Designs (WPS, PQR,?WQT) and all procedure preparations.
*Conducting the WPS, PQR, WQT Qualification test for refinery, petrochemical plant, IPP, paper mill and etc..
*Review & approval of WPS, PQR, & WQT of various projects.
*Approval of WPS, PQR, WQT certificate of offshore works.
-Including negotiation with clients, preparation of NDT and inspections procedure and welding procedure as well as conducting the testing per client specifications and/or per international code standard.

Nondestructive exam

2007-09-01T05:55:00.000-07:00

Examinations

The South West School of NDT is an “Authorised Qualifying Body” for central certification examinations under the PCN scheme, administered by the British Institute of NDT. This is in satisfaction of EN 473 and ISO 9712. Additionally, the school routinely hosts examinations in satisfaction of employer-based schemes such as SNT-TC-IA, NAS 410 and EN4179.

Whilst central certification examinations are held at the school’s examination centre in Cardiff, NDT level 3 examination staff travel to national and international venues to administer employer-based examinations on behalf of a variety of clients.

Working in close collaboration with Ruane and T P O’Neill, the school can offer examinations in all major NDT disciplines and Industry sectors. It also specialised in arranging examinations in allied disciplines in such areas as Mechanical Testing, Heat Treatment, Acid Etch Inspection, Hardness and Conductivity, Anodic Flaw Detection, Composite Materials Inspection and Bond Testing. These are normally conducted under a structure similar to that for the mainstream methods and can be expended to include almost any technical discipline.

NDT Applications and Equipments

2007-08-31T10:18:00.000-07:00

Inspection Technologies provides technology-driven inspection solutions (Non Destructive Testing [NDT] products and services) that deliver productivity, quality and safety. NDI design, manufacture and service ultrasonic, remote visual,radiographic (X-ray) and eddy current equipment and systems, and offer specialized solutions that will help you improve productivity in your applications in the aerospace, power generation, oil & gas, automotive or metals Industries.

Ultrasonic Testing
Flaw Detectors
Transducers
Thickness Gages
Ultrasonic Scanning Systems
Installed Sensors
Ultrasonic Instrumentations
Hardness Testing
Testing Machines and Integrated Systems

Remote Visual Inspection
Video Borescopes
Rigid Borescopes
Flexible Fiberscopes
Robotic Crawlers
Pan-Tilt-Zoom Cameras
Light Sources
Inspection Services
Equipment Rental

Radiography (X-ray)
Generators
Film Processors
Film
Computed Radiography
Digital Radiography
Analytical X-ray
Testing Machines and Integrated Systems

Eddy Current Testing
Instruments
Probes
Testing Machines and Integrated Systems

Others Products and Services
Software Solutions
Metrology
NDT Training
Equipment Services

What is CP-189

2007-08-30T05:10:00.000-07:00

CP-189 is a standart. This standart establishes the minimum requirements for the qualification and certification of NDT personnel.
This standart details the minimun trainingi education, and experience requirements for NDT personnel and provides criteria for documenting qualifications ant certification.
This standartrequires the employer to establish a peocedure for the cerfication of NDT personnel.
This standart requires that the employer incorporate any unique or additional requirements in the certification procedure.
Levels of Qualification;

trainee
NDT level I
NDT level II
NDT level III
NDT Instructor

What Is SNT-TC-1A

2007-08-30T04:19:00.000-07:00

SNT-TC-1A is a recommended practice..
It is recognized that the effectiveness of NDT aplications depends upon the capabilities of the personnel who are responsible for perform NDT. This recommended practice has been prepared to establish guidelines for the qualification and certification of NDT personnel whose specific jobs require appropriate knowledege of thecnical principles underlying the NDT they perform, witness, monitor or evaluate.
NDT Methods, Qualification and certification of NDT personnel in acorddance with this Recommended Practice is aplicable to each of the following methods:

Acoustic Emission Testing
Electromagnetic Testing
Laser Testing Methods
Leak Testing
Liquid Penetrant Testing
Magnetic Particle Testing
Neutron Radiographic Testing
Radiographic Testing
Thermal/Infrared Testing
Ultrasonic Testing
Vibration Analysis
Visual Testing

Ultrasonic Testing videos

2007-08-28T23:22:00.000-07:00

Signal propagation on a Printed Circuit Board

Magnetohydrodynamics Coupled Simulation of an arc in a Low...

Convergence of an iterative solver

Finite Volumes with Adaptive Meshes

Metamaterials - Split ring loaded waveguide

Hyperthermia Treatment

Current density inside the body induced by an electric blank

Nondestructive testing of materials

Induced current density inside the body

Thermal power denstity in the human head

Electric Field inside the Human Head.

Traveling Wave Tube

Electrons in a Pierce-Gun

Nondestructive Testing videos

2007-08-28T22:45:00.000-07:00

1		Signal propagation on a Printed Circuit Board From: TEMFTUD
2		Magnetohydrodynamics From: TEMFTUD
3		Convergence of an iterative solver From: TEMFTUD
4		Finite Volumes with Adaptive Meshes From: TEMFTUD
5		Metamaterials - Split ring loaded waveguide From: TEMFTUD
6		Hyperthermia Treatment From: TEMFTUD
7		Current density inside the body induced by an From: TEMFTUD
8		Nondestructive testing of materials From: TEMFTUD
9		Induced current density inside the body From: TEMFTUD
10		Thermal power denstity in the human head From: TEMFTUD
11		Electric Field inside the Human Head. From: TEMFTUD
12		Traveling Wave Tube From: TEMFTUD
13		Electrons in a Pierce-Gun From: TEMFTUD

NDT Method Summary Sheet

2007-08-27T14:35:00.000-07:00

No single NDT method will work for all flaw detection or measurement applications. Each of the methods has advantages and disadvantages when compared to other methods. The table below summarizes the scientific principles, common uses and the advantages and disadvantages for some of the most often used NDT methods.

Penetrant Testing	Magnetic Particle Testing	Ultrasonic Testing	Eddy Current Testing	Radiographic Testing

Scientific Principles
Penetrant solution is applied to the surface of a precleaned component. The liquid is pulled into surface-breaking defects by capillary action. Excess penetrant material is carefully cleaned from the surface. A developer is applied to pull the trapped penetrant back to the surface where it is spread out and forms an indication. The indication is much easier to see than the actual defect.	A magnetic field is established in a component made from ferromagnetic material. The magnetic lines of force travel through the material, and exit and reenter the material at the poles. Defects such as crack or voids cannot support as much flux, and force some of the flux outside of the part. Magnetic particles distributed over the component will be attracted to areas of flux leakage and produce a visible indication.	High frequency sound waves are sent into a material by use of a transducer. The sound waves travel through the material and are received by the same transducer or a second transducer. The amount of energy transmitted or received and the time the energy is received are analyzed to determine the presence of flaws. Changes in material thickness, and changes in material properties can also be measured.	Alternating electrical current is passed through a coil producing a magnetic field. When the coil is placed near a conductive material, the changing magnetic field induces current flow in the material. These currents travel in closed loops and are called eddy currents. Eddy currents produce their own magnetic field that can be measured and used to find flaws and characterize conductivity, permeability, and dimensional features.	X-rays are used to produce images of objects using film or other detector that is sensitive to radiation. The test object is placed between the radiation source and detector. The thickness and the density of the material that X-rays must penetrate affects the amount of radiation reaching the detector. This variation in radiation produces an image on the detector that often shows internal features of the test object.
Main Uses
Used to locate cracks, porosity, and other defects that break the surface of a material and have enough volume to trap and hold the penetrant material. Liquid penetrant testing is used to inspect large areas very efficiently and will work on most nonporous materials.	Used to inspect ferromagnetic materials (those that can be magnetized) for defects that result in a transition in the magnetic permeability of a material. Magnetic particle inspection can detect surface and near surface defects.	Used to locate surface and subsurface defects in many materials including metals, plastics, and wood. Ultrasonic inspection is also used to measure the thickness of materials and otherwise characterize properties of material based on sound velocity and attenuation measurements.	Used to detect surface and near-surface flaws in conductive materials, such as the metals. Eddy current inspection is also used to sort materials based on electrical conductivity and magnetic permeability, and measures the thickness of thin sheets of metal and nonconductive coatings such as paint.	Used to inspect almost any material for surface and subsurface defects. X-rays can also be used to locates and measures internal features, confirm the location of hidden parts in an assembly, and to measure thickness of materials.
Main Advantages
Large surface areas or large volumes of parts/materials can be inspected rapidly and at low cost. Parts with complex geometry are routinely inspected. Indications are produced directly on surface of the part providing a visual image of the discontinuity. Equipment investment is minimal.	Large surface areas of complex parts can be inspected rapidly. Can detect surface and subsurface flaws. Surface preparation is less critical than it is in penetrant inspection. Magnetic particle indications are produced directly on the surface of the part and form an image of the discontinuity. Equipment costs are relatively low.	Depth of penetration for flaw detection or measurement is superior to other methods. Only single sided access is required. Provides distance information. Minimum part preparation is required. Method can be used for much more than just flaw detection.	Detects surface and near surface defects. Test probe does not need to contact the part. Method can be used for more than flaw detection. Minimum part preparation is required.	Can be used to inspect virtually all materials. Detects surface and subsurface defects. Ability to inspect complex shapes and multi-layered structures without disassembly. Minimum part preparation is required.
Disadvantages
Detects only surface breaking defects. Surface preparation is critical as contaminants can mask defects. Requires a relatively smooth and nonporous surface. Post cleaning is necessary to remove chemicals. Requires multiple operations under controlled conditions. Chemical handling precautions are necessary (toxicity, fire, waste).	Only ferromagnetic materials can be inspected. Proper alignment of magnetic field and defect is critical. Large currents are needed for very large parts. Requires relatively smooth surface. Paint or other nonmagnetic coverings adversely affect sensitivity. Demagnetization and post cleaning is usually necessary.	Surface must be accessible to probe and couplant. Skill and training required is more extensive than other technique. Surface finish and roughness can interfere with inspection. Thin parts may be difficult to inspect. Linear defects oriented parallel to the sound beam can go undetected. Reference standards are often needed.	Only conductive materials can be inspected. Ferromagnetic materials require special treatment to address magnetic permeability. Depth of penetration is limited. Flaws that lie parallel to the inspection probe coil winding direction can go undetected. Skill and training required is more extensive than other techniques. Surface finish and roughness may interfere. Reference standards are needed for setup.	Extensive operator training and skill required. Access to both sides of the structure is usually required. Orientation of the radiation beam to non-volumetric defects is critical. Field inspection of thick section can be time consuming. Relatively expensive equipment investment is required. Possible radiation hazard for personnel.
Penetrant Testing	Magnetic Particle Testing	Ultrasonic Testing	Eddy Current Testing	Radiographic Testing

Methods and techniques of NDT

2007-08-27T14:07:00.000-07:00

NDT is divided into various methods of nondestructive testing, each based on a particular scientific principle. These methods may be further subdivided into various techniques. The various methods and techniques, due to their particular natures, may lend themselves especially well to certain applications and be of little or no value at all in other applications. Therefore choosing the right method and technique is an important part of the performance of NDT.

An example of Ultrasonic Testing (UT) on blade roots of a V2500 IAE aircraft engine.

Step 1: The UT probe is placed on the root of the blades to be inspected with the help of a special borescope tool (video probe).
Step 2: Instrument settings are input.
Step 3: The probe is scanned over the blade root. In this case, an indication (peak in the data) through the red line (or gate) indicates a good blade; an indication to the left of that range indicates a crack.

Liquid penetrant testing (PT or LPI)

1. Section of material with a surface-breaking crack that is not visible to the naked eye.
2. Penetrant is applied to the surface.
3. Excess penetrant is removed.
4. Developer is applied, rendering the crack visible.

Liquid penetrant inspection is a widely applied and low-cost inspection method used to locate surface-breaking defects in all non-porous materials (metals, plastics, or ceramics). Penetrant may be applied to all non-ferrous materials, but for inspection of ferrous components magnetic particle inspection is preferred for its subsurface detection capability. LPI is used to detect casting and forging defects, cracks, and leaks in new products, and fatigue cracks on in-service components.

Principles

LPI is based upon capillary action, where low surface tension fluid penetrates into clean and dry surface-breaking discontinuities. Penetrant may be applied to the test component by dipping, spraying, or brushing. After adequate penetration time has been allowed, the excess penetrant is removed, and a developer is applied. The developer helps to draw penetrant out of the flaw where a visible indication becomes visible to the inspector. Inspection is performed under ultraviolet or white light, depending upon the type of dye used - fluorescent or nonfluorescent (visible).

Materials

Penetrants are classified into sensitivity levels. Visible penetrants are typically red in color, and represent the lowest sensitivity. Fluorescent penetrants contain two or more dyes that fluoresce when excited by ultraviolet (UV-A) radiation (also known as black light). Since FPI is performed in a darkened environment, and the excited dyes emit brilliant yellow-green light that contrasts strongly against the dark background, this material is more sensitive to small defects.

When selecting a sensitivity level one must consider many factors, including the environment under which the test will be performed, the surface finish of the specimen, and the size of defects sought. One must also assure that the test chemicals are compatible with the sample so that the examination will not cause permanent staining, or degradation. This technique can be quite portable, because in its simplest form the inspection requires only 3 aerosol spray cans, some paper towels, and adequate visible light. Stationary systems with dedicated application, wash, and development stations, are more costly and complicated, but result in better sensitivity and higher sample through-put.

Inspection Steps

Below are the main steps of Liquid Penetrant Inspection:

1. Pre-cleaning:

The test surface is cleaned to remove any dirt, paint, oil, grease or any loose scale that could either keep penetrant out of a defect, or cause irrelevant or false indications. Cleaning methods may include solvents, alkaline cleaning steps, vapor degreasing, or media blasting. The end goal of this step is a clean surface where any defects present are open to the surface, dry, and free of contamination.

2. Application of Penetrant:

The penetrant is then applied to the surface of the item being tested. The penetrant is allowed time to soak into any flaws (generally 10 to 30 minutes). The soak time mainly depends upon the material being testing and the size of flaws sought. As expected, smaller flaws require a longer penetration time. Due to their incompatible nature one must be careful not to apply visible red dye penetrant to a sample that may later be inspected with fluorescent penetrant.

3. Excess Penetrant Removal:

The excess penetrant is then removed from the surface. Removal method is controlled by the type of penetrant used. Water-washable, solvent-removable, lipophilic post-emulsifiable, or hydrophilic post-emulsifiable are the common choices. Emulsifiers represent the highest sensitivity level, and chemically interact with the oily penetrant to make it removable with a water spray. When using solvent remover and lint-free cloth it is important to not spray the solvent on the test surface directly, because this can the remove the penetrant from the flaws. This process must be performed under controlled conditions so that all penetrant on the surface is removed (background noise), but penetrant trapped in real defects remains in place.

4. Application of Developer:

After excess penetrant has been removed a white developer is applied to the sample. Several developer types are available, including: non-aqueous wet developer, dry powder, water suspendible, and water soluble. Choice of developer is governed by penetrant compatibility (one can't use water-soluble or suspedible developer with water-washable penetrant), and by inspection conditions. When using non-aqueous wet developer (NAWD) or dry powder the sample must be dried prior to application, while soluble and suspendible developers are applied with the part still wet from the previous step. NAWD is commercially available in aerosol spray cans, and may employ acetone, isopropyl alcohol, or a propellant that is a combination of the two. Developer should form a thin, even coating on the surface.

The developer draws penetrant from defects out onto the surface to form a visible indication, a process similar to the action of blotting paper. Any colored stains indicate the positions and types of defects on the surface under inspection.

5. Inspection:

The inspector will use visible light with adequate intensity (100 foot-candles is typical) for visible dye penetrant. Ultraviolet (UV-A) radiation of adequate intensity (1,000 micro-watts per centimeter squared is common), along with low ambient light levels (less than 2 foot-candles) for fluorescent penetrant examinations. Inspection of the test surface should take place after a 10 minute development time. This time delay allows the blotting action to occur. The inspector may observe the sample for indication formation when using visible dye, but this should not be done when using fluorescent penetrant. Also of concern, if one waits too long after development the indications may "bleed out" such that interpretation is hindered.

6. Post Cleaning:

The test surface is often cleaned after inspection and recording of defects (if found), especially if post-inspection coating processes are scheduled.

Features

The flaws are more visible, because:
- The defect indication has a high visual contrast (e.g. red dye against a white developer background, or a bright fluorescent indication against a dark background).
- The developer draws the penetrant out of the flaw over a wider area than the real flaw, so it looks wider.
Limited training is required for the operator — although experience is quite valuable.
Low testing costs.
Proper cleaning is necessary to assure that surface contaminants have been removed and any defects present are clean and dry. Some cleaning methods have been shown to be detrimental to test sensitivity, so acid etching to remove metal smearing and re-open the defect may be necessary.
Penetrant dyes stain cloth, skin and other porous surfaces brought into contact. One should verify compatibility on the test material, especially when considering the testing of plastic components.
Further information on inspection steps may be found in industry standards (e.g. the American Welding Society, American Society for Testing and Materials, the British Standards Institute, and the Society for Automotive Engineers).

Radiographic testing (RT)

Radiographic Testing (RT), or industrial radiography, is a nondestructive testing (NDT) method of inspecting materials for hidden flaws by using the ability of short wavelength electromagnetic radiation (high energy photons) to penetrate various materials.

Either an X-ray machine or a radioactive source (Ir-192, Co-60, or in rare cases Cs-137) can be used as a source of photons. Neutron radiographic testing (NR) is a variant of radiographic testing which uses neutrons instead of photons to penetrate materials. This can see very different things from X-rays, because neutrons can pass with ease through lead and steel but are stopped by plastics, water and oils.

Since the amount of radiation emerging from the opposite side of the material can be detected and measured, variations in this amount (or intensity) of radiation are used to determine thickness or composition of material. Penetrating radiations are those restricted to that part of the electromagnetic spectrum of wavelength less than about 10 nanometres.

Inspection of welds

The beam of radiation must be directed to the middle of the section under examination and must be normal to the material surface at that point, except in special techniques where known defects are best revealed by a different alignment of the beam. The length of weld under examination for each exposure shall be such that the thickness of the material at the diagnostic extremities, measured in the direction of the incident beam, does not exceed the actual thickness at that point by more than 6%. The specimen to be inspected is placed between the source of radiation and the detecting device, usually the film in a light tight holder or cassette, and the radiation is allowed to penetrate the part for the required length of time to be adequately recorded.

The result is a two-dimensional projection of the part onto the film, producing a latent image of varying densities according to the amount of radiation reaching each area. It is known as a radiograph, as distinct from a photograph produced by light. Because film is cumulative in its response (the exposure increasing as it absorbs more radiation), relatively weak radiation can be detected by prolonging the exposure until the film can record an image that will be visible after development. The radiograph is examined as a negative, without printing as a positive as in photography. This is because, in printing, some of the detail is always lost and no useful purpose is served.

Before commencing a radiographic examination, it is always advisable to examine the component with one's own eyes, to eliminate any possible external defects. If the surface of a weld is too irregular, it may be desirable to grind it to obtain a smooth finish, but this is likely to be limited to those cases in which the surface irregularities (which will be visible on the radiograph) may make detecting internal defects difficult.

After this visual examination, the operator will have a clear idea of the possibilities of access to the two faces of the weld, which is important both for the setting up of the equipment and for the choice of the most appropriate technique.

Defects such as delaminations and planar cracks are difficult to detect using radiography, which is why penetrants are often used to enhance the contrast in the detection of such defects. Penetrants used include silver nitrate, zinc iodide, chloroform and diiodomethane. Choice of the penetrant is determined by the ease with which it can penetrate the cracks and also with which it can be removed. Diiodomethane has the advantages of high opacity, ease of penetration, and ease of removal because it evaporates relatively quickly. However, it can cause skin burns.

Ultrasonic testing (UT)

In ultrasonic testing, very short ultrasonic pulse-waves with center frequencies ranging from 0.1-15 MHz and occasionally up to 50 MHz are launched into materials to detect internal flaws or to characterize materials. It is also commonly used to determine the thickness of the test object - monitoring pipework corrosion being a good example.

Ultrasonic Inspection is often performed on steel and other metals and alloys, though it can be used on concrete and other materials such as composites. It is a form of non-destructive testing used in many industries including aerospace, automotive and other transportation sectors.

How it works

In ultrasonic testing, a transducer connected to a diagnostic machine is passed over the object being inspected. In reflection (or pulse-echo) mode, the transducer sends pulsed waves through a couplant (such as water or oil) on the surface of the object, and receives the "sound" reflected back to the device. Reflected ultrasound comes from an interface - such as the back wall of the object or from an imperfection. The screen on the calibrated diagnostic machine displays these results in the form of a signal with an amplitude representing the intensity of the reflection and the distance taken for the reflection to return to the transducer. In attenuation (or through-transmission) mode, a transmitter sends ultrasound through one surface, and a separate receiver detects the amount that has reached it on another surface after travelling through the medium. Imperfections or other conditions in the space between the transmitter and receiver reduce the amount of sound transmitted thus indicating their presence.

Non-destructive testing of a swing shaft showing spline cracking

Advantages

Superior penetrating power, which allows the detection of flaws deep in the part.
High sensitivity, permitting the detection of extremely small flaws.
Only one surface need to be accessible.
Greater accuracy than other nondestructive methods in determining the depth of internal flaws and the thickness of parts with parallel surfaces.
Some capability of estimating the size, orientation, shape and nature of defects.
Nonhazardous to operations or to nearby personnel and has no effect on equipment and materials in the vicinity.
Capable of portable or highly automated operation.

Disadvantages

Manual operation requires careful attention by experienced technicians
Extensive technical knowledge is required for the development of inspection procedures.
Parts that are rough, irregular in shape, very small or thin, or not homogeneous are difficult to inspect.
Surface must be prepared by cleaning and removing loose scale, paint, etc. (UT can often be used successfully through paint that is properly bonded to a surface.)
Couplants are needed to provide effective transfer of ultrasonic wave energy between transducers and parts being inspected unless a non-contact technique is used. Non-contact techniques include Laser and Electro Magnetic Acoustic Transducers (EMAT).
Inspected items must be water resistant, when using water based couplants that do not contain rust inhibitors.

Visual and optical testing (VT)
Electromagnetic testing (ET)

Electromagnetic Testing (ET), as a form of nondestructive testing, is the process of inducing electric currents or magnetic fields or both inside a test object and observing the electromagnetic response. If the test is set up properly, a defect inside the test object creates a measurable response.

The term "Electromagnetic Testing" is often intended to mean simply Eddy-Current Testing (ECT). However with an expanding number of electromagnetic and magnetic test methods, "Electromagnetic Testing" is more often used to mean the whole class of electromagnetic test methods, of which Eddy-Current Testing is just one.

Acoustic emission testing (AE)

Acoustic Emission (AE) is a naturally occurring phenomenon whereby external stimuli such as mechanical loading generate sources of elastic waves. AE occurs when a small surface displacement of a material is produced. This occurs due to stress waves generated when there is a rapid release of energy in a material, or on its surface. The wave generated by the source of the AE, or, of practical interest, in methods used to stimulate and capture AE in a controlled fashion for study and/or use in inspection, quality control, system feedback, process monitoring and others.

Acoustic emission testing is used as a type of nondestructive testing technology. It is in the ultrasonic regime, typically within the range between 100 kHz and 1 MHz (although this range is not absolute). Acoustic emissions can be monitored and detected in frequency ranges under 1 kHz and have been reported at frequencies up to 100 MHz. Rapid stress-releasing events generate a spectrum of stress waves starting at 0 Hz and typically falling off at several MHz, but one strength of the technique is that background noise, particularly airborne, falls off more quickly, so the signal-to-noise ratio reaches an optimum value around the conventional frequency range.

A commonly accepted definition for AE is a transient elastic waves within a material due to localized stress release. Hence, a source which generates one AE event is the phenomenon which releases elastic energy into the material, which then propagates as an elastic wave. AE events can also come quite rapidly when materials begin to fail, in which case AE activity rates are studied as opposed to individual events. AE events that are commonly studied include the extension of a fatigue crack, or fiber breakage in a composite material among material failure processes. AE is related to an irreversible release of energy, and can be generated from sources not involving material failure including friction, cavitation and impact.

Transducers are attached to the material to detect these waves. Most of these sensors are in the frequency range of 20 kHz to 650 kHz. Some geophysical studies with AE use much lower frequency sensors, while sensors in the MHz range are also available commercially.

AE tools do not actively produce waves (or "insonify") as in conventional ultrasonics. Rather, they passively detect emissions from acoustic sources.

AEs from within a material are monitored to locate and/or define their source event. AE is even more commonly used to correlate when activity occurred with the level of stimuli or length of time before something occurred, such as determining the onset of cracking, documenting the failure of a part during unattended monitoring or the level of reoccurrence of AE during multiple load cycles. The last method listed is the basis for many safety inspection methods utilizing AE. Parts inspected with AE can remain in service.

Infrared and thermal testing (IR)
Laser testing
Leak testing (LT)

General Introduction to NDT Presentation (powerpoint)

2007-08-27T13:53:00.000-07:00

General Introduction to NDT Presentation

Nondestructive testing is a career field that is relatively obscure in the minds of the general public. The name seems totally self-explanatory, but most NDT professionals can relate to the experience of trying to explain what nondestructive testing means to family members, friends and acquaintances. Most students when considering career options are completely unaware that NDT is a very exciting and rewarding career field.

To help remedy the situation, an "Introduction to Nondestructive Testing" presentation has been prepared. The presentation is intended to be used by NDT professionals when they have the opportunity to address middle and high school classes, professional societies, or any other group willing to listen. The presentation can be downloaded and modified to meet the specific needs of the presenter.

All rights are reserved by the authors but the material may be freely used by individuals and organizations for general educational purposes. The materials may not be sold commercially, or used in commercial products or services. The presentation was prepared using PowerPoint 2002, so please note that some of the animation features may not function properly when used with a earlier version of the program.

Download Introduction to NDT Presentation ( 4.7 MB, ppt)

What is Non-Destructive Testing (NDT)?

2007-08-27T13:34:00.000-07:00

Nondestructive testing (NDT), also called nondestructive evaluation (NDE) and nondestructive inspection (NDI), is testing that does not destroy the test object. NDE is vital for constructing and maintaining all types of components and structures. To detect different defects such as cracking and corrosion, there are different methods of testing available, such as X-ray (where cracks show up on the film) and ultrasound (where cracks show up as an echo blip on the screen). This article is aimed mainly at industrial NDT, but many of the methods described here can be used to test the human body. In fact methods from the medical field have often been adapted for industrial use, as was the case with Phased array ultrasonics and Computed radiography.

While destructive testing usually provides a more reliable assessment of the state of the test object, destruction of the test object usually makes this type of test more costly to the test object's owner than nondestructive testing. Destructive testing is also inappropriate in many circumstances, such as forensic investigation. That there is a tradeoff between the cost of the test and its reliability favors a strategy in which most test objects are inspected nondestructively; destructive testing is performed on a sampling of test objects that is drawn randomly for the purpose of characterizing the testing reliability of the nondestructive test.

Glossary Of Terms For Radiographic Testing

2007-08-14T14:07:00.000-07:00

Glossary of Terms for Radiographic Testing

Absorb dose:
The amount of energy imparted by ionizing radiation per unit mass of irradiated matter. Indicated by "rad"; 1 rad = 0.01j/kg. SI units is "gray"; 1 gray = 1 J/kg.

Absorb dose rate:
the absorbed dose per unit of time; rad/s or as SI unit gray/s.

Absorption:
The process whereby the incident particles or photons of radiation are reduced in a number or energy as they pass through matter, i.e. the energy of the radiation beam is attenuated. Note that the total attenuation is the sum of the components due to photoelectric absorption, Rayleigh scattering, Compton scattering and pair production.

Accelerating potential:
The difference in electric potential between the cathode and anode in an X-ray tube through which a charged particle is accelerated, usually spezified in units of kV or MV.

Activity:
The number of nuclear transitions occurring in a given quantity of radioactive material per unit of time. For example one disintegration/second is a becquerel (Bq), which has replaced curie (Ci) as the standard unit of activity.

Acute radiation syndrom:
The immediate effects of a short term, whole body overexposure of a person to ionizing radiation. These effects include nausea and vomiting, malaise, increase temerature, and blood change.

Ageing fog:
The increase in optical density on an unexposed film, measured after processing, due to long-term storage.

Alpha particle:
The nuclei of a helium atom (with two neutrons and two protons each) that are discharged by radioactive decay of many heavy elements, such as uranium-238 and plutonium-239.

Anode:
The positive electrode of an X-ray tube. In an X-ray tube, the anode carries the target.

Anode current:
The electrons passing from the cathode to the anode in an X-ray tube. There is a small loss incurred by the back scatted fraction.

Artefact (false indication):
A spurious indication on a radiograph arising e.g. from faults in the manufacturing, handling, exposing or processing of a film.

Attenuation:
The reduction in intensity of a beam of X- or gamma radiation during its passage through matter caused by absorption and scattering.

Attenuation coefficient µ:
The relationship between the intensity (I₀) of a radiation incident on one side of an absorber and the transmitted intensity (I) for an absorber thickness (t) as expressed by I₀ 10 exp (-µt).

Average gradient:
The slope of a line drawn between two specified points on the sensitometric curve.

Back scatter/back scattered radiation:
Radiation which is scattered at an angle of more than 90° in relation to the direction of the incident beam.

Beam angle:
The angle between the central axis of the radiation beam and the plane of the film.

Becquerel:
The SI unit of activity equal to one disintegration per second. [37 billion (3.7x1010) becquerels = 1 curie (Ci)].

Betatron:
A machine in which electrons are accelerated in a circular orbit before being deflected onto a target to produce high energy X-rays. This type of equipment usually operates at energies between 10 and 31 MEV.

Blocking medium:
A absorptive material surrounding specimens or covering their sections used to reduce the effect of scattered radiation on the film or on the image detector.

Build-up factor:
The ratio of the intensity of the total radiation reaching a point, to the intensity of the primary radiation reaching the same point.

Calibrated density step wedge:
A piece of film having a series of different optical densities which have been calibrated to be used as reference densities.

Cassette:
A rigid or flexible light-tight container for holding radiographic recording media (film or paper) with or without intensifying screens, during exposure.

Cathode:
The negative electrode of an X-ray tube.

Characteristic curve:
A curve (of a film) showing the relationship between the common logarithm of exposure, log K, and the optical density, D. Also called the D-log E curve or the H and D curve.

Clearing time:
The time needed for the first stage of fixing of a film, during which the cloudiness disappears.

Collimation:
The limiting of a beam of radiation to a form of required dimensions, by the use of diaphragms made of absorbing material.

Collimator:
A device made from radiation absorbent material such as lead or tungsten, designed to limit and define the direction and angular divergence of the radiation beam.

Compton scatter:
A form of scattering caused by a photon of X- or gamma radiation interacting with an electron and suffering a reduction of energy, the scattered radiation being emitted at an angle to the incident direction. Since the ejected electron has a short range in most materials, it is not considered part of the scattered radiation. For radiation in the energy range 100 keV to 10 MeV, it is the main factor contributing to radiation attenuation.

Computerized tomography (CT):
A procedure by which an image of the detail in a chosen plane, perpendicular to the axis of the specimen, is computed from a large number of X-ray absorption measurements made from many directions perpendicular to the axis. This is computerized axial tomography and does not apply to other means of performing tomography.

Constant potential circuit:
An electronic configuration which is designed to apply and maintain a substantially constant potential within an X-ray tube.

Continuous spectrum:
The range of wavelengths or quantum energies generated by an X-ray set.

Contrast:
See "Image contrast", "Radiation contrast", "Object contrast" and "Visual contrast".

Contrast medium:
Any suitable substance, solid or liquid, applied to a material being radiographed to enhance its radiation contrast in total or in part.

Contrast sensitivity (thickness sensitivity):
The smallest thickness change in specimen which produces a discemible change in optical density on a:, radiogragphic (or radioscopicl image, usually expressed as a perceatageof the total specimen thickness.'

Curie (Ci):
The unit used to describe the intensity of radioactivity in a sample of material. The curie is equal to 37 billion (3.7 x 1010) disintegrations per second, which is approximately the activity of 1 gram of radium. The Becquerel (Bq) has replaced the Ci in the SI system. The Becquerel (Bq) is 1 disintegration per second.

Decay curve:
Tftw,activity of a radiois setope;,,plotted a alInst time, usually As a Idg/lInoar. jelationship.

Densitometer:
A device for the measurement, of the optical density of a radiographic film or reflective density of a photographic print.

Development (of a film or paper):
chemical or physical process which converts a latent image into a visible image.

Diffraction mottle:
A superimposed pattern on a radiographicimtoe due to diffraction of the incident radiation by the material structure.

Dose rate rreter:
An instrument for the measurement of X- or gamma radiation dose-rate.

Dosemeter (dosimeter):
An instrument for measuring the accumulated dose of X- or gamma radiation.

Dual focus tube:
An X-ray tube with two different sizes of focus.

Dublex wire image quality indicator:
An image quality indicator specifically designed to assess the overall unsharpness of a radiographic image and composed of a series of pairs of wire elements made of high density metal.

Edge-blocking material:
Material applied around a specimen or in cavities to obtain a more uniform absorption, to reduce extraneous scattered radiation, and to prevent local over-exposure, e.g, fine lead shot (see also "Blocking medium").

Equalizing filter (beam flattener):
A device used to equalize the intensity across the primary X-ray beam in megavoltage radiography and so extend the useful field size.

Equivalent X-ray voltage:
The voltage of a X-ray tube which produces a radiograph most nearly equivalent to a gamma radiograph taken with a particular gamma-ray source.

Exposure:
The process whereby radiation is recorded on an imaging system.

Exposure calculator:
A device (for example a slide rule) which may be used to determine the exposure time required.

Exposure chart:
A chart indicating the time for radiographic exposures for different thicknesses of a specified material and for a given quality of a beam radiation,

Exposure latitude:
The range of exposures corresponding to the useful optical density range of the emulsion.

Exposure time:
Duration of the process of exposing a recording medium to radiation.

Film base:
The support material on which the photosensitive emulsion is coated.

Film gradient (G):
The slope of the characteristic curve of a film at a specified optical density D.

Film illuminator (viewing screen:
(viewing screen) Equipment containing a source of light and a translucent screen used for viewing radiographs.

Film processing:
The operations necessary to transform the latent image on the film into a permanent, visible image, consisting normally of developing, fixing, washing and drying a film.

Film system speed:
A quantitative measure of the response of a film system to radiation, energy, for specific exposure. conditions.

Filter:
Uniform layer of material, u !sual higher atomic number than the spectmen, placed between 1hp. radiation source and the film or e purpose of Preferentially absorbing::. the -softer radiations.

Fixing:
The chemical removal of silver halides from a film emulsion after development.

Flaw sensitivity:
The minimum flaw size detectable under specified test conditions.

Fluorescent intensifying, screen:
A screen consisting of a coating of phosphors which fluoresces when exposed to X- or gamma radiation.

Fluorometallic intensifying screen:
A screen consisting of a metallic foil (usually lead) coated with a material that fluoresces when exposed to X- or gamma radiation.

Fluoroscopy:
The production of a visible image on a fluorescent screen by X-rays and for direct viewing of the screen.

Focal spot size:
The dimension across the focal spot of an X-ray tube, measured parallel to the plane of the film or the fluorescent screen.

Focalspot:
The X-ray emitting area on the anode of the X-ray tube, as seen from the measuring device.

Focus-to-film distance (ffd):
The shortest distance from the focus of an X-ray tube to a film set up for a radiographic exposure.

Fog density:
A general term used to denote the optical density of a processed film caused by anything other than the direct action of image - forming radiation. It can be aging fog, chemical fog, dichroic fog, exposure fog or inherent fog.

Gamma Radiation:
High-energy, short wavelength electromagnetic radiation emitted from the nucleus of an atom. Gamma rays are very penetrating and are shielded by dense materials such as lead. Gamma rays are similar to X rays.

Gamma radiography:
Radiography using a gamma-ray source.

Gamma rays:
Electromagnetic ionizing radiation, emitted by specific radioactive materials.

Gamma-ray source:
Radioactive material sealed into a metal capsule.

Gamma-ray source container:
A container made of dense material and having a wall thickness sufficient to produce a very great reduction in the intensity of the radiation emitted by the source, so as to make it safe to handle.

Geometric unsharpness:
Unsharpness of a radiographic image arising from the finite size of the source of radiation. Its magnitude also depends on the distances of sourceto-object and object-to-film. Also called geometric blurring or penumbra.

Graininess:
The visual appearance of granularity.

Granularity:
The stochastic density fluctuations in the radiograph superimposed on the object image.

gray (Gy):
The SI (International System of Units) unit of radiation dose. The unit is named for the British physician L. Harold Gray (1905-1965), an authority on the use of radiation in the treatment of cancer.

Half life:
The time in which half the atoms of a radioactive substance will have disintegrated, leaving half the original amount. Half the residue will disintegrate in another equal period of time. The half-life values for radioisotopes vary widely.

Half value thickness (HVT):
The thickness of specified material which, when introduced into the beam of X- or gamma radiation, reduces its intensity by a half.

Illuminator:
An intense white light source for viewing radiographs.

Image contrast:

Image definition:
A qualitative term used to define sharpness of delineation of image detail in a radiograph.

Image enhancement:
Any process which increases the image definition by improving contrast and/or definition or reducing noise. When accomplished by computer programmes, it is referred to as digital image processing.

Image intensifier:
An electronic device that provides a brighter image than that produced by the unaided action of an X-ray beam on a flourescent screen.

Image quality:
That characteristic of a radiographic image defined by the degree of detail it shows.

Image quality indicator (IQI):
A device used to establish a measure of the radiographic image quality. An IQI is commonly made using wires or steps with holes.

Image quality value, IQI sensitivity:
A quantitative indication of the image quality required or achieved.

Incident beam axis:
The axis of the beam of X-radiation defined by the focal spot and the tube window.

Industrial radiology:
The use of X-rays, gamma rays, neutrons and other penetrating radiation for nondestructive testing.

Inherent filtration:
The reduction of softer radiation (lower energy) of a radiation beam by the parts of the X-ray tube, set up or source incapsulation components, through which the primary beam will pass.

Inherent unsharpness:
The blurring of a radiographic image caused by scattered secondary radiation in the imaging medium such as the photographic emulsion whereby these electrons render the silver halide grains developable.

Intensifying factor:
The ratio of the exposure time without intensifying screens, to that when screens are used, to obtain the same optical density.

Intensifying screen:
A material used in radiographic production to converts a part of the ionising radiation into light or electrons and that, when in contact with a recording medium during exposure, improves the quality of the radiograph, or reduces the exposure time required to produce a radiograph or both. Also see "Fluorometallic intensifying screen", or "Fluorescent intensifying screen".

Kerma:
An alternative term used for absorbed dose. Kerma is usually used to describe the transfer of energy from photons to electrons.

Latent image:
A condition produced in an image receptor by radiation and capable of being converted into a visible image by film processing.

Linear electron accelerator (LINAC):
A device for accelerating charged particles in a straight line, either by a steady electric field or by a radio-frequency electric field.

Masking:
The application of material which limits the area of irradiation of an object to the region undergoing radiographic examination to minimse image deterioration due to scatter radiation.

Metal screen:
A screen consisting of dense metal (usually lead) that both filters radiation and intensifies an image by emiting electrons when exposed to X- or gamma rays.

Microfocus radiography:
Radiography using an X-ray tube having a small effective focus-size of less than 0.1mm in size. Used for geometric enlargement of the image by projection.

Modulation transfer function (MTF):
The ratio of the image amplitude to the object amplitude as a function of sinusoidal frequency variation in the object.

Movement unsharpness:
Blurring of a radiographic or radioscopic image as a result of relatitve movement of the radiation source, object or, radiation detector.

Neutron:
An neutral hadron that is stable in the atomic nucleus but decays into a proton, an electron and an antineutrino with a half-life of 12 minutes outside of the nucleus. In the nucleus it has a rest mass slightly greater than the proton and a neutral charge.

Object contrast:
The relative difference of radiation transmitted between two regions of an irradiated object.

Object-to-film distance:
The distance between the radiation side of a test object and the film used to radiograph the object as measured along the central axis of the radiation beam.

Panoramic exposure:
A radiographic set-up whereby several objects are exposed simultaneously, or the full circumference of a cylindrical specimen is exposed by the onmidirectional characteristics of the radiation source.

Penetrameter:

Pressure mark:
A blemish on a radiograph, which may be light or dark in appearance, depending on circumstances, and caused by local pressure to the film.

Primary radiation:
Radiation which travels along a straight line, without scatter, from the source to the detector.

Projective magnification:
The degree of image size enlargement.

Projective magnification technique Quality (of a beam of radiation):
Also called Projection Microfocus radiography. A method of radiography or radioscopy that provides an enlargement of the image by the use of a distance between the specimen and imaging system. (see "Microfocus radiography").

rad (rd):
An old unit of absorbed radiation dose. One rad is equal to a dose of 0.01 joule of energy per kilogram of mass (J/kg); one rad equals 0.01 gray or 10 milligrays. "Rad" is an acronym for "radiation absorbed dose."

Quality of a beam of radiation:
The penetrating ability of a specified form of radiation, usually measured as a half-value thickness of a specified material.

Radiation contrast:
Differences in radiation intensity due to variation in radiation opacity within an irradiated object.

Radiation source:
Equipment used for generating X-rays or gamma rays or other penetrating radiation sources(e.g. protons, neutrons, Beta rays).

Radiograph:
A visible image after processing produced by a beam of penetrating radiation on a radiographic film or paper.

Radiographic film:
An image storage medium consisting of a transparent base, usually coated on both sides with a radiation sensitive emulsion.

Radiography:
The production of permanent visual image using penetrating radiation through the material tested.

Radioscopy:
The electronic production of a visual image by ionising radiation on a radiation detector and displayed on a monitor or similar screen.

Radioisotope:
An unstable isotope of an element that decays by emitting particles or gamma radiation or X-radiation.

Rod anode tube:
Uni-polar tubes with a long hollow anode in which the target is situated at the extremity of a tubular anode. These tubes generally produce a panoramic beam of radiation.

Scattered Radiation:
Particulate or EM radiation that has undergone a change in direction with or without a change in energy, during its passage through intervening matter.

Screen type film:
Radiographic fiIm designed to be used with fluorescent or lead intensifying screens.

SI units:
Abbreviation for Système International d'Unités. The international system of units derived from the m.k.s. units.

Sievert:
The SI unit of absorbed dose equivalent (1 Joule/Kilogram or 100 rems).

Source holder:
A container for a gamma ray source (sealed source).

Source size:
An indication of the radioactive intensity of a radioactive mass typically in units of Bequerels (formerly in Curies).

Source-to-film distance (sfd):
The distance between the source of radiation and the film along the path of the beam of radiation.

Spatial resolution:
The ability to form separable images of close objects.

Specific activity:
The number of atoms of a radioactive substance that disintigrate per unt time per unit mass of a radioisotope.

Step wedge:
An object with specified thickness steps used to obtain a radiograph of discrete densitiy values.

Stereo radiography:
The production of two radiographs made using a source shift exactluy parallel to the film plane.

Target:
A high melting point metal on the end of the anode of an X-ray tube on which the electron beam impinges and from which the primary beam of X-rays is emitted

Tube diaphragm:
A device, normally fixed to a tube shield in front of the tube window, used to reduce scatter by limiting the extent of the emergent X-ray beam.

Tube head:
One of the three main parts of an X-ray installation. The tube head contains the tube in its shield, the other two include the transformer and control panel.

Tube shield:
The metal container that supports the X-ray tube and hold the coolant and electrical insulation fluid. It also provides a means of reducing the leakage radiation.

Tube shutter:
A device used on an X-ray tube, used to regulate the X-ray beam, usually made of lead and remotely operated.

Tube voltage:
The potential difference between the anode and the cathode of an X-ray tube, usually measured in kilovolts (kV).

Tube window:
An area of relative transparency to X-rays in the X-ray tube through which the radiation is emitted.

Unsealed source:
Any radioactive material not encapsulated for safe handling.

Unsharpness:
A quantified value of image blurring. It is the total of "geometric unsharpness", "inherent unsharpness" and "movement unsharpness",

Useful density range:
The practical range of optical density on a radiograph. Maximum density is determined by the film illuminator and the minimum by the loss in flaw sensitivity.

Vacuum cassette:
A light-tight container using a vacuum to hold a radiographic recording media, film and screens, in intimate contact during radiographic exposure.

Viewing mask:
A device used with a radiographic illuminator used to exclude excessive transmitted light or to prevent light from passing the edges of the radiograph.

Visual contrast:
A density difference perceived visually between two adjacent areas when viewing a radiograph.

X-ray film:

X-ray tube:
A device for generating X-rays by accelerating electrons from a filament to strike a metal target (anode).

X-rays:
Electromagnetic radiation (photon), of shorter wavelength than ultraviolet radiation. Produced by bombardment of atoms by high-quntum-energy particles. Radiation wavelength is from 10^-11 to 10^-9 m.

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