Download Windows 7 Build 6956 VHD Image via BT Torrent (Possibly Beta)

Windows 7 beta (or beta 1) is possibly been released in January or February 2009 which Keith Comb has even mentioned in a comment on his TechNet blog (has since been removed) that “we (Microsoft) are targeting to have the DVD’s in the materials from 1/13/2009 on”. With the imminent arrival of Windows 7 beta 1 milestone build, any build version that is leaked or made know publicly can be of ‘beta quality’ (means can be released as beta build). Windows 7 build 6956, which is been showcased during WinHEC 2008 in Beijing recently, is one such candidate.According to a participant, edward_han who managed to steal a VHD (Virtual Hard Disk) image of Windows 7 Build 6956 out of WinHEC 2008, the build has the following features and enhancements (for complete Windows 7 features, see top 30 Windows 7 features or Desktop font no longer has problem when using Desktop Slideshow as background wallpaper rotator.
More Windows Aero features.

1. A lot more new desktop background wallpapers.
2. New Windows 7 start screen.
3. Increase in the Windows Experience Index which is now ranging from 1.0 to 7.9, which can be hacked to change the score.
4. New icons for some programs, such as Task Manager, even the options icons inside it are updated.
5. No more Quick Launch bar.
6. Media Center gadget now works properly, and then MediaCenter gadget is of bigger size with new initialization setup screen.
7. Right click on running application button or icon on Taskbar will open Jumplist.
8. Desktop Preview works.
   

Last but not least is that the confirmation that Windows 7 build 6956 will be similar (not a lot of differences) with the beta version that going to be released, or in fact can be the beta version itself. This version of build also include a “Send feedback” link, which probably reflect that the build, or slight variation of it is intended for outside of Microsoft consumption.
Good news is that the ’stolen’ Windows 7 build 6956′ has been released to Internet for everybody to download, albeit it’s not in installation DVD or ISO format. The currently available Windows 7 build 6956 is in VHD format, a virtual hard disk meant for virtual machine. Which means no installation required to try out Windows 7 build 6956. However, things is not as easy. Other than users will require Virtual Server 2005, Hyer-V HyperVisor or Windows 7 Disk Management to load the VHD image (although Virtual PC VPC 2007 can support VHD extension format, it’s unlikely you will be able to run the VHD), the VHD image is preloaded with drivers with may incompatible with other computers, causing the Windows 7 OS inside the VHD fails to load and can’t properly boot up. Of course, there are ways to fix, but before any error can be fixed, the VHD image must be downloaded.
Here’s the torrent file to download the much anticipated Windows 7 build 6956 with all features already unlocked, unlike Windows 7 build 6801 which requires BlueBadge hack tool to unlock hidden protected features.
Torrent File for BT Network Download: WinHEC.6956.rar (extract for torrent file) or WinHEC.torrent or HEC.rar.torrent (all point to same trackers)
The download size of the VHD compressed in RAR archive format is 1.82 GB.

Phased Array Applications

Where are phased array systems used?
Ultrasonic phased array systems can potentially be employed in almost any test where conventional ultrasonic flaw detectors have traditionally been used. Weld inspection and crack detection are the most important applications, and these tests are done across a wide range of industries including aerospace, power generation, petrochemical, metal billet and tubular goods suppliers, pipeline construction and maintenance, structural metals, and general manufacturing. Phased arrays can also be effectively used to profile remaining wall thickness in corrosion survey applications. The benefits of phased array technology over conventional UT come from its ability to use multiple elements to steer, focus and scan beams with a single transducer assembly. Beam steering, commonly referred to sectorial scanning, can be used for mapping components at appropriate angles. This can greatly simplify the inspection of components with complex geometries. The small footprint of the transducer and the ability to sweep the beam without moving the probe also aids inspection of such components in situations where there is limited access for mechanical scanning. Sectorial scanning is also typically used for weld inspection. The ability to test welds with multiple angles from a single probe greatly increases the probability of detection of anomalies. Electronic focusing permits optimizing the beam shape and size at the expected defect location, thus further optimizing probability of detection. The ability to focus at multiple depths also improves the ability for sizing critical defects for volumetric inspections. Focusing can significantly improve signal-to-noise ratio in challenging applications, and electronic scanning across many groups of elements allows for C-Scan images to be produced very rapidly.

An Introduction to Ultrasonic Phased Array Technology

What is a phased array system?
Conventional ultrasonic transducers for NDT commonly consist of either a single active element that both generates and receives high frequency sound waves, or two paired elements, one for transmitting and one for receiving. Phased array probes, on the other hand, typically consist of a transducer assembly with from 16 to as many as 256 small individual elements that can each be pulsed separately. These may be arranged in a strip (linear array), a ring (annular array), a circular matrix (circular array), or a more complex shape. As is the case with conventional transducers, phased array probes may be designed for direct contact use, as part of an angle beam assembly with a wedge, or for immersion use with sound coupling through a water path. Transducer frequencies are most commonly in the range from 2 MHz to 10 MHz. A phased array system will also include a sophisticated computer-based instrument that is capable of driving the multi-element probe, receiving and digitizing the returning echoes, and plotting that echo information in various standard formats. Unlike conventional flaw detectors, phased array systems can sweep a sound beam through a range of refracted angles or along a linear path, or dynamically focus at a number of different depths, thus increasing both flexibility and capability in inspection setups.

Typical phased array probe assemblies

Typical multi-element construction

How do they work?
In the most basic sense, a phased array system utilizes the wave physics principle of phasing, varying the time between a series of outgoing ultrasonic pulses in such a way that the individual wave fronts generated by each element in the array combine with each other to add or cancel energy in predictable ways that effectively steer and shape the sound beam. This is accomplished by pulsing the individual probe elements at slightly different times. Frequently the elements will be pulsed in groups of 4 to 32 in order to improve effective sensitivity by increasing aperture, which reduces unwanted beam spreading and enables sharper focusing. Software known as a focal law calculator establishes specific delay times for firing each group of elements in order to generate the desired beam shape, taking into account probe and wedge characteristics as well as the geometry and acoustical properties of the test material. The programmed pulsing sequence selected by the instrument's operating software then launches a number of individual wave fronts in the test material. These wave fronts in turn combine constructively and destructively into a single primary wave front that travels through the test material and reflects off cracks, discontinuities, back walls, and other material boundaries like any conventional ultrasonic wave. The beam can be dynamically steered through various angles, focal distances, and focal spot sizes in such a way that a single probe assembly is capable of examining the test material across a range of different perspectives. This beam steering happens very quickly, so that a scan from multiple angles or with multiple focal depths can be performed in a small fraction of a second.

The returning echoes are received by the various elements or groups of elements and time-shifted as necessary to compensate for varying wedge delays and then summed. Unlike a conventional single element transducer, which will effectively merge the effects of all beam components that strike its area, a phased array transducer can spatially sort the returning wavefront according to the arrival time and amplitude at each element. When processed by instrument software, each returned focal law represents the reflection from a particular angular component of the beam, a particular point along a linear path, and/or a reflection from a particular focal depth. The echo information can then be displayed in any of several formats.

Example of angled beam generated by flat probe by means of variable delay

Example of focused linear scan beam

What do the images look like?
In most typical flaw detection and thickness gaging applications, the ultrasonic test data will be based on time and amplitude information derived from processed RF waveforms. These waveforms and the information extracted from them will commonly be presented in one or more of four formats: A-scans, B-scans, C-scans, or S-scans. This section shows some examples of image presentations from both conventional flaw detectors and phased array systems.
A-Scan displays
An A-scan is a simple RF waveform presentation showing the time and amplitude of an ultrasonic signal, as commonly provided by conventional ultrasonic flaw detectors and waveform display thickness gages. An A-scan waveform represents the reflections from one sound beam position in the test piece. The flaw detector A-scan below shows echoes from two side-drilled holes in a steel reference block. The columnar sound beam from a common single-element contact transducer intercepts two out of the three of the holes and generates two distinct reflections at different times that are proportional to the depth of the holes.

Generalized beam profile Straight beam A-scan image

Generalized beam profile Angle beam A-scan image

Rail testing ultrasonic flaw detector Sonatest Railscan 125R

Setting standards of performance and reliability.
For over 20 years the Railscan name has meant exceptional performance with class leading design. The latest developments in amplifier and pulser technology deliver higher levels of near surface resolution, penetrating power and excellent signal to noise ratio.
Designed specifically for Rail Testing

Network Rail (UK) procedure and approval Narrow Band amplifiers 2 and 5 MHz G1 +ve trigger, G2 -ve trigger, (0.6 second delay for monitoring rail bottom depth).
Long Battery Life
Latest Li-Ion technology 10-16 hours (brightness dependant) Quick re-charge in 3-4 hours
Walking Stick Compatibility
Sperry walking stick. Others (e.g., NRS bi-directional walking stick) Single-shot PRF for high speed multiplexing RS232 & USB outputs for custom software systems, (e.g. Sperry palmtop with GPS)
Robust and Reliable
Sonatest's reputation for robust design and proven reliability is an important aspect of flaw detector ownership.
Down time is expensive and should be minimised to ensure maximum productivity. The Railscan is constructed to high standards using Xenoy plastics and sealed to IP67, giving excellent water resistance so it can withstand the tough environments in which operators work.
The Railscan comes with 2 years warranty, extendable to 5 years with Sonacover, and a worldwide service network.
High Performance with Total Control
The Railscan delivers high performance and advanced features, yet our engineer's experience in user interface design has ensured it is easy and quick to use. The acknowledged ease of use of the previous Railscan generation has been enhanced with the menu navigation key, providing easy access to functions. The menu structure has been designed to guide the user through their task with operation quickly becoming second nature.
High Visibility Display
For any flaw detector the display is a crucial element. The Railscan has a colour transflective TFT display as standard, providing high visibility at any light level. The choice of colours for menus and waveform display enhance clarity, with the LCD simulation mode giving direct sunlight readability. The TFT does not suffer the typical black out problems or temperature limitations of LCD giving full weather capability. The new Full Screen mode maximises the A-scan area to improve readability further whilst testing and its fast response and peak capture functionality ensure any indicationis clearly displayed, even if it only appears for one cycle of the 1 KHz PRF.
SDMS (Optional Sonatest Data Management Software)
This Windows based data management tool allows the user to interface a Sonatest digital flaw detector with a PC. The software uploads and downloads panel settings and A-scans, which can also be copied and pasted into Word for customised reporting. Thickness readings can be transferred directly into Excel with the ability to produce charts for B & C-Scans, colour 3D mapping etc.

Ultrasonic Specifications Measurement Modes:
Test Range: 0 - 5mm (0.2in) up to 0 - 10000 mm (400 in.) at steel velocity. Variable in 1mm & 10mm steps.
Velocity: 1000 to 9,999m/s continuously variable.
Probe Zero: 0 to 999.999 μs, continuously variable.
Delay: Calibrated delay from 0-10000mm in 0.05 mm steps at steel velocity (0-400in. in 0.002 in. steps).
Gain: 0 to 110dB. Adjustable in 0.5, 1, 2, 6, 10, 14 and 20dB steps. Direct access to gain control at all times.
Test Modes: Pulse echo and transmit/receive.
Pulser: -200V square wave pulser. Pulse width 100ns. Rise/fall times <10ns>P.R.F: 1000 Hz.
Update Rate: 60Hz (NTSC Mode); 50Hz (PAL Mode).
Rectification: Full wave.
Frequency: Range 2.5MHz and 5.0MHz.
System Linearity: Vertical = 1% Full Screen Height (FSH). Amplifier Accuracy ±0.1dB. Horizontal ±0.4% Full Screen Width (FSW).
Units: Metric (mm) or inch (in).
Display:
Display: Colour Transflective TFT: Display area 111.4 x 83.5 mm (4.39 x 3.29 in) 320 x 240 pixels. A-Scan Area 255 x 200 pixels (315 x200 expanded), 8 colour options and variable brightness.
Gate Monitor: Two fully independent gates for echo monitoring and thickness measurement. Start and width adjustable over full range of unit,amplitude variable from 0 to 100% FSH. Bar presentation. Positive triggering for gate 1 and negative triggering for gate 2, both with audible and visual alarms.
Gate Expansion: Expands range to width of Gate 1.
Gate Monitor Delay: Fixed 0.6 seconds delay on Gate 2 negative monitor tracking.
Measurement Modes:
Mode 1: Signal Monitor
Mode 2: Depth and amplitude of first signal in gate.
Mode 3: Echo-to-Echo distance measurement. (single gate)
Mode 4: Trigonometric display of beam path, surface distance and depth of indication, curve surface correction and X-OFFSET for probe index. Half skip indication on screen.
Mode 5: T-Min mode for holding minimum thickness reading.
Resolution: 0.01mm (0.001in) for distance measurement or 1% FSH for amplitudemeasurement. Large display of measurement at the top of A-Scan display. Measurement mode selectable between peak and flank.
A-Scan Memory: Maximum of 800 waveforms can be printed or transferred toa PC using optional SDMS software.
Panel Memory: 100 stores for retaining calibrations.
Thickness Logging: Storage for 8000 thickness readings configured either by Block/Location/Number mode or pre-programmable work sheets in sequential mode. Readings can be exported to MS Excel using optional SDMS software.
DAC: DAC defined by up to 10 points and digitally drawn on screen. DAC curves meet requirements of EN 1714, JIS and ASME standards, selectable between -2, -6, -10, -12 and -14dB. Amplitude read out selectable between % DAC or relative dB.
Auto-Cal: Provides automatic calibration from two echoes.
Clock: Sets time and date.
Notes: Alphanumeric labelling for panel and A-log allows the user to enter Notes for storage with panel settings and A-scans.
Display Freeze: For capturing the current A-scan image.
Peak Memory: For echo dynamic pattern determination.
Keylock: Prevents accidental alteration of parameters.
Help Key: For instant operator guidance on using the Railscan unit.
Language Support: Supports multiple languages. User selectable between English,German, Spanish, French, Dutch, Italian, Russian, Polish, Czech, Finnish & Hungarian. Others available on request.
Waveform Smoothing: Gives a smooth signal envelope, simulating analogue equipment.
Outputs: Full bi-directional serial interface to transfer parameters, thicknessreadings and waveform memories. Composite video, PAL or NTSCcompatibility.
External Alarm: Front mounted socket for attachment.
Printers: Supports any printer with PCL support including Hp DeskJet and Epson.
Power: Lithium Ion battery pack 14.4V, 5.0 ampere hours, gives up to 16 hours duration from a fully charged pack. Indication of lowbattery status. Recharge time 3-4 hrs.
Charger: 100 - 240 VAC, 50-60Hz.
Transducer Sockets: BNC or LEMO (factory option)
Environmental: Case sealed to IP67
Temperature: Operating -10°C to +55°C (14 to 131°F). -20°C to +70°C. (-4 to 158°F) survivable.Storage: -40° to +75°C. (-40 to = 167°F)
Physical:
Size: 255 x 145 x 145mm (10.0 x 5.7 x 5.7 in)
Weight: 2.5kg (5.5lbs) with Li-Ion cells.
Accessories:
Standard Kit Includes: Railscan 125RLi-ion Battery & Battery ChargerFabric Carry BagCalibration CertificateInstruction Manual (EN12668)
Certification: Calibration Certificate

Napster Launches DRM-Free Music Store: Over 6 Million MP3s

Look out, Amazon. Napster just launched the largest music store free of digital rights management in the world, with six million songs that can be loaded onto just about any digital audio player -- a healthy advantage over Amazon's five-million-track MP3 store.
Apple also has cause for concern. Two of its most widely-known competitors now offer DRM-free music the majors won't let Apple sell without DRM. Apple's latest figures on the topic (released in October) indicated that it only had two million DRM-free tracks.
Napster will continue selling songs for 99 cents a piece and albums for $10, except that now every song in its six-million-track catalog will be available in the unprotected MP3 format instead of the Microsoft's Playsforsure-protected format it had previously used to placate the record labels, before they became more afraid of Apple than they were of DRM-free music.
In a piece called "The Future of Online Music: Why Closed Platforms Will Fail," Napster's CTO Bill Pence wrote to Listening Post nearly two years ago, "I believe strongly that the market in the end must and will be based on interoperable digital formats, [and] if DRM is used to erect barriers to that goal, then there is no question it will be swept aside, and the industry may end up with what many have believed was the obvious choice from the beginning: open MP3 files." For Napster, that day has come -- at least as far as single-song and album downloads go.
"Music fans have spoken and it's clear they need the convenience, ease of use and broad interoperability of the DRM-free MP3 format," said Napster CEO Chris Gorog, "and they want to be able to find both major label artists and independent music all in one place. Napster is delighted to deliver all of this and more with the world’s largest MP3 catalog."
However, Napster will continue to offer its monthly music subscription service using DRM in addition to the MP3-download store, making it the first to offer an unlimited music subscription that lets users buy the songs they hear without DRM attached. According to the company, the vast majority of the six million MP3s in its store are encoded at 256 Kbps.
"By offering millions of high quality, MP3-encoded DRM-free tracks from all of the major labels as well as independents," said Susan Kevorkian, audio analyst for IDC, "this service is well-positioned to appeal to the broad spectrum of music lovers, including iPod and iPhone owners."
Unlike Amazon, Napster doesn't offer any software for syncing purchased songs into iTunes so that users can easily transfer them onto their iPods. A Napster spokesman told Wired.com that the current solution for importing into iTunes or any other media player is to import them manually by either double-clicking the files after they've downloaded or dragging and dropping them into the player.
The Napster spokesman also told us that as with Amazon's MP3 service, some of Napster's songs will contain identifying watermarks. However, as with Amazon's situation, these watermarks only indicate which store the song was purchased from, rather than identifying the person who purchased it. (This is a key distinction. Otherwise, someone could steal your laptop, share your music and land you in a sticky infringement suit where you'd have to explain how a song you purchased ended up being shared all over the world.)
Here's a screenshot of Napster MP3 store:

Digital voice recorder

Recording devices are used to capture various data including speech in analog or digital form. The market for voice recording and reproducing devices, often referred to as voice recorders, is growing rapidly. Recording and playback of voice messages is often useful in business applications such as in order entry systems, dictation for subsequent transcription, obtaining spoken output from a computer data base. Pocket-sized voice recorders are widely used as a convenient way to take notes, store information and create documents in audio form. For many years, very compact portable tape recorders have been available in a size which fits comfortably in the palm of the user's hand. These portable recorders are used to record spoken words or other sounds in analog form on removable magnetic tape cassettes. In recent years, there is provided a recorder in which a voice signal obtained by a microphone is converted into a digital signal, the digital signal is stored in a semiconductor memory, the voice signal is read from the semiconductor memory to be converted into an analog signal in a reproducing operation, and the analog signal is outputted as voice by a loudspeaker. Digital audio recorders are used as voice memo recorders, and as voice message recorders in portable telephone sets. In particular, digital voice recorders employing integrated-circuit (IC) memory as storage media are now finding many applications. Some digital audio recorders employ nonvolatile semiconductor memory, such as flash memory, as a recording medium.
Various types of digital voice recording and reproducing apparatuses have been developed and practically used. A digital voice recorder converts an analog signal representing a voice to a digital signal and records the digital signal in a recording medium when the voice is recorded, and converts the digital signal to an analog signal when the voice is reproduced. Digital compression / decompression circuits may be employed to increase storage capacity for a fixed memory size. These integrated circuit recorders may record analog values representing the instantaneous amplitude of the sound reaching the unit's microphone or the microphone output may be digitized and stored as binary values. The analog signal representing the collected voice is converted to a digital signal which is then stored in a storage medium of the digital recorder. When the recorded voice is reproduced, the stored digital voice is read out from the storage medium and converted to an analog signal. The analog signal is then reproduced by a speaker. In the recording mode, the digital voice system first produces a stream of digital data which represents the audio message signal; this stream of digital data is then recorded on a digital memory. In the playback mode, the memory card is accessed for a particular message, the message is converted into a stream of digital data which is, in turn, converted to an audio signal. Most voice recorders provide basic functions such as record, stop, play, rewind and fast forward. To permit a user to selectively actuate these functions, a number of manually operable switches are typically provided on the housing of the recorder. Often these recorders employ sound responsive switches to reduce the battery drain when there are no sounds to be recorded. The digital voice recording and reproducing apparatus has been practically used also in a dictation system in which the dictations recorded by a plurality of dictators are reproduced and typed by a typist, or in centralized type of dictation system in which a dictation is directly recorded by a dictator via a telephone network or the like to a reproducing apparatus located on the side of a typist.
Generally, in the voice recording/reproducing apparatus, in order to save an amount of data recorded in the semiconductor memory, the amount of data to be generated is controlled to be as small as possible by efficiently coding the digitized voice signal. The primary benefit of high compression recording is that it maximizes the available capacity in the recording medium. For business applications, a long recording time and good sound quality are essential requirements. It is thus desirable to record audio information at the highest possible degree of compression consistent with adequate sound quality and reasonable processing overhead. The factor enabling these requirements to be met has been the recent rapid progress in high-efficiency compression technology. Compression is achieved through coding techniques that make intensive use of complex, sophisticated digital signal processing, which requires a fast, high-performance digital signal processor (DSP). When the digital signal is stored in the storage medium, the digital recorder generally applies a coding technique to compress the volume of data efficiently for saving the space of the storage medium. There has been widely used a code drive linear predictive coding system having an adaptive code book as a means for efficient coding.
Voice recording and/or reproduction apparatus such as tape recorders had used a magnetic tape as a memory medium. However, the magnetic tape has major drawbacks. In recent years, compact audio recorders have been developed in which the audio information is stored as digital data in a solid state memory. The semiconductor memory is preferred as memory medium because no mechanical driving will be required. Nonvolatile semiconductor memory devices in general, and flash memory in particular, can tolerate only a limited number of erase-write cycles. A single memory device may store several recorded messages, so address information indicating where each message begins and ends is also stored. Solid state memories employing integrated circuits have supplanted tape recorders in many applications resulting in even smaller and lighter-weight units. In a flash memory device, the address information is stored in a single sector or page, which is erased and rewritten whenever a new message is recorded.

A-Scan Thickness Survey

How does it work?
Thickness measurements are performed using a conventional flaw detector and a compression wave probe, which sends longitudinal waves into the component at normal incidence to the surface. Signals are displayed on the flaw detector screen in the form of an A-scan, in which the horizontal axis represents distance and the vertical axis represents signal amplitude. Since a 0° compression probe is being used, the horizontal axis is equivalent to depth from the scanning surface. When the probe is placed on the surface of the component, a reflection appears at a range corresponding to the thickness of the component at that point. The use of an A-scan display allows the operator to distinguish more easily between signals originating from embedded plate flaws and the nominal back wall response. Also, the dynamics of the back wall echo can be observed on the A-scan display to detect the presence of pitting.
Conventional twin-crystal 0° compression probes are generally used to detect hidden corrosion. However, where pitted surfaces are being assessed for remaining thickness, pencil probes are used. These have a pointed tip which is designed to fit into the pits, so that the remaining thickness can be measured where the external pitting is at its most severe.
What will it find?
Internal corrosion pitting and general erosion in most metals. A-Scan thickness surveys are also used for the inspection of parent material for inclusions and laminations.
Where is it used?
Generally used for thickness surveys on pressure vessels, pipelines, storage tanks and ship hulls.

A-Scan Weld Inspection

How does it work?
A strong specular reflection is required to resolve a flaw response from the background noise level with pulse echo ultrasonics. For planar flaws (cracks, lack of fusion, etc.) a specular reflection will only result if the ultrasonic beam is normal (or near normal) to the plane of the flaw. Angled beam shear wave probes are commonly used for the manual ultrasonic inspection of welds in ferritic steels, as these provide the only way of directing ultrasound into the weld body when the cap reinforcement is still present. Where a weld cap restricts probe movement, the sound can be reflected off the bottom surface and directed into the weld body under the cap.
Where sound is angled directly at the area of interest, this is referred to as "half skip testing". "Full skip" testing occurs when the bottom surface is used to reflect the sound before it enters the weld.
For a typical girth weld, a 45° probe is used for inspecting the root region, and 60°/70° probes for the sidewall fusion faces and weld body. The behaviour of the echo-dynamic pattern and shape of the flaw response (with respect to probe movement) can be used to identify the type of flaw, estimate the length and, in some cases, the through-wall height of the flaw.
Vertically orientated planar flaws can be a particular problem for detection using an angle probe in pulse-echo mode. However, a variation of angled shear wave ultrasonics is the Tandem technique, which is normally used for the detection of vertical flaws in thick section components. Two 45° shear wave probes are positioned in a jig, one behind the other facing the area of interest. The rear probe is used to transmit ultrasound into the joint area and the front probe receives sound reflected from flaws within the insonified region. By moving the probes relative to each other, it is possible to obtain full-through thickness coverage.
The type of material to be inspected affects the choice of angle probe. Shear wave probes are commonly used for examining welds in fine grained materials such as ferritic steels and aluminium. Welds in coarse grained materials such as stainless steels, duplex stainless, copper and composites have a severe attenuating effect on shear waves and can cause beam skewing effects at fusion faces. For welds in these types of materials, angled compression waves are used. However, these have a longer wavelength than shear waves, so there is a reduction in their resolving power. A-Scan weld inspection using angled compression wave probes can be very difficult due to the presence of spurious mode converted signals on the flaw detector display. Consequently, such probes are restricted to half skip testing and are preferably used in conjunction with an imaging system.
What will it find?
Most manufacturing flaws (lack of sidewall fusion, lack of root fusion, lack of root penetration, porosity, solidification cracking, etc.) and in-service flaws (fatigue cracking, stress corrosion cracking, etc.).
Where is it used?
Inspection of welds made in both ferritic and non-ferritic metals in pressure vessels, pipework, storage tanks, bridge structures etc.

Pulse Echo Imaging

How does it work?
By using the standard ultrasonic probes used for pulse-echo thickness measurement and weld inspection with a position encoded scanner device and appropriate software, images of flaws can be generated and electronically saved. Imaging systems provide a highly repeatable inspection and are capable of showing the extent of scan coverage. Due to their ability to store data, they can be used to "fingerprint" a component for comparison with any repeat inspections.
Programmed parameters such as material velocity and beam angles are used in conjunction with positional data to automatically plot flaw responses in the correct position on top, side and end view images showing the volume of material inspected. Many different systems are commercially available, offering two or three dimensional images. Each image view is known by a particular name as follows:
C-Scan image
This is another name for a top (or plan) view image. C-Scans can be obtained from immersion testing systems (where a 0° compression wave probe is scanned across an area through a water path, i.e. non-contact scanning) or from direct 0° contact scans.
Depending on the mode of operation selected, the colour coding levels on the image may represent signal amplitude or range. The latter case is used for automated corrosion mapping where on-screen cursors can be used to show the thickness at any point and sectional thickness plots.
B-Scan and D-Scan images
These images are usually through-thickness side and end view slices which are produced by scanning a probe beam in a linear fashion across an area of interest. The B scan is normally used as a transverse section through a weld and is taken in the scanning direction whereas the D scan is a longitudinal view and is taken in the index direction which is orthogonal to the scanning direction. The B-Scan image is normally acquired through a flaw where it has its greatest through-wall extent and provides an estimate of both remaining ligament and height. As the probe is moved, the A-Scan signals are recorded and plotted according to probe position, range and probe angle. Owing to the beam divergence, the response from a point reflector (e.g. pore) will be plotted along the beam axis even when it does not lie on it, causing arc shaped indications on the B-Scan image. These characteristic arcs vary in shape and size according to the width of the ultrasonic beam at different depths within the material.
Some of the more advanced imaging systems are also capable of generating an amplitude colour coded side view image and of storing all of the raw A-Scan data acquired. For automated scans, individual probes can either be "raster" scanned in the conventional manner, focused at a fixed stand-off (thereby targeting a particular depth zone) or part of a Phased Array.
What will it find?
Manufacturing flaws (lack of sidewall fusion, lack of root penetration, lack of root fusion, porosity, etc.), in-service flaws (fatigue cracking, stress corrosion cracking, corrosion, erosion, etc.) and parent material flaws (inclusions and laminations).
Where is it used?
Thickness surveys and parent plate or weld inspection on ferritic and non-ferritic pressure vessels, pipework, storage tanks, bridge structures, etc.

Ultrasonic Test System Basics PC-Based

Ultrasonic test systems can take several forms, but the most common for automated test is immersion testing. To have good acoustical impedance matching between the couplant and the UUT and free range over the entire surface of the UUT, many test systems use an immersion tank filled with water.
These test systems use one or more ultrasonic transducers, which are moved over the surface of the unit under test (UUT). As the transducer is moved over the surface, it is pulsed and receives echoes from various surfaces. This process is repeated many times a second — sometimes over 50,000 times per second (>50 kHz). There are several pieces of the test system that must work together to get expected results. The following list includes the steps, and the accompanying hardware and software pieces, required to get one pulse and the subsequent echoes:
Application software – The user interacts with the application software to set up the test and presentation parameters.
Motion control – The ultrasonic transducer is moved over the appropriate area over the UUT.
Communication – The pulser/receiver operation parameters, such as pulse energy, pulse damping, and bandpass filtering, are set. The communication path is typically RS-232 or USB.
Pulser/Receiver – This device generates the high voltage pulse that is required by the ultrasonic transducer.
Ultrasonic Transducer – The transducer is pulsed, sending out an ultrasonic wave. The subsequent echoes generate a voltage in the transducer, which is sent back to the pulser/receiver.
Pulser/Receiver – The analog signal from the ultrasonic transducer is amplified and filtered before it is sent back to the digitizer within the PC.
Digitizer – The waveform sent from the pulser/receiver is converted from voltage to bits using an analog-to-digital converter.
Application software – Data from the digitizer is processed, analyzed, and presented according to the user-defined parameters. If there are multiple transducers that are coupled with one digitzer/pulser/receiver combination, switches much be used.There are several hardware and software components that must interact effectively for even the simplest ultrasonic test system to work properly. When assembling your custom ultrasonic test system, there are several factors to consider for each component of the system, including how well the components interact with one another. The Ultrasonic Transducer section describes each component of the test system in detail as well as the important features required for ultrasonic testing.

Present State of Ultrasonics

Ultrasonic testing (UT) has been practiced for many decades. Initial rapid developments in instrumentation spurred by the technological advances from the 1950's continue today. Through the 1980's and continuing through the present, computers have provided technicians with smaller and more rugged instruments with greater capabilities.
Thickness gauging is an example application where instruments have been refined make data collection easier and better. Built-in data logging capabilities allow thousands of measurements to be recorded and eliminate the need for a "scribe." Some instruments have the capability to capture waveforms as well as thickness readings. The waveform option allows an operator to view or review the A-scan signal of thickness measurement long after the completion of an inspection. Also, some instruments are capable of modifying the measurement based on the surface conditions of the material. For example, the signal from a pitted or eroded inner surface of a pipe would be treated differently than a smooth surface. This has led to more accurate and repeatable field measurements.
Many ultrasonic flaw detectors have a trigonometric function that allows for fast and accurate location determination of flaws when performing shear wave inspections. Cathode ray tubes, for the most part, have been replaced with LED or LCD screens. These screens, in most cases, are extremely easy to view in a wide range of ambient lighting. Bright or low light working conditions encountered by technicians have little effect on the technician's ability to view the screen. Screens can be adjusted for brightness, contrast, and on some instruments even the color of the screen and signal can be selected. Transducers can be programmed with predetermined instrument settings. The operator only has to connect the transducer and the instrument will set variables such as frequency and probe drive.
Along with computers, motion control and robotics have contributed to the advancement of ultrasonic inspections. Early on, the advantage of a stationary platform was recognized and used in industry. Computers can be programmed to inspect large, complex shaped components, with one or multiple transducers collecting information. Automated systems typically consisted of an immersion tank, scanning system, and recording system for a printout of the scan. The immersion tank can be replaced with a squirter systems, which allows the sound to be transmitted through a water column. The resultant C-scan provides a plan or top view of the component. Scanning of components is considerably faster than contact hand scanning, the coupling is much more consistent. The scan information is collected by a computer for evaluation, transmission to a customer, and archiving.
Today, quantitative theories have been developed to describe the interaction of the interrogating fields with flaws. Models incorporating the results have been integrated with solid model descriptions of real-part geometries to simulate practical inspections. Related tools allow NDE to be considered during the design process on an equal footing with other failure-related engineering disciplines. Quantitative descriptions of NDE performance, such as the probability of detection (POD), have become an integral part of statistical risk assessment. Measurement procedures initially developed for metals have been extended to engineered materials such as composites, where anisotropy and inhomogeneity have become important issues. The rapid advances in digitization and computing capabilities have totally changed the faces of many instruments and the type of algorithms that are used in processing the resulting data. High-resolution imaging systems and multiple measurement modalities for characterizing a flaw have emerged. Interest is increasing not only in detecting, characterizing, and sizing defects, but also in characterizing the materials. Goals range from the determination of fundamental microstructural characteristics such as grain size, porosity, and texture (preferred grain orientation), to material properties related to such failure mechanisms as fatigue, creep, and fracture toughness. As technology continues to advance, applications of ultrasound also advance. The high-resolution imaging systems in the laboratory today will be tools of the technician tomorrow.

Basic Principles of Ultrasonic Testing

• 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.