Phased Array Topics Introduction to Ultrasonic Phased Array

Phased Array

Topics Ø Introduction to Ultrasonic Phased Array Ø New Techniques Ø Industrial Applications Ø Advantages Ø Challenges Ø The Future

What is Phased Array? Ø Multi-element transducers and instrumentation Ø Electrically steer and/or focus ultrasound

How does it work ? Ø Transmission (Tx) Ø Elements pulsed at controlled time intervals Ø Control of beam direction and focusing Ø The delays are known as Tx Focal Laws Beam Steering Wave front formed by constructive interference between wavelets Beam Focusing

How does it work ? (cont’d) Ø Reception (Rx) Ø RF waveforms received by each element are delayed, then averaged Ø Delays used to align the signals = Rx Focal Laws • Ultrasound reflects from defect –Elements receive ultrasound at different times due to the different beam paths –Signals then aligned by electronic circuitry

How does it work ? (cont’d) Single point of focus What if the defect lies beyond the focus point ?

How does it work ? (cont’d) Solution = Dynamic Depth Focusing Focal Zone • Rx Focal Laws are modified for each element • Result = Extended Focal zone

How does it work ? (cont’d) Example - Dynamic Depth Focusing (DDF) Single Focus 25 mm Single Focus 75 mm Dynamic Focus 25 to 75 mm • Good Near Surface • Poor Near Surface • Good Near Surface • Poor Backwall • Good Backwall

Summary Ø Transmitted (TX) ultrasonic beams can be electronically steered and focused Ø Received (RX) ultrasound can also be steered and focused Ø Focussing over an extended range, not only at a single point = Dynamic Depth Focusing

New Techniques

Sectorial scan Multiple Focal Laws ØBeam is swept through many angles ØWide coverage of the specimen Side Drilled Holes Backwall

Electronic / Linear scanning ØEach PRF cycle ØAperture moves through the length of the array ØNo raster movement required ØFull volumetric coverage achieved Each PRF cycle ØAperture moves through the length of array ØNo raster movement required ØFull volumetric weld coverage achieved

Linear scanning ØPhysical scan movement in one axis only ØFull axial weld coverage achieved

Industrial Applications

Corrosion mapping - Aircraft Lap Joins • Probe with flexible membrane – rides over rivets –detects corrosion under lap joints

Corrosion detection – inaccessible areas Inspect area under reinforcement plate Defect Geometry Reflections

Composite testing – Aircraft structure Composite Structure Honeycomb Core Disbond

Pipeline inspection – Zone Discrimination (AUT) Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 • Weld zoned - inspect with focused waves from both sides. (Up/Down stream) • Fast, reliable weld inspection (ASME/ASTM/API compliant) • Mechanics simpler & more reliable –Conventional UT = 1 probe per zone –Phased Array = 1 probe covers all zones

Pipeline inspection (Cont’d) Recording Threshold Shaded area shows TOF Colours indicate Above / Below Acceptance thresholds Amplitude Data from Up-stream Chanels Data from Threshold Down-stream channels breaking defects.

Pipeline inspection (Cont’d) Automated scanner incorporates TD Handy-Scan. RX TD Focus-Scan mounted In vehicle

Complex geometries - Turbine blade root

Advantages Ø One transducer covers many angles (improved coverage) Ø Increased inspection speed Ø Can produce Compression or Shear waves Ø Greater resolution (improved flaw sizing) Ø Much improved signal to noise ratio Ø Increased penetration & sensitivity Ø Improved POD Ø Focus control (point & ddf) Ø Improved visual representation (imaging)

Challenges Ø Array footprint can be large Ø Probe cable, very delicate Ø Application / equipment set-up can be complex Ø Trained / experienced personnel Ø Applied application information

The Future of Phased Array Inspection Ø Cheaper, faster, smaller instrumentation Ø More qualified/experienced personnel Ø Improvement of Codes & Standards Ø Wider application of phased array UT Ø Tools for application simulation

Thank you for your attention