Introduction to Phased Array Using the OmniScan MX2 - Part One

OmniScan MX2 Training Program
Introduction to Phased Array Using the OmniScan MX2

Part 1
Please send questions and comments to: PhasedArraySupport@olympusndt.com

Introduction to Phased Array Using the OmniScan MX2 Part 1 - Overview
Ø  Supporting documentation for the training program comes primarily from the MX2
software manuals and the Olympus reference manuals below.
Ø  Modern phased array systems like the MX2 do not require an advanced knowledge
of mathematics or acoustic theory and the training program focuses on practical
explanations and real world application examples for the working inspector.
Ø  Supporting theory, mathematical formulas, and more advanced PA concepts can be
found in the books below available from the ONDT web site.
Ø  These manuals can be downloaded at http://www.olympus-ims.com

Introduction to Phased Array Using the OmniScan MX2 Part 1 - Overview
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Phased array calculators differ in functionality and complexity as a result of
supporting different types of probes, wedges, and applications.
The most simple or complex phased array calculators can generally be divided into 4
specific sets of parameters:
§  Probe parameters.
§  Wedge parameters.
§  Material parameters. (Velocity)
§  Focal law beam formation.
3 parts hardware and 1 part software to generate the focal laws.
For proper formation of the focal laws, all hardware parameters must be configured
correctly, and the beam formation requested must be within the limits of physics, the
hardware, and the instrumentation.

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Introduction to Phased Array Using the OmniScan MX2 Part 1 - Probes
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1D Linear array probes are the most widely used for industrial inspection and the
only type that is supported directly in the OmniScan MX2 software wizards.
Phased array probes other than 1D linear must use focal laws generated from an
external calculator for import into MX2.

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Ø 

1D linear array probes are defined by the following parameters.
§  Size or “Pitch” of the elements. (.25-2mm)
§  Number of elements. (8, 16, 32, 64, 128, 256)
§  Frequency. (1-17 MHz)
§  Radius focused or flat.
§  Reference point. (Only required for use without wedge and does not affect PA
calculator)

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OmniScan MX2 Training - Group Setup Wizard - Probe Selection
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The MX2 will read the following
information from the chip in the
connector of Olympus probes when the
probe auto detect is on:
§  Probe Model.
§  Probe Frequency.
§  Probe Element Quantity.
§  Probe Element Pitch.
§  Reference Point.
§  Serial Number (Not displayed).
With auto detect off, custom and probes
from manufacturers other than Olympus
can be entered and saved in the MX2
database.

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Ø 

Complex probes and wedges such as 2D or TRL type arrays or complex techniques
such as pitch-catch require more input parameters and must be generated with a
computer based phased array calculator and imported into the OmniScan MX2 on
the memory card.

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Ø 

The dimensional parameters of a 1D linear phased array probe are defined
as follows:

A = Aperture. Total length of all elements in active plane. (Pitch X
element count)
H = Element height in the passive plane. Also called element elevation.
P = Pitch. Center to center distance between two adjacent elements.
E = Size. The width of an individual element.
G = Gap. The spacing between two adjacent elements.
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Ø 
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Olympus probes are sold with common housings to minimize the amount of
wedges and accessories.
Below is pictured a standard 5L64-A2 probe that uses the same housing as the
2.25L64-A2. All A2 probes are compatible with A2 wedges and are listed in the
OmniScan MX2 database independently to account for different pitch and
position.

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Ø  Universal probes such as A10, A11, A12, And
A14 are designed for hand scanning or
automated inspections for a wide range of
applications including weld inspection and
corrosion monitoring.
Ø  Pitch and frequency makes these probes ideal
for thicknesses in carbon steel up to 100mm*
for new construction and in-service inspection.
Ø  Specific scanner adapters for automated
inspections and low profile wedges to reduce
the need for diameter contouring and improve
stability.

*Depending on acquisition module i.e. 32:128

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OmniScan MX2 Training –– Pipeline Weld Probes for use with MX2
Ø  Pipe Wizard probes such as the
PWZ series are the workhorse of the
Olympus pipeline phased array
systems.
Ø  Typical applications include high
speed precision inspection using
zone discrimination and amplitude
techniques on pipeline girth welds.
Ø  Suitable for manual and automated
inspections.
Ø  Specialized wedges used with the
PWZ include carbide wear pins and
sophisticated irrigation channels.
Ø  Internal radius focusing for improved
length sizing of pipeline flaws.
(Sharp C-scan and B-scan)
Ø  Short cable and front cable exit
available for scanner
accommodation.
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5L32-PWZ3 probe used for piping inspection.

Ø  Deep penetration probes such as the
A3, A4, and A5 are designed for
heavy wall inspections and coarse
grain materials.
Ø  Typical applications include the
inspection of large plates, castings,
and forgings where maximum
penetration and power is needed.
Ø  Large element pitch and elevation
with low frequency options make the
deep penetration probes ideal for
stainless steel and course grain
material inspection over long sound
paths.

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Ø  Probes for the Olympus Cobra scanner
and other tight clearance scanners are
optimized for the small piping diameter
inspection.
Ø  The Olympus CCEV probes have an
internal radius of 35mm and are suitable
for thickness range of approximately
4-25mm.
Ø  Have a low profile element design and
when used with the Olympus Cobra
scanner system need only 12mm pipe to
pipe clearance.
Ø  Are available in a range of frequencies
for carbon steel and austenitic material
inspection.

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Ø  Olympus immersion probes are designed
to be used with a water wedge or in an
immersion tank.
Ø  Typical application include thin plate or
tubing inspection, composite inspection,
inline thickness testing, and any
immersion application.
Ø  They are longitudinal wave probes that
can be set up for refracted angle shear
wave inspections using a wedge or
water.
Ø  Acoustic impedance matches water.
Ø  Linear scanning allow coverage of
30-90mm in one line.
Ø  Corrosion resistant steel casing and
waterproof up to 1meter under water.
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Ø  Designed to be used with the OmniScan MX2,
Olympus offers 4 different housing types with
compatible wedges for shear and longitudinal
wave inspection of stainless and carbon steel
power piping.
Ø  1.5 - 5 MHz Frequency and a range of pitch and
apertures for manual crack detection and sizing.
Ø  Small footprint wedges and ergonomic probe
casings for hand scanning and access in small
spaces and on small diameters for precision
measurement.
SS304 2mm SDH depth of 38mm

SS304 2mm SDH depth of 6mm

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SS304 ID notch - 68mm X 33 inch diameter.

Ø  Typical applications include inspection of
carbon fiber reinforced polymers (CFRP)
corners for composite delamination.
Ø  Acoustic impedance of water.
Ø  Corrosive resistant stainless steel casings
waterproof up to 1 meter.
Ø  Full line of adjustable immersion wedges.

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Introduction to Phased Array Using the OmniScan MX2 Part 1 - Wedges
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Phased array wedges perform the same function as conventional UT wedges by
coupling sound energy from the probe to the material at the desired refracted angle
and wave type.
Phased array wedges come in all shapes and sizes for various applications and are
an essential part of the inspection process.
Phased array wedges are used to assist the probe in beam formation for shear
wave and longitudinal wave inspections, just like UT.
1D probe wedges typically used in OmniScan MX2 applications come in 3 varieties:
§  Shear wave angle beam.
§  Longitudinal wave angle beam.
§  Longitudinal wave straight beam.

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Some housing types can accommodate probe models of different pitch size and
frequency, and may not be symmetrical in the housing.
Wedges compatible with these types of probes contain separate probe position
options with separate attachment points including reversing the probe.
Care should be taken to ensure the correct probe, wedge, and wedge position
are selected from the wedge database.

A2 Housing
5L64
Position

2.25L64
Position

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Included in the wedge label after the housing family (SA10, SA12, etc.) is the
nominal refracted angle (N60S) in steel with no beam steering.
To achieve a shear wave refracted angle of 60 degrees (N60S) in steel the wedge
is cut with an incident angle of 39 degrees in Rexolite. (Snell’s law)
N55 and N60 are common wedge designs because this angle allows good beam
steering from approximately 30-70 degrees for most probeswedge combinations.

39 degrees in
Rexolite

60 degrees in
carbon steel

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A zero degree wedge is designed for both straight beam and angle beam
longitudinal wave inspection as is typically used in corrosion mapping or composite
lamination type inspections.
This type of wedge acts as a stand off delay and provides improved near surface
resolution compared to using a probe with no wedge.
The 0L wedge also protects the probe as scanning with no wedge exposes the
probe membrane to wear and damage.

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Ø  Wedge coupling is essential for a good inspection and where the wedge is too large
to properly mate against the material, sound is impeded and the wedge must be
contoured.
Ø  The 3 most common types of wedge curvature for optimization of a particular
component, pipe or vessel inspection are:
1.  Flat
2.  AOD## (Axial Outside Diameter Curvature + Diameter)
3.  COD## (Circumferential Outside Curvature + Diameter)

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Ø 
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Inspection in the circumferential axis or “Long seam” type inspection requires a COD
wedge and special hardware and software considerations.
COD wedges are calibrated at the factory for precise incident angle to be used in the
focal law calculator. Each wedge is treated independently for precision.
The COD inspection for the OmniScan MX2 requires that the focal laws be built
externally with a computer based calculator like Tomoview and imported into the
OmniScan MX2 for use.

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Ø 
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The Hydroform corrosion mapper is a form of a specialized phased array probe and
wedge using water as the coupling medium.
It uses a stable water column with an adjustable probe height to transmit sound into
the component for corrosion inspection and C-scan generation.
The Hydroform wedge parameters for the phased array calculator are selected
directly from the database in the MX2 software and use the velocity of water.
The benefits of using water as the wedge include improved component coupling and
improved near surface defect resolution.

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Ø  In this example the phased array wedge was manufactured to the same
taper as the component for a perfect fit.
Ø  Custom wedges than cannot easily be defined by the phased array
calculator have inherent limitations. The ability to calibrate wedge delay and
sensitivity requires a custom calibration block and precision beam steering
and focusing is reduced.
Ø  The inspection below is for cracks using an amplitude C-scan and metal loss
using a position C-scan.

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Ø  A 20mm 0 degree Rexolite wedge is a common design and will put the wedge
interface echo at 50mm of the component when using carbon steel velocity (5980m
sec).
Ø  The primary offset (-56mm) represents the position of probe element #1 in relation
to the front face of the wedge in the primary axis.
Ø  The wedge is selected from the data base that includes standard Olympus wedges
and ability to create custom entries.


Ø  The following parameters
are required for the
OmniScan MX2 wedge
database and phased
array calculator:
–  Wedge model.
–  Wedge angle.
–  Wedge orientation. (Normal
or reverse)
–  Height of element #1 of the
probe (h1).
–  Wedge material velocity.
–  Primary and secondary
offsets (x,y).

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Ø  Every wedge from Olympus is delivered with a wedge specification data
sheet that contains all of the parameter values to populate the OmniScan
MX2 database or external focal law calculator. These values are relative to
the probe and its orientation on the wedge. For that reason one wedge may
be listed many times in the database.

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Introduction to Phased Array Using the OmniScan MX2 Part 1 - Velocity
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The only component material parameter that is
required for the phased array calculator is the
velocity of sound for shear wave andor
longitudinal wave transmission.
The OmniScan MX2 software contains a
database with common material types and their
velocities.
The material type and shearlongitudinal are
normally selected during the wizard group
creation as part of the setup process.
Custom velocities can be entered manually as
needed in the UT settings sub menu and can be
measured using the velocity calibration wizard.
The material velocity must be known prior to
focal law creation. The velocity cannot be
modified in the MX2 without recreating the focal
laws.
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Intro to Phased Array Using the OmniScan MX2 Part 1 – Beam Formation
Ø  A focal law is the pattern of time delays applied to pulsing and receiving elements of
an array probe in order to steer and focus the resulting sound beam and echo
response.
Ø  The speed or PRF, the quantity of A-scans in one or more groups, and the type of
beam formations possible is limited by instrument specifications and software
capability.

Single pulse echo focal law example
Software input

Transmitter delays (Pulse)

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Receiver delays (Echo)

Resulting A-scan

Ø  A simpler explanation is that a focal law is an A-scan. When used in pulse echo
mode the transmitted and received delays are the same and are using the same
group of elements.

Ø 

The phasing affect allows multiple focal laws or A-scans that differ in angle and focus
to be generated from the same group of elements and summed in a sector scan or
linear scan type display.

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Sector Scan Definition

Linear Scan Definition

§  Focal laws of different angles
generated using the same elements.
§  A-scan density and coverage is
defined by the range of angles
(45-70) and angle resolution. (45, 46,
47, etc)

§  Focal laws generated over a series of
elements using the same angle.
§  A-scan density and coverage is
defined by the element step
resolution.

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Ø  Sound beams can be focused like light rays with the energy focusing at a given
point and then expanding beyond it.
Ø  The depth of focus is changed by varying the applied delays on the elements and is
built into the focal law along with the angle steering.
Ø  The maximum depth or sound path that a beam can be focused is defined by the
near field which is a function of element size, frequency, and material velocity.
Ø  The effective sensitivity is improved by a smaller beam diameter with more energy
at the focus point.
Ø  Increasing the size of the aperture or creating the same aperture using more
smaller elements increases the sharpness of the focused beam and improves
results.

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Ø 
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Beam focusing is only possible within the near field of the probe.
The near field is different in the active and passive axis of the array and can be
calculated with the formula below.
Most methods for calculating the near field should be considered close
approximations due to simplifying the formula and not taking into account every
probe parameter.

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Ø  Different focusing strategies can provide optimized results for different
applications.
Ø  There are five primary types of focusing associated with phased array
inspection:
1.  Depth focusing. Defined from the bottom of the wedge in depth and different
for every angle.
2.  Sound path focusing. Defined by the uncorrected sound path and the same for
every angle.
3.  Projection focusing. Defined by the surface distance from the wedge face.
4.  Focal plane focusing. Defined by an X,Y position in the material.
5.  Unfocused. Any value that is beyond the near field of the probeaperture.

Depth

Sound Path

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Projection

Focal Plane

Ø  In addition to standard IIW and similar calibration blocks, there are industrial
standards such as ASTM E2491 that specify techniques and calibration
block designs for verification of the phased array beam profile.
Ø  Beam profile, beam steering limits, beam focusing, element activity, etc can
be verified similarly to the requirements of conventional UT with specialized
reference standards.

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OmniScan MX2 Training – Phased Array Calculator Review
Ø 

Question: What are the four groups of essential parameters for the
phased array calculator?
1. 
2. 
3. 
4. 

Probe parameters.
Wedge parameters.
Material Velocity
Beam Formation.

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Thank You!

Please send questions and comments to: PhasedArraySupport@olympusndt.com
For more information visit our website: www.olympus-ims.com

Introduction to Phased Array Using the OmniScan MX2 - Part One

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Introduction to Phased Array Using the OmniScan MX2 - Part One