2018

ULTRASONIC TRANSDUCERSFOR NDTIMMERSIONTOFD
PHASED ARRAYCONFORMABLE

Designer & manufacturer since 1989

SUMMARY

Context3

Small footprint linear array transducers 28

IMASONIC Overview

4

Low profile linear array transducers

29

IMASONIC’s NDT offer

5

Matrix array transducers

30

Transducers Key components

8

Annular array transducers

33

Bandwidth or pulse length ?

9

TRL array transducers

34

Coupling method

10

Conformable array transducers

36

Immersion single elements

12

Smart ConformableLinear Arrays (1D)37

Design notes

13

Smart Conformable
Matrix Arrays (2D)

38

NEW: Transducers
with conformable wedge

38

Curved Linear Array Transducers

40

Daisy Array Transducers

41

Advantages of piezocomposites
for immersion transducers
IM transducers

14
14

Enhanced focusing - Fermat concept 15

TOFD Transducers

16

Phased array coupling solutions

42

Standard TOFD series

17

Info: Plexiglas or Rexolite?

43

Extra-flat TOFD for CRD inspection

18

Phased array connection solutions

44

TOFD transducers for tube inspection 19

Phased array principle

46

Custom TOFD transducers

19

Phased array design notes

48

Phased Array transducers

20

And more

50

Acoustic solutions forphased array probes

22

Linear array transducers for steering

24

Linear array transducers for scanning 26
Info: pre-focused arrays27

3

Context
Non Destructive Testing (NDT) based on ultrasound is the use of ultrasonic waves to detect, locate andcharacterize defects in materials, components and assemblies. This technique has evolved enormously overfifty years and changes have been particularly rapid over the last twenty years.
Other NDT techniques (X Rays, Eddy Currents, Visual Inspection, Thermography, etc) complement
ultrasonic techniques. Whichever technique is used, the purpose is to ensure that the materials,
components or structures are of a satisfactory quality.
The evolution of the performance requirements of NDT has been determined by developments in quality requirements.
The history [1] of the development of these techniques has thus been marked by the evolution in theobjectives of inspections: the "zero defect" objective of the 1960s was replacedin the 1970s by the objective of detection of "critical defects", followed in the 1970s-1980s by theobjective of improving the detectability of defects.
It should be noted that the term Non Destructive Evaluation (NDE) has developed for this evolution
towards the characterization of defects.
The 1980s-1990s were then marked by the objective of continuous and improved NDTof the systems and structures that are subject to ageing.
In the 1990s-2000s appeared the needs to inspect very large areas, to monitor continuously the healthof certain structures through Structural Health Monitoring (SHM), and, at the same time, to reduce thecost of inspections and other evaluations.
The quality requirements behind NDT techniques is currently centred on establishing the key parametersof dimension, shape, orientation and detectability of defects.
In the light of these objectives, the development of the performance of NDT systems plays anessential role in connection with the development of science and techniques in the related fields of material
physics, design of components and structures, analysis of the constraints in the life of components
and structures, fracture mechanics, reliability evaluation, economic demands, etc.
The techniques of NDT based on ultrasound is gaining interest for several reasons:- they can be implemented without risk to operators or to the environment- they can be used on an extremely large range of different materials and at a wide range
of depths of use- they have improved their performance, flexibility and speed through the Phased Arraytransducer concept and through progress in modelization, microelectronics and microcomputing.
For more than twenty years, IMASONIC has been contributing, with their customers and theirpartners, to the constant evolution in the techniques of ultrasonic NDT.
With piezocomposite technology, we have been able to increase, in particular:- the performance in sensitivity- the focusing capacity (without lens, including aspherical)- the feasibility of custom-designed and custom-manufactured Phased Array transducers,in order to adapt the performance to the needs of each application
This progress continues with the development of conformable solutions to improve the conditions of inspection for many components.
[1] cf: D.O. Thomson “Evolution of QNDE’s Core Interdisciplinary Science and Engineering Base” in Review of quantitative
non destructive evaluation - vol 29.

4

IMASONIC Overview
IMASONIC is an independent, privately-owned company that develops and produces
ultrasonic transducers for high socio-economic added-value applications.
IMASONIC's vocation can be summed up as follows:- to act for the benefit of man and his environment, in particular in the interestsof health, safety and quality- to advance the profession of designer and manufacturer of ultrasound transducers
and to do this creatively, innovatively and productively- to increase recognition of the company and its leading position through the qualityof its relationships with customers and partners.
IMASONIC's vocation can also be seen in the willingness to collaborate over the long termwith its customers and partners.
IMASONIC is ISO9001: 2015 certified.
80% of the total turnover is exported to all five continents.
Around 67% of the total turnover is dedicated to safety and quality applications, mainly for
Non Destructive Testing and industrial measurement.
Customers for NDT transducers and probes are end users, service companies, equipment
manufacturers and laboratories.
The main applications for NDT are: power generation, aeronautics, car industry, railways,
petrochemicals and metallurgy.
Located in the east of France, close to Switzerland, in a region famous for its microtechnologies
and watch industry, IMASONIC is founded on the skills of its team of 105 employees (2018).

5Transducers for ultrasonic NDTThe IMASONIC offer
The wide variety of NDT applications and methods leads to a great range of needs.
Over 30 years, IMASONIC has acquired considerable experience in the demands of NDT,
and can offer the capacity to design and manufacture transducers adapted to this variety.

A transducer adapted to each application
IMASONIC offers customers its team’s expertise and its design capacity to define with them
the appropriate transducers for their applications. This service includes, in particular, feasibility
studies associating simulation and/or prototyping. In addition, IMASONIC can also provide
customers with access to their partner network of specialists for associated needs related totransducers.

"Customized" transducers
Some NDT needs require the development of transducers dedicated to a target application.
IMASONIC proposes the production and characterization of "made-to-measure" transducers,
defined according to detailed specifications.
IMASONIC's piezocomposite technology has a very large capacity for adaptation to the mostvaried needs. Over thirty years, IMASONIC has developed a high level of expertise in providing
for these types of needs.

"Standard" or "near-standard" transducers
Other NDT needs may be met with transducers whose design may be described as "standard"or "near-standard". For these needs, IMASONIC has developed a technological platform where,
in a large number of cases, certain parameters on a predefined design base can be adapted.
This approach offers very competitive prices and rapid delivery, while still offering a high levelof quality, reliability and reproducibility.

Quantities
IMASONIC's industrial and commercial organisation is able to respond appropriately
to requirements from just a few units up to production runs of several thousands of units.

6

IMASONIC's commitments
In a context where the technical and economic performance stakes are high,
IMASONIC makes the following commitments:

Quality
In order to provide the most appropriate response for the performance requirements,
IMASONIC undertakes to seek from the customer the specific needs for each application.
In seeking the highest quality, we also propose and implement solutions adapted to thedifferent development stages, from feasibility studies to finished products destined forindustrial applications with reproducibility requirements.

Standards
IMASONIC undertakes to identify with its customers the requirements that apply to thetransducers. IMASONIC’s commitment is also demonstrated through their contribution to workon establishing industry standards.

Transducer specifications
IMASONIC undertakes to collaborate closely with its customers to identify the essential
requirements, conformity criteria and verification conditions (tests and measurements).
On delivery, these specifications are completed by recommendations on conditionsof integration and use, to reduce any risks linked to an inappropriate use of the product.

Characterization
IMASONIC undertakes to verify conformity to essential requirements and acceptancecriteria through tests and measurements. A formal report presents the results.
IMASONIC also undertakes to offer characterization solutions that are reproducible
and connected to the appropriate standards where they exist.

Reliability and durability
IMASONIC undertakes to collaborate with its customers to identify any risks of failurefrom the viewpoint of conditions of integration and use, and to check the reliability ofthe products in their using conditions.

Confidentiality
IMASONIC takes all necessary steps to protect the confidential information of its customers
from unauthorized disclosure or use and thus to protect their interests.
In particular, this commitment can be formalized by signing non-disclosure agreements.

7

AlertsIMASONIC undertakes to alert its customers if any uncertainty arises regarding therelevance of a study or a manufacturing process in connection with the reliability ofa transducer or the safety of its use.

8

General Technical information
Transducers key components
Piezocomposite material
Specially designed piezocomposite structure is inserted in each type of probe.
The composite components and geometry are defined according to the temporaland frequency response specifications, while retaining high sensitivity and signal-to-noise
ratio level.
For phased array probes, the piezocomposite structure is also designed to lower
the cross-coupling between elements, which is necessary to properly steer the beamwith electronic delay laws. Typical cross-coupling is lower than –30dB.

Matching layers
Taking into account the conditions of use of the probe (manual, automated, direct contact,
contact with a wedge), the matching layer is designed to optimize the transfer of energy,
to shorten the pulse width and to protect the piezocomposite.

Backing material
The backing material is designed to shorten the pulse width and to attenuate the back echo.
Specially-designed backing materials allow an interesting trade-off with high damping
and high attenuation in reduced dimensions.

Housing
The housing is designed to combine the required geometry with the strength
and watertightness of the probe. It can be adapted to mechanical or manual use.

Cable
Performance of the cable is also a key parameter for the overall performance of the probe.
Its attenuation must be as low as possible, in particular for high frequency probes.
Its electrical impedance is matched with the probe and electronic characteristics.
The bending capability is optimized to access small areas, while keeping high mechanicalresistance and constant electrical properties.

Connector
The connector is most often defined by the electronic system the transducer will be connected to.
However, it must be adapted to handling and environmental constraints (frequency of handling,
immersion, vibrations, etc), while guaranteeing consistent quality for the electrical contacts.

9Technical Information
Bandwidth or pulse width?
The bandwidth of the probe is generally one of the main specifications.
However, it is often specified instead of the pulse width.
When the bandwidth has a Gaussian shape,
it is closely linked to the pulse widthand specifying the bandwidth is enoughto get the pulse width. However, when
the shape of the bandwidth is not Gaussian,a rather long pulse can be obtained,
as well as a bandwidth of more than 100%.
Some applications really require bandwidth,for example, when the received signal
is significantly shifted to the low frequencies
due to the attenuation of the material,or for harmonic imaging.
Most applications actually require axial
resolution using a short pulse widthand in this case it is more appropriate
to specify the pulse width than the bandwidth.
In addition, the pulse width and bandwidth
largely depend on the driving signal,
the electrical impedance and the environmentof the pulsers.

IMASONIC probes are optimized for and measured with a negative square pulse
with a length of T/2.

See also new acoustic solutions for phased array probes page 22.

10

Coupling method
Immersion
The transducer and the inspected piece are immersed in a vessel, and the couplingof the ultrasonic beam is done by the liquid, usually water.
This method provides the highest level of acoustic performance due to the constancyof the coupling and to the low ultrasonic attenuation in water, with proper management of
unwanted bubbles.
It allows working with complex geometry parts, and many types of transducers, including
curved ones, with no other dimensional constraints than those related to the vessel itself.
This method is cumbersome to implement and maintain in case of large components. It also
implies the compatibility of inspected parts and the possible mechanical scanners with
the immersion. It is not compatible with manual use.
The immersion is sometimes confined in a local water box positioned at the control location,
thus reducing the size of the equipment. The immersion can also be implemented with water
jets (squirters) in which the ultrasonic beams are guided. They require delicate tuning
and are reserved for probes of relatively small dimensions. In both cases, a waste water
management is necessary.

Contact with wedge
A mechanical part, generally in rigid plastics material, enables the ultrasonic coupling
between the probe and the inspected object. A fluid couplant is required at the probe-wedge
and wedge-component interfaces.
This method does not require equipment such as a water tank, it is quick and inexpensive
to implement, and is compatible with manual and automated inspections.
However wedges reduce acoustic performances compared to immersion• Attenuation is higher than in water, and the signal loss becomes sensitive beyond 5MHzand very critical beyond 15 MHz• The wedge-probe and wedge-component interfaces create disturbances that degrade
the signal if the thicknesses of couplant are not perfectly homogeneous or if the surfaceof the component is not regular.
The wedges are easy to implement for planar probes and flat or cylindrical components
interfaces. They are difficult to implement with curved probes or with inspected components
having complex or variable geometry.
Integrated wedges
An integrated wedge allows a transducer to be more compact and often
better adapted to industrial conditions. The coupling between the active
part and the wedge is guaranteed by being glued during manufacturing.
Thus it is constant and homogeneous, requires no maintenanceand guarantees a high level of performance.

11

Removable wedges
Removable wedges have great flexibility and enable the same transducer
to be used in several different configurations. They can also be replaced
easily if they show wear or are damaged.

Contact with conformable wedges - NEW - patent pending
A flexible and robust membrane filledwith water is fitted between the probe
and the piece to be inspected, to ensure
the transmission of ultrasound by combining
the advantages of the immersion
and contact with a wedge.
• The coupling is possible on parts with variable
or complex geometry• The acoustic performance is similar to immersion,
thanks to transmission through waterand acoustically invisible membrane.
• Manual and automated use are possible,
in similar conditions to those of conventional wedges.
• A wide range of probes can be used, including linear
and matrix arrays. Their active part can be formed.
See transducers with conformable wedges page 39.

Exemple of transducer
with conformable wedge

Direct contact on inspected part
In some cases, contact transducers can be used without a wedge, for example, if there is
not enough space available, or to avoid interference echoes from the wedge.
In this configuration, the unseen area below the surface is larger because of the ringing
of the excitation signal. Furthermore, deflection without grating lobes at high angles will
require smaller spacing, and consequently a larger number of elements.
Finally, in this case, shear waves with mode conversion between the wedge
and the part to be inspected cannot be generated.
Hard face
Wear and tear on the front face may have unexpected effects on probes, such as water
penetration or modification of electroacoustical properties.
Conversely, placing a protective layer may alter the pulse width and sensitivity due to theadditional interface.For this reason, IMASONIC has implemented a new hard face material
that combines appropriate acoustical impedance for high energy transfer and ten times
higher resistance to wear than a conventional front face. See Wedges page 44.

12

Immersion single elements
Applications
Automated inspection of various parts and materials:- Tubes, bars, plates inline inspection- Pipeline- Machined and forged parts- Metals, composite materials, ceramics, plastics, etc.

General Characteristics*• Piezocomposite• Acoustically matched to water• Centre frequency (-6dB): from 200 kHz to 20 MHz• Active area from 1mm to 300mm• Relative bandwidth (-6dB): 60 to 90 %• Circular or rectangular active area
• Flat or focused active area
• Watertight stainless-steel housing• Connector or integral cable

Options*• Spherical, cylindrical, or aspherical (see page 15) focusing• Temperature up to 150°C in continuous or 180°C over short periods• Pressure up to 600 bars
• Compatibility with chemical agents, oil, sea water• Halogen-free• Nuclear radiation withstanding* Some combinations of active size, frequencies, focusing and options may not
be feasible.

13

Design notes for immersion transducers
Online design
On this page of our website, you can do
an on-line simulation of the main characteristicsof the ultrasonic beam for circular immersion
probes, according to the frequency, the active
diameter and the focus.
www.imasonic.com
Search for Online Design

Valid for flat circular transducers

D24

Near field distanceN=

Half angle of divergencesin  = K 
DBeam diameter at near field
distance for flat transducer

D = active diameter
= wavelength
K = 0.51 for -6dB drop
K = 0.87 for -20dB drop

W (-6dB) = 0,26 . D

TRANSDUCETRUSIMMERSION TRANSDUCERSIMMERSION

Useful formulas

14Technical Information
Piezocomposite advantages for immersion transducers
Very high sensitivity
The acoustic impedance of IMASONIC piezocomposite materials can be adjusted fromapproximately 10 to 15 MRay. This impedance, much lower than that of ceramics, is closer tothat of water. This results in a better energy transfer which, combined with high electro-acoustic
efficiency, gives a sensitivity that is 10 to 32dB higher than that obtained with monolithic
piezoelectric ceramics.

Focusing by shaping
Thanks to IMASONIC technology, the shaping of the active area
enables the beam to be focused without resorting to using a lensthat absorbs some of the energy and only gives an approximate
focus because of the phenomena of aberration.

IM transducers• IMASONIC Piezocomposite technology• Spherical focus on request• Straight connector or integral cable• Connectors: UHF, BNC, Lemo, Microdot

Centre frequencies available (MHz)
10

19.3

15

25 - 38.9

5

16

7.5

3

3.5

Knurled ring
diameter
(mm)

2.25

Housing
length(mm)

1

Housing
diameter(mm)

0.5

Activediameter
(mm)

6

16

25 - 38.9

19.3

10

16

25 - 38.9

19.3

13

16

25 - 38.9

19.3

19

25.4

32 - 38.9

27

25

35

38.9

36.5

29

35

38.9

36.5

38

44.5

38.9

46

Standard configurations

15

Enhanced focusing - FERMAT concept
Applications
Inspection of critical components and detection of tiny defects.
• Multizone billets inspection• Thick plates inspection• Heavy forged parts inspection• Nuclear vessel inspection

Principle
The aspherically-focused active area is calculated to obtain the best focusing
effect at a given location in the material with a given refracted angle,
through a flat, cylindrical or toric interface.
Moreover, a large transducer aperture combined with Fermat concept allows
very high lateral resolution and signal-to-noise ratio.
It is typical used in immersion with pulse echo technique, but can also be
used in contact with a delay line.

Advantages• Very high resolution and signal-to-noise ratio• Beam profile very close to simulation thanks to IMASONIC
piezocomposite technology• Fermat concept may be implemented on phased array probes, allowing
flexible high-resolution beam focusing and beam scanning

Main Characteristics

Options• Custom wiring (cable length, type or positioning, Connector type)• Housing adaptation to mechanical set-up (probe holder, wedge, etc)
• Adaptation to environnemental contraints (Temperature, pressure,radiation, vibration, etc)

IMMERSION TRANSDUCERS• IMASONIC piezocomposite FERMAT technology• Centre frequency (-6dB): from 1 MHz to 15 MHz• Relative bandwidth (-6dB): 60 to 90 %• Acoustic impedance matched to water or delay line
• Watertight stainless steel housing

16

TOFD Transducers
Typical Applications• Weld inspection, steel components• Detection and sizing of cracks

Principle
Using the TOFD (Time Of Flight Diffraction) technique, cracks are detected, sized
and monitored, irrespective of their type and/or orientation, by using the diffracted
sound initiating from the flaw tips.
Two transducers are used to transmit and receive.
The beam divergence is enough to cover the whole thickness of the inspected part,which is displayed between the lateral wave (surface) and the back-wall echo.

Advantages• Possibility of detecting and sizing the defects• Reduced dead zone
• Fast technique

General Characteristics• IMASONIC piezocomposite technology• Nominal frequency from 1 to 20 MHz• High resolution/sizing capability because of a short pulse width• Very high sensitivity/detection capability• High reliability over time thanks to a design that is watertight and resistant to corrosion,compatible with permanent immersion under a metre of water

17Standard TOFD series• IMASONIC piezocomposite
technology• High sensitivity• Short pulse width• Designed for field conditions• Standard housing

Recommended configurations according to
NF EN ISO 16828 standard
Activediameter(mm)

Thickness <70 mm

Thickness 70-300 mm

Depth
(mm)

Angle (°)

Depth
(mm)

2

6

30<70

45-60

-

-

2

12

30<70

45-60

100<300

45-60

T0306

3.5

6

30<70

45-60

30<100

45-60

T0503

5

3

10<30

50-60

<10

50-70

T0606

5

6

10<30
30<70

50-60
45-60

<10
10<30

50-70
45-60

T0512

5

12

30<70

45-60

30<100

45-60

T0706

7.5

6

10<30

50-60

<10

50-70

T1003

10

3

T1006

10

6

<10
10<30

50-70
50-60

<10

50-70

T1503

15

3

<10

50-70

-

-

IMASONIC
Ref.

Nominalfrequency
(MHz)

T0206
T0212

Angle (°)

Active Ø

Housing type

Housing diameterand length (mm)Thread type(mm)

Connector

3-6 mmStandard

Ø 9.5 x L 30

M12 X 1.75

Lemo 00

3-6 mmShort

Ø 9.5 x L 20

M12 X 1.75

MCX

12 mm

Standard

Ø 17 x L 29

M20 X 1.5

Lemo 00

Options• Standard TOFD wedges (45°, 60°, 70°)
• Integrated cable• High-pressure resistance for offshore application• Compatibility with oil and chemical agents• Compatibility with high temperature

T.O.F.D. TRANSDUCERS

Transducer types

18

Extra-flat TOFD for CRD* inspection* control rod drive

Application
Reactor vessel cover penetration tubes inspection..

Principle
The very low thickness of the probes, combined with their curvature,
allows them to be inserted between the control bars and the guide tubes.
The transducers can thus inspect the guide tube and peripheral welds ( Jweld)
in TOFD mode.

The orientation of the transducers enables longitudinal or circumferential
defects to be detected.

Advantages
Inspection feasibility, sensitivity, bandwidth.

General Characteristics
These transducers are adapted individually to the inspection constraints,
and in particular to the handling, plating and coupling mode.
• Thickness < 2.5 mm (down to 1.5 mm)• Nominal frequency: 4 to 5 MHz• Adjustable PCS (Probe Center Spacing)• Refracted angle range: 45 to 70° LW• Radius of curvature: 70 mm (typical)• Longitudinal or circumferential orientation• Integrated cable

Options• Water distribution device for the coupling• Halogen-free• Mechanical plating solution• Mechanical guidance solution• Transducer at 0° for thickness measurement

19

TOFD transducers for tube inspection
Application
Internal inspection of tubes.

Principle
The cylindrical geometry of probes and their small possible diameter enable
them to be inserted into tubes for inspection from the inside in TOFD mode.
The orientation of the transducers enables longitudinal or circumferential defects
to be detected.

Advantages
Inspection feasibility, sensitivity, bandwidth.

General Characteristics
These transducers are adapted individually to the inspection constraints,
and in particular to the handling, plating and coupling mode.
• Diameter: down to 12 mm• Nominal frequency: 4 to 10 MHz• Refracted angle range: 45 to 70° LW• Longitudinal or circumferential orientation• Integrated cable

Options• see Options for Extra flat TOFD probes (page 18)

TOFD probes can be customized on request to meet the requirementsof your application. Some examples are:• Integrated miniature probes for small spaces / short PCS (probe center spacing)• Custom housing
Note: The TOFD technique is also compatible with phased array probes.
See phased array probes, page 20.

T.O.F.D. TRANSDUCERS

Custom TOFD transducers

20

Phased Array summary
Since 1989, IMASONIC has offered the widest range of phased arrayprobes for industrial applications.
• The standard phased array probes benefit from standardized designthat combines reliability, accuracy, performance and competitiveness.
• Customized phased array probes offer numerous possibilities for adaptation
to the most demanding applications.
Phased array transducers

21

Acoustic solutions for phased array probes

22

Linear array transducers for steering

24

Linear array transducers for scanning or for depth
Info: pre focused arrays

26
27

Small footprint linear array transducers

28

Low profile linear array transducers

29

Matrix array transducers

30

Annular array transducers

33

TRL array transducers

34

Conformable array transducers

36

Smart Conformable Linear Arrays (1D)37

Smart Conformable Matrix Arrays (2D)

37

NEW: Transducers with conformable wedge

38

Curved Linear Array Transducers

40

Daisy Array Transducers

41

Phased array coupling solutions
Info: Plexiglas or Rexolite?

42
43

Phased array connection solutions

44

Phased array principle

46

Phased array design notes

48

21

Phased Array transducers
Array types
Phased array transducers consist of several elements that can be activatedindependently (See Phased Array Principle, page 48). We have grouped thembelow according to the main types.

1D Linear array*

Curved linear array*(Concave or convex)

Focused linear array*

1,5D array*

2D matrix array*

Annular sectorial array*

Annular array*

Daisy array*

Circular array (convex)*
Encircling array (concave)* According to EN-16018

PHASED-ARRAYThis list is not exhaustive and other types of geometry of the elements that could be associatedwith shaping the active area (cylindrical or spherical, or aspherical prefocusing)offer a very wide feasibility field.

22

Acoustic solutions for IMASONIC
phased array probes
IMASONIC now offers four types of standard acoustic designs for its linear array probes.

How to choose?
Use in direct contact
with abrasive surface

Yes

Wear ResistantNo

VersatileYes

Dynamic

No

The probe is always
used with the same
coupling medium

Yes

Sensitivity and s/n ratio
are more criticalthan pulse durationNo

Accuracy

23

Versatile:
The acoustic design is matched to the coupling medium (water, plexiglas, rexolite, etc.).
The performances are slightly affected if the probe is used with another coupling medium.
The design is optimized for both high sensitivity and damping in the range of 2.5 cycles(20dB) on average. This technology has been proposed by IMASONIC for several years.

Dynamic:
The acoustic design is particularly optimized to gain about 6dB sensitivity on averagecompared to versatile design, while keeping the same pulse length. This optimization is valid
for the nominal coupling medium. When using the probe with other coupling media,
performances degrade faster than the versatile technology.

Accuracy:
The acoustic design is particularly optimized to gain 0.5 to 1 cycle in pulse length on
average compared to versatile design, while keeping the same sensitivity. This optimization
is valid for the nominal coupling medium. When using the probe with other coupling media,
performances degrade faster than the versatile technology.

Wear resistant:
The acoustic design is optimized to keep equivalent performance level than versatile design
while implementing a front face 10 times more resistant to abrasion.

Versatile

Accuracy

Dynamic

Wear resistant

Acoustic matching to the coupling
medium (water, plexiglas, rexolite,
etc.

Yes

Yes

Yes

No

Pulse length (cycles at -20dB)

2.5

1.5

2.5

No

Sensitivity

Ref.

Ref.

+6dB

Ref.

Performance alteration when usingwith other coupling medium

-.

+

+

-

PHASED-ARRAY

The above mentioned values are indicative and may change depending on probes characteristics, particularly frequency, element size, acoustic matching, cable length, excitation signal.

24

Linear Array Transducers
for steering
Applications
All applications require variable angles
and inspection depths:- General NDT, welds- Pressurized components, rotors, shaftsStandard Configurations

Freq.
(MHz)

Nb elts

Pitch
P (mm)

Active length
L (mm)

Active widthh (mm)

Housing size*(indicative value)

10

32

0.3

9.6

8

17x14x35

10

64

0.25

16

10

24x16x35

10

128

0.25

32

10

40x18x40

5

16

0.6

9.6

8

17x14x35

5

32

0.5

16

12

24x18x40

5

64

0.5

32

15

40x20x40

5

128

0.5

64

15

75x22x45

2.25

32

1

32

20

40x26x35

2.25

64

1

64

20

75x26x35

2.25

128

1

128

20

140x28x40* dimensions valid for probes with removable wedges, without flanges

Standard probes come with 3m cable, top or side output.
Standard connectors are Hypertronix/FRB, ITT Canon, Tyco, Conec, Ipex
Typical interface for attaching wedges is lateral flanges with holes or M3 captive screws(the position of the lugs is adjustable and the distance can be optimized to fit with all yourexisting wedges).

25

Principle
Generally, linear arrays for steering combine electronic beam steering and focusing.
To avoid grating lobes (see technical information page 48), they require a relatively smallinter-element pitch. The number of elements is typically less than 128, and even 64,
as electronic scanning is not often used.

Advantages
These transducers can work with angles and electronically-adaptable focusing depths, i.e.
without changing or moving the transducer. This allows, in particular:- a smaller number of probes to be used,- faster inspection.
They also allow a refracted, non-zero incidence beam to be generated without
using a wedge, which opens new possibilities for when there is no room to use
a wedge.

General Characteristics• Frequency from 500 kHz to 15 MHz• Unlimited number of elements, typically 8 to 128• Optimized signal/noise ratio and pulse width thanks to acoustic
solutions, see page 22• Reproducibility of the inspection through the homogeneity of performance
between the elements of the same probe, and between different probesof the same type• High reliability over time thanks to a robust, watertight design,compatible with difficult industrial environments

Options

Accessories• Wedges – page 42• Cable extensions and adaptors – page 44• NEW - Compatibility with conformable wedges, see page 38

PHASED-ARRAY• Hard face for use in direct contact• Integrated wedge• Housing customized for the mechanical environment(inspected parts, scanner, wedges, etc)
• Customized connection – page 46• Adaptation to a particular environment (temperature, pressure, radiation,
chemical compatibility)• Halogen-free for nuclear environments• Water inlets• Compliance with NF EN ISO 18563-3 standard

26

Linear Array Transducers
for scanning or for long range
inspection
Applications
Automated high-performance inspection of submerged parts: metal plates,
bars, pipes, composite materials, forged parts, etc.

Principle & Advantages
The scanned length (L) is maximised by combining a large numberof elements (typically between 64 to 256) to the widest possible
inter-element pitch (p).
Electronic focusing can be combined with scanning,for example, to inspect at different depths. In general,
electronic deflection is little used for this type of
application.
• Inspection time is reduced because of the highspeed of the electronic scanning combinedwith a large scanning width• The scanning mechanism is simplified

Standard Configurations
Freq.
(MHz)

Nb elts

Pitch
p (mm)

Active size
L x h (mm)Housing size
L x W x H (mm)*

10

64

0.5

32 x 1040 x 16 x 35

10

128

0.5

64 x 1075 x 20 x 40

5

64

1

64 x 1575 x 20 x 40

5

128

1

128 x 15140 x 25 x 45

2.25

128

1.5

192 x 20205 x 30 x 45

2.25

64

2

128 x 20140 x 30 x 35
* indicative values

Accessories – See page 42 to 45• NEW - Compatibility with conformable wedges, see page 38

27

General Characteristics• Frequency from 300 kHz to 20 MHz• Unlimited number of elements, typically from 64 to 512• Optimized signal/noise ratio and pulse width thanks to new acoustic solutions,see page 22• Reproducibility of the inspection because of the homogeneity of the elements of the sameprobe and the different probes of the same type• High reliability over time thanks to a design that is watertight and stainless,compatible with permanent immersion under a metre of water

Options• Pre-focused active area (see below)• Housing adapted to the probe holder• Low profile and side cable for wheel probe• Halogen-free for nuclear environments• Customized cabling• Adaptation to a particular environment (temperature, pressure, radiation,
chemical compatibility)• Compliance with NF EN ISO 18563-3 standard

Technical Information
Mechanical Pre-focusing

flat array

pre-focused array with various radiuses of curvature

PHASED-ARRAY

On linear arrays, electronic focusing is possible only in the planeof incidence. However, in the perpendicular plane (passive aperture), it ispossible to adjust focal depth and lateral resolution by using mechanicalpre-focusing, by choosing the appropriate radius of curvature, active width (h)and water path.

28

Small Footprint Linear Arrays
Applications
These transducers are designed for applications
with reduced transducer access, or with surfaces
with complex geometry where good coupling
is not possible:- Inspection of turbines, blade roots
and fine welds.
small footprint arrays for removable wedges
and with integrated wedges

General Characteristics• Footprint < 8 x 8 mm2• Center frequency 5 to 15 MHz• Number of elements: 8 to 20• Other characteristics similar to standard linear probes

Options• Hard face for use in direct contact• Integrated wedge• Other options similar to standard linear probes

Standard Configurations
Freq.
(MHz)

Nb elts

Pitch
P (mm)

Active length
L (mm)

Active widthh (mm)

Footprint*
(mm)

10

10

0.31

3

3

5x6

10

16

0.25

4

4

6.5x6

10

16

0.31

5

5

7x7

10

20

0.31

6

6

8x8

5

8

0.5

4

4

6.5x6

5

8

0.6

5

5

7x7

5

12

0.5

6

6

8x8

* without flanges or wedge attachment interface

29

Low Profile Linear Arrays

5MHz 12ch arraywith integral wedge

5MHz 64ch array
10mm height

Applications

10MHz 26ch
3.5mm flat array

5MHz 32ch curved array
2.5mm thick

These transducers are designed
for inspecting components
with a very limited vertical clearance:- Boiler tubes- Feeder tubes- Blade roots of turbines (see picture below)

General Characteristics• Housing height < 10 mm• Center frequency: 5 to 15 MHz• Number of elements: up to 64• Other characteristics similar to standard linear probes

Options• Hard face for use in direct contact• Integrated wedge• Other options similar to standard linear probes

PHASED-ARRAY

5MHz 64ch array
5mm height

30

Matrix Arrays

Miniature 5MHz 8x8elts
0.6x0.8mm pitch matrix array

2MHz 11x11elts
1.4x1.4mm pitch matrix array
Miniature 5MHz 16x16elts
0.6x0.6mm pitch matrix array

Applications- Weld inspection- Inspection of parts with complex geometry- General NDT

Principle & Advantages
Matrix array transducers allow 3D beam focusing and scanning,
thus opening up new possibilities:- Control of the focal zone diameter in 3D, cylindrical beam
- Inspection of volumes from limited points of access- Detection of defects that may have multiple, un-predetermined orientations

10MHz 16x16elts 0.3x0.3mm pitch
and 5MHz 16x16elts
0.6x0.6mm pitch active areas

Typical configurations for steering
The matrix array transducer configurations in table below are designed
for use when steering capabilities are required.
The pitch is minimized to offer good elementary directivity and steering capability.
Consequently, for a given number of elements, the active area is reduced
and the beam diameter is larger.
Freq.
(MHz)

Elementary active
size (mm)Total active
size (mm)Number ofelements

2

1,2 x 1,2

10 x 108 x 8 = 64

50,6 x 0,6

5x5

or 11 x 11 = 121

100,3 x 0,3

2,5 x 2,5

or 16 x 16 = 256

Typical configurations for depth / resolution
The matrix array transducer configurations in table below are designed for use when depth
and resolution capabilities are required.
The pitch is larger compared to steering configurations. The steering capability is reduced,
but for a given number of elements, the active area is larger and the beam diameter(lateral resolution) is thinner.

31

2D arrays
Freq.
(MHz)

Elementary active
size (mm)Total active
size (mm)Number ofelements2

2x2

22 x 228 x 8 = 64

51x1

11 x 11or 11 x 11 = 121

100,6 x 0,6

10 x 10or 16 x 16 = 256

Annular sectorial arrays
Freq.
(MHz)

Active diameter(mm)

Average
pitch (mm)Number ofelements

5

10

1.2

64

5

16

1.4

128

2.25

23

2

128

General Characteristics• Frequency from 500 kHz to 15 MHz• Unlimited number of elements, typically 16 to 1024
• High S/N ratio and optimized pulse width thanks to acoustic matching
to wedge material (Rexolite, Plexiglas, PEI, etc)
• Reproducibility of the inspection through the homogeneity of performance
between the elements of the same probe and between different probesof the same type• High reliability over time thanks to a robust, watertight design,compatible with difficult industrial environments

Options

Accessories• Wedges – page 42• Cable extensions and adaptors – page 44• NEW - compatibility with conformablewedges - see page 38
Simulation of 3D beam steering capability
with matrix array

PHASED-ARRAY• Hard face for use in direct contact• Integrated wedge• Housing customized for the mechanical environment (inspected parts, scanner, wedges, etc)
• Customized cabling• Adaptation to a particular environment (temperature, pressure, radiation, chemical compatibility)• Halogen-free for nuclear environments• Water inlets

32

Typical configurations for high resolution
annular sectorial arrays
Inspection of thick parts, forged parts, complex interface partsand difficult materials (coarse grain, non homogeneous).
The shaping of the active surface in a 2D array allows 3D beam steeringand 3D correction of the focus, which can compensate, for example,
for the defocusing effect of a complex interface or an anisotropic material.
Furthermore, matrix immersion transducers, like annular arrays, allow electronic
focusing at different depths.
As an option, Fermat surface pre-focusing (See Fermat concept page 15).

Freq.
(MHz)

Nb elts

Active diameter(mm)

Housing size
diameter x height (mm)*

10

128

40

50 x 60

7.5

128

50

60 x 60

5

128

60

70 x 60

2.25

128

80

90 x 60* indicative value

33

Annular Array Transducers
Applications• Thick parts• Forged parts

Principle & Advantages
Using electronic focusing, the focusing distance and the depthof field can be changed, thus enabling thick parts to be inspectedwith excellent lateral resolution over a large depth range,
without changing the transducer.

General Characteristics

Standard Configurations

Freq.
(MHz)

Options

Nb elts

Active diameter(mm)

Housing size diameterx height (mm)*

10

8

18

25 x 40

10

16

25

35 x 40

10

32

35

45 x 4558

35

45 x 405

16

50

60 x 405

32

70

80 x 502.25
1680
90 x 50• Spherical or bifocal
mechanical pre-focusing
2.25
32
110
120 x 50
• Housing adapted* indicative value
to the probe holder• Halogen-free for nuclear environments• Customized cabling• Adaptation to a particular environment (temperature, pressure, radiation,
chemical compatibility)

Accessories – See page 42 to 45

PHASED-ARRAY• Frequency from 300 kHz to 20 MHz• High sensitivity and signal-to-noise ratio, thanks to the acoustic matching to water allowing
a very good transfer of acoustic energy• Good axial resolution, and reduction of the unseen area below the surface thanks toa short pulse width (See note page 9)• High reliability over time thanks to a design that is watertight and stainless, compatible
with permanent immersion under a metre of water

34

TRL Arrays (Separate Transmit Receive)

Typical Applications• Wrought / cast stainless steel components,
austenitic structures• Dissimilar metal welds• Clad components• Safe end / sub clad of nuclear vessel• Pressurised welds

Principle
Transducers with separate emission
and reception, one linear or matrix arrayon each side.
Linear transducers allow a variablerefraction angle.
Matrix transducers also allow the beam crossing depth to be varied or the beam
to be deflected laterally.

Variable focusing depth

Variable skew angle

Standard configuration
Please contact us for the standard configurations corresponding
to your application.

35

Advantages• Possibility of steering and skewing (matrix only) the beam
• Absence of dead zone
• Focusing effect in the beam crossing region• Improvement of defect response• Reduction of the backscatter signal• Improvement of signal to noise ratio

General Characteristics• Frequency from 500 kHz to 5 MHz• Unlimited number of elements, typically 2x16 to 2x64
• High S/N ratio and optimized pulse width thanks to acoustic matching
to wedge material (Rexolite, Plexiglas, PEI, etc)
• High acoustic insulation between transmit and receive sides• High reliability over time thanks to a robust, watertight design,compatible with difficult industrial environments

Options• Integrated wedge• Housing customized for the mechanical environment (inspected parts, scanner, wedges, etc)
• Customized connection• Adaptation to a particular environment (temperature, pressure, radiation,
chemical compatibility)• Halogen-free for nuclear environments• Water inlets

Accessories• TRL Wedges – page 42• Cable extensions and adaptors – page 44

TRL Probe Design

With the customer’s agreement, IMASONIC can collaborate with partner companies
with experience in inspection methods based on TRL probes, to offer already-qualified
solutions for various inspections.

PHASED-ARRAYIMASONIC can help you to design your TRL probe,and particularly the incidence angle, roof angle
and distance between transmit and receive transducers
to reach the targeted focal zone with the desired
refracted angle.
We can also simulate in detail the beam crossing area
to evaluate the detection and sizing capabilities of the probes.

36

Conformable Array Transducers
Applications
Contact inspection of parts with irregular geometry• Welds, bends, pipe repairs in nuclear power stations• Turbine blades, composite materials• nozzles

Principle
1D or 2D phased array transducers are flexible, and can thus ensure good couplingon the geometry of the inspected part.
The sensor integrates real-time measurement of each element’s position, and thus of the surface,
so when it is used with compatible electronics, the delay laws can be adapted in real time
to steer the beam by compensating for the variations of the interface.
Example of real time
adaptation of delay
laws of a 1D conformable transducer
when passing overa welding seam(courtesy CEA-List
France)Advantages• Feasibility of certain inspections• Improvement in focusing quality by being freed from the interface geometry• Increase in lateral resolution through the use of larger active dimensions

Patented Concept
The concept implemented in these transducers, of updating the delay laws in real time
according to the real position of individual elements, is covered by a patent registeredwith the CEA (Atomic Energy Commission, France).
IMASONIC holds the exclusive licence for the use of this patent in designingand manufacturing these transducers.

37

Smart Conformable Linear Arrays (1D)
The individual elements are mecanically articulated, allowing convex
and concave active profile in the scanning direction.

Existing configurations
Freq.
(MHz)

Number of elements

Pitch
(mm)

Total aperture
(mm)

1.5

24

1.7 x 2241 x 221.5

48

1.5 x 2072 x 202

24

1.4 x 1734 x 172

32

1.4 x 1745 x 174

24

0.9 x 922 x 9Options
Inclinometer allowing to calculate the delay laws in real time taking into account the probe
inclination.

Smart Conformable Matrix Arrays(2D)
The active elements are embedded in a flexible
membrane which allows concave or convex
deformation in two dimensions, to adapt complex
and variable profiles.

Existing configurations
Numberof elements

Elementary
Pitch (mm)Elementary size Total active Radius of curvature Steering range Thickness(mm)
aperture (mm)
(mm)
(°)
(mm)

Tot. 1st Axis 2nd Axis 1st Axis 2nd Axis 1st Axis 2nd Axis
2

84

LW

SW

12

7

2.8

4

1.8

2.5

34 x 28

Spherical R 50

0-30

20-100

2

64

8

8

3.5

4

2.5

2.5

32 x 28

Spherical R 50

0-30

20-100

2.7

60

12

5

1.5

3

1.0

2.0

18 x 15

Spherical R 45

0-50 35-55

8-30

3.3

48

12

4

1.2

3.1

0.6

2.0

12.5 x 25

Spherical R 25

0

20-60

8-15

PHASED-ARRAY

Freq.
(MHz)

38

NEW: Transducers
with conformable wedge
Principle
The conformability is obtained with a flexible membrane filled with water between
the transducer and the inspected component. The coupling between the membrane
and the component requires a small quantity of water or couplant.

Advantages
The conformable wedge combines (see coupling methods page 10)• The acoustic performance of immersion technique with good coupling
and low attenuation• The flexibility and ease of use of contact technique• The compliance with non-regular and/or variable surface geometry

Main features• Compatible with most types of arrays (linear, matrix, focused, curved, etc.)• Acoustic performance close to water thanks to acoustically invisible membrane• Wear resistant membrane *• Halogen free
• Bubble trap system• Easy implementation and easy membrane replacement• Good chemical stability* No damage observed after a run of 0.5Km at 10cm/s over a corroded steel part with Raof 20μm, with lubrication and load of 1Kg

Options• Probes with integral frame (miniaturization, easier implementation)• Angled and L0° membranes• Extra flexible (grey) or extra resistant (blue) membranes• Water inlets for coupling between wedge and inspected part
• Lateral guides for manual use• Mechanical interface for automated use with scanner• Possible use in TRL/SE mode39Standard evaluation kit with 5MHz 64elts
pitch 0.8mm phased array probe• Standard probe mounted on a removable frame• Water path 20mm
• Can be used manually with the handle or mounted
on a scanner without the handle thanks to the 4 lateral
taped holes on each side
• Trim setting with 3 adjustable feet

Standard kit(same acoustic design)with reduced size

Exemple of probes for use
in TRL mode

Exemple of probes with integral conformable wedge

PHASED-ARRAY• Clip system for fast membrane change• Advanced bubble trap system• Reduced size
• 3 types of membranes (standard, extra-flexible,
extra resistant)

40

Curved Linear Array Transducers
Applications
These transducers are an adaptation of flat linear arraysfor the inspection of parts with circular symmetry. The
linear scanning becomes circular to adapt to inspectionof tubes, bars or sections.

Principle
360° or sector electronic beam scanning is combinedwith electronic focusing and beam steering.
• Scanning speed can be adapted to the water path.
• Focusing depth and inspection angle can beelectronically selected depending on the tube/bar
configuration.

General Characteristics• Frequency from 1 MHz to 20 MHz• Number of elements unlimited, typically 64 to 512• High sensitivity and signal-to-noise ratio, thanks to the acoustic matching
to water that allows a very good transfer of acoustic energy.
• Good axial resolution and reduction of the unseen area below the surface
thanks to a short pulse width (See note page 9)• Reproducibility of the inspection through the homogeneity of performance
between the elements of the same probe, and between different probesof the same type• High reliability over time thanks to a watertight and corrosion-resistantdesign, compatible with permanent immersion in a metre of waterin difficult industrial environments

Standard Configuration
Actually there is no standard configuration. The frequency, the number of elements,
the spacing and the radius of curvature are defined according to the tubes,
bars or sections to be inspected, the defects to be detected and the desired
inspection speed in particular.

Options• Pre-focused active area (See page 27)• Housing adapted to the probe holder• Customized cabling• Adaptation to a particular environment (temperature, pressure, radiation,
chemical compatibility)

41

Daisy Array Transducers
Application
Internal tube and bore inspection (fig. 1)
External tube inspection (fig. 2)

Figure 1

Figure 2

Principle
The ultrasonic beam is emitted by a flat circulartransducer and is reflected on the part to beinspected using a mirror.
Electronic scanning allows the beam to be turned
through 360°, without rotating the probe
or the mirror.
The choice of theangle of the mirror
enables the beam
to be given a straightor oblique incidence.

General Characteristics

Daisy element pattern• Frequency from 5 to 15 MHz• Number of elements: 32 to 256(according to the tube diameter)• Minimum internal tube diameter (for internal probes): 15 mm• High sensitivity and signal-to-noise ratio, thanks to the acoustic
matching to water that allows a very good transfer of acoustic energy• Good axial resolution, and reduction of the unseen area below
the surface thanks to a short pulse width (See note page 9)• Reproducibility of the inspection through the homogeneityof performance between the elements of the same probe,and between different probes of the same type

• Centring device• Water input device• Mechanical interfacing with the pusher-puller• Customized connection• Adaptation to a particular environment(temperature, pressure, radiation, chemical compatibility)

PHASED-ARRAY

Options42

Phased Array Coupling Solutions
Wedges for Contact Transducers
IMASONIC offers a wide variety of wedges for contact probes,
fully adaptable to transducers and their conditions of use.

Main Characteristics

Single classic wedge

Single wedge with roof angle

TRL wedge

Parameter

Typical indicative values, can be changed on request

Incidence angle

35-70°SW in steel / 0-70° LW in steel / 0° (Delay line)

Material

Rexolite or Plexiglas

Transducer attachment

2 to 4 threaded metal inserts

Anti-reverberation system

Yes

Options

Skew angle on request

OptionCustomized contact face geometry to fit
inspected parts or wedge focusing
Typical indicative values, can be changed on request

Interface with probe holder

One hole on each lateral side on the wedge

Irrigation system

Two water inlets connected to a groove on the contact face

Wear pads

4 carbide inserts on the contact face to prevent excessive wear on wedge

High temperature

High temperature material and integrated water cooling system

43

Wedge interface
IMASONIC offers as standard design M3 captive screws.
Thin flanges with or without holes remain available on request to fit all wedge designs.

M3 captive screws

Flange with holes

Conformable wedges
Conformable wedges combine acoustic
performance of immersion and ease of useof contact technique. Moreover, they comply
with non-regular and variable surface geometry.
See page 38.
example of conformable wedge

These two materials are the most commonly used for ultrasonic probe wedges.
Rexolite is a very interesting material with low attenuation and low sound velocityof 2350 m/s. It is thus well adapted for reduced-size wedges, thanks to its smaller angle,
and for high frequency probes (7.5 MHz and more), thanks to low attenuation combinedwith shorter acoustic path.
Plexiglas is more resistant to abrasion in some cases, its higher attenuation helps
to attenuate internal reverberations in the wedge..

PHASED-ARRAY

Technical Information
Plexiglas or Rexolite ?

44Phased Array Connection Solutions
Ipex

Cable Characteristics
The standard IMASONIC cables offered on phased array transducers
have been carefully selected for their mechanical and electrical properties.
- Little loss through attenuation or signal filtering- Good flexibility- Good mechanical resistance to handling- Compatibility with most industrial environments

Hypertronix/FRB

ZPAC

Cable typeMulti-coaxial 50 Ohms cable with overall shielding

Number of channel

Up to 16

Up to 64

Up to 128

Up to 256

Cable diameter

4.1 mm

5.6 mm

7.8 mm

8.7 mmMinimum static radius of curvature

25 mm

32 mm

50 mm

60 mm

Minimum dynamic radius of curvature

50 mm

64 mm

100 mm

120 mmBlack PVC
Black PVC
Black PVC
or halogen free PU

Black PVC

External jacket

Specific cable for high radiation or with low attenuation on request

Tyco TCZ

Cable Protection Options
IMASONIC can offer several different cable protection options adapted
to particular environments on request.

Connector Protection Options
ITT Canon DLM96

An optional protective jacket can be placed on the connector.

Connector Types
Conec 78

IMASONIC phased array transducers are compatible with most systems on the market.
The different standard connectors are available. Among them are the following:
Hypertronix/FRB, Tyco, ITT Canon, Ipex, Conec, ODU (non-exhaustive list).
See on the left.

45

Cable extensions & Adaptors
In addition to phased array transducers, IMASONIC offers extension cables
and adaptors, for connecting several probes to a system, or a probe and a systemwith different connectors.
The cable lengths and the number of channels are specified individually.
The cable protection options are also available for extensions and adaptors(within the limit of technically possible lengths).

Examples of cable extensions and adaptors

PHASED-ARRAYIMASONIC extensions and adaptors have all been tested electrically, to checkthat the cabling is in perfect order and that there are no short circuits.

46

Phased Array Principle
The principle of phased array technology is to activate for each shot all or someof the transducer elements which, with the adapted delay laws, contribute collectively
to the generation of the beam.

Electronic Commutation (Multiplexor)
The beam is electronically translated by alternatively firing a given number of elementsof a linear or circular phased array transducer.
This technique is an alternative to the mechanical translation of a single element probe.
The advantages are:- Faster inspection- No mechanical movement required, or reduction of scanline number- Possibility of combining with electronic focusing and beam steering (See below and next page)

Electronic scanning

Delay Laws

Electronic focusing
Electronic Focusing
The beam is electronically focused by applying symmetrical delay laws to the different
elements of a linear or annular phased array transducer.
This technique is an alternative to using several transducers to focus at different depths.
The advantages are:- Only one probe for focusing at each depth- Dynamic focusing speeds up the inspection of thick pieces- Electronic focusing can compensate for focusing aberrations due to refraction at interfaces

47

Electronic Steering
The beam is electronically deflected by applying delay laws to different
elements of a linear, circular or matrix array. Linear and circular arrays allow
for 2D beam steering, while matrix arrays allow for 3D beam steering.

Electronic beam steering
This technique is an alternative to using several transducers at different angles.
The advantages are:- Only one transducer is required for inspection at variable angles- Faster inspection of parts with complex geometry- This technique can be combined with electronic focusing

Full Matrix Capture and Total Focusing Method
FMC (Full Matrix capture) is a specific data acquisition process; each elementof an array is successively used as the transmitter, while all other elements
are used as receivers.
The efficiency of this acquisition is linked to the directivity diagram of each element:
the smaller the element, and the wider the directivity.
When the entire element has been fired, the data acquisition is complete
and TFM can be used for data processing.

PHASED-ARRAYTFM (Total Focusing method) is a method where the arrayis focused in emission and reception at every pointof the image. This gives very good resolution
and high image quality, but does not provide
any information on the nature of the defect.

48

Design Notes for Linear Phased Array
Grating Lobes
When using a phased array transducer, delay laws are applied to each channel to generatea beam with a given refraction angle and focal distance.
The ultrasonic beam is generated by the constructive interference of each transducer element’s
contribution in the desired direction.
In some cases, this interference can also be constructive in other directions.
These lobes of energy emitted outside the electronically driven direction are called grating lobes.
These energy lobes can interact with the part to be inspected in the same way as the main
beam, and thus generate echoes causing interference to the inspection. Therefore they haveto be avoided as much as possible.
The angle of the position of grating lobes in relation to the main beam is givenby the following formula:

Note: this formula is only valid in the case of electronic deflection (linear delay law).
In the case of electronic focusing, the angular deviation between the main beam andthe grating lobes is reduced.

Example for 70° SW in steel
From the above formula, the following general rule can be obtained:• If p < /2, then no grating lobe is generated whatever the angle of the main beam
• If p > , then there is always at least one grating lobe generated whatever the angleof the main beam
• Between these two values, the grating lobes appear progressively according to the angleof the main beam. The maximum pitch to avoid grating lobe is given by the formula:

49

In practice, for typical use in the 30-70° SW or LW range with a wedge for a 45° angle,
a pitch of 1.0  gives good results.

Lateral Resolution along the Plane of Incidence
The following formula allows a good approximation to be made of the lateral resolution,
and a quick check of the link between the active aperture and the lateral resolution.

W = focal spot or beam width (at –6dB in emission reception)
 = wave length in the medium under consideration
 = angle beneath which the active area is seen from the focal point
Note: This formula is a rough estimate valid when the hypothesis of electronic focusing
at the focal point under consideration is made. It does not take into account the energy
refraction/reflection law depending on the angle.

Number of Elements
Knowing the inter-element spacing required to avoid grating lobes and the widthof the active aperture, the number of elements necessary can be rapidly deduced.
If the appropriate number of electronic channels is not available for technicalor economic reasons, the best possible compromise must be found, by readjusting
the inter-element spacing, the frequency, and/or the active aperture(and thus the lateral resolution).

PHASED-ARRAY

Note: Some linear array transducers are also used for electronic scanning. In this case,the beam is generated by only some of the elements. To calculate the lateral resolution,
only the size of the active area is taken into account.

50

AND MORE ...
These two pages illustrate other IMASONIC capabilities through examples of transducers
dedicated to medical applications. These features can be adapted to NDT transducers
for new or challenging applications.

Transducers for medical diagnosis
High frequency transducers for high resolution imaging(eye and skin imaging, frequency up to 20 MHz)very high sensitivity - direct focusing

Photoacoustic imaging
The technology developed by IMASONIC has important advantages for applications such as
photoacoustic imaging, where the level of sensitivity in reception combined with a wide
bandwidth is very important

Dual frequency transducers
These transducers are designed with two frequency
peaks, as illustrated on the spectrum on the right,
with 1MHz and 2MHz peaks.
This kind of feature can be used for application
based on harmonic imaging or non linear acoustics.
It can also comply with requirements of highattenuation materials that generate important filtering
effects toward the low frequencies.

51

High power transducers for therapeutic applications
IMASONIC is the world leader for high power transducers dedicatedto medical therapy through HIFU technology (High Intensity Focused Ultrasound).

High power focusedtransducer for prostatecancer treatement

HIFU is a state of the art acoustic ablation technique, using the powerof ultrasound to accurately destroy deep-seated tissues without surgery,and without harming surrounding tissues.
IMASONIC high power technology combines high power capability, direct
shaping of the active element, and compatibility with array patterns(see table below).

300 mm diameter half
sphere transducer.
Matrix array with morethan 1000 elts.

Miniature endoscopic
probe combining imaging
and high power capability
on a single transducer

Acoustic power surface

Up to 30W/cm2

Efficiency

50 to 70%

Frequency range

200 kHz to 10 MHz

Shaping capability

F number down to 0.5 (half sphere)

Size range

Up to 300mm

diameter Array capability

Yes

Bandwidth

30 to 70%

MRI compatibility

yes, on request

High power ultrasound can also be used for Vibroacoustography, a novel
imaging for nondestructive inspection of materials. This is an ultrasound-based
imaging technique that uses the dynamic (oscillatory) radiation forceof low-frequency excitation (within kilohertz range) to remotely vibrate objects
and detect the ensuing acoustic emission.
The generation of high power ultrasonic beams can also be used
for application based on non linear-acoustics, like detection of closed cracks
or lack of adhesion in composite stuctures.

AND MORE ...

64 channel circular arrayfor oesophagial cancer
treatement – MRI
compatible – Including
cooling system.

IMASONIC SAS • 4 Rue des Savourots • 70190 Voray-sur-l’Ognon • FRANCE
Phone : +33 (0)3 81 40 31 30 • Fax : +33 (0)3 81 40 31 39
Email : imasonic@imasonic.com • Web : www.imasonic.com