Note: Descriptions are shown in the official language in which they were submitted.
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DEVICE AND METHOD FOR THE NON-DESTRUCTIVE CONTROL OF METAL
PROFILES
The invention relates to the field of non-destructive testing of metallurgical
products, in
particular with long profiles, typically in the range from a few metres to
several tens of metres.
In order to understand the invention better, it will be described in the
context of generally
tubular products, in particular tubes, as examples of metallurgical products.
However, the
invention is intended to be of wider application.
Great length tubes are widely used. Examples of fields of application which
may be cited
are electricity production where boiler tubes are used, oil and gas
production, where tubes are used
for drilling, extraction and transport (line pipes), or indeed mechanical
construction, which could be
in civil engineering, or indeed in the automobile and aviation sectors.
As with the majority of metallurgical products, the tubes are susceptible of
possessing
defects linked to their manufacture, such as inclusions of material in steel,
or the absence of
material, for example. In general, any heterogeneity in the steel matrix is
viewed as a defect which
is susceptible of impairing the mechanical strength of the tube in service.
For this reason, metal tubes are inspected immediately after their
manufacture, not only to
detect any defects therein, but also, if appropriate, to determine information
for use in assessing the
hazard profile of these defects, in particular the size, depth, position,
nature or indeed the
orientation.
When manufacturing a batch of tubes, it is desirable to inspect as many as
possible as
reliably as possible. Certain protagonists in the field, such as the
Applicant, inspect each tube
produced individually.
Testing of a tube represents a manufacturing step with the same status as more
conventional
shaping steps.
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Because they have an influence on the production rate, test methods which are
carried out
have to be economical and rapid, and still remain reliable. Practically
automatic test methods are
also being investigated.
In particular, test techniques using ultrasonic waves are used. The ultrasonic
waves are
emitted and the resulting echoes are studied, looking for those which cannot
be attributed to the
geometry of the tube. Inclusions or absences of material constitute variations
in the wave
propagation medium, and for this reason generate echoes when they are struck
by the ultrasonic
waves.
The intensity of the echo produced by a defect depends on the angle at which
the wave
strikes it. For any direction of propagation of the ultrasonic wave in the
tube, defects orientated
correspondingly, i.e. perpendicular to the direction of propagation, are
principally detected, but with
a certain tolerance of the order of one or two degrees.
In practice, defects are not purely longitudinal or transverse, but reflect an
echo which is of a
greater or lesser extent in one or the other of these directions. As an
example, a defect is qualified
as longitudinal when it generates an echo with an intensity above a defined
threshold in response to
a burst with a corresponding orientation. This threshold is fixed by
calibration using notches with a
normalized position (depth and orientation) and dimensions. The orientation of
a defect may be
equated to its largest reflective surface.
The duration of the test principally depends on the time necessary for the
ultrasonic waves
to pass through the tube, there and back, and to a certain extent on that for
processing the captured
returned signals.
In order to comply with demands linked to production rates and safety, it has
become
standard practice to limit the number of ultrasonic bursts and only to look
for defects orientated in
certain inclinations.
Conventionally, the aim is to detect defects with the broadest inclination,
generally defects
orientated parallel to the tube generatrix.
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Recent developments in the art are targeted towards test methods which can
also detect
defects with different orientations while limiting the number of bursts in
order to keep the test rate
acceptable.
US 5 473 943 discloses an ultrasonic wave test device comprising nine
ultrasonic sensors or
transducers distributed around a tube to be tested. A device of this type can
be used to detect
defects orientated in nine different directions with respect to each other.
The number of directions
which can be tested remains limited by the number of sensors. Further, that
device can only be used
to inspect a narrow zone of the tube, which means that the tube has to be
advanced very slowly with
respect to the sensors, or that the number of sensors has to be multiplied. A
low rate of advance is
incompatible with production demands, while increasing the number of sensors
poses problems
with costs and adjustment.
Some recent developments use ultrasonic sensors known as "phased array"
sensors, also
known as "multi-element linear transducers". These sensors comprise a
plurality of electroacoustic
transducers in the form of piezeoelectric elements distributed over an active
face of the sensor in a
principal direction. As an example, these transducers may be disposed in a
manner which is aligned
with respect to each other and form what is sometimes known as a "transducer
bar". Sensors with a
distribution of this type are said to be "one-dimensional". The transducers
are sequentially excited
one after the other in a manner so as to combine the ultrasonic waves produced
to form a deflected
beam of waves, which may be focused (focal point in front of the sensor),
which means that a tube
can be inspected as to the existence of defects orientated in a corresponding
direction.
An ultrasonic wave test device comprising a one-dimensional phased array type
sensor is
also known, in which the elementary transducers are distributed around the
tube to be tested. A
device of this type can be used to detect defects with almost all
inclinations, but only in a reduced
section of the tube. Because only a zone with a very small longitudinal extent
can be inspected at
one time, it must be operated at a low tube advance speed. The result is that
the duration of the
4
inspection is too long for industrial application to be envisageable.
Furthermore, the device in
question necessitates a different sensor per diameter of the tube to be
inspected.
WO 2003/050527 discloses non-destructive test equipment for metallurgical
products in
which a one-dimensional phased array type sensor is used. Each transducer
element is excited once,
then a processing circuit analyses the overall response of the tube to this
single emission, which is
known in the art as a burst. Starting from a burst in the transverse direction
of the tube, it is capable
of determining the presence not only of defects disposed perpendicular to this
direction, but also
defects with an inclination with respect to this perpendicular direction which
is within plus and
minus 10 .
In practice, three sensors are used: two sensors dedicated to the detection of
defects which
are orientated longitudinally or have an inclination with respect to this
longitudinal direction in the
range plus 20 to minus 20 , and a supplemental sensor for detecting defects
orientated transversely
to the tube and/or for measuring the thickness of that tube.
The equipment in question is broadly satisfactory.
It can be used to test a tube as to the existence of defects orientated in a
limited number of
orientations. In order to test the tube as to the existence of defects with
any orientation, it is
necessary to multiply the number of sensors or to modify the orientation of
the sensors with respect
to the tube a number of times, each time in order to target a different
direction.
The Applicant has sought to improve the existing position.
The proposed device for testing metallurgical products is of the type
comprising an ultrasonic
sensor comprising a plurality of elementary transducers which can be operated
independently of
each other and which are distributed in a two-dimensional pattern, a first
electronic component
which is capable of exciting each of the elementary transducers in accordance
with at least one
temporal law corresponding to a burst of ultrasonic waves in a corresponding
line of sight, and a
second electronic component which is capable of processing at least a portion
of signals captured by
each of the elementary transducers. Each temporal law is arranged such that
the corresponding
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burst of the ultrasonic waves from the plurality of elementary transducers
jointly produces a beam
of ultrasonic waves which is divergent about the corresponding line of sight
with increasing
distance from the ultrasonic sensor, the first electronic component is
configured to control the
divergence about the line of sight by the at least one temporal law, and the
at least one temporal law
produces a defocused primary beam jointly from the plurality of elementary
transducers.
The proposed method for testing metallurgical products comprises providing an
ultrasonic
sensor comprising a plurality of elementary transducers which can be operated
independently of
each other and are distributed in accordance with a two-dimensional pattern,
exciting each of the
elementary transducers in order to produce a burst of ultrasonic waves that
jointly correspond to a
beam which is divergent about a corresponding line of sight with increasing
distance from the
ultrasonic sensor, controlling with a first electronic component, the
divergence of the beam about
the corresponding line of sight by at least one temporal law corresponding to
the burst of ultrasonic
waves in the line of sight, and the at least one temporal law produces a
defocused primary beam
jointly from the plurality of elementary transducers, and processing at least
a portion of signals
captured by each of the elementary transducers in response to the ultrasonic
burst.
In contrast to conventional methods and devices which seek to deflect and to
focus a beam
of ultrasonic waves in the inspection line of sight, the proposed device emits
a beam of ultrasonic
waves which diverges about the line of sight.
For a burst sighting a particular line, a more extensive zone of the tube is
covered by the
ultrasonic waves resulting from this burst
This more extensive "insonification" zone can be used to detect defects which
have a greater
inclination with respect to the line of sight than in conventional devices.
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The proposed device can be used to detect defects at any inclination with the
aid of a single
sensor excited a limited number of times, while retaining a good testing rate.
In particular, with the aid of a single sensor and a limited number of bursts,
it is possible to
detect transverse defects, also termed "circumferential", i.e. defects
extending perpendicularly to the
generatrix of the tube, longitudinal defects which extend along this
generatrix, and defects making
any angle with the generatrix of the tube to be tested.
The gain in productivity and reliability is substantial.
Other characteristics and advantages of the invention will become apparent
from an
examination of the following detailed description and the accompanying
drawings in which:
=
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= Figure 1 diagrammatically shows a non-destructive testing device for a
tube, in front
view;
= Figure 2 represents the device of Figure 1, in side view;
= Figure 3 represents an electroacoustic sensor for use in the device of
Figure 1, in front
view;
= Figure 4 represents the sensor of Figure 3 in sectional view along a line
IV-IV;
= Figure 5 represents a block diagram of control and processing electronic
components for
the electroacoustic sensor of Figure 3;
= Figure 6A represents a diagram illustrating a burst direction for an
ultrasonic beam in
space;
= Figure 613 represents a diagram illustrating an array of elementary
transducers;
= Figures 7A and 7B respectively represent a first and a second delay table
for a multi-
element matrix electroacoustic sensor;
= Figure 8 represents a perspective view of an array of elementary
transducers in the
working position with respect to a tube to be tested, and a bar diagram
showing the
delay values applied to these transducers for a longitudinal burst in
accordance with a
first variation of a first embodiment of the invention;
= Figure 9A represents the table and the diagram of Figure 8 in isolation,
shown in
perspective;
= Figure 10A represents the bar diagram of Figure 9A, in side view;
= Figure 11A represents the bar diagram of Figure 9A in front view;
= Figure 12 is analogous to Figure 8, for a transverse burst;
= Figure 13A is analogous to Figure 8 for an oblique burst;
= Figure 14 shows the table and diagram of Figure 13A in perspective, at a
different
viewing angle;
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= Figures 9B, 10B, 11B and 13B are respectively analogous to Figures 9A,
10A, HA and
13A for a second variation of the first embodiment;
= Figures 15 and 16 are analogous to Figures 7A and 7B for different
excitation
conditions;
= Figures 17, 18A and 18B show "insonification" layouts for a reference
device, a device
in accordance with the first embodiment of the invention, and a device in
accordance
with a second embodiment of the invention respectively;
= Annex A.1 indicates, in the form of tables, delay values corresponding to
the first
variation of the first embodiment of the invention;
= Annex A.2 indicates, in the form of tables, delay values corresponding to
the second
variation of the first embodiment of the invention;
= Annex A.3 indicates, in the form of tables, the transposition laws for
the delay values for
different burst directions;
= Annex A.4 indicates, in the form of tables, delay values corresponding to
a second
embodiment of the invention;
= Annex A.5 is an addressing matrix for the elementary transducers of an
electroacoustic
sensor.
The drawings and the annexes comprise elements of a certain nature. Thus, they
could
not only serve as the description of the invention, but also serve to define
it, as appropriate.
Reference will now be made to Figures 1 and 2.
Ultrasonic wave test equipment comprises a bench 1 supporting a metal tube 3
to be tested
and an ultrasonic sensor 5 applied against the peripheral surface of the tube
3, and connected to
control and processing electronics 6. The ultrasonic sensor 5 is sometimes
known in the art as a
transducer.
For the test, the sensor 5 and the tube 3 are displaced helically relative to
each other.
Here, the tube 3 is displaced with respect to the bench 1 in accordance with a
helical movement
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about an axis corresponding to its longitudinal axis, while the sensor 5 is
held in position with
respect to the bench 1. The bench 1 may be provided with rotary rollers
inclined with respect to
the longitudinal axis of the tube 3.
In a variation, the tube 3 may be moved in rotation alone with respect to the
bench 1,
while the sensor 5 slides in the longitudinal direction of the bench 1. The
sensor may be mounted
on a carriage which is movable with respect to the bench 1. In accordance with
yet another
variation, the sensor 5 may turn about the tube 3 while the latter is
translated with respect to the
bench 1.
The relative helical motion between the sensor 5 and the tube 3 means that the
whole of
the tube 3 can be tested using one sensor 5 with reduced dimensions compared
with the
circumference of the tube 3. Alternatively, a larger number of sensors could
be provided, disposed
in a ring around the tube 3, and a burst sequence could be carried out which
ensured coverage when
the tube 3 slides with respect to the sensor 5.
A coupling medium or coupler, for example in the form of a gel, may be
interposed between
the sensor 5 and the peripheral surface of the tube 3. In a variation, the
apparatus may comprise a
box filled with water or any other liquid coupling medium in which the tube 3
and the sensor 5 are
immersed.
Reference will now be made to Figures 3 and 4.
They show a sensor 7, of the "mosaic" type, which may be used as a sensor 5 in
the
apparatus of Figures 1 and 2. Mosaic sensors are sometimes known as "multi-
element transducers"
in the art.
The sensor 7 comprises a plurality of bars 9 formed from a piezoelectric
material, in this
case distributed in a regular manner as an array. As shown, the sensor 7
corresponds to that
which is generally known in the art as a "multi-element array transducer".
The bars 9 are embedded in a matrix 11 formed from an electrically inert
polymer material.
The bars 9 are electrically and acoustically independent of each other. Each
bar 9 may be
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individually excited in order to generate ultrasonic pulses without these
pulses reaching adjacent
bars 9. Each bar 9 thus forms an elementary transducer which can function
independently of the
other bars 9.
The sensor 7 has an emitting surface which is not constituted by a
homogeneous, bulk
piezoelectric material, and so it is different from conventional sensors. In
contrast, the emitting
surface of the sensor 7 is produced from a composite material comprising a
polymer matrix and a
plurality of elements formed from piezoelectric material.
The sensor 7 here comprises sixty-four bars 9 distributed in a regular manner
in accordance
with a square pattern with eight bars 9 to a side. Each bar 9 here has a
square section the side of
which is smaller than 1 millimetre and larger than 0.1 millimetre. The
separation is of the order of a
tenth of a millimetre on facing sides of adjacent bars 9.
The square pattern is only one example of a two-dimensional pattern. A multi-
element
sensor is said to have a two-dimensional pattern when its elementary
transducers are distributed in
accordance with two directions which are distinct from each other over an
active surface of the
sensor, that which acts for emitting and receiving ultrasonic waves.
More generally, the invention may be carried out with any two-dimensional
pattern.
Each bar 9 is attached to its own electrical cable 13 and which connects it to
control and
processing electronics. The electrical cables 13 are collected together in a
sheath represented by the
block with reference 15 in Figure 4.
The sensor 7 comprises a casing 17 to which the sheath 15 is attached and
which houses the
bars 9. The casing 17 is closed by an adaptation layer 19 in contact with the
active surface of each
of the bars 9. The bars 9 are in contact with a metal plate 21 via a face
opposite to their face in
contact with the adaptation layer 19 in order to earth it. The space which is
still free in the casing 17
is filled with a packing 23.
Figure 5 shows an example of operating electronics 25 for an ultrasonic sensor
which may
be of the type of sensor 7 described above.
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The operating electronics 25 comprise an excitation circuit 27 individually
connected to
each of the elementary transducers 29 of the sensor in question. In this case,
the elementary
transducers 29 are distributed in accordance with a pattern corresponding to
an array with a square
shape with eight transducers per side. In Figure 5, an elementary transducer
Ci,j is marked by its
5 position in the table (line i, column j).
For the purposes of simplification of the drawing, the excitation circuit 27
of Figure 5 is in
each case connected to a single elementary transducer Ci,j of each column
only. In practice, the
excitation circuit 27 is connected to each elementary transducer Ci,j
individually.
The operating electronics 25 also comprise an acquisition circuit 31 which is
capable of
10 .. recording and processing signals obtained from waves captured by the
elementary transducers 29.
Each elementary transducer Ci,j is individually connected to a respective
analogue-to-digital
converter 33 which samples the output signal Si,j(t) of the transducer Ci,j in
question and supplies a
memory 35 with the digital representation Si,j,k obtained, at least over a
predefined time period.
The content of the memory 35 may be processed using a processing unit 37, for
example a
microprocessor.
For the purposes of simplification of the drawing, an analogue-to-digital
converter 33 of
Figure 5 is connected in each case to a single piezoelectric element Ci,j of
each line only. In
practice, each analogue-to-digital converter 33 is individually connected to
all of the elementary
transducers Ci,j of its line.
The elementary transducers 29 are excited individually and sequentially. A
"burst" is the
term used for the process which consists of causing each elementary transducer
Ci,j to emit a series
of pulses. A burst corresponds to implementing a temporal excitation law which
determines, for
each elementary transducer Ci,j, a respectively delay ti,j with respect to a
temporal reference which
is common to the set of elementary transducers Ci,j,. Once excited, the
elementary transducers
jointly produce a beam of ultrasonic waves.
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An excitation law is computed so as to sight a particular direction, which
means that the
elementary transducers 29 together produce a beam of ultrasonic waves which
propagate in this
particular direction or burst direction.
In accordance with a first embodiment of the invention, the direction of the
burst is inclined
with respect to the normal to the principal plane of the active surface of the
sensor when this is flat,
or to the central zone of this surface when it is curved. The beam of
ultrasonic waves may be
viewed as a deflected beam. This beam diverges about the line of sight.
In accordance with a second embodiment of the invention, the burst direction
substantially
corresponds to the normal to the principal plane of the active surface of the
sensor when this is flat,
or to the central zone of this surface when it is curved. The beam of
ultrasonic waves is divergent.
In particular, this beam is defocussed.
Reference will now be made to Figure 6A.
This shows a multi-element sensor C which is generally flat, square in shape,
with a
geometric centre with reference S.
The direction of propagation D of a beam of ultrasonic waves, also termed the
primary
direction here, may be defined by means of the following parameters:
= a first angle a, or "deflection angle", which this direction of
propagation makes with the
normal N to the principal plane of the sensor C (when the multi-element sensor
is not
flat, then the normal to the central zone of this sensor is what is
considered);
= a second angle 0, termed the "angle of obliquity" or abbreviated to
"obliquity", which
the direction of propagation D makes with a reference direction R, this latter
being
linked to the sensor C and to its geometry, in a plane P perpendicular to the
normal N to
the sensor C.
The sensor C is preferably positioned with respect to a tube to be inspected
in a manner
such that the principal plane of the sensor C is directed in a direction
tangential to the tube or, in
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other words, that the normal N to the principal plane of this sensor C at the
geometric centre S
coincides with a radius of the tube in question.
A burst in a direction of propagation D can be used to detect defects
orientated in a
corresponding manner in the tube, i.e. perpendicular to the direction
corresponding to the obliquity
of the direction of propagation D, or making a certain angle with this
perpendicular direction.
In accordance with the invention, the beam of ultrasonic waves used for
inspection diverges
about its direction of propagation D.
Reference will now be made to Figure 6B.
It highlights an array 41 of elementary transducers distributed in accordance
with a square
pattern. Without limiting the invention, the array 41 here comprises 8 x 8
elementary transducers.
The pattern has a first axis of symmetry x and a second axis of symmetry y,
respectively
corresponding to the midpoint perpendiculars of the sides of the pattern.
Preferably, the ultrasonic sensor is positioned with respect to the tube to be
tested such that
the first axis of symmetry x or the second axis of symmetry y of the pattern
corresponds to the
longitudinal direction of the tube. By convention, it will be assumed that in
Figure 6B, the sensor is
disposed such that the first axis of symmetry x corresponds to the transverse
direction of the tube to
be tested. The first axis of symmetry x acts as a reference direction for the
measurement of the
angle of obliquity 0. In this relative position of the ultrasonic sensor and
the tube, the second axis of
symmetry y of the array 41 corresponds to the longitudinal direction of the
tube.
In accordance with the first embodiment of the invention, at least one burst
is carried out in
a particular direction of obliquity, which corresponds to the orientation of
the investigated defects.
In an advantageous development of the first embodiment of the invention, an
ultrasonic
burst is envisaged in each of several burst directions which differ from each
other by the value of
their respective obliquity Oi (i=1, 2, ... n) measured with respect to the
direction of the first axis of
symmetry x of the sensor 41. The obliquities Oi are determined in a manner
such that an angular
sector of 2 it radians (360 ) is covered in a regular manner. Thus, the tube
can be tested as to the
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existence of defects irrespective of the orientation of these defects in the
tube. In a still more
advantageous development, eight successive ultrasonic bursts are carried out
which differ from each
other in the value of their respective obliquity 0i (i=1, 2.....8).
The following table summarizes the characteristics of the various bursts.
Rank of burst Burst direction Obliquity (with respect to the x
direction)
1 D1 01 = 0
2 D2 02 = 45
3 D3 03 = 90
4 D4 04 = 135
D5 05 = 180
6 D6 06 = 225
7 D7 07 ¨ 270
8 D8 08 = 315
5
In this table, the rank of the burst is only indicative; what is important is
that at the end of
the eight bursts, the whole of the angular sector of 2 it radians has been
covered. The order in
which the bursts are carried out is of little importance. This is primarily
due to the fact that in
accordance with the invention, it is possible to modify the direction of
propagation of an
ultrasonic beam without modifying the orientation of the ultrasonic sensor
with respect to the
tube.
A respective temporal excitation law corresponds to each burst which causes
the resulting
beam of ultrasonic waves to propagate in a particular line of sight Di, i: =
1,... 8 or burst
direction.
In accordance with a first variation of the first embodiment of the invention,
each
temporal excitation law comprises at least two sub-laws each defining the
delay values to be
applied to the transducers of a respective sub-set of the array 41 such that
the elementary
transducers of the corresponding sub-set jointly produce a primary beam of
ultrasonic waves in a
respective direction of propagation, the respective directions of propagation
of the primary beams
diverging with respect to each other and with respect to the burst direction
Di of the resulting beam
on moving away from the ultrasonic sensor.
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In a first form of this first variation, the primary beams are not focused,
i.e. they have no
focusing, neither direct nor inverse (inverse focusing is also sometimes known
as "defocussing").
As an example, the primary beams may have a distant focus compared with the
distance separating
the sensor from the tube to be tested. As an example, each primary beam has a
focal point which is
more than one metre from the sensor, while this latter is at a distance from
the tube which is in the
range 30 to 40 millimetres.
In a second form of this first variation, the primary beams are each
defocussed, i.e. they
have an inverse focusing. The focal point is behind the ultrasonic sensor with
respect to the path of
the ultrasonic waves.
The respective directions of emission of the primary beams form a respective
angle either
side of the direction of propagation.
The sub-laws are arranged such that the corresponding primary beams encounter
a target
surface of the tube to be tested corresponding to the line of sight at two
respective penetration zones
of this surface which are adjacent to each other.
This first variation of the first embodiment corresponds to emitting a beam of
ultrasonic
waves which is deflected and divergent; this beam results from the emission of
multi-directional
beams, in particular bi-directional. The sub-beams are not focused or have a
distant focus.
Each sub-law is determined such that the corresponding sub-set of elementary
transducers
produces a beam termed the primary beam the direction of propagation of which
forms an angle of
inclination J3 with respect to the line of sight Di, i:= 1, ... 8) on one side
or the other of this line.
The direction of propagation of each primary beam is such that it has an
obliquity which is
deduced from the obliquity 0i, i:= 1, ... 8 of the direction of propagation
Di, i:= 1, ... 8 of the
resulting beam by addition or respectively subtraction of the value of the
angle of inclination [3.
Each primary beam is deflected and diverges with respect to the line of sight
Di.
In a non-focused beam, the ultrasonic waves produced by the various elementary
transducers principally propagate parallel to each other. In order to obtain a
non-focused primary
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beam, delay values which follow a linear law are applied to a corresponding
sub-set of elementary
transducers. The beam of ultrasonic waves resulting from the primary beams
diverges about the
burst direction Di, i:= 1... 8 on moving away from the ultrasonic sensor.
In accordance with a second variation of the first embodiment of the
invention, each
5 temporal excitation law defines delay values to be applied to at least a
portion of the transducers of
the array 41 in a manner such that these elementary transducers jointly
produce a primary beam of
ultrasonic waves which extend in an emission direction, or primary direction,
corresponding to the
burst direction Di and diverge about this burst direction on moving away from
the ultrasonic sensor.
This second variation of the first embodiment corresponds to the emission of a
divergent
10 .. beam of ultrasonic waves which is deflected with respect to the normal N
to the principal plane of
the sensor.
A divergent beam has an angle of divergence. The value of this angle may be
determined
experimentally, optionally with the aid of simulations which can be used to
visualize the resulting
beam. In practice, divergence angle values are sought which can be used to
cover the largest
15 possible angular sector while preserving good detection quality. This
limits the number of bursts
necessary to inspect a tube as to the existence of a defect of any
inclination. As an example,
coverage of an angular sector of 40 is desirable. As an example, a value for
the angle of
divergence of 22.5 may be used.
Firstly, it is important to construct a temporal excitation law which can be
used to produce a
burst in a first direction D1, in the case of the first variation.
The elementary transducers of the array 41 located to one side of the first
axis of symmetry
x (left hand side in Figure 6B) form a first sub-set and will jointly generate
a beam of non-focused
ultrasonic waves which are inclined at an angle 13 with respect to the
obliquity of the direction Dl.
The elementary transducers located on the other side of the first axis of
symmetry x (right hand side
in Figure 6B) form a second sub-set and will generate a non-focused beam of
ultrasonic waves
inclined at an angle +13 with respect to this obliquity. The two primary beams
join up in the
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direction DI into a resultant beam, i.e. they superimpose or merge in the
direction DI to ensure the
transmission of energy in the direction D1, such that the resultant beam is
energetically
homogeneous between the directions (DI ¨ fI) and (DI + p) at the surface of
the tube. The result is
a broad focal spot at the surface of the tube, or insonification zone, which
can be used to seek out
defects which have a fairly steep inclination with respect to the direction
corresponding to the
obliquity of the burst direction.
Reference will now be made to Figure 7A.
Table 70 generically shows the delay values to be applied to each elementary
transducer
of the array 41. The value Bi,j of the delay to be applied to the elementary
transducer Ci,j of
array 41 is found in line i, column j of the table 70.
Reference will now be made to Figure 7B.
Table 71 is analogous to table 70. Table 71 generically shows the delay values
to be applied
to produce a burst in the first direction DI.
The delays applied to the transducers of one of the sub-sets are deduced from
those to be
applied to the transducers of the other of the sub-sets by a symmetry the axis
of which corresponds
to the first direction of symmetry x of array 41. The value Bi,j of the delay
to be applied to the
transducer Ci,j is equal to the value Bi,n-j+1 of the delay to be applied to
the transducer Ci,n-j+1,
the integer n corresponding to the number of elementary transducers in a line
of the array 41 (in this
case, n=8). As an example, the value B2,3 of the delay to be applied to the
elementary transducer
C2,3 is equal to the value B2,6 to be applied to the elementary transducer
C2,6.
In other words, the same temporal excitation sub-law is applied to each of the
two sub-sets
of elementary transducers of the array 41.
For a sub-set of elementary transducers, the set of delay values Bi,j such
that i:= I to 8 and
j:= 1 to 4 may be computed by applying the laws for computing the propagation
and interference of
ultrasonic waves which are known to the skilled person in the field. This
computation may in
17
particular be carried out manually, using a spreadsheet or using specific
software, for example of the
type known as civATm distributed by the firm EXTENDE
TM
The table of annex A.3 shows the transposition laws which, starting from the
delay values
obtained for a burst in the first direction DI, can be used to deduce delay
values for the burst in the
fifth direction D5 because of the symmetry of the sensor. The delay values to
be applied to the
elementary transducers Cij for a burst in the fifth direction D5 are deduced
from the values
computed for the burst in DI by the transformation indicated in annex A.3.
The delay values to be applied to the elementary transducers Cij for a burst
in the third
direction D3 are computed in an analogous manner to that which has been
carried out for the first
direction Dl.
The elementary transducers of array 41 located to one side of the second axis
of symmetry y
(at the top in Figure 6B) form a first sub-set and will jointly generate a non-
focused beam of
ultrasonic waves which is inclined at an angle -0 with respect to the
obliquity of the direction D3.
The elementary transducers located on the other side of the second axis of
symmetry y (at the
bottom in Figure 6B) form a second sub-set and will generate a non-focused
beam of ultrasonic
waves which is inclined at an angle +p with respect to this obliquity. The two
primary beams join
up in the direction D3 into a resultant beam in order to ensure the
transmission of energy in the
direction D3, such that the resulting beam is energetically homogeneous
between the directions
(D3-(3) and (D3-1-0) at the surface of the tube. This results in a broad focal
spot on the surface of the
tube, or insonification zone, which can be used to investigate defects which
are fairly steeply
inclined with respect to the direction corresponding to the obliquity of the
burst direction.
Annex A.3 shows that delay values for the seventh direction D7 (in the first
axis of
symmetry x) can be deduced from the delay values in the direction D3 by
symmetry.
Consider a burst in the direction D2.
The elementary transducers of the array 41 located to one side of a diagonal
of the pattern
corresponding to the direction D2 (at the top in Figure 6B) form a first sub-
set and will jointly
CA 2893044 2020-04-08
CA 02893044 2015-05-27
18
generate a beam of non-focused ultrasonic waves inclined at an angle ¨0 with
respect to the
obliquity of the direction D2. The elementary transducers located to the other
side of this diagonal
(at the bottom in Figure 6B) form a second sub-set and will generate a non-
focused beam of
ultrasonic waves inclined at an angle +13 with respect to this obliquity. The
two primary beams join
up in the direction D2 in a manner such that the resulting beam is
energetically homogeneous
between the directions (D2-43) and (D2+13) at the surface of the tube. This
results in a broad focal
spot at the surface of the tube, or insonification zone, which can be used to
investigate defects which
are fairly steeply inclined with respect to the direction corresponding to the
obliquity of the burst
direction.
Annex A.3 shows that it is possible to deduce delay values for the fourth
direction D4 (in
the second axis of symmetry y; as also shown in annex A.1.4) from the delay
values for a burst in
the direction D2 by symmetry; then for the sixth direction D6, starting from
delay values
corresponding to the direction D4, by symmetry about the first axis x. Delay
values for a burst in
the eighth direction D8 are deduced from delay values corresponding to the
direction D2, by
symmetry about the first axis x, or delay values corresponding to the
direction D6, by symmetry
about the second axis y.
Annex A.5 shows an addressing matrix for elements distributed in accordance
with a square
pattern, which addressing matrix may be used for the elementary transducers of
array 41, for
example.
As the address, the numeral 1 or a minimal address value is attributed to an
elementary
transducer disposed at a corner of the square pattern. Element No 1 is in
column Cl of line Ll of
the table in annex A.5. The numeral 64, or a maximal address value, is
assigned an address for
the elementary transducer which is diametrically opposed to transducer No 1.
This element is
found in column C8 of line L8 in the table of annex A.5. From the element with
the minimal
address to the element with the maximal address, the elements are mutually
ordered by increasing
address values and disposed, in this order, in lines then in columns of the
same line. In other words,
CA 02893044 2015-05-27
19
transducers in the same line of the pattern have address values which follow
on from each other. In
the table of annex A.5, the address values are successive whole numbers in the
range 1 to 64.
Figure 8 shows a portion 80 of a multi-element sensor in a working position
with respect to
a portion 82 of a tube to be tested. The portion 80 corresponds to an array of
elementary
transducers which form a square pattern, for example analogous to the array 41
of Figure 6B. The
longitudinal direction of the tube has the reference Y. The direction normal
to the principal plane of
the portion 80 corresponds to a radial direction of the tube, denoted Z. The
direction normal to the
plane defined by the directions Y and Z is denoted X. The portion 80 is
disposed with respect to the
tube portion 82 in a manner such that the axes of symmetry y and x of the
pattern, corresponding to
the midpoint perpendiculars of the sides of the pattern, are respectively
aligned in the directions Y
and X.
By way of example, the elementary transducers of the portion 80 are organized
in
accordance with the addressing matrix described above with respect to annex
A.5. The portion 80 is
disposed with respect to the tube portion 82 such that the direction X of the
tube corresponds to a
.. first axis of symmetry x separating elements No 4 and No 5, while the
direction Y corresponds to a
second axis of symmetry separating elements No 25 and No 33. Elements No 1 to
No 8 are
disposed in the direction Y in the sense of this direction indicated by the
arrow in Figure 8. In other
words, the first axis of symmetry x of the portion 80 is disposed in the
transverse direction X of the
tube portion 82, while the second axis of symmetry y is disposed in the
longitudinal direction Y of
the tube.
Annex A.1.1 shows, in the form of a table, an example of delay values to be
applied to the
elementary transducers of the portion 80 in order to produce a burst in the
transverse direction X of
the tube portion 82, i.e. the direction D1 of Figure 6B. In the table of annex
A.1.1, the elementary
transducers are arranged in accordance with the addressing matrix defined by
annex A.5. The delay
value to be applied to the element No i is found in the table of annex A.I .1
at the same position
(line, column) as the address i in the table of annex A.5. As an example, the
delay to be applied to
CA 02893044 2015-05-27
element No 28 which is at the intersection of column C4 and line L4 of the
table of annex A.5, is
369 nanoseconds, which value can be found at the intersection of column C4 and
line L4 of the
table of annex A.1.1.
Figures 9A, 10A and 11A show the delay values of annex A.1.1 in the form of a
two-
5 dimensional rod diagram 84, the base of which coincides with the portion
80. Each bar or rod of the
diagram represents the delay of the respective elementary transducer which
coincides with its base.
The height of the rod, which is represented in the form of an extension in the
Z direction, is
proportional to the value of the delay to be applied to the elementary
transducer in question.
Figure 10A shows the diagram 84 viewed from the right, i.e. projected in a
plane with
10 directions X, Z and a normal direction Y. The elementary transducers
No's 8, 16, 24, 32, 40, 48, 56
and 64 can be distinguished in it.
The delay value applied increases linearly from transducer No 8, close to a
first side of the
square pattern, to transducer No 64, opposite to this first side. This linear
change in the applied
delays is shown diagrammatically by a straight line 86 in Figure 10A. Annex
A.1.1 shows that the
15 same linear increasing law is applied to the elementary transducers of
each alignment in the X
direction, i.e. to the elements of each of columns Cl to C8 of the table of
annex A.1.1.
Figure 11A shows the diagram 84 from the front, i.e. projected in a plane with
directions Y,
Z and a normal direction opposite to the direction X. The elementary
transducers No's 1, 2, 3, 4, 5,
6, 7 and 8 as well as the delay values applied to each elementary transducer
of the portion 80 can be
20 .. distinguished in it.
Identical delay values are applied to the elementary transducers disposed in a
symmetrical
manner with respect to the midpoint perpendicular of the portion 80 which
extends in the X
direction. In other words, this midpoint perpendicular partitions the portion
80 into two sub-sets of
elementary transducers to which two delay sub-laws are applied. A first delay
sub-law is applied to
.. the elementary transducers located to the left of this midpoint
perpendicular in Figure 11A, in
particular transducers No's 1 to 4, while a second delay sub-law is applied to
the elementary
CA 02893044 2015-05-27
21
transducers located to the right of this midpoint perpendicular, in particular
the transducers No's 5
to 8.
The value of the applied delay decreases linearly from transducer No 1, close
to a second
side of the square pattern, to transducer No 4, close to the midpoint
perpendicular of the first side.
This linear change in the applied delays is shown diagrammatically by a
straight line 88 on Figure
11A. Annex A.1.1 shows that the same decreasing linear law is applied to the
elementary
transducers of each alignment in the direction Y located on this same side of
the midpoint
perpendicular, i.e. in the table of annex A.1.1, to the elements of each of
the lines Ll to L8 located
at the intersection of columns Cl to C4.
The value of the applied delay increases linearly from transducer No 5, close
to the midpoint
perpendicular of the first side, to transducer No 8, opposite the second side.
This linear change in
the applied delays is shown diagrammatically by a straight line 90 in Figure
11A. The straight lines
88 and 90 are symmetrical with respect to the plane X, Z containing the
midpoint perpendicular of
the first side of the square pattern. Annex A.1.1 shows that the same
increasing linear law is
applied to the elementary transducers of each alignment in the Y direction
located on this same side
of the midpoint perpendicular, i.e. in the table of annex A.1.1, to the
elements of each of lines Li to
L8 located at the intersection of columns C5 to C8.
Once sequentially excited in accordance with the delay values discussed above,
the
elementary transducers of each of the two sub-sets jointly produce a
respective beam of ultrasonic
waves. The two beams which are produced respectively extend in two respective
directions, with
the references 92 and 94 in Figure 11A, each inclined at the same angle, as an
absolute value, with
respect to the direction of emission of the resultant beam, which direction is
denoted 96 in Figure
11A. Each of these two beams, which may be qualified as primary beams, diverge
from the line of
sight on moving away from the portion 80.
Figure 12 is analogous to Figure 8 and concerns the case of a burst in the
longitudinal
direction of the tube, i.e. in the Y direction of the tube, i.e. the direction
D3 of Figure 6A. Figure 12
CA 02893044 2015-05-27
22
shows the delay values to be applied to the elementary transducers of the
portion 80 in the form of a
rod diagram 120.
The portion 80 of the multi-element sensor is in an operating condition with
respect to a
portion 82 of a tube to be tested, in a manner analogous to that of Figure 8.
Compared with the
position of Figure 8, the portion 80 may have been displaced in the
longitudinal direction Y and/or
angularly with respect to the central axis of the tube portion 82, for example
because of a relative
helical movement between the tube and the sensor.
Annex A.1.2 shows the delay values to be applied to the elementary transducers
of the
portion 80 when they are organized in accordance with the addressing matrix
described above with
.. respect to annex A.5.
The same linear increasing law is applied to the elementary transducers of
each alignment in
the Y direction, i.e. to the elements of each of the lines Ll to L8 of the
table of annex A.1.2. The
value of the applied delay increases linearly from the transducers close to
one side of the square
pattern perpendicular to the Y direction to the transducers opposite this
side. The delay for the array
may depart from a strictly linear change because these values are rounded.
Taking into account the
resolution of the apparatus conventionally used in this field, of the order of
5 nanoseconds, these
roundings in practice have no effect on the detection of defects.
Identical delay values are applied to the elementary transducers disposed
symmetrically
with respect to the midpoint perpendicular of the portion 80 which extends in
the Y direction.
A similar linear decreasing law is applied to the elementary transducers of
each alignment in
the X direction located on this same side of the midpoint perpendicular, i.e.
in the table of annex
A.1.2, to the elements of each of columns Cl to C8 located at the intersection
of lines LI to L4.
Each time, the applied delay value decreases linearly from the transducer
closest to one side of the
square pattern perpendicular to the X direction to the transducer closest to
the midpoint
perpendicular of the second side.
CA 02893044 2015-05-27
23
A similar linear increasing law is applied to the elementary transducers of
each alignment in
the X direction located on this same side of the midpoint perpendicular, i.e.
in the table of annex
A.1.2, to the elements of each of columns CI to C8 located at the intersection
of lines L5 to L8.
Each time, the value of the applied delay increases linearly, from the
transducer closest to the
midpoint perpendicular of the second side to the transducer opposite the first
side.
Once sequentially excited in accordance with the delay values discussed above,
the
elementary transducers of each of the two sub-sets jointly produce a
respective beam of ultrasonic
waves. The two beams thus produced respectively extend in two respective
directions, each
inclined at the same angle, as an absolute value, with respect to the
direction of emission of the
resultant beam, as in the case of a burst in the longitudinal direction of the
tube.
Each of these two primary beams depart from the line of sight on moving away
from the
portion 80.
Reference will now be made to Figures 13A and 14.
Figure 14 is analogous to Figure 8 and concerns the case of a burst known as
an "oblique"
burst, i.e. in a direction inclined at 450 with respect to the axis of the
tube in a plane X, Y, i.e. the
direction D2 in Figure 6B. Figure 14 shows the delay values to be applied to
the elementary
transducers of the portion 80 in the form of a rod diagram 130. Figure 13A
shows the diagram 130
at a different viewing angle.
The portion 80 of the multi-element sensor is in a working position with
respect to a portion
82 of a tube to be tested, in analogous manner to that of Figure 8. Compared
with the position of
Figure 8, the portion 80 may have been displaced in the longitudinal direction
Y and/or angularly
with respect to the central axis of the tube portion 82, for example because
of a relative helical
movement between the tube and the sensor.
Annex A.1.3 shows the delay values to be applied to the elementary transducers
of the
portion 80 when they are organized in accordance with the addressing matrix
described above in
respect of annex A.5.
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Respective linear increasing laws are applied to the elementary transducers of
each
alignment in the Y direction, i.e. to the elements of each of lines Ll to L8
of the table of annex
A.1.3. Each time, the value of the applied delay increases linearly from the
transducers close to the
second side of the square pattern to the transducers opposite this second
side.
Respective linear increasing laws are applied to the elementary transducers of
each
alignment in the X direction, i.e. to the elements of each of columns Cl to C8
of the table of annex
A.1.2. Each time, the value of the applied delay increases linearly, from the
transducers close to the
first side of the square pattern to the transducers opposite this first side.
Once sequentially excited in accordance with the delay values discussed above,
the
elementary transducers of each of two sub-sets, separated from each other by
the diagonal of the
square pattern, jointly produce a respective ultrasonic wave beam. The two
beams produced
thereby respectively extend along two respective directions, each inclined at
the same angle, as an
absolute value, with respect to the direction of emission of the resultant
beam. Each of these two
primary beams diverge from the line of sight on moving away from the portion
80.
More generally, we now focus on the construction of a temporal excitation law
to allow an
oblique burst, for example in the second direction D2, in the case of the
first variation.
The burst direction D2 corresponds to an axis of symmetry of array 41, namely
one of the
diagonals of the square pattern. This diagonal defines two sub-sets of
elementary transducers, a
lower sub-set and an upper sub-set.
Because of the curvature of the tube to be tested, the delay values to be
applied to the first of
these sub-sets differs from the delay values to be applied to the symmetrical
transducers of the
second of these sub-sets.
Reference will again be made to Figure 7A.
Firstly, the first delay values Bi,j to be applied to the set of elementary
transducers Ci,j of
array 41 are computed such that these together emit a non-focused beam of
ultrasonic waves
deflected in a direction D2-p. These values are shown in a generic manner in
the table 70.
CA 02893044 2015-05-27
Reference will now be made to Figure 15.
Next, second delay values Ai,j to be applied to the set of elementary
transducers Ci,j of
array 41 are computed such that they jointly emit a non-focused beam of
ultrasonic waves deflected
in a direction D2+I3. These values are shown in a generic manner in the table
73.
5 Reference will now be made to Figure 16.
Next, one of the emission directions D2+I3 and D2-p is selected for the
diagonal of the
pattern of array 41, i.e. to finally be attributed to the transducers Ci,i of
the diagonal, whether these
are the first delay values Bi,i or the second delay values Ai,i. By
convention, the values which
maximize the delay to the transducers are selected to be those at each of the
ends of this diagonal.
10 By way of example, assume that in the case of the table 72 of Figure 16,
this criterion is verified by
the values A8,1 and A1,8 of table 73, and not the values B8,1 and B1,8 of
table 70, because the
energy requirement in the direction corresponding to elements A is higher,
linked to a weaker
response in this direction, which weakness derives from the geometry of the
tube.
The delay values of the law corresponding to the other corners are stored,
namely, in the
15 example, the second value A1,1 and the first value B8,8.
The second delay values Ai,j are attributed to the elements Ci,j of the upper
portion of the
array 41 as final delay values. The final delay values for the elements Ci,j
of the lower portion of
array 41 are deduced by linear interpolation starting from the first delay
values Bi,j. Initially, the
delay value for the corner corresponding to the portion of the array for which
the values are to be
20 determined is used in order to compute the delay values for the column
and the corresponding line
by linear interpolation. Thus, in each case an interpolation is carried out
between a value
determined for the diagonal and a value at the end of the line or column.
In other words, the values for half of the array corresponding to the diagonal
are retained,
while the other delay values are slightly modified by linear interpolation
starting from the initially
25 obtained values.
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26
Reference will now be made to Figures 9B, 10B, 11B and 13B which illustrate
the delay
values to be applied to elementary transducers in the second variation of the
invention.
In accordance with this second variation, the elementary transducers jointly
produce a
defocussed primary beam which is deflected with respect to the normal to the
principal plane of the
sensor. In order to compute the delay laws, a divergent beam may be considered
to be a beam with
an inverted focus, i.e. which has a virtual focal point located behind the
multi-element sensor in the
burst direction of the ultrasonic waves. In order to obtain a resultant
defocussed beam, delay values
which follow a parabolic law are preferably applied to at least some of the
elementary transducers
of the sensor. In a variation, these delay values are obtained from a law
which is close to a
.. parabolic law, for example corresponding to a plurality of linear laws each
approaching a portion of
the same parabola.
In addition to the obliquity of its primary direction, a divergent and
deflected beam may be
defined by the angle of deflection a and a value for the angle of opening of
the beam or divergence
angle 6.
The angle of deflection a is determined as a function of the diameter of the
tube to be tested
and of the distance separating the sensor from this tube. It is different for
each of the bursts in the
directions D1, D2 and D3. For bursts in the other directions, the values for
the angle of deflection a
are deduced from the symmetries of the pattern of the sensor.
The value for the angle of divergence 8 may be the same for the set of bursts,
irrespective of
the line of sight. The largest angle of divergence which is compatible with
the criteria of quality
and/or rapidity which are fixed, is sought. As an example, the value for the
angle of divergence
may derive from the fact that the number of bursts is fixed because of a
production requirement.
This gives rise to a minimum value for the angle of divergence 6. The value
for the angle of
divergence may also derive from a quality criterion, linked to the size of the
defects which one
wishes to be able to detect. This imposes a maximum value on the angle of
divergence 6. In the
CA 02893044 2015-05-27
27
majority of applications, the value for the angle of divergence 6 will be
selected so that is best
satisfies these criteria.
These parameters may be determined by successive tests, or by simulation, on
calibration
notches the respective orientation and depth of which correspond to defects
which are to be
investigated in the tube.
As an example, a value of 22.5 for the angle of divergence 6 may be used.
Figures 9B, 10B and 11B are analogous to Figures 9A, 10A and 11A. They show,
in the
form of a rod diagram 140, an example of the delay values to be applied to the
elementary
transducers of the portion 80 of the sensor in order to produce a burst in a
transverse direction X of
the tube portion 82. The transducers are addressed in accordance with annex
A.5. The delay values
are shown in the table of annex A.2.1.
Figure 10B shows the diagram 140 viewed from the right, i.e. projected in a
plane of
directions X, Z and the normal direction Y. The elementary transducers No's 8,
16, 24, 32, 40, 48,
56 and 64 may be distinguished.
The applied delay value increases in a parabolic manner from transducer No 8
close to a
first side of the square pattern, to transducer No 64 opposite this first
side. This parabolic change in
the applied delays is shown for a portion of the parabola 142 in Figure 10B.
Annex A.2.1 shows
that the same increasing law is applied to the elementary transducers of each
alignment in the X
direction, i.e. to the elements of each of columns Cl to C8 of the table of
annex A.2.1.
Figure 11B shows the diagram 140 in front view, i.e. projected in a plane of
directions Y, Z
and with a normal direction opposite to the X direction. The elementary
transducers No's 1, 2, 3, 4,
5, 6, 7 and 8 can be distinguished, along with the delay value applied to the
elementary transducers
of the portion 80.
Identical delay values are applied to the elementary transducers disposed in a
symmetrical
manner with respect to the midpoint perpendicular of the portion 80 which
extends in the X
direction. This midpoint perpendicular partitions the portion 80 into two sub-
sets of elementary
CA 02893044 2015-05-27
28
transducers to which two delay sub-laws are respectively applied. A first
delay sub-law is applied
to the elementary transducers located on one side of this midpoint
perpendicular, in particular to
transducers No's Ito 4 located on the left of this midpoint perpendicular in
Figure 1113. A second
delay sub-law is applied to the elementary transducers located on the other
side of this midpoint
perpendicular, in particular to transducers numbers 5 to 8 located on the
right of this midpoint
perpendicular in Figure 11B.
The applied delay value follows a parabolic law from transducer No 1, close to
one side of
the square pattern, to transducer No 8, distanced from this side. This change
in the applied delays
is shown diagrammatically for a portion of the parabola 144 in Figure 11B.
The delay value decreases from transducer No 1 to transducer No 4. Annex A.2.1
shows
that the same parabolic decreasing law is applied to the elementary
transducers of each alignment in
the Y direction located on the same side of the midpoint perpendicular, i.e.
in the table of Annex
A.2.1, to the elements of each of lines Ll to L8 situated at the intersection
of columns Cl to C4.
The applied delay value increases from transducer No 5, close to the midpoint
perpendicular, to transducer No 8. Annex A.2.1 shows that the same parabolic
increasing law is
applied to the elementary transducers of each alignment in the Y direction
situated on this same side
of the midpoint perpendicular, i.e. in the table of Annex A.2.1, to the
elements of each of lines Ll to
L8 situated at the intersection of columns C5 to C8.
Once sequentially excited in accordance with the delay values discussed above,
the
elementary transducers of each of the two sub-sets jointly produce a beam of
ultrasonic waves
which extends in the X direction and which diverges with increasing distance
from the portion 80 of
the sensor.
The table of annex A.2.2 shows the delay values which may be applied to the
elementary
transducers in order to jointly produce a divergent beam of ultrasonic waves
which extends in the Y
direction.
CA 02893044 2015-05-27
29
Identical delay values are applied to the elementary transducers disposed
symmetrically
with respect to the midpoint perpendicular of the portion 80 which is disposed
in the X direction.
This midpoint perpendicular partitions the portion 80 into two sub-sets of
elementary transducers, to
which two delay sub-laws are respectively applied.
Figure 13B is analogous to Figure 13A and concerns the case of a burst termed
"oblique",
i.e. in a direction inclined at 45 with respect to the axis of the tube in a
plane X,Y, i.e. the direction
D2 of Figure 6B. Figure 13B shows the delay values to be applied to the
elementary transducers of
the portion 80 in the form of a rod diagram 150.
The portion 80 of the multi-element sensor is in a working position with
respect to a portion
82 of a tube to be tested, in analogous manner to that of Figure 8. Compared
with the position of
Figure 8, the portion 80 may have been displaced in the longitudinal direction
Y and/or angularly
with respect to the central axis of the tube portion 82, for example because
of a relative helical
movement between the tube and the sensor.
Annex A.2.3 shows the delay values to be applied to the elementary transducers
of the
portion 80 when they are organized in accordance with the addressing matrix
described above in
relation to annex A.5.
Respective parabolic increasing laws are applied to the elementary transducers
of each
alignment in the Y direction, i.e. to the elements of each of lines LI to L8
in the table of annex
A.2.3. Each time, the value of the applied delay increases in a parabolic
manner, from the
transducers close to one side of the square pattern to the transducers
opposite this side with respect
to the X direction.
Respective parabolic increasing laws are applied to the elementary transducers
of each
alignment in the X direction, i.e. to the elements of each of columns Cl to C8
of the table of annex
A.2.3. Each time, the value of the applied delay increases in a parabolic
manner from the
transducers close to one side of the square pattern to the transducers
opposite this side with respect
to the Y direction.
CA 02893044 2015-05-27
Once sequentially excited in accordance with the delay values discussed above,
the
elementary transducers of each of two sub-sets, separated from each other by
the diagonal of the
square pattern, jointly produce an ultrasonic wave beam extending in the
direction D2 and diverging
with respect to this direction with motion away from the sensor.
5 In an analogous manner to that described above with respect to the first
variation, it is
possible to use the various symmetries of the sensor pattern to deduce certain
delay laws from laws
computed for other burst directions.
We shall now turn to the second embodiment of the invention, in which the
elementary
transducers jointly produce a divergent non-deflected resultant beam which
extends in the direction
10 normal to the principal plane of the sensor. In this second embodiment,
a single burst of ultrasonic
waves is carried out. The divergent beam may be defined by a beam opening
angle or angle of
divergence 6.
In this embodiment, the first axis of symmetry x and the second axis of
symmetry y of the
pattern of array 41 define four sub-sets of elementary transducers to which
the same delay sub-law
15 is applied each time. The table of annex A.4 indicates an example of
delay values to be applied to
the elementary transducers in order to generate a resultant beam which is
divergent and non-
deflected with respect to the direction normal to the active surface of the
sensor. In this case, this
divergent beam results from a defocussed primary beam.
Each time, the delay value increases with distance from each of the first axis
of symmetry x
20 and the second axis of symmetry y.
Two variations of a first embodiment of the invention have just been described
which can be
used to carry out sequential bursts in distinct directions. In each of these
bursts, a broad portion of
the tube to be inspected is "insonified", producing a resultant divergent
beam. A large portion of
the tube is covered by the ultrasonic waves resulting from the burst. The
deflection of the resultant
25 beam can be used to detect the presence of defects with a corresponding
orientation with respect to
the tube. In a first variation, the divergent and deflected beam results from
at least two non-focused
CA 02893044 2015-05-27
31
and deflected primary beams respectively generated by a sub-set of elementary
transducers. In a
second variation, the divergent and deflected beam results from at least one
divergent and deflected
primary beam.
A second embodiment which can be used to produce a single burst in order to
detect the
.. presence of defects irrespective of their inclination has also just been
described. Here again, the
divergent nature of the beam means that a broad portion of the tube to be
tested can be insonified.
Each time, the symmetry of the sensor is used to compute delay sub-laws which
are applied
to a sub-set of elementary transducers.
The ultrasonic waves received in response to a burst are processed in order to
detect in them
any echoes resulting from the presence of defects or imperfections.
In a first development of the invention, processing the received ultrasonic
waves comprises
applying a delay law termed the "inverse" of the delay law which served to
emit the ultrasonic
waves during a burst. In other words, processing of the received ultrasonic
waves comprises
applying a specific delay value Ri,j to the signal received at each elementary
transducer Ci,j of the
sensor. The delay value on reception Ri,j is computed from the delay value
Ei,j applied to the
elementary transducer Ci,j on emission, using the following formula:
Ri,j = max(Ei,j) - Ei,j
The value max (Ei,j) represents the maximum delay value of the delay values
applied to the
elementary transducers Ei,j of the sensor.
Computation of an inverse delay law may be carried out using software which
has allowed
the computation of the emission delay law using a spreadsheet, or manually.
Thus, in the inspected
tube section, defects or imperfections orientated in a manner corresponding to
the direction of the
burst are principally detected. It is also possible to detect therein defects
which are slightly inclined
with respect to this direction, limited by the aperture of the primary beam,
generally having a
.. smaller signal to noise ratio.
32
Advantageously in a second development, processing of the received ultrasonic
waves
comprises application of the technique known from the document WO 03/050527.
For each burst,
the received signals are processed by applying several inverse delay laws,
each corresponding to an
obliquity value included in the primary beam. These inverse delay laws are
conventionally
computed using the technique known from WO 03/050527. As an example, the
various obliquity
values are distinguished from each other by a value of 5 . Following one
burst, in the inspected
section of tube, defects orientated in different obliquities included in the
primary beam resulting
from this burst are detected with, in each case, a signal to noise ratio which
is practically identical.
In this second development, the defects for which the orientation is both
included in the aperture of
the ultrasonic wave beam corresponding to the burst and inclined with respect
to the obliquity of the
principal direction of this beam, are detected with a better signal to noise
ratio. In other words, this
second development improves detection of fine defects. In other words, the
device has better
resolution in this case.
As an example, with an emitting beam with an angle of opening of 40 , and
application of
delay laws corresponding to respective inclinations of 5 , defects inclined at
0, 5 , 10 , 15 ,
with respect to the principal direction of the beam are particularly
effectively detected.
Reference will now be made to Figures 17, 18A and 18B.
These Figures represent zones known as "insonification" zones, i.e. struck by
at least a
portion of one of the ultrasonic beams used to inspect all of the possible
orientations of defects.
20 These figures result from simulations.
Figure 17 corresponds to a reference configuration. In this configuration, 72
bursts have
been carried out, each time in a direction with an obliquity of 5 with
respect to the preceding burst.
Figure 17 shows an insonification zone at -6 decibels, or focal zone, where
the maximum
energy is concentrated. The zone is in the form of an elliptical ring and is
practically
homogeneous. The insonification zone measures approximately 50 millimetres by
30
millimetres.
CA 2893044 2020-04-08
33
Figure 18A corresponds to the configuration in accordance with the first
variation of the first
embodiment in the case in which the "paintbrush" technique is applied, during
post-processing.
The parameter p is 150. Only 8 bursts have been necessary to obtain the result
of Figure 18A. The
amplitudes are practically homogeneous for all lines of sight. Figure 18A
shows an insonification
zone which appears almost as an elliptical ring. The insonification zone
measures
approximately 50 millimetres by 35 millimetres, which is very close to the
reference zone for Figure
17.
Figure 18B corresponds to the configuration in accordance with the second
embodiment in
the case in which the so-called "paintbrush" technique is applied during post-
processing. The beam
is defocussed at 25 millimetres. Figure 18B shows an insonification zone which
is elliptical in
appearance. The decibel zone measures 80 millimetres by 60 millimetres, which
is close to the
reference zone of Figure 17. The zone at -6 decibels is broader than for the
first embodiment. The
central portion of the ellipse is also insonified, although this zone is of
less use for inspection of the
tube.
Compared with Figure 18A, Figure 18B shows a more homogeneous insonification
zone
185 corresponding to a practically identical level of energy for all of the
inspected directions.
Compared with Figure 18B, Figure 18A shows a central zone of the ellipse which
is not
insonified, which means that the signal to noise ratio is better. However, the
second embodiment
= offers a faster inspection rate.
= 20 An insonification diagram corresponding to the second
variation of the first embodiment has
not been shown. Such a diagram has a broader elliptical insonification zone
than those shown in '
Figures 17, 18A and 18B. It results in a poorer signal to noise ratio and
relative energy loss.
However, that diagram has greater homogeneity in the lines of sight, which
facilitates inspection. In
particular, it is not necessary to compensate for the energy differences
between the various lines of
sight.
CA 2893044 2020-04-08
CA 02893044 2015-05-27
34
The Applicant has succeeded in testing a tube in a satisfactory manner as to
the existence of
defects orientated in any manner in just eight bursts, while retaining the
usual advance speeds used
in the art.
A device which can be used to test a tube as regards the existence of defects
at any
inclination at a speed compatible with production rates has just been
described. This increase in
speed results primarily from the fact that repositioning of the sensor with
respect to the tube
between two successive bursts in different directions is of no effect. In the
device in question, for
each line of sight, beams of ultrasonic waves are generated by respective
portions of a square multi-
element sensor which diverge with respect to the line of sight and which join
up as they strike the
outer surface of the tube to be tested.
This device is not limited to a sensor with a square pattern. It may be used
in an equivalent
manner with a sensor in which the elementary transducers are organized into
the shape of a
rectangle. A sensor may also be used in which the elementary transducers are
distributed in a circle.
In this case, the portions of the pattern dedicated to each divergent beam
correspond to an angular
sector of the pattern. As an example, successive bursts may be produced on the
various sectors,
with delay laws which can be computed using software analogous to that known
as "CIVA".
The invention may also be viewed as a process for testing a long metallurgical
product, in
particular a tube, in which the device described is used repeatedly to fire it
in each of the directions
D1 to D8.
The invention may also be viewed as a method for testing metallurgical
products in which a
burst of ultrasonic waves is produced in a line of sight with the aid of an
ultrasonic sensor
comprising a plurality of elementary transducers operable independently of
each other and
distributed in accordance with a two-dimensional pattern by applying a
temporal excitation law to
the elementary transducers, this temporal excitation law comprising one or
more sub-laws to
sequentially excite each of at least one sub-set of the plurality of
elementary transducers, each sub-
law being arranged such that excitation of the elementary transducers of the
corresponding sub-set
CA 02893044 2015-05-27
produces a respective primary beam of ultrasonic waves, and the sub-law or
laws also being
arranged such that said burst corresponds to a beam of ultrasonic waves
resulting from the
respective beams of primary ultrasonic waves of the sub-sets of elementary
transducers, said
resultant beam diverging about the line of sight on moving away from the
ultrasonic sensor.
5 A value for the angle P of 20 has been described by way of example, in
particular in the
context of a burst in direction Dl. The value of this angle may be adapted as
a function of the size
of the elementary transducers. As an example, the value of this angle may be
increased if the size of
the transducers is decreased.
In accordance with one aspect of the invention, sub-laws are applied in a
manner so as to
10 simultaneously excite the elementary transducers disposed mutually
symmetrically with respect to a
preferential direction of said pattern. Although the axes of symmetry of a
square pattern have been
described as preferential directions, the invention is not in any way limited
to this particular
embodiment. Patterns with different shapes each have corresponding
preferential directions for
these patterns. As an example, a pattern in which the transducer elements are
configured into
15 angular sectors and are symmetrically disposed with respect to certain
radial directions, for example
inclined at 120 with respect to each other, have these radial directions as
preferential directions.
More particularly, an ultrasonic sensor with a matrix shape comprising 64
elements
distributed in accordance with a square 8-element by 8-element pattern has
been described. The
invention is not limited either to this number of elements or to this
particular pattern. Each time, an
20 ultrasonic burst can be used to inspect a longitudinal section of a tube
as to the existence of defects.
In order to test the entire length of this tube, the tube and the ultrasonic
sensor may be displaced
with respect to each other. In a development of the invention, it is possible
to use ultrasonic sensors
disposed one beside the other in the longitudinal direction of the tube to be
tested. By operating the
sensors simultaneously with respect to each other, for each relative position
of the sensor and tube,
25 it is possible to inspect a longer section of this tube. In yet another
development, it is possible to use
a multi-element array ultrasonic sensor wherein the pattern has been broken
down into elementary
CA 02893044 2015-05-27
36
sub-patterns and each sub-pattern is operated simultaneously with the others
in the manner of an
isolated ultrasonic sensor. This means that a longer portion of the tube to be
tested is inspected. As
an example, an ultrasonic sensor of this type could comprise 256 elements
distributed in a
rectangular 8 element by 32 element pattern. By positioning this sensor such
that the long side of
the pattern corresponds to the length of the tube, then virtually, 8 multi-
element square sensors each
being an 8 element by 8 element square are disposed along the length of the
tube. And these 8
sensors could be operated simultaneously to inspect a large length of the tube
for each burst.
The invention is not limited to the embodiments described above by way of
example only,
but encompasses any variation which the skilled person could envisage.
CA 02893044 2015-05-27
37
Annex A.1 : Delay values corresponding to first embodiment, first variation
(in nanoseconds)
Annex A.1.1 : burst in direction DI
Cl C2 C3 C4 C5 C6 C7 C8
Li 127 85 43 0 0 43 85 127
L2 250 208 166 123 123 166 208 250
L3 373 331 289 246 246 289 331 373
L4 495 453 411 369 369 411 453 495
L5 617 575 533 490 490 533 575 617
L6 738 697 654 612 612 654 697 738
L7 859 817 __ 775 732 732 775 817 859
L8 979 938 895 853 853 895 938 979
Annex A.1.2 : burst in direction D3
Cl C2 C3 C4 C5 C6 C7 C8
Li 114 290 464 639 813 986 1159 1332
L2 77 252 427 601 775 949 1122 1294
L3 39 214 389 563 737 911 1084 1256
L4 0 175 350 525 699 872 1045 1217
L5 0 175 350 525 699 872 1045 1217
L6 39 214 389 563 737 911 1084 1256
L7 77 252 427 601 775 949 1122 1294
L8 114 290 464 639 813 986 1159 1332
CA 02893044 2015-05-27
38
Annex A.1.3 : burst in direction D2
Cl C2 C3 C4 C5 C6 C7 C8
Li 0 157 314 471 627 782 937 1091
L2 116 230 387 544 700 855 1010 1164
L3 233 346 460 616 772 928 1083 1237
L4 349 462 575 688 844 1000 1155 1309
L5 466 578 691 803 916 1071 1226 1381
L6 582 694 806 918 1030 1142 1297 .. 1451
L7 699 810 922 1033 1145 1256 1367 1522
L8 815 926 1037 1148 1259 1370 1481 1592
CA 02893044 2015-05-27
39
Annex A.1.4 : burst in direction D4
Cl C2 C3 C4 C5 C6 C7 C8
Li 815 926 1037 1148 1259 1370 1481 1592
L2 699 810 922 1033 1145 1256 1367 1522
L3 582 694 806 918 1030 1142 1297 1451
L4 466 578 691 803 916 1071 1226 1381
L5 349 462 575 688 844 1000 1155 1309
L6 233 346 460 616 772 928 1083 1237
L7 116 230 387 544 700 855 1010 1164
L8 0 157 314 471 627 782 937 1091
CA 02893044 2015-05-27
' 40
Annex A.2 : Delay values corresponding to first embodiment, second variation
(in nanoseconds)
Annex A.2.1 : burst in direction D1
Cl C2 C3 C4 C5 C6 C7 C8
Ll 135 67 23 0 0 23 67
135
L2 251 185 140 118 118 140 185
251
L3 389 323 279 257 257 279 323
389
L4 548 482 438 416 416 438 482
548
L5 726 661 618 596 596 618 661
726
L6 924 . 860 817 796 796 817 860
924
L7 1141 1078 1036 1014 1014 1036 1078
1141
L8 1376 1314 1272 1251 1251 1272 1314
1376
Annex A.2.2 : burst in direction D3
Cl C2 C3 C4 C5 C6 C7 C8
Li 133 194 277 381 506 652 817
1002
2 67 128 211 316 441 587 754
939
L3 22 84 167 272 398 544 711
897
L4 0 62 145 250 376 523 690
876
L5 0 62 145 250 376 523 690
876
L6 22 84; 167 272 398 544 711
897
L7 67 128 211 315 441 587 754
939
L8 133 194 277 381 506 652 817
1002
CA 02893044 2015-05-27
41
Annex A.2.3 : burst in direction D2
Cl C2 C3 C4 C5 C6 C7 C8
Li 0 30 83 158 255 373 512 672
L2 56 86 139 213 310 428 567 726
L3 134 164 216 291 387 504 642 801
L4 234 264 316 390 485 602 739 897
L5 355 385 436 510 604 720 857 1013
L6 497 527 578 651 745 860 995 1150
L7 660 689 740 812 905 1019 1153 1307
L8 842 871 922 993 1085 1198 1330 1483
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Annex A.3 : Transposition laws for delay values
Direction of Delay values Transformation
burst
Dl Computed None
D2 Computed None
D3 Computed None
D4 Deduced from values for D2 Bi,j := Bi, n+1 -j
D5 Deduced from values for al Bi,j := Bn+l-i, j
D6 Deduced from values for D4 Bi,j := Bn+l-i, j
D7 Deduced from values for D3 Bi,j := Bn+l-i, j
D8 Deduced from values for D6 Bi,j := Bi, n+1 -j
CA 02893044 2015-05-27
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Annex A.4 : Delay values corresponding to second embodiment (in nanoseconds)
Cl C2 C3 C4 C5 C6 C7 C8
LI 582 456 365 310 310 365 456 582
L2 456 330 239 184 184 239 330 456
L3 365 239 148 93 93 148 239 365
L4 310 184 93 38 38 93 184 310
L5 310 184 93 38 38 93 184 310
L6 365 239 148 93 93 148 239 365
L7 456 330 239 184 184 239 330 456
L8 582 456 365 310 310 365 456 582
CA 02893044 2015-05-27
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Annex A.5 : Addressing matrix for elementary transducers of a sensor
Cl C2 C3 C4 C5 C6 C7 C8
L I No I No 2 No 3 No 4 No 5 No 6 No 7 No 8
L2 No 9 No 10
Noll No 12 No 13 No 14 No 15 No 16
L3 No 17 No 18
No 19 No 20 No 21 No 22 No 23 No 24
L4 No 25 No 26
No 27 No 28 No 29 No 30 No 31 No 32
L5 No 33 No 34
No 35 No 36 No 37 No 38 No 39 No 40
L6 No 41 No 42
No 43 No 44 No 45 No 46 No 47 No 48
L7 No 49 No 50
No 51 No 52 No 53 No 54 No 55 No 56
L8 No 57 No 58
No 59 No 60 No 61 No 62 No 63 No 64
=
