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DESCRIPTION JPH10227775

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DESCRIPTION JPH10227775
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electron scanning probe (phased array probe) for oblique angle flaw detection used, for example,
in an automatic flaw detector for inspecting internal defects in steel welds. is there.
[0002]
2. Description of the Related Art Ultrasonic bevel flaw detection is widely used, for example, as a
method for nondestructive inspection of the presence or absence of internal defects in steel
welds. In this ultrasonic oblique flaw detection, a probe is used that transmits ultrasonic waves
obliquely to the surface of the object and receives ultrasonic waves reflected from internal
defects. At this time, in order to accurately determine the position of the defect, it is necessary to
propagate the ultrasonic wave into the object with a predetermined flaw refraction angle.
[0003]
By the way, in recent years, a steel material having low temperature toughness enhanced by a
special manufacturing method is manufactured. The shear wave velocity of the steel material
produced by such a production method is different from the shear wave velocity (3230 m / s) of
a standard test piece produced by a general production method. If the shear wave velocity is
different, the angle at which the ultrasonic wave is actually refracted on the surface of the object
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deviates from the predetermined flaw refraction refraction angle, so the position of the defect
determined by flaw detection will include a large error. For this reason, when flaw detection is
performed on a steel material manufactured by such a special manufacturing method, it is
necessary to obtain the shear wave velocity in advance. Conventionally, as an array flaw
detection apparatus capable of measuring the shear wave velocity of a subject, one disclosed in
Japanese Patent Application Laid-Open No. 8-43367 has been proposed. In this array flaw
detector, a calibration transducer is incorporated in the probe separately from the array
transducer in which a plurality of ultrasonic transducers are arranged. The ultrasonic wave
generated from the calibration vibrator is received by the array vibrator, and the ultrasonic
vibrator having the largest sound pressure among the array vibrators is identified, whereby the
shear wave velocity or the shear wave ultrasonic wave of the object is detected. The refraction
angle of
[0004]
However, in the conventional array flaw detection apparatus, it is necessary to provide a
calibration vibrator separately from the array vibrator, and further a drive circuit for driving the
calibration vibrator is also required. As a result, there is a problem that the device becomes
complicated. There is also the problem of reflection from the calibration transducer.
[0005]
The present invention has been made based on the above-mentioned circumstances, and it is an
electronic scanning probe for oblique angle flaw detection that can easily measure the shear
wave velocity of an object with a simple configuration without providing a calibration vibrator.
The purpose is to provide
[0006]
[Means for Solving the Problems] In order to achieve the above object, an electronic scanning
probe for oblique angle flaw detection according to the present invention comprises an array
transducer in which a plurality of ultrasonic transducers are arranged along a predetermined
direction. And reflecting the ultrasonic waves generated by driving a part of the plurality of
ultrasonic transducers formed on the housing to which the array transducer is attached and a
part of the front of the flaw detection direction of the housing. It is characterized by having a
reflecting surface which makes the reflected ultrasonic wave enter into a flaw detection surface
of a subject at a predetermined angle, and makes it propagate in the opposite direction to the
flaw detection direction.
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[0007]
In the present invention, ultrasonic waves generated by using a part of a plurality of ultrasonic
transducers are made to enter the reflection surface, whereby the ultrasonic waves reflected by
the reflection surface are in the direction opposite to the flaw detection direction in the object. To
propagate.
Therefore, by receiving this ultrasonic wave by the array transducer and specifying the ultrasonic
transducer having the largest sound pressure, the shear wave velocity of the subject can be easily
obtained.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will
be described below with reference to the drawings.
FIG. 1 is a schematic perspective view of an electronic scanning probe for oblique angle flaw
detection according to an embodiment of the present invention. The electronic scanning probe
for oblique angle flaw detection shown in FIG. 1 generates an ultrasonic wave that propagates
obliquely to the flaw detection surface of the object, and a case 10 having one peak portion
formed thereon, An array transducer 20, a reflection preventing surface 30, and a reflecting
surface 40 are provided. In the present embodiment, it is assumed that such a bevel flaw
detection electronic scanning probe is used in an automatic flaw detection apparatus for
inspecting an internal defect of a steel welded portion.
[0009]
The housing 10 has a flat bottom facing the flaw detection surface of the subject, and a first
slope 11 and a second slope 12 which are left and right slopes of the peak. For the housing 10,
for example, a polyimide resin having a longitudinal wave velocity v 'of 2830 m / s is used. The
array transducer 20 is formed by arranging a plurality of ultrasonic transducers 21 along a
predetermined direction. The plurality of ultrasonic transducers 21 are disposed on the second
slope 12 of the housing 10 at a constant pitch interval p. Further, in the plurality of ultrasonic
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transducers 21, the number k (k (k) is sequentially set from the transducer provided on the
lowest side of the second slope 12 to the transducer provided on the peak side of the peak. = 1,
2, ..., N) are attached. In the array transducer 20, for example, an operation of sequentially
applying a drive pulse to each pair of ultrasonic transducers 21 in a set of 16 ultrasonic
transducers 21 adjacent to each other is considered, one by one. The scanning is performed
electronically by performing on each set selected in a staggered manner. When flaw detection is
performed, it is necessary to adjust the propagation direction of the ultrasound generated by the
array transducer 20 so that the ultrasound propagating in the housing 10 propagates in the
object at a predetermined flaw refraction angle. Incidentally, as shown in FIG. 1, the side of the
flaw detection surface of the subject to be flawed is referred to as a flaw detection direction.
[0010]
The anti-reflection surface 30 is for preventing the ultrasonic waves generated by the array
transducer 20 from directly returning to the array transducer 20. In the present embodiment, the
reflection preventing surface 30 is formed by inserting a large number of wedge-shaped Vshaped grooves 31 in the first inclined surface 11 of the housing 10. As a result, the ultrasonic
wave incident on the portion where the V groove 31 is inserted is scattered or reflected in a
direction different from the incident direction. The reflection preventing surface may be formed,
for example, by sticking a sound absorbing material or the like on the first slope 11 instead of
inserting the V groove on the first slope 11.
[0011]
The reflective surface 40 is a flat surface formed on a part of the front surface of the case 10 in
the flaw detection direction. Here, by cutting a portion close to the bottom surface of the first
inclined surface 11 of the housing 10, the reflecting surface 40 is formed to be a predetermined
flat surface described later. The reflecting surface 40 is used to determine the shear wave
velocity of the subject and the refraction angle of the shear wave ultrasonic wave. That is, by
causing an ultrasonic wave generated using a part of the array transducer 20 to be incident on
the reflecting surface 40, the ultrasonic wave reflected by the reflecting surface 40 is detected on
the flaw detection surface of the subject at a predetermined incident angle. It is incident and
propagates in the inside of the subject in the direction opposite to the flaw detection direction.
Then, the ultrasonic waves reflected once at the back surface of the subject are received by the
array transducer 20 to determine the shear wave velocity of the subject and the angle of
refraction of the transverse ultrasonic waves. Details of how to find the shear velocity and the
angle of refraction will be described later. The propagation direction of the ultrasonic wave
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generated by the array transducer 20 is determined so that the ultrasonic wave propagates
through the subject at a predetermined flaw refraction angle based on the shear wave velocity of
the subject and the refraction angle of the shear wave ultrasonic wave thus determined. adjust.
[0012]
Next, a method of designing the electronic scanning probe for oblique angle flaw detection
according to the present embodiment will be described. FIG. 2 is a view for explaining how to
design the oblique scanning electronic scanning probe. This design is performed using a standard
test piece as the subject 2. The standard test piece is, for example, a steel material having a
thickness t of 19 mm and a velocity v0 of transverse waves propagating inside of 3230 m / s.
The case where the flaw detection of the subject 2 is performed in the range of one reflection
from the direct light with the ultrasonic wave frequency of 5 MHz and the flaw refraction angle
θ 0 of the ultrasound wave propagating in the subject 2 being 70 degrees is considered.
[0013]
First, the inclination angle α of the second slope 12 with respect to the bottom surface of the
housing 10 is determined. When each ultrasonic transducer 21 formed on the second slope 12
generates a longitudinal ultrasonic wave in the normal direction, the inclination angle α is a
longitudinal ultrasonic wave propagating in the housing 10 Is the incident angle incident on the
flaw detection surface. The longitudinal ultrasonic wave incident on the flaw detection surface of
the subject 2 at the incident angle α is refracted at the flaw refraction angle θ 0 and propagates
in the subject 2. Therefore, between the incident angle α and the flaw refraction angle θ 0 The
Snell's law v '/ sin α = v 0 / sin θ 0 holds. From this, α is about 52.4 degrees. Therefore, the
inclination angle of the second slope 12 of the housing 10 is set to about 52.4 degrees.
[0014]
Next, the inclination angle γ of the reflective surface 40 with respect to the normal direction of
the bottom surface of the housing 10 is determined. In the present embodiment, predetermined
16 ultrasonic transducers arranged on the side closer to the apex of the peak portion of the
housing 10 are used in the direction of the angle β with respect to the normal direction of the
ultrasonic transducers. By generating a sound wave, the ultrasonic wave is made to be incident
on a substantially central portion of the reflection surface 40. Here, the reason why the
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ultrasonic waves are made to enter the substantially central portion of the reflecting surface 40
is to make the ultrasonic waves efficiently enter the reflecting surface 40 because the ultrasonic
waves generally have a certain extent. At this time, the tilt angle of the reflecting surface 40 is
such that the ultrasonic wave reflected by the reflecting surface 40 propagates in the object 2 at
the flaw detection refraction angle θ 0, that is, enters the flaw detecting surface of the object 2
at an angle α. Let's define γ. A simple geometric calculation using FIG. 2 shows that the
inclination angle γ of the reflective surface 40 is β / 2. In practice, by determining an
appropriate angle β with respect to the angle α, a set of ultrasonic transducers that generate
ultrasonic waves to be incident on the reflection surface 40 is specified.
[0015]
The length L of the portion forming the array transducer 20 was determined as follows. Now, in
order to perform flaw detection on the subject 2 within the range of single reflection, since the
plate thickness t is 19 mm and the flaw refraction angle θ 0 is 70 degrees, the scanning width
needs to be at least about 2t · tan θ 0 0104 mm. is there. The length L0 obtained by projecting
this scanning width onto the second slope 12 is 104 mm · cos α ≒ 63 mm. By the way, in the
present embodiment, since the transverse acoustic velocity of the subject 2 is obtained by using
the reflection surface 40, the array vibration is considered in consideration of the portion of the
ultrasonic transducer for receiving the ultrasonic wave reflected by the reflection surface 40. The
length L of the portion forming the child 20 needs to be somewhat longer than L0. However, the
ultrasonic waves generated for flaw detection from the 16 ultrasonic transducers on the side
closer to the apex of the peak of the ridge portion of the casing 10 are positions P 0 at which the
ultrasonic waves reflected by the reflection surface 40 enter the object 2 By designing the first
inclined surface 11 of the housing 10 so as to be located forward of the flaw detection direction
with respect to the position P incident on the subject 2, the ultrasonic wave reflected by the
reflection surface 40 can be A plurality of ultrasonic transducers located on the lower side of the
peak can sufficiently receive. Therefore, in the present embodiment, it is sufficient to set the
length L of the portion forming the array vibrator 20 to about L0 ≒ 63 mm.
[0016]
Next, a method of determining the shear wave velocity of the subject 2 and the refraction angle
of the shear wave ultrasonic wave using the electronic scanning probe for oblique angle flaw
detection of the present embodiment will be described. FIG. 3 is a view for explaining a method
of determining the shear wave velocity of the object 2 and the refraction angle of the shear wave
ultrasonic wave by using the oblique angle flaw detection electronic scanning probe. First, the
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standard test piece described above is used as the subject 2. First, ultrasonic vibration is
generated by driving predetermined 16 ultrasonic transducers 21 arranged on the side closer to
the top of the peak of the housing 10 in order from a smaller number by a predetermined drive
timing. A longitudinal ultrasonic wave is generated in the direction of the angle β with respect to
the normal direction of the element 21. The longitudinal ultrasonic waves are reflected by the
reflection surface 40 and then enter the standard test piece at an incident angle α. The
longitudinal ultrasonic waves are mode-converted to transverse ultrasonic waves, and propagate
in the standard test piece at a refraction angle θ 0 in the direction opposite to the flaw detection
direction. After that, the shear wave ultrasonic waves are reflected once on the back surface of
the standard test piece, and when incident on the flaw detection surface of the standard test
piece, the mode is converted into longitudinal wave ultrasonic waves. The longitudinal wave
propagates in the housing 10 at a refraction angle α and is received by the array transducer 20.
Then, a receiving device (not shown) of the automatic flaw detection apparatus identifies the
ultrasonic transducer 21 having the highest sound pressure. For example, it is assumed that the
number of the ultrasonic transducer 21 having the highest sound pressure is n0.
[0017]
Next, using the subject 2 to be actually tested, the same operation as described above is
performed. That is, longitudinal ultrasonic waves are generated in the direction of the angle β
with respect to the normal direction of the ultrasonic transducers 21 by using predetermined 16
ultrasonic transducers 21. The longitudinal ultrasonic waves are reflected by the reflection
surface 40 and then enter the subject 2 at an incident angle α, and then mode-converted into
transverse ultrasonic waves. The shear wave ultrasonic waves propagate through the object 2 at
a refraction angle θ 1. Here, if the shear wave velocity of the subject 2 is the same as the shear
wave velocity of the standard test piece, the refraction angle θ1 is the same as the angle θ 0,
while the shear wave velocity of the subject 2 is the shear wave velocity of the standard test
piece If it is different, the refraction angle θ1 is different from the angle θ0. The ultrasonic
wave propagating inside the subject 2 in the opposite direction to the flaw detection direction at
the refraction angle θ 1 is reflected once by the back surface of the subject 2 and then enters
the flaw detection surface of the subject 2 to be a longitudinal wave mode. Convert. The
longitudinal wave propagates in the housing 10 at a refraction angle α and is received by the
array transducer 20. The receiving device of the automatic flaw detection apparatus identifies the
ultrasonic transducer 21 having the highest sound pressure. For example, it is assumed that the
number of the ultrasonic transducer 21 having the highest sound pressure is n1.
[0018]
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At this time, the distance y0 in the flaw detection direction in which the ultrasonic wave has
passed through the inside of the standard specimen and the distance y1 in the flaw detection
direction in which the ultrasonic wave has passed through the inside of the object 2 are given by
y0 = 2t ・ tanθ0y1 = 2t ・ tanθ1. Be Here, it was assumed that the thickness t of the subject 2
was the same as the thickness t of the standard test piece. On the other hand, the difference
between y1 and y0 is given by y1-y0 = np / cos alpha. Here, n = n0-n1 and p is a pitch interval
between adjacent ultrasonic transducers. By substituting the first two equations into the third
equation, the refraction angle θ1 of the subject 2 when the ultrasonic wave is incident at the
incident angle α is θ1 = tan−1 (tanθ0 + n · p / ( It can be determined from 2t · cos α)).
[0019]
Further, according to Snell's law on the flaw detection surface of the standard test piece and
Snell's law on the flaw detection surface of the subject 2, v0 / sin θ0 = v '/ sin αv1 / sin θ1 = v'
/ sin α holds. From this, the shear wave velocity v1 in the subject 2 can be obtained from v1 =
v0 ・ sinθ1 / sinθ0 using the above-mentioned refraction angle θ1.
[0020]
Next, the operation of the automatic flaw detection apparatus using the electronic scanning
probe for oblique angle flaw detection of the present embodiment will be described. First, as
described above, ultrasonic waves generated by using a part of the array transducer 20 are
reflected by the reflecting surface 40 to propagate in the direction opposite to the flaw detection
direction. Then, the ultrasound is received by the array transducer 20, and the ultrasound
transducer 21 having the largest sound pressure is identified, whereby the refraction angle θ1
of the subject 2 when the ultrasound is incident at the incident angle α The transverse acoustic
velocity v1 of the subject 2 is determined. Next, based on the determined refraction angle .theta.1
and shear wave velocity v1, the propagation direction of the ultrasonic wave generated from the
array transducer 20 is determined so that the flaw detection refraction angle of the object 2
becomes .theta.0. Then, the drive timing of each set of ultrasonic transducers is adjusted so that
ultrasonic waves can be generated in the determined propagation direction.
[0021]
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Next, flaw detection of the subject 2 is performed. First, transmission pulses are sequentially
applied from the first ultrasonic transducer to the sixteenth ultrasonic transducer at the adjusted
drive timing. The longitudinal ultrasonic waves thus generated propagate in a predetermined
direction and enter the flaw detection surface of the subject 2 and then propagate in the flaw
detection direction at a flaw refraction angle θ 0 as transverse wave ultrasonic waves in the
subject 2. If there is a wrinkle or the like in the propagation path of the transverse ultrasonic
wave propagating in the subject 2, the transverse ultrasonic wave is reflected there, and the
component of the reflected transverse ultrasonic wave that is returned along the path opposite to
the incident path is super It is received by the sound transducer.
[0022]
Then, after the time required for the ultrasonic wave to reciprocate between the ultrasonic
transducer 21 and the welding portion elapses, similarly from the second ultrasonic transducer
to the 17th ultrasonic transducer, Apply a transmit pulse. As described above, after ultrasonic
waves are generated by sequentially applying transmission pulses to a new set of 16 ultrasonic
transducers selected by shifting the ultrasonic transducers one by one, the ultrasonic waves
reflected by the defect are generated. Repeat the operation to receive. The transmission
operation is sequentially applied to the last set of 16 ultrasonic transducers, and the ultrasonic
wave reflected by the defect is received to complete the flaw detection operation.
[0023]
In the electronic scanning probe for oblique angle flaw detection according to the present
embodiment, the reflection surface is provided on a part of the front surface of the case in the
flaw detection direction, so that the super generated by using a part of a plurality of ultrasonic
transducers. When sound waves are made incident on the reflecting surface, the ultrasonic waves
reflected by the reflecting surface propagate in the object in the opposite direction to the flaw
detection direction. Therefore, by receiving this ultrasonic wave by the array transducer and
specifying the ultrasonic transducer having the largest sound pressure, the shear wave velocity
of the subject can be easily obtained. Therefore, unlike the conventional probe, it is not necessary
to provide a vibrator for calibration, and the apparatus can be simplified.
[0024]
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The present invention is not limited to the above embodiment, and various modifications can be
made within the scope of the invention. In the above embodiment, the case where a plurality of
ultrasonic transducers are arranged in a predetermined direction on the second slope is
described using the case having a peak portion formed by the first slope and the second slope.
For example, as shown in FIG. 4, an oblique-angle flaw detection electronic scanning probe in
which a plurality of ultrasonic transducers are arranged in a step may be used.
[0025]
The electronic scanning probe for oblique angle flaw detection shown in FIG. 4 comprises a
casing 10a having a saw-tooth shaped surface formed by repeating a first inclined surface 11a
and a second inclined surface 12a at a predetermined pitch, and a second An array transducer
20a in which a plurality of ultrasonic transducers 21a are arranged in a predetermined direction
on each of the slopes 12a, a reflection preventing surface 30a, and a reflecting surface 40a. The
reflection preventing surface 30a is formed on the upper side in the flaw detection direction
front surface of the casing 10a, and the reflective surface 40a is formed on the lower side in the
flaw detection direction front surface. In this case, as in the above embodiment, the inclination
angle α of the second slope 12a with respect to the bottom surface of the housing 10a and the
inclination angle γ of the reflecting surface 40a with respect to the normal direction of the
bottom surface of the housing 10a are Determined. For example, while setting the inclination
angle α of the second inclined surface 12a to about 52.4 degrees, the ultrasonic wave generated
from a part of the array transducer 20a is directed at the angle β with respect to the normal
direction of the ultrasonic transducer In the case of propagation, the inclination angle .gamma. Of
the reflecting surface 40a is set to .beta. / 2.
[0026]
As described above, according to the present invention, since the reflecting surface is provided
on a part of the front surface in the flaw detection direction of the casing, the super generated by
using a part of a plurality of ultrasonic transducers. When sound waves are made incident on the
reflecting surface, the ultrasonic waves reflected by the reflecting surface propagate in the object
in the direction opposite to the flaw detection direction, so these ultrasonic waves are received by
the array transducer and the maximum sound pressure is obtained. By identifying the ultrasonic
transducer having the following, it is possible to easily determine the shear wave velocity of the
object, and therefore, there is no need to provide a transducer for calibration as in the
conventional probe, and the apparatus is simplified. It is possible to provide an electronic
scanning probe for oblique angle flaw detection that can achieve the
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