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JPS6358156

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DESCRIPTION JPS6358156
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
apparatus for generating ultrasonic waves in a noncontacting manner on a test material and is
used, for example, for nondestructive testing of internal defects in the test material using
ultrasonic waves. Contactless ultrasonic wave generator. [Prior Art] When the surface of an
object that absorbs light is instantaneously irradiated with a high energy beam such as a laser
beam, an ultrasonic wave is generated on the object by the thermal excitation of the irradiation
unit, and the laser beam is inspected for internal defects. It is known in Japanese Patent
Application Laid-Open No. 54-9679 that an inspection material to be inspected is irradiated with
ultrasonic waves to be generated on the surface of the inspection material and a reflection echo
from a defect is detected to detect an internal defect. FIG. 3 is a schematic view showing the
configuration of a conventional non-contact type ultrasonic wave generator, and in the figure, 1
is an inspection material to be inspected for an internal defect, that is, an ultrasonic wave
generation target. A laser light source 2 for generating a laser beam is provided above the
material to be inspected 1 at an appropriate distance from the material to be inspected 1, and the
driving of the laser light source 2 is adjusted by a pulse signal from the switching circuit 3. Ru.
When the laser light emitted from the laser light source 2 is irradiated on the surface of the
inspection material l, the irradiated part of the laser light is thermally expanded instantly due to
the absorption of light. As a result, a local thermal stress is caused in the material to be inspected
1, a mechanical stress is generated in the material structure of the material to be inspected 1 by
the stress, a sound source is generated, and an elastic wave, that is, an ultrasonic wave is
generated. [Problems to be Solved by the Invention] In order to generate strong ultrasonic waves,
it is necessary to irradiate high-power laser light. However, when a high output laser beam is
irradiated to the material to be inspected, the thermal shock on the surface of the material to be
inspected becomes large, and the material to be inspected is damaged. In addition, there is a
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problem that it is difficult to set an optimal light amount for l of the laser light for generating the
ultrasonic wave of the maximum energy within a range where the inspection material is not
damaged. The present invention has been made in view of the above circumstances, and there is
no risk of damage to the material to be inspected even if it is irradiated with an excessive high
energy beam, and it is the largest within the scope of not damaging the material to be inspected.
An object of the present invention is to provide a noncontact ultrasonic wave generator capable
of irradiating a test material with a high energy beam necessary to generate an ultrasonic wave
of energy. [Means for Solving the Problems] The noncontact ultrasonic wave generator according
to the present invention comprises a thermometer for measuring the temperature on the surface
of the test material irradiated with the high energy beam, and a high value based on the
temperature measurement value. And control means for controlling the amount of energy beam.
[Function] The thermometer measures the temperature of the surface of the test material
irradiated with the high energy beam.
And if the measured value is lower than the reference value, the amount of the high energy beam
is increased noting that the test material is not damaged,-If the blade side fixed value is higher
than the reference value, the m inspection material is damaged, the high energy The control
means controls the amount of high energy beam to be irradiated to the test material so as to
reduce the amount of beam. Then, the beam of the highest energy within the range that does not
damage the test material is adjusted to irradiate the test material. Thus ultrasound generation
takes place at an ideal level. The present invention will be specifically described below based on
the drawings showing the embodiments. FIG. 1 is a schematic view showing the configuration of
an embodiment of the non-contact type ultrasonic wave generator according to the present
invention, and in the figure, 1 is a test material to be ultrasonically generated. The laser light
source 2 momentarily generates a laser beam which is a high energy beam to generate an
ultrasonic wave at an appropriate distance from the test material 1 above the test material 1, the
generated ultrasonic wave is An interferometer 6 is provided for detecting the surface
displacement of the material 1 by utilizing the interference of light, and a thermometer 5 is
provided for measuring the temperature of the surface irradiated with the laser light. The
thermometer 5 is a two-color thermometer that detects the ratio of the amount of light of two
different wavelengths emitted from the test material 1 and converts it to a temperature, and
measures the surface temperature of the test material 1 The measured value is converted into an
electrical signal and output. The laser light source 2 is connected to a switching circuit 3 that
outputs a pulse signal for controlling intermittent driving of the laser light source 2 to the laser
light source 2. Further, a laser modulator 4 for modulating the amplitude of the laser beam
emitted from the laser light source 2 is provided between the inspection material 1 and the laser
light source 2. The laser modulator 4 is made of, for example, a liquid crystal that changes the
light transmittance according to the level of the applied electric signal, and the output of the
thermometer 5 is given to the laser modulator 1. The laser variation aj J unit 4 is adapted to
adjust the degree of modulation for the laser light. Next, the operation will be described. When a
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pulse signal from the switching circuit 3 is input to the laser light source 2, the laser light source
2 emits a laser beam in synchronization with the pulse signal. The laser light is modulated in its
amplitude by the laser modulator 4 and the light quantity is adjusted to momentarily illuminate
the surface of the inspection material 1. Then, a local heat stress generated on the surface of the
inspection material 1 generates a sound source, and an ultrasonic wave is generated radially
from the sound source. Then, the interferometer 6 irradiates the test material 1 with light and
measures the intensity of interference light between the irradiated light and the reflected light
from the surface of the test material 1 displaced by the generated ultrasonic wave to detect an
ultrasonic wave. .
That is, the interferometer 6 detects the surface displacement of the test material surface due to
the reflection of the generated ultrasonic wave on the surface of the test material or the internal
defect, and measures the thickness of the test material 1 or detects the internal defect. When the
laser light is irradiated to the inspection material 1, the thermometer 5 detects the light emitted
from the laser light irradiation site of the inspection material 1 and measures the temperature of
the surface of the inspection material 1. The output of the thermometer 5 is input to the laser
modulator 4. Here, the laser modulator 4 is set in advance in accordance with the quality of the
test material 1 as a reference value based on the rise value of the surface temperature as to
whether or not the test material 1 is damaged. Then, when the input is lower than the reference
value, the laser modulator 4 increases the amplitude of the laser light by a certain amount or
more to increase the laser light to be irradiated. On the other hand, when the input is higher than
the reference value, the amplitude of the laser beam is reduced by a fixed period to reduce the
laser beam to be irradiated. Then, for example, when the temperature measurement value
obtained at the temperature d15 makes the A-1 / 2 half value -1-turn when the amplitude of the
laser light is gradually increased, the test material 1 is damaged, Conversely, the amplitude of the
laser beam is reduced to reduce the laser beam. On the other hand, when the amplitude of the
laser beam is gradually reduced, if the temperature measurement value obtained by the
thermometer 5 falls below the reference value, no damage occurs to the material to be inspected
1-conversely The amplitude of the laser beam is increased to increase the laser beam. In this way,
the amount of laser light to be emitted is converged to the optimum one. And after that, a laser
beam is irradiated to the to-be-tested material 1 by the quantity of the range which damage does
not generate ¦ occur ¦ produce. FIG. 2 is a schematic view showing the configuration of another
embodiment of the device of the present invention. In this embodiment, unlike the above
embodiment, the thermometer 5 has no laser modulator and controls the pulse signal output
from the switching circuit 3 to the laser light source 2 to control the output itself of the laser
light source 2. That is, the thermometer 5 controls the pulse width of the pulse signal based on
the obtained temperature measurement value, and suppresses the amount of the laser beam
irradiated to the test material 1 to such an extent that no damage occurs. In the present
embodiment, the case where the test material is not damaged is described. However, the present
invention is not limited to this, and the optimum amount may be used for the test material whose
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surface is dirty or uneven. Can be emitted. Even if the surface is soiled but the surface has
irregularities, the color properties of the surface do not contribute to the condition of the surface,
so that the present invention can irradiate an optimum amount of laser light to the test material.
[Effects] As described in detail above, according to the present invention, there is no possibility
that the inspection material will be damaged due to excessive irradiation of high power laser
light.
Moreover, it becomes easy to generate the ultrasonic wave of the maximum energy within the
range where the damage does not occur to the inspected material. Furthermore, since the
occurrence of tl flaws accompanying the laser beam irradiation is always confirmed, it is possible
to completely prevent the occurrence of the damage even when the ultrasonic wave is generated
on the inspection material online. In addition, since the surface condition of the material to be
inspected does not affect the color properties of the surface, the laser light to be irradiated can
be controlled to an optimum light amount even when the surface is dirty or uneven.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a schematic view of a noncontact ultrasonic wave generator according to the present
invention, FIG. 2 is a schematic view of another embodiment, and FIG. 3 is a schematic view of a
conventional noncontact ultrasonic wave generator.
1 ... inspection material 2 ... laser light source 3 ... switching circuit 4 ... laser modulator 5 ...
thermometer 6 ... one thousand #il. In the drawings, the same reference numerals indicate the
same or corresponding parts.
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