JPH11326078A - Stress wave detecting device for element area and detecting method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove the influence of noise generated from a whole device and to realize a high accurate measurement by irradiating a laser beam on a local element area surface of a fixed substance and detecting a motion speed at the area surface by Doppler effect. SOLUTION: A first incident laser 3 of an instrumentation laser output device 1 is incident on a first light wave guide 4 and a second incident laser 5 of a heating laser output device 2 is incident on a second light wave guide 6. The laser 5 emitted from a tip end opening 7 of the light wave guide 6 irradiates a local heat input area surface 8 to heat-input. The laser 3 emitted from a tip end opening 9 of the light wave guide 4 irradiates around the center point of the local heat input area 8 and reflects. A modulated laser L Doppler- modulated enters from the tip end opening 9 to a frequency analyzer 12 through the light wave guide 4 and a return path. A portion of the laser 3 and the returning modulated laser L are Doppler-interfered at an interference optical system by the frequency analyzer 12 and the strength of a light by the interference is measured and calculated to obtain a motion speed spectrum of the local heat input surface 8 based on the Doppler effect of the laser 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device and method for detecting a stress wave in an element region for detecting internal stress in a local region of a solid object, and more particularly, to liquid sealing in which high energy is injected. The present invention relates to an apparatus and a method for detecting stress waves in an element region for appropriately evaluating the pressure response of a rigid container structure and contributing to the development of the container structure. More specifically, stress wave detection in the element region for contributing to the development of the container structure by appropriately evaluating the pressure response of the rigid container structure when a high-intensity charged particle beam is injected into the liquid inside from the outside of the container. The present invention relates to an apparatus and a detection method thereof.

[0002]

2. Description of the Related Art There is a demand for a study on the structural strength of a rigid container in which high-energy particle beams from the sun are received or generated in space or the like. In order to promote such research, it is preferable to manufacture a test rigid container and artificially prepare an environment in which particle beams are generated inside. In Europe, neutron source development plan ES using high intensity proton accelerator ES
S is in progress.

When a large amount of scattered neutrons are generated by externally irradiating a proton beam into a liquid metal sealed in a metal container in a pulsed manner, the container itself absorbs a part of the incident energy and generates a stress wave in the container wall. Occurs simultaneously, the temperature of the liquid absorbing the other part of the incident energy instantaneously rises, and a shocking pressure wave is generated in the liquid. It is presumed that the two waves interact at the wall to generate a new shock wave, and that the two subsequently occurring waves will add and the repetitive waves will repeat periodically in the vessel.

[0004] Such a shock wave causes cavitation in the liquid, and cavitation erosion should occur on the wall surface. The synergistic effect of such a phenomenon and the repetitive stress may eventually cause the container to break. In order to manufacture a container that can withstand such a severe environment, it is important to know the pressure response of the wall receiving the shock wave.

In order to measure the amount of displacement of an object that is displaced under pressure, a pressure sensor using a piezo element is commonly used. A Doppler interferometer is commonly used as a sensor for differentially detecting a change in speed. Optical fibers have been used to cause Doppler interference in remote locations in explosive environments. The piezo element is not useful at all in an environment where a large amount of drift electrons due to the above-mentioned irradiation with proton beams exist, but Doppler interference using an optical fiber can be safely measured even in an environment where a large amount of neutrons are present. Such fiber optic Doppler interferometers may be used to enable dynamic pressure measurements in vessels in the above-described environment. That is, it is recognized that a Doppler interferometer can be used to measure the pressure response of a heat input container structure in which high energy is instantaneously injected into a sealed liquid.

[0006] A technique for appropriately and easily detecting the dynamic internal stress of a solid object is a generally required technical problem. Ultrasonic deep wound means covering the whole area of the object where the input wave is measured cannot know physical properties such as local elastic modulus. The elastic modulus of an object that is placed in an environment for a long time is variable. Measurement of physical properties such as the elastic modulus of the object without knowing the existence of the defective portion is sufficient for measurement of a local region. There is a strong demand for a more accurate measurement of physical properties by knowing the physical properties of the local area without locally changing the external environment and making the environmental change reach the entire area.

[0007]

SUMMARY OF THE INVENTION The present invention has been made based on such a technical background, and achieves the following objects.

SUMMARY OF THE INVENTION An object of the present invention is to detect a stress wave in an element region in which the physical properties of a local region of a solid object can be measured accurately without changing the external environment locally and making the environmental change not extend to the whole region. An apparatus and a method thereof are provided.

Another object of the present invention is to provide an element which can locally and precisely measure the physical properties of a local region of a solid object without changing the external environment locally and making the environmental change reach the entire area. An object of the present invention is to provide an apparatus and a method for detecting a stress wave in a region.

It is still another object of the present invention to provide a method for measuring stress waves in an element region in which an object can be detached from an environment in which the object is located and a property which changes while the object is located can be locally measured. A detection device and a method thereof are provided.

Still another object of the present invention is to separate a laser for heat input for causing a local environment change and a laser for a Doppler interferometer for detecting a stress wave so that the laser for heat input detects the Doppler effect. An object of the present invention is to provide a stress wave detecting device and a method for detecting stress waves in an element region which do not affect accuracy.

Still another object of the present invention is to provide a stress wave detecting device for an element region which has a large time density of energy to be injected and enables measurement of pressure response due to instantaneous / impact heat input, and a method of detecting the same. It is in.

[0013] The more specific objects of the present invention will become more apparent through its embodiments and examples.

[0014]

An apparatus and method for detecting a stress wave in an element region according to the present invention can measure a stress wave in a local element region of a solid object. The solid object includes a plastic body, an object whose hardness is to be measured,
For example, it includes agar-like objects, various plastics, metals, semiconductors, crystals such as diamond, semi-solid liquid crystals, and the like. The outer surface of the local region of the solid object is irradiated with a laser beam. Heat is input to the local area by the laser irradiation. Such heat input causes thermal diffusion starting from the local region. The rate of diffusion is higher than the rate of heat conduction, and stress is generated from the local region.
Propagating in a dimension. The stress wave propagates from the light irradiation surface of the specific element region in the radiation direction and simultaneously along the surface along the surface.
Propagation also in the dimension direction. The stress wave is reflected in a boundary region of the object. This boundary region is a back surface opposite to the heat input surface or an interlayer surface formed in the object, a hole / cavity surface, or the like.

Although the reflected stress wave returns to the heat input surface, it is desirable that heat conduction does not reach the reflecting surface until the stress wave is reflected. Before the heat transfer reaches the reflective surface, the stress wave is reflected many times at both interfaces. The object repeatedly expands and contracts due to the repeated propagation of the reflected stress wave. An arbitrary minute region in a disk-shaped object having a uniform thickness vibrates several times with a center plane whose distance in the thickness direction is equidistant from both boundary surfaces as a coordinate origin. For example, it vibrates several times. This vibration characteristic is determined by the elastic modulus of the object
Depends on Young's modulus. Therefore, the vibration characteristic, that is, the velocity spectrum can be measured before the heat transfer to the entire measurement area is completed.

If the object to be measured is the above-mentioned disk-shaped object, the vibration width of the heat input surface depends on the distance from the center plane, and the velocity in the radiation direction of the surface depends on the distance and the elastic modulus. Has a value that depends on The speed can be measured using a measuring laser. The principle of the measurement is
Doppler interference. Doppler interferometers are generally well-known measuring means and can be easily obtained, but those manufactured by the applicant company to which one of the present inventors belongs can be used as they are.

The heat input laser and the measurement laser may be the same. If the heat input of the heat input laser affects the detection of the Doppler effect of the same laser for measurement, it is preferred that the heat input laser and the measurement laser are independent. Even when large heat input energies are required, they are preferably separate. When it is necessary to stabilize the wavelength of the measurement laser, a He-Ne gas laser is used as the laser on the one hand, and a semiconductor laser is used on the other hand to increase the power of the heat input laser. Can be

The irradiation time (length of time) of the second laser beam for heat input is preferably controlled. The control of the irradiation time can prevent deterioration of the measurement accuracy of the physical properties of the object which is not affected by the heat if the propagation of heat due to the heat input and the measurement area are widened. In extreme terms, the heat input laser is preferably a linear pulse that rises instantaneously and immediately falls immediately. Changes in the characteristics of the speed spectrum obtained by changing the irradiation time of the heat input laser can be used for more accurate estimation of the speed spectrum. Means of such control is a means for changing the duration of DC input to the semiconductor laser oscillation element,
It is means for controlling the open time of the blocking plate for blocking the continuous wave beam. If the energy of the measurement laser is sufficiently smaller than the energy of the heat input laser,
Irradiation to the heat input surface can be continued at all times. In such a case, the measurement is completed at the moment when the heat input laser is irradiated (for example, 10 minus 6 seconds), so that the velocity spectrum of the surface of the object can be obtained in real time at an arbitrary time (instantaneous time). .

It is preferable that both the first laser for measurement and the second laser for heat input are guided to the local area surface to be measured by optical fiber fibers. For example, the internal stress of the reactor wall of a fusion reactor can be measured remotely during operation of the reactor.
The local heat input region may be a region where the laser beam emitted from the mouth of the optical waveguide is directly irradiated, and it is not necessary to condense and irradiate with a lens.

The measurement is not limited to the real-time measurement described above. Measuring the degradation of metallic materials exposed to large amounts of neutrons can be performed in two stages. Comparison of the pre-exposure velocity spectrum with the post-exposure velocity spectrum after prolonged exposure can provide an estimate of the degradation of the material. If a sample row of many velocity spectra is manufactured by changing the exposure time, the degree of deterioration corresponding to one of the sample rows can be estimated.

The apparatus and method for detecting a stress wave in an element region according to the present invention are also effective for measuring a defect in a layer portion of a two-layered object. The stress wave is also reflected in the boundary region between the two layers. If there is a cavity or a bonding defect on the reflection surface, the location of that portion can be detected. For example, it is possible to detect a defective contact position such as an electric contact formed of two layers of silver and copper.

[0022]

According to the apparatus and method for detecting a stress wave in an element region according to the present invention, the physical properties of one object made of a uniform material are the same as those of a local region. By vibrating the part without vibrating the whole, there is no influence of noise generated from the whole, so that more accurate measurement is possible. The equipment for performing the measurement is simple. Analysis is not required for each element, and measurement can be performed for each element.

The ease of measurement does not depend on the size of the object to be measured. The measurement can be performed in an environment filled with electric particles, and the measurement can be directly used for the measurement of the transverse stress wave. The present invention allows measurement of the physical properties of any object placed in any environment, regardless of its background. Measurement of arbitrary element regions of an object formed from various materials is possible.

[0024]

Next, an embodiment of a device for detecting a stress wave in an element region according to the present invention will be described. FIG.
Shows a specimen that has been idealized to facilitate calculations. This test piece has the advantage that any object can be approximately replaced by such an object, not only for easy calculation.

According to the method of the present invention for measuring a local region in principle, a stress wave isotropically propagates from a local heat input region to a two-dimensional region parallel to the heat input surface. While heat is also diffused isotropically, stress waves propagate from the heat input area in a direction perpendicular to the heat input surface (thickness direction) almost uniformly, and heat is also diffused uniformly in that direction. The overall physical properties of the object can be determined from the data analyzed assuming that any local region is substantially equivalent to a disk or disk.

The disk 10 of the embodiment for calculation has a thickness of 0.
5mm, 10mm diameter stainless steel (SUS31
6). A laser beam for heat input having a diameter of 100 microns is irradiated in the normal direction to a local heating area near the center point on one side. It is not necessary to focus the laser to a smaller diameter beam.

As shown in the figure, instantaneous irradiation of the heat input laser is practically impossible, and is actually performed at a certain rising angle (in a lamp shape). The rise time is 1 microsecond, and irradiation is performed for 2 microseconds. With this irradiation, the local irradiation area is instantaneously, for example,
Heat from room temperature (25 degrees C) to 100 degrees.

FIG. 2 shows an optical system for measurement. As a laser source, a first laser (for measurement) output device 1 and a second laser (for heat input) output device 2 are used. The first incident laser 3 output from the first laser output device 1 enters a first optical waveguide (first optical fiber) 4 having a total reflection cylindrical surface corresponding to the wavelength.

The second incident laser 5 output from the second laser output device 2 enters a second optical waveguide (second optical fiber) 6 having a total reflection cylindrical surface corresponding to the wavelength. The first optical waveguide 4 and the second optical waveguide 6 may be coaxial. The first optical waveguide 4 and the plurality of second optical waveguides 6 may be fixed close to each other. The plurality of second optical waveguides 6 are connected to the first
It can be arranged around the optical waveguide 4.

Since the wavelength of the second incident laser 5 is at least ten times the wavelength of the first incident laser 3, the first optical waveguide 4
And the second optical waveguide 6 can be formed coaxially. Second
The second incident laser 5 emitted from the tip opening 7 of the optical waveguide 6
Is irradiated on the local heat input area surface 8 as it is. First
First incident laser 3 exiting from opening 9 at the tip of optical waveguide 4
Is directly irradiated near the center point of the local heat input area surface 8.

The modulated laser L reflected by the heat input area surface 8 and subjected to Doppler modulation enters the first optical waveguide 4 again from the tip opening 9, passes through the return path 11, and enters the frequency analyzer 12. The first laser output device 1 is usually incorporated in a frequency analyzer 12. First laser output device 1
A part of the first laser 3 emitted from the laser and the return modulated laser L interfere with the interference optical system in the frequency analyzer 12. This interference is Doppler interference.

The velocity spectrum based on the Doppler effect of the first laser 3 on the heat input area 8 is obtained by measuring and calculating the intensity of light due to the Doppler interference. The velocity spectrum is a velocity component (vertical velocity component) in the direction of the incident axis of the first laser on the heat input area surface 8.

When the first incident laser 3 is incident on the heat input area surface 8 at a right angle, the absolute velocity of the vibrating heat input area face 8 is measured. The first incident laser 3 includes a frequency analyzer 12
It is common to modulate within. In this embodiment, a two-beam method is used so that the modulation cycle and the speed spectrum are not synchronized.

As the second laser output device 2, a high-output semiconductor oscillation device is used. The first laser output device 1 is composed of He-Ne gas having excellent wavelength stabilization.
Laser oscillators are used. First incident laser 3
The second incident laser 5 having a longer wavelength is converted into heat and absorbed more by the stainless steel. Frequency analyzer 12
Is a well-known technically established detection system, and its description is omitted.

FIG. 3 shows the effective effective diffusion front surface Sn of heat conduction by heat input over time. The virtual effective heat diffusion front surfaces Sn that advance by 1 / N · microsecond (n is an integer of 1 to 7) are indicated by virtual lines. The disk 10 is virtually divided into eight equal parts in the thickness direction. FIG.
When the energy of heat input shown therein is absorbed by the disk 10 from the heat input area surface 8, stress is immediately generated in the heat input area face 8, and a stress wave based on the generation is generated in the thickness direction (vertical direction).
Proceed to a.

When the diffusion front end surface S1 (1 is the lower right subscript in the figure) reaches the position shown in the figure, the stress wave is reflected by the reflection surface 13 which is the back surface of the disk 10, and returns to the heat input region surface 8. I have. When the diffusion front end surface S2 (1 is the lower right suffix in the figure) reaches the position shown in the figure, the stress wave is reflected on the reflection surface 13 which is the back surface of the disk 10 for the second time and heat is input again (second time). It returns to the area plane 8. Similarly, when the diffusion front end surface S7 reaches the illustrated position, the stress wave is reflected seven times by the reflection surface 13 which is the back surface of the disk 10, and returns to the heat input region surface 7 for the seventh time.

The four equally-divided positions are symmetrical with respect to the center plane 14,
The symbols are indicated by P1 to P4 in the figure. The center position is P
It is indicated by 0. FIG. 4 shows a velocity spectrum at each of the positions P1 to P4. Each of the positions P1 to P4 vibrates with respect to the immovable origin position P0. Since the surface of the disk 10 at the position P4 (two locations) also vibrates, the disk 10 sandwiched between both surfaces expands and contracts.

That is, the disk 10 expands and contracts in the vertical direction a between the position indicated by the imaginary line 15 and the position indicated by the imaginary line 16. The position P1 corresponds to the vibration starting position of the substance at the stationary position P1 that vibrates between the position indicated by the virtual line 15 and the position indicated by the virtual line 16.

In FIG. 4, the horizontal axis represents time (unit is microsecond).
The vertical axis indicates the speed. FIG. 4 shows four speed spectra V1 to V4. FIGS. 5 and 6 also show a velocity spectrum similar to that of FIG. Figures 4, 5, 6
Is that the Young's modulus E of the material of the disk 10 is 20 GPa, 30 G
The respective speed spectra are shown for Pa and 40 GPa.

In the case shown in FIG. 5, the velocity spectrum V1 indicates the velocity of the stress wave that has just reciprocated seven times between both surfaces of the disk 10 when the diffusion front surface S7 at 100 degrees has advanced to the position shown in FIG. Is shown. That is, seven waves appear as shown in FIG. The non-constant spacing between the first three waves is due to the lamp illumination shown in FIG. In the case where the diffusion front surface S7 coincides with the reflection surface 13, the number of waves is 7 at the maximum. In some cases, the speed of the stress wave drops sharply.
Even when such a rapid decrease in speed occurs, a phenomenon similar to that when the second heat input is performed occurs. Therefore, although the absolute value of the speed approaches zero, the second value having a similar shape to the speed spectrum Vn is obtained. A velocity spectrum V'n appears. In this measurement method, the velocity spectrum has two measurement chances with one heat input. The average speed of the speed spectrum is approximately 1 km /
sec.

As described above, when the Young's modulus increases, the wave number increases. If the wave number is determined by experiment, conversely, the Young's modulus can be determined by calculation. The data shown in FIG. 6 indicates that the Young's modulus changes with the deterioration of the material. Figure 7 shows that the Oak Ridge Institute in the United States
The Young's modulus (vertical axis) obtained by an irradiation experiment on SUS316 by ER is shown. The horizontal axis indicates the neutron irradiation dose. Since the irradiation amount corresponds to the deterioration of the material, the deterioration of the material progresses rapidly when the irradiation amount is increased.

Since the crystal grain size of stainless steel is about 50 microns, when a laser spot having a diameter smaller than this is irradiated, slip deformation occurs in the crystal structure, anisotropy appears in the material, and the elastic modulus is measured. Accuracy decreases. Therefore, it is preferable to irradiate a laser beam that is not too powerful to a region having a diameter of 100 microns.

8 and 9 show another embodiment of the object to be measured. This measurement object is the structure of the shell 20 of the neutron source which is the background of the present invention. One end is directed toward the spherical surface 22 of the substantially cylindrical shell of the hemispherical shell 21, and a proton beam parallel to the axial direction of the shell is irradiated so that protons enter the shell. Due to the heat input by this incidence, a stress wave of mercury in the shell is generated, and a stress is also generated from the hemispherical shell portion.

The elastic modulus of the shell can be measured based on the stress response due to the stress wave inside and the stress in the shell, but it is more reasonable to know the deterioration of the shell from the stress measurement of the shell alone. . 1.5 GeV proton beam hitting the mercury nucleon 2
No. 3 causes nuclear spallation by collision of particles to generate a large amount of neutrons, and induced by the charged particles, the shell surface is charged to a high pressure.

In a situation where such a high-voltage and large-capacity drift current is generated, it is impossible to detect distortion by the piezo element. Before the proton irradiation, the velocity spectrum of the surface based on the stress wave in such a shell is detected. The shell after the first irradiation is taken out from the irradiation position in the irradiation equipment, the radiation dose is sufficiently reduced, and the second measurement of the velocity spectrum is performed according to the present invention. After a further irradiation of a certain amount of protons again, the third measurement of the velocity spectrum is carried out at a similar interval.

By repeating such a measurement, a sample sequence of the velocity spectrum is created. From the velocity spectrum sequence of such a sample sequence, it is possible to know the state of deterioration of the shell, and it is possible to know the time when the shell should be replaced.

FIGS. 8 and 9 show the distribution of measurement points. The diameter of the hemispherical shell is 20 cm. The thickness is 2 cm. Approximately 10
It is divided into 0 parts (for example, 113 parts). Divide the hemisphere into ring-shaped strips of equal width, and divide one strip into 4
When divided into 8, 12,..., It is divided into 113.

The center part 2 of the area thus divided is
A second incident laser is applied to a circular region 24 having a diameter of cm, and a first incident laser is applied to a smaller region 25 at the center of the region. It is preferable to actually measure the velocity spectrum of the 113 spherical shell elements by such incidence. According to the method of the present invention, it is not necessary to measure during neutron irradiation, and it is sufficient to measure the physical properties of an empty container shell containing no mercury.

Mathematical analysis when heat is input to an element region of an object having a two-dimensional spread in a circular shape like the test piece in FIG. 1 is basically important. When analyzed in two dimensions, when the initial pressure field acts on the center of the circular object, the time t (>
The propagation behavior of the pressure wave in 0) is conveniently expressed in cylindrical coordinates. The wave equation of pressure p (r, t) is
In the cylindrical coordinate system, it is represented by the following equation (2). In the following formula, the derivative is, for example, in this specification,

[0050]

(Equation 3) And so on.

[0051]

(Equation 4) c0 (zero is a subscript) is a propagation speed. Cauchy-initial-value-problem (Cauchy-pro for short)
blem), a general solution of the pressure propagation behavior when the initial pressure distribution p (r, 0) and the initial pressure distribution change p ′ (r, 0) are assumed by the following equation is obtained.

[0052]

(Equation 5) The partial differential equation is converted to an ordinary differential equation by applying the Hankel transform to the wave equation (1). The Hankel transform for the spatial coordinates r of the pressure field p (x, t) is expressed by the following equation.

[0053]

(Equation 6) Superscripts and subscripts after the integration symbol indicate the integration range in this specification. When this is applied to the Laplace operator (two-dimensional Laplacian appearing on the left side of Expression (1)) in the cylindrical coordinate system, it can be converted into the following very simple expression.

[0054]

(Equation 7) When this is applied to the cylindrical wave equation (1), the partial differential equation is converted into the following ordinary differential equation.

[0055]

(Equation 8) Equation (5) has the following simple solution.

[0056]

(Equation 9) The Hankel transform of Expression (2), which is the initial condition, is represented by the following expression.

[0057]

(Equation 10) When these are substituted into the general solution equation (6), the undetermined constants A and B
The special answer is as follows.

[0058]

[Equation 11] When this is inversely transformed by Hankel, a general solution in the real space is obtained, and the following equation is obtained.

[0059]

(Equation 12) Next, the pressure propagation behavior when the circular initial compression field acts, that is, the circular initial compression field is integrated at time t (= 0) into a circular area of radius a as shown in the following equation (11). Then, the pressure wave propagation behavior at the time t (> 0) when a uniform pressure distribution acting as 1.0 is applied will be examined.

[0060]

(Equation 13) If this is Hankel transformed,

[0061]

[Equation 14] F * of the first term on the right side of equation (9), which is a general solution of equation (11)
Substituting into (ξ) gives the following equation.

[0062]

(Equation 15) This corresponds to the 0th-order Hankel inverse transformation of the function J1 (aξ) cos (c0ξt) / ξ, but since this integration is not easy, here, equation (11) is simplified to investigate the basic properties of wave propagation. Become That is, in the limit of a → 0 in Equation (11) using the property of the first-order Bessel function J1 (z), J1 (az) is limited to a region near 0, so that the gradient 1/2 is approximately It can be approximated to a straight line. This means that the initial pressure distribution function p
(R, 0) is a delta function δ (r) (a delta function δ
(R) is equivalent to δ (r = 0) = ∞, δ (a non-zero area in the vicinity of r = 0) = 0, and a function having a property of being 1 when integrated over the entire area) Means

[0063]

(Equation 16) Therefore, equation (11) is a simple constant.

[0064]

[Equation 17] The inverse Hankel transform of equation (12) is

(Equation 18) This is converted into the form in the formula of the inverse transformation, and is modified as in the following equation (15) in order to facilitate the inverse transformation.

[0065]

[Equation 19] This solution is easier to find from the following Hankel inverse transformation formula:

[0066]

(Equation 20) Using the Hankel transform equation (16) in the equation (15),

(Equation 21) Applying the differentiation in this equation, the final solution is:

[0067]

(Equation 22) This equation has a singular point at r = 0 and ct = r, and becomes ∞.
This means that at time t = 0, the initial pressure distribution of the + δ function propagates outward as a pressure wave at t> 0,
In contrast, the backward wave converges toward the center of the pressure distribution. The time t0 at which the backward wave reaches the center is generally t0 = a / c0t (zero is a subscript). Here, since a → 0, t reaches the center near zero, that is, instantaneously.

Since the compression field reverses to the pulling field when the center is reached, in this case, at time t (= 0), the initial pressure distribution of the + δ function (+ ∞) is −δ at t (> 0). This waveform becomes a function (-∞), and this waveform has a speed c0t
And propagates outward. Since the waveform has an amplitude of -∞ at first, even if it propagates to the outside, the amplitude of -∞ is maintained at the front of the wave. FIG. 10 shows p (r, t) at time c0t = 1 in equation (18). As shown in the equation (18), the time t becomes -∞ instantaneously near zero, so that t> 0
, The -p pressure wave propagates. In general, FIG. 1 is a diagram conceptually showing a method of propagating a pressure wave in a case where the diameter of the pressure distribution has a width a and the pressure amplitude is finite.
0. The propagation behavior of such a pressure wave causes expansion and contraction of the object, and the velocity of the surface is measured by the Doppler effect.

[Brief description of the drawings]

FIG. 1 is a combined plan view showing a test piece to be detected by a method for detecting a stress wave in an element region according to the present invention.

FIG. 2 is an optical circuit diagram showing an embodiment of an apparatus for detecting a stress wave in an element region according to the present invention.

FIG. 3 is a front sectional view of a test piece in which the stress wave appears.

FIG. 4 is a graph showing a velocity spectrum of a test piece having a certain Young's modulus.

FIG. 5 is a graph showing a velocity spectrum of another test piece having a certain Young's modulus.

FIG. 6 is a graph showing a velocity spectrum of still another test piece having a certain Young's modulus.

FIG. 7 is a graph showing a relationship between neutron irradiation dose and material deterioration.

FIG. 8 is a front view showing another embodiment of the measurement object.

FIG. 9 is a side view of FIG. 8;

FIG. 10 is an oblique axis projection view showing a pressure wave transmission behavior.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 1st laser (for measurement) output device 2 ... 2nd laser (for heat input) output device 3 ... 1st incident laser 4 ... 1st optical waveguide 5 ... 2nd incident laser 6 ... 2nd optical waveguide 8 ... heat input area surface 10 ... disk 12 ... frequency analyzer 13 ... reflection surface 20 ... shell 23 ... proton beam Sn ... diffusion tip surface Vn ... velocity spectrum

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Ryutaro Hino, 2-4 Shirakata Shirane, Tokai-mura, Naka-gun, Ibaraki Pref. Japan Atomic Energy Research Institute (72) Koichi Akabane 1-23-11 Wakamatsucho, Fuchu-shi, Tokyo Japan Scientific Engineering Co., Ltd.

Claims (13)

[Claims] 1. A method according to claim 1, wherein a first element is located on a surface of a local element region of the solid object.
First irradiating means for irradiating a laser beam to supply thermal energy to the element region; and irradiating a second laser beam to the surface of the element region to detect a movement speed of the surface of the element region. Second for
A stress wave detecting device for an element region, comprising: an irradiation unit; and a Doppler interferometer for receiving the second laser beam reflected from the surface of the element region and detecting the motion velocity by the Doppler effect. 2. The method according to claim 1, wherein the solid object is approximated as a two-dimensional object.
When the distance from the center point of the element area is represented by r, the following equation is obtained. A stress wave detection device for an element region, wherein the motion velocity caused by a singular point of a pressure distribution p (r, t) represented by: 3. The solid-state object according to claim 1, wherein the propagation speed of the stress wave is faster than the conduction speed of the thermal energy in the solid-state object, and the Young's modulus of the solid-state object is obtained from a spectrum of the speed at the time. An element region stress wave detecting device, characterized in that: 4. The stress wave detecting apparatus according to claim 3, wherein the movement speed is detected as a spectrum with respect to time. 5. The stress wave detecting device according to claim 1, wherein the first laser beam and the second laser beam are the same. 6. An apparatus according to claim 1, further comprising control means for controlling an irradiation time of said second laser beam. 7. The solid-state imaging device according to claim 1, further comprising control means for controlling an irradiation time length of the second laser beam, wherein a speed of propagation of the stress wave is larger than a speed of conduction of the thermal energy. At a reflection point where a stress wave generated by the irradiation is reflected in a reflection surface having a boundary condition of reflection formed in the solid-state object and reflected by the Doppler interferometer. Wherein the thermal energy is not transmitted to the reflection surface, and the irradiation time is shorter than a time length from the irradiation start time to the reflection time. 8. The stress wave detecting device according to claim 7, wherein the boundary condition is a distance from a boundary surface of a layer formed in the solid object to the surface. 9. The optical system according to claim 1, wherein the first laser beam is guided between the Doppler interferometer and the surface by a first optical waveguide, and the second laser beam is guided to a position before the surface by a second optical waveguide. A stress wave detecting device for an element region, which is guided by a wave tube. 10. A longitudinal stress wave propagating perpendicularly from the local region surface to the local region surface by irradiating a first laser to the local region surface of the solid object, and extending along the local region surface from the local region surface. Generating a transverse stress wave in the solid object that spreads two-dimensionally in the solid object, irradiating a second laser to the local region surface where the stress wave is reflected back in the solid object and Detecting the value of the second laser due to the Doppler effect. When the distance from the center of the element region is represented by r, the value of the Doppler effect is substantially the following equation. A method for detecting a stress wave in an element region, which is caused by the existence of a singular point of a pressure distribution p (r, t) represented by: 11. The method according to claim 10, wherein the second laser beam is instantaneously irradiated while the first laser beam is continuously irradiated. 12. The method according to claim 10, wherein the elastic modulus of the solid object is calculated from the value by calculation. 13. The method according to claim 10, wherein the duration of the instantaneous irradiation is variable.