JP2014232041A - Laser speckle strain measurement apparatus and laser speckle strain measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure strain of a measuring object even under a severe environment and a severe condition.SOLUTION: A laser speckle strain measurement apparatus for measuring strain of a measuring object comprises: an image acquisition unit for acquiring a speckle image of the measuring object; and an input-output device for controlling the operation of the image acquisition unit and processing the speckle image. The laser speckle strain measurement apparatus acquires a speckle image at a preset time interval by the image acquisition unit, compares the acquired speckle image with an immediately preceding speckle image to thereby calculate a traveling amount of the speckle included in the speckle image, and further calculates strain of the measuring object on the basis of the calculated traveling amount of the speckle.

Description

  The present invention relates to a laser speckle strain measuring apparatus and a laser speckle strain measuring method.

  There is a laser speckle strain measuring device as a device for measuring strain (strain) of an object to be measured. The laser speckle distortion measurement apparatus irradiates a measurement target with laser light and acquires an image (speckle image) including speckles that are striped patterns caused by interference of laser light diffused by the measurement target. When displacement, rotation, deformation (strain, shear strain) or the like occurs in the measurement object, the shape of the speckle image included in the speckle image changes because the shape of the surface changes. The laser speckle distortion measurement device acquires a speckle image and measures a change in speckle, thereby measuring the distortion of the measurement object (see Patent Document 1). Laser speckle strain measurement equipment can measure non-contact, and the gauge length, which is the area used for measurement, is short (about φ1mm), so it is possible to measure strain in areas where it is difficult to attach high-temperature parts or strain gauges. It becomes.

  In Patent Document 1, a laser beam having different wavelengths is irradiated from two directions onto the surface of an object (the surface of an object to be measured), and the reflected light (diffused light) of the laser is separated by a beam splitter on the surface of the object. Thus, there is described a laser speckle distortion measuring apparatus that acquires speckle images for light of each wavelength and measures a change in distortion based on a difference in the amount of speckle movement of each speckle image.

JP-A-62-150110

  The laser speckle strain measuring apparatus described in Patent Document 1 can measure a strain that changes at a high speed, such as vibration strain, by allowing laser beams having different wavelengths to enter from two directions, and has a wider application range. can do.

  Here, as a measurement of the distortion of the measurement object, the distortion of the measurement object may be measured for a long period. That is, it may be required to monitor the distortion of the measurement object for a long period of time. However, when applied to long-time monitoring, measurement accuracy may not be maintained.

  The present invention has been made in view of the above, and provides a laser speckle strain measuring apparatus and a laser speckle strain measuring method capable of measuring strain of an object to be measured even in more severe environments and severe conditions. With the goal.

  In order to solve the above-described problems and achieve the object, the present invention is a laser speckle distortion measurement device that measures distortion of a measurement object, and an image acquisition unit that acquires a speckle image of the measurement object; An input / output device that controls an operation of the image acquisition unit and processes a speckle image, and the input / output device acquires a speckle image at a set time interval by the image acquisition unit, The acquired speckle image is compared with at least the immediately preceding speckle image to calculate the movement amount of the speckle included in the speckle image, and based on the calculated movement amount of the speckle, the distortion of the measurement object is calculated. Is calculated.

  Moreover, it is preferable that the said measurement object further has an antioxidant film | membrane formed in the surface by which the said image acquisition part image | photographs a speckle image.

  The antioxidant film is preferably formed of a material that maintains an antioxidant function at 650 ° C. and can be formed on the surface of the measurement object at room temperature.

  In the set time interval, the correlation coefficient between the acquired speckle image and at least the immediately preceding speckle image is preferably 0.8 or more.

  The set time interval is preferably within 10 seconds.

  Further, the input / output device preferably averages the calculated movement amount of the speckle using the calculated movement amount, and sets the averaged movement amount of the speckle as the calculated movement amount of the speckle. .

  Moreover, it is preferable that the input / output device averages the movement amount of speckles at an average of three points.

  The image acquisition unit outputs a first laser output unit that outputs a laser beam having a first wavelength toward the measurement object, and a first laser unit that outputs a laser beam having a second wavelength toward the measurement object. A second laser output unit; a first laser receiving unit that receives light having a first wavelength among the light diffused by the measurement object; and a light having a second wavelength among light diffused by the measurement object. A second laser light receiving unit that receives light, an image of the measurement object having the first wavelength acquired by the first laser light reception unit, and the measurement object having the second wavelength acquired by the second laser light reception unit. And a processing unit that acquires a speckle image of the measurement object.

  The image acquisition unit further includes a half mirror that splits the light diffused by the measurement object, and the first laser light receiving unit is diffused by the light transmitted through the half mirror and the half mirror. It is preferable that one of the light is received, and the second laser receiving unit receives the other of the light transmitted through the half mirror and the light diffused by the half mirror.

  In order to solve the above-described problems and achieve the object, the present invention is a laser speckle strain measurement method for measuring strain of a measurement object, the step of acquiring a speckle image at a set time interval, Comparing the acquired speckle image with at least the immediately preceding speckle image to calculate a movement amount of the speckle included in the speckle image, and based on the calculated movement amount of the speckle, the measurement object And a step of calculating the distortion.

  A laser speckle distortion measuring apparatus and a laser speckle distortion measuring method according to the present invention acquire a speckle image at a set time interval and compare the acquired speckle image with at least the immediately preceding speckle image. By calculating the amount of speckle movement included in the image and calculating the distortion of the measurement object based on the calculated amount of speckle movement, changes in speckle other than distortion that occur in harsh environments and harsh conditions The influence of surface oxidation or the like, which is a factor, can be reduced or eliminated easily and inexpensively. Thereby, there exists an effect that distortion of a measuring object can be measured also in a severer environment and severe conditions.

FIG. 1 is a schematic diagram showing a configuration of a laser speckle distortion measuring apparatus according to the present embodiment. FIG. 2 is a block diagram showing a schematic configuration of an input / output device of the laser speckle distortion measuring apparatus. FIG. 3 is a flowchart showing the operation of the laser speckle distortion measuring apparatus. FIG. 4 is an explanatory diagram illustrating an example of the acquired speckle image. FIG. 5 is an explanatory diagram showing an example of the acquired speckle image. FIG. 6 is a graph showing an example of the relationship between time and strain measured by the laser speckle strain measurement apparatus. FIG. 7 is a graph showing an example of the relationship between the time measured by the laser speckle distortion measuring apparatus and the correlation coefficient. FIG. 8 is a flowchart illustrating an example of a correlation coefficient calculation method. FIG. 9 is an explanatory diagram for explaining an example of a correlation coefficient calculation method. FIG. 10 is a graph showing an example of the relationship between the temperature of the measurement object and the oxide scale growth rate. FIG. 11 is a block diagram showing a configuration of a laser speckle distortion measuring apparatus according to another embodiment. FIG. 12 is an explanatory diagram illustrating an example of the acquired speckle image. FIG. 13 is an explanatory diagram showing an example of the acquired speckle image. FIG. 14 is a graph showing an example of the relationship between time and strain measured by the laser speckle strain measurement apparatus. FIG. 15 is a graph showing an example of the relationship between the time measured by the laser speckle distortion measuring apparatus and the correlation coefficient. FIG. 16 is a graph showing an example of the relationship between time and strain measured by the laser speckle strain measurement apparatus. FIG. 17 is a graph showing an example of the relationship between the time measured by the laser speckle distortion measuring apparatus and the correlation coefficient. FIG. 18 is an explanatory diagram for explaining another example of the arithmetic processing of the laser speckle distortion measuring apparatus.

  Embodiments of a laser speckle strain measuring apparatus and a laser speckle strain measuring method according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In addition, the constituent elements in this embodiment include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in a so-called equivalent range. Here, the laser speckle strain measuring apparatus and the laser speckle strain measuring method of the present embodiment can use various members that generate strain as measurement objects.

  First, the configuration of the laser speckle distortion measuring apparatus according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram showing a configuration of a laser speckle distortion measuring apparatus according to the present embodiment. FIG. 2 is a block diagram showing a schematic configuration of an input / output device of the laser speckle distortion measuring apparatus. The laser speckle distortion measurement apparatus 10 measures the distortion at the measurement target position of the measurement target 8. The laser speckle distortion measurement apparatus 10 controls the operation of an image acquisition unit (speckle image acquisition unit) 11 that acquires a speckle image of a measurement region of the measurement object 8 and the image acquisition unit 11 and acquires an image. The input / output device 28 that calculates the distortion by processing the speckle image acquired by the unit 11 and the holding unit 30 that holds the measurement object 8 are included.

  The measurement object 8 is a member to be measured for strain. The measuring object 8 shown in FIG. 1 is a rod-shaped test piece and is held by a holding unit 30 described later. The measurement object 8 has an antioxidant film 70 formed at least in a region where strain is measured. The antioxidant film 70 is a film having a function of preventing the measurement object 8 from being oxidized, that is, preventing the alteration of the region in which the strain of the measurement object 8 is measured. The antioxidant film 70 is formed by applying or attaching an antioxidant to the surface of the measurement object 8. It is preferable that the antioxidant has stable antioxidant performance even at a high temperature (for example, 650 ° C.) and can be dried at room temperature (that is, firing is not necessary). The antioxidant is preferably a material that can be easily applied, specifically, a material that can be applied to the measurement object 8 by spraying or brushing. Moreover, it is preferable that the antioxidant follows the displacement of the measurement object 8 after being formed as the antioxidant film 70 on the surface of the measurement object 8. That is, it is preferable that the antioxidant film 70 has a function of deforming together with the measurement object 8. As the antioxidant, for example, SCW-4 can be used. The antioxidant film 70 can be easily formed on the measurement object 8 by being formed of an antioxidant having the above performance. Moreover, the antioxidant film | membrane 70 can suppress deterioration, such as oxidation of the measuring object 8, by forming with the antioxidant provided with the said performance. Here, in the present embodiment, the measurement object 8 is a test piece, but is not limited thereto. The measuring object 8 may have a shape in which the region where strain is measured is exposed. For example, a measurement object 8 can be a pipe, a housing, or the like.

  The holding unit 30 is a mechanism that holds the measurement object 8, and includes a holding unit 32, a heating unit 34, and a thermometer 36. The holding unit 32 is a holding mechanism that fixes the measurement object 8 at a predetermined position. The holding unit 32 sandwiches and holds the end of the measurement object 8 (in the present embodiment, the upper side in the vertical direction). The heating unit 34 heats the measurement object 8. The heating unit 34 is preferably a mechanism that heats the measurement object 8 in a non-contact manner, for example, a heater. The thermometer 36 measures the temperature of the measurement object 8. The thermometer 36 sends the measurement result to the input / output device 28. The holding unit 30 uses the measurement result of the thermometer 36 to control the operation of the heating unit 34 by an input / output device 28 described later, and maintains the measurement object 8 at a predetermined temperature. The holding unit 30 may apply predetermined stress (tensile stress, compressive stress) to the measurement object 8 depending on measurement conditions. In this case, the holding unit 30 applies stress by relatively moving the holding unit 32 while holding the both ends of the measurement object 8 by the holding unit 32. In the laser speckle strain measurement apparatus 10 of the present embodiment, since the measurement object 8 is a test piece, the holding unit 30 is provided. However, when the measurement object 8 is a part of various apparatuses, the holding unit 30 is provided. There is no need to provide.

  The image acquisition unit 11 is a mechanism for acquiring a speckle image of the measurement region of the measurement object 8, and includes a first laser output unit 12, a second laser output unit 14, a half mirror 16, and a first filter 18. The first laser light receiving unit 20, the second filter 22, the second laser light receiving unit 24, and the processing unit 26 are included.

  The first laser output unit 12 is a light source that outputs laser light having a first wavelength. The first laser output unit 12 irradiates the measurement region of the measurement object 8 with laser light having a first wavelength (hereinafter referred to as “first laser light”). The first laser output unit 12 causes the first laser light to be incident on the measurement region of the measurement object 8 in the direction in which the incident angle with respect to the measurement region of the measurement object 8 is θ. The second laser output unit 14 is a light source that outputs laser light having a second wavelength different from the first wavelength. The second laser output unit 14 irradiates the measurement region of the measurement object 8 with laser light having a second wavelength (hereinafter referred to as “second laser light”). The second laser output unit 14 has an orientation in which the incident angle of the measurement object 8 with respect to the measurement region is −θ, that is, an axis orthogonal to the measurement region of the measurement object 8 and is opposite to the first laser beam. The second laser beam is incident on the measurement region of the measurement object 8 in a direction inclined by θ. Therefore, the first laser beam and the second laser beam are respectively incident on the measurement region of the measurement object 8 from a symmetrical angle with respect to an axis orthogonal to the measurement region of the measurement object 8.

  The half mirror 16 is disposed on an axis orthogonal to the measurement region of the measurement object 8. The half mirror 16 receives part of the diffused light of the first laser light and the second laser light incident on the measurement region of the measurement object 8. The half mirror 16 transmits a part of the incident diffused light and reflects a part thereof.

  The first filter 18 is disposed on the optical path of the diffused light reflected by the half mirror 16. The first filter 18 is a filter that selectively transmits light having the first wavelength. For example, the first filter 18 has a light transmittance of the first wavelength equal to or higher than a predetermined ratio (for example, 90%), and at least a light transmittance of the second wavelength is equal to or lower than the predetermined ratio (for example, 5%). It is. Thereby, the 1st filter 18 permeate | transmits the light of 1st wavelength among the diffused lights reflected by the half mirror 16, and interrupts | blocks the light of 2nd wavelength. The first laser light receiving unit 20 is disposed on the downstream side of the first filter 18 on the optical path of the diffused light reflected by the half mirror 16. The first laser light receiving unit 20 is an image sensor in which light receiving elements (CMOS, CCD) are two-dimensionally arranged. By receiving the diffused light transmitted through the first filter 18, the light of the first wavelength diffused in the measurement region of the measurement object 8 is received. The first laser light receiving unit 20 converts the received light signal into an image signal and sends the image signal to the processing unit 26.

  The second filter 22 is disposed on the optical path of the diffused light that has passed through the half mirror 16. The second filter 22 is a filter that selectively transmits light of the second wavelength. For example, the second filter 22 has a second wavelength light transmittance of a predetermined ratio (for example, 90%) or more, and at least a first wavelength light transmittance of a predetermined ratio (for example, 5%) or less. It is. Thereby, the 2nd filter 22 permeate | transmits the light of 2nd wavelength among the diffused light which permeate | transmitted the half mirror 16, and interrupts | blocks the light of 1st wavelength. The second laser light receiving unit 24 is disposed on the downstream side of the second filter 22 on the optical path of the diffused light transmitted through the half mirror 16. The second laser light receiving unit 24 is an image sensor in which light receiving elements (CMOS, CCD) are two-dimensionally arranged. By receiving the diffused light transmitted through the second filter 22, the light of the second wavelength diffused in the measurement region of the measurement object 8 is received. The second laser light receiving unit 24 converts the received light signal into an image signal and sends the image signal to the processing unit 26. The optical path length L from the measurement object 8 to the first laser light receiving unit 20 and the optical path length La from the measurement object 8 to the second laser light receiving unit 24 are set to be equal to each other.

  The processing unit 26 processes the image signal sent from the first laser light receiving unit 20 to create a speckle image of light having the first wavelength in the measurement region of the measurement object 8, and from the second laser light receiving unit 24. The sent image signal is processed to create a speckle image of the second wavelength light in the measurement region of the measurement object 8.

  The first wavelength is, for example, a green wavelength, and the second wavelength is, for example, a red wavelength. The first wavelength and the second wavelength may be different from each other by a predetermined distance or more, and the wavelength is not particularly limited. Note that the first wavelength is a wavelength at which the transmittance of the second filter 22 is a predetermined ratio (for example, 5%) or less. The second wavelength is a wavelength at which the transmittance of the first filter 18 is a predetermined ratio (for example, 5%) or less.

  As described above, the image acquisition unit 11 irradiates the first laser beam and the second laser beam from the first laser output unit 12 and the second laser output unit 14 toward the measurement region of the measurement object 8, respectively. The image acquisition unit 11 has the first wavelength of the diffused light generated by irradiating the measurement region of the measurement object 8 with the first laser light and the second laser light and having passed through the half mirror 16 and the first filter 18. The first laser light receiving unit 20 receives the light, and the second laser light receiving unit 24 receives the second wavelength light that has passed through the half mirror 16 and the second filter 22. Further, the image acquisition unit 11 processes a signal generated based on the light received by the first laser light receiving unit 20 and the second laser light receiving unit 24 by the processing unit 26, thereby speckle images of the measurement regions at the respective wavelengths. That is, two speckle images can be acquired.

  The input / output device 28 controls the operation of the image acquisition unit 11 and processes the speckle image acquired by the image acquisition unit 11 to calculate distortion. The input / output device 28 includes an input unit 50, an output unit 52, a communication unit 54, a control unit 56, and a storage unit 58.

  The input unit 50 is a device such as a keyboard, mouse, touch panel, etc., on which a user or an operator inputs an operation. The output unit 52 is a device that outputs various information such as characters and graphics. The output unit 52 is a liquid crystal panel, an organic EL (Organic Electro-Luminescence) panel, a display device such as a projector, a printing device, or the like. The communication unit 54 controls transmission / reception of information to / from other devices based on a predetermined communication protocol. The communication unit 54 can be used as an input / output unit as well as the input unit 50 and the output unit 52.

  The control unit 56 includes a CPU (Central Processing Unit) that is a calculation unit and a memory that is a storage unit, and implements various functions by executing programs using these hardware resources. Specifically, the control unit 56 reads out a program stored in the storage unit 58 and expands it in the memory, and causes the CPU to execute instructions included in the program expanded in the memory. The control unit 56 reads / writes data from / to the memory and the storage unit 58 and controls the operation of the communication unit 54 and the like according to the execution result of the instruction by the CPU.

  The storage unit 58 includes a nonvolatile storage device such as a magnetic storage device or a semiconductor storage device, and stores various programs and data. The program stored in the storage unit 58 includes a laser speckle distortion measurement evaluation program. Note that some or all of the programs and data to be stored in the storage unit 58 in FIG. 2 are stored in another device with which the input / output device 28 can communicate via a network, and the input / output device as necessary. 28 may be downloaded. 2 may be stored in a storage medium and read by a medium reading unit as necessary. The program and data stored in the storage unit 58 in FIG.

  Next, the processing operation of the laser speckle strain measuring apparatus 10, specifically, the strain measuring operation, that is, the laser speckle strain measuring method will be described with reference to FIGS. FIG. 3 is a flowchart showing the operation of the laser speckle distortion measuring apparatus. 4 and 5 are explanatory diagrams illustrating examples of acquired speckle images. FIG. 6 is a graph showing an example of the relationship between time and strain measured by the laser speckle strain measurement apparatus. FIG. 7 is a graph showing an example of the relationship between the time measured by the laser speckle distortion measuring apparatus and the correlation coefficient. FIG. 8 is a flowchart illustrating an example of a correlation coefficient calculation method. FIG. 9 is an explanatory diagram for explaining an example of a correlation coefficient calculation method. FIG. 10 is a graph showing an example of the relationship between the temperature of the measurement object and the oxide scale growth rate.

  First, in the laser speckle distortion measuring apparatus 10, the measurement object 8 is attached to the holding unit. Thereafter, the laser speckle strain measurement apparatus 10 determines measurement conditions (step S12), and starts measurement, that is, strain measurement (step S14). Here, the measurement conditions are a temperature at the time of measurement, a predetermined time (measurement interval) described later, and the like. The measurement condition may be determined based on the condition input to the input unit 50, or may be determined based on the information acquired from the measurement object 8.

  The laser speckle distortion measuring apparatus 10 acquires a speckle image when measurement is started (step S16). When the laser speckle distortion measuring apparatus 10 starts measurement, the image acquisition unit 11 acquires the first speckle image. Thereby, the laser speckle distortion measuring apparatus 10 acquires the speckle image of the 1st measurement object used as the reference | standard of determination.

  When the speckle image is acquired, the laser speckle distortion measuring apparatus 10 determines whether a predetermined time has elapsed (step S18). Specifically, it is determined whether the elapsed time after acquiring the speckle image is equal to or longer than a threshold time. If the laser speckle distortion measurement apparatus 10 determines that the predetermined time has not elapsed (No in step S18), the laser speckle distortion measurement apparatus 10 returns to step S18. The laser speckle distortion measurement apparatus 10 repeats the determination in step S18 until a predetermined time has elapsed.

  If the laser speckle distortion measurement apparatus 10 determines that the predetermined time has elapsed (Yes in step S18), the image acquisition unit 11 acquires a speckle image (step S20). The laser speckle distortion measuring apparatus 10 can acquire a speckle image after a predetermined time has elapsed after acquiring the speckle image. After acquiring the speckle image, the laser speckle distortion measurement device 10 compares the latest speckle image with the speckle image, calculates the speckle movement amount (step S22), and stores the calculation result (step S24). The laser speckle distortion measurement device 10 compares the acquired speckle image with the latest speckle image, identifies a similar position, and determines the amount of movement of the identified similar position between the two images. , The speckle movement amount. The laser speckle distortion measuring apparatus 10 stores the calculated speckle movement amount in the storage unit 58.

  After storing the calculation result, the laser speckle distortion measurement apparatus 10 calculates the distortion based on the calculation result (step S26). The laser speckle distortion measuring apparatus 10 integrates the calculated speckle movement amount and calculates the integrated value as distortion. Note that the method of calculating the distortion based on the speckle movement amount is not limited to simple integration, and correction processing may be performed.

  After calculating the strain based on the calculation result, the laser speckle strain measuring apparatus 10 determines whether the measurement is finished (step S28). If the laser speckle distortion measuring apparatus 10 determines that the measurement is not finished (No in step S28), the process returns to step S18. The laser speckle distortion measurement device 10 acquires a speckle image, calculates a speckle movement amount, and calculates a distortion based on the speckle movement amount until the measurement is completed, that is, until a set measurement time elapses. Repeat the process. If the laser speckle distortion measuring apparatus 10 determines that the measurement has been completed (Yes in step S28), the process ends.

  As shown in FIG. 3, the laser speckle distortion measuring apparatus 10 acquires a speckle image every time a predetermined time elapses, that is, acquires a speckle image at a predetermined time interval. For example, the laser speckle distortion measuring apparatus 10 can acquire a plurality of speckle images at regular time intervals as shown in FIG. 4 by acquiring a speckle image every 5 minutes. The speckle image shown in FIG. 4 includes a speckle image acquired during 5 to 30 minutes and a speckle image acquired during 40 hours and 5 minutes to 40 hours and 30 minutes during 40 hours and 30 minutes. And an image. The laser speckle distortion measuring apparatus 10 can acquire a plurality of speckle images at regular time intervals as shown in FIG. 5, for example, by acquiring a speckle image every 10 seconds. The speckle image shown in FIG. 5 was measured for 40 hours and 1 minute, and was acquired between 10 seconds and 60 seconds, and between 40 hours and 10 seconds and 40 hours and 1 minute. A speckle image is shown. 4 and 5, the object 8 to be measured is formed of a chromium molybdenum steel pipe, specifically, STBA24 (a standard steel alloy pipe for boiler heat exchanger (JIS G 3462)), and an antioxidant film is formed on the surface. 70 was formed with SCW-4. Moreover, it measured by making the temperature of the measuring object 8 into 650 degreeC.

  When measuring strain in a fatigue test, a thermal cycle test, or the like, the laser speckle strain measurement apparatus 10 preferably shortens a time interval (sampling interval) for acquiring a speckle image, for example, within 10 s (seconds). . When the laser speckle strain measurement apparatus 10 measures strain in a long-time creep test, it is preferable that the time interval (sampling interval) for acquiring a speckle image is increased to, for example, 5 min (minutes).

  The laser speckle distortion measuring apparatus 10 compares the speckle image with the most recently acquired speckle image, that is, the speckle image acquired before a predetermined time interval, and performs processing for calculating the speckle movement amount. It is performed every time, and the calculated plurality of speckle movement amounts are integrated to calculate the distortion.

  The laser speckle distortion measuring apparatus 10 acquires speckle images at predetermined time intervals, calculates the speckle movement amount compared with the speckle image acquired immediately before, and calculates distortion based on the speckle movement amount. By calculating, even if the measurement region of the measurement object 8 has deteriorated between the start of measurement and the end of measurement, it is possible to specify the change in the relative relationship of each position and perform measurement with high accuracy. . That is, the laser speckle strain measuring apparatus 10 can easily and inexpensively reduce or eliminate the influence of surface oxidation or the like, which is a cause of speckle changes other than strain occurring under severe conditions and severe conditions. Thereby, there exists an effect that distortion of a measuring object can be measured also in a severer environment and severe conditions. Since the laser speckle distortion measuring apparatus 10 can increase measurement accuracy by arithmetic processing, it is possible to easily and inexpensively reduce or eliminate the influence of surface oxidation or the like.

  Further, the laser speckle strain measuring apparatus 10 can suppress the alteration of the measurement region, particularly oxidation, by providing the antioxidant film 70 in the measurement region of the measurement object 8. Thereby, it becomes easy to compare speckles of speckle images, and the accuracy of measurement can be further increased.

  Specifically, when the laser speckle distortion measuring apparatus 10 acquires a speckle image every 5 minutes as shown in FIG. 4 and calculates the distortion based on the acquired result, as shown in FIG. The time change of strain could be measured. In FIG. 6, the horizontal axis represents time (h) and the vertical axis represents strain (strain% ε). As shown in FIG. 6, it can be seen that no strain is measured after 10 hours. Since the measurement shown in FIG. 6 is held in a state where no stress is applied, distortion does not occur, and measurement can be performed with high accuracy.

  FIG. 7 shows the correlation coefficient when the distortion is measured in FIG. In FIG. 7, the horizontal axis represents time (h), and the vertical axis represents the correlation coefficient. The correlation coefficient is an index indicating the correlation between two images to be compared when calculating the speckle movement amount. The closer to 1, the higher the correlation, that is, the corresponding region has a similar shape. . As the correlation coefficient is higher, that is, closer to 1, the corresponding positions of the two images can be compared with higher accuracy, so that the speckle movement amount and distortion can be measured with higher accuracy. In the present embodiment, as shown in FIG. 7, a state where the correlation coefficient is high, specifically, a state where the correlation coefficient is 0.8 or more is maintained. Therefore, it can be seen that the measurement shown in FIG. 6 has high accuracy.

  Here, an example of the speckle movement amount and the correlation coefficient calculation method will be described with reference to FIGS. 8 and 9. The process shown in FIG. 8 may be performed by the laser speckle distortion measuring apparatus 10 or may be performed by capturing and analyzing a speckle image. The following description will be made assuming that the laser speckle distortion measurement apparatus 10 is used.

  The laser speckle distortion measurement apparatus 10 specifies a search range in the XY coordinates, which is a condition for the iterative process performed by the Do Loop statement (step S40). That is, the laser speckle distortion measuring apparatus 10 sets conditions for comparing two speckle images.

  Next, the laser speckle distortion measuring apparatus 10 determines the movement amount I in the X direction and the movement amount J in the Y direction, and determines the correlation permutation ranges VV1 (X, Y) and VV2 (X, Y) ( Step S42). The range VV1 (X, Y) is a range of the latest speckle image as shown in FIG. 9, and the range VV2 (X, Y) is a speckle image (the latest speckle image of the latest speckle image is shown in FIG. Next, the range of the acquired speckle image). VV1 (X, Y) and VV2 (X, Y) are in the same size range.

  Next, the laser speckle distortion measuring apparatus 10 compares the determined range VV1 (X, Y) and range VV2 (X, Y), and calculates the correlation coefficient r based on the comparison result (step S44). Specifically, the pixels at the same position in the range VV1 (X, Y) and the range VV2 (X, Y) shown in FIG. 9 are compared using the following formula to calculate the correlation coefficient r.

  After calculating the correlation coefficient r, the laser speckle distortion measuring apparatus 10 determines whether the search range calculation is finished (step S46). If the laser speckle distortion measurement apparatus 10 determines that the correlation function r has been calculated for the entire search range set in step S40, it determines that the search range calculation is complete. If the laser speckle distortion measurement apparatus 10 determines that the calculation of the search range has not ended (No in step S46), the process returns to step S42, changes the movement amount I and the movement amount J, and step S42, step S42. The process of S44 is performed.

  If the laser speckle distortion measurement device 10 determines that the calculation of the search range has been completed (Yes in step S46), it outputs the movement amount I, the movement amount J, and the correlation function r between the two target speckle images. (Step S48), and this process is terminated. The laser speckle distortion measurement device 10 is the closest to one of the correlation coefficients r calculated by repeated calculation, that is, the correlation coefficient r under the condition of the maximum value between the two target speckle images corresponding to each other. Let it be a correlation function r. Further, the laser speckle distortion measuring apparatus 10 calculates the speckle movement amount based on the movement amount I and the movement amount J under this condition.

  The laser speckle distortion measuring apparatus 10 can calculate the speckle movement amount with high accuracy by calculating the correlation coefficient r and the speckle movement amounts I and J in the process shown in FIG. Distortion can be calculated with high accuracy.

  Here, it is preferable that the laser speckle distortion measuring apparatus 10 acquires a speckle image at a time interval in which a correlation coefficient between the acquired speckle image and at least the immediately preceding speckle image is 0.8 or more. . That is, it is preferable to set the time interval for acquiring the speckle image as a condition that the correlation coefficient is 0.8 or more. The laser speckle distortion measuring apparatus 10 more preferably acquires the speckle image at a time interval at which the correlation coefficient between the acquired speckle image and at least the immediately preceding speckle image is 0.9 or more. . The laser speckle distortion measurement apparatus 10 measures speckle movement with high accuracy by comparing speckle images under a condition that the correlation function is 0.8 or more, more preferably 0.9 or more. Can do.

  Here, in the case where the laser speckle strain measuring apparatus 10 is provided with the antioxidant film 70 on the measurement object, the time interval for acquiring the speckle image is preferably set to 5 minutes or less. As shown in FIGS. 6 and 7, by setting the time interval for acquiring the speckle image to 5 minutes or less, the correlation coefficient can be maintained high, and the speckle movement amount can be measured with high accuracy. it can.

  Moreover, it is preferable that the laser speckle distortion measuring apparatus 10 performs measurement while heating the measurement object by the heating unit 34. The laser speckle strain measurement apparatus 10 can perform an acceleration test by heating the measurement object with the heating unit 34 and performing measurement under a temperature condition higher than the actual use condition. For example, as shown in FIG. 10, an oxide scale can be grown at a rate of 100 times by heating and measuring a measurement object of STBA 24 used at 550 ° C. to 650 ° C. As a result, it is possible to measure the effect of 4000 hours, about half a year, of the actual machine in 40 hours of measurement. In the above-described embodiment, the case of STBA 24 has been described. However, the same applies to the case of the measurement object of other materials such as HCM2S and T91. For example, when the measurement object manufactured in T91 is used at 550 ° C., a test accelerated by 100 times can be performed by measuring at about 700 ° C.

  Next, a laser speckle distortion measuring apparatus according to another embodiment will be described with reference to FIGS. FIG. 11 is a block diagram showing a configuration of a laser speckle distortion measuring apparatus according to another embodiment. 12 and 13 are explanatory diagrams showing examples of acquired speckle images. FIG. 14 is a graph showing an example of the relationship between time and strain measured by the laser speckle strain measurement apparatus. FIG. 15 is a graph showing an example of the relationship between the time measured by the laser speckle distortion measuring apparatus and the correlation coefficient. FIG. 16 is a graph showing an example of the relationship between time and strain measured by the laser speckle strain measurement apparatus. FIG. 17 is a graph showing an example of the relationship between the time measured by the laser speckle distortion measuring apparatus and the correlation coefficient.

  The laser speckle strain measuring apparatus 10 of the above embodiment can suppress oxidation or the like of the surface of the measurement object 8 by forming the antioxidant film 70 in the measurement region of the measurement object 8, and can improve measurement accuracy. However, the present invention is not limited to this. In the laser speckle strain measuring apparatus 10a shown in FIG. 11, the antioxidant film 70 is not formed on the surface of the measuring object 8a. The laser speckle strain measurement apparatus 10a has the same configuration except that the antioxidant film 70 is not formed on the surface of the measurement object 8a, and thus the description of the apparatus configuration is omitted.

  Similarly to the laser speckle distortion measurement apparatus 10, the laser speckle distortion measurement apparatus 10a acquires speckle images at predetermined time intervals, and compares the speckle image acquired immediately before with the speckle movement amount to calculate the speckle movement amount. By calculating the distortion based on the speckle movement amount, even if the measurement region of the measurement object 8a has changed between the start of measurement and the end of measurement, it is possible to specify the change in the relative relationship between the positions. Can be measured with high accuracy. That is, the laser speckle strain measurement apparatus 10a can easily and inexpensively reduce or eliminate the influence of surface oxidation or the like that is a factor of speckle change other than strain generated under severe conditions and severe conditions. Thereby, there exists an effect that the distortion of the measuring object 8a can be measured even in more severe environments and severe conditions. Since the laser speckle strain measurement apparatus 10a can increase the measurement accuracy by arithmetic processing, it is possible to reduce and eliminate the influence of surface oxidation and the like easily and inexpensively.

  Here, also in the laser speckle distortion measurement apparatus 10a, the time interval at which the speckle image is acquired is the time interval at which the correlation coefficient between the acquired speckle image and at least the immediately preceding speckle image is 0.8 or more. It is preferable to set it to 0.9 or more. As an example, the laser speckle distortion measuring apparatus 10a preferably sets the time interval for acquiring the speckle image to within 10 seconds. The laser speckle strain measuring apparatus 10a sets the time interval for acquiring a speckle image to a time interval at which the correlation coefficient is 0.8 or more, for example, within 10 seconds, so that the antioxidant film 70 is formed on the surface. Even when the film is not formed, it is possible to suppress the measurement accuracy from being lowered due to the influence of the surface alteration, and it is possible to measure the strain with high accuracy.

  Hereinafter, it will be described with specific examples with reference to FIGS. The laser speckle distortion measuring apparatus 10a acquires a speckle image every time a predetermined time elapses, that is, acquires a speckle image at a predetermined time interval. The laser speckle distortion measurement apparatus 10a can acquire a plurality of speckle images at regular time intervals as shown in FIG. 12, for example, by acquiring a speckle image every 5 minutes. The speckle image shown in FIG. 12 includes a speckle image acquired during 5 to 30 minutes and a speckle image acquired during 40 hours and 5 minutes to 40 hours and 30 minutes during 40 hours and 30 minutes. And an image. For example, the laser speckle distortion measuring apparatus 10a can acquire a plurality of speckle images at regular time intervals as shown in FIG. 13 by acquiring a speckle image every 10 seconds. The speckle image shown in FIG. 13 was measured for 40 hours and 1 minute, and was acquired between 10 seconds and 60 seconds, and between 40 hours and 10 seconds and 40 hours and 1 minute. A speckle image is shown. 12 and 13, the measurement object 8a is formed of a chromium molybdenum steel pipe, specifically, STBA24 (a standard steel alloy pipe for boiler heat exchanger (JIS G 3462)). The measurement was performed with the temperature of the measurement object 8a set to 650 ° C.

  When the laser speckle distortion measuring apparatus 10a acquires a speckle image every 10 seconds as shown in FIG. 13 and calculates the distortion based on the acquired result, as shown in FIG. Was able to be measured. In FIG. 14, the horizontal axis represents time (h) and the vertical axis represents strain (strain% ε). As shown in FIG. 14, it can be seen that no strain is measured after 0.7 hours. Since the measurement shown in FIG. 14 is held in a state where no stress is applied, distortion does not occur, and measurement can be performed with high accuracy. In the image, it was confirmed that the speckle pattern changed when 0 hour passed and when 0.6 hour passed.

  Next, FIG. 15 shows a correlation coefficient when the distortion is measured in FIG. In FIG. 15, the horizontal axis represents time (h), and the vertical axis represents the correlation coefficient. As shown in FIG. 15, by acquiring a speckle image every 10 seconds, a state where the correlation coefficient is high, specifically, a state where the correlation coefficient is 0.8 or more is maintained. Therefore, it can be seen that the accuracy of measurement can be increased by acquiring speckle images every 10 seconds.

  On the other hand, when a speckle image is acquired every 5 minutes as shown in FIG. 12 and distortion is calculated based on the acquired result, the temporal change of distortion is measured as shown in FIG. I was able to. In FIG. 16, the horizontal axis represents time (h) and the vertical axis represents strain (strain% ε). As shown in FIG. 16, it can be seen that no strain is measured after 10 hours.

  FIG. 17 shows the correlation coefficient when the distortion is measured in FIG. In FIG. 17, the horizontal axis represents time (h) and the vertical axis represents the correlation coefficient. As shown in FIG. 17, it can be seen that when the speckle image is acquired every 5 minutes, the correlation coefficient is 0.4 or less. Therefore, it can be seen that, when the antioxidant film is not formed in the measurement region of the measurement object, the measurement accuracy decreases if the time interval for acquiring the speckle image is longer than 10 seconds. From the above, it can be seen that the laser speckle distortion measurement apparatus 10a can increase the measurement accuracy by acquiring a speckle image every 10 seconds.

  Moreover, in the said embodiment, although the speckle movement amount was calculated, the calculated speckle movement amount was integrated | accumulated, and distortion was calculated by the variation | change_quantity integration method which calculates distortion, This invention is not limited to this. The laser speckle distortion measurement device uses the calculated speckle movement amount, the most recent speckle movement amount, the most recently calculated strain, and various average values to calculate the speckle movement amount and the distortion The calculated value may be corrected. For example, the laser speckle distortion measuring device calculates the speckle movement amount by the average of three points using the three calculated values of the two most recent speckle movement amounts and the average value of the speckle movement amount. It may be calculated.

  Here, FIG. 18 is an explanatory diagram for explaining another example of the arithmetic processing of the laser speckle distortion measuring apparatus. FIG. 18 shows the relationship between the speckle movement amount and the integrated value calculated with the above-described distortion being zero, and the time. The integrated value is a value obtained by integrating relative values (speckle movement amounts calculated from the two most recent speckle images). As shown in FIG. 18, by calculating the speckle movement amount by averaging three points, it can be seen that a value closer to 0 than the relative value, that is, a value closer to the actual value can be calculated. Therefore, the laser speckle distortion measuring apparatus can reduce the accumulation of errors due to integration by performing a correction process on the speckle movement amount, and can increase the measurement accuracy.

  In addition, since the speckle image can be acquired with higher accuracy in the above-described embodiment, the speckle image is acquired by irradiating the measurement object with lasers having two different wavelengths in the image acquisition unit (speckle image acquisition unit). However, the present invention is not limited to this. The image acquisition unit can use various configurations for acquiring speckle images.

8, 8a Measurement object 10, 10a Laser speckle distortion measuring device 11 Image acquisition unit (speckle image acquisition unit)
DESCRIPTION OF SYMBOLS 12 1st laser output part 14 2nd laser output part 16 Half mirror 18 1st filter 20 1st laser light-receiving part 22 2nd filter 24 2nd laser light-receiving part 26 Processing part 28 Input / output device 30 Holding unit 32 Holding part 34 Heating Part 36 Thermometer
50 Input unit 52 Output unit 54 Communication unit 56 Control unit 58 Storage unit 70 Antioxidation film

Claims (10)

A laser speckle strain measurement device that measures strain of a measurement object,
An image acquisition unit for acquiring a speckle image of the measurement object;
An input / output device that controls the operation of the image acquisition unit and processes speckle images;
The input / output device acquires a speckle image at a set time interval by the image acquisition unit, compares the acquired speckle image with at least the immediately preceding speckle image, and includes the speckle image included in the speckle image. The laser speckle distortion measuring apparatus is characterized in that a distortion of the measurement object is calculated based on the calculated movement distance of the speckle.   The laser speckle strain measurement apparatus according to claim 1, wherein the measurement object further includes an antioxidant film formed on a surface on a side where the image acquisition unit captures a speckle image.   3. The laser speckle strain measurement according to claim 2, wherein the antioxidant film is formed of a material that maintains an antioxidant function at 650 ° C. and can be formed on a surface of the measurement object at room temperature. apparatus.   4. The set time interval according to claim 1, wherein a correlation coefficient between the acquired speckle image and at least the immediately preceding speckle image is 0.8 or more. 5. Laser speckle strain measurement device.   The laser speckle distortion measuring apparatus according to claim 4, wherein the set time interval is within 10 seconds.   The input / output device averages the calculated movement amount of the speckle using the calculated movement amount, and uses the averaged movement amount of the speckle as the calculated movement amount of the speckle. The laser speckle distortion measuring apparatus according to any one of claims 1 to 5.   The laser speckle distortion measuring apparatus according to claim 6, wherein the input / output device averages the amount of speckle movement by averaging three points. The image acquisition unit includes a first laser output unit that outputs laser light having a first wavelength toward the measurement target;
A second laser output unit for outputting laser light of a second wavelength toward the measurement object;
Of the light diffused by the measurement object, a first laser light receiving unit that receives light of the first wavelength;
Of the light diffused by the measurement object, a second laser light receiving unit that receives light of the second wavelength;
The measurement object image of the first wavelength acquired by the first laser light receiving unit and the image of the measurement object of the second wavelength acquired by the second laser light receiving unit are processed, and the measurement is performed. The laser speckle distortion measuring apparatus according to claim 1, further comprising: a processing unit that acquires a speckle image of an object. The image acquisition unit further includes a half mirror that separates light diffused by the measurement object,
The first laser light receiving unit receives one of the light transmitted through the half mirror and the light diffused by the half mirror,
9. The laser speckle distortion measuring apparatus according to claim 8, wherein the second laser light receiving unit receives the other of the light transmitted through the half mirror and the light diffused by the half mirror. A laser speckle strain measurement method for measuring strain of a measurement object,
Acquiring speckle images at set time intervals;
Comparing the acquired speckle image with at least the immediately preceding speckle image to calculate the movement amount of the speckle included in the speckle image;
Calculating the distortion of the measurement object based on the calculated movement amount of the speckle;
A laser speckle strain measuring method comprising:

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