JP4928930B2 - Ultrasonic flaw detection apparatus and ultrasonic flaw detection method - Google Patents

Description

  The present invention relates to an ultrasonic flaw detection apparatus and an ultrasonic flaw detection method suitable for ultrasonic flaw detection, in particular, ultrasonic flaw detection performed on stainless steel welds and the like.

  Conventionally, ultrasonic flaw detection is known as a method for nondestructively inspecting defects such as cracks generated inside a welded portion of metal. As such an ultrasonic flaw detection method, there is a phased array method. This is because a plurality of transducers arranged in a line or matrix are individually controlled, and the timing of oscillating each transducer is shifted to generate a composite wave of ultrasonic beams emitted from each transducer. A method of inspecting the presence or absence of defects such as cracks at the inspection target position, the size of the defect, etc. by receiving and analyzing the reflected wave or diffracted wave when the combined wave is applied to any inspection target position of the inspection target It is.

However, even if the inspection object is irradiated with the ultrasonic beam in this way, the traveling direction of the synthetic wave is bent due to the anisotropy of the particles of the inspection object, and the reflected wave from the inspection object position cannot be received. There is. In this case, the so-called S / N ratio becomes low and inspection becomes impossible.
Regarding such points, for example, the object to be inspected is irradiated with an ultrasonic beam in advance, and the time until the reflected wave returns is observed. When actually inspecting, the reflected wave returned is inverted. There is known a method for transmitting an ultrasonic signal so that an ultrasonic beam reaches an inspection target position (see, for example, JP-A-6-341978).
Japanese Patent Application Laid-Open No. 2005-148209 discloses that a plurality of artificial defects are formed at known positions on substantially the entire surface of a test piece made of the same material as the inspection object, and each artificial defect is superposed in advance. It is disclosed that a flaw detection inspection is performed on an inspection object by emitting a sound wave and making a database by associating a signal pattern obtained by inverting the reflected wave with the position of each artificial defect.
JP-A-6-341978 JP 2005-148209 A

However, in the inspection by the ultrasonic flaw detector of Patent Document 2, since the actual inspection object and the test piece are different, the ultrasonic beam is inspected even if the inspection is performed using the information stored in the database. There is a possibility that the target position cannot be reached, and there is a problem that the reflected wave cannot be received reliably.
Also, the delay time is not necessarily an appropriate time, and the error of the delay time due to the individual difference between the actual inspection object and the test piece is not taken into consideration.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an ultrasonic flaw detection apparatus and an ultrasonic flaw detection method that can improve the accuracy of ultrasonic flaw detection.

In order to solve the above problems, the present invention employs the following means.
The present invention includes a signal generator that generates an electrical signal for driving based on at least two delay patterns for focusing an ultrasonic beam on a predetermined inspection target position in an inspection target under different conditions; An ultrasonic beam corresponding to the electrical signal for driving is emitted into the inspection object, and the SN ratio of each reflected wave received by the probe is compared with the probe that receives the reflected wave, An adjustment unit that identifies the delay pattern when the highest reflected wave is obtained and generates a plurality of adjustment delay patterns by adjusting the delay pattern based on a predetermined condition; Each of the corresponding ultrasonic beams is irradiated into the inspection object and the reflected wave is received, and the reflected wave with the highest SN ratio is obtained among these reflected waves. To provide an ultrasonic flaw detector for analyzing defects.

  According to such a configuration, the reflected wave is received by irradiating the inspection target with an ultrasonic beam based on at least two delay patterns, and the delay pattern when the SN ratio of the received reflected wave is the highest is specified. Thus, the most suitable delay pattern can be extracted from the delay patterns. Further, a plurality of adjustment delay patterns are generated by finely adjusting the delay pattern, and an ultrasonic wave based on the adjustment delay pattern is irradiated to the inspection object to receive a reflected wave, and the highest of these reflected waves. The reflected wave from which the S / N ratio was obtained is specified. Thereby, the said delay pattern can be made into the pattern more suitable for a test subject. And since a defect is analyzed based on the electric signal at this time, the detection accuracy of the depth and position of the groove | channel of a defect can be improved.

  2. The adjustment unit according to claim 1, wherein the adjustment unit generates the plurality of adjustment delay patterns by handling the delay pattern as a spline curve passing through a plurality of control points and moving each control point according to a predetermined condition. Ultrasonic flaw detector.

  In this way, the delay pattern is handled as a spline curve f (x) passing through a plurality of control points, and a plurality of adjustment delay patterns are generated by moving each control point according to a predetermined condition. A delay pattern can be easily generated.

  The present invention generates a driving electric signal based on at least two delay patterns for focusing an ultrasonic beam on a predetermined inspection target position of an inspection target under different conditions, and each of the driving electric signals In response to the ultrasonic beam, the reflected wave is received, the S / N ratio of each reflected wave is compared, and the delay pattern from which the reflected wave with the highest S / N ratio is obtained is specified. And adjusting the identified delay pattern based on a predetermined condition to generate a plurality of adjustment delay patterns, irradiating the inspection object with an ultrasonic beam based on the adjustment delay pattern, and reflecting the reflected wave And an ultrasonic flaw detection method for analyzing a defect using a reflected wave having the highest S / N ratio among the received reflected waves.

  In the ultrasonic flaw detection method, the delay pattern may be handled as a spline curve passing through a plurality of control points, and the control delay points may be moved according to a predetermined condition to generate a plurality of the adjustment delay patterns. .

  According to the present invention, it is possible to improve the accuracy of ultrasonic flaw detection.

Hereinafter, an embodiment of an ultrasonic flaw detection apparatus and an ultrasonic flaw detection method according to the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of the ultrasonic flaw detector according to the present embodiment.
As shown in FIG. 1, the ultrasonic flaw detector 10 includes a probe 12 including a plurality of transducers 11 and a control unit 20 that controls the probe 12.
In the present embodiment, the vibrators 11 are arranged in a line along a predetermined direction. Each vibrator 11 is made of a piezoelectric element, and emits a vibration corresponding to an electric signal and an electric signal corresponding to the vibration received from the outside.

  The control unit 20 includes a signal generation unit 21 that generates an electrical signal for driving for vibrating each transducer 11 of the probe 12, and a reflected signal reception unit 22 that receives an electrical signal corresponding to the vibration detected by the probe 12. An analysis unit 23 that analyzes the received electrical signal, an adjustment unit 24 that adjusts a delay pattern used when generating the drive electrical signal, and a database (storage unit) 25 that stores a plurality of delay patterns. It has.

  In the database 25, for example, a delay pattern when it is assumed that the material of the inspection object is uniform and a delay pattern when it is assumed that the material of the inspection object is non-uniform are stored in advance. In addition, as for the delay pattern when it is assumed that the material is non-uniform, a plurality of delay patterns are stored according to the non-uniform level. As described above, the database 25 stores a plurality of delay patterns under different conditions.

These delay patterns are generated by the following method.
For example, a test piece that is uniform in material is created and a known artificial defect is formed in a predetermined location on the test piece. At this time, the size of the artificial defect to be formed is set such that the ultrasonic beam is reliably reflected by the artificial defect.

  Subsequently, the probe 12 is set at a predetermined position with respect to the test piece. Subsequently, the signal generation unit 21 generates an electric signal S1 such that an ultrasonic beam, which is a synthesized wave of ultrasonic waves emitted from each transducer 11, is focused on the position of the artificial defect, and this is generated by each transducer of the probe 12. 11 is given. Thereby, each vibrator 11 vibrates at a timing according to the waveform of the given electric signal S1, and emits an ultrasonic wave.

  At this time, an electric signal S1 having a waveform with a different timing (delay time) for generating vibration is given to each transducer 11 from the signal generation unit 21 so that the ultrasonic wave reaches the position of the artificial defect. Therefore, an ultrasonic beam that is a combined wave of ultrasonic waves emitted from each transducer 11 reaches a known artificial defect and is reflected, and this reflected wave returns toward the probe 12 and is received by each transducer 11. Will be. In the vibrator 11, an electric signal S <b> 2 corresponding to the vibration of the reflected wave is generated, and this electric signal S <b> 2 is received by the reflected signal receiving unit 22 of the control unit 20.

In the analysis unit 23, based on the received electrical signal S2, an electrical signal obtained by inverting (temporally reversing) the electrical signal S2 of the reflected wave corresponding to each of the transducers 11 (hereinafter referred to as “drive”). A combination of delay times of the vibrators 11 in the drive electric signal S3 is referred to as a “delay pattern”).
Here, since the reflected wave is received by each transducer 11 through the reflection path specific to the material of the test piece, the delay pattern has a waveform corresponding to the material and the formation position of the artificial defect. Become.
Then, a large number of artificial defects are formed over substantially the entire surface of the test piece, and by performing the same inspection on each artificial defect, a delay pattern for each artificial defect formation position is generated, and the artificial defect formation position And the delay pattern are stored in the database 25 in association with each other.

Similarly, by creating a plurality of test pieces with different uniform levels of materials and performing the same inspection on each test piece, a delay pattern corresponding to the formation position of each artificial defect for each test piece Are stored in the database 25 in association with each other.
As a result, in the database 25, the formation position of each artificial defect and the delay pattern are stored in association with each other for each uniform level (material) of the material.
In the present embodiment, for convenience of explanation, three levels are set as non-uniform levels of the material, and these are referred to as level 1, level 2, and level 3, respectively. Further, a material in which the above-described material is uniform is referred to as level 0.

Next, an ultrasonic flaw detection method during actual inspection will be described with reference to FIG.
First, a position where it is estimated that a defect has occurred in the inspection object is set as an inspection object position. Subsequently, the probe 12 is set at an appropriate position of the inspection object.

  Subsequently, a reference level is selected by the signal generator 21 (step SA1 in FIG. 2). In the present embodiment, level 0 is selected as the reference level. Subsequently, the signal generation unit 21 reads out from the database 25 a delay pattern for converging the ultrasonic beam to the inspection target position from among a plurality of delay patterns corresponding to the reference level 0, and this delay pattern is used as the delay pattern. A driving electrical signal S3 is generated and applied to each transducer 11 of the probe 12 (step SA2).

Thereby, as shown in FIG. 3, each transducer 11 emits an ultrasonic wave at a timing corresponding to each delay time, and the ultrasonic beam, which is a synthesized wave, is uniform in the material of the inspection object. Focusing at the inspection target position P1.
The focused ultrasonic beam is reflected according to the presence / absence of a defect at the inspection target position P 1, the situation, and the like, and this reflected wave is received by each transducer 11 of the probe 12. In each transducer 11, an electric signal Sr corresponding to the reflected wave is generated, and this electric signal Sr is given to the analyzing unit 23 via the reflected wave receiving unit 22 (step SA3).

Subsequently, a comparison level is selected by the signal generator 21 (step SA4). In the present embodiment, level 1 is selected as the comparison level. Subsequently, the signal generation unit 21 reads out from the database 25 a delay pattern for converging the ultrasonic beam to the inspection target position among the plurality of delay patterns corresponding to the level 1 that is the comparison level. A driving electrical signal S3 is generated and applied to each transducer 11 of the probe 12 (step SA5).
As a result, as shown in FIG. 4, the ultrasonic beam corresponding to the driving electrical signal S3 is focused at the inspection target position P2 when it is assumed that the material of the inspection target is non-uniform, as described above. Then, this reflected wave is received by each transducer 11 of the probe 12, and an electric signal Sc corresponding to this reflected wave is given to the analyzing unit 23 via the reflected wave receiving unit 22 (step SA6).

The analysis unit 23 determines whether or not the SN ratio of the electric signal Sc at the comparison level is larger than the SN ratio of the electric signal Sr at the reference level (step SA7). As a result, when the SN ratio at the comparison level is larger (“YES” in step SA7), a delay pattern of the comparison level is given to the adjustment unit 24.
The adjustment unit 24 generates a plurality of adjustment delay patterns by adjusting the delay pattern acquired from the analysis unit 23 according to a predetermined condition (step SA8).
The adjustment delay pattern is generated according to the following procedure.

First, as shown in FIG. 5, the delay pattern acquired from the analysis unit 23 is represented as a spline curve f (x) passing through a plurality of control points. In FIG. 5, the y-axis corresponds to the delay time, and the x-axis corresponds to the position of the transducer of the probe 12.
Here, the control point is a point defined when the delay pattern is represented as a spline curve, and is not related to the position of the vibrator 11. That is, each control point and each transducer 11 do not correspond one-on-one. Further, in the case of the probe 12 in which the eight vibrators 11 are arranged in one row as in the present embodiment, it is preferable that the maximum number of control points is six. This is because if there are many control points, the processing load related to the curve deformation processing increases.

Next, the adjustment unit 24 adjusts the delay pattern by moving the control point in the y-axis direction based on a predetermined condition.
Specifically, when the pattern of three consecutive control points C1 to C3 is a simple increase as shown in FIG. 6, the central control point C2 is moved by a predetermined amount within the following range.
y1 <y2 <y3 (1)
In the above equation (1), y1 is the y coordinate value of the control point C1, y2 is the y coordinate value of the control point C2, and y3 is the y coordinate value of the control point C3.
For example, as shown in FIG. 6, the predetermined amount is obtained by dividing the movable width W (= y3-y1) of the central control point C2 by a predetermined number (for example, an integer of 2 to 10). 1 division width. If the control points C1 to C3 are simply decreased, y1 and y3 may be interchanged in the above equation (1).

As shown in FIG. 7, when the central control point C2 has a maximum value among the three consecutive control points C1 to C3, the central control point C2 among the control points C1 and C3 at both ends. A control point having a value close to the y coordinate value is selected, and the central control point C2 is moved by a predetermined amount within the following range determined by the y coordinate value ys of the selected control point Cs.
y2- (y2-ys) <y2 <y2 + (y2-ys) (2)

  Note that the predetermined amount in this case is determined in the same manner as described above. Further, the case where the central control point C2 takes the minimum value can be handled in the same manner.

When the adjustment unit 24 creates a plurality of adjustment delay patterns by moving each control point by a predetermined amount in accordance with the various conditions as described above, the adjustment unit 24 gives these to the signal generation unit 21.
Based on the plurality of adjustment delay patterns provided from the adjustment unit 24, the signal generation unit 21 generates the corresponding drive electric signals S3 and sequentially supplies them to the transducer 11 of the probe 12 (FIG. 2). Step SA9).
As a result, as shown in FIG. 8, irradiation of an ultrasonic beam is performed based on each adjustment delay pattern created by the adjustment unit 24, and the electric signal of the reflected wave at this time is analyzed via the reflection signal receiving unit 22. Input to the unit 23 (step SA10).

  The analysis unit 23 identifies the electrical signal having the highest SN ratio from the SN ratios of the reflected wave electrical signals corresponding to the respective adjustment delay patterns, and performs analysis such as defect sizing using the identified electrical signals ( Step SA11).

  In step SA7 shown in FIG. 2, when the SN ratio of the electrical signal Sc at the comparison level is smaller than the SN ratio of the electrical signal Sr at the reference level (“NO” in step SA7), The process proceeds to step SA12, a different level, for example, level 2 is selected as the comparison level, the process returns to step SA5, and the above-described processing is executed.

As described above, according to the ultrasonic flaw detection apparatus and the ultrasonic flaw detection method according to the present embodiment, a delay pattern more suitable than the reference level is extracted from the delay patterns stored in the database 25, and By adjusting this delay pattern, an electric signal having the highest S / N ratio is acquired, so that a reflected wave reflecting the state of a defect generated inside the inspection object can be reliably received. As a result, the detection accuracy of the depth and position of the defect groove can be improved.
In the above-described embodiment, as a result of comparing the SN ratio of the electric signal Sc corresponding to the comparison level and the SN ratio of the electric signal Sr corresponding to the reference level, the comparison level indicates a higher SN ratio. However, instead of shifting to the adjustment of the delay pattern corresponding to this comparison level, the ultrasonic beam irradiation based on the delay pattern at each level 0 to 3 is performed, and as a result, the SN ratio is the highest. It is also possible to specify a delay pattern when an electric signal is obtained and adjust this delay pattern. By doing so, it is possible to extract an optimum delay pattern from among the delay patterns stored in the database 25.

  In the above embodiment, level 0 is selected as the reference level, but any of level 0 to level 3 may be selected. For example, the level estimated to be closest to the material of the inspection object may be selected as the reference level.

  In the above-described embodiment, the probe in which the vibrators are arranged in a line along a predetermined direction is used. However, the present invention is not limited to this, and the vibrators are arranged in a matrix (two-dimensional) as shown in FIG. Ultrasonic flaw detection may be performed using the probe 12 'on which 11 is arranged. In this case, the delay pattern is a three-dimensional representation as shown in FIG.

  Furthermore, as shown in FIG. 10, a TOFD (Time of Flight Diffraction Technique) method using different vibrators 11 for transmission and reception may be used. In this case, since the path of the ultrasonic beam from the transmitting probe 12a to the inspection target position is different from the path of the reflected wave from the inspection target position to the receiving probe 12b, the delay pattern of the receiving probe 12b is fixed. In this state, the delay pattern of the transmitting probe 12a is changed to obtain an optimal delay pattern, and then the delay pattern of the transmitting probe 12a is fixed to the optimal delay pattern. An optimum delay pattern is obtained by changing the delay pattern. The optimum delay pattern in this case is the same as described above.

  In the TOFD method, the transmission probe 12a can also be the reception probe 12b, and the reception probe 12b can be the transmission probe 12a. Therefore, as described above, the optimum delay pattern of the transmission probe 12a. Then, the optimum delay pattern of the reception probe 12b may be obtained by switching between the transmission probe 12a and the reception probe 12b and emitting an ultrasonic beam from the reception probe 12b.

  In the above-described embodiment, the adjustment delay pattern is obtained from the delay pattern in step SA8 in FIG. 2, but instead, a plurality of adjustment delay patterns are created in advance for each delay pattern in the database. The adjustment delay pattern may be read out from the database 25 and used. As described above, the adjustment delay pattern is also stored in the database 25 in advance, so that the processing time can be shortened.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the specific structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

It is the figure which showed schematic structure of the ultrasonic flaw detector which concerns on one Embodiment of this invention. It is the flowchart which showed the procedure of the ultrasonic flaw detection method of this invention. It is the figure which showed an example of the path | route of an ultrasonic beam at the time of irradiating the test object with the ultrasonic beam according to the delay pattern which concerns on a reference level. It is the figure which showed an example of the path | route of an ultrasonic beam at the time of irradiating the test object with the ultrasonic beam according to the delay pattern which concerns on a comparison level. It is the figure which represented the delay pattern with the spline curve. It is a figure for demonstrating the procedure which produces | generates an adjustment delay pattern. It is a figure for demonstrating the procedure which produces | generates an adjustment delay pattern. It is the figure which showed an example of the path | route of an ultrasonic beam at the time of irradiating an inspection target object with the ultrasonic beam according to an adjustment delay pattern. It is a figure for demonstrating the case where a vibrator is made into a two-dimensional arrangement. It is a figure for demonstrating the case where it applies to the TOFD method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Ultrasonic flaw detector 11 Transducer 12 Probe 20 Control part 21 Signal generation part 22 Reflection signal reception part 23 Analysis part 24 Adjustment part 25 Database

Claims (4)

A signal generator for generating electrical signals for driving based on at least two delay patterns for focusing the ultrasonic beam on a predetermined inspection object position in the inspection object under different conditions;
A probe that emits an ultrasonic beam corresponding to each of the driving electrical signals into the inspection object, and receives the reflected wave;
By comparing the S / N ratio of each reflected wave received by the probe, specifying the delay pattern when the reflected wave with the highest S / N ratio is obtained, and adjusting the delay pattern based on a predetermined condition An adjustment unit that generates a plurality of adjustment delay patterns, and
Each ultrasonic beam corresponding to the adjustment delay pattern is irradiated into the inspection object to receive the reflected wave, and the reflected wave with the highest S / N ratio among these reflected waves is used to obtain a defect. Ultrasonic flaw detector that performs analysis.   2. The adjustment unit according to claim 1, wherein the adjustment unit generates the plurality of adjustment delay patterns by handling the delay pattern as a spline curve passing through a plurality of control points and moving each control point according to a predetermined condition. Ultrasonic flaw detector. Under the different conditions, respectively, driving electric signals are generated based on at least two delay patterns for focusing the ultrasonic beam on a predetermined inspection target position of the inspection target,
An ultrasonic beam corresponding to each of the driving electrical signals is emitted into the inspection object, and the reflected wave is received,
By comparing the S / N ratios of the reflected waves, the delay pattern from which the reflected wave with the highest S / N ratio is obtained is identified, and a plurality of adjustment delay patterns are obtained by adjusting the identified delay pattern based on a predetermined condition. Generate
The inspection object is irradiated with an ultrasonic beam based on the adjustment delay pattern, the reflected wave is received, and the reflected wave having the highest S / N ratio among the received reflected waves is used. Ultrasonic flaw detection method for analysis.   The ultrasonic flaw detection method according to claim 3, wherein the delay pattern is handled as a spline curve passing through a plurality of control points, and each control point is moved according to a predetermined condition to generate a plurality of the adjustment delay patterns.

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