JP5846367B2 - Flaw detection method and flaw detection apparatus for welds using TOFD method - Google Patents

Description

  The present invention relates to a flaw detection method and a flaw detection apparatus for a welded part, and more particularly to a flaw detection method and a flaw detection apparatus using a TOFD (Time Of Flight Diffraction) method for flaw detection of nozzles connected by welding.

  In the TOFD method, two longitudinal wave probes (a transmitting probe and a receiving probe) face each other at a constant interval on the surface of the specimen, and lateral waves transmitted from the specimen surface or from the back of the specimen This is a method for detecting a defect or measuring a defect size by using a difference in propagation time between a reflected wave and a diffracted wave from a defect tip. In the TOFD method, attention is paid to only the longitudinal wave received earliest so as not to be affected by the mode conversion transverse wave generated at the tip of the defect in the analysis. In general, a wide range of tests are performed at once by using a probe with low directivity.

  A conventional flaw detection apparatus using TOFD is disclosed in, for example, Japanese Patent Laying-Open No. 2005-70017 (Patent Document 1). According to Patent Document 1, a pair of a transmitting probe 1 and a receiving probe 2 are arranged on the surface of an object 3 at a predetermined distance from the transmitting probe 1 and the target is detected. The ultrasonic wave is radiated into the object, and the diffracted wave generated at the end of the existing defect in the object is received by the receiving probe 2 to detect the longitudinal wave component and the transverse wave component of the diffracted wave, respectively. Then, based on the arrival time difference between the detected longitudinal wave component and the transverse wave component, the point that the distance L from the defect end portion where the diffracted wave is generated to the wave receiving probe 2 is estimated is disclosed. In addition, in the patent document, the position of the upper end of the flaw that makes the propagation path lengths from the transmission probe to the reception probe equal to each other focuses on the positions of the transmission probe and the reception probe. It is disclosed that it exists on an elliptical locus.

JP 2005-70017 A

  The inspection of the jig of a flaw detection apparatus that performs flaw detection using the conventional TOFD method and the welded portion of a small-diameter pipe circumferential joint has been configured as described above. Each of them was configured to detect a set of probes including a transmitting side and a receiving side while maintaining a predetermined interval with the welding line at the center. With such a configuration, flaw detection is possible when the welded portion is arranged so as to be positioned at the center of both probes, but the weld line, such as a nozzle welded portion, is used for transmission and reception. There is a problem that flaws cannot be detected when the probe is not located at the center of the probe.

  The present invention has been made to solve the above-described problems, and provides a flaw detection apparatus for a nozzle and a method thereof that can easily detect the position of a nozzle flaw connected by welding by the TOFD method. Objective.

According to the present invention, a flaw detection method for a welded portion using the TOFD method includes a transmitting side probe and a receiving side probe arranged with the welded portion interposed therebetween, and the welded portion at a predetermined angle from the transmitting side probe. An elliptical trajectory that equalizes the propagation path length of the ultrasonic wave from the transmitter probe to the receiver probe by transmitting the ultrasonic beam to the receiver, receiving the diffracted wave from the flaw of the welded portion by the receiver probe , Calculate the echo heights of the diffracted waves on the detected elliptical trajectory, switch the reception angle of the receiving probe, and based on the calculated echo heights of the diffracted waves Calculate the position of the flaw in the weld.
Preferably, the position of the flaw in the welded portion is detected according to the intensity of the received diffracted wave with a plurality of reception angles switched.

  In another aspect of the present invention, a flaw detection apparatus for a welded portion using the TOFD method includes a transmitting side probe and a receiving side probe arranged with the welded portion interposed therebetween, and the transmitting side probe is An ultrasonic beam is transmitted to the welded portion at a predetermined angle, a diffracted wave from a flaw of the welded portion is received by a receiving side probe, and an ultrasonic wave propagates from the transmitting side probe to the receiving side probe. An ellipse trajectory calculating means for calculating an elliptical trajectory for equalizing the path length and an echo height for calculating an echo height of a plurality of diffracted waves on the calculated elliptical trajectory by switching a plurality of reception angles of the receiving probe. And a flaw position calculating means for detecting a flaw position of the weld based on the ellipse trajectory calculated by the ellipse trajectory calculating means and the echo height calculated by the echo height calculating means.

  According to the present invention, the elliptical trajectory in which the transmission side probe and the reception side probe are arranged at predetermined intervals and the propagation path length of the ultrasonic wave from the transmission side probe to the reception side probe is made equal. Calculating the reception angle of the receiving probe, calculating the echo heights of the diffracted waves on the elliptical trajectory, and based on the echo height detected on the elliptical trajectory, Since the position of the flaw is calculated, it is possible to easily detect the position of the flaw even when the welded portion is located at a biased position between the transmitting and receiving side probes.

It is a figure which shows a horizontal hole test body. It is a figure which shows a horizontal hole test body. It is a figure which shows a horizontal hole test body. It is a figure which shows the arrangement position of the transmission / reception probe at the time of connecting a nozzle to a trunk | drum by welding. It is sectional drawing which shows a groove shape. It is a figure which shows the flaw detection possible area | region in case plate | board thickness is 200 mm. It is sectional drawing which shows arrangement | positioning of the probe in the trunk | drum which has the nozzle connected by the welding part. It is a top view which shows arrangement | positioning of the probe in the trunk | drum which has the nozzle connected by the welding part. It is a figure which shows the view of the transmission angle of the ultrasonic wave from the transmission side probe to the flaw in a welding part, and the reception angle of the ultrasonic wave which a receiving side probe receives from a flaw. It is a figure which shows the concept for calculating a position, without using a transmission / reception probe. It is a figure which shows the method of detecting a position, without using a transmission / reception probe. It is a block diagram of a flaw detector. It is a figure which shows the result display screen by the TOFD method using specific software.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, the basic concept of the present invention will be described. In order to know in which range the defects (defects) of the welded portion when the nozzles are joined by welding can be detected, the inventors produced transverse hole specimens 101 to 103 having transverse holes simulating flaws. The position of the transmitter / receiver probe and the transmission / reception angle for finding the position of the flaw were found.

  “Flaw” refers to an incomplete portion or a discontinuous portion determined from the result of a nondestructive test, and among these, a flaw that fails is referred to as a “defect”.

  The manufactured horizontal hole specimen 101 is shown in FIG. 1A is a plan view, FIG. 1B is a front view (an arrow view indicated by BB in FIG. 1A), and FIG. 1C is a side view (FIG. (A) is a view taken along the line CC in FIG. Referring to FIG. 1, a lateral hole test body 101 is a rectangular parallelepiped plate having a length of 800 mm, a height of 250 mm, and a thickness of 40 mm, and has through holes 102 and 103 at different positions as shown in the figure. Yes. Specifically, the horizontal hole test body 101 has through holes 102 and 103 having a diameter of 5 mm at positions where the depth is 20 mm and 50 mm.

  A horizontal hole specimen 102 is shown in FIG. 2A is a plan view, FIG. 2B is a front view (a view taken along the line BB in FIG. 2A), and FIG. 2C is a side view (FIG. (A) is a view taken along the line CC in FIG. Referring to FIG. 2, the horizontal hole test body 102 is a rectangular parallelepiped plate having a length of 800 mm, a height of 250 mm, and a thickness of 40 mm, and as shown in the drawing, a through hole having a diameter of 5 mm at positions of 30 mm and 100 mm deep. Holes 112 and 113.

  Similarly, with reference to FIG. 3, the horizontal hole test body 103 has through holes 122 and 123 having a diameter of 6 mm at positions of 150 mm and 200 mm in depth.

  FIG. 4 is a diagram showing the arrangement position of the transmission / reception probe considered by the inventors when the nozzle 131 is connected to the body portion 133 by welding. Referring to FIG. 4, when the nozzle 131 is welded to the body portion 133, the receiving side probe 11 is disposed on the nozzle neck portion 132, and the welding side 134 is sandwiched with respect to the receiving side probe 11. The probe 12 is arranged.

  Here, the transmission-side probe 12 transmits at a frequency of 5 MHz and a transmission angle of 60 ° counterclockwise from the plane on which the transmission-side probe 12 is placed.

  Prior to the examination of the flaw detection range, a groove shape was assumed. FIG. 5 shows a groove shape (shaded portion in the figure) of a body portion having a thickness of 200 mm based on an existing nozzle groove shape. Referring to FIG. 5, the groove 135 has an upper portion 115 and a lower portion 116, and the upper portion 115 has a dimension of 115 mm and a groove angle θ of 35 °. Even if the plate thickness changed, the weld angle was assumed such that the bead width was narrowed without changing the groove angle. At this time, the bead toe on the nozzle 131 side was set as a reference position (indicated by Y = 0 in the figure).

  When checking the flaw detection range, the transmission / reception probe is arranged at a predetermined interval using the horizontal hole specimens 101, 111, 121, and the transmission / reception probe is moved relative to the horizontal hole to obtain the maximum echo. Were obtained, and positions where the echo height was ½ (−6 dB) and ¼ (−12 dB) of the maximum echo were examined, and the results were collected for each probe and position to obtain a flaw detection range.

  The flaw detection arrangement and the flaw detection possible range were examined according to the dimensions by varying the plate thickness under the above conditions. FIG. 6 is a diagram showing a flaw-detectable region when the plate thickness is 200 mm. A hatched area is a flaw-detectable area. Here, four transmission probes are used. The first to fourth transmission side probes 42 to 45 are referred to from the side closer to the reception side probe 41. The transmission condition of the first and second transmission side probes 42 and 43 is 5 MHz 60 °, and the transmission condition of the third and fourth transmission side probes 44 and 45 is 2 MHz 60 °.

  In FIG. 6, Y = 0 indicates the reference position, the receiving probe 41 is placed at a position a distance a away from the reference position on the left side, and the transmitting probes 42 to 45 are on the right side from the reference position. Are placed at positions separated by distances e, d, c, and b, respectively. Further, a line indicated by a two-dot chain line extending obliquely from the left side of the lower end of the transmission side probe 42 to the lower left direction is the shape of the welded portion.

  The reception condition of the receiving probe 41 is 5 °, 25 °, and 60 ° at 5 MHz for a transmission condition of 5 MHz 60 °, and 2 MHz for a transmission condition of 2 Hz 60 °. 5 °, 25 °, and 60 °.

  As shown in FIG. 6, with a plate thickness of 200 mm, the transmission conditions of the transmitting probe are 2 MHz, 5 MHz, 60 °, and the receiving conditions of the receiving probe are 5 °, 25 °, and 60 ° at 2 MHz. If 5 °, 60 °, 5 MHz, 5 °, 25 °, and 60 °, a necessary region can be detected. Thus, it can be seen that flaw detection of the welded portion of the nozzle is possible if the transmitting side and receiving side probes are arranged so as to cover the welded portion according to the plate thickness.

  Next, a specific flaw detection method for the nozzle welded portion and a method for determining the arrangement of the probe will be described. From the above, the flaw detection method for the nozzle weld and the arrangement of the probe were determined as follows.

  Although flaw detection is possible from the inner surface of the tube body, it is performed from the outer surface side. The transmission and reception frequencies use a longitudinal wave of 5 MHz or 2 MHz for each applied plate thickness. Specifically, a longitudinal wave of 5 MHz is used when the plate thickness is 50 mm or less, and a longitudinal wave of 2 MHz and 5 MHz is used together when the plate thickness is 50 mm to 200 mm.

  The combination of the transmitter probe and the receiver probe is as follows.

  In order to cover the entire welded portion, flaw detection is performed at three kinds of reception angles.

  The probe is a combination of 60 ° on the transmission side and 5 ° on the reception side, 60 ° on the transmission side and 25 ° on the reception side, and 60 ° on the transmission side and 60 ° on the reception side.

  Next, the arrangement of the probes will be described. FIG. 7 is a view showing the arrangement of the probe in the body portion 62 having the nozzle 61 connected by the welding portion 60. Referring to FIG. 7, a reception side probe 51 and transmission side probes 52 and 53 are arranged with a welded portion 60 interposed therebetween. FIG. 8A is a plan view showing a preferred arrangement in the probe as shown in FIG. FIG. 8B is a view similar to FIG. 8A, but showing a case where the diameter of the nozzle 61 is large. Specifically, FIG. 8A is a view when the nozzle weld radius is 150 mm, and FIG. 8B is a view showing a case where the nozzle weld radius is 300 mm.

  Referring to FIGS. 7 and 8, the first transmitting probe 52 and the second transmitting probe 53 are placed on the opposite side of the nozzle 61 with the weld 60 interposed therebetween, and the receiving probe. 51 is placed on the nozzle 61 side.

  Also, as shown in FIG. 8A, a set of a 60 ° transmitting probe 52c and a 5 ° receiving probe 51c, a 25 ° transmitting probe 52b, and a 25 ° receiving side From the center of the nozzle welded portion 60, three sets of transmitting side and receiving side probes, that is, a set of probes 51 b and a set of 60 ° transmitting side probe 52 a and 60 ° receiving side probe 51 a are arranged. If the flaws are arranged in a fan shape, the flaws can be detected at once.

  Next, the evaluation method of the flaw height and flaw depth in this embodiment will be described. FIG. 9 is a diagram showing the concept of the transmission angle of the ultrasonic wave from the transmitting probe 12 to the flaw and the reception angle of the ultrasonic wave received by the receiving probe 11 from the flaw. Here, in order to detect flaws in the welded portion of the nozzle, the receiving probe 11 is disposed in the vicinity of the welded portion 60, and the transmitting probe 12 is disposed in a position away from the welded portion 60.

  Let f be the interval between the ultrasonic incident positions of the transmitting probe 12 and the receiving probe 11. Among the ultrasonic beams transmitted from the transmission side probe 12 to the reception side probe 11, an elliptical trajectory having a propagation path length w that reflects the flaw 70 is obtained, and this and an echo in the reception side probe 11 are obtained. The position where the intersection with the high reception angle θ is reflected by the scratch 70 is shown.

  Since the propagation path length w reflected by the flaw 70 can be read from the flaw detection figure, if the elliptical locus is calculated and the reception angle θ by the receiving probe 11 can be estimated, the position of the flaw can be calculated.

  As the reception angle θ of the reception side probe 11, it is necessary to obtain an angle having the highest echo height. This can be done by scanning the receiving angle in the receiving probe 11.

  On the other hand, you may obtain | require from the echo height of the echo estimated as the same flaw detected with the receiving side probe in each of several angles, for example, each angle of 5 degrees, 25 degrees, and 60 degrees. The probes having the same frequency and vibration diameter are considered to have substantially the same spread of the ultrasonic beam, and the reception angle is obtained from the ratio of the echo heights of the probes. For example, in FIG. 9, if the ratio of the echo height of θ is 5 ° and 25 ° is 1: 2, there is a flaw at a position where θ is divided by 2: 1 between 5 ° and 25 °. It can be judged.

  Next, the flaw depth calculation method will be described. As described above, the flaw position is calculated from the propagation path length and the echo height of the received wave at the position of the upper end of the transmission / reception side probe 11, 12.

  FIG. 10 is a diagram illustrating a specific method for calculating a position without using a transmission / reception probe. FIG. 10A schematically illustrates the concept, and FIG. 10B illustrates the actual transmitter probe 12 and the receiver probe before being modeled as illustrated in FIG. It is a figure which shows the positional relationship of the child 11 and the flaw 70 specified by both.

  Here, it is assumed that the positions X = 0 and Y = 0 are the origin, and the transmitting probe 11 and the receiving probe 12 are positioned at the position of the focal point F. w / 2 + w / 2 = w is a distance that forms an elliptical trajectory that equalizes the propagation path length of the ultrasonic wave from the transmitting probe 12 to the receiving probe 11, and θ is a different receiving probe. This is the reception angle obtained from the echo height of the received wave.

  Further, a is the long side of the ellipse, b is the short side of the ellipse, and c is the Y-axis intercept of the received wave obtained from the echo height.

  In this example, an intersection 14 (indicated by a circle) between the elliptical trajectory and a straight line obtained by subtracting the reception angle θ from the position of the receiving probe 11 is estimated as the position of the flaw 70.

  Specifically, the position 14 of the flaw 70 is obtained from a simultaneous equation of an ellipse and a straight line. In this way, the coordinates (x, y) of the intersection can be obtained.

  Next, calculation of the height of the scratch 70 will be described. Assuming that there is a flaw on the X coordinate of the upper end position 14 of the flaw 70 obtained above, the value of the X coordinate is substituted into the ellipse equation calculated from the echo propagation distance from the lower end of the flaw 70 to obtain the lower end position. Ask. The difference between the upper end position and the lower end position is the height of the flaw 70.

Here, the relational expression for obtaining the intersection is as follows.
y = √ ((1-X ² ) / a ² ) * b ² )
y = tan η × X + c

  Next, a specific calculation method will be described. Here, the case where a through hole is detected as a flaw using a test body having a plurality of through holes as shown in FIGS. FIG. 11 shows a display screen of a personal computer. FIG. 11A is a diagram showing a case where the position of a flaw is specified with a cursor with respect to a specific flaw in the specimen when the probe is received by a probe having a reception angle of 60 °. B) is a diagram showing the echo height in that case. In FIG. 11A, the horizontal axis indicates the distance from the end of the specimen, and the vertical axis indicates the propagation time. In FIG. 11B, the horizontal axis indicates the distance from the end of the specimen, and the vertical axis indicates the echo height. Similarly, FIGS. 11C and 11D show the flaw position and echo height when the reception angle is 25 °, and FIGS. 11E and 11F show the flaw position and echo height when the reception angle is 5 °. Indicates.

  With reference to FIGS. 11A and 11B, a method for specifying the position of a flaw when the probe is received by a probe having a reception angle of 60 ° will be described. As shown in FIG. 11A, a plurality of flaws provided on the specimen are displayed on the screen as indicated by reference numerals 71, 72 and the like. Of the displayed flaws, a desired flaw (here, reference numeral 72) is selected with the cursor lines 81-83. Here, the cursor line 82 indicates the position of the upper end portion of the flaw, and the cursor line 83 indicates the position of the lower end portion of the flaw.

  In FIG. 11A, when the position of the flaw is specified, an echo waveform 86 at that position is displayed as shown in FIG. Here, the upper end portion of the flaw indicated by the cursor line 82 corresponds to the minimum portion 86 a of the echo waveform 86, and the lower end portion of the flaw indicated by the cursor line 83 corresponds to the maximum portion 86 b of the echo waveform 86. When the position of the flaw is specified in this way, data such as the echo height at that time is automatically input as shown in FIG.

  FIG. 12 is a block diagram of the flaw detection apparatus 20 having a display unit that displays the display screen as shown in FIG. Referring to FIG. 12, flaw detection apparatus 20 includes a control unit 21, a display unit 22, a calculation unit 23, and an I / O unit 24 that serves as an interface between reception-side probe 11 and transmission-side probe 12. The control unit 21 controls the display unit 22, the calculation unit 23, and the I / O unit 24 to specify the position of the flaw.

  Next, a method for analyzing the position of the flaw 70 using the flaw detection apparatus 20 will be described. The flaw detection apparatus 20 has a flaw depth calculation function. This function is linked with spreadsheet software such as Excel (registered trademark), and the cursor display position of the flaw detection result, propagation time, echo height, etc. are given to this spreadsheet software. This is a function for calculating and displaying the result on the display unit.

  As described above, the calculation result is displayed on the display unit 22 in real time in accordance with the movement of the cursor.

  As an example, FIG. 13 shows a result display screen by the TOFD method using this software.

  FIG. 13A is a diagram showing an example of a software display screen when the position where the cursor is not used is specified as shown in FIG. Here, the nominal refraction angle, flaw detection gain value, top echo height, bottom echo height, top beam propagation time, and bottom beam propagation time of the receiving probe in a certain flaw detection example, respectively, The state automatically input for each angle is shown. As described above, the gain of flaw detection sensitivity is adjusted for each nominal refraction angle of the receiving probe 11 and the upper end echo height, the lower end echo height, the upper end propagation time, and the lower end propagation time are displayed.

  When this is input, as shown in FIG. 12 (B), the flaw position, flaw depth, and flaw height are automatically calculated based on the above equations.

  In the above-described embodiment, the case where the refraction angle is 5 °, 25 °, or 60 ° has been described. However, the present invention is not limited to this. Or other combinations at a plurality of angles.

  Moreover, although the case where the transmission angle is 60 ° has been described in the above embodiment, the present invention is not limited to this and may be an arbitrary angle.

  Although the embodiments of the present invention have been described with reference to the drawings, the present invention is not limited to the illustrated embodiments. Various modifications can be made to the illustrated embodiment within the same scope or equivalent scope as the present invention.

  Since the flaw detection apparatus and the flaw detection method using the TOFD method according to the present invention can easily calculate the position of the flaw of the nozzle connected by welding, the flaw detection apparatus for the weld part of the nozzle and the method thereof It is advantageously used.

  11, 41 Receiver probe, 12, 42 Transmitter probe, 20 Flaw detector, 21 Control unit, 22 Display unit, 23 Calculation unit, 24 I / O unit, 60 Welding unit, 61, 131 Nozzle, 62 133 Body, 101, 111, 121 Horizontal hole specimen, 102, 103, 112, 113, 122, 123 Through hole.

Claims (3)

A method for flaw detection of a weld using the TOFD method,
A transmitting probe and a receiving probe are arranged across the weld,
An ultrasonic beam is transmitted from the transmitting probe to the weld at a predetermined angle;
Receiving the diffracted wave from the flaw of the weld by the ultrasonic beam at the receiving probe;
Calculating an elliptical trajectory that equalizes the propagation path length of the ultrasonic wave from the transmitting probe to the receiving probe;
By switching a plurality of reception angles of the reception probe, calculating echo heights of a plurality of diffraction waves on the detected elliptical locus,
Based on the detected echo height of the plurality of diffracted waves, to calculate the position of the flaws of the weld,
A method for flaw detection of a welded portion using the TOFD method, wherein the receiving side probe is arranged in the vicinity of the welded portion, and the transmitting side probe is arranged away from the welded portion.   The method for flaw detection of a welded portion using the TOFD method according to claim 1, wherein the detection of the position of a flaw in the welded portion is detected according to the intensity of a diffracted wave with a plurality of reception angles switched. A flaw detection apparatus for welds using the TOFD method,
Including a transmitter probe and a receiver probe disposed across the weld,
The transmitting probe transmits an ultrasonic beam to the weld at a predetermined angle;
The receiving probe receives a diffracted wave from a flaw of the weld by the ultrasonic beam,
Elliptic trajectory calculating means for calculating an elliptic trajectory for equalizing the propagation path length of the ultrasonic wave from the transmission probe to the reception probe;
Echo height detection means for switching a plurality of reception angles of the reception probe and calculating echo heights of a plurality of diffracted waves on the calculated elliptical locus;
Flaw position calculating means for calculating the position of the flaw of the weld based on the elliptical trajectory calculated by the elliptic trajectory calculating means and the echo height calculated by the echo height calculating means,
A flaw detection apparatus for a welded portion using a TOFD method, wherein the receiving side probe is arranged in the vicinity of the welded portion, and the transmitting side probe is arranged away from the welded portion.

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