JP6414444B2 - Ultrasonic flaw detection method - Google Patents

Description

  The present invention relates to an ultrasonic flaw detection method, and more particularly to an ultrasonic flaw detection method capable of accurately obtaining the reflected wave arrival time from the surface of a flaw detection material.

  Patent Document 1 discloses an ultrasonic flaw detection method capable of obtaining a cross-sectional image of a welded portion or the like that is an exploration target region. Here, the target area of the material to be scanned is scanned at a plurality of different incident angles to receive and oscillate the ultrasonic wave, and a non-linear image is obtained from the reflected wave at each incident angle, and this is the cross-sectional shape of the target area. A cross-sectional image of the search target region is obtained by generating a non-linear search image by superimposing these frame conversion images.

JP 2010-230630

  By the way, in the above-described conventional method, even if the incident angle is changed, the distance from the ultrasonic sensor to the surface of the flaw detection material (usually the water distance because it is placed in water) is assumed to be unchanged. This water distance can be known from the time t from when the ultrasonic wave oscillates until the reflected wave arrives at the surface of the flaw detection material. However, actually, when the incident angle of the ultrasonic wave on the surface of the flaw detection material is changed, the reflected wave image from the surface of the flaw detection material becomes different. This will be described with reference to FIGS.

  8 is a reflected wave image from the surface of the flaw detection material when the incident angle is 0 °, and FIG. 9 is a reflected wave image from the surface of the flaw detection material when the incident angle is 8 °. When the incident angle is 8 °, the width of the reflected wave image from the surface of the flaw detection material is widened and the reflected wave arrival time t is shortened and therefore the water distance is shortened as compared with the incident angle of 0 °. . This is because the receiving and oscillating surface of the ultrasonic sensor has a certain length and is a concave curved surface in order to converge the ultrasonic wave at a certain distance.

  Thus, even if the position of the ultrasonic sensor is adjusted so that the water distance from the center position of the receiving and oscillating surface to the surface of the plate-shaped flaw detection material is always a constant value, The water distance from one end on the surface to the surface of the flaw detection object fluctuates and shortens, and as a result, the reflected wave arrival time t is shortened. As a result, an accurate defect image cannot be obtained.

  Therefore, the present invention solves such a problem, and provides an ultrasonic flaw detection method capable of accurately obtaining the reflected wave arrival time from the surface of the flaw detection material even if the incident angle of the ultrasonic wave is changed. Objective.

  In the first aspect of the invention, the ultrasonic wave is oscillated from the receiving and oscillating surface of the ultrasonic sensor at a predetermined incident angle with respect to the flaw detection material, and the reflected wave of the ultrasonic wave is received by the receiving and oscillating surface to obtain reflected wave data. In the ultrasonic flaw detection method, the incident angle is based on the distance along the oscillation direction from the end position of the receiving oscillation surface to the surface of the flaw detection material where the distance to the surface of the flaw detection material is the shortest at the incident angle. The arrival time of the reflected wave from the surface of the flaw detection material is corrected.

  In the first aspect of the invention, the reflected wave arrival time from the surface of the flaw detection material at a predetermined incident angle is corrected based on the distance from the end position on the receiving / oscillating surface to the surface of the flaw detection material. Accordingly, the reflected wave arrival time can be obtained with high accuracy.

  In the second aspect of the invention, the correction is obtained by scanning the ultrasonic sensor in a direction along the surface with the ultrasonic sensor facing the surface of the flaw detection material, and scanning at a plurality of different incident angles. The reflected wave data based on the arrival time of the surface reflected wave is converted into cross-sectional images, and the cross-sectional images are combined to obtain a combined cross-sectional image.

  In the second invention, reflected wave data obtained by scanning at a plurality of different incident angles are respectively imaged, and the cross-sectional images with high accuracy can be obtained by synthesizing the respective cross-sectional images.

  As described above, according to the ultrasonic flaw detection method of the present invention, the reflected wave arrival time from the surface of the flaw detection material can be obtained with high accuracy.

It is a figure which shows the path | route of the ultrasonic wave from the center of a receiving-and-oscillation surface in incident angle 0 degree. It is a figure which shows the path | route of the ultrasonic wave from the center of a receiving-and-oscillation surface in incident angle (theta) degree. It is a figure which shows the path | route of the ultrasonic wave from the end of a receiving-and-oscillation surface in incident angle 0 degree. It is a figure which shows the path | route of the ultrasonic wave from the end of a receiving-and-oscillation surface in incident angle (theta) degree. It is a graph which shows the difference of the ultrasonic reciprocation time by an incident angle. It is a figure which shows the synthetic | combination cross-sectional image obtained by performing time correction | amendment of ultrasonic reciprocation time. It is a figure which shows the synthetic | combination cross-sectional image which is not performing the time correction | amendment of ultrasonic reciprocation time. It is a figure which shows the cross-sectional image in case the incident angle is 0 degree in a prior art. It is a figure which shows the cross-sectional image in case the incident angle is 8 degrees in a prior art.

  The embodiment described below is merely an example, and various design improvements made by those skilled in the art without departing from the gist of the present invention are also included in the scope of the present invention.

  FIG. 1 schematically shows only the receiving and oscillating surface RS of the ultrasonic sensor. The receiving and oscillating surface RS is an arcuate concave surface that is curved with a predetermined radius of curvature r so that the oscillated ultrasonic waves converge at a constant distance. Here, if the arc length of the receiving and oscillating surface RS is D, the angle α is α (°) = 90D / πr.

  FIG. 1 shows a state in which an ultrasonic wave is incident on the surface S of the plate-shaped flaw detection material at an incident angle of 0 °, and the water distance from the center C of the receiving and oscillating surface RS to the flaw detection material surface S is set to WP. Has been. Therefore, the ultrasonic path (thick arrow in FIG. 1) that oscillates from the center C of the receiving and oscillating surface RS, reflects off the surface S of the flaw detection material, and returns to the receiving and oscillating surface RS is 2WP.

  If the receiving and oscillating surface RS is rotationally displaced about the ultrasonic incident point In as shown in FIG. 2, even if the ultrasonic incident angle with respect to the flaw detection material surface S changes to θ °, the receiving and oscillating surface The water distance from the center C of the RS to the flaw detection material surface S is maintained at WP, and the path of ultrasonic waves from the center C of the oscillation surface RS (thick arrow in FIG. 2) is maintained at 2WP.

  However, considering the path of ultrasonic waves oscillated from one end E1 of the receiving and oscillating surface RS with the shortest path of ultrasonic waves to be received and oscillated, as shown in FIG. When the incident angle of the sound wave is 0 °, the ultrasonic path (thick arrow in FIG. 3) oscillated from the end E1, reflected by the surface S of the flaw detection material and returning to the receiving surface RS again is 2 · (R- (r-WP) / cosα)).

  On the other hand, as shown in FIG. 4, when the ultrasonic sensor is turned and displaced in the direction of the end E1, and the ultrasonic incident angle with respect to the surface S to be inspected changes to θ (°), it oscillates from the end E1. Then, the path of the ultrasonic wave (reflected by the thick arrow in FIG. 4) reflected from the surface S to be detected and returned to the oscillation surface RS again is 2 · (r−y1) (where y1 = (r−WP) cos θ / cos). (θ + α)) and changes so as to become shorter according to the angle θ. The “distance along the oscillation direction from the end position of the receiving surface where the distance to the surface of the flaw detection material is the shortest at the predetermined incident angle to the surface of the flaw detection material” in claim 1 is ( r-y1).

  Here, the path length 2 · (r−y1) of the ultrasonic wave from the end E1 corresponding to the incident angle θ is divided by the ultrasonic wave velocity in water (which changes according to the temperature) and converted to time. FIG. 5 is a graph showing the difference between the path length 2 · (r− (r−WP) / cos α)) and the time when the incident angle is 0 °. In the figure, the line x is the theoretical value, the line y is the experimental value, and the experimental value is almost in line with the theoretical value. Note that a negative time difference indicates that the path is shortened.

  Therefore, the arrival time t of the reflected wave obtained at each incident angle θ is corrected to the original time axis of the reflected wave arrival time at the incident angle 0 ° based on the theoretical value of the above graph (in the graph of FIG. 5). Arrow line).

  In this way, the reflected wave arrival time is corrected in the reflected wave data obtained by scanning at each incident angle, and the reflected wave data based on the time-corrected reflected wave arrival time t is cross-sectional imaged respectively. By synthesizing the respective cross-sectional images, a highly accurate synthetic cross-sectional image can be obtained. The composite cross-sectional image F1 thus obtained is shown in FIG. The combined cross-sectional image F1 shows the shape of the circular defect well and has a relatively high luminance. On the other hand, the synthetic cross-sectional image F2 obtained from the reflected wave data that has not been time-corrected has the shape of the circular defect collapsed and the luminance is relatively low as shown in FIG. Absent.

  In the above embodiment, in order to compensate for an error of a scanner that scans the flaw detection material with respect to the flaw detection material, if the flaw detection material test piece for calibration is used to obtain the correction graph, Further, it is possible to obtain a synthesized cross-sectional image with high accuracy.

Claims (2)

In the ultrasonic flaw detection method for obtaining reflected wave data by oscillating an ultrasonic wave from a receiving / oscillating surface of an ultrasonic sensor at a predetermined incident angle with respect to a material to be detected, receiving the reflected wave of the ultrasonic wave on the receiving / oscillating surface, From the surface of the flaw detection material at the incident angle based on the distance along the oscillation direction from the end position of the receiving oscillation surface to the flaw detection material surface where the distance to the surface of the flaw detection material becomes the shortest at the incident angle. An ultrasonic flaw detection method characterized by correcting the reflected wave arrival time of a laser beam. The corrected surface reflected wave arrival time obtained by scanning the ultrasonic sensor in a direction along the surface with the ultrasonic sensor facing the surface of the flaw detection material, and scanning at a plurality of different incident angles. The ultrasonic flaw detection method according to claim 1, wherein the reflected wave data based on each is converted into a cross-sectional image, and the respective cross-sectional images are combined to obtain a combined cross-sectional image.