Ultrasonic inspection method and ultrasonic inspection system

Abstract

The accuracy of inspection is improved by estimating the focal position taking into account the refraction of ultrasonic waves within the object being inspected. [Solution] The ultrasonic inspection method is an ultrasonic inspection method for inspecting the inside of an object to be inspected M using ultrasonic waves transmitted from the concave surface 111a of a transmitting-side focused ultrasonic probe 111, and is characterized in that a predetermined range is defined within the entire range viewed from the direction of the radius of curvature of the concave surface 111a, and the depth position from the surface of the object to be inspected at the central axis C is calculated based on the distance from the position where the propagation route of the ultrasonic waves extending from the end of the predetermined range in a direction perpendicular to the concave surface 111a reaches the surface of the object to be inspected to the central axis C of the concave surface 111a and the refraction at the shear wave sound speed depending on the material of the object to be inspected, the depth position is estimated to be the focal position, and the distance between the transmitting-side focused ultrasonic probe 111 and the object to be inspected M is determined based on the focal position.

Description

[Technical Field]

[0001] The present invention relates to an ultrasonic inspection method and an ultrasonic inspection system for performing inspection using ultrasonic waves. [Background technology]

[0002] Conventionally, in order to obtain images showing the presence or absence of defects inside a test object using airborne ultrasonic flaw detection, concave focused ultrasonic probes with a fixed radius of curvature are used for both the transmitting and receiving ultrasonic probes.

[0003] For example, the applicant has proposed an airborne ultrasonic flaw detection device using such a concave focused ultrasonic probe, which includes a receiving unit that receives signals output from the receiving ultrasonic probe, and an output unit that outputs an image indicating the presence or absence of defects in the test object based on the signal level of the electrical signal received by the receiving unit, and the receiving surface of the receiving ultrasonic probe has an area smaller than that of the transmitting surface, and receives ultrasonic waves that are transmitted by the transmitting ultrasonic probe toward the test object and pass through the test object without being reflected within the test object, but does not receive ultrasonic waves that are transmitted from the test object after being reflected within the test object (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-176916 Summary of the Invention [Problem to be solved by the invention]

[0005] When inspecting an object using airborne ultrasonic waves with a focused ultrasonic probe, the center of the radius of curvature of the concave surface of the focused ultrasonic probe is assumed to be the focal position, and measurement is performed by aligning this focal position with the position to be inspected on the object.

[0006] However, ultrasonic waves are refracted as they propagate through the air, reach the surface of the object under inspection, and propagate into the object under inspection. Due to this refraction, the focal position of the ultrasonic waves within the object under inspection is located closer to the surface of the object than the center of the radius of curvature. Furthermore, since ultrasonic waves transmitted from the outside of the concave surface are refracted more, if the center of the radius of curvature of a focused ultrasonic probe for a concave surface is assumed to be the focal position, spherical aberration occurs, causing the focal positions to not align. As such, if the assumed focal position is deviated from the actual focal position, the resolution and clarity of the image showing the presence or absence of defects will decrease, making it difficult to see the details within the object under inspection, resulting in a problem of reduced inspection accuracy.

[0007] The present invention has been made in consideration of the above points, and aims to improve the accuracy of inspection by estimating the focal position taking into account the refraction of ultrasonic waves within the object to be inspected. [Means for solving the problem]

[0008] (1) An ultrasonic inspection method for inspecting the inside of an object to be inspected by ultrasonic waves transmitted from a concave surface of a focused ultrasonic probe, comprising: defining a predetermined range within the entire range as viewed from the direction of the radius of curvature of the concave surface; a distance from the position where the propagation route of the ultrasonic wave extending from the end of the predetermined range in a direction perpendicular to the concave surface reaches the surface of the object to be inspected to the central axis of the concave surface, and based on the refraction at a shear wave sound velocity according to the material of the object to be inspected, the depth position from the surface of the object to the central axis is calculated, and the depth position is estimated to be the focal position; an ultrasonic inspection method, characterized in that a distance between the focused ultrasonic probe and the object to be inspected is determined based on the focal position;

[0009] The ultrasonic inspection method (1) is an ultrasonic inspection method for inspecting the inside of an object to be inspected by ultrasonic waves transmitted from the concave surface of a focused ultrasonic probe, and includes the following steps. A predetermined range is defined within the entire range as viewed from the direction of the radius of curvature of the concave surface. The ultrasonic propagation route extending from the end of the specified range in a direction perpendicular to the concave surface calculates the depth position from the surface of the object to the central axis of the concave surface based on the distance from the position where it reaches the surface of the object to be inspected to the central axis of the concave surface and the refraction at the shear wave sound speed depending on the material of the object to be inspected, and this depth position is estimated to be the focal position. Then, based on this focal position, the distance between the focused ultrasonic probe and the object to be inspected is determined.

[0010] According to the ultrasonic inspection method (1), the depth position from the surface of the object to be inspected on the central axis is calculated based on the distance from the position where the propagation route of the ultrasonic waves extending in a direction perpendicular to the concave surface from the end of a predetermined range of the entire range viewed from the curvature radius direction of the concave surface reaches the surface of the object to the central axis of the concave surface and the refraction at the shear wave sound velocity depending on the material of the object to be inspected, and the depth position is estimated as the focal position, and the distance between the focused ultrasonic probe and the object to be inspected is determined based on this focal position. That is, the focal position of the ultrasonic waves transmitted from the concave surface is estimated based on the propagation direction of the ultrasonic waves within the object to be inspected, taking into account the refraction of the ultrasonic waves depending on the material of the object to be inspected. Therefore, by estimating the focal position taking into account the refraction of ultrasonic waves within the object to be inspected, the accuracy of the inspection can be improved.

[0011] (2) defining a plurality of the predetermined ranges having mutually different sizes; Estimating the focus position for each of the plurality of predetermined ranges; The ultrasonic inspection method described in (1) is characterized in that the distance between the focused ultrasonic probe and the object to be inspected is determined based on the position where the focus positions are densely packed among the plurality of focus positions.

[0012] Here, the focal position taking refraction into consideration differs depending on the size of the specified range of the concave surface of the focused ultrasonic probe, but by determining the distance between the focused ultrasonic probe and the object to be inspected based on a position where multiple focal positions are concentrated, it can be estimated that the image obtained by inspection, which indicates the presence or absence of defects, will have higher resolution and clarity than when the distance between the focused ultrasonic probe and the object to be inspected is determined based on other positions.

[0013] In the ultrasonic inspection method (2), a plurality of predetermined ranges having different sizes are defined, and the focal position is estimated for each of the plurality of predetermined ranges. Based on the position where the plurality of focal positions are concentrated, the distance between the focused ultrasonic probe and the object to be inspected is determined. This makes it possible to further improve the accuracy of the inspection.

[0014] (3) An ultrasonic inspection system for inspecting the inside of an object to be inspected by ultrasonic waves transmitted from a concave surface of a focused ultrasonic probe, a predetermined range defining means for defining a predetermined range within the entire range as viewed from the direction of the radius of curvature of the concave surface; a focal position estimation means for calculating a depth position from the surface of the object to be inspected on the central axis based on a distance from a position where a propagation route of an ultrasonic wave extending from an end of the predetermined range in a direction perpendicular to the concave surface reaches the surface of the object to the central axis of the concave surface and based on refraction at a shear wave sound velocity according to the material of the object to be inspected, and estimating the depth position as a focal position; and a distance determining means for determining a distance between the focused ultrasonic probe and the object to be inspected based on the focal position.

[0015] The ultrasonic inspection system (3) provides the same effects as the ultrasonic inspection method (1).

[0016] (4) The focused ultrasonic probe includes a transmitting focused ultrasonic probe that transmits ultrasonic waves and a receiving focused ultrasonic probe that receives ultrasonic waves, the transmitting focused ultrasonic probe is disposed on one surface side of the object to be inspected, The receiving side focused ultrasound probe comprises: is placed on the other surface side of the inspection object, The ultrasonic inspection system according to (3), characterized in that the distance to the object to be inspected is greater than the distance between the transmitting focused ultrasonic probe and the object to be inspected in order to reduce the influence of multiple reflection signals within the object to be inspected.

[0017] In the ultrasonic inspection system (4), the focused ultrasonic probe includes a transmitting focused ultrasonic probe that transmits ultrasonic waves and a receiving focused ultrasonic probe that receives ultrasonic waves. The transmitting focused ultrasonic probe is arranged on one side of the object to be inspected, and the receiving focused ultrasonic probe is arranged on the other side of the object to be inspected. The distance between the receiving focused ultrasonic probe and the object to be inspected is greater than the distance between the transmitting focused ultrasonic probe and the object to be inspected in order to reduce the influence of multiple reflection signals from within the object to be inspected.

[0018] Here, if the distance between the receiving focused ultrasonic probe and the object to be inspected is smaller than or equal to the distance between the transmitting focused ultrasonic probe and the object to be inspected, the receiving focused ultrasonic probe will receive ultrasonic waves that are multiple-reflected below the internal defect of the object to be inspected, resulting in a false image in the image obtained by inspection showing the presence or absence of a defect, reducing the resolution and clarity.

[0019] According to the ultrasonic inspection system of (4), by making the distance between the receiving focused ultrasonic probe and the object to be inspected larger than the distance between the transmitting focused ultrasonic probe and the object to be inspected, the multiply reflected ultrasonic waves propagate outside the receiving focused ultrasonic probe, so that the receiving focused ultrasonic probe can avoid receiving the multiply reflected ultrasonic waves. This makes it possible to prevent the occurrence of false images in the images obtained by inspection that indicate the presence or absence of defects, which would reduce the sense of resolution and clarity, thereby further improving the accuracy of the inspection. [Effects of the Invention]

[0020] According to the present invention, the accuracy of inspection can be improved by estimating the focal position taking into account the refraction of ultrasonic waves within the object to be inspected. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a diagram illustrating an overview of an ultrasonic inspection system according to an embodiment of the present invention. [Figure 2]FIG. 2 is a diagram illustrating the functional configuration of a calculation unit of the ultrasound inspection system according to the embodiment of the present invention. [Figure 3] FIG. 2 is a diagram illustrating information acquired by a calculation unit of an ultrasonic inspection system according to an embodiment of the present invention. [Figure 4] FIG. 2 is a diagram illustrating processing by a calculation unit of the ultrasonic inspection system according to one embodiment of the present invention. [Figure 5] 10A and 10B are diagrams showing an example of a processing result by a focal position estimation means of a calculation unit in the ultrasonic inspection system according to one embodiment of the present invention. [Figure 6] 10A and 10B are diagrams illustrating processing by a distance determination means of a calculation unit in an ultrasonic inspection system according to an embodiment of the present invention. [Figure 7] FIG. 1 is a diagram illustrating a test specimen used as an object to be inspected in an experimental example. [Figure 8] 8A and 8B are diagrams for explaining Experimental Example 1. Fig. 8A is a diagram showing the positional relationship between an inspection object (test piece), a transmitting-side focused ultrasonic probe, and a receiving-side focused ultrasonic probe in Experimental Example 1. Fig. 8B is a diagram showing an inspection result image in Experimental Example 1. [Figure 9] 9(a) is a diagram illustrating the positional relationship between an inspection object (test piece), a transmitting-side focused ultrasonic probe, and a receiving-side focused ultrasonic probe in Experimental Example 2. FIG. 9(b) is a diagram illustrating an inspection result image in Experimental Example 2. [Figure 10] 10(a) is a diagram illustrating the positional relationship between the object to be inspected (test piece), the transmitting-side focused ultrasonic probe, and the receiving-side focused ultrasonic probe in Experimental Example 2. FIG. 10(b) is a diagram illustrating an inspection result image in Experimental Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0022] An embodiment of the present invention (hereinafter referred to as the present embodiment) will be described in detail below with reference to the drawings. In each drawing, the same or similar components are designated by the same reference numerals.

[0023] FIG. 1 is a diagram illustrating an overview of an ultrasonic inspection system according to one embodiment of the present invention. As shown in FIG. 1, the ultrasonic inspection system 1 of this embodiment includes an ultrasonic inspection device 10 that uses ultrasonic waves to inspect defects inside an inspection object M, and a calculation unit 20 that determines the distance between a focused ultrasonic probe 11 of the ultrasonic inspection device 10 and the inspection object M.

[0024] The ultrasonic inspection device 10 includes a focused ultrasonic probe 11, a driving unit 12, and a control unit 13, and transmits ultrasonic waves to an inspection object M and receives ultrasonic waves that have passed through the inspection object M.

[0025] The focused ultrasonic probe 11 includes a transmission-side focused ultrasonic probe 111 and a reception-side focused ultrasonic probe 112 that are arranged so as to sandwich the object M to be inspected.

[0026] The transmitting side focused ultrasonic probe 111 is arranged on one surface M1 side of the object to be inspected M, and the transmitting surface, which is the vibration surface, is a concave surface 111a having a certain diameter and formed with a predetermined radius of curvature, and ultrasonic waves are transmitted from the concave surface 111a toward the object to be inspected M by voltage supplied from the driving unit 12.

[0027] The receiving side focused ultrasonic probe 112 is arranged on the other side M2 ​​of the object to be inspected M, and its receiving surface, which is the vibration surface, is a concave surface 112a having a certain diameter and formed with a predetermined radius of curvature. This concave surface 112a receives ultrasonic waves that have passed through the object to be inspected M, converts the received ultrasonic waves into electrical signals, and transmits these electrical signals to the driving unit 12.

[0028] The driving unit 12 applies a voltage to the transmitting-side focused ultrasonic probe 111 to generate ultrasonic waves, receives an electric signal transmitted from the receiving-side focused ultrasonic probe 112, and transmits the received electric signal to the control unit 13. The driving unit 12 may also include a moving means for moving the focused ultrasonic probe 11 or the inspection object M in the horizontal or vertical direction.

[0029] The control unit 13 controls the driving unit 12 to perform various controls such as generating ultrasonic waves, moving the focused ultrasonic probe 11 or the object to be inspected M to scan the object to be inspected M, and adjusting the distance between the focused ultrasonic probe 11 and the object to be inspected M.

[0030] Furthermore, the control unit 13 receives an electric signal from the driving unit 12, and generates an inspection result image indicating the presence or absence of defects in the inspection object M based on this electric signal, and displays it on a display means such as a monitor.

[0031] FIG. 2 is a diagram illustrating the functional configuration of the calculation unit of the ultrasonic inspection system according to one embodiment of the present invention. The calculation unit 20 includes a probe specification information acquisition means 21, an inspection environment information acquisition means 22, a predetermined range definition means 23, a focal position estimation means 24, and a distance determination means 25, and generates distance information indicating the optimum distance between the focused ultrasonic probe 11 and the inspection object M, and transmits this distance information to the control unit 13. In the description of this embodiment, the calculation unit 20 is described as a device separate from the ultrasonic inspection device 10, but this is not limiting, and the ultrasonic inspection device 10 may include the calculation unit 20. The ultrasonic inspection method of the present invention is a method mainly executed by the calculation unit 20.

[0032] Based on this distance information, the control unit 13 controls the drive unit 12 to move the focused ultrasonic probe 11 or the object to be inspected M in a direction closer to or farther away from each other, thereby enabling ultrasonic inspection to be performed at a position where the inspection accuracy is higher (a position where the resolution and clarity of the inspection result image are higher).

[0033] FIG. 3 is a diagram illustrating information acquired by a calculation unit of an ultrasonic inspection system according to an embodiment of the present invention. The probe specification information acquiring means 21 (see FIG. 2) acquires, as the probe specification information, information indicating the specifications of the concave surface of the focused ultrasonic probe 11. Specifically, the probe specification information acquiring means 21 accepts, as the probe specification information, information indicating the probe curvature R of the concave surface 111a (see FIG. 1) of the transmitting-side focused ultrasonic probe 111, the probe diameter D, and the probe height y at the depth focus (see FIG. 4 described later), for example, based on the operation of an input means (e.g., a keyboard, a touch panel, etc.) by a user, and stores the information in a storage means. Note that the probe specification information acquiring means 21 may read out and acquire the probe specification information stored in advance in a storage means. In addition, the probe specification information acquisition means 21 may make the probe specification information of the concave surface 111a of the transmitting side focused ultrasound probe 111 common to that of the concave surface 112a of the receiving side focused ultrasound probe 112, or may receive and store the probe specification information of the concave surface 112a separately from the concave surface 111a.

[0034] The inspection environment information acquiring means 22 (see FIG. 2) acquires, as the inspection environment information, information on the environment of the route along which ultrasonic waves propagate in an ultrasonic inspection. Specifically, the inspection environment information acquiring means 22 receives, as the inspection environment information, information indicating the sound speed c1, which is the shear wave sound speed of a medium through which ultrasonic waves transmitted from the transmitting-side focused ultrasonic probe 111 first propagate (e.g., air: "medium 1" in FIG. 3), and the sound speed c2, which is the shear wave sound speed of a medium through which the ultrasonic waves subsequently propagate (inspection object M (e.g., CFRP (Carbon Fiber Reinforced Plastics), acrylic, etc.): "medium 2" in FIG. 3), based on, for example, a user's operation of an input means, and stores the information in a storage means. Note that the inspection environment information acquiring means 22 may read out and acquire inspection environment information previously stored in a storage means.

[0035] FIG. 4 is a diagram illustrating the processing performed by the calculation unit of the ultrasonic inspection system according to one embodiment of the present invention. The predetermined range defining means 23 (see FIG. 2) defines a predetermined range of the entire range viewed from the direction of the radius of curvature of the concave surface 111a (see FIG. 1) of the transmission-side focused ultrasonic probe 111. Specifically, the predetermined range defining means 23 defines a diameter dr of a circular range centered on the center C of the concave surface 111a as the predetermined range. The predetermined range defining means 23 may also define multiple diameters dr that increase by a predetermined amount (for example, 1 mm) (for example, dr=1 mm, dr=2 mm, dr=3 mm, etc.). The predetermined range defining means 23 may define the predetermined range based on the operation of an input means by a user, or may read and acquire a predetermined range that is stored in advance in a storage means.

[0036] FIG. 5 is a diagram showing an example of a processing result by the focal position estimation means of the calculation unit in the ultrasonic inspection system according to one embodiment of the present invention. The focal position estimation means 24 (see FIG. 2) calculates a depth position from the surface of the object to be inspected at the central axis C ("inspection object focal depth d" shown in FIG. 5) based on the distance from the position where the propagation route of the ultrasonic waves extending from the end of a predetermined range (the range of diameter dr shown in FIG. 4) in a direction perpendicular to the concave surface 111a of the transmitting-side focused ultrasonic probe 111 reaches the surface of the object to be inspected to the central axis C of the concave surface 111a ("lateral distance from end to incident point x1" shown in FIG. 5) and the refraction at the shear wave sound velocity according to the material of the object to be inspected ("refraction angle" shown in FIG. 5), and estimates the depth position as the focal position.

[0037] In detail, the focal position estimation means 24 calculates the focal depth d of the object to be inspected for each predetermined range (effective probe diameter dr in FIG. 5) defined by the predetermined range definition means 23 based on the probe specification information acquired by the probe specification information acquisition means 21 (probe curvature R, probe diameter D, probe height y at the depth focus, etc. shown in FIG. 4) and the inspection environment information acquired by the inspection environment information acquisition means 22 (sound speed c1, which is medium 1 sound speed c1 and medium 2 sound speed c2 shown in FIG. 4).

[0038] Specifically, the focal position estimation means 24 calculates the aperture angle, refraction angle, actual diameter arrow height, probe height at actual diameter, horizontal distance x1 from the end to the incident point, horizontal refraction distance x2, and focal depth d of the object to be inspected. The aperture angle is calculated by dividing the value obtained by dividing the predetermined range (actual probe diameter dr) by half by the probe curvature R, converting the value to the arcsine of the converted value into degrees, and then doubling this angle. The refraction angle is an example of a numerical representation of the refraction at the shear wave sound velocity depending on the material of the object being inspected. The angle of refraction is calculated by dividing the opening angle by 2, converting it to radians, calculating the sine of the converted value, multiplying this sine by the sound velocity in medium 2, c2, divided by the sound velocity in medium 1, c1, and then calculating the inverse sine of this multiplication, converting it to degrees. The actual diameter arrow height is calculated by calculating the cosine of the value obtained by converting the value of the aperture angle halved into radians, subtracting this cosine value from 1, and multiplying the result by the probe curvature R. Note that in this embodiment, in the example shown in Fig. 4, for example, when the actual diameter is D, the "actual diameter arrow height" is the dimension from the intersection P3 of the chord connecting P1 and P2 with the central axis C to the position P4 through which the center position (central axis C) of the concave surface 111a passes. The probe height at the real diameter is the value obtained by subtracting the real diameter arrow height from the probe height y at the depth focus. The horizontal distance x1 from the end to the incident point is the tangent of the value obtained by converting the value of the aperture angle halved into radians and multiplying it by the height of the probe at the effective diameter. The horizontal distance x1 from the end to the incident point is an example of the distance from the position where the ultrasonic propagation route extending from the end of a specified range in a direction perpendicular to the concave surface reaches the surface of the object to be inspected to the central axis of the concave surface. The horizontal refraction distance x2 is a value obtained by subtracting the horizontal distance x1 from the end to the incident point from the value obtained by halving the actual diameter dr of the probe. The focal depth d of the object to be inspected is the horizontal refraction distance x2 divided by the tangent of the refraction angle converted to radians. The focal depth d of the object to be inspected is an example of the depth position from the surface of the object to be inspected on the central axis.

[0039] Returning to FIG. 2, the distance determining means 25 determines the distance (probe height at the effective diameter in FIG. 5) between the transmitting focused ultrasonic probe 111 and the object M (see FIG. 4) based on the focal position estimated by the focal position estimating means 24 (the focal depth d of the object M in FIG. 5).

[0040] In detail, the distance determining means 25 determines the distance between the transmission-side focused ultrasonic probe 111 and the object of inspection M (see FIG. 4) based on the position where the focal positions (the object of inspection focal depth d in FIG. 5) are densely packed among a plurality of focal positions. Specifically, for example, in the example shown in FIG. 5, the object of inspection focal depth d for the probe actual diameter dr "4" to "6" is "2.37···" to "2.31···", which is relatively densely packed compared to other parts. In such a case, the distance determining means 25 determines the distance (the probe height at the actual diameter in FIG. 5) between the transmission-side focused ultrasonic probe 111 and the object of inspection M (see FIG. 4) to be, for example, 29.9 mm, and stores it in the storage means.

[0041] The distance determining means 25 transmits distance information indicating the determined distance between the transmission-side focused ultrasonic probe 111 and the inspection object M (see FIG. 4) to the control unit 13. Note that the distance determining means 25 may acquire a plurality of inspection object focal depths d estimated by the focal position estimating means 24, extract a value that is the center point of a dense portion by, for example, AI (Artificial Intelligence), and determine this value as the distance between the transmission-side focused ultrasonic probe 111 and the inspection object M. Also, the distance determining means 25 may determine the distance between the transmission-side focused ultrasonic probe 111 and the inspection object M based on the user's operation of the input means.

[0042] FIG. 6 is a diagram illustrating processing by the distance determination means of the calculation unit in the ultrasonic inspection system according to one embodiment of the present invention. Further, the distance determination means 25 determines the distance y2 between the receiving focused ultrasonic probe 112 and the object of inspection M based on the determined distance y1 between the transmitting focused ultrasonic probe 111 and the object of inspection M, and stores it in the storage means.

[0043] In detail, the distance determining means 25 determines the distance y2 from the receiving focused ultrasonic probe 112 to the surface of the object M to be greater than the distance y1 from the transmitting focused ultrasonic probe 111 to the surface of the object M in order to reduce the influence of multiple reflection signals within the object M.

[0044] 6, at position P1 of the receiving-side focused ultrasonic probe 112, the distance y2 from the receiving-side focused ultrasonic probe 112 to the surface of the object of inspection M is the same as the distance y1 from the transmitting-side focused ultrasonic probe 111 to the surface of the object of inspection M. On the other hand, at position P2 of the receiving-side focused ultrasonic probe 112, the distance y2 from the receiving-side focused ultrasonic probe 112 to the surface of the object of inspection M is greater than the distance y1 from the transmitting-side focused ultrasonic probe 111 to the surface of the object of inspection M.

[0045] Here, in the ultrasonic inspection, ultrasonic waves may undergo multiple reflections below an internal defect Mf of the inspection object M, and the multiple-reflected ultrasonic waves mr may propagate to the receiving-side focused ultrasonic probe 112 side. In such a case, if the receiving-side focused ultrasonic probe 112 is at position P1, the ultrasonic wave mr is received by the receiving-side focused ultrasonic probe 112, and if the receiving-side focused ultrasonic probe 112 is at position P2, the ultrasonic wave mr is not received by the receiving-side focused ultrasonic probe 112.

[0046] [Experimental Example] Next, an experimental example relating to the ultrasonic inspection system according to one embodiment of the present invention will be described. FIG. 7 is a diagram illustrating a test specimen used as an object to be inspected in the experimental example. In the experimental example described below, the test piece as the inspection object M is an acrylic plate with a thickness of 5 mm, and multiple holes f with a diameter of 2 mm are formed in the center in the thickness direction. The inspection object M (test piece) has multiple holes f with two holes spaced 1 mm apart, two holes spaced 2 mm apart, two holes spaced 3 mm apart, and two holes spaced 4 mm apart.

[0047] In the experimental example described below, the focused ultrasonic probe 11 has a diameter D of 20 mm and a curvature R of 40 mm (32 mm at the focal position). (Experimental Example 1) Fig. 8 is a diagram for explaining Experimental Example 1. Fig. 8(a) is a diagram showing the positional relationship between the inspection object (test piece), the transmitting-side focused ultrasonic probe, and the receiving-side focused ultrasonic probe in Experimental Example 1. Fig. 8(b) is a diagram showing an inspection result image in Experimental Example 1.

[0048] In Experimental Example 1, the influence of refraction at the shear wave sound velocity depending on the material of the inspection object and the influence of multiple reflection signals within the inspection object M are not taken into consideration. 8(a), in Experimental Example 1, the centers of the curvature radii of the transmission-side focused ultrasonic probe 111 and the reception-side focused ultrasonic probe 112 were placed at the center in the thickness direction of the inspection object M (test piece). Specifically, the distance y1 from the transmission-side focused ultrasonic probe 111 to the surface of the inspection object M was 35.5 mm, and the distance y2 from the reception-side focused ultrasonic probe 112 to the surface of the inspection object M was also 35.5 mm.

[0049] As shown in Figure 8(b), Experimental Example 1 did not take into account the effects of refraction and multiple reflection signals, resulting in reduced resolution and sensitivity, and the defect area (hole f shown in Figure 7) displayed with the darkest shading becoming unclear in the inspection result image. Furthermore, in Experimental Example 1, the sensitivity was reduced by 14.1 dB (approximately 80%) compared to Experimental Example 3 (see Figure 10), which will be described later and which takes into account the effects of refraction and multiple reflection signals.

[0050] (Experimental Example 2) 9A and 9B are diagrams for explaining Experimental Example 2. Fig. 9A is a diagram showing the positional relationship between the inspection object (test piece), the transmitting-side focused ultrasonic probe, and the receiving-side focused ultrasonic probe in Experimental Example 2. Fig. 9B is a diagram showing an inspection result image in Experimental Example 2.

[0051] In Experimental Example 2, refraction at the shear wave sound velocity depending on the material of the object to be inspected is taken into consideration, but the influence of multiple reflection signals within the object to be inspected M is not taken into consideration. 9(a), in Experimental Example 2, the distance y1 between the transmission-side focused ultrasonic probe 111 and the inspection object M (test object) was determined so that the refracted focus of the ultrasonic waves transmitted from the transmission-side focused ultrasonic probe 111 was focused at the center in the thickness direction of the inspection object M (test object). Also, in Experimental Example 2, the distance y2 between the reception-side focused ultrasonic probe 112 and the surface of the inspection object M was set to the same as the distance y1. Specifically, the distance y1 between the transmission-side focused ultrasonic probe 111 and the surface of the inspection object M was 18 mm, and the distance y2 between the reception-side focused ultrasonic probe 112 and the surface of the inspection object M was also 18 mm.

[0052] As shown in Figure 9(b), in Experimental Example 2, the effect of refraction is taken into account, and therefore the resolution and sensitivity are improved compared to Experimental Example 1, which does not take the effect of refraction into account, and the defect part (hole f shown in Figure 7) displayed with the darkest shading in the inspection result image is clearer. On the other hand, in Experimental Example 2, the influence of the multiple reflection signals was not taken into consideration, and therefore a false image was generated in the inspection result image due to the influence of the multiple reflection signals. Specifically, compared to Experimental Example 3 (see FIG. 10), which will be described later and which takes the influence of the multiple reflection signals into consideration, the inspection result image has a wider area of ​​lighter shading around the defect part (hole f shown in FIG. 7) that is displayed with the darkest shading, and the clarity of the defect part (hole f shown in FIG. 7) that is displayed with the darkest shading is reduced.

[0053] (Experimental Example 3) Fig. 10 is a diagram illustrating Experimental Example 3. Fig. 10(a) is a diagram illustrating the positional relationship between the inspection object (test piece), the transmitting-side focused ultrasonic probe, and the receiving-side focused ultrasonic probe in Experimental Example 2. Fig. 10(b) is a diagram illustrating an inspection result image in Experimental Example 3.

[0054] In Experimental Example 3, the influence of refraction at the shear wave sound velocity depending on the material of the inspection object and the influence of multiple reflection signals within the inspection object M are taken into consideration. 10(a), in Experimental Example 3, the distance y1 between the transmission-side focused ultrasonic probe 111 and the inspection object M (test object) was determined so that the refracted focus of the ultrasonic waves transmitted from the transmission-side focused ultrasonic probe 111 was concentrated at the center in the thickness direction of the inspection object M (test object). Also, in Experimental Example 3, the distance y2 between the reception-side focused ultrasonic probe 112 and the surface of the inspection object M was determined to be larger than the distance y1 between the transmission-side focused ultrasonic probe 111 and the surface of the inspection object M in order to reduce the influence of multiple reflection signals within the inspection object M. Specifically, the distance y1 between the transmission-side focused ultrasonic probe 111 and the surface of the inspection object M was 18 mm, and the distance y2 between the reception-side focused ultrasonic probe 112 and the surface of the inspection object M was 30 mm.

[0055] As shown in Figure 10(b), in Experimental Example 3, the influence of refraction and multiple reflection signals within the object to be inspected M is taken into consideration, so the resolution and sensitivity are improved compared to Experimental Examples 1 and 2 above, and the defect part (hole f shown in Figure 7) displayed with the darkest shading in the inspection result image is clearer.

[0056] The functional configuration of the present system described above is merely an example, and one functional block (database and functional processing unit) may be divided, or multiple functional blocks may be combined into one functional block. Each functional processing unit is realized by a central processing unit (CPU) built into the device reading a computer program (e.g., core software or an application that causes the CPU to execute the various processes described above) stored in a storage device (storage unit) such as a read-only memory (ROM), flash memory, solid-state drive (SSD), or hard disk, and executing the computer program. In other words, each functional processing means is realized by the computer program reading and writing necessary data such as tables from a database (DB) stored in the storage device or a storage area in memory, and, in some cases, controlling related hardware (e.g., an input / output device, a display device, or a communication interface device).

[0057] As described above, according to the ultrasonic inspection system 1 of this embodiment and the ultrasonic inspection method executed by the ultrasonic inspection system 1, the propagation route of the ultrasonic waves extending in a direction perpendicular to the concave surface 111a from the end of a predetermined range (the range of diameter dr shown in FIG. 4) of the entire range viewed from the curvature radius direction of the concave surface 111a of the transmission-side focused ultrasonic probe 111 reaches the surface of the inspection object M, and the depth position on the central axis C from the surface of the inspection object M is calculated based on the distance to the central axis C of the concave surface 111a and the refraction angle depending on the material of the inspection object M, and the depth position is estimated as the focal position, and the distance between the transmission-side focused ultrasonic probe 111 and the inspection object M is determined based on this focal position. That is, the focal position of the ultrasonic waves transmitted from the concave surface 111a is estimated based on the propagation direction of the ultrasonic waves in the inspection object M, taking into account the refraction of the ultrasonic waves depending on the material of the inspection object M. Therefore, by estimating the focal position taking into account the refraction of ultrasonic waves within the object to be inspected, the accuracy of the inspection can be improved.

[0058] Moreover, according to this embodiment, a plurality of predetermined ranges (ranges of diameter dr shown in FIG. 4) having different sizes are defined, and the focal position is estimated for each of these predetermined ranges, and the distance between the transmitting-side focused ultrasonic probe 111 and the object to be inspected M is determined based on the position where these plurality of focal positions are concentrated. This makes it possible to further improve the accuracy of the inspection.

[0059] Furthermore, according to this embodiment, by making the distance between the receiving-side focused ultrasonic probe 112 and the object of inspection M larger than the distance between the transmitting-side focused ultrasonic probe 111 and the object of inspection M, the multiply-reflected ultrasonic waves propagate outside the receiving-side focused ultrasonic probe 112, so that it is possible to avoid the receiving-side focused ultrasonic probe 112 receiving the multiply-reflected ultrasonic waves. This makes it possible to prevent the occurrence of false images in the images obtained by inspection that indicate the presence or absence of defects, which would reduce the sense of resolution and clarity, thereby further improving the accuracy of the inspection.

[0060] The present invention is not limited to the ultrasonic inspection method and ultrasonic inspection system of the above-described embodiment. [Explanation of symbols]

[0061] 1. Ultrasonic inspection system 10 Ultrasonic inspection equipment 11 Focused ultrasound probe 12 Drive unit 13 Control Unit 20 Calculation section 21. Probe specification information acquisition means 22. Means for obtaining inspection environment information 23 Predetermined range definition means 24 Focus position estimation means 25 Distance determination means 111 Transmitting focused ultrasound probe 111a concave 112 Receiving focused ultrasound probe 112a concave

Claims

1. An ultrasonic inspection method for inspecting the inside of an object to be inspected by ultrasonic waves transmitted from a concave surface of a focused ultrasonic probe, comprising: defining a predetermined range within the entire range as viewed from the direction of the radius of curvature of the concave surface; Based on the distance from the position where the propagation route of the ultrasonic wave extending from the end of the predetermined range in a direction perpendicular to the concave surface reaches the surface of the object to the central axis of the concave surface and the refraction at the shear wave sound velocity according to the material of the object, calculating a depth position from the surface of the object to be inspected on the central axis, and estimating the depth position as a focal position; an ultrasonic inspection method, characterized in that a distance between the focused ultrasonic probe and the object to be inspected is determined based on the focal position;

2. defining a plurality of the predetermined ranges having mutually different sizes; Estimating the focus position for each of the plurality of predetermined ranges; 2. The ultrasonic inspection method according to claim 1, wherein the distance between the focused ultrasonic probe and the object to be inspected is determined based on the position where the focus positions are densely located among the plurality of focus positions.

3. An ultrasonic inspection system for inspecting the inside of an object to be inspected by ultrasonic waves transmitted from a concave surface of a focused ultrasonic probe, comprising: a predetermined range defining means for defining a predetermined range within the entire range as viewed from the direction of the radius of curvature of the concave surface; a focal position estimation means for calculating a depth position from the surface of the object to be inspected on the central axis based on a distance from a position where a propagation route of an ultrasonic wave extending from an end of the predetermined range in a direction perpendicular to the concave surface reaches the surface of the object to the central axis of the concave surface and based on refraction at a shear wave sound velocity according to the material of the object to be inspected, and estimating the depth position as a focal position; and a distance determining means for determining a distance between the focused ultrasonic probe and the object to be inspected based on the focal position.

4. The focused ultrasound probe includes a transmitting focused ultrasound probe that transmits ultrasound waves and a receiving focused ultrasound probe that receives ultrasound waves, the transmitting focused ultrasonic probe is disposed on one surface side of the object to be inspected, The receiving side focused ultrasound probe comprises: is placed on the other surface side of the inspection object, 4. The ultrasonic inspection system according to claim 3, wherein the distance to the object to be inspected is greater than the distance between the transmitting focused ultrasonic probe and the object to be inspected in order to reduce the influence of multiple reflection signals within the object to be inspected.

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