JP2005345138A - Method of ultrasound flaw detection and method of measuring thickness of material quality changed part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasound flaw detection method capable of easily measuring the thickness of a test object and a material quality changed part. <P>SOLUTION: The ultrasound flaw detector 10 detects a flaw on a test object 20 by bringing a transmitter probe T and a receiver probe R into contact with a surface 11 of the test object 20. The transmission probe T transmits outgoing pulse tends to mode convert between transverse waves and longitudinal waves to the test body 20, and the receiver probe R receives the mode converted mode conversion pulse from a bottom surface 13 of the test object 20. The thickness of the test object or the material quality changed part is measured from the distance between the transmission probe T and the receiver probe R, and the path length of the incident bottom surface mode conversion pulse. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrasonic flaw detection method and a material change portion thickness measurement method, and more particularly to an ultrasonic flaw detection method and a material change portion thickness measurement method capable of accurately detecting a carburized layer.

  A method for detecting a carburized layer of a specimen using an ultrasonic flaw detector is described in, for example, Japanese Patent Application Laid-Open No. 2000-321041 (Patent Document 1).

According to Patent Document 1, a transmitting probe and a receiving probe for an ultrasonic oblique flaw detection test are provided at intervals on the outer surface of a metal tube, and a carburized layer is obtained by an ultrasonic V transmission method test. The thickness etc. are measured.
JP 2000-321041 A (paragraph number 0016, etc.)

  In a conventional method for detecting a carburized layer of a specimen using an ultrasonic flaw detector, an ultrasonic V transmission method using a transverse beam of 45 degrees or the like as a main beam is used. In this method, when flaw detection is carried out with increased flaw detection sensitivity, interference pulses such as longitudinal waves, transverse waves, and surface waves that propagate on the flaw detection surface appear even before the bottom surface reflection pulse on the display even when there is no carburized layer. Therefore, it becomes difficult to discriminate the carburized layer, and considerable skill is required to discriminate the carburized layer, and it is also difficult to measure the thickness of the carburized layer. It was also difficult to measure the thickness of the test specimen itself.

  The present invention has been made in view of the problems as described above, and can easily identify a portion where the material has changed, such as a carburized layer of a test body, and can be made of a material such as a test body or a carburized layer. An object of the present invention is to provide an ultrasonic flaw detection method and a material change portion thickness measurement method capable of easily measuring the thickness of the changed portion.

An ultrasonic flaw detection method according to the present invention, in which a transmitting probe and a receiving probe are brought into contact with the surface of a test body to detect the test object, is obtained by using the transmitting probe. A step of emitting a pulse that is likely to cause a transverse / longitudinal wave mode conversion from the surface of the substrate, a step of applying a mode-converted bottom surface mode conversion pulse from the bottom surface of the specimen using a receiving probe, and a receiving probe And a detection step of detecting the thickness of the specimen based on the mode conversion pulse incident on the touch element.
From the surface of the test body, a pulse that easily causes transverse wave longitudinal wave mode conversion is emitted, and the thickness of the test body is detected based on the mode-converted bottom surface mode conversion pulse that is incident from the bottom surface of the test body. Since the bottom mode conversion pulse for measurement can be separated from other interference pulses, the measurement pulse can be easily discriminated.

  As a result, an ultrasonic flaw detection method that can easily measure the thickness of the test body can be provided.

  Preferably, the bottom mode conversion pulse includes an SS conversion pulse, an SL / LS conversion pulse, and an LL conversion pulse, and the detection step includes a step of detecting an SL / LS bottom pulse from the plurality of conversion pulses, and a transmission side A step of detecting a distance between the probe and the receiving probe, a step of detecting a beam path of the SL / LS bottom pulse, a distance between the transmitting side and the receiving probe, and a SL / LS bottom pulse. The thickness of the specimen is detected based on the path length.

  More preferably, the test body has a boundary surface where the material changes, and the receiving probe receives a mode-converted boundary surface conversion pulse from the boundary surface where the material changes, and the detection step Detects the position of the boundary surface where the material changes based on the boundary surface conversion pulse.

  Even if there is a boundary surface with changing material, the bottom mode conversion pulse for measuring the boundary surface can be effectively separated from the disturbing pulse, so the thickness of the material-changed part such as carburized layer is easy. An ultrasonic flaw detection method can be provided.

  The boundary surface where the material changes may exist on the bottom surface side of the test body or may exist on the surface side of the test body.

  Further, the pulse that is likely to cause the transverse wave longitudinal wave mode conversion is a transverse wave pulse emitted at a transverse wave refraction angle of 0 ° to a longitudinal wave critical angle of 33.2 ° with respect to the direction directly below the specimen.

The pulse that is likely to cause the transverse wave / longitudinal wave mode conversion is more preferably a transverse wave pulse emitted at an angle of 30 ° with respect to the direction directly below the specimen.
According to another aspect of the present invention, in the material changing portion thickness measuring method, a pulse for performing mode conversion from a transverse wave to a longitudinal wave is emitted from one side to a test body having a portion where the material changes. A step in which a mode-converted pulse is incident on one side of the specimen from the other end surface of the specimen, and a portion of the specimen in which the internal material is changed using the incident pulse. Find the thickness of the.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a main part of an ultrasonic flaw detector 15 according to an embodiment of the present invention. Referring to FIG. 1, an ultrasonic flaw detector 15 includes a CPU 151 that controls the entire ultrasonic flaw detector 15, a switch 153 that turns on / off the ultrasonic flaw detector 15 connected to the CPU 151 via an interface 152, and a transmission unit 154, a synchronization unit 155, a time axis unit 156, a reception unit 157, a memory unit 159, an amplification unit 160, and a display unit 161.

  The transmission unit 154 is connected to a transmission side probe T described later and outputs a pulse signal. The synchronization unit 155 synchronizes the transmission signal of the transmission unit 154 and the time axis unit 156. The time axis unit 156 measures the time from transmission to reception and converts it to a distance. The receiving unit 157 is connected to the receiving probe R and receives a signal propagated by the receiving probe R. Note that the reception unit 157 includes an A / D conversion unit 158 that converts the received analog signal into a digital signal. The memory unit 159 stores the A / D converted received signal. The amplifying unit 160 amplifies the received signal. The display unit 161 displays the received signal as a flaw detection figure as will be described later.

  FIG. 2 is a schematic diagram for explaining the measurement principle of the ultrasonic flaw detection method according to the present invention. In the present invention, the ultrasonic transmission flaw detection method adopts a V transmission method using a transverse wave longitudinal wave mode conversion pulse instead of a conventional V transmission method using a transverse wave of 45 ° or the like as a main beam. In the transverse wave / longitudinal wave mode conversion pulse, there are transverse wave (S) incidence / longitudinal wave (L) reflection and longitudinal wave (L) incidence / transverse wave (S) reflection. In the following explanation, these are integrated. This is referred to as “SL / LS pulse V transmission method”.

  Referring to FIG. 2, in ultrasonic flaw detector 10 using the SL / LS pulse V transmission method, transmitting probe T and receiving probe R are on surface 11 of specimen 20. It is arranged with a predetermined inter-probe distance 2Y.

  Here, first, a case where the test body 20 is healthy without a material-changed portion such as a carburized layer will be described. In this case, the entire thickness of the test body 20 from the front surface 11 to the bottom surface 13 is measured.

  In the SL / LS pulse V transmission method, ultrasonic waves 16a having a main beam of a transverse wave of 30 ° (indicated by θS in FIG. 3) that is most likely to undergo mode conversion are incident on the test body 20 from the transmitting probe T. When this is done, the receiving side probe R receives the pulse reflected at the bottom surface 13 or the boundary surface and mode-converted to the longitudinal wave 17a.

  The angle of the transverse wave where mode conversion is likely to occur is preferably 30 °, but is not limited to this, and in the case of steel, the transverse wave refraction angle may be within the range of 33.2 °, which is 0 ° to the longitudinal wave critical angle. In this case, mode conversion occurs.

As shown in FIG. 2, at this time, an ultrasonic wave 17b having a longitudinal wave of 66 ° (indicated by θL in FIG. 3) as a main beam is also emitted, and a transverse wave 16b enters the receiving probe R. In FIG. 2, when the transmitting side and receiving side probes T and R are arranged at the positions shown in the figure, other transverse waves received (incident) on the receiving side probe R due to the expansion of the ultrasonic beam. And the longitudinal wave path is also shown. The transverse wave 18 due to the spread of the ultrasonic beam is reflected on the bottom surface, and the longitudinal wave passing through the same path as the transverse wave 18 is also reflected on the bottom surface and propagates. That is, in the arrangement of the transmission side and reception side probes T and R shown in the figure, as the bottom surface pulse on the display unit 161, in addition to the SL / LS pulse, the longitudinal wave incidence longitudinal wave reflection ( LL) pulses and transverse wave incident, transverse wave reflected (SS) pulses appear.

  As indicated by hatched lines 19 in FIG. 2, the supersonic directivity of the main beam from the transmitting probe T is 30 ° transverse wave and 66 ° longitudinal wave is both blunt, and the ultrasonic beam spreads and propagates.

  In the figure, the transverse wave is indicated by a thick line, and the longitudinal wave is indicated by a thin line.

  FIG. 3 is a diagram for explaining the path of each beam shown in FIG. As shown in FIG. 3, there are three types of beam paths. With reference to FIG. 3, a position 21 is a position where a bottom wave pulse of a transverse wave that is emitted by the transverse wave 16 a and reflected by a point 27 on the bottom face 13 of the test body 20 is incident. Hereinafter, this incident pulse is referred to as an SS bottom surface pulse (hereinafter, simply referred to as “SS”).

  The position 22 is a position where the bottom pulse of the longitudinal wave 17 b which is emitted by the transverse wave 16 a and reflected by the point 27 on the bottom surface 13 of the test body 20 is incident, or is emitted by the longitudinal wave 17 a and is on the bottom surface 13 of the test body 20. This is the position where the bottom pulse of the transverse wave 16b reflected by the point 28 enters. Hereinafter, this incident pulse is referred to as a SL / LS bottom pulse (hereinafter, simply referred to as “SL / LS”).

  The position 23 is a position where the bottom surface pulse of the longitudinal wave 17 c that is emitted by the longitudinal wave 17 a and reflected by the point 28 on the bottom surface 13 of the test body 20 is incident. Hereinafter, this incident pulse is referred to as an LL bottom pulse (hereinafter, simply referred to as “LL” in some cases).

  In the SL / LS pulse V transmission method, the thickness of the specimen can be calculated from the geometrical arrangement of the beam path length of each bottom reflection pulse and the distance between the transmitting and receiving probes. This will be specifically described below.

  FIG. 4 is a diagram illustrating a display example of the beam path length and the echo height displayed on the display unit 161. FIG. 4A shows waveforms of SS, SL / LS, and LL bottom pulses when the SL / LS bottom pulse is set to 80% echo height as flaw detection sensitivity. ) Shows a display example when the flaw detection sensitivity is increased based on the data of FIG.

  As can be seen from FIGS. 4A and 4B, at a certain inter-probe distance, LL bottom pulse, SL / LS bottom pulse, and SS bottom pulse appear on the display unit 161 in the order of shorter beam path length. . In FIG. 4B, a peak value appears at a position whose path length is shorter than that of the LL bottom pulse, but this is a disturbing pulse that propagates on the surface 11 of the specimen 20.

  These pulses appear on the display 161 over a wide range even if the inter-probe distance 2Y changes because the ultrasonic beam is expanded and the flaw detection sensitivity is increased.

  FIG. 5 is a diagram showing a result of calculating the relationship between the inter-probe distance 2Y and the beam path length in the test body 20 having the same plate thickness based on the data of FIG. In addition, in FIG. 5, the case where the carburized layer 25 is provided in the bottom face 13 side of the test body 20 is also partially demonstrated. Therefore, in FIG. 5, in addition to the SS bottom surface pulse 31, the SL / LS bottom surface pulse 34, and the LL bottom surface pulse 37, the surface wave pulse 32, the surface transverse wave pulse 33, the SL / LS interface reflection pulse 35, and the SL / LS boundary refraction. Data of the pulse 36 and the surface longitudinal wave pulse 38 are also displayed.

Here, the SL / LS boundary surface reflection pulse 35 refers to a pulse that is reflected at the boundary surface when a boundary layer such as the carburized layer 25 is formed inside the test body 20, and is SL / LS. The boundary refraction pulse 36 is a pulse that is refracted at a boundary surface such as a carburized layer, enters the end surface (bottom surface 13), and is reflected by the bottom surface 13.
In FIG. 5, the ◯ marks indicate the peak positions due to the main beam. FIG. 5 also shows the distance within the probe approach limit. As is clear from the figure, the peak position of the SS bottom surface pulse is within the probe approach limit, so it is actually measured. Can not.

  Referring to FIG. 5, LL bottom surface pulse, SL / LS bottom surface pulse, and SS bottom surface pulse appear on display unit 161 in the shortest order of the beam path at a certain probe distance 2Y. Regardless of 2Y. In addition, disturbing pulses that propagate on the surface 11 appear. Among these interference pulses, as described above, the longitudinal wave propagating on the surface 11 appears at a position where the beam path is shortest, and the positional relationship does not change depending on the distance between the probes. The transverse wave and the surface wave propagating on the surface 11 appear at a position where the beam path is shorter than the SL / LS bottom pulse on the display unit 161 at a position where the distance between the probes is short, but the SL / LS bottom pulse becomes a peak. When the distance between the probes becomes longer than near the position, these disturbing pulses appear at positions where the beam path length is longer than that of the SL / LS bottom pulse.

  This is because if the distance between the probes is larger than the vicinity of the position where the SL / LS bottom surface pulse reaches a peak, boundary pulses such as the SL / LS bottom surface pulse and the carburized layer are transmitted through the surface 11 which is a disturbing pulse, This means that evaluation can be performed without being interfered by surface waves. Therefore, flaw detection with a high S / N ratio is possible, and appearance pulses can be easily identified.

  The SL / LS bottom pulse is discriminated from the beam path between these appearing pulses and the distance 2Y between the probes, and the total thickness up to the bottom face 13 is determined by the geometry of the beam path of the SL / LS bottom pulse and the distance between the probes. Calculate from the target arrangement. Next, this calculation method will be described.

  First, the SL / LS bottom surface pulse is identified from the geometrical arrangement of the probes T and R, SS bottom surface pulse, SL / LS bottom surface pulse, and LL bottom surface pulse.

  Next, the distance between the transmitter and receiver probes T and R and the beam path length of the SL / LS bottom pulse are read, and the thickness is calculated based on the following equation (1) or (2).

Thickness t = {(W) / (1 / cos θS−1 / cos θL)} × (CL / CS) · (1)
t = (2Y) / (tan θS + tan θL) (2)
Where W = beam path
CS = shear wave speed (3230m / s)
CL = longitudinal wave sound speed (5900 m / s)
(2) When a carburized layer is present Next, a case where a carburized layer is present in the specimen 20 will be described. FIG. 6 is a diagram illustrating various pulse paths when the carburized layer 25 is present on the test body 20. Here, the case where the carburized layer 25 exists in the inside of the test body 20 (the bottom surface 13 side in the opposite direction to the probe) is shown. In this case, when the SL / LS pulse V transmission method is used, reflection or refraction due to mode conversion occurs at the boundary, and a pulse having a different path length from the bottom reflection pulse (boundary reflection pulse, boundary refraction pulse, bottom boundary reflection). (Referred to as a pulse, a surface boundary surface reflection pulse) appears on the display portion 161.

  Referring to FIG. 6, the SL / LS pulse 41a emitted from the transmission side probe T is reflected at a point 51 on the boundary surface 45 to become a boundary surface reflection pulse 43a, and is received by the reception side probe R1. The A part of the pulse 41a goes straight through the carburized layer 25 as it is, is reflected at the bottom surface 13 and is reflected as a bottom surface reflection pulse 42b, and is received as the bottom surface peak position of the SL / LS bottom surface pulse by the receiving probe R2. The A part of the SL / LS pulse 41a is refracted at a point 51 on the boundary surface 45, is reflected on the bottom surface 13 as a boundary refraction pulse 44a, and is received by the receiving probe R3.

  A part of the longitudinal wave 42a which is the SL / LS pulse transmitted from the transmission side probe T is reflected at the boundary reflection position 52 of the boundary surface 45, and enters the reception side probe R1 as a transverse wave 41b. That is, the SL / LS interface reflection pulses 41a and 41b are reflected at two points 51 and 52 and enter the reception probe R1 as “interface reflection pulses”.

  The remainder of the longitudinal wave 42a passes through the carburized layer 25 as it is and is reflected by the bottom surface 13, and as an SL / LS bottom surface pulse, as the bottom surface reflected pulse 42b, as a transverse wave 41c, to the receiving side probe R2. Incident as “bottom pulse”.

  Part of the longitudinal wave 42a that has passed through the carburized layer 25 is reflected as a longitudinal wave 42c on the bottom surface 13, refracted at a point 53 on the boundary surface 45, and enters the receiving probe R3. That is, the SL / LS pulses 41a and 42a are refracted at the points 51 and 53 on the boundary surface 45, and enter the receiving probe R3 as “boundary refraction pulses”.

In FIG. 6, as in FIG. 2, the transverse wave is indicated by a thick line and the longitudinal wave is indicated by a thin line. FIG. 7 shows the beam path length and echo displayed on the display unit 161 of each pulse described above. It is a figure which shows the example of a display with height. FIG. 7A shows the boundary surface reflection pulse, FIG. 7B shows the bottom surface pulse, and FIG. 7C shows the boundary refraction pulse. FIG. 7B corresponds to FIG. 4B, and, similar to FIG. 4B, the SL / LS pulse is displayed on the display portion 161 at the probe position where the SL / LS bottom pulse reaches a peak. After adjusting the gain to 80%, the flaw detection sensitivity is increased at the same position, and FIGS. 7A and 7C are obtained.
Referring to FIGS. 7A and 7C, it can be seen that the boundary reflection pulse 62 and the boundary refraction pulse 63 appear at a position shorter than the bottom pulse 61 in the beam path length. From this, the presence or absence of the carburized layer 25 can be determined by the peak position of the SL / LS bottom pulse.

  Further, the thickness of the carburized layer 25 can be calculated in the same manner using the above-described formula (1) or (2).

  Next, a case where a carburized layer is present on the outer surface side of the test body 20 (the surface 11 side on which the probe is placed) will be described.

  An example in which the test body 20 used in FIG. 6 is inverted and the same data as in FIG. 7 is obtained is shown in FIGS. Referring to FIG. 8, in this example, the carburized layer 25 is provided on the side where the probes T and R are provided. The SL / LS pulse (transverse wave 71a, longitudinal wave 72a) from the transmitter probe T is refracted and reflected at points 75 and 76 on the boundary surface 45 and the bottom surface 13, and this is reflected on the probe on the receiver side. Received by children R4 and R5. Also here, the transverse wave is represented by a thick line, and the longitudinal wave is represented by a thin line.

  Referring to FIG. 9, when there is a carburized layer on the outer surface side, the boundary surface reflection pulse does not appear on the display unit 161, but at a position away from the distance between the probes where the SL / LS bottom surface pulse becomes a peak. When the probe is disposed, a boundary refraction pulse that has undergone mode conversion at the boundary of the carburized layer appears on the display unit 161 before the SL / LS bottom surface pulse.

  FIG. 10 is a view corresponding to FIG. 5 when the carburized layer 25 exists on the outer surface side. Basically, it has the same characteristics as in FIG. 5, but the SL / LS interface reflection pulse cannot be measured due to the proximity of the probe on the transmitting side and the receiving side. Therefore, it does not exist as data.

  Next, a method for calculating the thickness of the carburized layer 25 from the above data will be described. The carburization thickness of the carburized layer 25 is calculated on the display unit 161 by changing the inter-probe distance 2Y so that the SL / LS pulse is maximized at the inter-probe distance 2Y that is not interfered by the disturbing pulse. From the beam path length of the bottom pulse and the beam path length of the pulse at the boundary of the carburized layer 25 and the distance 2Y between the probes at that time, the calculation is performed by the same method as the above formulas (1) and (2).

  That is, the refraction angle changes at the inter-probe distance 2Y other than the peak position due to beam expansion. A table is created by calculating the relationship between the beam path length for each inter-probe distance 2Y and the thickness of the specimen 20 when the refraction angles of the longitudinal wave and the transverse wave are sequentially changed. The distance 2Y between the probes and the beam path are read and calculated from the table.

  A specific example of calculating the thickness of the specimen will be described with reference to FIG. FIG. 11 is a diagram showing the relationship between the plate thickness and the beam path length in a state where the inter-probe distance 2Y is kept constant (in this example, 17 mm).

  In FIG. 11, the carburized layer 25 exists on the surface side along with the data of the SS bottom surface pulse 31, the surface wave pulse 32, the SL / LS bottom surface pulse 34, the surface transverse wave pulse 39, the LL bottom surface pulse 37, and the surface longitudinal wave pulse 38. In this case, different pulse incidence data 81 to 86 are shown for each thickness. Here, the incident data 81 is data when the carburized layer thickness is 0.5 mm, the incident data 82 is data when the carburized layer thickness is 1.0 mm, and the incident data 83 is the carburized layer thickness. The incident data 84 is data when the carburized layer thickness is 2.0 mm, and the incident data 85 is data when the carburized layer thickness is 2.5 mm. Data 86 is data when the carburized layer thickness is 3.0 mm.

  Referring to FIG. 11, when carburized layer 25 is provided on the bottom surface 13 side, it is considered that the SL / LS bottom surface pulse is reflected at the position t2 in FIG. Therefore, the detected beam path length is read, and the intersection of the X-direction line of that value and the line of the SL / LS bottom pulse 34 is obtained to obtain the plate thickness. When this thickness is subtracted from the total thickness t1, the thickness of the carburized layer 25 is obtained. That is, the inner surface thickness (thickness when the carburized layer is on the bottom surface 13 side) d1 is obtained by reading the data in the X-axis direction.

  On the other hand, in the case where the carburized layer 25 is provided on the surface 11 side, in FIG. 8, the longitudinal wave 72a advances by t4, the transverse wave 73a mode-converted by the boundary surface 45 advances by t3, is reflected by the bottom surface 13, and advances by t3 + t4. . That is, it proceeds by a transverse wave by t3 and proceeds by a longitudinal wave by t3 + 2 × t4.

  At this time, the thickness of the carburized layer 25 on the surface 11 side is obtained by the following procedure. The total thickness obtained from the bottom pulse is set as the value of the X axis as the plate thickness value, and an axis orthogonal to the value is set. On the axis, the intersection of the SL / LS bottom pulse line is set to zero, and the intersection with the line for each carburization thickness is shown as the thickness of the carburized layer 25. The thickness of the carburized layer 25 is obtained from the intersection with the value of the detected beam path length of the carburized layer 25 on the set axis in the Y-axis direction.

  That is, the outer surface thickness (the thickness when the carburized layer 25 is on the surface 11 side) is shown for each thickness of the carburized layer 25 on the axis orthogonal to the X-axis value of the obtained total thickness. Obtained by reading data with line scales.

Next, the features of the SL / LS pulse V transmission method according to the present invention will be summarized. As described above, the measurement method of the material changing portion such as the carburized layer by the SL / LS pulse V transmission method has the following advantages over the conventional method.
(1) Since the distance between the probes in which the pulse height of the bottom pulse reaches a peak is long, the probe is not limited to the probe approach limit distance even for a thin specimen (about 5 mm). Reflection of the main beam occurs in the distance. Therefore, it is possible to detect flaws with the main beam.

    This will be described by taking as an example a case where the thickness t = 5 mm of the specimen and the probe approach limit distance is 12 mm. Conventionally, the SS pulse peak position when a transverse wave of 45 ° is the main beam is 2Y = (t × tan 45 °) × 2 = 10.0 mm from Equation (1), which is smaller than 12 mm. Therefore, if it is this dimension, it will be in the probe approach limit of a transmission side and a reception side, and the peak pulse of a main beam cannot be detected.

On the other hand, according to this embodiment, the transverse wave 30 ° SL / LS pulse peak position is 2Y = (t × tan 30 °) + (t × tan 66 °) = 14.1 mm.
And larger than 12 mm.

Therefore, it is possible to detect flaws with a main beam even on a thin specimen (about 5 mm) without entering the probe approach limit.
(2) By using the SL / LS pulse, which was considered to be a disturbing pulse in the conventional method, the number of disturbing pulses is reduced, and in the range where the distance between the probes is longer than the position where the peak height of the main beam is at the peak. Further, since the longitudinal wave, the transverse wave, and the surface wave pulse (referred to as the surface longitudinal wave, the surface transverse wave, and the surface wave pulse) propagating on the surface 11 that are other disturbance pulses can be separated from the bottom surface 13 and the boundary surface pulse, the boundary surface pulse is discriminated. Becomes easy.
(3) Boundary surface reflection pulses can be detected with low flaw detection sensitivity compared to conventional methods.

  This is because, as shown in FIGS. 7 and 9, reflection and refraction occur at two locations on the boundary surface, and the angle of incidence on the boundary surface is appropriate.

  In the above-described embodiment, the example of creating a table for detecting the thickness of the carburized layer and referring to the table has been described. However, the present invention is not limited to this, and the processing of this part is converted into software or hardware. May be.

  A specific flowchart of processing contents in the software in this case is shown in FIG. This flowchart may be performed by, for example, the CPU 151 of the ultrasonic flaw detector 15 or a separate personal computer.

  Referring to FIG. 12, first, the total thickness of the specimen 20 is measured (step S11, hereinafter, steps are omitted). At this time, the mode conversion pulse is emitted by the transmission probe T as described above. Then, the bottom surface mode conversion pulse is incident on the receiving probe R (S12). Next, the SL / LS bottom surface pulse is detected (S13), the SL / LS bottom surface pulse peak position is detected (S14), and the inter-probe distance 2Y and the beam path length W are read (S15). The thickness of the specimen 20 is calculated from the above data (S16).

  Next, the received data is amplified by the amplifier 160 to inquire whether or not the thickness of the carburized layer 25 is to be measured. If the carburized layer 25 is not measured, the process is terminated here.

  When measuring the thickness of the carburized layer 25, the display unit 161 inquires whether to measure the surface side of the test body 20 or the bottom side. When the carburized layer 25 on the surface 11 side is measured, the bottom surface mode conversion pulse, the boundary surface reflection pulse, and the boundary surface refraction pulse are received by the receiving probe R (S20), and the distance between the probes is changed ( S21), the distance 2Y between the probes and the beam path W are read, and the thickness of the carburized layer 25 on the bottom surface 13 side is calculated (S23).

  When measuring the thickness of the carburized layer 25 on the bottom surface 13 side, the same processing as that on the surface 11 side is performed to calculate the thickness of the carburized layer 25 on the surface 11 side (S24 to S27).

  It should be noted that a sensor suitable for the detection of the inter-probe distance 2Y is used.

  In the above embodiment, on the surface side and the bottom surface side of the test body, the case where there is a part where the material has changed, such as a carburized layer, has been described as an example. Needless to say, even when the material change layer exists on both the front surface side and the bottom surface side, it can be similarly detected.

  In the above embodiment, the carburized layer is described as an example of the material changed in the specimen, but not limited to this, various material changed layers such as a nitride layer and a clad layer can be detected. It is.

  In the above embodiment, the example in which the presence / absence of the carburized layer, the discrimination of the inner and outer surfaces, and the calculation of the thickness are performed using the boundary surface reflection pulse or the boundary surface refraction pulse related to the SL / LS pulse has been described. First, it is possible to use a boundary reflection pulse or a boundary refraction pulse related to the LL pulse or the SS pulse alone or in combination.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to the thing of embodiment shown in figure. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

1 is a block diagram showing the overall configuration of an ultrasonic flaw detector according to the present invention. It is a schematic diagram for demonstrating the measurement principle of the ultrasonic flaw detector concerning this invention. It is a figure explaining the path | route of each beam shown in FIG. It is a figure which shows the example of a display of a beam path length and echo height. It is a figure which shows the result of having calculated the relationship between the distance between probes and the beam path length in the test body of the same board thickness. It is a figure which shows the path | route of various pulses when a carburized layer exists in a test body. It is a figure which shows the example of a display of a beam path length and echo height when a carburized layer exists in a test body. It is a figure explaining the path | route of each beam when a carburized layer exists in a test body. It is a figure which shows the example of a display of a beam path length and echo height when a carburized layer exists in a test body. It is a figure which shows the result of having calculated the relationship between the distance between probes and the beam path | route distance in the test body of the same board thickness in case a carburized layer exists in a test body. It is a figure which shows the relationship between plate | board thickness and a beam path length in the state which kept the distance between probes constant. It is a flowchart which shows the content of the process sequence at the time of automating one embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Ultrasonic flaw detector, 11 Surface, 13 Bottom, 15 Ultrasonic flaw detector, 16 Transverse wave, 17 Longitudinal wave, 19 Incident wave distribution range, 20 Specimen, 25 Carburized layer, 45 Interface, 151 CPU, 154, Transmission Part, 155 synchronizing part, 156 time axis part, 157 receiving part, 160 amplifying part, 161 display part, T transmitting side probe, R receiving side probe.

Claims (8)

An ultrasonic flaw detection method in which a transmitter probe and a receiver probe are brought into contact with the surface of a test body to detect the test body,
Using the transmitter probe, emitting from the surface of the specimen a pulse that is likely to cause transverse wave longitudinal wave mode conversion; and
Injecting the mode-converted bottom surface mode conversion pulse from the bottom surface of the specimen using the receiving probe, and
And a detection step of detecting a thickness of the specimen based on a mode conversion pulse incident on the receiving probe. The bottom mode conversion pulse includes an SS conversion pulse, an SL / LS conversion pulse, and an LL conversion pulse,
The detecting step includes
Detecting a SL / LS bottom pulse from the plurality of conversion pulses;
Detecting a distance between the transmitter probe and the receiver probe;
Detecting a beam path of the SL / LS bottom pulse;
The ultrasonic flaw detection method according to claim 1, wherein the thickness of the test body is detected based on a distance between a transmitting side and a receiving side probe and a path length of an SL / LS bottom pulse. The test body has a boundary surface in which the material changes,
The receiving probe receives the mode-converted interface conversion pulse from the interface where the material changes,
The ultrasonic flaw detection method according to claim 1, wherein the detecting step detects a position of the boundary surface where the material changes based on the boundary surface conversion pulse. The boundary surface where the material changes exists on the bottom surface side of the specimen, and the step of detecting the position of the boundary surface measures the thickness from the bottom surface of the specimen to the boundary surface. 4. The ultrasonic flaw detection method according to 3. The boundary surface where the material changes exists on the surface side of the specimen, and the step of detecting the position of the boundary surface measures the thickness from the surface of the specimen to the boundary surface. 5. The ultrasonic flaw detection method according to 3 or 4. The pulse which is likely to cause the transverse wave longitudinal wave mode conversion is a transverse wave pulse emitted at a transverse wave refraction angle of 0 ° to a longitudinal wave critical angle of 33.2 ° with respect to a direction directly below the specimen. The ultrasonic flaw detection method according to any one of 1 to 5. 6. The ultrasonic flaw detection method according to claim 1, wherein the pulse that easily causes the transverse wave longitudinal wave mode conversion is a transverse wave pulse that is emitted at an angle of 30 ° with respect to a direction directly below the specimen. A step of emitting a pulse for mode conversion from a transverse wave to a longitudinal wave, from one side thereof, to a test body having a portion where the material changes inside,
Injecting the mode-converted pulse from one end surface of the test body on one side of the test body;
A method for measuring a material change portion thickness, wherein the thickness of a portion of the test body where an internal material has changed is determined using the incident pulse.

Images