JPH073410B2 - Ultrasonic bevel flaw detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a method for oblique angle flaw detection of a round rod-shaped or tubular test body by ultrasonic waves.

[Conventional technology]

As is well known, typical waves of ultrasonic waves used for flaw detection in metal materials include longitudinal waves and transverse waves. Conventionally, as a flaw detection method for the surface and surface layer of a round rod-shaped test body, JIS Z-2344 is used. It is well known that the ultrasonic oblique angle flaw detection method using a predetermined transverse wave is widely used.

However, the ultrasonic beam radiated into the round bar test body (hereinafter referred to as the test body) rotates in the test body, and the ultrasonic bevel probe is arranged on the same circumference perpendicular to the test body axis. It is better that the probe itself that radiates ultrasonic waves and ultrasonic waves is also incident as an interfering echo by issuing "Ultrasonic test technology" on February 25, 1980 (Japan Management Association) [pp.364-367]. This is a known fact.

Therefore, in order to improve inspection efficiency, multiple probes are arranged on the same circumference that is often used for pipe flaw detection, etc., and the probe or test piece is rotated to perform flaw detection over the entire circumference of the test piece. It is difficult to apply it to a round bar specimen because of the disturbing echo propagating in the specimen. The cause of this disturbing echo and the conventional method will be described below.

FIG. 4 is an explanatory view showing a plurality of transducers arranged on the same circumference of the test body and the propagation state of the ultrasonic beam in the test body in that case, and FIG. 5 is the explanatory view shown in FIG. It is a figure which shows the generation condition of the interference echo by the ultrasonic beam which propagates a sound wave beam in the test body on the A scope of a flaw detector.

In Fig. 4, (1) is a transmitter / receiver probe with a refraction angle of 45 ° in the specimen for detecting defects on the surface and surface layer of the specimen, and (3) is a transmitter / receiver probe. Transmitter / receiver probe with a refraction angle of 45 ° in the test body for detecting defects on the surface and surface layer of the test body, which are arranged at opposite positions on the same circumference of the probe (1), (5) is the test body, (6) is a defect on the surface of the test body, (7) is the ultrasonic beam emitted from the transmitter / receiver probe (1), and (9) is the transmitter / receiver probe. The ultrasonic beam emitted from the child (3). In FIG. 5, (a) is an A-scope waveform when the transmitter / receiver probe (1) is individually sent and received, and (b) is a case where only the transmitter / receiver probe (3) is transmitted. A of the disturbing echo from the transmitting / receiving probe (3) received by the transmitting / receiving probe (1) of
Scope waveform, (c) A scope waveform when the transmitter / receiver probe (3) is individually transmitted / received, (d) is transmission when only the transmitter / receiver probe (1) is transmitted. -A scope waveform from the transmitting / receiving probe (1) received by the receiving probe (3), (e) is a defect set in the transmitting / receiving probe (1), (3) This is the timing of the detection gate.

The ultrasonic beam (7) emitted from the transmitting / receiving probe (1) into the test body (5) is reflected on the outer wall of the test body, propagates in the test body, and travels once around the test body. It returns to the transmitting / receiving probe (1). The A-scope waveform in that case is the fifth
It is (a) of a figure. Along with the propagation of the ultrasonic beam in the A scope, the waveform T of the transmission timing, the surface echo (abbreviated as s echo) reflected when the ultrasonic beam was incident on the surface, and the ultrasonic beam made one round in the test body. Echo (below
R1 echo) and a defect echo reflected 3/4 rounds by the surface defect (6) during the propagation process (hereinafter abbreviated as f3 echo)
Is observed.

The ultrasonic beam (9) emitted from the transmitter / receiver probe (3) into the test body (5) is the same as that of the transmitter / receiver probe (1) shown in FIG. 5 (c). An A-scope waveform is obtained. In this case, a defect echo (hereinafter abbreviated as f1 echo) reflected by a quarter of the surface defect (6) can be observed.

Furthermore, when the transmitter / receiver probes (1) and (3) are simultaneously transmitted, the ultrasonic beam (7) emitted from the transmitter / receiver probe (1) into the test body is tested. Interfering echo (hereinafter RB1 / 2) to the transmitting / receiving probe (3) at the time of 1/2 turn around the body
Abbreviated). FIG. 5D is an A scope waveform showing the state. The ultrasonic beam (9) radiated into the test body from the transmitting / receiving probe (3) also similarly produces a disturbing echo as shown in FIG. 5 (b), and the transmitting / receiving probe (1). Appears in. It is observed that the timing of generation of the disturbing echo RB1 / 2 overlaps with the defect echo f1.

By the way, when detecting flaws on a round rod-shaped test body, the defect detection gate has the best detection sensitivity, considering the diffusion of the ultrasonic beam in the test body and setting it near the first incidence of the ultrasonic beam on the outer wall. And is commonly used. Fifth
(E) of the figure shows a gate setting method in a general case. Therefore, as in this example, the defect echo f1 and the disturbing echo RB
When 1/2 overlaps, it becomes impossible to detect fine defects.

[Problems to be solved by the invention]

When the interfering echoes between the probes as described above occur, ultrasonic flaw detection becomes virtually impossible, and multiple transducers are arranged on the same circumference as used for pipe flaw detection. However, it has been impossible to arrange an efficient probe that rotates the probe or the test body and inspects the entire circumference of the test body. Even if multiple probes are placed on the same circumference due to the problem of the probe mounting space, simultaneous transmission is not possible, so the ultrasonic beam emitted from one probe is The transmission method generally called "time-division method" was adopted, in which the signal was sufficiently attenuated by the transmitter and then transmitted from the next probe.
In the “time division method”, the transmission repetition frequency is inevitably lowered and the inspection speed cannot be set high, so it is extremely rarely used in general. Furthermore, since the ultrasonic beam in the test body has a property of spreading considerably, it is difficult to escape from the interfering echo even if the probe is placed at a position where the beam incident point on the outer wall of the test body is shifted. It has been desired to develop a flaw detection method for a round rod-shaped test body.

The present invention has been made to solve such a problem. Even if a plurality of probes are arranged on the same circumference, the disturbing echo and the defective echo are separated, and a high repetition frequency is maintained and the efficiency is improved. The purpose of the present invention is to obtain a flaw detection method for a typical rod-shaped test body.

[Means for solving problems]

The ultrasonic bevel flaw detection method according to the present invention is such that the ultrasonic bevel transducers are arranged at equal intervals on the same circumference perpendicular to the test body axis.
The position at which the beam emitted from the probe into the test body is incident on the outer surface of the test body in the ultrasonic flaw detection method for a round rod-shaped test body in which the probe or the test body is rotated to detect defects in the test body. This is a method in which the probe is placed on the test piece and the test piece is flawed by shifting the transmission timing of the transmitting / receiving probe that is disturbed by the propagation time of the disturbing echo in the test piece.

[Action]

In the present invention, the probe is placed at a position where the beam emitted from the probe into the test body is incident on the outer surface of the test body for the purpose of determining the position where the disturbing echo is generated. The interference echo RB1 and the defective echo f1 can be temporally separated by shifting the transmission timing of the transmitting / receiving probe that is disturbed by the propagation time.

〔Example〕

FIG. 1 is an explanatory view showing a plurality of probes arranged on the same circumference of a test body showing an embodiment of the present invention and a propagation state of an ultrasonic beam in the test body in that case, and FIG. The figure shows the A-scope waveform of the ultrasonic beam when the transmission timing is shifted by the propagation time of the interfering echo RB1 in the test body. Fig. 3 shows the structure of the transmission unit of the flaw detection device for shifting the transmission timing. FIG.

In FIG. 1, (1), (3), (5) to (7),
(9) is exactly the same as the above conventional example. (2)
Is 90 ° on the same circumference of the first transmitting / receiving probe (1)
The second feed with the refraction angle of 45 ° in the test piece, which is placed at the position of, for detecting defects on the surface and surface layer of the test piece.
Receiving probe, (4) is placed at a position of 270 ° on the same circumference of sending and receiving probe (1), and is a test piece for detecting defects on the surface and surface layer of the test piece. The inside refraction angle is 45 °
4th transmitter / receiver probe, (8) is an ultrasonic beam emitted from the transmitter / receiver probe (2), and (10) is emitted from the transmitter / receiver probe (4). It is a generated ultrasonic beam.
In FIG. 2, (a) is the A-scope waveform and flaw detection gate when the transmitter / receiver probe (1) independently transmits / receives, and (b) is the transmitter / receiver probe (2). A-scope waveform of the disturbing echo received by the transmitting / receiving probe (1) when only the transmission timing is shifted for a predetermined time, (c)
Is the A-scope waveform of the interfering echo received by the transmitting / receiving probe (1) when only the transmitting / receiving probe (3) shifts the transmission timing for a predetermined time, and (d) is the transmitting / receiving A scope waveform of the interference echo received by the transmitting / receiving probe (1) when only the transmitting probe (4) shifts the transmission timing for a predetermined time, (e) shows the transmitting / receiving probe (2) A scope waveform and flaw detection gate in the case of independent transmission / reception in which the transmission timing is shifted by a predetermined time, and (f) is transmitted when only the transmission / reception probe (1) transmits. A-scope waveform of the disturbing echo received by the receiving probe (2),
(G) is the A-scope waveform of the disturbing echo received by the transmitting / receiving probe (2) when only the transmitting / receiving probe (3) shifts the transmission timing for a predetermined time, and (h) is A scope waveform of the disturbing echo received by the transmitting / receiving probe (2) when only the transmitting / receiving probe (4) shifts the transmission timing for a predetermined time, (i) is the third transmission・ A scope waveform and flaw detection gate when the receiving probe (3) performs single transmission / reception with the transmission timing shifted for a predetermined time,
(J) is an A-scope waveform of an interference echo received by the transmitting / receiving probe (3) when only the transmitting / receiving probe (1) transmits, (k) is a transmitting / receiving probe A scope waveform of the interference echo received by the transmitting / receiving probe (3) when only the child (2) shifts the transmission timing for a predetermined time,
(1) is the A-scope waveform of the disturbing echo received by the transmitting / receiving probe (3) when only the transmitting / receiving probe (4) shifts the transmission timing for a predetermined time, and (m) is A scope waveform and flaw detection gate when the transmission / reception probe (4) performs independent transmission / reception with the transmission timing shifted for a predetermined time, (n) is only the transmission / reception probe (1) When the transmitter / receiver probe (4) receives the A-scope waveform of the disturbing echo, (o) is the case where only the transmitter / receiver probe (2) shifts the transmission timing for a predetermined time. The A scope waveform of the interfering echo received by the transmitter / receiver probe (4), (p) indicates the transmitter / receiver when only the transmitter / receiver probe (3) shifts the transmission timing for a predetermined time. 3 is an A-scope waveform of an interference echo received by the probe (4).

In the oblique angle flaw detection method using ultrasonic waves configured as described above, the ultrasonic beam (7) emitted from the transmitter / receiver probe (1) into the test body is used as a disturbing echo. Input to the child (2), (3), (4) after the propagation time in the test body represented by the following formula.

In this case, since the refraction angle in the test body is 45 °, assuming that the outer diameter of the test body is D, the ultrasonic beam is transmitted from the transmitting / receiving probe (1) to the transmitting / receiving probe (2). The beam path length 1 of the test body reached by is calculated by the equation (1).

1 = sin (45 °) · D (1) Similarly, the ultrasonic beam path lengths l2 and l3 from the transmitting / receiving probe (1) to the transmitting / receiving probe (3), (4) are It is calculated by the equations (2) and (3).

l2 = 2.1 (2) l3 = 3.1 (3) The propagation time t1 to t3 from 1 to l3 is the transverse wave sound velocity in the test body.
If it is vs, it can be obtained by the expressions (4) to (6).

t1 = 1 / vs… (4) t2 ＝ l2 / vs ＝ 2 ・ t1… (5) t3 ＝ l3 / vs ＝ 3 ・ t1… (6) Transmitting / receiving probes (2), (3) The A scope waveforms when the transmission timing is shifted by t1 to t3 after the transmitting / receiving probe (1) are (e), (i), and
(M). The defect detection gate is installed near the point where the ultrasonic beam first enters the outer wall. In that case, the center of the gate is the time when the ultrasonic beam is reflected by the outer wall defect and returns to the probe. equal. The time tf is (7)
Calculated by the formula.

tf = 2 · 1 / vs = 2 · t1 (7) The echo that enters the transmitting / receiving probe (1) as a disturbing echo is incident on the test body from the transmitting / receiving probe (2). The ultrasonic beam appears at a position around 3/4 round the test body, and the time is equal to t3 from the beam path in the test body. Furthermore, since the transmission of the transmitting / receiving probe (2) is deviated by t1, t3 +
Since t1 = 4 · t1, it overlaps with the disturbing echo R1 that goes around the test body of the transmitter / receiver probe (1), and does not enter the defect detection gate. FIG. 2B shows the A scope having only the disturbing echo in this case.

The interference echo from the transmitting / receiving probe (3) is also 2/4
Although it appears at the place where the transmitter and receiver went around, because the transmission timing is shifted by t2, the disturbing echo is the same as the transmitter / receiver probe (2), and the disturbance echoes around the test body of the transmitter / receiver probe (1). The echo RB1 overlaps and does not enter the defect detection gate.
FIG. 2 (c) shows an A scope having only disturbing echoes in this case.

The interference echo from the transmitting / receiving probe (4) is also 1/4.
Although it appears in the place where the transmitter and receiver went around, because the transmission timing is shifted by t3, the disturbing echo is the same as the transmitter / receiver probe (2) and the disturbance echoed around the test body of the transmitter / receiver probe (1). It overlaps with echo R1 and does not enter the defect detection gate. In this case, the A scope with only the disturbing echo is shown in FIG.
Shown in.

Next, the echo that enters the transmitting / receiving probe (2) as an interfering echo is the place where the ultrasonic beam incident on the test body from the transmitting / receiving probe (1) makes a quarter turn around the test body. The time is equal to t1 from the beam path in the specimen.
Furthermore, since the transmission of the transmitting / receiving probe (2) is delayed by t1, t1−t1 = 0 and the surface when the ultrasonic beam of the transmitting / receiving probe (2) is incident on the surface of the test body. It does not enter the defect detection gate because it overlaps with the echo. FIG. 2 (f) shows an A scope having only disturbing echoes in this case.

The disturbing echo from the transmitter / receiver probe (3) is 3 /
It appears at four laps, and the time is equal to t3 from the beam path in the specimen. However, the transmission timing of the transmitting / receiving probe (3) is delayed by t2 and the transmitting / receiving probe (2)
Since the transmission of the signal is also delayed by t1, t3 + t2-t1 = 4 · t1. Therefore, the interference echo overlaps with the interference echo R1 that has gone around the test body of the transmitter / receiver probe (2) for defect detection. Do not enter the gate. The A scope having only the disturbing echo in this case is shown in FIG.

Interfering echoes from the transmitter / receiver probe (4) also appear in a place that makes 2/4 rounds of the test body, but the transmission timing is t3.
The transmission of the transmitter / receiver probe (2) is delayed by t1 as well, so that the interference echo is the same as the transmitter / receiver probe (3). It does not enter the defect detection gate because it overlaps with the interfering echo R1 that has traveled around the test body. FIG. 2 (h) shows the A scope having only the disturbing echo in this case.

The echo that enters the transmitter / receiver probe (3) as an interfering echo appears at the location where the ultrasonic beam incident on the test body from the transmitter / receiver probe (1) makes 2/4 turns around the test body. ， The time is equal to t2 from the beam path in the specimen. Further, the transmission of the transmitting / receiving probe (3) is delayed by t2, so t2
Since -t2 = 0, the ultrasonic beam of the transmitting / receiving probe (3) overlaps with the surface echo when incident on the surface of the test body and does not enter the defect detection gate. The A scope with only the disturbing echo in this case is shown in (j) of FIG.

The disturbing echo from the transmitting / receiving probe (2) is 1 /
It appears at four laps, and the time is equal to t1 from the beam path in the test body. Further, the transmission of the transmitting / receiving probe (3) is delayed by t2 and the transmission of the transmitting / receiving probe (2) is also delayed by t1. Therefore, t2-t1-t1 = 0 and the transmitting / receiving probe is When the ultrasonic beam of the child (3) is incident on the surface of the specimen, it overlaps with the surface echo and does not enter the defect detection gate. The A scope with only the disturbing echo in this case is shown in (k) of FIG.
Shown in.

The disturbing echo from the transmitter / receiver probe (4) is 3 /
It appears at four laps, and the time is equal to t3 from the beam path in the specimen. However, the transmission timing of the transmitting / receiving probe (3) is delayed by t2 and the transmitting / receiving probe (4)
Is also delayed by t3, resulting in t3 + t3−t2 = 4 · t1, so the interfering echo overlaps with the interfering echo RB1 that has traveled around the test body of the transmitting / receiving probe (3) and the defect detection gate. Does not break into The A scope having only the disturbing echo in this case is shown in (1) of FIG.

The echo that enters the transmitter / receiver probe (4) as an interfering echo appears at the place where the ultrasonic beam incident on the test body from the transmitter / receiver probe (1) makes 3/4 rounds around the test body. , The time is equal to t3 from the beam path in the test body. Furthermore, since the transmission of the transmitting / receiving probe (4) is delayed by t3, t3
Since -t3 = 0, the ultrasonic beam of the transmitting / receiving probe (4) overlaps with the surface echo when it enters the surface of the test body and does not enter the defect detection gate. The A scope having only the disturbing echo in this case is shown in (n) of FIG.

Interfering echoes from the transmitter / receiver probe (2) are 2 /
It appears at four laps, and the time is equal to t2 from the beam path in the test body. Further, the transmission of the transmission / reception probe (4) is delayed by t3 and the transmission of the transmission / reception probe (2) is also t1.
Because of the delay, t2 + t1-t3 = 0 and the ultrasonic beam of the transmitting / receiving probe (4) overlaps with the surface echo when it enters the surface of the test body and does not enter the defect detection gate.
The A scope having only the disturbing echo in this case is shown in (o) of FIG.

The disturbing echo from the transmitting / receiving probe (3) is 1 /
It appears at four laps, and the time is equal to t1 from the beam path in the test body. Furthermore, the transmission of the transmitting / receiving probe (4) is delayed by t3 and the transmission of the transmitting / receiving probe (3) is also t2.
Because of the delay, t1 + t2-t3 = 0 and the ultrasonic beam of the transmitting / receiving probe (4) overlaps with the surface echo when it enters the surface of the test body and does not enter the defect detection gate.
In this case, the A scope with only the disturbing echo is set to the first (p)
Shown in.

From the above, it can be proved that the flaw detection of the round rod-shaped test body of this configuration can be performed by ignoring the interference echo.

In this example, the case where the refraction angle was set to 45 ° was explained, but even if the refraction angle was changed, the probes were arranged at equal intervals on the circumference and at the incident points on the outer wall of the ultrasonic beam. If this is the case, this method is effective.

FIG. 3 shows the structure of the transmission part of the flaw detector for actually shifting the transmission timing.

(1) to (4) are exactly the same as in FIG. (1
1) is the transmission pulse synchronization timing generator of the flaw detector, (1
2) is a means for inputting the outer diameter of the test body such as a digital switch, (13) is a means for calculating the transmission timing shift amount using a micro computer, (14)-
(17) is a transmission timing generator using, for example, a counter (however, each set value is different), (18)-
Reference numeral (21) denotes a transmission pulse generator that generates a transmission pulse according to the input transmission timing.

The outer diameter value D input from the outer diameter input means (12) including a digital switch and a keyboard is (4)-
The formula (6) is calculated by the transmission timing shift amount calculating means (13) using a micro computer or the like,
It is set in transmission timing shifting means (14) to (17) composed of a counter or the like. The transmission timing shifting means (14) to (17) shifts the time set as the transmission timing signal to the transmission pulse generators (18) to (20) with respect to the transmission synchronization timing and supplies it. The transmission pulse generators (18) to (21) supply transmission pulses to the transmission / reception probes (1) to (4) according to the input transmission timing signal.

By the way, in the above description, the flaw detection method for round bar specimens was described, but in the case of pipe flaw detection where the wall thickness outer diameter ratio exceeds 18%, when the flaw detection of the outer surface and the surface layer part is performed without making the ultrasonic beam incident on the inner surface It goes without saying that it can also be used for.

〔The invention's effect〕

As described above, according to the present invention, the probes are arranged at the positions where the beams emitted from the probe into the test body are incident on the outer surface of the test body. The transmission timing position of the Nth probe is t ₁ , 2t ₁ , 3t ₁ , ... (t ₁ is from the 1st probe to the 2nd probe) with respect to the _1st probe. The interference echo and the defective echo can be separated by shifting the propagation time (with respect to the ultrasonic beam path), and efficient flaw detection can be performed while maintaining a higher repetition frequency than in the past.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an arrangement of a probe and a propagation state of an ultrasonic beam in a test body showing an embodiment of the present invention, and FIG. 2 is a view showing an A-scope waveform of FIG. FIG. 3 is a block diagram of a transmission unit for shifting the transmission timing of the present invention, and FIG.
FIG. 5 is an explanatory view showing the probe arrangement of the conventional example and the propagation state of the ultrasonic beam in the test body, and FIG. 5 is a diagram showing the A scope waveform of the conventional example of FIG. In the figure, (1) to (4) are transmitting / receiving probes. The same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. N number of ultrasonic bevel probes at equal intervals (N is 4 or more) on the same circumference perpendicular to the axis of a rod-shaped or tubular test body.
In the ultrasonic bevel flaw detection method for a round rod-shaped or tubular test body, which is arranged and rotates the probe or the test body to detect defects in the test body, the beam emitted from the probe into the test body is detected. The probes are arranged at positions where they are incident on the outer surface of the test body, and the transmission timing positions of the second to the Nth probes of the probe are set to the first probe, respectively.
An ultrasonic oblique-angle flaw detection method characterized in that t ₁ , 2t ₁ , 3t ₁ , ... (T ₁ is a propagation time with respect to an ultrasonic beam path from the first probe to the second probe) are shifted.