JPS6136176B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic flaw detection device, and in particular, it is capable of identifying multiple acoustic discontinuities that are located close to each other within an inspected body even when using a probe with a wide directivity angle. ,
The present invention relates to a flaw detection device suitable for determining each position and size.

Ultrasonic flaw detection using the pulse method has many advantages such as ease of handling and is therefore very popular.

This conventional method will be briefly explained with reference to FIG.

FIGS. 1a to 1c each show the directivity characteristics of the probe, a cross-sectional view of the flaw detection state, and the waveform of the reflected pulse obtained by the flaw detection.

In order to detect an acoustic discontinuity f _j (hereinafter simply referred to as a discontinuity) inherent in the object 3, the first
As shown in Figure b, the refraction angle θ from the ultrasonic transmitter/receiver 1 is
A pulse T is transmitted to the object to be inspected 3 via the probe 2 of
The reflected pulse R _ij from the discontinuity f _j
(The subscripts i and j indicate the discontinuity f when the probe position x _i
j ) is received by the probe 2, which also serves as a wave receiver, and displayed on the cathode ray tube oscilloscope built in the transmitter/receiver 1 as shown by the solid line c in the same figure. The inspector determines the propagation time t _ij of the obtained reflected pulse R _ij
and the pulse peak value p _ij , and read the discontinuity f _j
We are estimating the location and size of. However,
The probe 2 has a directivity characteristic as shown in figure a, that is, a sound field exists in the range of directivity angle +δ ₀ to -δ ₀ , and the strength h of the sound field is the relationship between the deviation angle δ from the center beam. Therefore, in practice, the probe 2 is repeatedly moved back and forth (in the x direction) to observe changes in the peak value of the reflected pulse. Then, when the wave height value reaches the maximum (R _i+1 , _j in figure c), the probe 2 moves so that its center beam just hits the discontinuity part f _j as shown by the broken line in figure b. Therefore, the coordinates (X _j , Y _j ) of the discontinuous portion f _j are determined from the position x _i+1 and the propagation time t _i+1 , _j at this time, and the pulse peak value p _{i+ 1} , the approximate size is estimated from _j .

The above is the conventional method, but the envelope (first
An ultrasonic flaw detection device that automatically reads the maximum value p _i+1 , _j and the corresponding time t _i+1 , _j of the dot-dash line in FIG.

However, even if it is observed by an inspector,
Even if automatic reading is performed as in the method of 85385, a large number of reflected pulses often appear in actual ultrasonic inspection, depending on the shape, material, number of discontinuities, etc. of the object to be inspected. Therefore, many envelopes of pulse height values are drawn at the same time due to the movement of the probe, and when there are many discontinuities in close proximity, the envelopes overlap and it is difficult to read the maximum value. , even if this is possible, it is very difficult to guess which discontinuity is caused. Furthermore, the probe must be moved many times until the maximum value is found, which takes a long time.

As explained above, the conventional method has the disadvantage that it is difficult to identify a case where there is a plurality of discontinuous parts.

The purpose of the present invention is to use complex reflected pulse trains from a large number of discontinuities existing in an object to be inspected as information.
An object of the present invention is to provide an ultrasonic flaw detection device that can accurately and quickly set the coordinates of a discontinuous portion and calculate the maximum value of the peak value of a reflected pulse.

Generally, the coordinates of one discontinuity can be calculated geometrically using the propagation times of two reflected pulses obtained from probes at two fixed points. However, if a plurality of reflected pulses are calculated and these are echoes or noise from other discontinuities, calculating the coordinates is not easy. The present invention creates a combination of pulses by selecting two pulses from the same discontinuity from a reflected pulse train obtained under certain probe conditions and a new reflected pulse train obtained by changing the probe position. However, this method takes into consideration the directional characteristics of the probe, quickly performs position evaluation of multiple discontinuities, and accurately evaluates the positions of multiple discontinuities.

Furthermore, the present invention differs from the conventional method in which the probe is moved until the peak value of the reflected pulse reaches its maximum value and the peak value is read. This device accurately calculates the maximum value from two pulses from the same discontinuity.

FIG. 3 shows an embodiment of the ultrasonic flaw detection device according to the present invention. In the drawings, the same numbers and symbols are used for the same parts as in FIGS. 1 and 2 for explanation.

The reflected pulse R from the ultrasonic transceiver 1 and the probe position x detected by the position detector 4 are each A-
The data is stored in a data memory 7 through D converters 5 and 6. The data memory 7 also stores the refraction angle θ of the probe 2 in use, the directivity h(δ), and the object 3 to be inspected.
A constant C determined by the material of the material and a threshold value H are input from the outside.

In the data memory 7, the probe position x, the propagation time t and peak value p of the reflected pulse obtained at this time are arranged in an orderly table format. The calculation processor 8 draws out the contents of the data memory as appropriate and calculates the contents of the fourth data memory.
Perform the calculations according to the flowchart shown in the figure.

Hereinafter, the present invention shown in FIG. 4 will be described in detail with reference to FIG. 2.

FIG. 2a is a sectional view of the flaw detection state, and FIGS. 2b and 2c are waveform diagrams of the reflected pulse train when the flaw detection conditions are changed. There are many discontinuous parts in the object to be inspected 3 as shown by the black dots in figure a, and the position of the probe ₂ is
Consider the case where reflected pulse trains as shown in b and c in the same figure are obtained when changing from x _i+1 to x i+1. First, in block 100, the pulse train (FIG. 2b) at the probe position _x1 is read out, and in block 101, pulses whose peak value is larger than a predetermined threshold value H are extracted and their number is determined.

Here, the case of pulse R _ij will be explained.
The pulse is located at the discontinuous part f _j (coordinates are (X _j ,
This is a reflected pulse due to Y _j
Orient the position in the following order.

The pulse train in Fig. 2b is from a discontinuous part of the range of directivity angle of the probe 2 (the range surrounded by _{i i} and _{i i} in Fig. 2a), and if we pay attention to the pulse R _ij in this, , the time required for this propagation is t _ij .
Since the propagation velocity in the inspected object 3 is known, the distance l _ij between U _i and f _j is expressed by equation (1).

l _ij =C·t _ij (1) where C is a constant representing the propagation speed. Therefore, R _ij is the radius l _ij centered on the ultrasonic incident point U _i
It is clear that this is a reflected wave from a discontinuity on the arc CD. Therefore, the following equation holds.

(x−x _i ) ² +y ² =l _ij ² (2) Equations (1) and (2) are calculated in blocks 102 and 103, respectively.

Here, in order to locate the position of the discontinuous portion f _j , it is sufficient to move the probe 2 a small distance to obtain a reflected pulse, set up an equation similar to equation (2), and solve the simultaneous equations.

However, since the number of reflected pulses obtained at position x _i+1 is generally large as shown in Figure 2c,
One reflected pulse due to the discontinuous portion f _j must be selected from among these. Therefore, in the present invention, coordinates are determined in the following order using the directional characteristics of the probe (FIG. 1a).

(1) Limitation of the sample period (2) Calculation of coordinates (3) Selection of coordinates based on the strength of the sound field First, the limitation of the sample period will be explained. The distance l _ij is determined from the propagation time t _ij of the reflected pulse R _ij in Figure 2b, and the circular arc CD in Figure 2a with this as the radius
I was able to draw it.

However, if the reflected pulse from f _i also appears when the position x _{i+1 (} actually, the reflected pulse from f _j appears), then Take measures such as choosing a small deviation △x from _i .) As is clear from the drawing, the following can be said.

(1) f _j is on an arc CD with radius l _ij centered on U _i (coordinates are (x _i , 0)).

(2) f _j is an arc whose center is U _i+1 (coordinates are (x _i+1 , 0) and passes through the intersection S ₁ of CD and _i+1 , _i+1)
It's inside the QR.

(3) f _j is centered on U _i+1 , CD, _i+1 , _i+1
It lies outside the arc EF passing through the intersection S ₂ with .

From the above, the reflected wave from the discontinuous part f _j at the position x _i+1 has a time t ₁ corresponding to the distance between U _i+1 and S ₁ , and a time t 1 corresponding to the distance between U _i+1 and S ₂ time _t according to the distance between
It should appear between.

From the above-mentioned matters, t ₁ and t ₂ can be expressed as the following equations (3) and (4). These equations are determined in blocks 104 and 105.

Here, △x=x _i+1 −x _i ………(5) β ₁ = tan (θ+δ ₀ ) ………(6) β ₂ = tan (θ−δ ₀ ) ………(7) The selection of the pulse corresponding to pulse R _ij is then facilitated by selecting the pulse of period t ₁ -t ₂ in block 106 from the plurality of pulses of FIG. 2c. However, since only one pulse does not necessarily exist during this period, further pulse selection is required. In block 107, those whose peak values of R are larger than the threshold value H _{i +1} are extracted, and the number m thereof is counted. For the sake of explanation, it is assumed that R _i+1 , _n (m=1, 2, 3) is observed as a pulse larger than a predetermined threshold value H _i+1 during this period.

Next, a pulse corresponding to R _ij is determined from among R _i+1 and _n . First, read the propagation time t _i+1 , _n (m=1, 2, 3) of each pulse of R _i+1 , _n , and from this, calculate the respective distance l _i+1 in the same way as in equation (1). , _n (m
=1, 2, 3) are determined in block 108.

l _i+1 , _n = C・t _i+1 , _n ......(8) Next, let the center be U _i+1 (coordinates (x _i+1 , 0)) and set the radius l _i+1 , _n The equation of the circle is determined in block 109.

(x−x _i+1 ) ² +y ² =l _i ² ₊₁ , _n ......(9) Three equations (9) hold, and each
In block 110, the simultaneous equations with _equation (2 ₎ representing

Which of these solutions is the true value is determined from the relationship with the strength of the sound field.

The specific steps for selecting the coordinates based on the strength of the sound field are as follows: First, in block 111, the deviation between the coordinates (X _n , Y _n ) and the center beam line _{i i} at the probe position x _i is determined. Obtain the angles δ _i and _n according to equation (10), and similarly calculate the coordinates (X _n , Y _n ) and the probe position X _{i +1}
The central beam line _i+1 , the declination angle from _{i+1 when δ i+1 , n}
is calculated as in equation (11).

δ _i , _n =tan ^-1 (X _n -X _i /Y _n )-θ ......(10) δ _i+1 , _n = tan ^-1 (X _n -x _i+1 /Y _n )-θ... …(
11) (m = 1, 2, 3) The above equation is expressed as follows: If a certain discontinuity exists at the coordinates (X _n , Y _n ), and by moving the probe from position x _i to x _{i +1,} This means that the deviation angle of the coordinates (X _n , Y _n ) from the ultrasound center beam has changed from δ _i , _n to δ _i+1 , _n . From this, it can be said that the peak value of the reflected pulse should theoretically change from h(δ _i , _n ) to h(δ _i+1 , _n ).

On the other hand, the peak values of the reflected pulses are actually measured as p _i , _j and p _i+1 , _n (m=1, 2, 3) as shown in FIGS. 2b and 2c. For each wave height value p _i , _j and p _i+1 , _n , the attenuation effect due to the propagation distance is corrected (so-called
DAC correction) is performed using equation (12) to obtain peak values p^ _i , _j and p^ _i+1 , _n . Block 112 does this.

p^ _i , _j = d(0)/d(l _i , _j ) p _i , _j (12) Here, the function d(l) is a DAC curve.

Next, in block 113, theoretical peak values h(δ _i , _n ) and h(δ _i+1 , _n ) of the reflected pulses are determined from the characteristics of the probe. In block 114, the processes of blocks 108 to 113 are performed for all reflected waves R _i+1 , _n .

Finally, in block 115, a pulse _{with which the difference between the theoretical value and the measured value is the smallest is found from among m pulses, and this pulse is selected from the coordinates (X i ,} Y
_j ). The evaluation function J is expressed as equation (13).

J=〓 _io・(h(δ _i+1 , _n )/h(δ _i , _n )−p
_i+1 , _n /p _i , _j ) ² (13) The pulse corresponding to R _i , _j and its position are determined in the above manner, but the operations from blocks 102 to 115 involve M reflected pulses. The coordinates of all the discontinuous parts present in the object to be inspected 3 are determined and stored. Therefore, the correspondence relationship becomes clear as to which discontinuity portion causes the observed reflected pulse. For example, R _ij and R _i+1 , _n (m=one of 1 to 3) described above are reflected pulses due to the discontinuity f _j .

Next, a method of determining the maximum value of the reflected pulse height value due to the discontinuous portion will be explained. Assume that N _j reflected pulses from the discontinuous portion f _j are obtained by changing the position of the probe. Here, the subscript j means that from the discontinuous portion f _j . Now, if the pulse height value at position x _i is p^ _ij (DAC corrected), this value is the deviation angle δ _ij from the center beam.
This is from when I was alone. Therefore, the value (maximum value p^ _j ) when the deflection angle is zero, that is, the discontinuous portion f _j just hits the center beam, can be estimated from the proportional relationship of equation (14).

p^ _i = h(0)/h(δ _ij ) p^ _ij ………(14
) Similarly to equation (14), for the discontinuous part f _j ,
In order to achieve N _j calculations and increase the reliability of the estimation, it is better to take an averaged value as shown in equation (15).

Equation (14) or (15) is executed in block 120 to determine the maximum value of the reflected wave.

As described above, all the coordinates of the discontinuous part in the object to be inspected can be located, and furthermore, the maximum wave height value of the reflected pulse from these coordinates can be calculated, and the size of the discontinuous part can be estimated.

Note that, as described above, the position and maximum value of the discontinuous portion are determined for the entire object to be inspected.

As described above, according to the present invention, it is possible to quickly and accurately determine the position and evaluate the size of a plurality of discontinuous portions, which was difficult to do with conventional devices.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the conventional ultrasonic flaw detection method, Fig. 2 is an illustration for explaining the principle of the present invention, Fig. 3 is an embodiment of the present invention, and Fig. 4 is a flowchart of the functions of the present invention. It is a line diagram. Explanation of symbols, 1...transmitter/receiver, 2...probe,
3...Test object, T...Transmission pulse, R...Reception pulse, 8...Computer.

Claims (1)

[Claims] 1 Ultrasonic pulses are applied to the body to be inspected using a probe with known directional characteristics, and the position of the acoustic discontinuity within the body is detected based on the reflected pulses from the acoustic discontinuities within the body. In a sonic flaw detector, when one of the two reflected pulse trains obtained at different probe positions is focused on one of the pulse trains at one probe position, the probe position at that time is According to the circular arc whose radius is the distance determined from the center and the propagation time of the pulse, and the ultrasonic pulse propagation area at other probe positions,
The propagation time of the reflected pulse from the acoustic discontinuity on the circular arc is estimated at the other probe position, and the estimated propagation time is estimated among the pulses of the reflected pulse train at the other probe position. Obtain a pulse train that exists in time, obtain the peak value after correcting the distance-amplitude characteristics of these pulses, identify a pulse from the same acoustic discontinuity as the one pulse of interest, and find its position. , from the directional characteristics of the probe, the peak value of the detected pulse, and the angle between the center beam and the center beam of the ultrasonic pulse, calculate the magnitude of the reflected pulse when the center beam of the ultrasonic pulse hits the acoustic discontinuity obtained above. An ultrasonic flaw detection device characterized by determining the size of an acoustic discontinuity by estimation.