JPH0535988B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a distance axis setting device for an ultrasonic flaw detector, which sets a distance axis related to a measurement range, a defect position, etc. in an ultrasonic flaw detector. [Prior Art] Ultrasonic flaw detectors are well known as devices for inspecting the presence or absence of flaws inside an object without destroying the object. This ultrasonic flaw detector will be explained using figures. FIG. 5 is a block diagram of a conventional ultrasonic flaw detector. In the figure, 1 is the object to be inspected, 1f is the object to be inspected 1
Indicates the defects present within. 2 is an ultrasonic probe that emits ultrasonic waves into the object to be inspected 1 and outputs an electric signal proportional to the reflected ultrasonic waves. 3 is an ultrasonic flaw detector which outputs an ultrasonic generation pulse to the ultrasonic probe 2, receives a signal from the ultrasonic probe 2, and displays the waveform of this signal. The ultrasonic flaw detector 3 is composed of the following elements. That is, 4 is a synchronous circuit that generates a signal voltage that temporally regulates the operation of the ultrasonic flaw detector 3, and 5 is a synchronous circuit that outputs pulses for generating ultrasonic waves to the ultrasonic probe 2 based on the signal from the synchronous circuit 4. This is the transmitter. 6'
A receiving section receives signals from the ultrasonic probe 2, and is composed of an attenuation circuit 6a consisting of a combination of voltage dividers made up of resistors, and an amplification circuit 6b'. 7 is a detection circuit for rectifying the signal from the amplifier circuit 6b', and 8 is a vertical amplifier circuit. Reference numeral 9 represents a sweep circuit that generates a triangular wave based on the synchronization signal from the synchronization circuit 4, and reference numeral 10 represents an amplifier circuit that amplifies the triangular wave signal from the sweep circuit 9. 11 is a display unit that displays the signal waveform from the ultrasound probe 2, the horizontal axis is the time axis determined by the triangular wave output from the amplifier circuit 10, and the vertical axis is the vertical axis output from the amplifier circuit 8. It is considered to be the magnitude of the signal. A cathode ray tube is used as the display section 11, and a scale is displayed on its surface. 12 is the object to be inspected 1,
This is a measurement range setting section that sets the range to be inspected (measurement range) from the surface. Reference numeral 13 denotes a delay time setting section that shifts the position of the waveform displayed on the display section 11 in parallel with a sweep start signal delay time. FIG. 6 is a circuit diagram of the sweep circuit shown in FIG. 5. In the figure, 9a is an amplifier, 9r is a variable resistor, 9
c is a variable capacitor. Measurement range setting section 12
Usually consists of a coarse adjustment knob and a fine adjustment knob, and by rotating these knobs, the resistance value of the variable resistor 9r and the capacitance of the variable capacitor 9c are adjusted. Next, an outline of the operation of the conventional ultrasonic flaw detector described above will be explained. When a pulse is output from the transmitter 5 due to the signal voltage from the synchronous circuit 4, the ultrasonic probe 2
is excited by this pulse and emits ultrasonic waves to the object 1 to be inspected. A part of the emitted ultrasonic waves is immediately transmitted to the ultrasonic probe 2 from the surface of the object to be inspected 1.
, and the others propagate within the object to be inspected 1 , reach the bottom of the object to be inspected 1 , where they are reflected and return to the ultrasound probe 2 . On the other hand, if a defect 1f exists in the object to be inspected 1, the ultrasonic waves are also reflected from the defect 1f and return to the ultrasonic probe 2. The ultrasonic waves returned to the ultrasonic probe 2 excites the ultrasonic probe 2 in proportion to its magnitude, and the ultrasonic probe 2 outputs an electric signal corresponding to this. This signal is input to the attenuation circuit 6a, adjusted to a size suitable for processing, and input to the detection circuit 7 via the amplifier circuit 6b'. The detection circuit 7 rectifies the input signal so that the display unit 11 displays a one-sided swing instruction. At this time, noise components mixed in the signal are also removed. The output signal of the detection circuit 7 is input to the display section 11 via the vertical axis amplifier circuit 8, and its magnitude is displayed on the vertical axis of the display section 11. On the other hand, the sweep circuit 9 generates a triangular wave voltage based on the synchronization signal from the synchronization circuit 4, and this voltage passes through the amplifier circuit 10 to the display section 11.
Applied to the deflection electrode of a cathode ray tube (cathode ray tube), it sweeps the electron beam. Due to this sweep and the input signal from the vertical axis amplifier circuit 8, the waveform of the reflected wave returned to the ultrasound probe 2 is displayed on the display section 11. FIG. 7 is a waveform diagram of the displayed reflected waves. In the figure, the horizontal axis represents time, and the vertical axis represents the magnitude of the reflected wave. T is the reflected wave from the surface of the object to be inspected 1, F ₁
is the reflected wave from the defect 1f, and _B1 is the reflected wave from the bottom surface of the object 1 to be inspected. S indicates a scale drawn on the display section 11. A part of the reflected wave reflected from the bottom surface is re-reflected from the surface and returns into the object 1 to be inspected. As a result, the reflected wave from defect 1f
F ₂ , the reflected wave B ₂ from the bottom appears again F ₂ ,
The magnitude of B ₂ is naturally smaller than the magnitude of reflected waves F ₁ and B ₁ . In this way, the reflected wave from the defect 1f and the reflected wave from the bottom surface appear repeatedly while being attenuated. Note that since the sound speed of ultrasonic waves within the object to be inspected 1 is constant, the horizontal axis (time) represents the distance from the surface inside the object to be inspected 1;
The position of the defect 1f can be determined from this waveform diagram. By the way, in general, when inspecting the object to be inspected 1, it is not necessarily necessary to inspect the entire object from the surface to the bottom, and it is often sufficient to inspect a certain depth range from the surface. In this case, it is desirable to display only the range (measurement range) of the waveform, thereby allowing more accurate analysis. Here, a method for setting such a measurement range will be explained. Now, let's assume that the distance from the surface to the bottom of the object to be inspected is 200mm, and the measurement range is 100mm.
Let's consider the case where it is set to mm (within 100 mm from the surface). In this case, a specimen with a thickness of 100 mm made of the same material as the object to be inspected 1 is prepared. Next, when ultrasonic waves are radiated to the specimen, reflected waves T, B ₁ , B ₂ , . . . appear on the display section 11. Therefore, by operating the coarse adjustment knob and fine adjustment knob of the measurement range setting section 12 to expand or reduce the horizontal axis, the reflected wave B 1 is displayed on the scale S _L at the left end of the display section 11, and the reflected wave B ₁ is displayed on the scale S L at the left end of the display section 11. Adjust so that the reflected wave _B2 appears on S _R.
In this case, only the reflected waves B ₁ and B ₂ are displayed on the display unit 11, and the interval between the scales S _L and _SR at both left and right ends corresponds to a position interval of 100 mm.
Next, the knob of the delay time setting section 13 is rotated to move the waveform in parallel to the right, and the reflected wave T is aligned with the scale S _L at the left end. When ultrasonic waves are emitted to the object to be inspected 1 in this state, the measurement range of 100 mm (scale _SR ) from the surface (scale _SL ) will be displayed on the display section 11. [Problems to be Solved by the Invention] As described above, the measurement range in the conventional device is set by preparing a sample having a thickness equal to the measurement range and made of the same material as the object to be inspected 1, and setting the measurement range in the measurement range. Two knobs of setting section 12 and delay time setting section 1
It is extremely troublesome because it is necessary to operate the knobs No. 3 and requires considerable skill to match the reflected waves B ₁ and B ₂ with the scales _SL and _SR during these operations. Furthermore, specimens having the required material and thickness do not always exist; in fact, they often do not exist, and in this case, it is almost impossible to set the measurement range. However, for a material with a certain sound velocity, the values of the resistor 9r and capacitor 9c of the sweep circuit 9 are calculated in advance for each measurement range, and the measurement range is displayed on one knob (for example, a rough adjustment knob) of the measurement range setting section 12. It is also possible to display the speed of sound by calculation in advance on the other knob (for example, the fine adjustment knob) corresponding to the display above, and set the measurement range using both knobs, but the variable capacitor 9
Since c is used, each of the above displays itself becomes a non-linear display, and it is extremely difficult to set the knobs accurately. Therefore, it is almost impossible to accurately set the measurement range. If the measurement range cannot be set accurately, it will not be possible to accurately read the position of the defect. As described above, with the above-mentioned conventional device, accurate setting of the measurement range is extremely troublesome even when a sample is present, and almost impossible when a sample is not present. Ta. In addition to this, even if the measurement range could be set accurately, the following problems would occur. That is, the resistance value of the resistor 9r of the sweep circuit 9, the capacitance of the capacitor 9c,
And the amplification factor of the amplifier circuit 10 changes depending on the temperature. Therefore, when the ambient temperature changes, errors occur even in the accurately set measurement range. This means that the reflected waves are shifted in the horizontal axis direction, making it impossible to accurately determine the position of the defect. The problems in setting the measurement range have been described above, but there are other problems as well. That is, when investigating the position of the reflected wave from the defect 1f using the conventional device, the distance of one scale in the time axis direction of the scale S from the measurement range is calculated, and the number of scales at which the reflected wave is located is calculated. , and then multiplying it by the distance of one scale, which is extremely troublesome. Furthermore, if the reflected wave is located at a position that does not match the scale S (which is often the case), it is necessary to actually measure the position between one scale and perform the necessary calculations. The time required to know the position of the reflected wave becomes even more complicated. After all, the above-mentioned problems arise from the fact that the distance axis is determined by visual measurement, whether in setting the measurement range or in measuring the defect position. An object of the present invention is to solve the above-mentioned problems of the prior art, and to easily and accurately set the time axis related to the measurement range, defect position, etc. on the display section of an ultrasonic flaw detector. Regarding an axis setting device. [Means for Solving the Problems] In order to achieve the above object, the present invention includes a transmitter that outputs a predetermined pulse to an ultrasound probe, and a transmitter that receives a signal from the ultrasound probe. In an ultrasonic flaw detector, the ultrasonic flaw detector is equipped with a receiver that displays the waveform of the signal based on the signal received by the receiver. The thickness of the object to be inspected or an object made of the same material, and the peak value corresponding to the thickness in the memory are stored in the memory sequentially in the order of the addresses in the sampling period, and the inside of the object to be inspected is A sound speed calculation means section is provided for calculating the speed of sound propagating to the sound speed calculation means, and the distance axis calculation means performs calculations regarding the distance axis related to the measurement range, defect position, etc. based on the sound speed calculated by the sound speed calculation means and the sampling period. It is characterized by the following. [Operation] The reflected waves of the ultrasonic waves from the object to be inspected return to the ultrasonic probe, and the ultrasonic probe outputs a signal according to the reflected waves. The receiving section receives this signal, and the output signals from the receiving section are sequentially stored in the memory at a predetermined sampling period. Next, using the thickness of the object to be inspected or an object made of the same material and the address in the memory that stores the peak value corresponding to the thickness, the speed of sound in the object to be inspected is calculated by the sound velocity calculation means. Remember. When setting the distance axis, the distance axis is set based on the stored sound speed and the sampling period. [Example] The present invention will be described below based on the illustrated example. FIG. 1 is a block diagram of an ultrasonic flaw detector according to an embodiment of the present invention. In the figure, parts that are the same as those shown in FIG. 5 are given the same reference numerals, and explanations thereof will be omitted. Ultrasonic flaw detectors sometimes detect and display reflected waves, and sometimes display without detecting them.
The following embodiments are applicable to either case. Therefore, in the following description, an embodiment will be described in which the receiving section 6 is constructed by combining the amplifier 6b' and the detection circuit 7 shown in FIG. 5 as the amplifier circuit 6b, and detection is performed. Reference numeral 21 indicates an ultrasonic flaw detector of this embodiment. This ultrasonic flaw detector 21 is composed of the following elements. That is, 22 is an A/D converter that converts the output signal of the receiver 6 into a digital value;
3 is a waveform memory that stores the values converted by the A/D converter 22, and 24 is an address counter that sequentially specifies each address of the waveform memory 23. 2
Reference numeral 5 denotes a timing circuit, which provides activation signals to the transmitter 5, the A/D converter 22, and the address counter 24, respectively. A crystal oscillator is used for oscillation of this timing circuit 25. 26 is a CPU (central processing unit) that performs necessary calculations and control, and 27 is a RAM (random access memory) that temporarily stores parameters and data for calculations.
memory), 28 stores the processing procedure of the CPU 26
It is ROM (read only memory). 29
3 is a measurement range setting section for inputting a desired measurement range;
0 is a keyboard input section for inputting the thickness of the object to be inspected. 31 is the liquid crystal display section, 32 is the CPU 26
This is a display unit controller that controls the display of the liquid crystal display unit 31 based on data obtained as a result of calculation and control. Next, for the operation of this embodiment when setting the measurement range, refer to the waveform diagram of the reflected wave shown in FIG. 2, the content explanatory diagram of the waveform memory 23 shown in FIG. 3, and the flowchart shown in FIG. 4. I will explain while doing so. First, a desired measurement range l _R (this value is shown on the object to be inspected 1 shown in FIG. 1) is set in the measurement range setting section 29. On the other hand, use a caliper, micrometer, etc. to measure the thickness l _B of the object to be inspected 1 (this value is also shown in the object to be inspected 1 shown in Figure 1) or the thickness l _B of any test piece. The measured value is input using the keyboard input section 30. In this state, from the timing circuit 25 to the transmitter 5
When the trigger signal is output, the transmitter 5 outputs a pulse to the ultrasonic probe 2, and the ultrasonic probe 2 emits ultrasonic waves into the object to be inspected 1. This reflected ultrasound wave is converted into an electrical signal by the ultrasound probe 2, and this signal is received by the receiver 6. The receiving unit 6 outputs the received reflected wave signal as a value suitable for subsequent processing. This output reflected wave signal is sent to the A/D converter 2 at every predetermined sampling period.
2, the converted values are sequentially stored in the waveform memory 23. This memory is stored by the address counter 24 in the waveform memory 23.
This is done by specifying the addresses in sequence.
Sampling of the reflected wave signal and addressing of the waveform memory 23 are executed by a start signal output from the timing circuit 25. Sampling of such a reflected wave signal and storage of its digital value in the waveform memory 23 will be explained with reference to FIGS. 2 and 3. FIG. 2 is a waveform diagram of the reflected wave signal. In the figure, time is plotted on the horizontal axis, and the magnitude (voltage) of the reflected wave signal is plotted on the vertical axis. T and F ₁ indicate the same reflected waves as shown in FIG. In addition, in FIG. 2, only the horizontal axis is extremely enlarged. Next, FIG. 3 is a block diagram of the waveform memory 23. Each block shown in a column represents a data storage section in the waveform memory 23, and the data written in each storage section is
D ₍₀₎ , D ₍₁₎ , ......D _(o-1) , D _(o) , D _(o+1) ...... are reflected waves converted into digital values by the A/D converter 22 This is signal data. These data are expressed as D _(i) in general form. Also, the symbols A _M(0) , A _M(1) , ......A _M(o-1) , A _M(o) , written on the left side of each storage section are
A _M(o+1) ...... indicates the address of the corresponding storage unit. These addresses are expressed as A _M(i) in general form. Now, at time t ₀ shown in FIG. 2, when the timing circuit 25 outputs the activation signal for the A/D converter 22 and the address counter 24, the A/D converter 22 outputs the voltage of the reflected wave T at that time. A/D
The data is converted to obtain data D(0). Further, the address counter 24 specifies address A _{M (0)} of the waveform memory 23. As a result, data D ₍₀₎ is the waveform memory 2
3 is accommodated at address A _M(0) . Then, the time τ _s
At time t ₁ after the elapse of time, when the timing circuit 25 outputs the activation signal to the A/D converter 22 and address counter 24 again, the voltage of the reflected wave T at that time is also converted by the A/D converter 22. Since the address counter 24 specifies the next address A _{M (1) ,} the data D ₍₁₎ is stored in the address A _{M (1)} of the waveform memory 23.
In this case, the time τ _s is the sampling time (e.g.
50ns). Hereinafter, the reflected waves T, F ₁ ,
Data of B ₁ , F ₂ , B _{2 .} . . will be stored in the waveform memory 23. Next, it is determined whether the material of the object to be inspected 1 to be inspected this time is the same as the material of the object to be inspected previously inspected with this ultrasonic flaw detector 21 (step P ₁ shown in FIG. 4), If they are not the same, the CPU 26 reads the thickness l _B previously input using the keyboard input unit 30 (step P ₂ ). Also, among the data stored in the waveform memory 23, search for consecutive large peak values (peak values of reflected waves B ₁ and B ₂ ) excluding the reflected wave T,
The two addresses where the respective peak values are stored are read out (procedure P ₃ ). Of these two addresses, select the address that stores the peak value of reflected wave _B1 .
A _M(b1) and the address where the peak value of the reflected wave B ₂ is stored are expressed as A _M(b2) . Then these addresses, thickness l _B ,
And from the sampling time τ _s, the sound wave v _s in which the ultrasonic wave propagates through the inspected object 1 is determined by the following formula (procedure
_P4 ). v _s = 2l _B / {A _M(b2) −A _M(b1) }×τ _s ………(1) In equation (1), {A _M(b2) −A _M(b1) } is the reflected wave Indicates _the number of addresses that store data between B1 and reflected wave _B2 . These addresses store data every sampling time τ _s , so the time from the appearance of reflected wave B ₁ until the appearance of reflected wave B ₂ is {A _M(b2)
−A _M(b1) }×τ _s . Also, during this time, the ultrasonic wave makes one round trip between the surface and the bottom, and the distance is 2×l _B.
Therefore, the sound speed _vs of the ultrasonic wave can be determined by calculating the above equation (1). The obtained sound speed v _s is RAM
27 at a predetermined location (step P ₅ ). If it is determined in step _P1 that the materials of the current inspected object 1 and the previous inspected object are the same, the sound velocity v _s
are the same value, so steps P ₂ to _{P 5} are performed in the fourth step.
Omitted as shown in the figure. Once the sound speed _vs. is obtained, the measurement range setting section 2
The measurement range l _R set to 9 is read (procedure
_P6 ). Furthermore, the speed of sound stored in RAM27
v _s is read (step P ₇ ). Next, in order to display the measurement range l _R across the entire horizontal direction of the liquid crystal display section 31,
That is, in order to display the reflected wave T on the left end scale of the liquid crystal display section 31 and the position corresponding to the distance l _R on the right end scale, how should the data stored in the waveform memory 23 be retrieved? Whether it is good or not is determined by calculation (step P ₈ ). This calculation will be explained below. The waveform memory 23 stores data of repeated reflected waves equal to or smaller than the reflected wave T, as described above.
However, what is needed is data within the measurement range, and it is sufficient to display the data within the measurement range between the scales at the left and right ends of the liquid crystal display section 31. Generally, when displaying on the liquid crystal display section 31, data for display is stored in a display memory (not shown) provided in the display section controller 32. The address of this display memory is the number of horizontal arrays of liquid crystal dots (for example,
200 pieces). Using this address in general form, A _L(j) (j=0, 1, 2,...
199). If the measurement range is a certain value, the address of this display memory is the number of data stored in the waveform memory 23 within the measurement range (i.e.,
(number of addresses within the measurement range). Therefore, in order to display data within the measurement range between the scales at the left and right ends, the waveform memory 23
The above calculation will be performed to determine how to select addresses within the measurement range at . Here, τ _s : Sampling time l _R : Measurement range, v _s : Sound speed of the ultrasonic wave inside the object to be inspected 1 obtained by calculating equation (1) t : Time until the reflected wave returns ΔA : Measurement range The number of addresses in the waveform memory 23 corresponding to l _R is D _t : the number of liquid crystal dots arranged in the horizontal direction of the liquid crystal display section 31 (or the number of addresses in the display memory), then the reflection at the distance of the measurement range l _R from the surface The time t required for the wave to return is t=2l _R /v _s ......(2) The number of addresses ΔA stored in the waveform memory within this time is ΔA=t/τ _s = 2l _R /τ _s・v _s ………(3) To select an address according to the number of liquid crystal dots D _t (number of addresses in display memory) among the addresses with this number of addresses ΔA, select the address at the ratio of ΔA/D _t It will be a good thing if you do it. That is, the third
Each address A _M(0) of the waveform memory 23 shown in the figure,
A _M(1) , ......A _M(o-1) , A _M(o) , A _M(o+1) , ...... In order to display the measurement range l _R , the i-th address is If selected, the number i is expressed by the following equation. i=ΔA−1/D _t −1×j (4) where j is a positive integer {from 0 to (D _t −1)}. In step _P8 , the calculation of equation (4) is executed. The number i obtained in step _P8 is the address number of the waveform memory, so naturally it must be an integer. Therefore, this number i is converted into an integer by an appropriate means (step P ₉ ). Each address obtained in this way
A _M(i) data is stored in display memory (not shown)
is transferred to each predetermined address A _L(j) (procedure
_P10 ). Next, the liquid crystal display section 31 is driven by the display section controller 32 (step P ₁₁ ), and the data stored in the display memory is sequentially displayed. As a result, all the waveforms of the reflected waves within the measurement range l _R appear on the liquid crystal display section 31 between the scales at both the left and right ends. Here, the processing of steps P ₆ to P ₁₁ in the above procedure will be explained using a specific example. Now, sampling time τ _s , measurement range l _R , sound speed _vs , number of liquid crystal dots D _t
Suppose that is the following value. τ _s = 50 ns (20 MHz) l _R = 200 mm v _s = 5.9 Km/s D _t = 200 points First, the numerical value 200 is input to the measurement range setting section 29, this value is read, and the sound velocity is
5.9×10 ⁶ is read out (procedures P ₆ and P ₇ ). Then,
In step _P8 , the number ΔA of addresses in the waveform memory 23 corresponding to the measurement range of 200 mm is determined from equation (3). ΔA=2×200/50×10 ^-9 ×5.9×10 ⁶ =1355.9 In other words, the address A _M(0) of the waveform memory 23 ~
A _M(1355) stores waveform data within a range of 200mm from the surface. In order to store the data at these addresses in all addresses A _L(0) to _{A L(199)} of the display memory, the address of the waveform memory 23 is
Which address to select from A _M(0) to _{A M(1355)} is determined using equation (4). i=1355.9-1/200-1×j=1354.9/199×j=6.81
×j Here, number 6.81 is sequentially multiplied by integers 0 to 199 to determine the address to be selected, but during this multiplication, number i is converted to an integer (procedure
_P9 ). In this example, integer conversion is performed by rounding off. Each address of the waveform memory selected in this way is sequentially displayed as each address A _L(0) ~
A _L(199) , and the data of the former address is stored in the latter address (step P ₁₀ ). This can be summarized in a table as follows.

〔Effect of the invention〕

As described above, in the present invention, the data of the received reflected wave is stored in the waveform memory, and the speed of sound is calculated based on the address of the memory and the known thickness, and this is stored in the memory. Since calculations regarding the distance axis are performed based on the speed of sound and the sampling period of the waveform memory, settings regarding the distance axis such as measurement range and defect position can be made extremely easily and accurately.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an ultrasonic flaw detector according to an embodiment of the present invention, FIG. 2 is a waveform diagram of a part of the reflected wave, FIG. 3 is an explanatory diagram of the contents of the waveform memory shown in FIG. 1, and FIG. The figures are a flowchart explaining the operation of the ultrasonic flaw detector shown in Fig. 1, Fig. 5 is a block diagram of a conventional ultrasonic flaw detector, Fig. 6 is a circuit diagram of the sweep circuit shown in Fig. 5, and Fig. 7 is a block diagram of the conventional ultrasonic flaw detector. The figure is a waveform diagram of reflected waves. DESCRIPTION OF SYMBOLS 1...Object to be inspected, 1f...Defect, 2...Ultrasonic probe, 5...Transmitter, 6...Receiver, 21...
...Ultrasonic flaw detector, 22...A/D converter, 23...
... Waveform memory, 24 ... Address counter, 25
...Timing circuit, 26...CPU, 27...
RAM, 28...ROM, 29...Measurement range setting section, 30...Keyboard input section, 31...Liquid crystal display section.

Claims (1)

[Claims] 1. A transmitter that outputs a predetermined pulse to an ultrasound probe, a receiver that receives a signal from the ultrasound probe, and a waveform of the signal based on the signal received by the receiver. In an ultrasonic flaw detector, the ultrasonic flaw detector is equipped with a memory that stores the input signals received by the receiver in addresses sequentially at a predetermined sampling period, and a display that displays the thickness of the object to be tested or an object made of the same material. sound velocity calculation means for calculating the speed of sound propagating within the object to be inspected based on an address for storing a peak value corresponding to the thickness and the thickness in the memory; and a memory for storing the sound speed calculated by the sound speed calculation means. What is claimed is: 1. A distance axis setting device for an ultrasonic flaw detector, comprising: a distance axis calculation means for performing calculations regarding the distance axis based on the speed of sound and a sampling period of the memory.