JPH049261B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an electronic scanning ultrasonic flaw detection device,
In particular, the present invention relates to an electronic scanning type ultrasonic flaw detection apparatus suitable for flaw detection of steel materials and the like where mode conversion between longitudinal waves and transverse waves occurs when ultrasonic waves enter and exit from a measurement system.

[Prior art]

Electronic scanning ultrasonic flaw detection equipment has multiple probes arranged in an array, and an electronic circuit controls the direction and phase of the ultrasonic waves emitted from each contact. Flaw detection is performed by focusing upward and moving the focus over time to scan the object, and this technology has been developed and put into practical use in the medical field. In this medical case, the human body, which is the subject, is mostly water, so
From the moment the ultrasonic wave is emitted from the probe until it returns again, it is treated as a longitudinal wave.
However, when this technology and equipment is applied to flaw detection of steel materials, etc., longitudinal ultrasonic waves are emitted from the probe, and when they enter the object, they form longitudinal waves at a refraction angle that follows Snell's law. A component that propagates into the subject's body and a component that is mode-converted into a transverse wave and propagates into the subject's body are generated, and the refraction angles of the longitudinal wave and the transverse wave are different. Of course, this path is reversible, and the ultrasound reflected within the subject also returns to the probe as a longitudinal wave on the opposite path to the incident path. The ultrasound that is reflected as a longitudinal wave inside the subject and the ultrasound that is reflected as a transverse wave inside the subject and returns at a different location have different sound pressures. The sound pressure ratio changes greatly depending on the angle of incidence on the subject. For this reason, in a device similar to that used in the medical field, which always detects as a signal the change in the reversal ratio near the focal point of the longitudinal wave component within the subject depending on the presence or absence of a wound, the longitudinal wave component is greatly attenuated. There is a drawback that sometimes the S/N ratio of the signal is significantly reduced.

In order to deal with this, some methods perform flaw detection using a component with higher intensity depending on the angle of incidence of the ultrasonic wave on the object to be inspected, such as steel material. In this case, it is necessary to switch the components to be used according to changes in the angle of incidence, and for this reason, the aforementioned control parameters for each probe must be changed, and the parameters for processing the received signal must also be changed accordingly. let but,
In this type of conventional equipment, the refractive index and transmittance of longitudinal waves and transverse waves in the object with respect to the angle of incidence are given based on fixed characteristics that have been theoretically analyzed, so they are different from the actual situation. They did not match and sufficient improvement could not be obtained.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electronic scanning ultrasonic flaw detection device that eliminates the drawbacks of the prior art described above and can further improve the S/N ratio.

[Summary of the invention]

The present invention focuses on the mode conversion of ultrasonic waves generated at the interface between the subject and the medium in contact with it.
In addition to performing flaw detection by selecting longitudinal waves or transverse waves, whichever has a larger sound pressure amplitude, the parameters for flaw detector control and signal processing corresponding to that selection and the selected mode are externally determined based on actual measured values. It is characterized by being able to be set accurately.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail using the drawings.
FIG. 1 is a block diagram showing an embodiment of the present invention.
This is an ultrasonic switching device 13 consisting of an ultrasonic switching circuit 12 and its input device 11, which is a feature of the present invention, added to the conventional electronic scanning type ultrasonic flaw detection device. In the figure, the input device 1 is used to determine the sound velocity of the object (hereinafter, this will be explained as a steel material),
Control parameters related to the incident angle of ultrasonic waves, etc. are input to the ultrasonic beam control circuit 2. The ultrasonic beam control circuit 2 receives a signal from an ultrasonic switching circuit 12 having an input circuit 11 and an input from the input device 1, performs calculations according to these signals, and outputs a pulse oscillator 3 and a delay circuit connected thereto. 4 and signal processing circuit 6, respectively. The pulse oscillator 3 oscillates a pulse for ultrasound transmission after the delay time of the delay circuit 4 is set by the ultrasound beam control circuit 2. The pulses delayed by the delay circuit 4 are input to the array probe 5, and ultrasonic waves are transmitted. The transmitted ultrasonic waves are reflected by the reflector, received by the array probe 5, passed through the delay circuit 4, and input into the signal processing circuit 6. The signal processing circuit 6 performs signal processing on the received ultrasound signal using the ultrasound beam control signal received from the ultrasound beam control circuit 2, and sends the processing result to the display device 7. The display device 7 is a general display device such as a CRT or a printer, and is used to display the results of the signal processing circuit 6. The above is a description of the entire device. Next, as a preparation for explaining the operation, mode conversion at the interface between water and steel will be explained.

Conventionally, in electronic scanning flaw detection equipment, there is a gap between the array probe 5 and the steel material 22 as shown in FIG.
A liquid couplant 21 such as water is introduced, and the ultrasonic beam 31 is deflected and focused under the control of the ultrasonic beam control circuit 2 to scan the beam within the steel material 22 and the focal point 23. This control is performed by adjusting the phase of the ultrasonic waves from each probe in the array using the delay circuit 4, and converges them directly below the array 5 as shown in the left half of FIG. Scanning is performed by deflecting and converging as shown in the right half of the figure. By the way, as shown in FIG. 3, the ultrasonic waves (longitudinal waves, transverse waves do not occur in water) output from each probe 32 are refracted and refracted at the interface between the water 21 and the steel material 22, which have different sound speeds. Mode conversion occurs, and longitudinal waves L and transverse waves S are generated in the steel material 22. Of these, the longitudinal wave L is refracted at a refraction angle θ _L according to the well-known Snell's law, but the refraction angle θ _S of the transverse wave S is smaller than that of the longitudinal wave. In other words, steel material 22
proceed in different directions within. Even when the reflected light travels from the steel material 22 to the water 21, it follows a reversible path. Not only the path differs depending on the mode, but also the sound pressure. Figure 4 shows the theoretical relationship between the change in sound pressure and the angle of incidence and angle of refraction for each mode. The vertical axis shows the round-trip passage rate of longitudinal waves.
T _L and the shear wave round trip passage rate T _S are shown. This round-trip passage rate means that when the sound pressure of the ultrasonic wave entering the object (steel) from the contact medium (water) is 100%,
This is the sound pressure expressed in % when the ultrasonic waves of each mode are totally reflected in the steel material and return to the water via the opposite path. On the other hand, the refraction angles θ _L and θ _S of longitudinal waves and transverse waves are plotted on the horizontal axis of FIG. 4, and the corresponding incident angles are simultaneously indicated as α _L and α _S. In other words, in Figure 4, the refraction angles θ _L and θ _S for both mode waves are expressed on the same scale, so the scales of the corresponding incident angles α _L and α _S differ depending on the mode. It shows.

As shown in the characteristics in Figure 4, the refraction angle is approximately
At 34°, the magnitudes of the round-trip passage rates T _S and T _L change. For this reason, as described in the conventional example, in a method using only longitudinal waves similar to applications in the medical field, S/N deterioration of the detection signal occurs depending on the scanning position. Therefore, we fixed _the characteristics as shown in Figure 4, and set the refraction angle θ ₀ in the figure as the switching angle so that the round-trip passing rates T _S and T _L each stably become larger values. A method of using the transverse wave S at a refraction angle of θ and a longitudinal wave L at a refraction angle of θ ₀ or less was considered. During this switching, since the corresponding incident angle for the same refraction angle differs depending on the mode, the scanning position moves smoothly by changing the incident angle so that the refraction angle does not change before and after the mode switch. Control such as this is also performed by the ultrasonic beam control circuit 2. However, in the conventional device using this method, the characteristics shown in FIG. 4 are fixed. However, the speed of sound in steel varies depending on temperature, sedimentation, etc. in both longitudinal and transverse wave modes, and the velocity of longitudinal waves in water also varies depending on water temperature. Since the refraction angle also changes in accordance with these speed changes, accurate control has not been possible. For this reason, in the embodiment shown in FIG. 1, an ultrasonic switching device 13 is provided to eliminate this drawback, and its operation will be explained below.

FIG. 5 is an operational flowchart of the embodiment shown in FIG. First, in this apparatus, in step 100, parameters indicating the dimensions of the array probe, the number n of probes, etc., and the scanning range and scanning pitch are set in the control circuit 2 from the input device 1. Among these, in the scanning range β, the refraction angle θ is |θ|<
It is a parameter that is limited to change within a range of β, and within this range, θ is changed stepwise by the magnitude specified by the scanning pitch. In addition, the velocity of water and steel material (subject), which changes depending on temperature, etc., the relationship between the refraction angle θ and the incident angle α obtained from the characteristics at that time corresponding to Fig. 4, and the longitudinal wave and transverse wave. In step 101, the boundary angle θ ₀ and the like to be used are set from the input device 11 to the switching circuit 12. Subsequently, in step 102, the control circuit 2 sets the initial value of the refraction angle θ to θ=β. However, since this initial setting is a different value for each individual probe, it must be set for each probe. For this purpose, if the value of β set in step 100 is for one predetermined probe on the probe array 5, then using this as a reference, the other input probes The scanning range β ₁ for each probe can be calculated from the dimensions of , the length of the array, etc., and of course each refraction angle θ ₁ will have a different value. Next, in step 103, it is determined whether |θ ₁ |>θ ₀ with respect to the refraction angle θ ₁ of each probe at that time, using the boundary angle θ ₀ input in the switching circuit 12, and the result and When there is a mode switching corresponding to the result, data corresponding to the switched mode such as sound speed necessary for subsequent processing is transferred to the control circuit 2. In step 104, as a result of the determination in step 103,
For a probe that satisfies |θ ₁ | > θ ₀ , find the incident angle α _S of the transverse wave S corresponding to the incident angle θ ₁ from the characteristics shown in Figure 4 and use it as the incident angle of the probe. This delay time τ ₁ is determined by the corresponding delay circuit 4. Furthermore, if the probe satisfies |θ ₁ |<θ ₀ , the incident angle α _L corresponding to the longitudinal wave L and the corresponding delay time τ ₁ are similarly determined. Furthermore, in step 104, the parameters required in step 106 are transferred to the signal processing circuit 6 when the mode is switched. In step 105, ultrasonic waves are outputted toward a focus determined by the ultrasonic waves from each probe having a phase determined by the determined delay time τ ₁ to detect flaws inside the steel material. The received signal is input to the signal processing circuit 6.
In step 106, this received signal and the control circuit 2
The necessary processing is performed using the parameters from and the results are displayed on the display device 7. When this is completed, in step 107, the control circuit 2 decreases each refraction angle θ ₁ by a scanning pitch (taken as a negative value), and in step 108 it is determined whether the resulting θ ₁ satisfies |θ ₁ |<β ₁ or not. do. If not, it is assumed that the scanning has ended, but if |θ ₁ |<β ₁ , the process returns to step 103 and the following steps are repeated.

Through the above operations, as shown in FIG. 7, the refraction angle θ ₁ changes stepwise from β ₁ to −β ₁ and scanning is performed, and the determination step 1 is performed corresponding to |θ ₁ |θ ₀ .
As a result of step 03, u is output, and at the time of this switching, the data transfer v in step 103 described above is executed. In this way, by controlling the switching circuit 12,
For example, as shown in Figure 8, each probe can always use waves in modes with higher sound pressure, so the S/N ratio of detection signals for scratches, etc. is improved, and experiments have shown that this improvement The amount is about 6dB. Furthermore, data representing the characteristics shown in FIG. 4 for this switching can be easily set from the input device 11 in accordance with the temperature and the material of the subject, allowing accurate mode switching and processing.

[Effects of the Invention] As is clear from the above embodiments, according to the present invention, efficient transmission and reception of ultrasonic waves can be achieved by simply adding a simple ultrasonic switching device to a conventional electronic scanning ultrasonic flaw detection device. As a result, the S/N ratio is significantly improved, precision flaw detection is possible, and flaw detection performance is improved.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention;
Figure 2 is an explanatory diagram of the convergence and deflection state of the ultrasonic beam, Figure 3 is an explanatory diagram of the refraction and mode conversion of the ultrasound beam, and Figure 4 is the theoretical value of the round-trip passage rate of the ultrasound in water and steel. Figure 5 is an operation flowchart of the embodiment shown in Figure 1, Figure 6 is an explanatory diagram of the scanning range, Figure 7 is an operation time chart of the embodiment shown in Figure 1, and Figure 8 is an operation flowchart of the embodiment of Figure 1. FIG. 1... Input device, 2... Ultrasonic beam control circuit, 3
...Pulse oscillator, 4...Delay circuit, 5...Array probe, 6...Signal processing circuit, 11...Input circuit, 12...
Ultrasonic switching circuit, 13... Ultrasonic switching device, 21...
Water, 22...Object, 23...Focal point, 31...Ultrasonic beam, 32...Probe, L...Longitudinal wave, S...Transverse wave.

Claims (1)

[Claims] 1. Ultrasonic waves output from the individual probes constituting the array probe and incident on the subject via a liquid contact medium converge at a focal position within the subject, and the focal position changes over time. a control means for controlling the phase of the output ultrasound from each probe so as to move within the subject; In an electronic scanning ultrasonic flaw detection device equipped with a signal processing means for processing a received signal received by each probe in a reversible path, the ultrasonic wave of one longitudinal wave mode propagating in a coupling medium is A boundary angle indicating a boundary as to which mode of a longitudinal wave or a transverse wave that propagates through the object with different refraction angles corresponding to the sound wave is selected as the ultrasonic wave for flaw detection of each probe, and the above-mentioned Input means for inputting parameters required for the control means and signal processing means corresponding to each mode, and one scanning position in the phase control means is determined by specifying the refraction angle of each probe. The mode to be used by each of the probes is determined by comparing the refraction angle with the input boundary angle at each point in time, and the control means controls each probe corresponding to that mode. and a function of transmitting the input parameters corresponding to the newly selected mode to the control means and signal processing means if the determined mode is different from the previous mode. 1. An electronic scanning ultrasonic flaw detection device, characterized in that it has a switching means having: