JP2002243703A - Ultrasonic flaw detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a defect existing in the vicinity of a surface of a specimen detected. SOLUTION: A waveform data of a reflected echo provided by a probe 10 in each flaw detection position is stored in a waveform memory 40. A difference computing means 31 conducts difference computation between the waveform data obtained by flaw detection in the each flaw detection point and the waveform data obtained by the last flaw detection in the flaw detection point adjacent to the flaw detection position to find a difference waveform data. A surface echo reflected on the specimen 2 to be returned is removed thereby, and only a defect echo reflected by the defect to be returned is contained in the difference waveform data, when the defect exists in the vicinity of the surface of the specimen 2. The defect existing in the vicinity of the surface of the specimen 2 is detected thereby based on the difference wave form data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flaw detector for non-destructively inspecting internal defects such as steel materials using ultrasonic waves.

[0002]

2. Description of the Related Art Conventionally, an ultrasonic flaw detector has been known as a device for nondestructively inspecting a defect which may occur in a steel material or the like. Such an ultrasonic flaw detector uses a probe,
The inspection of the defect in the inspection object is performed. The transducer is
Ultrasonic waves are made to enter the object to be inspected, and the ultrasonic waves (reflected echoes) reflected by the reflection source in the object to be inspected are received. here,
The probe includes a vertical probe that transmits ultrasonic waves that travel perpendicular to the surface of the device under test, and an oblique probe that transmits ultrasonic waves that travel obliquely to the surface of the device under test. There is a child. If there is an uneven portion such as a defect or the like in the surface or bottom surface of the inspection object or the inspection object, the ultrasonic wave is reflected using the non-uniform portion as a reflection source. Therefore, for example, the reflected echo received by the vertical probe includes a surface echo reflected on the surface of the inspection object, a defect echo reflected on a defect, and a bottom echo reflected on the bottom surface of the inspection object. included.

[0003] The ultrasonic flaw detection apparatus specifies the echo height and the position of the reflection source based on the reflection echo received by the probe. Thereafter, for each reflection echo, it is determined whether the reflection source is defective or not by examining whether the reflection source is included in a predetermined area, the echo height is equal to or more than a predetermined value, and the like. Then, the ultrasonic flaw detection apparatus creates a flaw detection image in which the echo height is plotted at the position of each defect, and the operator determines the presence or absence of the defect based on the flaw detection image.

[0004]

For example, when performing a flaw detection using a vertical probe, the distance from the probe to the surface of the device under test is the distance from the probe to the bottom surface of the device under test. Of course, the probe will receive the surface echo first and then the bottom echo. At this time,
If a defect exists inside the object to be inspected, the probe receives the defect echo between the time of receiving the surface echo and the time of receiving the bottom echo. However, since each echo has a certain extent, if a defect exists near the surface of the test object, the defect echo reflected by the defect may overlap with the surface echo and be buried in it. is there. For this reason, it is difficult to detect a defect echo buried in the surface echo, and therefore, there is a limit in detecting a defect existing near the surface of the inspection object.

[0005] The present invention has been made based on the above circumstances, and has as its object to provide an ultrasonic flaw detector capable of detecting a defect existing near the surface of an object to be inspected.

[0006]

According to a first aspect of the present invention, there is provided a probe for transmitting an ultrasonic wave into an object to be inspected and receiving an ultrasonic wave returning from the object to be inspected. Scanning means for scanning the probe at a predetermined pitch along the surface of the object to be inspected, and a waveform of an ultrasonic wave obtained by the probe at each flaw detection position during scanning by the scanning means. In an ultrasonic flaw detector for inspecting a defect in the inspected body based on data, the waveform data obtained by flaw detection at each flaw detection position and the waveform data obtained by flaw detection at a flaw detection position adjacent to the flaw detection position Calculation means for obtaining difference waveform data by performing a difference calculation with
Display means for displaying the differential waveform data obtained by the calculation means.

According to a second aspect of the present invention, in the ultrasonic inspection apparatus according to the first aspect, a defect is detected in a region near the surface of the inspection object based on the differential waveform data obtained by the arithmetic means. It is characterized by comprising a judging means for judging whether or not it exists.

According to a third aspect of the present invention, in the ultrasonic flaw detector according to the first or second aspect, the probe transmits an ultrasonic wave which travels substantially perpendicularly to the surface of the inspection object. It is a feature.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram of an ultrasonic flaw detector according to one embodiment of the present invention, and FIG. 2 is a diagram for explaining flaw detection waveform data received by a probe of the ultrasonic flaw detector.

As shown in FIG. 1, such an ultrasonic flaw detector is for detecting a defect inside the object 2 to be inspected, and includes a probe 10, a scanning device (not shown), and an AD.
It includes a conversion unit 20, a control unit 30, a waveform memory 40, a difference waveform memory 50, and a display device 60.

The probe 10 transmits an ultrasonic wave into the inspection object 2 and receives an ultrasonic wave (reflected echo) returning from the inspection object 2. In the present embodiment, as the probe 10,
It is assumed that a so-called vertical probe that transmits an ultrasonic wave that travels substantially perpendicular to the surface of the test object 2 is used. Since a known probe can be used as the probe 10, a detailed description of the structure of the probe 10 is omitted here.

The scanning device scans the probe 10 at a predetermined pitch along the surface of the test object 2. This pitch interval is set to, for example, 1 mm. Further, water is interposed between the probe 10 and the device under test 2 as a contact medium. Therefore, the probe 10 and the test object 2
As shown in FIG. 1, they are separated by a certain distance.

The probe 10 performs a flaw detection operation every time it moves by a predetermined pitch along a predetermined direction. For example, FIG.
As shown on the left side of (a), the probe 10 is stopped at a certain flaw detection position, and one defect F exists just below the flaw detection position and substantially at the center of the test object 2. Shall be. When the flaw detection operation starts at the flaw detection position, first, the probe 10 generates an ultrasonic wave. Ultrasonic waves generated from the probe 10 are incident on the surface S of the device under test 2 substantially perpendicularly. At this time, part of the ultrasonic wave returns to the probe 10 as the reflection surface echo E _S at the surface S of the subject 2, another ultrasound enters the inside of the subject 2. The ultrasonic wave that has entered the test object 2 propagates toward the bottom surface of the test object 2 as it is. Then, a part of the ultrasonic wave propagating in the subject 2 is
The light is reflected by the defect _F and returns to the probe 10 as a defect echo EF. A part of the ultrasonic wave reaches the bottom surface B of the subject 2 is probe 10 as bottom echo E _B is reflected by the bottom surface B
Return to As described above, the probe 10 receives the flaw detection waveform data of the reflected echo that has been returned from each of the reflection sources existing in the area immediately below the flaw detection position at each of the flaw detection positions.

The right side of FIG. 2A shows an example of flaw detection waveform data received by the probe 10 when one defect F exists at a substantially central portion of the test object 2. The flaw detection waveform data has the echo height on the vertical axis and the beam path on the horizontal axis. The beam path is the distance from the ultrasonic wave emission position to the reflection source. Water as a contact medium and test object 2
Since the speed of sound of the ultrasonic wave propagating inside the inside of each is substantially constant, the beam path is calculated from the time required for the ultrasonic wave to propagate that distance. In this case, the probe 10
Initially receiving the surface echo E _S, then defect echo E
_F is received. Then, receiving the bottom echo E _B further delayed. Therefore, if the defect exists at a relatively deep position in the inspection object 2, the defect can be detected based on the flaw detection waveform data as shown on the right side of FIG.

Although the probe 10 and the device under test 2 are separated by a certain distance, the distance is determined according to the thickness of the device under test 2. That is, the surface echo received by the probe 10 includes not only the surface echo in which the ultrasonic wave is reflected once and returns on the surface of the test object 2, but also, for example, the ultrasonic wave between the test object 2 and the probe 10. There is also a surface echo (second surface echo) that returns to the probe 10 after the second reflection on the surface of the test object 2 after the reflection. If the second surface echo returns to the probe earlier than the bottom surface echo, it becomes difficult to distinguish the second surface echo from the defect echo. Therefore, the distance between the probe 10 and the test object 2 is set according to the thickness of the test object 2 so that the second surface echo returns to the probe 10 later than the bottom echo. ing.

Incidentally, a defect such as a flaw may be present in a relatively shallow portion of the device under test 2. The flaw detection waveform data when the defect echo E _F in flaw detection waveform data shown in FIG. 2 (a) is such that close to the surface echo E _S. Then, as shown on the left side of FIG. 2B, when the defect F exists near the surface of the inspection object 2, the defect echo overlaps the surface echo and is buried therein. That is, in this case, as shown on the right side of FIG. 2B, in the beam path corresponding to the vicinity of the surface of the inspection object 2, the echo E where the surface echo and the defect echo overlap each other.
_{S + F} appears. The surface layer region of the inspection object 2 in which the defect echo is buried in the surface echo is referred to as “surface dead zone”. In the conventional ultrasonic flaw detector, the surface dead zone is generated in a relatively wide range, and it is difficult to detect a defect generated near the surface of the inspection object 2. However, in the present embodiment, as described later, the surface Flaw detection with a narrow dead zone is possible.

The AD converter 20 converts the flaw detection waveform data of the reflected echo received by the probe 10 into digital waveform data. For example, the echo height is 1-byte data and takes a value from 0 to 255. This digital waveform data is stored in the waveform memory 40.

The control unit 30 controls scanning of the probe 10 and processes data obtained by the probe 10. As shown in FIG. 1, the control unit 30 includes a difference calculating unit 31, a peak detecting unit 32, and a defect determining unit 33.
And a flaw detection image creating means 34.

The difference calculating means 31 calculates a difference between digital waveform data obtained by flaw detection at each flaw detection position and digital waveform data obtained by previous flaw detection at a flaw detection position adjacent to the flaw detection position. This is for obtaining waveform data. Such difference waveform data is stored in the difference waveform memory 50. The peak detecting means 32 determines the echo height of each peak and the position of the reflection source (echo position corresponding to each peak) based on the digital waveform data stored in the waveform memory 40 and the differential waveform data stored in the differential waveform memory 50. ) And ask. Defect judgment means 33
Determines whether a defect exists in the inspection object 2 based on the result obtained by the peak detection means 32. Then, the flaw detection image creating means 34 creates a flaw detection image in which the echo height is plotted at the echo position of the echo determined as a defect by the defect determining means 33.
Note that each of the above means is actually realized by software.

The display device 60 displays digital waveform data and differential waveform data, and displays a flaw detection image created by the flaw detection image creating means 34.

Next, a procedure for processing data obtained by the probe 10 in the ultrasonic flaw detector according to the present embodiment will be described.
FIG. 3 is a flowchart for explaining a data processing procedure in the ultrasonic inspection equipment of the present embodiment. Also,
FIG. 4 is a diagram for explaining the processing contents of the difference calculating means 31.

After the scanning and flaw detection operations of the probe 10 have been completed and the digital waveform data has been stored in the waveform memory 40, the control unit 30 executes processing according to the flow of FIG.
First, the difference calculating means 31 of the control unit 30 reads digital waveform data obtained by flaw detection at each flaw detection position from the waveform memory 40. Then, differential waveform data is obtained by performing a difference operation between the digital waveform data obtained by the flaw detection at the flaw detection position and the digital waveform data obtained by the previous flaw detection at the flaw detection position adjacent to the flaw detection position (S1). .

For example, as shown in FIG. 4, a defect F exists near the surface of the inspection object 2 facing the inspection position, while the inspection object facing the previous inspection position adjacent to the inspection position. It is assumed that no defect exists in the inside of No. 2. At this time, the wound waveform data probe in place of the beam path length corresponding to near the surface of the subject 2, in the case of the flaw in the inspection position, includes only the surface echo E _S, whereas, flaw detection In the case of flaw detection at a position, an echo ES _{+ F in} which a defect echo and a surface echo are superimposed is included. Normally, when the surface of the steel material as the test object 2 is flat, the surface state at two adjacent points on the test object 2 hardly changes. For this reason, it is considered that the surface echoes obtained by the flaw detection at these two adjacent points are almost the same. That flaw detection surface echo obtained in flaw at position may be considered resulting surface echo E _S Tohodondo same for flaw detection in inspection position. Therefore, when converting the flaw detection waveform data into digital waveform data, the difference waveform data ΔE obtained by taking the difference between the surface echo E _S in the echo E _{S + F} and flaw detection position in the inspection position
In the flaw detection position, the probe 10
Represents the defect echo that has returned. The difference waveform data thus obtained is stored in the difference waveform memory 50.

It is sufficient that the difference calculation is performed only on the digital waveform data in the beam path corresponding to the vicinity of the surface of the test object 2. This is because the difference waveform data is used for detecting a defect near the surface of the inspection object 2. However, it is free to perform a difference operation on all digital waveform data.

The difference waveform data obtained by the difference calculation means 31 can be displayed on the display device 60. As a result, the operator can immediately determine whether there is a defect with his own eyes.

Next, the peak detecting means 32 finds each peak from the digital waveform data stored in the waveform memory 40 and the differential waveform data stored in the differential waveform memory 50, and determines the echo height and the beam path for each peak. Extract (S2). Thereafter, the defect determining means 33 determines whether each of the echoes obtained by the peak detecting means 32 is a defective echo (S3). Specifically, the peak found from the digital waveform data is present inside the inspection object 2 and in a region other than the vicinity of the surface thereof, and the echo height is equal to or higher than a predetermined threshold value. Sometimes, the echo is determined to be a defective echo.
On the other hand, when the peak found from the differential waveform data is present in a region inside the inspection object 2 near the surface thereof and the echo height is equal to or higher than the threshold value, Is determined to be a defect echo.
An echo that does not satisfy the above conditions is determined to be not a defective echo.

Next, the flaw detection image creating means 34 creates a flaw detection image (S4). This is performed as follows.
First, the flaw detection image creating unit 34 divides a predetermined area in the three-dimensional view of the inspection object 2 into cells of a certain size. Here, the cell is basically a cube having a side length of 1 mm, but can be set arbitrarily. Next, the flaw detection image creating means 34 plots the height of each echo identified as a defective echo by the defect determining means 33 in a cell corresponding to the echo position. In particular,
For example, plotting is performed by color-coding according to the echo height. This is performed for each defect echo. Thus, a flaw detection image is created.

Incidentally, if a three-dimensional view is used as a flaw detection image, it may be difficult for an operator to evaluate a defect. Therefore, an image created by projecting each echo height onto a predetermined plane can be created.

Thereafter, the control section 30 displays the flaw detection image created by the flaw detection image creating means 34 on the display device 60 (S5). The operator examines the flaw detection image to determine whether the defect is acceptable when the defect has occurred. Then, finally, the pass / fail of the subject 2 is determined.

In the ultrasonic flaw detector of this embodiment, the difference calculation is performed between the waveform data obtained by the flaw detection at each flaw detection position and the waveform data obtained by the flaw detection at the flaw detection position adjacent to the flaw detection position. Ask for data. Thereby, when a defect is present near the surface of the object to be inspected, the surface echo that has returned and reflected on the surface of the object to be inspected is removed from the differential waveform data, and the surface echo that has returned and reflected by the defect is removed. Only the defect echo will be included. For this reason,
Based on the difference waveform data obtained by the difference calculation,
Defects existing near the surface of the inspection object can be detected.

The present invention is not limited to the above embodiment, and various modifications are possible within the scope of the invention.

In the above-described embodiment, the case where the flaw detection is performed using the vertical probe has been described. However, if there is a demand to inspect a defect existing near the surface of the object to be inspected, the oblique probe is used. The present invention can also be applied to the case where it is used.

[0033]

As described above, according to the ultrasonic inspection apparatus of the present invention, the waveform data obtained by the inspection at each inspection position and the waveform data obtained by the inspection at the inspection position adjacent to the inspection position To calculate difference waveform data. Thereby, in the case where a defect exists near the surface of the inspection object, the surface echo reflected and returned on the surface of the inspection object is removed from the differential waveform data, and the differential echo data is reflected and returned on the defect. Only the defect echo will be included. For this reason, it is possible to detect a defect existing near the surface of the inspection object based on the difference waveform data obtained by the difference calculation.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an ultrasonic flaw detector according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining flaw detection waveform data received by a probe of the ultrasonic flaw detection apparatus.

FIG. 3 is a flowchart for explaining a data processing procedure in the ultrasonic flaw detector according to the embodiment;

FIG. 4 is a diagram for explaining the processing contents of a difference calculating means.

[Explanation of symbols]

 2 Inspection object 10 Probe 20 A / D conversion unit 30 Control unit 31 Difference calculation means 32 Peak detection means 33 Defect judgment means 34 Flaw detection image creation means 40 Waveform memory 50 Difference waveform memory 60 Display device

Claims (3)

[Claims] 1. A probe for transmitting ultrasonic waves into an object to be inspected and receiving ultrasonic waves returning from the object to be inspected, and scanning the probe at a predetermined pitch along the surface of the object to be inspected. An ultrasonic flaw detector which performs a defect inspection in the object to be inspected based on ultrasonic waveform data obtained by the probe at each flaw detection position during scanning by the scanning means, Calculating means for calculating differential waveform data by performing a difference calculation between the waveform data obtained by the flaw detection at each flaw detection position and the waveform data obtained by the flaw detection at a flaw detection position adjacent to the flaw detection position; And a display means for displaying the differential waveform data obtained in (1). 2. The apparatus according to claim 1, further comprising a determination unit configured to determine whether a defect exists in a region near the surface of the inspection object based on the difference waveform data obtained by the calculation unit. 2. The ultrasonic flaw detector according to claim 1. 3. The ultrasonic flaw detector according to claim 1, wherein the probe emits an ultrasonic wave that travels substantially perpendicularly to the surface of the inspection object.