JPH11281628A - Evaluation apparatus for crack in weld of object to be inspected and probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an evaluation apparatus in which the energy intensity of a reflected echo from a crack is compensated and in which the crack is evaluated with high accuracy even when the inclination of the crack generated in a weld on the fillet surface of a nozzle is unknown. SOLUTION: A probe in which ultrasonic waves are made incident on an object, to be inspected, in two directions from a first transmitting-receiving element 1a and a second transmitting-receiving element 1b is provided. A first detecting means 3a and a second detecting means 3b which measure reflected echoes from the two directions are provided. An incident-position computing means 9 by which a position in which the ultrasonic waves are incident on the object, to be inspected, is computed on the basis of the incidence and reflection propagation time obtained by the first detecting means 3a is provided. An angle-of- incidence and angle-of-reflection computing means 10 by which the angle of incidence and the angle of reflection of the ultrasonic waves at the second transmitting-receiving element 1b are computed on the basis of the incidence and reflection propagation time obtained by the incident position of the ultrasonic waves and by the second detecting means 3b is provided. An echo-energy-compensation computing means 13 by which the energy intensity of the echo obtained from the second detecting means 3b is compensated by the known transmittance of a sound pressure and by the known reflectance of the sound pressure is provided. A crack evaluating means 15 which evaluates a crack on the basis of compensated echo energy and crack shape data is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for evaluating a crack generated at a weld portion of a nozzle by using ultrasonic waves, and more particularly to a crack evaluation apparatus suitable for evaluating a crack having an unknown inclination. .

[0002]

2. Description of the Related Art It is generally known that a device or a structure to which a repeated load acts is subject to fatigue damage and cracks, which hinders safe operation. In particular, thermal stress acts on the fillet welding of the nozzle attached to the pipe side of the boiler during operation, and a crack 7 as shown in FIG. 8 may occur. Since the crack 7 is generated from the inside of the fillet weld 6 starting from the partial penetration portion 8 corresponding to the stress concentration part when the nozzle 5 is fillet welded 6 to the pipe 4, the penetrant inspection method or the magnetic particle inspection method Therefore, ultrasonic flaw detection is used because it cannot be detected.

[0003] In the conventional ultrasonic flaw detection method used for evaluating the crack 7 as described above, a probe 16 is applied to the outer surface of a nozzle 5 and a transmitting / receiving element 1 incorporated in the probe 16 is used. The ultrasonic wave 2 generated in the above is incident on the material of the nozzle 5 in an oblique direction, and is reflected once by the inner surface of the nozzle 5 to be transmitted to a desired fillet weld 6.

The transmitting and receiving element 1 receives a reflected echo (hereinafter referred to as a reflected echo) generated when the ultrasonic incident wave 2a propagated to the fillet weld 6 hits the crack 7 so that the crack is generated. 7, and the evaluation of the crack 7 is performed by scanning the probe 16 in the axial direction of the nozzle 5 indicated by the arrow in FIG. 8 and using the maximum energy intensity of the reflected echo received by the transmitting / receiving element 1. I have.

Here, the intensity of the reflected echo received by the transmission / reception element 1 depends on the sound pressure transmission rate related to the incident angle i when the ultrasonic wave 2 is incident on the material of the nozzle 5, and the ultrasonic incident wave 2
Since a changes depending on the sound wave reflectance related to the reflection angle α when a is reflected on the inner surface of the nozzle 5, the influence of the sound pressure transmission rate and the sound pressure reflectance is considered in order to evaluate the crack 7 with high accuracy. There is a need to.

[0006]

Since the ultrasonic wave 2 generated by the transmitting / receiving element 1 has a property of being strongly radiated within a certain angle range, the incident wave 2a of the ultrasonic wave incident on the material of the nozzle 5 is used. , 2b, and 2c propagate while expanding, in which only the reflected echo of the ultrasonic incident wave 2a propagating along the path perpendicular to the crack 7 propagates the ultrasonic incident wave 2a. The signal is returned by the transmitting / receiving element 1 in the reverse direction.

However, the reflected echoes of the ultrasonic incident waves 2b and 2c propagating along a path that hits the crack 7 at an angle other than a right angle are scattered and are not received by the transmitting / receiving element 1. For this reason, if the inclination of the crack 7 is known, the incident angle i and the reflection angle α of the ultrasonic wave that generates the reflected echo received by the transmitting / receiving element 1 can be calculated from the inclination of the crack 7. Based on this, it is possible to evaluate the crack 7 with high accuracy in consideration of the sound pressure passage rate and the sound pressure reflectivity.

However, since the inclination of the crack 7 generated in the fillet weld 6 cannot be specified, the incident angle i and the reflection angle α of the ultrasonic wave that generates the reflected echo received by the transmitting / receiving element 1 are conventionally known. However, there is a problem that it is not possible to calculate the crack 7 with high accuracy in consideration of the sound pressure passage rate and the sound pressure reflectivity.

That is, one of the echoes 2a, 2b, and 2c returns depending on the direction of the crack 7 in FIG. Since each of the echoes has a different incident angle i and a different reflection angle α, the energies of the reflected echoes are different. Even if cracks of the same size are used and the directions of the cracks are different, the magnitude of the reflected echo energy is different, and the size of the crack is erroneously determined.

Accordingly, an object of the present invention is to make it possible to evaluate a crack with high accuracy even if the inclination of the crack generated in the fillet welding is unknown.

[0011]

In order to solve the above problems, the present invention mainly employs the following configuration.

A probe that uses the first and second transmitting and receiving elements to transmit ultrasonic waves to the welded part of the object to be inspected from the same position in two directions and receive a reflected echo from the welded part;
A first detecting means for measuring reflected echoes from two directions obtained by the first and second transmitting / receiving elements, respectively;
Detecting means, an incident position calculating means for calculating a position at which an ultrasonic wave is incident on the object to be inspected, based on a propagation time of an incident reflection which is a measurement result from the first detecting means, and an incident position calculating means Incident angle / reflection angle calculating means for calculating an ultrasonic wave incident angle and a reflection angle of the second transmitting / receiving element based on an ultrasonic wave incident position from the apparatus and a propagation time of incident reflection which is a measurement result from the second detecting means; An echo energy compensating means for compensating the echo energy intensity obtained from the measurement result by the second detecting means with the sound pressure transmissivity from the sound pressure transmissivity database and the sound pressure reflectivity from the sound pressure reflectivity database. And crack evaluation means for evaluating a crack based on the compensation echo energy from the echo energy compensation calculation means and the crack shape data from the crack evaluation database. Te, crack evaluation apparatus Ki for evaluating the magnitude of the crack of the device under test welds.

An ultrasonic probe for detecting a crack in a fillet weld by a transmitting element for transmitting an ultrasonic wave to the fillet weld and receiving a reflected echo, wherein the transmitting / receiving element comprises:
A first transmitting / receiving element for transmitting an ultrasonic wave to a partial penetration portion which is a starting point of the crack generation and a butt surface of welding to receive a reflected echo from the partial penetration portion, and the fillet weld portion; A second transmission / reception element capable of transmitting ultrasonic waves to the second part and receiving reflected echoes from the cracks in the fillet welds.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view schematically showing an apparatus for evaluating a crack in a nozzle welded portion according to an embodiment of the present invention, and FIG. 2 shows an example of an ultrasonic wave incidence means and a detection means. FIG. 3 is a diagram for explaining a propagation path of an ultrasonic wave in a welded portion, and FIG.
FIG. 3A is a characteristic curve diagram showing the detection result of the first detection means, and FIG. 3B is a characteristic curve showing the detection result of the second detection means, where the horizontal axis shows the detection result of the reflected echo with time indicated. It is.

FIG. 4 is a characteristic curve diagram showing the relationship between the incident angle of the ultrasonic wave and the sound pressure reciprocal transmittance, and FIG. 5 is a characteristic curve diagram showing the relationship between the reflection angle of the ultrasonic wave and the sound pressure reciprocal reflectivity. FIG. 6 is a characteristic curve diagram showing the relationship between the compensation echo energy intensity and the crack area in consideration of the influence of the incident angle and the reflection angle.

1 and 2, 1a is a transmitting / receiving element for transmitting ultrasonic waves 2a to the partial penetration portion 8, 1b is a transmitting / receiving element for transmitting ultrasonic waves 2b to the fillet weld 6, 2a and 2b are ultrasonic waves, 2a 'and 2b' are ultrasonic wave incident waves, 3a is a first detecting means, 3b is a second detecting means, 4 is a pipe, 5 is a nozzle, 6 is a fillet weld, 7 is a crack, 8 is a part. Penetration part, 9 is incident position calculating means, 10 is incident angle / reflection angle calculating means, 1
1 is a sound pressure transmissivity database, 12 is a sound pressure reflectivity database, 13 is an echo energy compensation calculation means, 14 is a crack shape evaluation database, 15 is a crack evaluation means, 16
Represents a probe, respectively.

In such a configuration, the apparatus for evaluating a crack in a nozzle weld portion according to an embodiment of the present invention is capable of partially melting the nozzle 5 attached to the boiler pipe 4 during a periodical inspection of a thermal power plant. It is used to evaluate a crack 7 generated in the fillet weld 6 starting from the notch 8.

As shown in FIGS. 1 and 2, the method of evaluating the cracks in the nozzle weld basically involves transmitting an ultrasonic wave 2a propagating from the outer surface of the nozzle 5 toward the partial penetration portion 8 of the nozzle 5. A first transmitting / receiving element 1a incident on the material, a first detecting means 3a for detecting a reflected echo from the partial penetration portion 8 and measuring a propagation time Δta of the ultrasonic wave incident by the transmitting / receiving element 1a; An incident position calculating means 9 for calculating the incident position of the ultrasonic wave based on the propagation time Δta measured by the detecting means 3a, and the ultrasonic wave is transmitted from the same position as the ultrasonic wave incident position of the transmitting / receiving element 1a to the fillet weld 6. A transmitting / receiving element 1b for transmitting ultrasonic waves into the material of the nozzle 5, and a second method for detecting a reflected echo from the crack 7 and measuring a propagation time Δtb and an echo energy intensity Fb of the ultrasonic waves incident by the transmitting / receiving element 1b. The angle of incidence i of the ultrasonic wave that caused the crack echo and the angle of incidence of the ultrasonic wave generated by the detecting means 3b, the ultrasonic wave incident position Y by the incident position calculating means 9 and the ultrasonic wave propagation time Δtb by the second detecting means 3b. The incident angle / reflection angle calculation means 10 for calculating the reflection angle α, and the reflection echo intensity Fb from the crack 7 are compensated by the sound pressure transmission data 11 and the sound pressure reflection data 12 (e in FIG. 6).
Echo energy compensation calculating means 13 for calculating B);
And a crack evaluation means 15 for evaluating the crack 7 from the crack shape evaluation database 14 and the compensation echo energy value dB.

First, the detecting means 3a of the partial penetration portion 8 by the transmitting / receiving element 1a, the detecting means 3b of the crack 7 by the transmitting / receiving element 1b, and the detection results from those means are as follows.
This will be described with reference to FIGS. The probe 16 having the transmitting / receiving elements 1a and 1b is pressed against the outer surface of the nozzle 5
While scanning in the direction of the axis, the ultrasonic wave 2a generated by the transmitting / receiving element 1a and the ultrasonic wave 2b generated by the transmitting / receiving element 1b are obliquely incident on the material of the nozzle 5 from the same position.

The ultrasonic incident wave 2a 'propagated to the partial penetration portion 8 has a refraction angle θ of 90 ° propagating through the nozzle surface layer because the surface of the partial penetration portion 8 is perpendicular to the nozzle surface. Nearby horizontal transverse waves (SH waves) are preferred.

The incident ultrasonic wave 2a 'is reflected by the surface of the partial penetration portion 8, and a reflected echo Fa as shown in FIG. 3A is detected by the first detecting means 3a. The propagation time Δta until the ultrasonic incident wave 2a ′ is incident on the material of the nozzle 5 and returns to the incident point again as a reflection echo at the partial penetration part 8 is measured. Then, this propagation time Δta is input to the incident position calculating means 9,
The incident position Y of the ultrasonic incident wave 2a 'based on the partial penetration portion 8 is calculated using the following equation.

Y = Δta × Va ′ × sin θa / 2 where Va ′ is the speed at which the ultrasonic wave 2a ′ propagates through the material of the nozzle 5, and θa is the known refraction angle of the ultrasonic wave 2a.

On the other hand, the incident ultrasonic wave 2b 'is reflected once by the inner surface of the nozzle 5 and then strikes the crack 7 to produce a reflected echo, which is perpendicular to the crack surface as shown in FIG. 3 (2). The reflected echo Fb of the ultrasonic incident wave 2b 'propagating along the path hit by the second detecting means 3b is detected by the second detecting means 3b, and after the ultrasonic incident wave 2b' is incident on the material of the nozzle 5, The propagation time Δtb before returning to the incident point and the echo energy intensity of the reflected echo Fb are measured.

Then, the propagation time Δtb and the ultrasonic incident position Y are inputted to the incident angle / reflection angle calculating means 10, and the reflection angle α of the ultrasonic incident wave 2b 'is calculated by the following equation.

Α = sin ⁻¹ {2Y / (Δtb × Vb ′)} Further, the incident angle i of the ultrasonic wave 2b is calculated using the following equation.

I = sin ⁻¹ {(Vb / Vb ′) × sinα} where Vb ′ is the speed at which the ultrasonic incident wave 2b ′ propagates through the material of the nozzle 5, and Vb is the propagation speed of the ultrasonic wave 2b. is there.

Here, the principle of obtaining the incident angle i and the reflection angle α from the incident position Y will be described again with reference to FIG.

The probe 16 includes a transmitting and receiving element 1a for generating and receiving a horizontal transverse wave (SH wave), a transmitting and receiving element 1b for generating and receiving a longitudinal wave, and a sound absorbing element for absorbing and removing extra ultrasonic waves in the probe 16. It comprises a material 17, a damper 18 for limiting the vibration time of the transmitting / receiving elements 1a and 1b, and a wedge 19 for obliquely entering the ultrasonic waves 2a and 2b into the material of the nozzle 5.

In such a configuration, the transmitting / receiving element 1a
And the refraction angle θa of the ultrasonic wave 2a ′ and the incident angle ib of the ultrasonic wave 2b generated by the transmitting / receiving element 1b and the refraction angle θ of the ultrasonic wave 2b ′.
The following equation holds between b in accordance with Snell's law.

Va / sinia = Va '/ sinθa Vb / sinib = Vb' / sinθb Therefore, the desired refraction angles θa, θb are determined by the ultrasonic waves 2a,
It can be obtained by selecting the incident angles ia and ib of 2a and the material of the wedge 19. Here, Va is the ultrasonic wave 2
a is the speed at which the ultrasonic wave 2a 'propagates through the material of the nozzle 5, Vb is the speed at which the ultrasonic wave 2b propagates through the wedge 19, and Vb' is the ultrasonic wave incident. The speed at which the wave 2b 'propagates through the material of the nozzle 5.

Therefore, when it is desired to obtain an incident ultrasonic wave 2a 'of a horizontal shear wave having a refraction angle θa of about 90 ° with respect to the material of the nozzle 5 having a shear wave sound speed of 3230 m / s,
30m / s acrylic wedge 19, ultrasonic 2a
Transmitting / receiving element 1 so that the incident angle ia of
This can be realized by setting a. That is, the following equation is used.

Ia = sin ⁻¹ (sin 90 × 1430/3230) In the transmitting / receiving element 1 as shown in FIG. 8, the incident angle i and the reflection angle α
However, it is not preferable because it changes depending on the direction of the crack 7.

However, in the embodiment of the present invention, the transmitting and receiving element 1a for transmitting and receiving the horizontal shear wave to and from the partial penetration portion 8 and the transmitting and receiving element 1b for transmitting and receiving the longitudinal wave and the transverse wave to the fillet weld portion 6 are provided. Incident position Y shown in FIG.
, The incident angle i and the reflection angle α can be accurately calculated.

Next, how the echo energy intensity of the reflected echo Fb measured by the second detector 3b is compensated will be described. FIG. 4 is a diagram showing the relationship between the incident angle i of the ultrasonic waves and the sound pressure reciprocation passage rate, and is a part of the sound pressure passage rate database 11 of FIG. As described above, when the ultrasonic wave 2b is incident on the material of the nozzle 5, the amount of energy passing therethrough varies depending on the incident angle i. Therefore, by examining this relationship in advance, the influence of the incident angle i should be avoided. Can be.

That is, if the incident angle i of the ultrasonic wave 2b is known, the energy intensity of the reflected echo Fb can be compensated by the data shown in FIG. Here, the vertical axis is expressed as the sound pressure reciprocal passage rate, because the same phenomenon occurs when the reflected echo returns as when the ultrasonic wave 2b is incident.

FIG. 5 is a diagram showing the relationship between the reflection angle α of the ultrasonic wave and the sound pressure reciprocal reflectivity, and is a part of the sound pressure reciprocal reflectivity database 12 of FIG. As described above, when the ultrasonic incident wave 2b 'is reflected on the inner surface of the nozzle 5, the amount of reflected energy changes depending on the reflection angle α.
Can be avoided.

That is, if the reflection angle α of the ultrasonic wave 2b 'is known, the energy intensity of the reflected echo Fb can be compensated by the data shown in FIG. Here, the vertical axis is represented as the sound pressure reciprocal reflectance, because the same development as when the ultrasonic incident 2b 'is reflected occurs when the reflected echo returns.

As described above, the echo energy compensating means 1
In No. 3, the energy intensity of the reflected echo Fb is compensated in accordance with the change of the incident angle i and the reflected angle α, but the sound pressure transmission rate database 11 and the sound pressure reflection rate database 12 have databases for each nozzle material. The database of the corresponding material is called to compensate for the energy intensity of the reflected echo Fb.

The compensation echo energy value of the reflected echo Fb obtained in this way is input to the crack evaluation means 15.
The crack evaluation means 15 calculates a crack area corresponding to the compensation echo energy value from the crack shape evaluation database 14 shown in FIG.

Further, the embodiment of the present invention is not limited to the evaluation of cracks generated in nozzle welds mounted near pipes of a boiler, but also includes cracks generated in socket welds of various pipes such as oil and gas. It can also be applied to the evaluation of

As described above, the features according to the embodiment of the present invention and the operation thereof are described again as follows.

In the boiler tube-side nozzle weld, the direction of crack propagation is affected by the direction and magnitude of the applied stress, and it is difficult to predict the inclination of the crack. The crack generated in the nozzle weld is characterized in that it starts from the partial penetration corresponding to the stress concentration part. Therefore, the ultrasonic wave is transmitted from the outer surface of the nozzle in two directions of the partial penetration portion and the fillet welding, and if the incident position of the ultrasonic wave is obtained by the reflection echo of the ultrasonic wave transmitted to the partial penetration portion, the transmission / reception element The angle of incidence and the angle of reflection of the ultrasonic wave that caused the reflected echo from the crack received by the method can be obtained.

Accordingly, the intensity of the reflected echo energy from the crack received by the transmitting / receiving element can be compensated by referring to the sound pressure transmission rate database and the sound pressure reflection rate database. In this manner, if the compensated energy intensity is known, the crack can be evaluated with high accuracy even if the inclination of the crack is unknown by comparing it with the crack shape reputation database.

[0044]

According to the present invention, the intensity of the reflected echo energy from the crack can be compensated even if the inclination of the crack generated in the fillet weld of the nozzle is unknown, so that a highly accurate crack evaluation is possible. Can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing an apparatus for evaluating a crack in a nozzle weld according to an embodiment of the present invention.

FIG. 2 is a view illustrating an example of an ultrasonic wave incident unit and a detecting unit according to the present invention, and is a diagram illustrating a propagation path of an ultrasonic wave in a nozzle weld portion where a crack has occurred.

FIG. 3 is a diagram showing a result of detection of a reflected echo by first and second detection means of the present invention.

FIG. 4 is a diagram illustrating a relationship between an incident angle of an ultrasonic wave and a sound pressure reciprocating passage rate in the sound pressure passage rate database of the present invention.

FIG. 5 is a diagram showing the relationship between the reflection angle of an ultrasonic wave incident wave and the sound pressure reciprocal reflectance in the sound pressure reflectance database of the present invention.

FIG. 6 is a diagram showing the relationship between the compensation energy intensity and the crack area in the crack evaluation means of the present invention in consideration of the influence of the incident angle and the reflection angle.

FIG. 7 is a diagram illustrating an operation principle of the probe according to the embodiment of the present invention.

FIG. 8 is a schematic view showing a conventional technique.

[Explanation of symbols]

1a Transmitting and receiving element for transmitting ultrasonic wave 2a to partial penetration portion 8 1b Transmitting and receiving element for transmitting ultrasonic wave 2b to fillet weld 6 Ultrasonic wave 2a ', 2b' Ultrasonic wave 3a First detecting means 3b Second detecting means 4 Pipe opening 5 Nozzle 6 Fillet weld 7 Crack 8 Partial penetration part 9 Incident position calculating means 10 Incident angle / reflection angle calculating means 11 Sound pressure transmittance database 12 Sound pressure reflectance database 13 Echo energy Compensation calculation means 14 Crack shape evaluation database 15 Crack evaluation means

Claims (2)

[Claims] 1. A probe that uses a first and a second transmitting / receiving element to transmit ultrasonic waves to a welded part of an inspection object from the same position in two directions and receive a reflected echo from the welded part. First detecting means for measuring reflected echoes from two directions obtained by the first and second transmitting / receiving elements, respectively;
Detecting means, an incident position calculating means for calculating a position at which an ultrasonic wave is incident on the body to be inspected, based on a propagation time of an incident reflection which is a measurement result from the first detecting means, and an incident position calculating means Incident angle / reflection angle calculating means for calculating an ultrasonic wave incident angle and a reflection angle of the second transmitting / receiving element based on an ultrasonic wave incident position from the apparatus and a propagation time of incident reflection which is a measurement result from the second detecting means; Echo energy compensating means for compensating the echo energy intensity obtained from the measurement result by the second detecting means with the sound pressure transmissivity from the sound pressure transmissivity database and the sound pressure reflectivity from the sound pressure reflectivity database And crack evaluation means for evaluating a crack based on the compensation echo energy from the echo energy compensation calculation means and the crack shape data from the crack evaluation database. prepare for,
A crack evaluation device for evaluating the size of a crack in a weld of a test object. 2. An ultrasonic probe for transmitting a ultrasonic wave to a fillet weld and detecting a crack in the fillet weld by a transmitting element for receiving a reflected echo, wherein the transmitting / receiving element comprises: A first transmitting / receiving element that transmits ultrasonic waves to a partial penetration portion that is a starting point of crack generation and is a butt surface of welding and receives a reflected echo from the partial penetration portion; An ultrasonic probe, comprising: a second transmitting / receiving element capable of transmitting a sound wave and receiving a reflected echo from a crack in the fillet weld.