JP2000338092A - Method for ultrasonic inspection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a method for ultrasonic inspection capable of accurately measuring the length or flaw inspection. SOLUTION: A pulse-like transversal wave 4 having a vibrating direction coincident with a crystal growing direction ([001] direction) of a material 1 to be inspected is incident from one side 3 of a surface 2 to be inspected. In this case, the wave 4 is incident perpendicularly to a surface of the material 1. The wave 4 incident to the material 1 is propagated through the material 1, and arrives at another side 5 of the surface 2. The wave 4 arriving at the side 5 of the surface 2 is reflected at the side 5, propagated toward one side 3 of the incident position, and arrives at the one side 3 incident with the wave 4. Accordingly, a propagating time from when the wave 4 is incident from the one side 3 of the surface 2 to when the wave 4 is arrived at the one side 3 is measured, thereby measuring a thickness (=propagating time ×propagating speed) of the surface 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic inspection method for measuring and flaw-detecting an inspection object having directionality in crystal growth, such as a directionally solidified casting or a single crystal casting.

[0002]

2. Description of the Related Art Conventionally, a pulse reflection type ultrasonic inspection method has been used for measuring the thickness of a cast molded product and detecting flaws such as pitting corrosion. In this pulse reflection type ultrasonic inspection method, a pulse-like longitudinal ultrasonic wave generated by a probe is made incident from the surface of the inspection object, and the longitudinal ultrasonic wave is transmitted to a defect or an incident surface of the inspection object. The length measurement or flaw detection is performed by detecting and detecting longitudinal ultrasonic waves that are reflected at a boundary surface such as an end surface on the opposite side and are reflected back.

[0003] In recent years, materials having directionality in crystal growth, such as unidirectionally solidified castings or single crystal castings, are being used for hollow blade members of turbo fluid machines such as gas turbines. The hollow wing members made of these unidirectionally solidified castings or single crystal castings are manufactured while gradually lowering the mold in a furnace so as to control the progress of solidification so that the crystal growth direction matches the blade height direction. You. Therefore, the hollow wing member is held in the furnace in an unstable state in which the molten metal is filled in the mold for a long time, so that the core for forming the hollow portion moves and the thickness of the wing portion fluctuates. Sometimes. Therefore, it is extremely important for quality control of the hollow blade member to accurately perform nondestructive wall thickness measurement and flaw detection such as pitting corrosion.

[0004]

SUMMARY OF THE INVENTION According to the present invention, an ultrasonic wave is made incident on an object having directionality in crystal growth, and length measurement or flaw detection is performed with high accuracy based on the reflected ultrasonic wave. It is an object of the present invention to provide an ultrasonic inspection method capable of performing the method.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies on an ultrasonic inspection method capable of performing highly accurate measurement, and as a result, have newly found the following facts. An object to be inspected such as a one-way solidification casting or a single crystal casting has anisotropy depending on the crystal orientation, and is a plane perpendicular to the crystal growth direction when the crystal growth direction is the [001] direction (001). The crystal orientation on the plane differs for each crystal grain. Therefore, when the longitudinal ultrasonic wave is incident from the surface of the inspection object, the vibration direction of the crystal particles by the ultrasonic wave becomes parallel to the traveling direction of the ultrasonic wave, and the influence of the crystal anisotropy on the (001) plane. Will be greatly affected. On the other hand, the propagation velocity of longitudinal ultrasonic waves changes according to the magnitude of the Young's modulus. For example, the Young's modulus of a Ni-based superalloy used for a moving blade of a gas turbine is as shown in FIG. This shows the crystal orientation dependence. Therefore, due to such crystal orientation dependence of the Young's modulus, the propagation velocity changes according to the direction in which the longitudinal ultrasonic wave is incident, and the error included in the measured value increases. In the case of the above-described Ni-based superalloy, the propagation speed of the ultrasonic wave changes by an average value of about ± 15% when estimated from the amount of change in the Young's modulus. It has been found that it is difficult to perform length measurement and flaw detection with high accuracy on an inspection object having a directivity.

[0006] Based on the above research results, the ultrasonic inspection method according to the present invention according to the first aspect of the present invention applies ultrasonic waves to an object having directionality in crystal growth, and reflects the ultrasonic waves inside the object. An ultrasonic inspection method for measuring a distance to a position where the ultrasonic wave is reflected, based on the ultrasonic wave, wherein the object has a vibration direction that coincides with a crystal growth direction of the object. It is characterized in that a transverse ultrasonic wave is incident.

According to the ultrasonic inspection method of the first aspect, when a transverse ultrasonic wave having a vibration direction coinciding with the crystal growth direction is incident on the inspection object, the crystal particles vibrate in the crystal growth direction. The shear wave travels in the incident direction without being affected by the crystal anisotropy in a plane perpendicular to the crystal growth direction. Therefore, regardless of the direction in which the shear wave ultrasonic wave is incident, the shear wave ultrasonic wave propagates at a substantially constant sound speed, and the occurrence of a length measurement error due to a change in the propagation speed is extremely effectively suppressed.

The object to be inspected is a blade member of a turbo-type fluid machine, and it is preferable that a transverse ultrasonic wave having a vibration direction coinciding with the crystal growth direction is perpendicularly incident on the surface of the blade member. . In this way, by injecting a transverse ultrasonic wave into the wing member of the turbo type fluid machine perpendicularly to the surface, it is possible to accurately measure the thickness of the wing portion.

According to a third aspect of the present invention, there is provided an ultrasonic inspection method according to the present invention, in which an ultrasonic wave is made incident on a test object having directionality in crystal growth, and based on the ultrasonic wave reflected in the test object. An ultrasonic inspection method for flaw-detecting an object to be inspected, characterized in that a transverse ultrasonic wave having a vibration direction coinciding with a crystal growth direction of the object to be inspected is incident on the object to be inspected.

According to the ultrasonic inspection method of the third aspect, when a transverse ultrasonic wave having a vibration direction coinciding with the crystal growth direction is incident on the inspection object, the crystal particles vibrate in the crystal growth direction. The shear wave travels in the incident direction without being affected by the crystal anisotropy in a plane perpendicular to the crystal growth direction. Therefore, regardless of the direction in which the shear wave ultrasonic wave is incident, the shear wave ultrasonic wave propagates at a substantially constant sound speed, so that a flaw detection result such as the position of a defect includes an error due to a fluctuation in the propagation speed. Is extremely effectively suppressed.

Further, an ultrasonic probe for generating a transverse ultrasonic wave having a vibration direction coinciding with the crystal growth direction and a delay member having a convex surface are used. It is preferable that the shear wave ultrasonic wave is incident on the inspection object via the member. In this case, even when the surface of the object to be inspected has a concave shape, it becomes possible to accurately input the transverse ultrasonic waves in a desired direction.

[0012]

Embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

(First Embodiment) FIG. 1 is a conceptual diagram for explaining a first embodiment of an ultrasonic inspection method according to the present invention, and FIGS. 2 (a) and 2 (b) are diagrams according to the present invention. FIG. 2A shows an ultrasonic probe used in the first embodiment of the ultrasonic inspection method, and FIG. 2A is a longitudinal sectional view of the ultrasonic probe,
FIG. 2B is a cross-sectional view of the ultrasonic probe.

First, an outline of a method for measuring the thickness of an inspection object 1 made of a directionally solidified casting will be described with reference to FIG. As shown in the figure, the inspection object 1 is formed in a columnar shape, and a crystal grows in one direction of the [001] direction (Z-axis direction in the figure), and is perpendicular to the crystal growth direction ( The (001) surface is the inspection surface 2. A pulsed transverse ultrasonic wave 4 having a vibration direction coinciding with the crystal growth direction ([001] direction) of the test object 1 is incident on the test object 1 from one side 3 of the test surface 2. . At this time, shear wave ultrasonic wave 4
Is perpendicularly incident on the surface of the inspection object 1. The pulsed transverse ultrasonic wave 4 incident on the inspection object 1 propagates in the inspection object 1 and reaches the other side 5 of the inspection surface 2. The pulsed transverse ultrasonic wave 4 arriving at the other side 5 of the surface 2 to be inspected is reflected at the other side 5 and propagates toward the one side 3 on which the transverse ultrasonic wave 4 is incident. Reach side 3. Therefore, the propagation time from when the pulsed transverse ultrasonic wave 4 is incident from one side 3 of the surface 2 to be inspected to when the transverse ultrasonic wave 4 reflected on the other side 5 reaches the one side 3 is measured. Thus, the thickness (= propagation time × propagation speed) on the inspection surface 2 can be measured. Here, the propagation speed is set in advance as a transverse sound speed.

As shown in FIGS. 2A and 2B, an ultrasonic probe 10 for generating a pulsed transverse ultrasonic wave 4 is supported by a housing 11 and the housing 11. Y-cut vibrator 13 and convex delay member 1 to be brought into contact with inspection object 1
And 4. The ultrasonic probe 10 includes a connection cable 15
The vibration reducing member 12 is provided on the surface opposite to the surface from which the ultrasonic wave is emitted while being connected to the ultrasonic measuring device 20 via the. The ultrasonic measuring device 20 includes the ultrasonic probe 1
From the time when the pulsed shear wave ultrasonic wave 4 is emitted from 0 to the time when the reflected shear wave ultrasonic wave enters the ultrasonic probe 10, the thickness and the like of the inspection object 1 are calculated based on the time from Display the calculation result.

The Y-cut vibrator 13 oscillates in the direction of the arrow shown in FIG. 2 (b), applies a shear vibration parallel to the measurement surface of the test object 1, and applies a transverse wave to the test object 1. Ultrasonic waves are incident. By making the direction of the shear vibration coincide with the crystal growth direction ([001] direction) of the inspection object 1,
A transverse ultrasonic wave having a vibration direction coinciding with the crystal growth direction ([001] direction) of the test object 1 can be incident. The vibration reducing member 12 and the convex delay member 14 are made of an acrylic resin or the like, and the surface of the vibration reducing member 12 that is in contact with the Y-cut vibrator 13 is formed flat. Is formed in a convex shape (substantially semi-cylindrical shape) having a predetermined curvature.

FIG. 3 shows a procedure for measuring the wall thickness of a moving blade 30 of a gas turbine as an example of a hollow blade member made of a directionally solidified casting and applied to a turbo fluid machine. In this case, the ultrasonic probe 10 is in contact with the abdominal surface 31 of the moving blade 30. An arrow mark 16 indicating the vibration direction of the Y-cut transducer 13 is provided on the back surface of the housing 11 of the ultrasonic probe 10, and the direction of the arrow mark 16 and the crystal growth direction of the rotor blade 30 are determined. In the aligned state, the convex delay member 14 is brought into contact with the abdominal surface 31 of the rotor blade 30 from a direction perpendicular thereto.
In this state, a pulse-like transverse ultrasonic wave 4 is incident from the ultrasonic probe 10. The ultrasonic measuring device 20 measures the time from the emission of the pulsed transverse ultrasonic wave 4 until the reflected pulsed transverse ultrasonic wave enters the ultrasonic probe 10. The thickness of the moving blade 30 is calculated based on the calculated value.

FIG. 4A shows a result of comparing the measured value of the wall thickness of the moving blade 30 made of the one-way solidified casting with the actually measured wall thickness of the cut piece of the moving blade 30 by the above-described procedure. FIG. 4 (a)
As shown in the figure, since the error amount with respect to the actually measured value is ± 0.2 mm or less in the entire measurement range, the wall thickness is increased by using a transverse ultrasonic wave having a vibration direction coinciding with the crystal growth direction of the moving blade 30. By measuring, it can be confirmed that extremely high-precision measurement can be performed. On the other hand, when longitudinal ultrasonic waves are used, FIG.
As shown in (b), the error amount with respect to the actually measured value is about ± 10% of the actually measured value in the entire measurement range. FIG.
From FIG. 4A and FIG. 4B, when the longitudinal wave ultrasonic wave is used, the measurement error tends to increase as the thickness increases, whereas when the transverse wave ultrasonic wave is used, It can also be confirmed that stable measurement with little error can be performed regardless of the thickness.

As described above, the oscillation direction of the pulsed transverse ultrasonic wave 4 propagating in the inspection object 1 (the moving blade 30) is made to coincide with the crystal growth direction ([001] direction) of the inspection object 1. As a result, the crystal grains of the test object 1 vibrate in the crystal growth direction, and the pulsed transverse ultrasonic waves 4 are not affected by the crystal anisotropy in a plane perpendicular to the crystal growth direction. (The moving blade 30). Therefore, regardless of the direction in which the transverse ultrasonic wave 4 is incident, the pulse-like transverse ultrasonic wave 4 propagates at a substantially constant sound velocity, and the occurrence of a length measurement error due to fluctuations in the propagation velocity is suppressed. As a result, extremely accurate length measurement can be performed.

Further, the vibration direction of the Y-cut vibrator 13
If the convex delay member 14 is brought into contact with a direction perpendicular to the abdominal surface 31 of the moving blade 30 in a state where the crystal growth direction of the moving blade 30 is made to coincide with the direction of crystal growth, It is possible to accurately measure the wall thickness of the moving blade 30 by applying a transverse ultrasonic wave to the moving blade 30.

The surface of the convex delay member 14 which comes into contact with the moving blade 30 is a convex (approximately semi-cylindrical) having a predetermined curvature.
Therefore, even when the surface of the object to be inspected has a concave shape, such as the abdominal surface 31 of the rotor blade 30, it is possible to make the transverse ultrasonic waves accurately incident in a desired direction. Become.

(Second Embodiment) FIG. 5 is a conceptual diagram for explaining a second embodiment of the ultrasonic inspection method according to the present invention.

With reference to FIG. 4, a method of detecting a flaw 50 such as a minute pit in the inspection object 41 made of a unidirectionally solidified casting will be described. Inspection object 41
Is formed in a columnar shape as in the first embodiment, and [00]
The crystal grows in one direction (Z-axis direction in the drawing), and the (001) plane perpendicular to the crystal growth direction is the inspection surface 42. A pulse-like transverse ultrasonic wave 44 having a vibration direction coinciding with the crystal growth direction ([001] direction) of the test object 41 is incident on the test object 41 from one side 43 of the test surface 42. Let it. At this time, the shear wave ultrasonic wave 44 is perpendicularly incident on the surface of the inspection object 41.
The pulsed transverse ultrasonic wave 44 incident on the inspection object 41 is
The light propagates inside the inspection object 41. As shown in FIG. 5, when the defect 50 exists in the inspection object 41, the pulse-like transverse ultrasonic wave 44 is reflected at the boundary surface with the defect 50, and the transverse ultrasonic wave 44 is incident. The light propagates toward the side 43 and reaches one side 43 which is the incident position. Therefore, by measuring the propagation time from the time when the pulsed ultrasonic wave 44 is incident from one side 43 of the surface 42 to be inspected to the time when the ultrasonic wave 44 is reflected by the defect portion 50 and reaches the one side 43, the inspection is performed. The presence or absence of the defect 50 on the surface 42 and the distance to the defect 50 (= propagation time × propagation speed) can be measured. here,
The propagation speed is set in advance as a transverse sound speed.

As described above, the vibration direction of the pulsed transverse ultrasonic wave 44 propagating in the inspection object 41 is made to coincide with the crystal growth direction ([001] direction) of the inspection object 41, so that the inspection object The crystal grains of 41 vibrate in the crystal growth direction,
The pulsed shear wave ultrasonic wave 44 is not affected by the crystal anisotropy in a plane perpendicular to the crystal growth direction, and
Propagating within 1. Therefore, regardless of the direction in which the shear wave ultrasonic wave 44 is incident, the pulse-like shear wave ultrasonic wave 44 propagates at a substantially constant sound speed, and the flaw detection result such as the presence or absence of the defect 50 or the distance to the defect 50 is not obtained. It is suppressed that an error due to the fluctuation of the propagation speed is included. As a result, extremely high-precision flaw detection can be performed.

In the first and second embodiments,
Although an example of measuring or inspecting the inspection objects 1 and 41 made of a unidirectionally solidified casting has been described, the inspection object is not limited to these, and may be, for example, a single crystal casting, and may be in the crystal growth direction. Various materials can be used as inspection objects as long as they have directionality.

Further, the shape of the convex delay member 14 of the ultrasonic probe 10 included in the first embodiment is not limited to the above-described one, and the surface to be brought into contact with the inspection object has a predetermined curvature. It may have a spherical shape.

[0027]

As described in detail above, claim 1 is as follows.
According to the present invention described in the above, by applying a transverse ultrasonic wave having a vibration direction coinciding with the crystal growth direction to the inspection object, the crystal particles vibrate in the crystal growth direction, and in a plane perpendicular to the crystal growth direction. Without being affected by the crystal anisotropy of
The shear wave ultrasonic waves travel in the incident direction. Therefore, the shear wave propagates at a substantially constant sound speed, and the occurrence of a length measurement error due to a fluctuation in the propagation speed is suppressed, so that highly accurate length measurement can be performed.

According to the third aspect of the present invention,
When a transverse ultrasonic wave having a vibration direction coinciding with the crystal growth direction is applied to the object to be inspected, the crystal grains vibrate in the crystal growth direction and are affected by the crystal anisotropy in a plane perpendicular to the crystal growth direction. Instead, the shear wave travels in the incident direction.
Therefore, the shear wave ultrasonic wave propagates at a substantially constant sound velocity, and errors due to fluctuations in propagation speed in a flaw detection result such as the position of a defective portion are suppressed, and high-precision flaw detection can be performed. .

[Brief description of the drawings]

FIG. 1 is a conceptual diagram for describing a first embodiment of an ultrasonic inspection method according to the present invention.

FIG. 2 shows an ultrasonic probe used in a first embodiment of the ultrasonic inspection method according to the present invention, wherein (a) is a longitudinal sectional view of the ultrasonic probe, and (b) is an ultrasonic probe. FIG.

FIG. 3 is an explanatory diagram showing an example in which the first embodiment of the ultrasonic inspection method according to the present invention is applied to measurement of the thickness of a hollow wing member.

FIG. 4A is a table showing measurement results when a transverse ultrasonic wave is incident on a hollow blade member made of a unidirectionally solidified casting,
(B) is a table showing measurement results when longitudinal ultrasonic waves are incident on a hollow blade member made of a unidirectionally solidified casting.

FIG. 5 is a conceptual diagram illustrating a second embodiment of the ultrasonic inspection method according to the present invention.

FIG. 6 is a table showing a relationship between a crystal orientation and a Young's modulus in a Ni-based superalloy.

[Explanation of symbols]

1, 41: inspected object, 2, 42: inspected surface, 4: transverse ultrasonic wave, 10: ultrasonic probe, 11: housing, 12: vibration reducing member, 13: Y-cut vibrator, 14 ... Convex delay member,
Reference numeral 15: connection cable, 16: arrow mark, 20: ultrasonic measuring instrument, 30: blade, 31: abdominal surface, 50: defective part.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F068 AA28 AA48 BB08 BB21 CC00 CC04 FF03 FF12 FF14 FF16 FF25 GG01 HH02 KK01 KK13 LL02 LL22 2G047 AA07 AC05 BA03 BC02 BC07 BC18 CB01 CB02 EA17 GB22 GF06 GF10

Claims (4)

[Claims] An ultrasonic wave is incident on an object having directionality in crystal growth, and a distance to a position where the ultrasonic wave is reflected is determined based on the ultrasonic wave reflected in the object. An ultrasonic inspection method, comprising: applying a transverse ultrasonic wave having a vibration direction coinciding with a crystal growth direction of the inspection object to the inspection object. . 2. The object to be inspected is a wing member of a turbo-type fluid machine, and a transverse ultrasonic wave having a vibration direction coinciding with the crystal growth direction is perpendicularly incident on a surface of the wing member. The ultrasonic inspection method according to claim 1, wherein: 3. An ultrasonic inspection method for irradiating an ultrasonic wave to an inspection object having directionality in crystal growth, and detecting the inspection object based on the ultrasonic wave reflected in the inspection object. An ultrasonic inspection method, wherein a transverse ultrasonic wave having a vibration direction coinciding with a crystal growth direction of the inspection object is incident on the inspection object. 4. An ultrasonic probe for generating a transverse ultrasonic wave having a vibration direction coinciding with the crystal growth direction, and a delay member having a convex surface, wherein the convex surface is brought into contact with the inspection object. The ultrasonic inspection method according to any one of claims 1 to 3, wherein a transverse ultrasonic wave is made incident on the inspection object via the delay member.