JPH04204143A - Method and apparatus for discriminating crack in shaft surface with laser - Google Patents

Abstract

PURPOSE:To enhance the detecting accuracy of the defect of a crack and to make it possible to perform highly reliable preventive maintenance by scanning a crack recognizing point with a semiconductor laser beam, casting the laser beam with the focal point being focused, and detecting the reflected beam. CONSTITUTION:When the presence or absence of a crack on the shaft surface of the water feeding boiler pump which is a body to be measured 10 is detected by an image processing, the point (the recognized defective part) is scanned with a semiconductor laser 4. The laser beam of the laser 4, which is focused with a focusing lens 7 of a laser-beam emitting device 2, is emitted. The change in reflection intensity is measured with a CCD photodiode array 9 of a detecting device 3 at a relative position. The output is inputted into a microcomputer through an A/D converter. In this computer, discriminating values are stored as databases for judging flaws and cracks beforehand. The input value is compared with the discriminating value, and whether the defect at the point is the fatigue crack or a simple flaw is discriminated.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a preventive maintenance system for a shaft, which is the most important part of a rotating machine. The present invention relates to a method and apparatus for determining shaft surface cracks using a laser, which are suitable for quickly and highly accurately determining whether they are scratches or not.

[Prior Art] A shaft is the most important component in a rotating machine, and maintenance must be performed reliably. For example, in boiler feed pumps delivered as part of existing thermal power generation equipment, fatigue cracks that occur due to material deterioration due to aging and harsher operation must be detected early and preventive maintenance must be carried out.

Conventional technology used to detect surface cracks on shafts was a two-dimensional surface crack tissue processing device using an optical microscope, CCD camera, and image processing device, but It is desired to develop a highly reliable non-destructive testing system to improve accuracy.

[Problems to be Solved by the Invention] Since the above-mentioned conventional technology is an inspection device using an optical microscope, a CCD camera, and an image processing device, it is a detection system using two-dimensional planar processing. therefore,
Even when a defect is detected, it is difficult to distinguish between a fatigue crack and a simple flaw, and the detection accuracy is insufficient.

The present invention was made in order to solve the problems of the conventional technology described above, and makes it possible to distinguish between fatigue cracks and simple scratches, improve the detection accuracy of crack defects, and enable highly reliable preventive maintenance. It is an object of the present invention to provide a method and apparatus for determining shaft surface cracks using a laser.

[Means for Solving the Problems] In order to achieve the above object, the structure of the shaft surface crack determination method using a laser beam according to the present invention is to The crack recognition point is scanned with a semiconductor laser beam, the laser beam is focused and irradiated, the laser beam reflected from the crack recognition point is detected, and the intensity of the laser reflection is detected as a change in the output voltage signal. By computer processing that is input into a computer and compared with a preset discrimination value, it is determined whether the crack at the crack recognition point is a fatigue crack or a simple flaw.

In addition, in order to achieve the above object, the structure of the shaft surface crack determination device using a laser beam according to the present invention irradiates the crack recognition point with respect to the recognized surface crack of the shaft of a one-rotation machine. a semiconductor laser driving device; a laser beam injection device that scans the crack recognition point and focuses the laser beam to irradiate the laser beam; and a laser beam that is located relative to the injection device and is reflected from the crack recognition point. A detection device detects the reflected intensity of the laser beam and compares the output voltage signal of the reflected intensity of the laser beam with a preset discrimination value to determine whether the crack at the crack recognition point is a fatigue crack or a simple scratch. The system is equipped with a computer processing device that determines the

Additionally, in order to achieve the above object, the present invention includes a semiconductor laser and an optical system (especially a focusing lens) for adjusting the laser beam on the input device side, and a focusing lens on the relative position detection device side. A CCD photodiode array is provided. Also, CC
In order to discriminate between cracks and flaws based on the output voltage from the D photodiode array, a microcomputer is provided to make a quantitative judgment.

[Action Co. The working of the above technical means is as follows.

After detecting surface defects (cracks) on the shaft of a rotating machine using image processing using conventional technology, a semiconductor laser is scanned over the recognized surface cracks (hereinafter referred to as points).

A point is irradiated with a laser beam from a semiconductor laser focused by the focusing lens of the input device, and the CC of the detection device located in the relative position is used to observe how the reflected intensity changes.
Measured with a D photodiode array.

The output is then input to the microcomputer through the A/D converter. The microcomputer has
Discrimination values are input and stored in advance as a database for determining flaws and tears. The amount of change in laser reflection intensity is compared with a discrimination value (set value) to determine whether the defect at the point is a fatigue crack or a simple scratch.

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2 as an example of a crack discrimination processing device for detecting damage to the shaft of a boiler feed pump, which is a rotating machine of a thermal power generation machine. explain.

FIG. 1 is a schematic configuration diagram of a detection section of a shaft surface crack determination apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a processing section of the apparatus of FIG. 1.

In Figs. 1 and 2, 1 is an inspection stand, 2a is an incident-side mount placed on the detection stand 1 at a certain angle to the surface of the object to be measured 10 (shaft), and 3a is the incident side mount placed on the detection stand 1. This is a detection side mount placed at a position relative to the side.

4 is a semiconductor laser, 5 is a beam expander to reduce the spread angle of the laser beam, 6 is an anamorphic prism that corrects the laser beam to make it nearly perfect circle, and 7 is a focusing lens. These optical systems, which are focusing lenses, are arranged on an incident-side pedestal 2a to constitute a laser beam incident device 2.

Further, 8 is a focusing lens that narrows down the laser beam reflected from the surface of the object to be measured 10 (shaft), and 9 is a CCD photodiode array that converts the strength of the reflected intensity into a voltage and outputs it, and these are on the detection side. A detection device 3 is arranged on a pedestal 3a to detect the reflected intensity of the laser beam.

Note that here, CCD is a charge coupled device, a charge coupled device (Charge Coupled D
evice).

The axis of the laser beam injection device 2, that is, the optical axis of the laser beam incident light, is arranged so as to maintain a certain angle of incidence with respect to the surface of the object to be measured 10. On the other hand, the axis of the detection device 3 located in the relative position, that is, the optical axis R of the reflected light of the laser beam, is arranged so as to maintain a reflection angle equal to the incident angle with respect to the surface of the object to be measured 10. Here, the angle of incidence and the angle of reflection range from 25 to 35 as shown in the figure.

16 shown in FIG. 2 is a semiconductor laser driving device, and 11 is a C
CD photodiode array driver (hereinafter simply referred to as COD)
(referred to as a drive device), 12 is an A/D converter, 13 is
A microcomputer 14 is a storage unit that inputs and stores a database for determining cracks and flaws, and a display unit 15 outputs determination results.

Next, a method for determining cracks on the shaft surface of a rotating machine will be described.

Assume that there is a defect on the shaft surface of the boiler feed pump related to the object to be measured 10.

The presence or absence of cracks is detected by conventional image processing.

This recognized defective portion, that is, the crack recognition point is hereinafter referred to as a point. A semiconductor laser is scanned at that point.

The semiconductor laser 4 is driven by the semiconductor laser driving device 16, the spread of the beam is adjusted through the beam expander 5, the laser beam is corrected to a nearly perfect circle through the anamorphic prism 6, and the laser beam is focused through the focusing lens 7. Emits light in a focused manner.

The laser beam reflected and scattered thereby is focused on a CCD photodiode array 9 by a focusing lens 8, and the intensity of the reflected beam is converted into a voltage and output.

In the processing section shown in FIG. 2, the output signal of each channel from the CCD drive device 11 is inputted to the microcomputer 13 through the A/D converter 12, and the output form is analyzed in the microcomputer 13, and the point defect is detected. It is determined whether it is a fatigue crack or a simple flaw and it is displayed on the display section 15.

As an analysis method, the microcomputer 13
The storage unit 14 stores crack data and flaw data as a database and sets determination values. Then, as described above, the output value of the reflected intensity of the laser beam and the discrimination value are compared to make the discrimination.

In this way, the laser-based shaft surface crack determination device of this embodiment can detect the recognized shaft surface crack-like defect by
It is possible to determine whether it is a fatigue crack or a simple flaw, which has the effect of increasing the accuracy of detecting crack defects.

Furthermore, by changing the judgment value or changing the method of focusing on the object to be measured, the method can also be used to detect defective corrosion (pits, etc.) other than cracks.

[Effects of the Invention] As explained in detail above, according to the present invention, it is possible to distinguish between fatigue cracks and simple scratches, improve the detection accuracy of crack defects, and enable highly reliable preventive maintenance. A method and apparatus for determining shaft surface cracks using a laser can be provided.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a detection section of a shaft surface crack determination apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a processing section of the apparatus of FIG. 1. 2... Laser beam incidence device, 3... Detection device. 4... Semiconductor laser, 5... Beam expander,
6... Anamorphic prism, 7, 8... Focusing lens, 9... CCD photodiode array, 1o... Measured object, 11... CCD drive device, 12... A/D Converter, 13... Microcomputer, 14... Storage section, 15... Display section, 1
6... Semiconductor laser drive device.

Claims (1)

[Claims] 1. Scanning a semiconductor laser beam at the crack recognition point for a recognized surface crack in the shaft of a rotating machine,
The laser beam is focused and irradiated, the laser beam reflected from the crack recognition point is detected, the strength of the laser reflection intensity is input to the microcomputer as a change in the output voltage signal, and compared with a preset discrimination value. A method for determining a shaft surface crack using a laser, the method comprising: determining whether the crack at the crack recognition point is a fatigue crack or a simple scratch through computer processing. 2. A semiconductor laser drive device that irradiates the detected surface crack on the shaft of a rotating machine at the crack recognition point, and a laser that scans the crack recognition point and focuses the laser beam to irradiate it. a beam injection device; a detection device located relative to the injection device for detecting the reflection intensity of the laser beam reflected from the crack recognition point; and an output voltage signal of the reflection intensity of the laser beam set in advance. 1. A shaft surface crack discriminating device using a laser, comprising: a computer processing device that compares the discriminant value with the determined discriminant value to determine whether the crack at the crack recognition point is a fatigue crack or a simple flaw. 3. The laser beam injection device includes a beam expander that adjusts the spread of the semiconductor laser beam, an anamorphic prism that corrects the laser beam to a nearly perfect circle, and a laser beam that focuses the laser beam on the crack recognition point. 3. The shaft surface crack determination device using a laser according to claim 2, further comprising a focusing lens. 4. The detection device that detects the reflected intensity of the laser beam consists of a focusing lens that focuses the laser beam reflected from the crack recognition point on the shaft surface, and a CCD photodiode array that converts the intensity of the reflected intensity into voltage and outputs it. A shaft surface crack determination device using a laser according to claim 2, characterized in that the device comprises: 5. The computer processing device has a storage unit that records discrimination data for determining whether it is a fatigue crack or a simple flaw, and compares the intensity change of the laser beam input from the CCD photodiode array through the A/D converter with the discrimination value. 3. The apparatus for determining shaft surface cracks using a laser according to claim 2, further comprising an arithmetic unit for determining and a display unit for outputting the determination result.