JP3956486B2 - Method and apparatus for detecting thermal spray coating peeling on structure surface - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for detecting peeling of a sprayed coating formed on the surface of a structure such as a boiler furnace wall.
[0002]
[Prior art]
In order to improve wear resistance and the like, the furnace wall of a power generation boiler is usually provided with a metal spray coating on the surface.
[0003]
The sprayed coating has defects such as peeling and cracking due to secular change, and therefore needs to be inspected regularly. Therefore, conventionally, color check (immersion test) and visual inspection are performed.
[0004]
[Problems to be solved by the invention]
However, cracks in the thermal spray coating can be detected by color check or visual inspection, but in the case of peeling, since it is not a surface defect, it cannot be detected by color check. Although possible, detection of small delamination is extremely difficult.
[0005]
Therefore, the present invention is intended to provide a method and an apparatus for detecting a thermal spray coating peeling on the surface of a structure that can easily and reliably detect the thermal spray coating peeling that has been difficult to observe visually.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention places a receiving probe of an AE device on a sound part of a sprayed coating formed on the surface of a structure, and ultrasonic waves on the inspection portion of the sprayed coating. The transmitter for transmitting the oscillator is sequentially brought into contact with the ultrasonic oscillator to excite the thermal spray coating at the inspection position , and then the vibration propagating through the structure is received on the healthy part of the thermal spray coating. The vibration waveform is displayed on the display after being received by the AE device via the probe for the FFT, and the frequency of the waveform is subjected to FFT calculation. From the position of the peak frequency region of the waveform after the FFT calculation , A method and an apparatus for detecting a thermal spray coating peeling on the surface of a structure that detects the peeling portion by distinguishing the peeling portion from the healthy portion.
[0007]
When the portion where the thermal spray coating is peeled is vibrated, the vibration is less likely to be transmitted to the base material as compared with a healthy portion that is not peeled, and therefore the frequency of the received vibration has a higher frequency component. Therefore, the healthy part and the peeled part can be distinguished from the peak frequency position.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0009]
First, the basic principle of the present invention will be described. Generally, the natural period of a wave propagating through a structure (plate) is higher as the plate thickness is thinner. Therefore, if the thermal spray coating is not peeled off, it vibrates including the base material, and if it is peeled off, it is difficult to transmit to the base material, and a difference in vibration frequency appears when the two are compared.
[0010]
FIG. 1 shows an embodiment of a thermal spray coating detection apparatus for a structure surface according to the present invention based on the above basic principle. The thermal spray coating 2 formed on the surface of the structure 1 such as a boiler furnace wall. An ultrasonic oscillator (pulsar) 3 that makes the transmitting probe 3 a abut on the inspection position and vibrations generated and propagated by the operation of the ultrasonic oscillator 3 on the healthy portion of the thermal spray coating 2. The AE device 4 that is received through the receiving probe 4 a arranged, the display 5 such as an oscilloscope that displays the vibration waveform received by the AE device 4, and the waveform displayed on the display 5 It consists of a spectrum analyzer such as a spectrum ram analyzer or a personal computer that performs an FFT operation on the frequency. In addition, 2a shows the peeling part of the thermal spray coating 2. FIG. Reference numeral 7 denotes an amplifier such as a preamplifier.
[0011]
When detecting the presence or absence of the peeled portion 2a of the thermal spray coating 2 formed on the surface of the structure 1, the receiving probe 4a of the AE device 4 is placed on the healthy portion of the thermal spray coating 2, and an ultrasonic oscillator The three transmission probes 3a are sequentially brought into contact with the inspection portion. In this case, since it is not initially known whether or not the position where the receiving probe 4a is placed is a healthy part, it is necessary to perform several preliminary inspections. When the sprayed coating 2 is vibrated by the operation of the ultrasonic oscillator 3, the vibration propagated through the structure 1 is received by the AE device 4 and the vibration waveform is displayed on the display 5. Next, the frequency of the waveform is FFT-calculated by the frequency analyzer 6. As shown in FIG. 2 (a), the waveform after the FFT calculation has a peak frequency when it is from the peeled portion 2a as compared with a case from the sound portion as shown in FIG. 2 (b). Since the region is shifted to the high frequency side, the healthy part and the peeled part 2a can be distinguished.
[0012]
As described above, the presence or absence of the peeling portion 2a, which has been difficult to visually observe so far, can be determined based on the frequency level, and the detection of the peeling portion 2a can be easily performed.
[0013]
In the above embodiment, the case where the ultrasonic vibration is applied to the surface of the structure by the ultrasonic oscillator 3 and the vibration reception is performed by the AE device 4 has been described. Of course, various changes may be added without departing from the scope of the present invention.
[0014]
【Example】
Next, a description will be given of the result of performing the peeling detection by the pseudo AE method using a test piece.
[0015]
First, as a preliminary test, the present inventor used a SUS304 steel plate in order to grasp the characteristics of the frequency of waves transmitted through the plate due to the change in the plate thickness, and the plate thickness was 5 mm, 3 mm, 2 mm, 1 mm, 0.6 mm, respectively. The pseudo AE waveform when changing to 0.1 mm was measured. The obtained waveforms were as shown in FIGS. 3 (a), (b), (c), (d), (e), and (f). Next, graphs obtained by applying FFT to these are shown in FIGS. 4 (a), (b), (c), (d), (e), and (f). From these results, there was no difference due to the plate thickness in FIGS. 3 (a), (b), (c), (d), (e), and (f), but FIG. 4 (a) (b) after frequency analysis was performed. In (c), (d), (e), and (f), it was confirmed that the peak frequency region was shifted to the high frequency side as the plate thickness was reduced.
[0016]
Next, based on the above results, the results of measuring the pseudo waveform using a test piece in which metal was sprayed on the plate material and an exfoliation portion was artificially formed were shown in FIGS. 5 (a), (b), (c) and FIG. 6 (a) (b) (c). In this case, the receiving probe is fixed to a sound part without a peeling part, and two types of transmission pulses from the transmitting probe, 15 MHz and 500 KHz, are used, as shown in FIGS. As shown in 6 (a) and (b), it shows the result when it is transmitted from two different healthy parts and when it is transmitted from the peeling part as shown in FIGS. 5 (c) and 6 (c). is there. Next, when these waveforms were subjected to FFT and subjected to frequency analysis, the results shown in FIGS. 7 (A), (B), and (C) and FIGS. 8 (A), (B), and (C) were obtained. 5 (a) (b) (c) and FIG. 6 (b) (b) (c) and FIG. 7 (b) (b) (c) and FIG. 8 (b) (b) (c) From the comparison, it can be seen that the frequency when transmitted from the peeling portion is high.
[0017]
【The invention's effect】
As described above, according to the present invention, the receiving probe of the AE device is placed on the sound part of the sprayed coating formed on the surface of the structure, and the ultrasonic oscillator is placed on the inspection portion of the sprayed coating. The receiving probe is placed on the healthy part of the thermal spray coating, with the transmission probe in contact with each other and the ultrasonic oscillator operating to vibrate the thermal spray coating at the inspection position. The vibration waveform is displayed on the display after being received by the AE device via the probe , the frequency of the waveform is subjected to FFT calculation, and the thermal spray coating is peeled off from the position of the peak frequency region of the waveform after the FFT calculation. A method for detecting the peeling of the thermal spray coating on the surface of the structure that distinguishes between the healthy part and the healthy part, and a probe for transmitting the ultrasonic oscillator on the inspection portion of the thermal spray coating formed on the surface of the structure With the operation of the ultrasonic oscillator, The spray coating is vibrated, and the vibration generated by the operation of the ultrasonic oscillator and propagated through the structure is received by the AE device via the receiving probe disposed on the healthy portion of the spray coating. and so, further comprising: a display for displaying the oscillation waveform received by the AE device, Ri Na and a frequency analyzer for FFT calculating the frequency of the vibration waveform is displayed in the display unit, after the FFT operation to distinguish a release portion and a healthy section of the sprayed coating from the position of the peak frequency domain of the waveform, since the sprayed film peeling detecting device of a structure surface having a configuration which is adapted to detect the peeling unit, conventionally, even visually The presence or absence of peeling that has been difficult can be determined by the level of the frequency, and the excellent effect of easily performing the detection operation of the peeling portion is exhibited.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an embodiment of a thermal spray coating peeling detection apparatus on a structure surface according to the present invention.
FIG. 2 schematically shows a state after FFT calculation of a received wave, (A) shows a result when transmitted from a peeling portion, and (B) shows a result when transmitted from a healthy portion. FIG.
Fig. 3 shows the results of a preliminary test conducted in order to grasp the characteristics of the frequency due to the change in the plate thickness. (I) (b) (c) (d) (e) (f) It is a pseudo AE waveform diagram when changing to 3 mm, 2 mm, 1 mm, 0.6 mm, and 0.1 mm.
FIG. 4 shows a frequency spectrum of a pseudo AE waveform. (A), (b), (c), (d), (e), and (f) are respectively shown in FIGS. (E) It is a figure which shows the analysis result of the waveform shown to (f).
FIG. 5 shows a pseudo AE waveform measured using a test piece with a transmission pulse of 15 MHz. (A) shows a waveform when transmitted from a healthy part, and (B) is different from (A). The figure which shows the waveform at the time of transmitting from the sound part of a position, (c) is a figure which shows the waveform at the time of transmitting from a peeling part.
FIG. 6 shows a pseudo AE waveform measured using a test piece with a transmission pulse of 500 KHz. (A) shows a waveform when transmitted from a healthy part, and (b) is different from (a). The figure which shows the waveform at the time of transmitting from the sound part of a position, (c) is a figure which shows the waveform at the time of transmitting from a peeling part.
FIGS. 7A and 7B show the frequency spectrum of a pseudo AE waveform, and FIGS. 5A, 5B, and 5C show the analysis results of the waveforms shown in FIGS. 5A, 5B, and 5C, respectively.
FIG. 8 shows the frequency spectrum of a pseudo AE waveform, and (a), (b), and (c) show the analysis results of the waveforms shown in FIGS. 6 (a), (b), and (c), respectively.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Structure 2 Thermal spray coating 2a Peeling part 3 Ultrasonic oscillator 3a Transmitting probe 4 AE apparatus 4a Receiving probe 6 Frequency analysis apparatus

Claims (2)

The receiving probe of the AE device is placed on the sound part of the sprayed coating formed on the surface of the structure, and the transmitting probe of the ultrasonic oscillator is sequentially brought into contact with the inspection portion of the sprayed coating. Te vibrated the sprayed coating inspection position by operation of the ultrasonic oscillator, the vibration propagating through the time structure, is received by the AE device via the ultrasonic probe reception placed on healthy portion of said thermally sprayed coating comprising Then, the vibration waveform is displayed on the display, the frequency of the waveform is subjected to FFT calculation, and the peeling portion and the healthy portion of the sprayed coating are distinguished from the position of the peak frequency region of the waveform after the FFT calculation , A method for detecting a thermal spray coating delamination on a surface of a structure, wherein: An ultrasonic oscillator transmitting probe is brought into contact with an inspection portion of the thermal spray coating formed on the surface of the structure, and the thermal spray coating is vibrated by the operation of the ultrasonic oscillator. The vibration generated by the operation of the ultrasonic oscillator and propagated through the structure is received by the AE device via the receiving probe arranged on the sound part of the thermal spray coating, and further, the AE device spraying a display for displaying the received oscillation waveform, Ri Na and a frequency analyzer for FFT calculating the frequency of the vibration waveform is displayed in the display unit, the position of the peak frequency domain of the waveform after FFT operation A spray coating peeling detection device for a structure surface, characterized in that a peeling portion is detected by distinguishing a peeling portion and a healthy portion of a coating.

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