JPH02108908A - Measuring method for thickness of body to be measured with coating - Google Patents

Abstract

PURPOSE:To securely lead out a border surface reflected wave required to measure the thickness of the body to be measured by receiving a surface reflected wave and the border surface reflected wave by a 1st transmission-side member. CONSTITUTION:An ultrasonic probe 2 is constituted by arranging a transmission member (1st member) 5 which has a transmission and reception function for ultrasonic wave pulses and a receiving member (2nd member) 6 successively in a case 4 and also arranging an acoustic partition plate 7 between the both. An ultrasonic wave pulse generator 21 generates an ultrasonic wave pulse generation signal to send ultrasonic wave pulses out of the member 5. Some of the ultrasonic wave pulses are reflected by the surface of the coating 9 first. The surface reflected wave is cut off by the partition plate 7, hardly propagated to the member 6, and received mainly by the member 5. Some of ultrasonic wave pulses passed through the coating 9 are reflected by the border surface between the coating 9 and body 10 to be measured and the majority of them are received by the member 5 as well as the surface reflected wave. Consequently, the reception level of the border surface reflected wave is large and the signal can securely be extracted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a thickness measuring method for measuring the true thickness of a coated object from above the coating.

[Prior Art] When measuring the thickness of a coated object such as a steel plate, the general method is to peel off the coating and then measure using an appropriate thickness measuring device. However, since removing the coating and repainting it is a very time-consuming task, various means have been considered in the past that can measure the object to be measured with the coating still attached.

For example, the thickness measuring device shown in FIG. 5 measures the thickness of the object to be measured using the reflection of ultrasonic pulses, and includes an ultrasonic probe 2 that is brought into close contact with the coated object 1, and ,
The ultrasonic probe 2 used in this device is a so-called split type, and is a cylindrical type. A case 4 includes an ultrasonic pulse transmitting member 5 and a receiving member 6 arranged in parallel with each other. An acoustic partition plate 7 is provided between the transmitting member 5 and the receiving member 6 to prevent the ultrasonic pulses from directly propagating from the transmitting member 5 to the receiving member 6, and this partition plate 7 extends to the opening surface of the case 4. ing. Further, the case 4 is filled with a delay material 8. Such an ultrasonic probe 2 is used by bringing its end face into close contact with the surface of the coated object to be measured 1, and when an ultrasonic pulse is emitted from the transmitting member 5, the pulse is transmitted to the coated object to be measured 10. These reflected waves are received by the receiving member 6, and the received signal is sent to the thickness measuring device 3. Then, using the signals of the boundary surface reflected wave and the bottom surface reflected wave, the thickness of the plate is calculated in the thickness measuring device 3 from the difference in reception time.

Further, as another method, there is a so-called B, -82 method that utilizes multiple reflected waves of bottom surface reflected waves. This B, -82
The method, as shown in FIG.
A part of the bottom surface reflected wave is reflected without passing through the interface between the coating and the object to be measured 10 and is reflected again at the bottom surface of the object to be measured 10 (second bottom surface reflected wave). This method calculates the plate thickness by measuring the difference in reception times.

[Problems to be Solved by the Invention] However, the conventional thickness measuring method described above has the following problems.

First, in a method using reflected waves from the boundary surface and the bottom surface, the acoustic partition plate 7 of the ultrasonic probe 2 is
Since the interface is in contact with the surface of the interface, there is a problem that the reception level of the interface reflected wave is low and measurement errors are likely to occur. In other words, significant amplification is required to extract the signal due to the boundary surface reflected wave, and the error caused by the amplification may not be negligible. (including multiple reflected waves, surface reflected waves, etc.) is also easier to pick up. Therefore, especially when the coating is thin, it is difficult to select and reliably extract signals due to interface reflected waves, and it is difficult to accurately determine the true thickness of the object to be measured 10.

On the other hand, in the B and -B2 methods, the above-mentioned problems associated with extracting the interface reflected waves do not occur, but when there is a corroded part 11 on the bottom surface of the coated object 1 as shown in FIG. Depending on the conditions, the signal f2 due to the reflected wave from the corroded part 11, its multiple reflected wave f2, and the bottom surface reflected wave signal B are mixed in the signal output from the receiving member 6, and it is not possible to distinguish between them. It becomes impossible to accurately measure the thickness of the measurement object 10.

Therefore, an object of the present invention is to solve such problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a first member capable of transmitting and receiving ultrasonic pulses, and a second member capable of receiving at least ultrasonic pulses. A thickness measuring method in which the thickness of only the coated object to be measured is measured using split-type ultrasonic probes arranged in parallel with an acoustic partition plate in between. The first member of the sonic probe emits an ultrasonic pulse, and the first member receives a surface reflected wave from the coating surface and an interface reflected wave from the interface between the coating and the object to be measured. Then, only the signal of the boundary surface reflected wave is extracted from the signal received by the first member and used as a timing start signal, and on the other hand, the second member of the ultrasonic probe detects the signal from the bottom surface of the object to be measured. It is characterized in that the bottom reflected wave is received as a clock stop signal, and the thickness of the object to be measured is calculated from the clock start signal and the clock stop signal.

[Function] According to the present invention, by receiving the surface reflected waves and the boundary surface reflected waves by the first member on the transmitting side, the reception level of these reflected waves becomes high, and it is possible to measure the thickness of the object to be measured. It is possible to reliably collect the necessary boundary surface reflected waves.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings, in which the same reference numerals are used for the same or corresponding parts.

FIG. 1 of the drawings shows an example of an apparatus for carrying out the measuring method of the present invention. Reference numeral 2 designates a conventionally commonly used split-type ultrasonic probe, which consists of a transmitting member (first member) 5 that emits ultrasonic pulses and a receiving member (second member) 6 that receives the ultrasonic pulses. Normally, these members 5.
6 consists of what is called a vibrator, and has both transmitting and receiving functions. In the present invention, the circuit configuration is such that the transmitting member 5 transmits and receives ultrasonic pulses.6 In the following description, the transmitting member will be referred to as a transmitting/receiving member. Further, reference numeral 20 is a thickness measuring device connected to the ultrasonic probe 2.

When measuring the thickness of the coated object to be measured 1 using such an apparatus, first, a couplant such as glycerin is applied to the surface of the coating 9, and the opening surface of the ultrasonic probe 2 is brought into close contact with the surface of the coating 9.

The transmitting/receiving member 5 of the ultrasonic probe 2 is connected to the ultrasonic pulse generator 21 of the thickness measuring device 20, and this ultrasonic pulse generator 21 receives rectangular pulses of a constant period from the original oscillator 22. An ultrasonic pulse generation signal is generated, and the ultrasonic pulse is transmitted from the transmitting/receiving member 5 at a constant period. A part of the ultrasonic pulse emitted from the transmitting/receiving member 5 is
First, it is reflected by the surface of the coating 9. This surface reflected wave is blocked by the acoustic partition plate 7, hardly propagates to the receiving member 6, and is mainly received by the transmitting/receiving member 5.

Further, a part of the ultrasonic pulse that has passed through the coating 9 is reflected at the interface between the coating 9 and the object to be measured 10, and most of the waves reflected from the interface are received by the transmitting/receiving member 5 like the surface reflected waves. The signal ■ from the transmitting/receiving member 5 which received the 0 surface reflection q (wave and the boundary surface reflected wave) is sent to the thickness measuring device 20.
(Fig. 2) 8 In the surface reflected wave amplifier 23, an auto gain control voltage (a constant negative voltage in this embodiment) is added to the signal (2) by the auto gain control 24. The signal 0 is adjusted to an appropriate level as shown in FIG.

The boundary surface reflected wave selector 25 receives a gate signal 2 preset as shown in FIG. is output (Fig. 2 ■),
Then, in the level setting circuit 27, a signal exceeding the level setting value (Fig. 2), that is, a signal ■ corresponding to the boundary surface reflected wave.
Based on this signal ■, a timing start signal ■ for plate thickness measurement is sent to the signal generating circuit 28 to star 1.
It is formed by (Fig. 2 ■1 ■).

The other part of the ultrasonic pulse emitted from the transmitting/receiving member 5 propagates through the coating 9 and the object to be measured 10 and is reflected at the bottom surface of the object to be measured 10, and the bottom reflected wave is received by the receiving member 6. Ru. This received signal [F] passes through the bottom reflected wave amplifier 29 of the thickness measuring instrument ZO, is adjusted by the auto gain control 30, and is then input to the bottom reflected wave selector 31 (Fig. 2 ■, ■). , signal■
is converted into a signal 0 by the gate signal [share] from the selector gate circuit 32 in the bottom reflected wave selector 31 (Fig. 2 [phase], ■), and the level setting circuit 33 converts it into a signal 0 (Fig. 2 [phase], ■). ), the signal [phase] corresponding to the bottom surface reflected wave is extracted (No. 21"J@). After this, the signal ■ is output as the timing stop signal ■ by the stop signal generation circuit 34 (Fig. 2 ■) .

The timing start signal ■ and the timing stop signal ■ are input to the flip-flop circuit 35, and the flip-flop circuit 35
7J' and the like output a signal (2) corresponding to the time from the reception time of the boundary surface reflected wave to the reception time of the bottom surface reflection wave, as understood from FIG. 2 (2).

The true thickness of the object to be measured 10 is calculated by counting this in the timing/arithmetic circuit 36 and performing arithmetic processing based on the propagation velocity of the ultrasonic wave in the object to be measured 10, and that value is used as the measured value. It is displayed on the display section 37.

FIG. 3 is an oscilloscope photograph showing the waveforms of the received signal at the transmitting/receiving member 5 and the receiving signal at the receiving member 6 when thickness measurement according to the present invention is performed using an ultrasonic probe having broadband characteristics. be.

Here, the broadband ultrasonic probe refers to a probe with a reflected wave peak number of up to about 4 and a wide bandwidth of the frequency spectrum of the reflected wave. This is an oscilloscope photograph taken using a narrowband ultrasound probe under the same conditions as in the figure. As can be seen by comparing Figures 3 and 4, the former has good resolution of the surface reflected wave and the boundary surface reflected wave, but the voltage of the response output of the bottom reflected wave is small and requires large amplification. On the other hand, the latter narrow-band ultrasonic probe has a characteristic that the resolution of the surface reflected wave and the boundary surface reflected wave is poor, and the response output of the bottom surface reflected wave is large.

Although the present invention can be carried out using any of the ultrasonic probes, each has its advantages and disadvantages. In order to do this, in the ultrasonic probe 2, the transmitting/receiving member 5 and the damper 40 on the back side thereof shall have broadband characteristics, and the receiving member 6 and the damper 41 on the back side thereof shall have narrow band characteristics. is preferable.

[Effects of the Invention] As described above, according to the present invention, since the boundary surface reflected waves are received by the transmitting side member of the segmented ultrasonic probe, the reception level of the boundary surface reflected waves can be increased. , the signal can be reliably extracted. Therefore, it is possible to accurately measure the true thickness of the object to be measured without coating from the boundary surface reflected wave and the bottom surface reflected wave. Also, B
There is no measurement error due to corrosion of the measured object as seen in the +B- method.Furthermore, in the past, in order to separate and extract the signals of various reflected waves received by the receiving member, coating, measuring It was necessary to select the type of ultrasonic probe depending on the thickness of the object and the delay material, the ultrasonic propagation velocity of each, etc., but in the present invention, the type of ultrasonic probe can be selected depending on the thickness of the object and the delay material, the ultrasonic propagation velocity of each, etc., but in the present invention, the type of ultrasonic probe Since the signals are received separately, the signal can be easily extracted, and one type of ultrasonic probe can be used for various types of objects to be measured.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing an example of a thickness measuring device for carrying out the thickness measuring method according to the present invention, FIG. 2 is a waveform explanatory diagram showing the waveforms of each output signal in FIG. 1, and FIG. Figure 4 is an oscilloscope photograph showing the waveform of the received signal at the transmitting/receiving member and the receiving member when an ultrasonic probe with broadband characteristics is used, and Figure 4 is an image when an ultrasonic probe with narrowband characteristics is used. A photograph of an oscilloscope showing the waveform of the received signal at the transmitting/receiving member and the receiving member, FIG. 5 is a schematic explanatory diagram showing a conventional general thickness measuring device, and FIGS.
Figure B is a schematic explanatory diagram showing thickness measurement using the -82 method. 5
... Transmitting/receiving member (first member) 6... Receiving member (second member) 9... Coating 10... Measured object patent applicant Toyo Kanetsu Co., Ltd. Same as above Japan Probe Co., Ltd. Figure 1 Broom diagram (YC 1) Child 3 Figure Horse 4 Figure also 2nd section H quantity 2) Figure root

Claims (1)

[Claims] A split-type ultrasonic probe in which a first member capable of transmitting and receiving ultrasonic pulses and a second member capable of receiving at least ultrasonic pulses are arranged in parallel across an acoustic partition plate. A thickness measuring method for measuring the thickness of only the coated object to be measured using a method, in which an ultrasonic pulse is emitted from the first member of the ultrasonic probe, and the thickness of the coated object is measured by A surface reflected wave and an interface reflected wave from the interface between the coating and the object to be measured are received by the first member, and only the signal of the interface reflected wave is selected from the signals received by the first member. is taken out as a timing start signal, and on the other hand, the second member of the ultrasonic probe receives a bottom surface reflected wave from the bottom surface of the object to be measured as a timing stop signal, and the timing start signal and the timing stop signal are obtained. A method for measuring the thickness of a coated object to be measured, characterized in that the thickness of the object to be measured is calculated from .