JP2003279547A - Non-destructive inspection method for mechanical type reinforcing bar coupler and ultrasonic probe for inspection - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily measure fitting length L of a reinforcing bar fitted with a sleeve and then evaluate performance of a coupler jointed with a mechanical type reinforcing bar coupler. <P>SOLUTION: The mechanical type reinforcing bar coupler is formed by joining end edges 1a, 2a of two reinforcing bars 1, 2 to connect with a sleeve 3. A probe 5 of an ultrasonic wave is contacted to the surface of the reinforcing bar 2 at a distance L<SB>0</SB>from the end edge 3b of the sleeve 3. The ultrasonic wave (surface SH wave) is transmitted from the probe 5 towards the end edge 2a, and then echo reflected with the end edge 2a of the reinforcing bar 2 is received and displayed on a flaw detector 4. A distance L1 from the probe 5 to the end edge 2a of the reinforcing bar 2 is calculated and length L from the end edge 3b to the end edge 2a of the reinforcing bar 2 is measured by analyzing the time-of-arrival of the echo. The analyzing of the time-of-arrival of the echo determines with either 'the time-of-arrival of a pulse firstly reaching' or 'the time-of-arrival of pulse with maximum amplitude among pulses reaching' as the time-of-arrival. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION In a mechanical rebar joint in which two rebars are joined by covering the ends with a sleeve, whether or not the joint is appropriate, that is, the length of the rebar covered by the sleeve is measured. The present invention relates to a nondestructive inspection method for a mechanical rebar joint and an ultrasonic probe optimum for this inspection direction.

[0002]

2. Description of the Related Art Pressure welding, welding, mechanical joints and the like are used as joint methods for joining reinforcing bars in the longitudinal direction. Non-destructive inspection is indispensable for ensuring the reliability of the joint, and high reliability is ensured by non-destructive inspection for pressure welded joints and welded joints.

With respect to mechanical joints, non-destructive inspection methods that are easy to apply in the field have not been established, and the reliability of the joints may be confirmed by a radiation transmission test only when serious doubts arise. there were.

[0004]

Generally, the reinforcing bar is D19.
(Reinforcing bar outer diameter 19 mm) to D51 (reinforcing bar outer diameter 51 mm), the radiation transmission test can be applied when the reinforcing bar diameter is small, but when the reinforcing bar diameter is large like D51, sufficient image quality is obtained. There is a problem that an X-ray film cannot be obtained and reliable inspection cannot be performed. Further, in the radiation transmission test, there is a problem that the device becomes large and a simple inspection cannot be performed on site.

[0005]

However, according to the present invention, the arrival time of the echo reflected from the edge of the reinforcing bar is measured by the ultrasonic method (surface SH wave flaw detection method), which is not applicable to the field. Destructive inspection method was realized.

That is, the present invention relates to a mechanical rebar joint in which ends of two rebars are covered with sleeves and joined.
This is a nondestructive inspection method for mechanical rebar joints, characterized by performing the following steps. (1) An ultrasonic probe is applied to the surface of the reinforcing bar near the edge of the sleeve to emit ultrasonic waves consisting of surface SH waves toward the edge of the reinforcing bar, and (2) the edge of the sleeve. On the surface of the rebar in the vicinity, among the transmitted ultrasonic waves, receive the echo reflected at the edge of the rebar, (3) from the sleeve edge to the rebar edge by analyzing the arrival time of the echo Measure the length of.

Further, in the above description, the analysis of the arrival time of the echo is a nondestructive inspection method for the mechanical rebar joint in which the first arrived pulse or the pulse having the maximum amplitude is used as a measurement value.
Further, the analysis of the arrival time of the echo is a nondestructive inspection method of the mechanical rebar joint in which the pulse that reaches first and the pulse of the maximum amplitude are compared and examined, and the optimum value is used as the measured value.

Another aspect of the present invention is an ultrasonic probe connected to a flaw detector that measures the arrival time of an echo, processes the echo, and displays the processed result on a screen. An ultrasonic probe for inspection, characterized in that a measurement protrusion having a predetermined length is formed in the ultrasonic wave transmitting direction.

When an echo is measured using the present invention, an echo as shown in FIG. 22 appears. In this case, normally, as shown in FIG. 22A, if the maximum signal is detected within a preset range in which the first echo reaches the maximum, the arrival time of the signal is adopted. , The speed at which the transmitted ultrasonic waves travel in the reinforcing bar is known, so the distance to the edge of the reinforcing bar can be known.

However, for some reason, the echo that arrives first is small, and the echo that arrives subsequently is larger than the first echo. In this case, there are two methods: a method of measuring the length from the arrival time of the first echo and a method of measuring the length from the arrival time of the maximum echo.

The obtained ultrasonic signal is returned to an electric signal by the probe (piezoelectric element). In the case of adopting the maximum echo, after rectifying the time-series electric signal (alternating current), the maximum signal is obtained within a certain time range.

That is, the algorithm for obtaining the maximum value records the maximum value of the echo height from the first time set in the monitoring range, the data and the time, and compares it with the echo height obtained at the next position. And re-record the larger data as maximum value data. This processing can be continued until the end time of the monitoring range, and as a result, the arrival time of the remaining echo height data as the maximum value data can be adopted as the arrival time data. Therefore, this process is relatively easy.

On the other hand, in the case of obtaining the echo that arrives first, if the amplification degree of the signal is increased, the noise level rises and the signal cannot be distinguished, and noise may be erroneously recognized as the signal. Therefore, how much amplification (gain)
There is a problem in the process of determining whether to raise or to raise the time information of the signal. For example, in order to obtain the first data, it is necessary to find the point where the change in echo height at each data point changes from "+" to "-" and confirm that it is a peak. In this case, mathematically, the differential method is used,
The difference is calculated on the processing software. Therefore, the algorithm becomes complicated.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION (1) In a mechanical rebar joint, a sleeve 3 is put on the ends of two rebars 1 and 2 to join them, and the two rebars 1 and 2 are abutted with their edges 1a and 2a. To join. (2) Near the edge 3b of the sleeve 3 on the reinforcing bar 2 side (edge 3b
The ultrasonic probe 5 is applied to the surface of the reinforcing bar 2 at a distance L ₀ from (FIG. 2). The ultrasonic probe 5 is connected to the flaw detector 4. (3) Ultrasonic waves (surface SH wave) toward the edge 2a of the reinforcing bar 2.
To send. (4) Of the ultrasonic waves transmitted by the probe 5, the edge 2 of the reinforcing bar 2
The echo reflected by a is received and displayed on the flaw detector 4 (FIG. 3). (5) The probe 5 is analyzed by analyzing the arrival time of the echo.
It calculates a distance L ₁ to the edge 2a of the reinforcing bar 2 from, for measuring the length L to the rebar edge 2a from the sleeve end edge 3b.
The arrival time of the echo is analyzed as either the "arrival time of the pulse that first arrived" or the "arrival time of the pulse having the maximum amplitude among the arrived pulses".
The distance L ₁ can be calculated from the arrival time and the velocity of the ultrasonic wave traveling in the reinforcing bar. (6) Based on the measured length L, it is possible to judge whether or not the joint is an effective one that maintains a predetermined mating length L. (7) If this measuring method is used, there is no support for measuring the mating length even for a joint in which the sleeve is filled with a material such as resin or mortar. Further, not only mechanical joints but also crimp joints are possible.

Further, when there is a film on the surface of the reinforcing bar in the portion to be contacted with the probe, generally, when there is a thick coating film or synthetic resin film, it is necessary to remove it. , Can be measured as it is.

[0016]

[Experimental example] (1) Specimen As shown in Table 1, measurement is performed on each specimen whose mating length is known in advance. The deformed rebars 1 and 2 with ribs are brought into contact with each other, and the sleeve 3 is put on the ends thereof to construct each test body (FIGS. 1A to 1D).

[0017]

[Table 1]

(2) Experimental apparatus As shown in FIG. 3, a probe 5 connected to a flaw detector 4 with a cable 10 is used.

(3) Experimental method Using a digital ultrasonic flaw detector 3 and a surface SH wave probe 5,
From the probe 5 to the end edge (end face) 1a (2) of the reinforcing bar 1 (reinforcing bar 2)
The mating length is measured by measuring the distance to a). As shown in Table 1, using screw rebars from Company T and Company K, measurements are made from both vertical ribs on both sides of the rebar from normal mating length to 1/4 mating length (Fig. 1). . The deformed rebars 1 and 2 with ribs are butted, and the sleeve 3 is covered on the ends thereof, and the probe 5 is placed at a position at a distance L ₀ (L ₀ = 50 mm) from the end edges 3 a and 3 b of the sleeve 3. Then, the measurement is performed (FIGS. 3 and 19).

(4) Experimental Results As shown in FIGS. 4 to 18, it is clear that the mating length of the mechanical joint can be measured and the mating length can be measured with sufficient accuracy by the surface SH wave flaw detection method. Became.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an apparatus for carrying out the method of the present invention will be described. The flaw detector 4 and the probe 5 used in the experiment can be connected by a cable 10 to form an apparatus (FIG. 3), but in order to use them on site, it is necessary to make them compact and easy to operate. There is.

That is, the function of the flaw detector, that is, the measuring device 6 is constructed by connecting the small device body 7 incorporating the above-mentioned measuring method as a program and the surface SH wave probe 5 with the cable 10. (FIG. 20). The device body 7 is ON-O
It has an FF switch 8 and a screen 9 for processing the measurement result into a length and displaying the length L ₁ .

The apparatus main body 7 can input the value of the length L ₀ or fixes the value of the L ₀ (the probe is placed on the position of the defined length L ₀ for measurement). By doing so, the program can be configured to display the length L (that is, L ₁ -L ₀ ) on the screen 9. In the figure, 12 is a switch for setting various conditions at the time of measurement (FIG. 20, FIG. 21).
(B)).

In another embodiment, the distance L from the ultrasonic wave reception / transmission position of the probe 5 to the edge 3b of the sleeve 3 is L.
_In order to keep ₀ constant in advance, the probe 5 can be configured by projecting the measurement projection 11 on the end face of the probe 5 in the ultrasonic wave transmitting direction (FIGS. 21A and 21B). . That is, in the device main body 7 in this case, the length L ₀ fixed on the screen 9 by adopting the fixed length L ₀ in a state where the end edge 11 a of the measurement protrusion 11 is in contact with the end edge 3 b of the sleeve. L can be displayed. Further, the operator only has to apply the lower surface (ultrasonic wave transmitting / receiving surface) of the probe to the surface of the reinforcing bar 1 (usually on the vertical ribs) and the measurement projection 11 end edge 11a to the sleeve end edge 3b. The engagement length L of the sleeve 3 can be measured.

[0025]

EFFECT OF THE INVENTION By applying an ultrasonic probe to the surface of the reinforcing bar near the edge of the sleeve and transmitting ultrasonic waves consisting of surface SH waves toward the edge of the reinforcing bar and receiving echo,
Since the distance to the edge of the reinforcing bar can be measured, there is an effect that the fitting length of the reinforcing bar fitted with the sleeve can be easily measured and the performance of the bonded joint can be evaluated by the mechanical joint.
Moreover, since measurement can be performed with a device including a probe and a flaw detector, a measurement system that is easy to carry can be configured.

Further, when the probe provided with the measurement protrusion is used, there is an effect that the measurement error due to the presence or absence of the skill of the operator is eliminated, and the engagement length can be measured very easily.

[Brief description of drawings]

1A to 1D are front views of four test bodies of an experimental example.

FIG. 2 is a conceptual diagram of an embodiment of the invention.

FIG. 3 is a conceptual diagram showing a configuration of an apparatus of an experimental example of the present invention.

FIG. 4 is a graph showing the organic mating length of D25 manufactured by T company.

FIG. 5 is a graph showing the error in the organic coupling length of D25 manufactured by T company.

FIG. 6 is a graph showing an echo height at the time of organic measurement of D25 manufactured by T company.

FIG. 7 is a graph showing the D25 inorganic mating length of Company T.

FIG. 8 is a graph showing the error in the D25 inorganic mating length of Company T.

FIG. 9 is a graph showing the echo height at the time of measuring D25 inorganic matter of Company T.

FIG. 10 is a graph showing the D51 inorganic mating length of Company T.

FIG. 11 is a graph showing an error in the inorganic mating length of D51 manufactured by T company.

FIG. 12 is a graph showing the echo height at the time of D51 inorganic measurement of Company T.

FIG. 13 is a graph showing D25 mating length of K company.

FIG. 14 is a graph showing an error in a mating length of D25 manufactured by K company.

FIG. 15 is a graph showing the echo height when measuring D25 of K company.

FIG. 16 is a graph showing a mating length of D51 manufactured by K company.

FIG. 17 is a graph showing an error in a mating length of D51 manufactured by K company.

FIG. 18 is a graph showing the echo height when measuring D51 of K company.

19 (a) to (c) are conceptual diagrams showing a test body used in an experimental example and a measurement position.

FIG. 20 is a configuration diagram of a measuring device used for implementing the present invention.

FIG. 21 is a diagram of the probe of the present invention, in which (a) is a state in which the probe is in contact with a sleeve to be measured, and (b) is a diagram showing a measuring device using the probe. is there.

22 (a) and (b) are screens displaying the echo of the present invention.

[Explanation of symbols]

1 rebar 1a Edge of rebar 2 rebar 2a Edge of rebar 3 sleeves 3a, 3b Edge of sleeve 4 flaw detector 5 probe 6 Measuring device 7 Device body 9 screens 11 Measurement protrusion 11a Edge of measurement protrusion

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Emi Kobayakawa             Shimizu Construction 3-4-17 Etchujima, Koto-ku, Tokyo             Within the corporation (72) Inventor Shoji Sekino             3-2-23 Yashio, Shinagawa-ku, Tokyo Japan Gas Pressure             Inside the joint stock company (72) Inventor Tsujihiko Yoshino             1-24 Iidabashi Masumoto Bi, 1-24 Yangbacho, Shinjuku-ku, Tokyo             Le 5th floor Musashi Co., Ltd. (72) Inventor, Hadano             2641 Yamazaki, Noda City, Chiba Prefecture Tokyo University of Science (72) Inventor Hitoshi Hamasaki             1 Tatehara, Tsukuba-shi, Ibaraki Architecture             In the laboratory F term (reference) 2G047 AA05 AB01 AB07 BA03 BC18                       CA01 CB03 DA01 EA08 EA10                       GA01 GA03 GG24 GG28 GG30                       GH03 GH04

Claims (4)

[Claims] 1. A non-destructive inspection method for a mechanical rebar joint, which comprises performing the following steps in a mechanical rebar joint formed by covering a sleeve on the ends of two rebars and joining them. (1) An ultrasonic probe is applied to the surface of the reinforcing bar near the edge of the sleeve to emit ultrasonic waves consisting of surface SH waves toward the edge of the reinforcing bar, and (2) the edge of the sleeve. On the surface of the rebar in the vicinity, among the transmitted ultrasonic waves, receive the echo reflected at the edge of the rebar, (3) from the sleeve edge to the rebar edge by analyzing the arrival time of the echo Measure the length of. 2. The nondestructive inspection method for a mechanical rebar joint according to claim 1, wherein the arrival time of the echo is analyzed by using a pulse that reaches first or a pulse having the maximum amplitude as a measurement value. 3. The nondestructive inspection method for a mechanical rebar joint according to claim 1, wherein the analysis of the arrival time of the echo is carried out by comparing and comparing the first arrived pulse and the pulse of the maximum amplitude, and the optimum value is used as the measured value. 4. Echo arrival time is measured and processed,
An ultrasonic probe connected to a flaw detector for displaying a processing result on a screen, characterized in that a measurement protrusion having a predetermined length is formed in the ultrasonic wave transmitting direction of the ultrasonic probe. Ultrasonic probe for.