JPS61264253A - Strand disconnection detecting method for parallel wire strand - Google Patents

Abstract

PURPOSE:To detect even disconnection near the fastening part of a parallel wire strand by making an ultrasonic in a band of a prescribed range from an ultrasonic probe incident from the end face of each strand and receiving the reflected wave from the disconnection part by the probe. CONSTITUTION:The ultrasonic wave having a frequency higher than 4MHz and lower than 50MHz from an ultrasonic probe 4 is made incident from the exposed parts of the strand ends of a fastening part 3 and is propagated in the longitudinal direction of the strands. Since the frequency higher than 4MHz and lower than 50Hz is used, this ultrasonic wave is propagated efficiently in the longitudinal direction of strands. Since the ultrasonic wave is reflected by a disconnection part 5 near the fastening part 3, the reflected echo is received by the same probe 4, and the presence/absence of disconnection and its position of the strand are detected surely in accordance with the presence/absence of the reflected echo and its arrival time.

Description

Detailed Description of the Invention (Utilization i1 on the above) The present invention is a non-destructive method for collecting wires constituting Bakel wire strands used as tension members in long bridges such as cable-stayed bridges. The present invention relates to a method for detecting tllIbg.

(Conventional technology) As a tension member used in long bridges, etc.

Among wire ropes, a parallel wire strokund type wire rope made by bundling relatively large T44 wires with a diameter of about 5 to 7 W is preferably used. It is essential to non-destructively detect the presence or absence of wire breaks in parallel wire strands during their service life, and there is a strong need for the establishment of such technology.

Conventionally, the method for detecting the breakage 1IeI of the turtle wire is as follows:
The mainstream method is the magnetic probe method, which uses a wire to detect magnetic flux leaking through defects. However, the wire diameter used for long bridges, etc.
In cables with large east diameters, it becomes difficult to detect defects caused by 1 company * seagulls as these dimensions increase, and -t! A portion of the cable is large in size, and it is extremely difficult to move and scan it in the longitudinal direction of the cable. Furthermore, the application of the air flaw detection method is not recommended due to the fact that the sheathing tool is not suitable for the area near the fastening part of the end where it is thought that retention due to M contact is likely to occur on the collecting surface. I'm fed up.

On the other hand, the sonic wave detection method can be applied not only to members but also to IF-column bodies, and various application techniques have been proposed depending on the form of the defect detection target. However, this method is not applicable to detecting disconnection in parallel wire strands.

There is no example other than the applicant's earlier application, Machitane Sho 59-259016.

(Problems to be Solved by the Invention) The method of the above-mentioned WI No. 59-25901b makes it possible to detect cable breaks in parallel wire strands using ultra-f waves, and exhibits considerable effectiveness. However, it has been found that there are certain restrictions on the application of 7.

However, at the fastening part of parallel wire strands,
Some cables have a zinc alloy cast between them, so in that case, i! In the usual detection frequency interval below 4MHz,
While the super-IT wave propagates through the wire, it is absorbed by the zinc alloy, etc., and cannot be propagated efficiently in the length direction of the wire.
Even if there is a disconnection as a result, it is disconnected! ! It was found that the reflected echo from s was not received and could be mistaken for a non-T# line.・Unexploded qa, even if the cable connection part of the Bakel wire strand is made of zinc alloy, etc. It is an object of the present invention to provide a method for detecting a wire break near an IO fastening part.

(Tth means and effects for solving the problem, embodiments) The above-mentioned object of the present invention Vi, a method for detecting a disconnection near the II# connection S of a loose wire strand, and an end face of each single wire. )]! 50Mfi over 4MHz from ifl probe
This is achieved by injecting an ultrasonic wave with a wavelength below z and receiving the reflection from the disconnected part using the same probe in a single probe.

FIG. 1 shows a portion of the parallel wire strand in the vicinity of the cable fastening portion. The wire strand (for example, 5 m in diameter) is made up of wires (2) that are terminated.The fastening ff1l (3) at the end of the sin east is made by casting zinc alloy or the like between the cables M. There are some that are fastened.When zinc alloy etc. is cast in this way, 1
When the circumferential number is ultra-z, the ultrasonic wave propagating in the wire (2) is dissipated into the zinc alloy, etc., and cannot be efficiently propagated in the length direction of the wire. In the present invention, ultrasonic waves with a frequency exceeding 4 MHz and a frequency of 50 ME1 Hz are incident on the ultrasonic probe (4) from the exposed part of the cable end of the fastening part (3).

Propagate in the length direction of the wire. 4 Hl MEiz5
0h/Ulz for example 10 MEIz,
By using ultraf-waves with a frequency of 22 MHz, this ultrasonic wave can be efficiently propagated along the length of the wire, and since it is reflected at the break m <s> near the fastening part, one reflected echo is generated. By receiving the same RNL element (4), it is possible to reliably detect the presence or absence of a break in the strand and its position based on the presence or absence of one reflected echo and its piercing time.

In general, the frequency used in ultrasonic IS is determined by (i) flaw detection distance, (1) dead zone, (i98m) defect size, etc. At high circumference i &, attenuation is large, and at short range gR At low frequencies, the dead zone becomes large, making it impossible to detect small defects.At low frequencies, the directivity angle is large and it is not possible to concentrate the sound waves.Therefore, depending on the target conditions, ultrasonic flaw detection There is a number of frequencies suitable for this, and generally a frequency of 1 to 5 b'fHz is often used. It is only applied to materials, etc.

In the present invention, even if a damping factor is added to the fastening part of the parallel wire strand by using a zinc alloy or the like, it is possible to detect a disconnection of the l/4 wire near the fastening part.
4 Mf (High Jilt exceeding z and less than 50 hfHz)
Flaws are detected using a single detection method using ultrasonic waves with a certain number of waves and entering from the end face of the wire. The basis for this must be shown as follows.

Figure 5 ((A) shows the waveform when a wire (2) with a break (5) is detected using the configuration shown in Figure 1 using the 1MH2 ultra-f technique. The horizontal axis is time. , vertical axis l-f received sound pressure (
voltage). Even if an attempt is made to receive the reflected echo from the Ur line part, no reflected echo can be detected within one rotation.

The sixth factor (b) shows the waveform when hot water is drawn at the same frequency < 5 MHz. Although a slight reflected echo can be detected at 5 MHz, it is not clear.

If the cast-in feldspar (T) of the fastening part (3) exceeds 600a, detection Vi becomes difficult.

On the other hand, FIG. 2(a) shows a waveform when flaw detection is performed using ultrasonic waves of 10 MHz, which has an extremely short wavelength for a wire diameter of 9 in accordance with the present invention.

The second factor (b) shows waveforms obtained when flaws were detected at 22 MHz according to the present invention. In both cases, the reflection defect echo from the wr line portion can be clearly received. At this frequency, reflected echoes can be received even if the casting length of the fastened part exceeds 50ON.

Contrary to this, Fig. 6 (−→#'1t50 MHz super f
(waveform) shows the waveform when two tumors are formed. No reflected echo could be received at 50 hlkLz. This is thought to be due to the fact that the attenuation of the ultrasonic waves increases due to the crystal grains in the S-striped steel wire.

As described above, according to the present invention, it is possible to detect disconnection in 10 elements by using ultrasonic waves with a peripheral frequency exceeding 4 yrkiz t and less than 50 MEIIz.

(Effects of the Invention) According to the present invention, 1! near the fastening portion of the parallel wire strand! /r line 1-, it can be detected even in cases where conventional technology cannot detect it, contributing to the establishment of a disconnection investigation method,
Parallel wire strands (L) have the advantage of being highly reliable in terms of integrity and therefore safety.

[Brief explanation of the drawing]

Figure 1 is a g8'Wi diagram showing the detection of cable wire breakage near the fastening part of parallel wire strands, and Figure 2 (
The barrel was inspected for flaws using 10MHz ultrasonic waves according to the present invention, and Figure 2 (b) is a copy of the waveform in the case of 7'c.
Figure 6 (bottom) is a reproduction of the detection waveform at Hz, and Figure 6 (b) is a reproduction of the detection waveform at 5-speed. Figure 5 (c) is a reproduction of the flaw detection waveform at the same < 50 Maw.
J@, t3) Meeting/fastening part h (4) '1. Ultrasonic probe, (5) ψ/vJr line part, (Q... Casting length.

Claims (1)

[Claims] In order to detect wire breaks near the fastening points of the wires of parallel wire strands, ultrasonic waves with a frequency of more than 4 MHz and less than 50 MHz are incident from the end face of each wire from an ultrasonic probe, and the reflection from the wire breaks is detected. A method for detecting breakage in a parallel wire strand, characterized by detecting flaws using a single detection method that is received by the same probe.