JPH09304357A - Method for examining filling state of filler using ultrasonic wave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an examining method by which the filling state of mortar or the like on the back of a steel plate or the like can easily be detected from the front. SOLUTION: A method for examining the filling state of a filler, such as mortar 2 on the back of a plate such as a metallic plate comprises placing an ultrasonic-wave transmitting 4 and receiving 5 probes on the surface 3 of the plate and in respective positions that are a certain distance away from each other, bringing the probes into contact with the surface 3, causing a longitudinal ultrasonic pulse from the transmitting prove 4 incident on the surface 3 at a longitudinal-wave critical angle, converting the mode of part of a creeping wave 6 produced into a transverse wave 7, detecting using the receiving probe 5 the echoes that are reflected at the back 8 and the front 3 once or plural times, and examining the filling state of the filler that is in contact with the back 8 of the pate from the damping factor of the echoes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for externally inspecting a filling state of mortar or the like on the back side of a steel plate or the like on the outside of a structure or the like.

[0002]

2. Description of the Related Art In order to reinforce the earthquake resistance of elevated roads, railways and other structures and buildings, a steel plate is wound on the outside of columns such as pier columns, and a reinforcement method of filling a resin mortar or the like in the gap between the steel plate and the column is known. Has been done. Further, there is a method in which a steel lining pipe is provided along the inner surface of a hydraulic conduit for hydroelectric power generation, and a resin mortar or the like is filled in the gap between the inner surface of the hydraulic conduit and the lining pipe for reinforcement. At this time, unless the mortar is completely filled in the gap between the steel plate and the structure on the back side, sufficient strength cannot be exhibited, so it is necessary to inspect the filled state of the mortar and the like from the outside.

Conventionally, as such an inspection method, a percussion method in which the sound of a hammer or the like is used for checking, and a method of transmitting radiation from a radioisotope are known.

On the other hand, a method is known in which an ultrasonic creeping wave is used for flaw detection of a test body. A creeping wave is generated when an ultrasonic longitudinal wave is incident on the surface of a specimen at an incident angle of the longitudinal wave critical angle (first critical angle), and propagates in the specimen along the free surface. It is The creeping wave propagates while attenuating while radiating inside the test body by continuously mode-converting a part of energy into a transverse wave.

[0005]

In the conventional inspection method using the hitting sound and the radiation, it is necessary to inspect an extremely large number of inspection points over the entire surface to be inspected.
There are problems that it is troublesome and that when radioactive materials are used, special handling qualifications and protective equipment are required depending on the dose size.

Therefore, it is an object of the present invention to provide an inspection method capable of easily knowing the filling state of mortar or the like on the back side of a steel plate or the like from the surface.

[0007]

In order to achieve the above object,
As a result of earnest studies by the present inventors, when a creeping wave of ultrasonic waves is used, when the creeping wave is mode-converted into a transverse wave and reflected on the back surface of the steel sheet, the reflectivity depends on the filling state on the back side of the steel sheet. The filling state on the back side of the steel sheet can be known by measuring the intensity of the reflected wave.The creeping wave is mode-converted into a transverse wave gradually while advancing along the steel sheet surface, and the transverse wave traverses the steel sheet. Since it is reflected at different points on the back side of the steel sheet, it has been found that the filling state of the entire back side of the steel sheet between two points where the ultrasonic wave is incident and the receiving point can be inspected by one measurement, thus completing the present invention. Came to do.

That is, the present invention is a method for inspecting the filling state of a filling material such as mortar on the back side of a plate such as a metal plate, wherein a transmitting probe and a receiving probe for ultrasonic waves are placed at positions separated by a certain distance on the surface of the plate. A probe is placed in close contact with the surface, an ultrasonic pulse of a longitudinal wave is made incident on the surface at a critical angle of a longitudinal wave from the transmitting probe, and a part of the generated creeping wave is changed to a transverse wave. Converting, echoes reflected on the back surface and front surface of the plate once or a plurality of times are detected by the reception probe, and the filling state of the filling material in contact with the back surface of the plate is inspected from the attenuation rate of the echo. The gist is a method of inspecting the filling state of the filling by ultrasonic waves, which is characterized by

A creeping wave, which is a longitudinal wave traveling along the surface of a plate-shaped test body, propagates while attenuating while radiating inside the test body by continuously mode-converting a part of its energy into a transverse wave. To do. When the transverse wave radiated in the test body reaches the back surface of the test body, a part of the energy thereof passes through the back surface of the test body and enters the medium in contact with the back surface of the test body.
Most of the remaining energy that did not pass through the back surface of the test body is converted into creeping waves again on the back surface of the test body and propagates along the back surface of the test body. The creeping wave along the back surface propagates in the same manner as the creeping wave along the front surface while being mode-converted into transverse waves, and the mode-converted transverse waves head again to the surface of the test body. In this way, the creeping waves of the ultrasonic waves incident on the plate-shaped test body are alternately mode-converted between longitudinal wave creeping waves propagating along the front and back surfaces and transverse waves reciprocating between the front and back surfaces. On the other hand, reflection is repeated on both sides of the test body and propagates in the test body, and at the time of reflection, a part of the energy is transmitted to the outside and rapidly attenuated.

Generally, when an ultrasonic wave propagates through a medium and reaches an interface between different media, reflection and passage occur. The ratio of the energy of the reflected wave and the energy of the passed wave is the density of the medium on both sides of the interface. It is determined by the acoustic impedance (Z = ρC) represented by the product of (ρ) and the speed of sound (c).

That is, the sound pressure reflectance γ of the interface between the media 1 and 2
In the case of vertical incidence, when the acoustic impedance of the medium 1 is Z ₁ and the acoustic impedance of the medium 2 is Z ₂ , it is expressed by γ = | (Z ₂ −Z ₁ ) / (Z ₂ + Z ₁ ) |. For example, at the interface between steel and mortar, the acoustic impedance Z between steel and mortar is about 23 × 10 ^{6 for} steel.
Since kg / m ² sec and mortar are about 4 × 10 ⁶ kg / m ² sec, the sound pressure reflectance γ between them is about 0.7.

Between steel and air, γ≈1, which is approximately 100.
% Is reflected, while about 70% is reflected between steel and mortar, and 30% is transmitted. Therefore, if the steel plate and mortar are in close contact, the ultrasonic waves incident on the steel plate are The reflected wave is attenuated by 30% each time
The echo intensity decreases rapidly with the number of reflections. By measuring the attenuation of this echo, the filling state of the mortar on the back surface of the steel sheet can be known.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the method for inspecting the filling state of mortar or the like on the back side of a steel sheet by ultrasonic waves according to the present invention will be specifically described with reference to the drawings.

As shown in FIG. 1, when the steel plate 1 and the mortar 2 are in contact with each other, the transmitting probe 4 and the receiving probe 5 are closely contacted to the surface 3 of the steel plate 1 with a certain distance. When a longitudinal wave of ultrasonic waves is incident on the surface 3 of the steel sheet 1 from the transmitting probe 4 at a critical angle of the longitudinal wave, a creeping wave 6 consisting of the longitudinal wave propagating along the surface 3 is generated. This creeping wave propagates along the surface 3 of the steel plate 1 and gradually undergoes mode conversion into a transverse wave 7,
The generated transverse wave 7 reaches the back surface 8 of the steel plate 1. When the mortar 2 is in close contact with the back surface 8, the mortar 2 is reflected at a reflectance of 70% between the steel and the mortar 2, and the remaining 30% is transmitted through the mortar 2. When reflected, this reflected wave is converted into a longitudinal wave again and becomes a creeping wave 6 that propagates along the back surface 8. Similarly to the creeping wave 6 along the front surface, the creeping wave 6 along the back surface is gradually mode-converted into the transverse wave 7, and the generated transverse wave 7 is directed to the surface 3 of the steel plate 1. The transverse wave 7 reaching the surface 3 of the steel plate 1 is reflected by approximately 100%, and at that time, the mode is converted again into a longitudinal creeping wave 6.

In this way, the front surface 3 and the back surface 8 of the steel plate 1 are
While the mode is alternately converted into the creeping wave 6 and the transverse wave 7 between, the reflection and the partial transmission are repeated, and the energy is attenuated according to the number of reflections on the back surface 8. For example, the echo received by the receiving probe 5 is reduced by 10 dB if it is reflected on the back surface 8 three times by that time, and is 15 dB when it is reflected five times.
30 dB reduction after 10 reflections.

The time from the emission of the pulse to the detection of the echo is received by the receiving probe 5 after receiving the reflected wave which has been transmitted from the transmitting probe 4 by the longitudinal ultrasonic pulse and following the various propagation paths. When the intensity of the echo is displayed on a display device such as an oscilloscope or recorded and read, the arrival of the echo is delayed by the time it takes to reciprocate through the thickness of the steel plate 1 according to the number of reflections, so that these overlap. As shown in FIGS. 2 and 3, a plurality of bottom surface echoes are observed. FIG. 2 shows the case where the back surface 8 has no filling and is in contact with air, and FIG. 3 shows the case where the entire back surface 8 is completely filled with the mortar 2. However, the measurement sensitivity of FIG. 2 is 54 dB, and the measurement sensitivity of FIG. 3 is 9 dB.
Since the measurement sensitivity is adjusted so that the peak height is 3% and the peak height is 80% of full scale in both figures, the actual peak height in FIG. 3 is the same as the peak height in FIG.
It is 39 dB or about 1/100.

When the mortar 2 is filled, the sound pressure reflectance γ is as small as 70% and the attenuation rate is large as described above, so that the echo is rapidly attenuated as the number of reflections is increased. The attenuation rate of the echo changes according to the filling rate of the mortar 2, and the filling rate of the mortar 2 can be determined from the attenuation rate of the echo.

[0018]

【Example】

[Example 1] A test piece 11 made of a U-shaped steel having a width of 123 mm and a length of 1600 mm shown in Fig. 4 was used, and as shown in Fig. 4c, inside the test piece 11 along the longitudinal direction of the test piece 11. The mortar filling part 9 on both sides and the hollow part 10 in the center.
And a local water immersion type transmission probe 4 and a reception probe 5 are arranged at the center of the width of the test body 11 and at positions of 300 mm from both ends, respectively, and are separated from each other by 1000 mm. The surface 3 of the test body 11 so as to be in close contact. An ultrasonic wave pulse of 2.25 MHz longitudinal wave was made incident from the transmitting probe 4 at the longitudinal wave critical angle of steel, 14.5 °, and the echo received by the receiving probe 5 was observed. An echo as shown in 3 was observed. Of the multiple echoes observed, the peak height of the largest bottom echo was measured.

The measurement was repeated by changing the length D of the hollow portion 10 to change the mortar filling rate. Instead of reading the echo peak height directly on the oscilloscope,
Adjust the sensitivity of the oscilloscope so that the peak height of the maximum observed bottom surface echo is exactly 80% of the full scale on the oscilloscope, read the value of the sensitivity scale at that time as a dB value, and the result Is shown in Table 1.

[Table 1]

The results are shown in the graph of FIG. In the graph of FIG. 5, when the mortar filling rate (%) is plotted on the abscissa and the mortar filling rate is 0 and the mortar is filled at a certain filling rate, the peak height ratio is adjusted to 80%. Expressed as the sensitivity difference (dB) of, and scaled on the vertical axis.

From these results, it can be seen that the ratio (dB value) of the peak height of the echo displayed in logarithm is directly proportional to the mortar filling rate.

[0022]

According to the method for inspecting the internal filling state by ultrasonic waves according to the present invention, between the transmitting probe 4 and the receiving probe 5 which are arranged on the surface 3 of the test body 11 at a certain distance. The filling state of the mortar or the like on the back side of the part of the test body 11 can be quantitatively grasped as the average filling rate of the straight line portion between them, and if the observed filling rate is 100%, each of the portions between them can be grasped. It can be confirmed that the filling is complete with one measurement, and the inspection can be performed extremely efficiently. If the filling rate is 1
If it is not 00, or if the filling rate is lower than the predetermined limit, by a percussion method or a vertical flaw detection method using ultrasonic waves,
It is possible to identify the defective part of mortar filling.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an inspection method of an internal filling state by ultrasonic waves according to the present invention.

FIG. 2 is a diagram showing a bottom surface echo when the mortar filling rate is 0%.

FIG. 3 is a diagram showing a bottom surface echo when the mortar filling rate is 100%.

FIG. 4 is an explanatory diagram of a test body used in an example of an inspection method for an internal filling state by ultrasonic waves according to the present invention.

FIG. 5 is a graph showing the measurement results of an example of the method for inspecting the internal filling state by ultrasonic waves according to the present invention.

[Explanation of symbols]

 1 Steel plate 2 Mortar 3 Surface 4 Transmitting probe 5 Receiving probe 6 Creeping wave 7 Transverse wave 8 Backside 9 Mortar filling part 10 Cavity part 11 Specimen

Claims (2)

[Claims] 1. A method of inspecting a filling state of a filling material such as mortar on the back side of a plate such as a metal plate, wherein an ultrasonic transmitting probe and an ultrasonic receiving probe are provided at positions separated by a certain distance on the surface of the plate. Arranged and in close contact with the surface, an ultrasonic pulse of a longitudinal wave is incident on the surface at a critical angle of the longitudinal wave from the transmitting probe, and a part of the generated creeping wave is converted into a transverse wave. An echo reflected on the back surface and the front surface of the plate once or a plurality of times is detected by the reception probe, and the filling state of the filling material in contact with the back surface of the plate is inspected from the attenuation rate of the echo. The inspection method of the filling state of the filling by ultrasonic waves. 2. The filling is for reinforcing columns such as pier columns,
A mortar such as a resin mortar filled with a steel plate or the like around the pillar to fill the gap between the steel plate and the pillar, or an inner pipe is provided along the inner surface of the water conduit to provide the inner surface of the water conduit and the inner lining pipe. The method for inspecting the filling state of a filling by ultrasonic waves according to claim 1, which is a filling made of mortar such as resin mortar filled in the gap.