JP3770668B2 - Method for detecting internal defects in structures - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for detecting an internal defect of a structure, and more specifically, the surface of the structure is hit with a constant energy, and the strength of the member estimated from the repulsion degree of the hit and the structure in the vicinity of the hitting surface. The present invention relates to a method of detecting an internal defect of a structure from the amplitude of the impact sound that is reflected and its variation.
[0002]
[Prior art]
Various methods have been developed as investigation techniques for detecting dangerous parts, deteriorated parts, defects, etc. of structures, particularly concrete structures. For example, visual inspection is a basic inspection method that has been carried out for a long time, but this method relies solely on vision, so if you are not an experienced engineer who has experience and sense of judgment It is impossible to inspect internal defects that cannot be performed and that do not appear outside. In the inspection of internal defects of concrete structures, a method by drilling sampling may be taken, but not only is very complicated, but it is not a preferable technique because it destroys the structure albeit partly, Internal defects cannot be inspected where sampling is not possible. Therefore, at present, a non-destructive inspection method for inspecting invisible internal defects and the like without destroying the structure is performed.
[0003]
As a nondestructive inspection method, an infrared method, a radar method, a shock elastic wave method, a sounding method, a resilience method, and the like are known. The infrared method is a method of measuring the temperature distribution of an object using an infrared camera and detecting points with different temperatures and points with large temperature changes as abnormal locations. However, sunlight and temperature changes are factors that cause temperature changes. Is a natural phenomenon, and its change is difficult to predict, so the reproducibility is low, and it is also easily affected by natural phenomena such as wind. Furthermore, the equipment is also expensive.
[0004]
The radar method is a method of detecting internal cavities by irradiating an object with electromagnetic waves and measuring the reflected waves from the surface and inside, but it is difficult to measure with structures where metal etc. are present inside. In addition, it is necessary to keep the irradiation angle of the electromagnetic wave at the time of measurement constant, but it is not only difficult to use in a structure having irregularities on the surface, but also the equipment is expensive.
[0005]
The shock elastic wave method is a method of detecting the presence of internal defects and backside cavities by hitting the surface of an object, measuring the reflected waves with a vibrator (ultrasonic sensor), and evaluating the frequency characteristics. However, it is necessary to bring the vibrator into close contact with the surface of the object, and depending on the surface shape of the object, the measurement work may be difficult.
[0006]
The percussion method starts from the primitive method of hitting the surface of an object and judging the percussion sound with the human ear, but the percussion sound is collected using a microphone, and its frequency, amplitude, etc. Has evolved into a way to evaluate The primitive method of judging the hitting sound by human hearing is not only influenced by the experience of the engineer, but also has a drawback that the result cannot be expressed numerically. In the method using a microphone, a mechanism that keeps the striking energy constant is important in order to make a numerical comparison. However, since the sound directly radiated from the striking point is measured, the striking device itself radiates. In addition to the difficulty that the generated sound becomes noise and a measurement error is likely to occur, the determination reference value is not clarified, and as a result, the determination is empirical.
[0007]
The rebound degree method is a method of measuring the strength of an object from the degree of repulsion using a device that strikes the surface of the object and measures the degree of repulsion. It is an evaluation. This method is used in a state where the object is firmly fixed, and a structure having a cavity on the back has a drawback that proper measurement cannot be performed because the structure itself vibrates. In addition, the measurement results are easily influenced by the surface properties of the object, and there is a difficulty in that the reproducibility is low. The Schmitt hammer method is known as the repulsion degree method, but this method is easily affected by the surface properties of the object, so that sufficient accuracy can be obtained unless the impact position is moved little by little and the impact is made many times. Absent.
[0008]
[Problems to be solved by the invention]
In view of the advantages and disadvantages of the nondestructive inspection method described above, an object of the present invention is to clarify a method for detecting an internal defect of a structure that can be efficiently performed by a simple operation without depending on an expert. .
[0009]
[Means for Solving the Problems]
The internal defect detection method for a structure according to the present invention includes a striking device and a sound collecting device arranged on the surface of a measurement object, and the sound collecting is performed by hitting a plurality of times at the same location by a hammer of the striking device. A method of detecting an internal defect of a structure by detecting two kinds of signals of a striking sound detected by a device and a change pattern of a repulsion degree with respect to a hammer on a surface of a measurement object detected by the striking device. The striking device and the sound collecting device are configured not to transmit vibration at the time of striking according to the following configuration A or B , and the change pattern is an image described below. A method for detecting internal defects in a structure.
[Configuration A] Configuration in which the striking device and the sound collecting device are separated and separated from each other. [Configuration B] Configuration in which the striking device / sound collecting device is provided with a vibration preventing mechanism using a damping material.
[Change pattern] is (1) percussion sound information for each striking position obtained by performing striking and sound collection at separate positions, and (2) per striking position of the measured material obtained by the striking device. An image in which the defect position is displayed in a visually observable state by a combination of intensity information and (3) position information input in advance.
[0010]
Specific Configuration of the Invention
Next, a specific configuration of the present invention will be described in detail with reference to the drawings.
[0011]
FIG. 1 is a conceptual diagram illustrating a method for detecting an internal defect of a structure according to the present invention. An apparatus for carrying out the method of the present invention includes a striking part A, a sound collecting part B, a measuring part C, and software D. Hereinafter, description will be made sequentially.
[0012]
In the striking part A, a striking device 10 that strikes the surface of the structure to be inspected with a constant energy is used. The hitting device 10 is based on a known Schmitt hammer used for concrete strength estimation, and further improved so that the hitting position and hitting energy can be kept constant. A specific example of the striking device 10 is shown in FIG. That is, the striking device 10 is provided with a plunger 14 supported by a plunger fixing spring 13 in a housing 12 to which a position fixing tool 11 is attached to the outside. A counterweight 15, a force spring 16, a motor 17, and a resilience measuring device 18 are arranged. The measurement of the repulsion degree by this striking device 10 is performed as follows. (1) The tip of the position fixing tool 11 is brought into contact with the surface of the measurement object. {Circle around (2)} The motor 17 is actuated to raise the counterweight 15 upward (in the direction away from the object to be measured) and compress the force spring 16. {Circle around (3)} When the compression of the force spring 16 reaches a certain value, the spring is released, and the head of the plunger 14 is hit by the counterweight 15 and the surface of the measurement object is hit by the tip. (4) The amount of rebound (rebound degree) of the counterweight 15 from the head of the plunger 14 at the time of impact is measured by a rebound degree measuring instrument 18. (5) The strength of the measurement object is estimated by repeating the above series of operations a plurality of times.
[0013]
In the hitting device 10 described above, the force spring 16 is compressed by the operation of the motor 17, but may be configured by a manual operation.
[0014]
The position fixing tool 11 is composed of a support leg such as a tripod or a four leg attached to the lower end of the housing 12, but the position fixing tool 11 and the housing 12 are independent and extend from the position fixing tool 11. A mode in which the housing 12 is fixed in a state in which the housing 12 can be rotated and moved up and down is also included in the present invention.
[0015]
The striking device 10 used in the method of the present invention is provided with a striking energy variable mechanism in order to cope with the difference in the measurement object. In order to make the impact energy variable, force springs having different spring constants may be used. For example, a spring having a thickness of 60 cm, such as tunnel lining concrete, uses a spring having a large spring constant. Moreover, in order to strike a measurement object having low strength, a plurality of plungers 14 having a diameter of, for example, 5 mm to 30 mm are prepared. That is, the penetration resistance is increased using a plunger having a large diameter for a measurement object having a low strength. Furthermore, as a tip shape of the plunger 14, for example, a spherical shape or a conical shape is prepared, and when a comparatively deep part of the measurement object is a measurement target, a conical shape in which the tip easily penetrates is used. .
[0016]
Further, in order to prevent a fine crushed material generated during the impact by the plunger 14 from becoming a cushion at the time of impact and preventing an accurate numerical value from being obtained, as shown in FIG. It is preferable to provide a mechanism for removing the crushed material so that compressed air is blown into the vicinity of the tip of the plunger 14 via 19 and the crushed material is blown off from the gap of the position fixing tool 11.
[0017]
The striking device 10 can cope with both a case of performing a single striking according to a measurement specification of a known Schmidt hammer test and a case of performing a continuous striking at the same point. If the surface of the object to be measured is very uneven, or the vicinity of the object to be measured is deteriorated, the measurement accuracy is significantly lowered with the conventional Schmitt hammer, but according to the striking device 10 used in the method of the present invention. By repeating hitting continuously at the same point, the surface irregularities can be smoothed and measured, so that a stable repulsion can be obtained.
[0018]
The striking device 10 used in the method of the present invention is provided with a mechanism for outputting the obtained repulsion degree in the form of voltage or the like. Moreover, it is preferable that the striking device 10 is provided with a mechanism for preventing noise emission by disposing a soundproofing / absorbing material on the surface or inner surface of the housing 12.
[0019]
In the sound collection unit B, the sound collection device 20 is used. The sound collector 20 has a structure in which a vibration suppression or resonance prevention material 21 is provided and a microphone 24 is disposed inside a hood 23 whose lower end is covered with a dustproof waterproof sheet 22. It arrange | positions in the state which contact | adhered or adjoined to the measurement surface at a distance. The frequency range of the microphone 24 is not limited as long as it does not have resonance characteristics in the measurement band. The inner surface of the hood 23 has a structure that does not have a special resonance characteristic in the audible range by providing unevenness. In addition, noise around the hood 23 is reduced by attaching a soundproof material such as a lead plate.
[0020]
In the present invention, the striking device 10 and the sound collecting device 20 are configured so that (1) they are basically separated and separated by a certain distance so as not to transmit vibration at the time of striking. or (2) that make up a striking device, the sound collecting device integrated by providing the vibration preventing mechanism and with damping material.
[0021]
The measuring device 30 of the measuring unit C is configured as follows.
[0022]
The measurement device 30 is input with two systems of signals: a striking sound (voltage) detected by the sound collector 20 and a rebound degree (voltage) detected by the striking device 10. The input range can be adjusted in several steps depending on the input hit sound. However, when A / D conversion described later is performed, the output is not changed by the range switching because the reciprocal of the ratio amplified by the range switching is multiplied. The impact sound (voltage) and repulsion degree (voltage) signals are A / D converted, stored in the memory of the measuring instrument, and transferred to the personal computer through the information transmitting means using the IC card and other transmitting means after the measurement is completed. . Therefore, measurement can be performed with a measuring instrument alone, even when connected to a personal computer.
[0023]
The measuring device 30 has a function in which the hitting device 10 hits the same point of the measurement object a plurality of times and outputs an average value and a standard deviation of the maximum amplitude of the hitting sound. That is, the measuring device 30 has two types of the continuous measurement mode and the same spot measurement mode. In the same spot measurement mode, the impact is repeated about 25 times at the same position. The deviation α is stored in the memory. For the rebound degree R, a predetermined determination reference value is input in advance. The determination reference values are determined as V + α (possibly defective) and V + 3α (defective) from the obtained V and α, and stored in the memory of the measuring instrument. In the continuous measurement mode, the amplitude value of each of the impact sound and the degree of repulsion is compared with the determination reference value, and a value exceeding the determination reference value is output to the display window as a determination result.
[0024]
The measuring device 30 can be used in a state where it is connected to a single unit or a personal computer.
The software D is basically a “determination reference value setting circuit by statistical processing” incorporated in the measuring apparatus 30, but additionally has a function of processing data on the personal computer 40. This will be described below.
[0025]
When the measurement position and the measurement order are input by operating the keyboard of the personal computer 40, an instruction to perform data measurement in accordance with the order is issued. When the striking device 10 and the sound collecting device 20 are operated according to the instruction, the measurement device 30 measures the striking sound and the resilience data, and the result is transferred to the personal computer 40 for storage and storage. On the screen of the personal computer 40, the contour map of the maximum impact sound and resilience (see A and B in FIG. 4), the defect position determined by the impact sound (see C in FIG. 4), and the material estimated from the resilience An intensity distribution diagram (see D in FIG. 4), a comprehensive judgment diagram (see E in FIG. 4) in which the defect position estimation result by the hitting sound and the material strength distribution diagram by the degree of repulsion are superimposed are displayed.
[0026]
The detection of internal defects in the structure by the method of the present invention includes, for example, (1) detection of non-adhered portions of the existing slope in the sprayed concrete slope and back cavity, (2) exploration of the cavity behind the tunnel lining, and (3) ▼ Applicable for detecting unfilled and unfilled parts of backing material in seismic reinforced steel sheet winding work, and detecting peeling of exterior wall tiles.
[0027]
In the detection of the non-contact portion of the existing slope in the shotcrete slope and the back cavity, a positioning net may be used as shown in FIG. Further, the hitting device 10 and the sound collecting device 20 are used by being mounted on a robot that moves on the surface of a measurement object by history operation or the like, in addition to being placed and moved by human power.
[0028]
The present invention described above is similar to the apparatus described in Japanese Patent Application Laid-Open No. 56-652 in that the concrete surface is hit and the hitting sound is recorded by a microphone, and a hood is used in the sound collecting section. However, in the device described in the publication, since the hitting portion and the microphone are present in the hood, the local hitting sound near the hitting point is recorded, which causes the microphone to pick up noise radiated from the hammer. Measurement error due to the fact that vibration is generated in the entire device due to impact, no special resonance prevention measures are taken inside the hood, and resonance occurs inside the hood, which hinders measurement. There is a difficulty that becomes very large. On the other hand, according to the present invention, according to the aspect in which the vibration generated at the striking point is propagated into the hood through the concrete, only the information inside the concrete can be obtained, and the sound collecting part is separated from the striking part. Therefore, there is an advantage that extra vibration is not transmitted to the microphone. According to the aspect in which the resonance prevention measure or the sound insulation measure is provided outside the hood, a good hitting sound can be obtained.
[0029]
In addition, the present invention can be used to evaluate the strength of a measurement object by striking the surface of the measurement object via a plunger (pressure receiving plate) or the like, and evaluating the strength of the measurement object based on the degree of repulsion. Common to the apparatus described in Japanese Patent Application Laid-Open No. 61-90037 in that a reaction force device is not required for measurement and a counterweight (weight) is made to collide with the plunger by the force stored in the spring. To do. However, it differs from the present invention in the following points. That is, in the present invention, there is no description about the number of hits in the device of the publication while the impact is performed multiple times at the same location. In the apparatus of the publication, the compressive strength of the object is measured. In the apparatus of the same publication, where the compressive strength of the surface of the target object, the compressive strength of the base material of the target object, and the depth of deterioration are measured, the measurement target is when the target object is young. In the present invention, while the measurement data of the apparatus of the same publication is the degree of resilience, which is standard hardened concrete, concrete with severe irregularities on the surface, concrete with surface degradation and concrete young age, There are differences such as the degree of repulsion (initial value, final value) and the change pattern of the degree of repulsion.
[0030]
【The invention's effect】
According to the method of the present invention, it is possible to numerically express hitting sound that has been used empirically in the past, and it is possible to easily detect internal defects of a structure without being a skilled engineer. Even if there is unevenness on the surface of the measurement object, by repeatedly striking continuously at the same point, it is possible to measure the smoothness of the surface unevenness, so stable measurement is possible, The issues mentioned above are solved.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an apparatus for carrying out the method of the present invention. FIG. 2 is a schematic sectional view of a striking device. FIG. 3 is a schematic sectional view of a sound collecting device. Schematic diagram showing the implementation status of the present invention [Explanation of symbols]
A-striking part B-sound collecting part C-measuring part D-software 10-striking device 11-position fixture 12-housing 13-plunger fixing spring 14-plunger 15-counterweight 16-force spring 17 -Motor 18-Repulsion degree measuring device 19-Compressed air discharge port 20-Sound collecting device 21-Damping / resonance preventing material 22-Dust-proof waterproof sheet 23-Hood 24-Microphone 30-Measuring device 40-Personal computer

Claims (1)

A striking device and a sound collecting device are arranged on the surface of the object to be measured, and a striking sound detected by the sound collecting device and detected by the striking device due to a plurality of hits performed at the same location by a hammer of the striking device. A method for detecting internal defects of a structure by detecting two systems of signals of a change pattern of the repulsion degree with respect to a hammer on the surface of the measured object, wherein the hitting device and the sound collecting device have the following configuration A Alternatively, the structure B is configured not to transmit vibration at the time of impact , and the change pattern is an image described below .
[Configuration A] Configuration in which the striking device and the sound collecting device are separated and separated from each other. [Configuration B] Configuration in which the striking device / sound collecting device is provided with a vibration preventing mechanism using a damping material.
[Change pattern] is (1) percussion sound information for each striking position obtained by performing striking and sound collection at separate positions, and (2) per striking position of the measured material obtained by the striking device. An image in which the defect position is displayed in a visually observable state by a combination of intensity information and (3) position information input in advance.

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