JPH07134060A - Method and device for detecting fracture by using ae sound - Google Patents

Abstract

PURPOSE:To accurately predict the internal fracture of an object to be inspected in real time by finding an internal fracture estimating value from the upper and lower limit values of the amplitude of acoustic emission (AE) sounds and the number of amplitudes exceeding the upper and lower limits within an arbitrary amplitude range of the AE sounds. CONSTITUTION:AE sound data are detected by vertically burying one of AE sound measuring tools 3 respectively constituted by fitting AE sensors 2 to both ends of waveguide rods 1 in an object 9 to be inspected having a slope and horizontally burying the other tool 3 in the object 9 and analyzing 21 and 22 the state and position of a fracture in the object 9. Namely, the upper and lower limit values of the amplitude of the AE sounds are calculated by deciding several tens to several hundreds evaluation data at a prescribed time from the amplitude frequency distribution of the AE sounds and finding a mean value and standard deviation of the amplitude. Thereafter, the number of the amplitudes exceeding the lower and upper limit values within an arbitrary amplitude range is found and the internal fracture is estimated at the prescribed time from the upper and lower limit values and the number of amplitude exceeding the limits. In addition, the level, time, and position of the internal fracture of the object 9 are discriminated in real time by continuously finding the estimating value at certain prescribed time with time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AE sound destruction detection method and an destruction detection device for detecting internal destruction of an object to be investigated using acoustic emission sound (hereinafter referred to as AE sound). For example, in a rock slide, the time from the appearance of a failure sign to the surface of the rock until the failure is short, no countermeasure can be taken at the stage when the surface is deformed, and there is a safety problem.

However, AE is used for monitoring such destruction.
The law is considered effective. Here, the AE sound means a sound emitted from the inside of the object, and the characteristic of the acquired AE sound (AE sound wave) can be used to determine the destruction state of the object that has generated the AE.

[0003]

2. Description of the Related Art Conventionally, when predicting the internal destruction of an object to be investigated by the AE method, generally, the occurrence frequency of the acquired AE sound is calculated by a counter 100, and the internal destruction of the investigation object is calculated from the obtained occurrence frequency. An AE sound monitoring system for monitoring the sound has been proposed (see FIG. 12).

However, the occurrence frequency of the AE sound differs depending on the object to be investigated, and it is not possible to accurately detect the internal destruction by simply detecting the occurrence frequency of the AE sound. Therefore, an AE sound monitoring system has been proposed which calculates the number of predetermined amplitudes and the range of amplitudes from the amplitude frequency distribution of the AE sounds and uses the number and the range to detect the internal destruction of the investigation target. .

There are various detection methods depending on the number of amplitudes used for calculation or the setting of the amplitude range. First, there are a method of using a cumulative number and a method of using a fixed number of times to determine the number of amplitudes to be calculated.
The method of calculating from points, the method of calculating by the maximum likelihood method or the method of least squares, and the method of calculating by the eye register can be considered.

Here, in determining the number of calculated amplitudes,
The method of using the cumulative number is a method of calculating using all the data acquired up to the time of calculating the gradient, and the method of using the fixed number of times is a method of calculating using the data acquired within a certain period of time. To do. Further, in the determination of the calculation range of the amplitude, the method of calculating from two preset points is a method of setting the upper limit amplitude value and the lower limit amplitude value used for the calculation in advance and calculating the gradient from those frequencies.

Next, the method of calculating by the maximum likelihood method or the least squares method means a method of calculating from the maximum likelihood estimated value on the assumption that the frequency distribution according to the amplitude scale has an exponential distribution. Further, the calculation method based on the register is a method of plotting a frequency distribution according to amplitude scale on a graph and drawing a straight line based on the register to calculate the gradient.

However, regarding the determination of the number of calculated amplitudes,
In the method using the cumulative number, the calculated value converges to a constant value as the number of data increases, so that there is a problem that, for example, internal destruction of the same scale in a certain investigation target cannot be expressed as a similar value. Further, in the method of using the fixed number of times for determining the number of calculated amplitudes, the number of data of the AE sound is different for each time, and therefore the value is calculated by using the number of different data for each time. Similar to the method using the number, there is a problem that the calculated value converges to a constant value as the number of data increases.

Further, regarding the determination of the amplitude calculation range,
In the method of calculating from two preset points, if the AE sound data is not distributed in the amplitude range set before the AE sound measurement, the value must be calculated in the amplitude range including the non-linear approximation section. There is. Further, in the method of calculating by the maximum likelihood method or the method of least squares, the lower limit value of the calculated amplitude is required. Therefore, like the above-mentioned method of calculating from two preset points, the amplitude range including the non-linear approximation section is used. There is a problem that the value has to be calculated.

Further, in the calculation method based on the register, only the linear approximation section can be judged by the register, but the calculation method cannot be said to be a real-time calculation method, and there is a problem that the calculation method lacks accuracy. .

[0011]

DISCLOSURE OF THE INVENTION The present invention is based on the conventional A
It was created in order to solve various problems existing in the method of predicting the internal destruction of an object to be investigated by the E method, and is not affected by the physical properties of the object to be investigated, and the internal destruction of the object to be investigated. An object of the present invention is to provide a destruction detection method and a destruction detection device using an AE sound that can be predicted accurately and in real time.

[0012]

In order to achieve the above-mentioned object, the present invention is constructed as follows. That is, the destruction detection method by the AE sound according to the first invention is a method of acquiring the AE sound generated along with the internal destruction behavior of the investigation target 9 and detecting the internal destruction by the AE sound. Based on the amplitude frequency distribution of, the evaluation data at a predetermined time is calculated from several tens to one of the evaluation data before the predetermined time.
It is determined to be up to 00, and the amplitude average value μ and the amplitude standard deviation value σ at a predetermined time are obtained from the condition, and further, the lower limit value al and the upper limit of the amplitude are calculated from the obtained amplitude average value μ and the amplitude standard deviation value σ. The value au is calculated, and within the arbitrary amplitude range, the frequency Nal whose amplitude is equal to or higher than the lower limit value al and the frequency Nau whose amplitude is equal to or higher than the upper limit value au are calculated, and from each of the calculated values al, au, Nal, Nau The destruction detection method by the AE sound according to the second aspect of the invention is configured to obtain the predicted internal breakdown value S at a predetermined time, and in the first aspect of the invention, the predicted internal breakdown value S at the predetermined time is continued along the elapsed time. It is constructed so that it can be obtained sequentially.

Furthermore, the destruction detecting device by the AE sound according to the third invention is the device according to the first invention or the second invention,
The acquisition of the AE sound is performed by installing the AE sound measuring tool 3 including the waveguide rod 1 and the AE sensors 2 and 2 attached to both ends of the waveguide rod 1 in a crossed state inside the object to be investigated. The destruction detecting device by AE sound according to the fourth aspect of the invention has a waveguide rod 1 attached to the inside of an object to be examined in a crossed state and AE attached to both ends of the waveguide rod 1. An AE sound measuring tool 3 provided with sensors 2 and 2, a destruction position analyzing means 10 for analyzing the internal destruction position of the investigation target from the AE sound measured by the AE sound measuring tool 3, and an AE sound measuring tool 3 From the AE sound measured by, the destruction state analysis means 11 for analyzing the internal destruction state of the investigation target, and the display means 12 for displaying the analyzed internal destruction position and the internal destruction state.
And a situation determination means 13 for determining the presence or absence of a dangerous situation from the analyzed internal destruction position and the internal destruction state, and a warning means 14 for issuing a warning when the dangerous situation is determined. Is configured.

[0014]

In the present invention, the frequency of occurrence of AE sound is used as a reference only as a parameter for so-called damage monitoring when predicting the internal damage of the investigation target from the acquired AE sound data. Then, in order to calculate the qualitatively and quantified parameters of the destruction monitoring, the evaluation data at a predetermined time is determined from several tens to several hundreds of the evaluation data before the predetermined time from the amplitude frequency distribution of the AE sound. .

Then, the amplitude average value μ and the amplitude standard deviation value σ at a predetermined time are obtained from these. Further, the lower limit value al and the upper limit value au of the amplitude are calculated from the obtained amplitude average value μ and amplitude standard deviation value σ. Within the arbitrary amplitude range, the frequency Nal whose amplitude is equal to or higher than the lower limit value al and the frequency Nau whose amplitude is equal to or higher than the upper limit value au are obtained, and the obtained respective values a
From l, au, Nal, Nau, the predicted internal fracture value S at a predetermined time is obtained.

Further, along with the elapsed time, the predicted internal damage value S at a certain predetermined time is continuously and successively obtained. Then, using this sequentially obtained predicted internal damage value S,
It is possible to construct an internal breakdown prediction system using AE sound that can determine the internal breakdown level, time, and position of the investigation target in real time.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the preferred embodiments shown in the drawings. (1) Calculation method of predicted internal fracture value S The AE sound measuring tools 3 and 3 in which the AE sensors 2 and 2 are attached to both ends of the waveguide rod 1 are attached to the investigation target 9 having a slope as shown in FIG. Install.

For the attachment, one AE sound measuring tool 3 is vertically embedded in the object 9 to be investigated, and the other AE sound measuring tool 3 is attached.
Is embedded horizontally in the object 9 to be investigated. With such a configuration, the slope collapse monitoring of the investigation target 9 is performed. Then, the AE sound data as shown in the table of FIG. 3 is obtained (measurement time is t1 to tn, and the unit of amplitude is dB).

Here, a method of calculating the predicted internal fracture value Si at time t1 will be described below. (However, the calculated number is α
To be individual. At this time, in order to set the upper and lower limit amplitude values, first, the amplitude average value and the amplitude standard deviation value are obtained (see FIGS. 4 and 5). Then, the amplitude average value and the amplitude standard deviation value are calculated as shown in FIG.

Next, a frequency NaL having an amplitude of aL or more and a frequency NaU having an amplitude of aU or more are obtained. These frequencies are obtained from FIG. And from the above, the estimated internal breakdown value Si
Is calculated as shown in FIG. Here, by using the sequentially determined internal fracture expected value Si, the temporal change of the internal fracture expected value Si as shown in FIG. 9 can be obtained.

Then, by monitoring the maximum value of this internal destruction predicted value Si or the time of abrupt decrease, it becomes possible to determine the large-scale destruction inside the investigation target which could not be determined conventionally. It should be noted that the increase in the internal fracture expected value Si means that the large-scale fracture (micro fracture) occurs more frequently than the large-scale fracture (macro fracture), and conversely, the internal fracture expected value Si. A drop in the number indicates that major destruction is predominant.

Next, the structure of the apparatus according to the present invention will be described with reference to the structure explanatory view shown in FIG. The AE sound acquired from the AE sensor 2 is amplified by the amplifier 20, and the AE sound is input to the destruction position analysis unit 21. Fracture position analysis unit 2
In 1, the destruction position in the investigation target 9 is analyzed from the input AE sound.

That is, as understood from FIG.
The estimated fracture surface position of the investigation target 9 is the frequency distribution of the position control points on the respective waveguide rods 1 and 1 of the AE sound measuring tool 3 installed vertically and the AE sound measuring tool 3 installed horizontally. You can get more. Then, in FIG. 11, the breaking position is estimated to be point A on the horizontal waveguide rod 1 and point B on the vertical waveguide rod 1.

Further, the AE sound is also input to the destruction state analysis unit 22. Then, the breakdown state analysis unit 22 analyzes the breakdown state in the investigation target 9 from the input AE sound. This breakdown state analysis is performed by continuously and successively calculating the internal breakdown predicted value S in real time.

Here, the analyzed internal breakdown position and internal breakdown state are displayed on the CRT 23, and by monitoring the CRT 23, the internal breakdown of the investigation target 9 can be monitored in real time. Further, the analyzed internal destruction position and internal destruction state are sent to the dangerous situation determination unit 24 at any time, and the dangerous situation determination unit 24 determines that there is a dangerous situation from the analyzed internal destruction position and internal destruction state. When the determination is made, a warning is issued to the warning unit 25, and the dangerous situation is promptly known.

[0026]

The present invention has the above construction. With the method and apparatus for detecting internal destruction by AE sound according to the present invention, it is possible to accurately and in real time predict the internal destruction of the object to be investigated without being affected by the physical properties of the object to be investigated. .

Further, since the predicted internal fracture value S obtained by the present invention is a parameter that does not depend on the measurement time, the quantitative value can be grasped even in the long-term monitoring of the structure, and the fracture can be predicted reliably. According to the present invention, it is possible to monitor a series of damages of an object to be investigated including internal damages of several kinds and plural kinds.

Further, by monitoring the change tendency of the internal fracture expected value S obtained successively and further grasping the position of the AE sound source, the time until the fracture and the fracture position can be judged.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of a fourth invention.

FIG. 2 is an explanatory view of an installation state of the AE sound measuring tool according to the present invention.

FIG. 3 is an explanatory diagram showing AE sound data obtained by the present invention.

FIG. 4 is an explanatory diagram referred to in order to calculate an average amplitude value and an amplitude standard deviation value.

FIG. 5 is an explanatory diagram referred to in order to calculate an average amplitude value and an amplitude standard deviation value.

FIG. 6 is an explanatory diagram showing a method of calculating an amplitude average value and an amplitude standard deviation value.

FIG. 7 is an explanatory diagram showing a calculation method for calculating a frequency whose amplitude is equal to or higher than an upper limit value and a lower limit value.

FIG. 8 is an explanatory diagram showing a method of calculating an internal fracture expected value S.

FIG. 9 is an explanatory diagram showing a secular change of an internal fracture expected value S.

FIG. 10 is a structural explanatory view showing the schematic structure of an embodiment of the fourth invention.

FIG. 11 is an explanatory diagram for estimating a fracture surface position.

FIG. 12 is an explanatory diagram showing a conventional internal damage detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Waveguide rod 2 AE sensor 3 AE sound measuring tool 9 Investigation object 10 Breakage position analysis means 11 Breakage state analysis means 12 Display means 13 Situation determination means 14 Warning means

Claims (4)

[Claims] 1. A method for acquiring an AE sound that accompanies the internal destruction behavior of an object to be investigated (9) and detecting the internal destruction by the AE sound, which is obtained at a predetermined time from the amplitude frequency distribution of the AE sound. The evaluation data in 10 to several hundreds of evaluation data before the predetermined time
The amplitude average value μ and the amplitude standard deviation value σ at a predetermined time are determined from the conditions, and the amplitude lower limit value al and the upper limit value of the amplitude are calculated from the obtained amplitude average value μ and the amplitude standard deviation value σ. au is calculated, and within a given amplitude range, a frequency Nal whose amplitude is equal to or higher than a lower limit value al and a frequency Nau whose amplitude is equal to or higher than an upper limit value au are obtained, and a predetermined value is obtained from each of the obtained values al, au, Nal, Nau. A method for detecting destruction by an AE sound, characterized in that an expected internal destruction value S at a time is obtained. 2. The method for detecting damage by an AE sound according to claim 1, wherein the predicted internal damage value S at a predetermined time is continuously and sequentially obtained along the elapsed time. 3. The method according to claim 1 or 2,
AE sound is acquired by using an AE equipped with a waveguide rod (1) and AE sensors (2, 2) attached to both ends of the waveguide rod (1).
A device for detecting breakage by AE sound, characterized in that the sound measuring tool (3) is installed inside the object to be examined in a crossed state. 4. A waveguide rod (1) mounted in a crossed state inside an object (9) to be investigated, and AE sensors (2, 2) attached to both ends of the waveguide rod (1). An AE sound measuring tool (3) provided with the AE sound measuring tool (3), and an AE sound measured by the AE sound measuring tool (3).
0) and the AE sound measured by the AE sound measuring tool (3), the failure state analysis means (1) for analyzing the internal failure state of the investigation target.
1), display means (12) for displaying the analyzed internal breakdown position and internal breakdown state, and status determination means (13) for determining the presence or absence of a dangerous situation from the analyzed internal breakdown position and internal breakdown state. An AE sound destruction detection device comprising: warning means (14) for issuing a warning when it is determined that a dangerous situation exists.