Wood structure damage detection method and system based on acoustic emission effective energy density

Abstract

The present invention relates to a wood structure damage detection method and system based on the effective energy density of acoustic emission, and belongs to the technical field of wood non-destructive testing. The method includes five steps: installing an acoustic emission sensor, collecting acoustic emission signals, processing effective acoustic emission signals, calculating effective energy density, and evaluating wood damage levels. The present invention directly implements in-situ dynamic non-destructive testing of wood structures based on the effective energy density index of the original acoustic emission signal, and then gives a dynamic damage level evaluation report, providing a diagnostic basis for the safe and healthy use of wood structures.

Description

Technical Field

[0001] The invention belongs to the technical field of wood nondestructive testing, and in particular relates to a wood structure damage detection method and system based on acoustic emission effective energy density. Background Art

[0002] Wood is prone to microscopic and macroscopic damage during use, and the accumulation of damage can lead to structural failure and serious consequences such as collapse. Therefore, dynamic monitoring of the degree of wood damage is the key to ensuring the safe use of wooden structures.

[0003] As a non-metallic material, wood has very limited non-destructive testing methods. Currently, the most widely used non-destructive testing methods are based on the principle of mechanical waves. Such methods mainly include three detection technologies: stress wave, ultrasonic wave and acoustic emission. Among them, stress wave and ultrasonic wave are essentially an active detection method based on the excitation-response mode, which are usually only applicable to local static non-destructive testing. Acoustic emission technology is a global passive dynamic detection method. Its basic principle is that when wood is damaged, it releases strain energy in the form of mechanical waves, and this mechanical wave is also called acoustic emission signal. Therefore, by collecting and analyzing the acoustic emission signals generated during the use of wood, the degree of damage and health level of wood can be objectively evaluated.

[0004] The application of acoustic emission technology in wood can be traced back to the 1960s, but related research mainly focuses on wood acoustic emission signals and their propagation characteristics. In the early days, due to the limitations of signal acquisition equipment, the damage process of wood was qualitatively described mainly through the measurement parameters given by the acoustic emission instrument. With the rapid development of signal acquisition and storage equipment, in the past decade or so, many scholars have conducted in-depth research on the propagation characteristics of acoustic emission signals in wood, such as propagation speed, energy attenuation, and acoustic emission source positioning, from the perspective of acoustic emission waveforms, thus providing a new way for wood damage monitoring based on acoustic emission.

[0005] Existing patents for acoustic emission nondestructive testing of wood mainly include aspects such as acoustic emission signal acquisition, acoustic emission signal processing, and acoustic emission detection related devices. Among them, patent CN104634878A is a wood damage monitoring method based on acoustic emission technology, which uses wireless transmission to collect acoustic emission signals detected on site. Patent CN116297867A is a wood crack depth detection method based on acoustic emission multi-parameter coupling, which invented a wood crack depth detection method based on acoustic emission technology. Patent CN110196283A is a wood structure damage acoustic emission nondestructive testing method based on instantaneous frequency, which qualitatively evaluates the degree of damage to the wood structure by analyzing the instantaneous frequency of the acoustic emission signal during the wood damage process. Patent CN117783294B is a wood damage dynamic detection method and system based on acoustic emission energy entropy, which evaluates the degree of damage to the wood by calculating the signal energy entropy after wavelet decomposition.

[0006] At present, in the detection of wood damage using acoustic emission technology, it is necessary to perform time-frequency domain analysis or decomposition on the original collected acoustic emission signal. Patent CN110196283A is a method for nondestructive detection of wood structure damage based on instantaneous frequency. It is necessary to perform empirical mode decomposition on the original acoustic emission signal and then calculate the corresponding instantaneous frequency; Patent CN117783294B is a method and system for dynamic detection of wood damage based on acoustic emission energy entropy. It is necessary to perform wavelet packet decomposition on the original acoustic emission signal and then calculate the energy entropy. Although the instantaneous frequency and energy entropy indicators proposed in these patents can objectively reflect the degree of wood damage, in order to obtain these indicators, the acquisition system needs to have a very high data processing capability, which seriously limits the promotion and use of these methods in practical applications. Secondly, since the energy of the acoustic emission signal is the most direct reflection of the strain energy released when the wood is damaged, the energy of the acoustic emission signal is the most critical and essential basis for evaluating wood damage. However, there is no report on the method of directly using the energy of the acoustic emission signal to evaluate the degree of wood damage.

[0007] Therefore, how to overcome the shortcomings of the existing technology is an urgent problem to be solved in the field of wood non-destructive testing technology. Summary of the invention

[0008] The purpose of the present invention is to solve the deficiencies of the prior art and to provide a method and system for detecting damage to wooden structures based on the effective energy density of acoustic emission.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0010] The method for detecting damage of wood structures based on effective energy density of acoustic emission includes the following steps:

[0011] Step (1), installing at least one acoustic emission sensor in the length direction of the wood to be tested;

[0012] Step (2) acquires the original acoustic emission signal data collected by the acoustic emission sensor in real time; when the signal amplitude is lower than the set threshold, it is deemed that no damage has occurred and no signal is collected; when the signal amplitude reaches or exceeds the set threshold, signal collection begins, and when the signal amplitude is lower than 10% of the set threshold for 20 consecutive times, signal collection stops; the collected signal is regarded as a valid acoustic emission signal and recorded as X, where X=(x1,x2,...,x N );

[0013] Where N is the length of signal X; x1 is the amplitude of the signal collected for the first time, x2 is the amplitude of the signal collected for the second time, and x N is the signal amplitude collected for the Nth time; the set threshold is 0.5V;

[0014] Step (3), extract each signal x from X in turn i , if |x i | is greater than or equal to 0.5V, then the corresponding signal amplitude x i Record it in the variable Y. When recording, record it in the order of collection to obtain the effective acoustic emission signal Y, Y=(y1,y2,...,y S );

[0015] Among them, x i is the signal amplitude collected for the i-th time, i=1,2,...,N; S is the length value of signal Y; y1 is the signal amplitude of the first signal in X whose absolute value is greater than or equal to 0.5V, y2 is the signal amplitude of the second signal in X whose absolute value is greater than or equal to 0.5V, y S is the signal amplitude of the Sth signal in X whose absolute value is greater than or equal to 0.5V;

[0016] Step (4), calculate the effective energy density ρ of the collected signal, the calculation formula is as follows:

[0017] ;

[0018] Among them, y k is the signal amplitude of the kth signal in X whose absolute value is greater than or equal to 0.5V; k=1,2,...,S;

[0019] Step (5), evaluating the wood damage level according to the effective energy density:

[0020] when , it is a minor injury;

[0021] when , it is moderate injury;

[0022] when When , it is a severe injury;

[0023] when When it is serious injury.

[0024] Furthermore, an acoustic emission sensor is installed every 80 cm in the length direction of the wood to be tested.

[0025] Furthermore, in step (1), a UTM5105 electronic universal mechanical testing machine is used for the test, and an acoustic emission sensor is installed in the length direction of the wood to be tested, and the acoustic emission sensor is 80 mm away from the pressure head of the mechanical testing machine.

[0026] Furthermore, in step (4), the value range of ρ is [0,1].

[0027] Furthermore, the method also includes the following steps: recording the dynamic effective energy density and damage level, wherein the damage level is divided into four levels: slight, moderate, severe, and serious damage.

[0028] Furthermore, the method further comprises the following steps: recording the waveform of Y, and when Y is assessed as moderately damaged, marking a warning at the corresponding waveform peak;

[0029] When Y is assessed as severely damaged, a warning word is marked at the corresponding waveform peak;

[0030] When Y is assessed as severely damaged, the word "Danger" is marked at the corresponding waveform peak.

[0031] The present invention also provides a wood structure damage detection system based on effective energy density of acoustic emission, which adopts the above-mentioned wood structure damage detection method based on effective energy density of acoustic emission, and includes: an acoustic emission sensor, a preamplifier, a high-speed data acquisition card, a computer and a signal acquisition trigger switch;

[0032] The acoustic emission sensor is installed in the length direction of the wood to be tested, and is used to collect the original acoustic emission signal of the wood to be tested;

[0033] The input end of the preamplifier is connected to the output end of the acoustic emission sensor, and is used to amplify the collected original acoustic emission signal of the wood to be tested;

[0034] The output end of the preamplifier is connected to the input end of the high-speed data acquisition card through a signal acquisition trigger switch; the high-speed data acquisition card is used to collect the original acoustic emission signal amplified by the preamplifier;

[0035] When the amplitude of the original acoustic emission signal reaches or exceeds the set threshold, the signal acquisition trigger switch is closed;

[0036] The high-speed data acquisition card transmits the acquired original acoustic emission signal to the Lab VIEW data processing platform of the computer, and then performs detection according to steps (2) to (5).

[0037] Further, the preamplifier is a 40dB preamplifier.

[0038] Furthermore, the high-speed data acquisition card is an 8-channel high-speed data acquisition card, and the signal acquisition frequency is set to 500kHz.

[0039] Aiming at the problem of strain energy release in the process of wood damage, the present invention proposes a method for calculating the effective energy density based on the original acoustic emission signal. Aiming at the problem of evaluating the degree of wood damage, the present invention proposes a grading evaluation method based on the effective energy density of the acoustic emission signal.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) Patents CN110196283A and CN117783294B both require continuous acquisition of acoustic emission signals, which not only greatly occupies storage space, but also acquires a lot of redundant signals, which easily affects the accuracy of the results; while the present invention can dynamically trigger signal acquisition according to the amplitude of the acoustic emission signal, saving the storage space for acquisition;

[0042] (2) Patent CN110196283A requires complex processing such as filtering, wavelet reconstruction, and EMD decomposition of the original acoustic emission signal, while the present invention directly performs simple calculations on the original collected acoustic emission signal to obtain the effective energy density index, effectively simplifying the processing process of wood acoustic emission signals;

[0043] (3) Patent CN117783294B divides wood damage into three evaluation levels: mild, moderate, and severe based on acoustic emission signals, while the classification of the present invention is more refined. The present invention provides four evaluation levels for wood damage: mild, moderate, severe, and serious damage, which can more effectively and accurately adopt different subsequent treatment methods for different levels;

[0044] (4) Patent CN117783294B requires wavelet packet decomposition of the original acoustic emission to realize wood damage detection; while the present invention directly realizes in-situ dynamic non-destructive testing of wood structures based on the effective energy density index of the original acoustic emission signal, and then provides a dynamic damage level evaluation report, providing a diagnostic basis for the safe and healthy use of wood structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a flow chart of the wood structure damage detection method based on the effective energy density of acoustic emission of the present invention;

[0046] Figure 2 It is a structural schematic diagram of a wood structure damage detection system based on effective energy density of acoustic emission according to the present invention;

[0047] Figure 3 The waveform of Y and the corresponding annotation diagram of application example 1;

[0048] Figure 4 The waveform of Y obtained by collecting and processing the first acoustic emission sensor in application example 2 and the corresponding annotation diagram;

[0049] Figure 5 The waveform of Y obtained by collecting and processing the second acoustic emission sensor in application example 2 and the corresponding annotation diagram. DETAILED DESCRIPTION

[0050] The present invention is further described in detail below in conjunction with embodiments.

[0051] Those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the art or the product specifications are used. If the manufacturer of the materials or equipment used is not specified, they are all conventional products that can be purchased.

[0052] Example 1

[0053] like Figure 1 As shown, the wood structure damage detection method based on the effective energy density of acoustic emission includes the following steps:

[0054] Step (1), installing at least one acoustic emission sensor in the length direction of the wood to be tested;

[0055] Step (2) acquires the original acoustic emission signal data collected by the acoustic emission sensor in real time; when the signal amplitude is lower than the set threshold, it is deemed that no damage has occurred and no signal is collected; when the signal amplitude reaches or exceeds the set threshold, signal collection begins, and when the signal amplitude is lower than 10% of the set threshold for 20 consecutive times, signal collection stops; the collected signal is regarded as a valid acoustic emission signal and recorded as X, where X=(x1,x2,...,x N );

[0056] Where N is the length of signal X; x1 is the amplitude of the signal collected for the first time, x2 is the amplitude of the signal collected for the second time, and x N is the signal amplitude collected for the Nth time; the set threshold is 0.5V;

[0057] Step (3), extract each signal x from X in turn i , if |xi | is greater than or equal to 0.5V, then the corresponding signal amplitude x i Record it in the variable Y. When recording, record it in the order of collection to obtain the effective acoustic emission signal Y, Y=(y1,y2,...,y S );

[0058] Among them, x i is the signal amplitude collected for the i-th time, i=1,2,...,N; S is the length value of signal Y; y1 is the signal amplitude of the first signal in X whose absolute value is greater than or equal to 0.5V, y2 is the signal amplitude of the second signal in X whose absolute value is greater than or equal to 0.5V, y S is the signal amplitude of the Sth signal in X whose absolute value is greater than or equal to 0.5V;

[0059] Step (4), calculate the effective energy density ρ of the collected signal, the calculation formula is as follows:

[0060] ;

[0061] Among them, y k is the signal amplitude of the kth signal in X whose absolute value is greater than or equal to 0.5V; k=1,2,...,S;

[0062] Step (5), evaluating the wood damage level according to the effective energy density:

[0063] when , it is a minor injury;

[0064] when , it is moderate injury;

[0065] when When , it is a severe injury;

[0066] when When it is serious injury.

[0067] Example 2

[0068] like Figure 1 As shown, the wood structure damage detection method based on the effective energy density of acoustic emission includes the following steps:

[0069] Step (1), installing at least one acoustic emission sensor in the length direction of the wood to be tested;

[0070] Step (2) acquires the original acoustic emission signal data collected by the acoustic emission sensor in real time; when the signal amplitude is lower than the set threshold, it is deemed that no damage has occurred and no signal is collected; when the signal amplitude reaches or exceeds the set threshold, signal collection begins, and when the signal amplitude is lower than 10% of the set threshold for 20 consecutive times, signal collection stops; the collected signal is regarded as a valid acoustic emission signal and recorded as X, where X=(x1,x2,...,x N );

[0071] Where N is the length of signal X; x1 is the amplitude of the signal collected for the first time, x2 is the amplitude of the signal collected for the second time, and x N is the signal amplitude collected for the Nth time; the set threshold is 0.5V;

[0072] Step (3), extract each signal x from X in turn i , if |x i | is greater than or equal to 0.5V, then the corresponding signal amplitude x i Record it in the variable Y. When recording, record it in the order of collection to obtain the effective acoustic emission signal Y, Y=(y1,y2,...,y S );

[0073] Among them, x i is the signal amplitude collected for the i-th time, i=1,2,...,N; S is the length value of signal Y; y1 is the signal amplitude of the first signal in X whose absolute value is greater than or equal to 0.5V, y2 is the signal amplitude of the second signal in X whose absolute value is greater than or equal to 0.5V, y S is the signal amplitude of the Sth signal in X whose absolute value is greater than or equal to 0.5V;

[0074] Step (4), calculate the effective energy density ρ of the collected signal, the calculation formula is as follows:

[0075] ;

[0076] Among them, y k is the signal amplitude of the kth signal in X whose absolute value is greater than or equal to 0.5V; k=1,2,...,S;

[0077] Step (5), evaluating the wood damage level according to the effective energy density:

[0078] when , it is a minor injury;

[0079] when , it is moderate injury;

[0080] when When , it is a severe injury;

[0081] when When it is serious injury.

[0082] An acoustic emission sensor is installed every 80 cm in the length direction of the wood to be tested.

[0083] In step (1), a UTM5105 electronic universal mechanical testing machine is used for the test, and an acoustic emission sensor is installed in the length direction of the wood to be tested, and the acoustic emission sensor is 80 mm away from the pressure head of the mechanical testing machine.

[0084] In step (4), the value range of ρ is [0,1].

[0085] Example 3

[0086] like Figure 1 As shown, the wood structure damage detection method based on the effective energy density of acoustic emission includes the following steps:

[0087] Step (1), installing at least one acoustic emission sensor in the length direction of the wood to be tested;

[0088] Step (2) acquires the original acoustic emission signal data collected by the acoustic emission sensor in real time; when the signal amplitude is lower than the set threshold, it is deemed that no damage has occurred and no signal is collected; when the signal amplitude reaches or exceeds the set threshold, signal collection begins, and when the signal amplitude is lower than 10% of the set threshold for 20 consecutive times, signal collection stops; the collected signal is regarded as a valid acoustic emission signal and recorded as X, where X=(x1,x2,...,x N );

[0089] Where N is the length of signal X; x1 is the amplitude of the signal collected for the first time, x2 is the amplitude of the signal collected for the second time, and x N is the signal amplitude collected for the Nth time; the set threshold is 0.5V;

[0090] Step (3), extract each signal x from X in turn i , if |x i | is greater than or equal to 0.5V, then the corresponding signal amplitude x i Record it in the variable Y. When recording, record it in the order of collection to obtain the effective acoustic emission signal Y, Y=(y1,y2,...,y S );

[0091] Among them, x iis the signal amplitude collected for the i-th time, i=1,2,...,N; S is the length value of signal Y; y1 is the signal amplitude of the first signal in X whose absolute value is greater than or equal to 0.5V, y2 is the signal amplitude of the second signal in X whose absolute value is greater than or equal to 0.5V, y S is the signal amplitude of the Sth signal in X whose absolute value is greater than or equal to 0.5V;

[0092] Step (4), calculate the effective energy density ρ of the collected signal, the calculation formula is as follows:

[0093] ;

[0094] Among them, y k is the signal amplitude of the kth signal in X whose absolute value is greater than or equal to 0.5V; k=1,2,...,S;

[0095] Step (5), evaluating the wood damage level according to the effective energy density:

[0096] when , it is a minor injury;

[0097] when , it is moderate injury;

[0098] when When , it is a severe injury;

[0099] when When it is serious injury.

[0100] An acoustic emission sensor is installed every 80 cm in the length direction of the wood to be tested.

[0101] In step (1), a UTM5105 electronic universal mechanical testing machine is used for the test, and an acoustic emission sensor is installed in the length direction of the wood to be tested, and the acoustic emission sensor is 80 mm away from the pressure head of the mechanical testing machine.

[0102] In step (4), the value range of ρ is [0,1].

[0103] The method also includes the following steps: recording the dynamic effective energy density and damage level, wherein the damage level is divided into four levels: slight, moderate, severe and serious damage.

[0104] Record the waveform of Y. When Y is assessed as moderately damaged, mark the corresponding peak of the waveform with a warning.

[0105] When Y is assessed as severely damaged, a warning word is marked at the corresponding waveform peak;

[0106] When Y is assessed as severely damaged, the word "Danger" is marked at the corresponding waveform peak.

[0107] Example 4

[0108] like Figure 2 As shown, a wood structure damage detection system based on acoustic emission effective energy density adopts the wood structure damage detection method based on acoustic emission effective energy density described in Example 1, Example 2 or Example 3, comprising: an acoustic emission sensor 1, a preamplifier 2, a high-speed data acquisition card 3, a computer 4 and a signal acquisition trigger switch 5;

[0109] The acoustic emission sensor 1 is installed in the length direction of the wood to be detected, and is used to collect the original acoustic emission signal of the wood to be detected;

[0110] The input end of the preamplifier 2 is connected to the output end of the acoustic emission sensor 1, and is used to amplify the collected original acoustic emission signal of the wood to be detected;

[0111] The output end of the preamplifier 2 is connected to the input end of the high-speed data acquisition card 3 through the signal acquisition trigger switch 5; the high-speed data acquisition card 3 is used to collect the original acoustic emission signal amplified by the preamplifier 2;

[0112] When the amplitude of the original acoustic emission signal reaches or exceeds the set threshold, the signal acquisition trigger switch 5 is closed;

[0113] The high-speed data acquisition card 3 transmits the acquired original acoustic emission signal to the Lab VIEW data processing platform of the computer 4, and then performs detection according to steps (2) to (5).

[0114] Example 5

[0115] like Figure 2 As shown, a wood structure damage detection system based on acoustic emission effective energy density adopts the wood structure damage detection method based on acoustic emission effective energy density described in Example 1, Example 2 or Example 3, comprising: an acoustic emission sensor 1, a preamplifier 2, a high-speed data acquisition card 3, a computer 4 and a signal acquisition trigger switch 5;

[0116] The acoustic emission sensor 1 is installed in the length direction of the wood to be detected, and is used to collect the original acoustic emission signal of the wood to be detected;

[0117] The input end of the preamplifier 2 is connected to the output end of the acoustic emission sensor 1, and is used to amplify the collected original acoustic emission signal of the wood to be detected;

[0118] The output end of the preamplifier 2 is connected to the input end of the high-speed data acquisition card 3 through the signal acquisition trigger switch 5; the high-speed data acquisition card 3 is used to collect the original acoustic emission signal amplified by the preamplifier 2;

[0119] When the amplitude of the original acoustic emission signal reaches or exceeds the set threshold, the signal acquisition trigger switch 5 is closed;

[0120] The high-speed data acquisition card 3 transmits the acquired original acoustic emission signal to the Lab VIEW data processing platform of the computer 4, and then performs detection according to steps (2) to (5) to output a damage level evaluation report. The report includes the effective energy density and damage level; it also includes the waveform of Y. When Y is evaluated as moderate damage, the word "attention" is marked at the corresponding waveform peak;

[0121] When Y is assessed as severely damaged, a warning word is marked at the corresponding waveform peak;

[0122] When Y is assessed as severely damaged, the word "Danger" is marked at the corresponding waveform peak.

[0123] Preamplifier 2 is a 40dB preamplifier.

[0124] The high-speed data acquisition card 3 is an 8-channel high-speed data acquisition card, and the signal acquisition frequency is set to 500kHz.

[0125] Application Example 1

[0126] Beech was used as the wood to be tested. The specifications of the wood to be tested were 300 mm×20 mm×20 mm (axial×tangential×radial). A three-point bending test was carried out using a UTM5105 electronic universal mechanical testing machine. The test parameters were set according to ASTM-D198-21a, and the loading speed was 2 mm / min.

[0127] Based on NI USB-6366 acquisition card and LabVIEW software, the acoustic emission sensor used is RS-2A single-ended resonant AE sensor with a resonant frequency of 150kHz. The preamplifier uses a PAI preamplifier with a gain of 40dB to amplify the signal received by the acoustic emission sensor. The maximum amplitude of the signal is 10V, and the sampling frequency is set to 500kHz.

[0128] The acoustic emission sensor was placed vertically at a distance of 80 mm from the pressure head of the mechanical testing machine. The pressure head was located in the center of the specimen and pressure was applied continuously at a constant speed of 2 mm / min.

[0129] In order to illustrate the advantages of the present invention in more detail, the time interval is refined. In this example, 9 effective acoustic emission signals (such as Figure 3), and the damage level is divided according to the effective energy density index, and the warning information of "Attention!", "Warning!" and "Danger!" are respectively marked in the waveform for the moderate, severe and serious levels, as shown in Table 1, which provides an intuitive criterion for dynamic damage monitoring of wooden structures. Compared with the prior art, the present invention has the following advantages: 1) Only effective acoustic emission signals are collected, which effectively reduces the signal storage space; 2) The effective energy density index can be calculated without any time-frequency domain analysis of the original collected signals, so as to evaluate the degree of damage from the essence of energy. 3) The warning information is directly marked on the acoustic emission waveform, which is more intuitive and effective.

[0130] Table 1

[0131]

[0132] Application Example 2

[0133] Pinus sylvestris var. mongolica was used as the wood to be tested. The specifications of the wood to be tested were 1500 mm×30 mm×60 mm (axial×tangential×radial). A three-point bending test was carried out using a UTM5105 electronic universal mechanical testing machine. The test parameters were set according to ASTM-D198-21a, and the loading speed was 2 mm / min.

[0134] Based on NI USB-6366 acquisition card and LabVIEW software, the acoustic emission sensor used is RS-2A single-ended resonant AE sensor with a resonant frequency of 150kHz. The preamplifier uses a PAI preamplifier with a gain of 40dB to amplify the signal received by the acoustic emission sensor. The maximum amplitude of the signal is 10V, and the sampling frequency is set to 500kHz.

[0135] The acoustic emission sensors were placed vertically at 80 mm and 880 mm away from the pressure head of the mechanical testing machine. The two emission sensors were placed on the same side of the pressure head. The pressure head was 200 mm away from the end face of the specimen, and pressure was applied continuously at a constant speed of 2 mm / min.

[0136] In order to illustrate the advantages of the present invention in more detail, the time interval is refined. In this example, the first acoustic emission sensor extracts 6 effective acoustic emission signals (such as Figure 4 ), the second acoustic emission sensor extracted two valid acoustic emission signals from the 200-second test (such as Figure 5 );

[0137] Because the first acoustic emission sensor is closer to the pressure head, the number and amplitude of the effective acoustic emission signals are higher than the effective acoustic emission signals collected by the second acoustic emission sensor. The two acoustic emission sensors detected the moderate damage level of the wood to be tested at 14.37 seconds and 14.38 seconds respectively, and the effective energy density calculated by the signal collected by the first acoustic emission sensor was significantly higher than the effective energy density calculated by the signal collected by the second acoustic emission sensor, indicating that the damage location is closer to the first acoustic emission sensor, which is consistent with the test results.

[0138] Table 2

[0139]

[0140] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A wood structure damage detection method based on acoustic emission effective energy density, characterized in that: The steps include: Step (1), installing at least one acoustic emission sensor in the length direction of the wood to be tested; Step (2) acquires the original acoustic emission signal data collected by the acoustic emission sensor in real time; when the signal amplitude is lower than the set threshold, it is deemed that no damage has occurred and no signal is collected; when the signal amplitude reaches or exceeds the set threshold, signal collection begins, and when the signal amplitude is lower than 10% of the set threshold for 20 consecutive times, signal collection stops; the collected signal is regarded as a valid acoustic emission signal and recorded as X, where X=(x1,x2,...,x N ); Where N is the length of signal X; x1 is the amplitude of the signal collected for the first time, x2 is the amplitude of the signal collected for the second time, and x N is the signal amplitude collected for the Nth time; the set threshold is 0.5V; Step (3), extract each signal x from X in turn i , if |x i | is greater than or equal to 0.5V, then the corresponding signal amplitude x i Record it in the variable Y. When recording, record it in the order of collection to obtain the effective acoustic emission signal Y, Y=(y1,y2,...,y S ); Among them, x i is the signal amplitude collected for the i-th time, i=1,2,...,N; S is the length value of signal Y; y1 is the signal amplitude of the first signal in X whose absolute value is greater than or equal to 0.5V, y2 is the signal amplitude of the second signal in X whose absolute value is greater than or equal to 0.5V, y S is the signal amplitude of the Sth signal in X whose absolute value is greater than or equal to 0.5V; Step (4), calculate the effective energy density ρ of the collected signal, the calculation formula is as follows: ； Among them, y k is the signal amplitude of the kth signal in X whose absolute value is greater than or equal to 0.5V; k=1,2,...,S; Step (5), evaluating the wood damage level according to the effective energy density: when , it is a minor injury; when , it is moderate injury; when When , it is a severe injury; when When it is serious injury.

2. The method for detecting damage to wooden structures based on effective energy density of acoustic emission according to claim 1, characterized in that: An acoustic emission sensor is installed every 80 cm in the length direction of the wood to be tested.

3. The method for detecting damage to wooden structures based on effective energy density of acoustic emission according to claim 1, characterized in that: In step (1), a UTM5105 electronic universal mechanical testing machine is used for the test, and an acoustic emission sensor is installed in the length direction of the wood to be tested, and the acoustic emission sensor is 80 mm away from the pressure head of the mechanical testing machine.

4. The method for detecting damage to wooden structures based on effective energy density of acoustic emission according to claim 1, characterized in that: In step (4), the value range of ρ is [0,1].

5. The method for detecting damage to wooden structures based on effective energy density of acoustic emission according to claim 1, characterized in that: The method also includes the following steps: recording the dynamic effective energy density and damage level, wherein the damage level is divided into four levels: slight, moderate, severe and serious damage.

6. The method for detecting damage to wooden structures based on effective energy density of acoustic emission according to claim 1, characterized in that: The steps include: recording the waveform of Y, and when Y is assessed as moderately damaged, marking a warning at the corresponding waveform peak; When Y is assessed as severely damaged, a warning word is marked at the corresponding waveform peak; When Y is assessed as severely damaged, the word "Danger" is marked at the corresponding waveform peak.

7. A wood structure damage detection system based on effective energy density of acoustic emission, using any one of the wood structure damage detection methods based on effective energy density of acoustic emission according to claims 1 to 6, characterized in that: include: Acoustic emission sensor, preamplifier, high-speed data acquisition card, computer and signal acquisition trigger switch; The acoustic emission sensor is installed in the length direction of the wood to be tested, and is used to collect the original acoustic emission signal of the wood to be tested; The input end of the preamplifier is connected to the output end of the acoustic emission sensor, and is used to amplify the collected original acoustic emission signal of the wood to be tested; The output end of the preamplifier is connected to the input end of the high-speed data acquisition card through a signal acquisition trigger switch; the high-speed data acquisition card is used to collect the original acoustic emission signal amplified by the preamplifier; When the amplitude of the original acoustic emission signal reaches or exceeds the set threshold, the signal acquisition trigger switch is closed; The high-speed data acquisition card transmits the acquired original acoustic emission signal to the Lab VIEW data processing platform of the computer, and then performs detection according to steps (2) to (5).

8. The wood structure damage detection system based on acoustic emission effective energy density according to claim 7 is characterized in that: The preamplifier is a 40dB preamplifier.

9. The wood structure damage detection system based on acoustic emission effective energy density according to claim 7, characterized in that: The high-speed data acquisition card is an 8-channel high-speed data acquisition card, and the signal acquisition frequency is set to 500kHz.

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