Wood nondestructive testing method and system based on acoustic emission damage factors

Abstract

The invention relates to a wood nondestructive testing method and system based on acoustic emission damage factors, and belongs to the technical field of wood dynamic nondestructive testing. The method comprises the steps of installing an acoustic emission sensor, collecting an effective acoustic emission signal, calculating a root mean square value, calculating a peak value, calculating a waveform index, calculating a damage factor and evaluating the wood damage grade according to the damage factor. Only effective acoustic emission signals are collected, and the signal storage space is effectively reduced; the damage factor can be directly calculated without any time-frequency domain analysis on the originally acquired signal, so that the damage degree evaluation is realized; damage factors can be directly marked on an acoustic emission oscillogram, and the method is more visual and effective.

Description

Technical Field

[0001] The present invention belongs to the technical field of dynamic non-destructive testing of wood, and particularly relates to a non-destructive testing method and system for wood based on acoustic emission damage factors. Background Art

[0002] As an important engineering material, during the use process of wood, due to its own defects and changes in environmental factors, it is extremely easy to produce microscopic and macroscopic damage phenomena. Even with the accumulation of damage, it will lead to structural failure and cause serious consequences. Traditional wood damage assessment methods often have limitations and cannot accurately and real-time reflect the degree of wood damage. According to the principle of acoustic emission, wood will release strain energy in the form of mechanical waves during the damage process, and this mechanical wave is also called the acoustic emission phenomenon. Therefore, by collecting and analyzing the acoustic emission signals released during the wood damage process, the dynamic evaluation of the degree of wood damage can be realized.

[0003] Existing methods for monitoring wood damage using acoustic emission technology include: the invention patent CN108267510A, a health monitoring system and method for wood components, which proposes a wood structure monitoring system based on a wireless acoustic emission sensor network. The system collects the acoustic emission signals of wood components through acoustic emission sensors, and the first microcontroller extracts the characteristic parameters of the acoustic emission signals and sends them to the control terminal after processing by the differential compression algorithm to obtain the health detection results of the wood components. The acoustic emission characteristic parameters sent to the control terminal include amplitude, rise time, duration, ring count, and hit count. Although this invention proposes to determine the health detection results of wood components by analyzing the acoustic emission characteristic parameters, it does not specify a specific analysis and evaluation method. The invention patent CN118465085A, a method for evaluating the characteristics of wood damage evolution based on active acoustic emission, which proposes a method for evaluating the characteristics of wood damage evolution based on acoustic emission. First, the wood damage evolution process is divided into an initial stage, a linear damage accumulation stage, a non-linear damage accumulation stage, and a failure stage. Then, 4 acoustic emission parameters (ring count, amplitude, energy, rise time) in the wood damage stage are extracted and subjected to clustering processing, and then the damage characteristic index is analyzed to classify the wood damage type. Finally, the RA-AF correlation analysis method is used to quantitatively analyze the wood damage mode to obtain the corresponding damage form. This invention mainly focuses on the discrimination of wood damage types and forms and cannot evaluate the degree of wood damage. Although the above technical solutions all use acoustic emission technology to achieve wood damage monitoring, none of them propose a quantitative evaluation of the degree of wood damage.

[0004] In addition, CN117783294A discloses a method and system for dynamic detection of wood damage based on acoustic emission energy entropy, which evaluates the degree of wood damage by calculating the energy entropy of the signal after wavelet decomposition. However, it is necessary to perform wavelet packet decomposition on the original acoustic emission signal before calculating the energy entropy. Although the energy entropy indexes proposed in the patent technical solution can objectively reflect the degree of wood damage, in order to obtain these indexes, the acquisition system needs to have a very high data processing ability, which severely limits the popularization and application of these methods in practical applications.

[0005] Therefore, how to overcome the deficiencies of the prior art is an urgent problem to be solved in the field of current wood dynamic non-destructive testing technology. Summary of the Invention

[0006] The purpose of the present invention is to solve the deficiencies of the prior art and provide a method and system for non-destructive testing of wood based on acoustic emission damage factors.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for non-destructive testing of wood based on acoustic emission damage factors includes the following steps: Step (1), install at least one acoustic emission sensor in the length direction of the wood to be detected; Step (2), obtain 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 considered that no damage occurs and the signal is not collected; when the signal amplitude reaches or exceeds the set threshold, start collecting the signal, and stop collecting the signal when the signal amplitude is continuously lower than 10% of the set threshold for 20 times; regard the collected signal as a valid acoustic emission signal and denote it as X, X = (x 1 , x 2 ,..., x N ); wherein, N is the length value of the signal X; x 1 is the signal amplitude collected for the first time, x 2 is the signal amplitude collected for the second time, x N is the signal amplitude collected for the Nth time; the set threshold is 0.5V; Step (3), calculate the root mean square value RMS of this section of the signal, and the calculation formula is as follows: ; wherein, x k is the signal amplitude collected for the kth time; Step (4), calculate the peak value PE of this section of the signal, and the calculation formula is as follows: ; Step (5), calculate the waveform index FI of this section of the signal, and the calculation formula is as follows:

[0008] Step (6), calculate the damage factor DF of this section of the signal, and the calculation formula is as follows:

[0009] Step (7), evaluate the wood damage level according to the damage factor: When it is slight damage; when it is moderate damage; when it is severe damage; when it is extremely severe damage.

[0010] Furthermore, in step (1), an acoustic emission sensor is installed every 80 cm in the length direction of the wood to be detected.

[0011] Furthermore, in step (1), a UTM5105 type electronic universal testing machine is used for the test. An acoustic emission sensor is installed in the length direction of the wood to be detected, and the acoustic emission sensor is 80 mm away from the indenter of the testing machine.

[0012] Furthermore, it also includes the following steps: record the waveform of the effective acoustic emission signal as X, and generate a detection report; the detection report also includes the generation time of the effective acoustic emission signal, as well as the corresponding root mean square value, peak value, waveform index, and calculated value of the damage factor.

[0013] Furthermore, for the 4 damage levels, they are respectively recorded as slight, moderate, severe, and extremely severe in the damage level column of the detection report; for the slight and moderate levels, they are only recorded in the report, and for the severe and extremely severe levels, in addition to being recorded in the report, the loss factor is also marked on the corresponding waveform.

[0014] The wood non-destructive testing system based on the acoustic emission damage factor adopts the above-mentioned wood non-destructive testing method based on the acoustic emission damage factor, and includes: an acoustic emission sensor, a preamplifier, a high-speed data acquisition card, a computer, and a signal acquisition trigger switch; The described acoustic emission sensor 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; The input end of the preamplifier is connected to the output end of the acoustic emission sensor, and is used to amplify the original acoustic emission signal of the wood to be detected collected; The output end of the preamplifier is connected to the input end of the high-speed data acquisition card through the 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 closes; The high-speed data acquisition card transmits the acquired original acoustic emission signals to the Lab VIEW data processing platform of the computer, and then performs detection according to steps (2) to (7).

[0015] Furthermore, the preamplifier is a 40 dB preamplifier.

[0016] Furthermore, the high-speed data acquisition card is an 8-channel high-speed data acquisition card, the signal acquisition frequency is set to 500 kHz, and the maximum amplitude of the acquired signal is 10 V.

[0017] Based on three waveform features of the acoustic emission signals during the wood damage process, namely the root mean square value, peak value, and waveform index, the present invention proposes a calculation method for the damage factor, and classifies the wood damage into four levels: slight, moderate, severe, and extremely severe according to the damage factor.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a non-destructive testing method and system for wood based on the acoustic emission damage factor. In terms of signal acquisition, the traditional method is to continuously acquire and store the acoustic emission signals. The present invention does not adopt the continuous acquisition method, but only acquires and stores the acoustic emission signals after reaching a certain threshold, saving the storage space of the acquisition system; in terms of operation, the damage factor can be obtained by directly performing simple operations on the originally acquired acoustic emission signals, effectively simplifying the structure of the wood acoustic emission signal acquisition system; in terms of detection, the dynamic non-destructive testing of wood is directly realized based on the damage factor of the original acoustic emission signals, and then a dynamic damage level evaluation report is given, providing a diagnostic basis for the safe and healthy use of wood.

[0019] Patent CN108267510A proposes a wood structure acoustic emission monitoring system, and patent CN118465085A proposes a damage type discrimination method based on the time-frequency domain characteristics of acoustic emission signals, but neither of these two patents involves the grading evaluation of the wood damage degree. Patent CN117783294A proposes an evaluation method based on the energy entropy of acoustic emission signals, classifying the wood damage into three levels: slight, moderate, and severe, and it is necessary to perform complex wavelet packet decomposition on the signals and then calculate the energy entropy. The present invention does not require signal preprocessing, directly calculates the damage factor using the root mean square value, peak value, and waveform index of the original signal, and classifies the wood damage into four levels: slight, moderate, severe, and extremely severe. Description of the Drawings

[0020] Figure 1 is a flowchart of the non-destructive testing method for wood based on the acoustic emission damage factor;

[0021] Figure 2 is a schematic structural diagram of the non-destructive testing system for wood based on the acoustic emission damage factor;

[0022] Figure 3 Waveform of X and corresponding annotation diagram for Application Example 1;

[0023] Figure 4 Waveform of X and corresponding annotation diagram for Application Example 2; among them, (a) is the waveform of X collected by Channel 1 and the corresponding annotation diagram; (b) is the waveform of X collected by Channel 2 and the corresponding annotation diagram. Detailed implementation manner

[0024] The present invention will be further described in detail below in conjunction with the embodiments.

[0025] Those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. For those not specified in the embodiments, the techniques or conditions described in the literature in the art or according to the product specifications are followed. Those materials or equipment not specified by the manufacturer can be obtained as conventional products through purchase.

[0026] Embodiment 1 As Figure 1 shown, a non-destructive testing method for wood based on acoustic emission damage factor includes the following steps: Step (1), install at least one acoustic emission sensor in the length direction of the wood to be detected; Step (2), obtain 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 regarded that no damage occurs and the signal is not collected; when the signal amplitude reaches or exceeds the set threshold, the signal is collected, and when the signal amplitude is continuously lower than 10% of the set threshold for 20 times, the signal collection is stopped; this section of the collected signal is regarded as a section of effective acoustic emission signal and is denoted as X, X = (x 1 , x 2 ,..., x N ); wherein, N is the length value of the signal X; x 1 is the signal amplitude collected for the first time, x 2 is the signal amplitude collected for the second time, x N is the signal amplitude collected for the Nth time; the set threshold is 0.5V; Step (3), calculate the root mean square value RMS of this section of the signal, and the calculation formula is as follows: ; wherein, x k is the signal amplitude collected for the kth time; Step (4), calculate the peak value PE of this section of the signal, and the calculation formula is as follows: ; Step (5), calculate the waveform index FI of this segment of the signal, and the calculation formula is as follows:

[0027] Step (6), calculate the damage factor DF of this segment of the signal, and the calculation formula is as follows:

[0028] Step (7), evaluate the wood damage level according to the damage factor: When , it is slight damage; when , it is moderate damage; when , it is severe damage; when , it is extremely severe damage.

[0029] Embodiment 2 As Figure 1 shown, a non-destructive testing method for wood based on the acoustic emission damage factor includes the following steps: Step (1), install at least one acoustic emission sensor in the length direction of the wood to be detected; Step (2), obtain 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 regarded as no damage occurring and the signal is not collected; when the signal amplitude reaches or exceeds the set threshold, the signal collection starts, and when the signal amplitude is continuously lower than 10% of the set threshold for 20 times, the signal collection stops; this segment of the collected signal is regarded as a segment of effective acoustic emission signal and is denoted as X, X = (x 1 , x 2 ,..., x N ); wherein, N is the length value of the signal X; x 1 is the signal amplitude collected for the first time, x 2 is the signal amplitude collected for the second time, x N is the signal amplitude collected for the Nth time; the set threshold is 0.5V; Step (3), calculate the root mean square value RMS of this segment of the signal, and the calculation formula is as follows: ; wherein, x k is the signal amplitude collected for the kth time; Step (4), calculate the peak value PE of this segment of the signal, and the calculation formula is as follows: ; Step (5), calculate the waveform index FI of this segment of the signal, and the calculation formula is as follows:

[0030] Step (6), calculate the damage factor DF of this section of the signal, and the calculation formula is as follows:

[0031] Step (7), evaluate the wood damage level according to the damage factor: When , it is slight damage; when , it is moderate damage; when , it is severe damage; when , it is extremely severe damage.

[0032] In step (1), an acoustic emission sensor is installed every 80 cm in the length direction of the wood to be detected.

[0033] In step (1), a UTM5105 type electronic universal mechanical testing machine is used for the test. An acoustic emission sensor is installed in the length direction of the wood to be detected, and the acoustic emission sensor is 80 mm away from the indenter of the mechanical testing machine.

[0034] It further includes the following steps: record the waveform of the effective acoustic emission signal as X, and generate a test report; the test report also includes the generation time of the effective acoustic emission signal, as well as the corresponding root mean square value, peak value, waveform index, and calculated value of the damage factor.

[0035] Example 3 As Figure 1 shown, a non-destructive testing method for wood based on the acoustic emission damage factor includes the following steps: Step (1), install at least one acoustic emission sensor in the length direction of the wood to be detected; Step (2), obtain 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 considered that no damage occurs and the signal is not collected; when the signal amplitude reaches or exceeds the set threshold, start collecting the signal, and stop collecting the signal when the signal amplitude is continuously 20 times lower than 10% of the set threshold; regard this section of the collected signal as a section of effective acoustic emission signal, and record it as X, X=(x 1 ,x 2 ,...,x N ); wherein, N is the length value of the signal X; x 1 is the signal amplitude collected for the first time, x 2 is the signal amplitude collected for the second time, x N is the signal amplitude collected for the Nth time; the set threshold is 0.5 V; Step (3), calculate the root mean square value RMS of this section of the signal, and the calculation formula is as follows: ; wherein, x kis the amplitude of the signal collected for the k-th time; Step (4), calculate the peak value PE of this segment of the signal, and the calculation formula is as follows: ; Step (5), calculate the waveform index FI of this segment of the signal, and the calculation formula is as follows:

[0036] Step (6), calculate the damage factor DF of this segment of the signal, and the calculation formula is as follows:

[0037] Step (7), evaluate the wood damage level according to the damage factor: when it is minor damage; when it is moderate damage; when it is severe damage; when it is extremely severe damage.

[0038] In step (1), an acoustic emission sensor is installed every 80 cm in the length direction of the wood to be detected.

[0039] In step (1), a UTM5105 type electronic universal mechanical testing machine is used for the test. An acoustic emission sensor is installed in the length direction of the wood to be detected, and the acoustic emission sensor is 80 mm away from the indenter of the mechanical testing machine.

[0040] It further includes the following steps: record the waveform of the effective acoustic emission signal as X and generate a detection report; the detection report also includes the generation time of the effective acoustic emission signal, as well as the calculated values of the corresponding root mean square value, peak value, waveform index, and damage factor.

[0041] For the 4 damage levels, they are respectively recorded as minor, moderate, severe, and extremely severe in the damage level column of the detection report; for the minor and moderate levels, they are only recorded in the report, and for the severe and extremely severe levels, in addition to being recorded in the report, the loss factor is also marked on the corresponding waveform.

[0042] Example 4 As Figure 2 shown, the non-destructive testing system for wood based on the acoustic emission damage factor adopts the non-destructive testing method for wood based on the acoustic emission damage factor described in Example 1, Example 2 or Example 3, and includes: 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; The described 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; 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 original acoustic emission signal of the wood to be detected collected; 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 acquire the original acoustic emission signal amplified by the preamplifier 2; When the amplitude of the original acoustic emission signal reaches or exceeds the set threshold, the signal acquisition trigger switch 5 closes; The high-speed data acquisition card 3 transmits the original acoustic emission signal it acquires to the Lab VIEW data processing platform of the computer 4, and then performs detection according to steps (2) to (7).

[0043] Embodiment 5 As Figure 2 shown, the non-destructive testing system for wood based on the acoustic emission damage factor adopts the non-destructive testing method for wood based on the acoustic emission damage factor described in Embodiment 1, Embodiment 2 or Embodiment 3, and includes: 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; The described acoustic emission sensor 1 is installed in the length direction of the wood to be detected, and is used to acquire the original acoustic emission signal of the wood to be detected; 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 original acoustic emission signal of the wood to be detected collected; 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 acquire the original acoustic emission signal amplified by the preamplifier 2; When the amplitude of the original acoustic emission signal reaches or exceeds the set threshold, the signal acquisition trigger switch 5 closes; The high-speed data acquisition card 3 transmits the original acoustic emission signal it acquires to the Lab VIEW data processing platform of the computer 4, and then performs detection according to steps (2) to (7).

[0044] The preamplifier 3 is a 40dB preamplifier.

[0045] The described high-speed data acquisition card 3 is an 8-channel high-speed data acquisition card, the signal acquisition frequency is set to 500kHz, and the maximum amplitude of the acquired signal is 10V.

[0046] Application Example 1

[0047] Use beech wood as the wood to be tested. The specifications of the wood to be tested are 300 mm × 20 mm × 20 mm (axial × tangential × radial). A three-point bending test is carried out using a UTM5105 type electronic universal mechanical testing machine. The test parameters are set according to ASTM-D198-21a, and the loading speed is 2 mm / min.

[0048] A 1-channel data acquisition system built based on an NI USB-6366 acquisition card and LabVIEW software. The acoustic emission sensor used is an RS-2A single-ended resonant AE sensor with a resonant frequency of 150 kHz. The preamplifier uses a PAI preamplifier with a gain of 40 dB to amplify the signal received by the acoustic emission sensor. The maximum amplitude of the signal is 10 V, and the sampling frequency is set to 500 kHz.

[0049] Place the acoustic emission sensor vertically 80 mm away from the indenter of the mechanical testing machine. The indenter is located at the center of the specimen, and continuous pressure is applied at a constant speed of 2 mm / min.

[0050] To more precisely illustrate the superiority of the present invention, the time interval is refined. In this example, 20 s of signal data collected by the acoustic emission sensor is obtained in real time, and the dynamic damage level assessment using the detection method of the present invention is shown in Table 1.

[0051] Table 1

[0052] In this example, 12 effective acoustic emission signals are extracted from the 20-second three-point bending test of the wood (as Figure 3 ), and the damage levels are divided according to the damage factor. At the same time, the corresponding damage factor values are marked on the waveform diagram for the severe and very severe levels respectively, providing an intuitive criterion for the dynamic damage monitoring of the wooden structure. Compared with the prior art, the present invention has the following advantages: 1) Only collect effective acoustic emission signals, effectively reducing the signal storage space; 2) It is not necessary to perform any time-frequency domain analysis on the original collected signals, and the damage factor can be directly calculated to achieve the evaluation of the damage degree. 3) Mark the damage factor directly on the acoustic emission waveform diagram, which is more intuitive and effective.

[0053] Application Example 2 Use Pinus sylvestris var. mongolica as the wood to be tested, which is a wooden beam on a certain building. The specifications of the wood to be tested are 2500 mm × 40 mm × 60 mm (length × width × height), and acoustic emission non-destructive testing is carried out without damaging the wooden beam.

[0054] A 2-channel data acquisition system built based on the NI USB-6366 acquisition card and LabVIEW software. The acoustic emission sensor used is the RS-2A single-ended resonant AE sensor with a resonant frequency of 150 kHz. The preamplifier uses a PAI preamplifier with a gain of 40 dB to amplify the signal received by the acoustic emission sensor. The maximum amplitude of the signal is 10 V, and the sampling frequency is set to 500 kHz.

[0055] Place the acoustic emission sensor of Channel 1 at the middle position of the wooden beam, and place the acoustic emission sensor of Channel 2 at a distance of 80 cm from the acoustic emission sensor of Channel 1.

[0056] To more precisely illustrate the superiority of the present invention, the time interval is refined. In this example, 20 s of signal data collected by the acoustic emission sensor is obtained in real time, and the dynamic damage level assessment is carried out using the detection method of the present invention as shown in Table 2.

[0057] Table 2

[0058] A total of 5 effective acoustic emission signals were collected in Channel 1 (as shown in Figure 4 (a)), and a total of 7 acoustic emission signals were collected in Channel 2 (as shown in Figure 4 (b)). The 12 acoustic emission signals collected by the two channels are all at the minor damage level, indicating that the health condition of the wooden beam is good.

[0059] For Application Example 1, the evaluation results obtained by the method of invention patent CN117783294A are shown in Table 3.

[0060] Table 3

[0061] Compared with the present invention, the present invention detected 12 damage signals, while the invention patent CN117783294A only detected 5 damage signals; for the 5 detected damage signals, the damage levels of the first 4 damage signals correspond to the severe level of the present invention, and the last 1 damage signal corresponds to the serious level of the present invention; for the 6 minor-level damage signals detected by the present invention, the method of invention patent CN117783294A failed to detect them all. Therefore, whether it is the number of detected damages and the level classification, the present invention is superior to the existing patents.

[0062] Since all of Application Example 2 are minor damages, no further comparative analysis will be carried out.

[0063] For Application Example 1, the evaluation results obtained by the method of the invention patent (application number: 202510101383X) are shown in Table 4.

[0064] Table 4

[0065] Compared with the present invention, 12 damage signals are detected by the present invention, while 10 damage signals are detected by the invention patent (application number: 202510101383X). Among them, the evaluations of 5 damage signals are consistent. The damage levels of the 2nd - 5th damage signals are lower than the first level of this project; the 6th damage signal is located at a minor damage level, while the invention patent locates it at a severe damage level. From Figure 3 it can be seen that obvious damage signals occur at this time, but due to the short duration, the calculated effective energy density is low, so it is misjudged as minor damage. Therefore, in terms of the accuracy of damage level classification, the present invention is superior to the existing patents.

[0066] Since all the application examples 2 are minor damages, no further comparative analysis will be conducted.

[0067] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above - mentioned embodiments. What is described in the above - mentioned embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for nondestructive testing of wood based on acoustic emission damage factor, 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 considered 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), calculate the root mean square value RMS of the signal segment, the calculation formula is as follows: ； Among them, x k is the signal amplitude collected for the kth time; Step (4), calculate the peak value PE of the signal segment, the calculation formula is as follows: ； Step (5), calculate the waveform index FI of the signal segment, the calculation formula is as follows: ； Step (6), calculate the damage factor DF of the signal segment, the calculation formula is as follows: ； Step (7), evaluate the wood damage level according to the damage factor: When When When When it is serious injury.

2. The method for nondestructive testing of wood based on acoustic emission damage factor according to claim 1, characterized in that: In step (1), an acoustic emission sensor is installed every 80 cm in the length direction of the wood to be tested.

3. The method for nondestructive testing of wood based on acoustic emission damage factor 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 nondestructive testing of wood based on acoustic emission damage factor according to claim 1, characterized in that: The method also includes the following steps: recording the waveform of the effective acoustic emission signal as X, and generating a test report; the test report also includes the generation time of the effective acoustic emission signal, and the corresponding root mean square value, peak value, waveform index, and calculated value of the damage factor.

5. The method for nondestructive testing of wood based on acoustic emission damage factor according to claim 1, characterized in that: For the four damage levels, they are recorded as mild, moderate, severe, and serious in the damage level column of the test report; mild and moderate levels are only recorded in the report, and severe and serious levels are not only recorded in the report, but the loss factors are also marked on the corresponding waveforms.

6. A wood nondestructive testing system based on acoustic emission damage factor, using the wood nondestructive testing method based on acoustic emission damage factor according to any one of 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 (7).

7. The wood nondestructive testing system based on acoustic emission damage factor according to claim 6 is characterized in that: The preamplifier is a 40dB preamplifier.

8. The wood nondestructive testing system based on acoustic emission damage factor according to claim 6 is characterized in that: The high-speed data acquisition card is an 8-channel high-speed data acquisition card, the signal acquisition frequency is set to 500kHz, and the maximum amplitude of the acquisition signal is 10V.

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