CN113030275A - Wood structure water content measuring device and method based on wave velocity method - Google Patents

Wood structure water content measuring device and method based on wave velocity method Download PDF

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Publication number
CN113030275A
CN113030275A CN202110441387.4A CN202110441387A CN113030275A CN 113030275 A CN113030275 A CN 113030275A CN 202110441387 A CN202110441387 A CN 202110441387A CN 113030275 A CN113030275 A CN 113030275A
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wood structure
driver
sensor
signal
excitation signal
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陈琳
李修权
熊海贝
孔庆钊
桑笑晗
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Tongji University
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Tongji University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/07—Analysing solids by measuring propagation velocity or propagation time of acoustic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/24—Probes
    • G01N29/2437—Piezoelectric probes
    • G01N29/245—Ceramic probes, e.g. lead zirconate titanate [PZT] probes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/01—Indexing codes associated with the measuring variable
    • G01N2291/011—Velocity or travel time
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/023—Solids
    • G01N2291/0238—Wood
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/028—Material parameters
    • G01N2291/02845—Humidity, wetness

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  • Biochemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
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  • Ceramic Engineering (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)

Abstract

The invention discloses a device and a method for measuring the moisture content of a wood structure based on a wave velocity method, which are used for measuring the moisture content of the wood structure to be measured and comprise the following steps: the device comprises a sensor, a driver and a signal transmitting and receiving device; the sensor and the driver are connected with the wood structure to be detected in a point contact mode; the sensor and the driver are both connected with the signal transmitting and receiving device; PZT modules are arranged in the sensor and the driver; the driver is used for transmitting an excitation signal to the wood structure to be tested and generating a stress wave in the wood structure to be tested; the sensor is used for receiving the stress wave and sending the stress wave to the signal transmitting and receiving device as a sensing signal; the signal transmitting and receiving device is used for simultaneously acquiring an excitation signal transmitted by the driver and a sensing signal transmitted by the sensor and acquiring the moisture content of the wood structure to be detected based on the excitation signal and the sensing signal. The invention can realize rapid and convenient nondestructive detection, is suitable for various types of wood members, and has wide application prospect.

Description

Wood structure water content measuring device and method based on wave velocity method
Technical Field
The invention relates to the field of wood processing and wood structure buildings, in particular to a device and a method for measuring the water content of a wood structure based on a wave velocity method.
Background
The water content of the wood component is one of important parameters influencing the service performance and long-term service durability of the wood structure building. The mechanical properties, particularly the elastic modulus, of the wood member are significantly affected by the water content. In addition, in the long-term service process of the wood structure, the change of the water content can affect the creep property of the wood member, and termites and the like can be bred, so that holes and corrosion in the member are caused. Internal holes and corrosion weaken the cross section bearing capacity of the member, and bring about potential safety hazards to the structure.
At present, a drying method and a resistance method are mainly used for measuring the moisture content of a wood member in service. The drying method needs to sample the components, the moisture content is measured according to a standard method for measuring the moisture content, a constant temperature box, a vernier caliper and an electronic balance are used in the measuring process, and the moisture content is calculated according to the mass and volume changes of the wood component samples before and after drying. The method needs a long time, and the sample is generally placed in the constant temperature box for about 6 hours, so that the method is not suitable for quick detection of engineering application. The principle of resistance measurement is that the moisture content of wood and the resistance characteristic thereof present a certain relationship, and the moisture content of the wood component is obtained by substituting the resistance measured by the resistance meter into a relational expression of the moisture content and the resistance. The method is convenient to measure, but the range of the water content capable of being measured is limited, generally limited to about 5-30%, and the method is greatly influenced by wood tree species.
Therefore, it is particularly necessary to provide a device and a method for measuring the moisture content of a wood structure, which are rapid and convenient for nondestructive testing and have a wide application range.
Disclosure of Invention
The invention aims to provide a device and a method for measuring the water content of a wood structure based on a wave velocity method, which are used for solving the technical problems in the prior art, and the probe adopts point contact, can realize rapid and convenient nondestructive detection, is suitable for various types of wood members, and has wide application prospect.
In order to achieve the purpose, the invention provides the following scheme: the invention provides a wood structure water content measuring device based on a wave velocity method, which is used for measuring the water content of a wood structure to be measured and comprises the following components: the device comprises a sensor, a driver and a signal transmitting and receiving device; the sensor and the driver are connected with the wood structure to be detected in a point contact mode; the sensor and the driver are both connected with the signal transmitting and receiving device; PZT modules are arranged in the sensor and the driver;
the driver is used for transmitting an excitation signal to the wood structure to be tested, so that the excitation signal generates stress waves in the wood structure to be tested;
the sensor is used for receiving stress waves generated in the wood structure to be detected and sending the received stress waves to the signal transmitting and receiving device as sensing signals;
the signal transmitting and receiving device is used for simultaneously acquiring an excitation signal transmitted by the driver and a sensing signal transmitted by the sensor and acquiring the moisture content of the wood structure to be detected based on the excitation signal and the sensing signal.
Preferably, the excitation signal employs a sine window function.
Preferably, the sensor and the driver both comprise a first protective body, a second protective body and a probe which are sequentially connected, the probe is in point contact connection with the wood structure to be tested, and the PZT module is arranged in the second protective body.
Preferably, the first protection body and the second protection body are cylindrical structures, the inner diameter of the first protection body is the same as the outer diameter of the second protection body, the first protection body is a sleeve with a thread on the inner wall, the second protection body is a sleeve with a thread on the outer wall, and the first protection body is connected with the second protection body through a thread; the probe is of a conical structure, and the vertex of the conical structure is in point contact connection with the wood structure to be detected.
Preferably, the PZT module comprises a PZT sheet, a magnet connecting layer is arranged at the bottom of the PZT sheet, and an amplifying and modulating circuit is fixedly connected to the surface of the PZT sheet; the PZT sheet is also connected with a lead, and the lead is respectively connected with the anode and the cathode of the PZT sheet; the second protective body is provided with a wire hole, and a wire passes through the wire hole and is connected with the signal transmitting and receiving device; the PZT module is connected to the second protective body through the magnet connection layer.
Preferably, an epoxy resin protector is arranged on the periphery of the PZT sheet.
The invention also provides a method for measuring the water content of the wood structure based on the wave velocity method, which comprises the following steps:
the sensor and the driver are respectively connected with the signal transmitting and receiving device through leads, and are connected with the wood structure to be tested in a point contact mode;
transmitting an excitation signal to the wood structure to be detected through the driver, receiving a stress wave generated by the excitation signal in the wood structure to be detected through the sensor, and sending the stress wave serving as a sensing signal to the signal transmitting and receiving device;
performing cross-correlation calculation on the excitation signals and the sensing signals through the signal transmitting and receiving device to obtain time delay between the excitation signals and the sensing signals, and calculating the wave velocity transmitted by the stress waves in the wood structure to be measured based on the time delay and the distance between the driver and the sensor;
and acquiring a calibration curve of the wave velocity and the water content of the wood structure, and obtaining the water content of the wood structure to be detected based on the calibration curve and the wave velocity of the stress wave transmitted in the wood structure to be detected.
Preferably, the excitation signal emitted by the driver to the wood structure to be measured is a sine window function; and the frequency of the sine window function is the natural vibration frequency of a PZT module in the driver.
Preferably, the excitation signal generates a stress wave in the wood structure to be measured through an inverse piezoelectric effect of the PZT module inside the driver, and the stress wave is collected by the signal transmitting and receiving device through the inverse piezoelectric effect of the PZT module inside the sensor after passing through the cross section of the wood structure to be measured.
Preferably, the time delay between the excitation signal and the sensing signal is calculated by a cross-correlation function, which is expressed by the following equation:
Figure BDA0003035180330000041
wherein, x (m) is an excitation signal, y (m + N) is a sensing signal, and N is the number of discrete data points of the sensing signal; r (n) is a correlation coefficient vector, the maximum value of which is denoted as max (r), and the time delay Δ t between the excitation signal and the sensing signal is expressed as follows:
Figure BDA0003035180330000042
where Index is the Index position of max (R), fsIs the sampling frequency of the excitation signal.
The invention discloses the following technical effects:
(1) according to the invention, PZT modules are arranged in the sensor and the driver, an excitation signal generates a stress wave in the wood structure to be detected through the inverse piezoelectric effect of the PZT module in the driver, the stress wave passes through the cross section of the wood structure to be detected and is collected by the signal transmitting and receiving device through the positive piezoelectric effect of the PZT module in the sensor, the propagation wave velocity of the stress wave in the wood structure to be detected is obtained through the time delay of the excitation signal and the sensing signal, and the moisture content of the wood structure to be detected is obtained through the calibration curve of the wave velocity and the moisture content of the wood structure, so that the rapid, convenient and nondestructive detection is realized, and the sensor can be suitable for various types of wood structures and has wide application prospect;
(2) the PZT module is provided with the magnet connecting layer and is connected with the second protective body through magnetic force, so that the PZT module has the advantages of easy installation and disassembly;
(3) the sensor and the driver of the invention are in conical structures, are in point contact connection with the wood structure to be detected, and have the advantages of simple operation and nondestructive detection.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a schematic structural diagram of a device for measuring the moisture content of a wood structure based on a wave velocity method;
FIG. 2 is a schematic diagram of a driver/sensor configuration according to the present invention;
FIG. 3 is a schematic diagram of a PZT module according to the present invention;
FIG. 4 is a flow chart of a method for measuring the moisture content of a wood structure based on a wave velocity method;
FIG. 5 is a schematic diagram of excitation signals and sensing signals in an embodiment of the present invention;
FIG. 6 is a schematic diagram of a calibration curve of the wave velocity and the moisture content of the wood structure in the embodiment of the invention;
in the figure, 1 is an epoxy resin protector, 2 is a PZT sheet, 3 is a magnet connection layer, 4 is an amplification modulation circuit, 5 is a lead, 11 is a first protector, 12 is a second protector, 13 is a lead hole, 14 is a probe, 21 is a sensor, 22 is a signal transmitting and receiving device, 23 is a wood structure to be measured, and 24 is a driver.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Referring to fig. 1 to 3, the present embodiment provides a wood structure moisture content measuring device based on a wave velocity method, which is used for measuring the moisture content of a wood structure 23 to be measured, and specifically includes: a sensor 21, a driver 24, a signal transmitting and receiving device 22; the sensor 21 and the driver 24 are connected with the wood structure 23 to be detected in a point contact manner; the sensor 21 and the driver 24 are both electrically connected to the signal transmitting and receiving device 22.
A PZT (Piezoelectric Transducer 21) module is disposed inside each of the sensor 21 and the driver 24.
The driver 24 is configured to transmit an excitation signal to the wood structure 23 to be tested, so that the excitation signal generates a stress wave in the wood structure 23 to be tested; wherein the excitation signal adopts a sine window function.
The sensor 21 is configured to receive a stress wave generated in the wood structure 23 to be measured, and send the received stress wave to the signal transmitting and receiving device 22 as a sensing signal;
the signal transmitting and receiving device 22 is configured to simultaneously acquire an excitation signal transmitted by the driver 24 and a sensing signal transmitted by the sensor 21, perform cross-correlation calculation on the two time-series discrete signals of the excitation signal and the sensing signal to obtain a time delay Δ t, measure a distance L between the driver 24 and the sensor 21, calculate a wave velocity v of the stress wave transmitted in the wood structure 23 to be measured according to a formula L/. DELTA.t, and calculate the water content of the wood structure 23 to be measured according to a calibration curve of the wave velocity v and the water content of the wood structure.
The sensor 21 and the driver 24 respectively comprise a first protective body 11, a second protective body 12 and a probe 14 which are connected in sequence; the first protective body 11 and the second protective body 12 are cylindrical structures, the inner diameter of the first protective body 11 is the same as the outer diameter of the second protective body 12, the first protective body 11 is a thin-walled sleeve with threads arranged inside, the second protective body 12 is a thin-walled sleeve with threads arranged outside, and the first protective body 11 is connected with the second protective body 12 through the threads; the probe 14 is in a conical structure, the vertex of the conical structure is in point contact connection with the wood structure 23 to be detected, the operation is simple, and the nondestructive detection of the wood structure 23 to be detected can be realized; the PZT module is disposed in the second protective body 12, and the inner diameter of the second protective body 12 is the same as the inner diameter of the PZT module; the first protector 11 is equivalent to the cover of the second protector 12, and the first protector and the second protector are connected by threads, so that the internal PZT module can be conveniently detached and replaced.
The PZT module comprises a PZT sheet 2, the PZT sheet 2 is a main sensing element, an epoxy resin protector 1 is arranged on the periphery of the PZT sheet 2, and the sensing material can be protected from being influenced and damaged by the environment through the epoxy resin protector 1, so that the service lives of the sensor and the driver are prolonged; the bottom of the PZT sheet 2 is provided with a magnet connecting layer 3, the surface of the PZT sheet 2 is fixedly connected with an amplifying and modulating circuit 4, and the amplifying and modulating circuit 4 is welded on the surface of the PZT sheet 2; the PZT sheet 2 is also connected with a lead 5, and the lead 5 is respectively connected with the anode and the cathode of the PZT sheet 2; the second protective body 12 is provided with a wire hole 13, and the wire 5 passes through the wire hole 13 and is connected with the signal transmitting and receiving device 22; the PZT module is connected with the second protective body 12 through the magnet connecting layer 3, and has the advantages of easy installation and detachability through a magnetic force connection mode.
Referring to fig. 4, the invention further provides a method for measuring the moisture content of the wood structure based on the wave velocity method, which specifically comprises the following steps:
s1, connecting the sensor 21 and the driver 24 with the signal transmitting and receiving device 22 through a lead 5 respectively, and connecting the sensor 21 and the driver 24 with the wood structure 23 to be tested in a point contact manner;
s2, transmitting an excitation signal to the wood structure 23 to be measured through the driver 24, receiving a stress wave generated in the wood structure 23 to be measured by the excitation signal through the sensor 21, and sending the stress wave as a sensing signal to the signal transmitting and receiving device 22;
wherein, the excitation signal transmitted by the driver 24 to the wood structure 23 to be measured is a sine window function, and the sine window function is in matlabIn the generation, a sine window function is generated by setting the period, the frequency and the number of sampling points in matlab; the frequency of the sine window function is the natural vibration frequency of the PZT sheet 2, the sine window function is a column of amplitude data generated in matlab, and the amplitude data is stored as a text file type. Selecting the excitation signal type as 'self-defined waveform' on the control panel of the signal transmitting and receiving device 22, introducing a modulated sine window function file, and performing transmission time interval, amplitude increasing coefficient and sampling frequency f on the signal transmitting and receiving device 22sAnd sends a sine window function wave excitation signal to the wood structure 23 to be measured through the driver 24.
The excitation signal generates a stress wave in the wood structure 23 to be measured through the inverse piezoelectric effect of the PZT module inside the driver 24, and after the stress wave passes through the cross section of the wood structure 23 to be measured, the stress wave is collected by the signal transmitting and receiving device 22 through the positive piezoelectric effect of the PZT module inside the sensor 21, as shown in fig. 5, T is an excitation signal, and R1 is a sensing signal.
S3, performing cross-correlation calculation on the excitation signal and the sensing signal through the signal transmitting and receiving device 22 to obtain a time delay between the excitation signal and the sensing signal, and calculating a wave velocity of the stress wave transmitted in the wood structure 23 to be measured based on the time delay and a distance between the driver 24 and the sensor 21;
due to the existence of the time delay between the excitation signal and the sensing signal, the time delay Δ t between the two time-series discrete signals of the excitation signal and the sensing signal is calculated through a cross-correlation function, the distance L between the driver 24 and the sensor 21 is measured at the same time, and the wave velocity v of the stress wave transmitted in the wood structure 23 to be measured is calculated based on the time delay Δ t and the distance L between the driver 24 and the sensor 21, as shown in the following formula:
Figure BDA0003035180330000101
wherein the cross-correlation function is represented by:
Figure BDA0003035180330000102
wherein, x (m) is an excitation signal, y (m + N) is a sensing signal, and N is the number of discrete data points of the sensing signal; r (n) is a correlation coefficient vector, the maximum value of the vector is denoted as max (r), and the time delay Δ t between the excitation signal and the sensing signal is calculated according to the following formula:
Figure BDA0003035180330000103
where Index is max (R) Index position in time series, N is the number of discrete data points of the sensing signal, fsIs the sampling frequency of the excitation signal, fsProvided in the control panel of the signal transmitting and receiving device 22.
S4, obtaining a calibration curve of the wave velocity and the water content of the wood structure, and obtaining the water content of the wood structure 23 to be detected based on the calibration curve and the wave velocity of the stress wave transmitted in the wood structure 23 to be detected. The method for acquiring the calibration curve of the wave velocity and the water content of the wood structure comprises the following steps:
selecting wood structures of different types and different water contents, calibrating the water contents, and measuring the wave velocity to obtain a calibration curve of the wave velocity and the water contents of the wood structures, as shown in FIG. 6; through the calibration curve of moisture content, can carry out quick, convenient, nondestructive test through the wave speed to the moisture content of timber structure 23 that awaits measuring, and be applicable to various types of timber structure.
The invention has the following technical effects:
(1) according to the invention, PZT modules are arranged in the sensor and the driver, an excitation signal generates a stress wave in the wood structure to be detected through the inverse piezoelectric effect of the PZT module in the driver, the stress wave passes through the cross section of the wood structure to be detected and is collected by the signal transmitting and receiving device through the positive piezoelectric effect of the PZT module in the sensor, the propagation wave velocity of the stress wave in the wood structure to be detected is obtained through the time delay of the excitation signal and the sensing signal, and the moisture content of the wood structure to be detected is obtained through the calibration curve of the wave velocity and the moisture content of the wood structure, so that the rapid, convenient and nondestructive detection is realized, and the sensor can be suitable for various types of wood structures and has wide application prospect;
(2) the PZT module is provided with the magnet connecting layer and is connected with the second protective body through magnetic force, so that the PZT module has the advantages of easy installation and disassembly;
(3) the sensor and the driver of the invention are in conical structures, are in point contact connection with the wood structure to be detected, and have the advantages of simple operation and nondestructive detection.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.

Claims (10)

1. The utility model provides a timber structure moisture content measuring device based on wave velocity method for carry out the moisture content to timber structure (23) that awaits measuring and measure, its characterized in that includes: a sensor (21), a driver (24), a signal transmitting and receiving device (22); the sensor (21) and the driver (24) are connected with the wood structure (23) to be detected in a point contact mode; the sensor (21) and the driver (24) are both connected with the signal transmitting and receiving device (22); PZT modules are arranged in the sensor (21) and the driver (24);
the driver (24) is used for transmitting an excitation signal to the wood structure (23) to be tested, so that the excitation signal generates a stress wave in the wood structure (23) to be tested;
the sensor (21) is used for receiving stress waves generated in the wood structure (23) to be detected and sending the received stress waves serving as sensing signals to the signal transmitting and receiving device (22);
the signal transmitting and receiving device (22) is used for simultaneously acquiring an excitation signal transmitted by the driver (24) and a sensing signal transmitted by the sensor (21), and acquiring the water content of the wood structure (23) to be detected based on the excitation signal and the sensing signal.
2. The device for measuring the moisture content of the wood structure based on the wave velocity method according to claim 1, wherein the excitation signal adopts a sine window function.
3. The device for measuring the water content of the wood structure based on the wave velocity method is characterized in that the sensor (21) and the driver (24) respectively comprise a first protective body (11), a second protective body (12) and a probe (14) which are sequentially connected, the probe (14) is in point contact connection with the wood structure (23) to be measured, and the PZT module is arranged in the second protective body (12).
4. The wave velocity method-based wood structure water content measuring device according to claim 3, wherein the first protective body (11) and the second protective body (12) are cylindrical structures, the inner diameter of the first protective body (11) is the same as the outer diameter of the second protective body (12), the first protective body (11) is a sleeve with threads on the inner wall, the second protective body (12) is a sleeve with threads on the outer wall, and the first protective body (11) and the second protective body (12) are connected through threads; the probe (14) is of a conical structure, and the vertex of the conical structure is in point contact connection with the wood structure (23) to be detected.
5. The device for measuring the moisture content of the wood structure based on the wave velocity method is characterized in that the PZT module comprises a PZT sheet (2), a magnet connecting layer (3) is arranged at the bottom of the PZT sheet (2), and an amplification and modulation circuit (4) is fixedly connected to the surface of the PZT sheet (2); the PZT sheet (2) is also connected with a lead (5), and the lead (5) is respectively connected with the anode and the cathode of the PZT sheet (2); the second protective body (12) is provided with a wire hole (13), and the wire (5) penetrates through the wire hole (13) to be connected with the signal transmitting and receiving device (22); the PZT module is connected to the second protective body (12) via the magnet connection layer (3).
6. The device for measuring the water content of the wood structure based on the wave velocity method according to claim 5, wherein an epoxy resin protector (1) is arranged on the periphery of the PZT sheet (2).
7. The method for measuring the moisture content of the wood structure based on the wave velocity method according to any one of claims 1 to 6, comprising the steps of:
the sensor (21) and the driver (24) are respectively connected with the signal transmitting and receiving device (22) through a lead (5), and the sensor (21) and the driver (24) are connected with the wood structure (23) to be tested in a point contact mode;
an excitation signal is transmitted to the wood structure (23) to be tested through the driver (24), a stress wave generated in the wood structure (23) to be tested by the excitation signal is received through the sensor (21), and the stress wave is used as a sensing signal and is sent to the signal transmitting and receiving device (22);
performing cross-correlation calculation on the excitation signal and the sensing signal through the signal transmitting and receiving device (22) to obtain time delay between the excitation signal and the sensing signal, and calculating the wave velocity transmitted by the stress wave in the wood structure (23) to be measured based on the time delay and the distance between the driver (24) and the sensor (21);
and acquiring a calibration curve of the wave velocity and the water content of the wood structure, and acquiring the water content of the wood structure (23) to be detected based on the calibration curve and the wave velocity of the stress wave transmitted in the wood structure (23) to be detected.
8. The method for measuring the water content of the wood structure based on the wave velocity method according to claim 7, wherein the excitation signal transmitted by the driver (24) to the wood structure (23) to be measured is a sine window function; the frequency of the sine window function is the natural frequency of the PZT module in the driver (24).
9. The method for measuring the water content of the wood structure based on the wave velocity method according to claim 7, wherein the excitation signal generates a stress wave in the wood structure (23) to be measured through a reverse piezoelectric effect of a PZT module inside the driver (24), and the stress wave passes through the cross section of the wood structure (23) to be measured and is collected by the signal transmitting and receiving device (22) through a positive piezoelectric effect of the PZT module inside the sensor (21).
10. The method for measuring the moisture content of the wood structure based on the wave velocity method according to claim 7, wherein the time delay between the excitation signal and the sensing signal is calculated by a cross-correlation function, and the cross-correlation function is represented by the following formula:
Figure FDA0003035180320000041
wherein, x (m) is an excitation signal, y (m + N) is a sensing signal, and N is the number of discrete data points of the sensing signal; r (n) is a correlation coefficient vector, the maximum value of which is denoted as max (r), and the time delay Δ t between the excitation signal and the sensing signal is expressed as follows:
Figure FDA0003035180320000042
where Index is the Index position of max (R), fsIs the sampling frequency of the excitation signal.
CN202110441387.4A 2021-04-23 2021-04-23 Wood structure water content measuring device and method based on wave velocity method Pending CN113030275A (en)

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CN202110441387.4A CN113030275A (en) 2021-04-23 2021-04-23 Wood structure water content measuring device and method based on wave velocity method

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Application Number Priority Date Filing Date Title
CN202110441387.4A CN113030275A (en) 2021-04-23 2021-04-23 Wood structure water content measuring device and method based on wave velocity method

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