CN114675013A - Method and equipment for determining wood drying shrinkage/wet swelling behavior - Google Patents
Method and equipment for determining wood drying shrinkage/wet swelling behavior Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 57
- 239000002023 wood Substances 0.000 title claims abstract description 43
- 230000008961 swelling Effects 0.000 title claims abstract description 34
- 238000001035 drying Methods 0.000 title claims abstract description 25
- 239000010453 quartz Substances 0.000 claims abstract description 66
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 66
- 238000001179 sorption measurement Methods 0.000 claims abstract description 32
- 238000005259 measurement Methods 0.000 claims abstract description 11
- 238000009499 grossing Methods 0.000 claims abstract description 5
- 238000004140 cleaning Methods 0.000 claims abstract description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 40
- 238000003795 desorption Methods 0.000 claims description 14
- 238000010521 absorption reaction Methods 0.000 claims description 6
- 238000004364 calculation method Methods 0.000 claims description 6
- 239000000725 suspension Substances 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 5
- 239000012153 distilled water Substances 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 2
- 230000002708 enhancing effect Effects 0.000 claims description 2
- 238000003556 assay Methods 0.000 claims 2
- 238000012545 processing Methods 0.000 abstract description 8
- 238000012360 testing method Methods 0.000 description 13
- 238000002474 experimental method Methods 0.000 description 6
- 238000011065 in-situ storage Methods 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 4
- 238000000691 measurement method Methods 0.000 description 3
- 230000001360 synchronised effect Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000001413 cellular effect Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000010191 image analysis Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/46—Wood
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
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Abstract
The invention relates to a method and a device for measuring wood drying shrinkage/wet swelling behavior, wherein the measuring method comprises the following steps: s1: preparing a sample to be tested, smoothing the surface to be tested of the sample, S2: cleaning a quartz tray for placing a sample to be tested, placing a cushion block on the cleaned quartz tray, S3: put the sample that awaits measuring on the cushion, put into the sample storehouse with the quartz tray in, cover the lid, adjust the sample storehouse to constant temperature and relative humidity, until the sample that awaits measuring reaches the moisture content equilibrium state, S4: setting a video white light microscope combined with the dynamic moisture adsorption analyzer, keeping a fixed time interval, continuously photographing the to-be-measured surface of the to-be-measured sample, and S5: performing analysis processing on the image obtained at S4, S6: the image obtained in step S5 is introduced into image processing software for measurement. The invention solves the problem that the surface to be measured of the sample is directly attached to the bottom of the quartz tray, and can accurately obtain the corresponding dry shrinkage/wet expansion variable quantity of the sample to be measured under different relative humidity conditions in real time.
Description
Technical Field
The invention relates to the technical field of wood measurement, in particular to a method and equipment for determining wood drying shrinkage/wet swelling behavior.
Background
The phenomenon of wood drying and wet expansion has great influence on wood utilization, and the influence of drying and shrinkage on wood utilization mainly causes gaps, warping deformation and cracking caused by dimension shrinkage of wood products; swelling not only increases the size of the wood product, causing floor heave, door and window failure, but also reduces the mechanical properties (other than tensile strength) of most wood.
At present, a method for measuring the wood drying shrinkage/wet swelling behavior by using a dynamic moisture adsorption analyzer in combination with a video white light microscope is as follows: the method comprises the steps of placing a to-be-measured surface of a sample on a quartz tray with a transparent bottom after smoothing treatment by a slicer, shooting the bottom of the quartz tray by using a video white light microscope arranged right below the quartz tray, recording a digital image of the to-be-measured surface of the sample in a moisture desorption/adsorption process, and processing the digital image by using software to obtain the dry shrinkage/wet expansion variation of the to-be-measured surface of the sample.
The common practice for measuring the change in the shrinkage/swelling dimension on a cellular scale is: humidifying the control group sample in an environmental chamber, and determining the time required for the water content to reach equilibrium under the conditions of different relative humidity; then placing the sample to be tested into an environment chamber of an environment scanning electron microscope or a confocal laser scanning microscope, and humidifying according to the moisture content balance time obtained in the control test group; and finally, shooting the wood samples under different equilibrium moisture content levels, and obtaining the dry shrinkage/wet expansion size variation through image analysis.
The two methods have the following disadvantages: the surface to be measured of the sample is directly attached to the bottom of the quartz tray, so that the gaseous water molecules are prevented from freely contacting the tangent plane, and certain influence is caused on the synchronism and accuracy of the acquired dry shrinkage/wet expansion variable quantity data; the wood is a non-homogeneous and anisotropic material, so that whether the moisture content of the wood sample reaches an equilibrium state cannot be accurately judged in the experimental process, and the estimation can be carried out only through time obtained by a comparison test; only the dry shrinkage/wet expansion variation of the sample in the moisture content equilibrium state can be measured, and the dry shrinkage/wet expansion variation of the sample in the moisture desorption/adsorption process cannot be obtained.
Disclosure of Invention
Technical problem to be solved
In order to solve the above problems of the prior art, the present invention provides a method for measuring the drying shrinkage/swelling behavior of wood, and further provides an apparatus for measuring the drying shrinkage/swelling behavior of wood used in the above measuring method.
(II) technical scheme
In order to achieve the purpose, the invention adopts the main technical scheme that:
a wood drying shrinkage/swelling behavior determination method comprises the following steps:
s1: preparing a wood sample to be tested, and smoothing the surface to be tested of the sample by a slicer;
s2: cleaning a quartz tray for placing a sample to be tested by using distilled water, and placing a cushion block in the middle of the cleaned quartz tray;
s3: placing the sample to be tested obtained in the step S1 on the cushion block, then placing the quartz tray into the sample bin, covering the cover body, and adjusting the temperature and the relative humidity of the sample bin to be constant until the water content of the sample to be tested reaches a water content equilibrium state;
s4: setting a video white light microscope combined with a dynamic moisture adsorption analyzer, keeping a fixed time interval, and continuously photographing the surface to be measured of the sample to be measured;
s5: analyzing the image obtained in the step S4;
s6: and (4) introducing the image obtained in the step (S5) into image processing software for measurement, obtaining the size change of the sample to be measured in the moisture desorption/adsorption process, and finally obtaining the dry shrinkage/wet expansion change of the sample to be measured.
According to the method for determining the wood dry shrinkage/wet expansion behavior, a dynamic moisture adsorption analyzer is matched with a video white light microscope for use, photographing is carried out at fixed time intervals, the obtained image is processed through image processing software, and dry shrinkage/wet expansion size variable quantity data under different equilibrium water contents can be obtained in situ and in real time in cell scale;
in the above-described measuring method, preferably, in step S3, the temperature in the sample chamber is 5 to 50 ℃ and the relative humidity is 0 to 98%.
The temperature and the relative humidity in the sample bin are both adjustable, different temperatures and different humidities can be adjusted as required to test the shrinkage/swelling size variation of the sample to be tested under different conditions during an experiment, the testable relative humidity range of the tester is 0-98%, the highest testable relative humidity of a common tester can be 90%, and the method can more comprehensively obtain the shrinkage/swelling variation data of the sample to be tested under different relative humidity conditions.
In the above-mentioned measuring method, preferably, in step S4, the pixels of the image taken by the video white light microscope are 1280 × 960, and the interval time between the taking of the video white light microscope can be adjusted according to the needs of the experimenter, and is 20S, 1min or 2min respectively.
The shooting interval of the video white light microscope can be adjusted, and experimenters can adjust according to experiment requirements.
In the above-described measurement method, preferably, the analyzing the image obtained in S4 in step S5 includes: and adjusting the brightness, contrast, exposure, tone curve and color level of the picture, and enhancing the details of the measurement area.
In the above-described measurement method, preferably, step S6 includes:
s61: importing the processed picture into image processing software, firstly opening the image processing software, selecting 'file-open', importing the picture, selecting 'analysis-set proportion' to convert and calibrate a scale;
s62: selecting 'image-type-8 bit' to modify the format of the picture to change the picture into a gray-scale picture, and selecting 'image-adjustment-threshold' to process the picture by using a threshold method;
s63: the area of the catheter cavity to be measured is selected by using a magic stick tool in the image processing software, and the area of the selected catheter cavity can be measured and recorded by selecting analysis-measurement.
In the above measurement method, preferably, the wood swelling dimension change amount calculation formula:
△Ssw＝Ssw-S0 (1)
in the formula:
△Sswthe change of the swelling size of the tested catheter cavity in any relative humidity environment during the moisture absorption process is measured in the unit of mum2；
SswIs the area size of the tested catheter cavity when the water content reaches the equilibrium water content in any relative humidity environment in the water absorption process, and the unit is mum2；
S0Is the area size of the tested catheter cavity in an absolute dry state and has the unit of mum2；
The wood drying shrinkage size variation calculation formula is as follows:
△Ssh＝Ssh-S0 (2)
in the formula:
△Sshthe change quantity of the drying shrinkage size of the tested catheter cavity in any relative humidity environment in the moisture desorption process is expressed in the unit of mum2；
SshThe area size of the measured catheter cavity when the water content reaches the equilibrium water content in any relative humidity environment in the water desorption process is expressed in the unit of mu m2；
S0Is the area size of the tested catheter cavity in an absolute dry state and has the unit of mum2。
The present invention also provides a wood drying shrinkage/swelling behavior measuring apparatus used for the above measuring method, comprising:
a dynamic moisture adsorption analyzer, a video white light microscope;
the dynamic moisture adsorption analyzer comprises a sample bin and a gas flow controller;
the sample bin is positioned at the upper part of the gas flow controller, and the top of the sample bin is provided with a cover body;
the video white light microscope is positioned at the lower part of the dynamic moisture adsorption analyzer and is electrically connected with the dynamic moisture adsorption analyzer;
the quartz tray and the cushion block are also included;
the quartz tray is a bearing platform of a sample to be tested, the bottom of the quartz tray is transparent, two support rods are symmetrically and fixedly arranged on the outer edge of the quartz tray, the two support rods extend towards the upper part and intersect at one point to form a support, and a horizontal cross rod is fixedly arranged between the two support rods;
the cushion block is made of rubber materials and is placed on the upper portion of the quartz tray.
The cushion block is additionally arranged on the quartz tray, so that the cushion block can support the sample to be tested, and the surface to be tested of the sample to be tested can be freely and fully contacted with the gaseous water molecules in the sample bin at the first time.
Preferably, the inner diameter of the quartz tray is 17mm, the outer diameter of the quartz tray is 19mm, and the top of the quartz tray support is connected with a suspension wire for lifting the quartz tray in the sample bin.
The quartz tray is used for bearing a sample to be tested and a cushion block, and is convenient to put in and take out during experiment by arranging the suspension wires.
Preferably, the cushion block is a rubber ring, the inner diameter of the rubber ring is 5.8-6.2mm, the outer diameter of the rubber ring is 6.8-7.2mm, the height of the rubber ring is 0.9-1.2 mm, and the rubber ring is provided with an opening.
The size of the cushion block can meet the requirement that the mass of the cushion block is between 28 and 34mg, the function of supporting the surface to be tested of the sample to be tested without being in direct contact with the quartz tray is achieved, and meanwhile, the phenomenon that the bottom of the quartz tray is in contact with the lens of a video white light microscope below the quartz tray due to the fact that the quartz tray sinks due to the fact that the mass of the cushion block is too large is avoided, and test data cannot be obtained.
Preferably, the inner diameter of the rubber ring is 6mm, the outer diameter of the rubber ring is 7mm, the height of the rubber ring is 1mm, and the opening of the rubber ring occupies 1/6-1/4 of the outer circumference of the rubber ring.
(III) advantageous effects
The invention has the beneficial effects that:
according to the method for determining the wood drying shrinkage/swelling behavior, a dynamic moisture adsorption analyzer is combined with a video white light microscope to obtain a series of image sets of the to-be-measured surface of the wood sample under different relative humidity, and the drying shrinkage/swelling size variable quantity data under different equilibrium moisture content is obtained in situ and in real time by matching with an image processing technology.
The determination method of the invention has the following advantages: the problem that the surface to be measured of a sample is directly attached to the bottom of a quartz tray is solved, the surface to be measured of the sample is directly contacted with the relative humidity environment of a sample bin, the dry shrinkage/wet expansion behavior of the surface to be measured of the sample can synchronously respond to desorption/adsorption of water, the synchronous real-time measurement of the water content of the sample and the dry shrinkage/wet expansion size variation is realized, and dry shrinkage/wet expansion size variation data under different equilibrium water contents are obtained in situ and in real time by matching with an image processing technology. The moisture content can be monitored in real time, the accuracy is high, and the operation is convenient.
Drawings
FIG. 1 is a flow chart showing the steps of the measuring method of the present invention;
FIG. 2 is a schematic image processing of a wood sample according to the present invention;
FIG. 3 is a front view of the wood shrinkage/swelling behavior measuring apparatus according to the present invention;
FIG. 4a is a side view of the wood shrinkage/swelling behavior determination apparatus of the present invention;
FIG. 4b is a top view of the wood shrinkage/swelling behavior measuring apparatus according to the present invention;
FIG. 5 is a cross-sectional view of a quartz tray and a sample to be tested according to the present invention;
fig. 6 is a top view of the spacer of the present invention.
[ description of reference ]
1: a dynamic moisture adsorption analyzer;
101: a sample bin;
102: a gas flow controller;
2: a video white light microscope;
3: a quartz tray;
4: cushion blocks;
5: and (4) suspending the filaments.
Detailed Description
For the purpose of better explaining the present invention and to facilitate understanding, the present invention will be described in detail by way of specific embodiments with reference to the accompanying drawings.
Examples
As shown in fig. 1, a method for determining the drying shrinkage/swelling behavior of wood comprises the following steps:
s1: preparing a wood sample to be tested, and smoothing the surface to be tested of the sample by a slicer;
s2: cleaning a quartz tray 3 for placing a sample to be tested by using distilled water, and placing a cushion block 4 in the middle of the cleaned quartz tray 3;
s3: placing the sample to be tested obtained in the step S1 on the cushion block 4, then placing the quartz tray 3 into the sample bin 101, covering the cover body, and adjusting the temperature and the relative humidity of the sample bin 101 to be constant until the water content of the sample to be tested reaches an equilibrium state;
s4: setting a video white light microscope 2 which is used together with the dynamic moisture adsorption analyzer 1, keeping a fixed time interval, and continuously photographing the surface to be measured of the sample to be measured;
s5: analyzing the image obtained in the step S4;
s6: the Image obtained in step S5 is introduced into Image processing software (Image J) to be measured, and the dimensional change of the sample to be measured in the moisture desorption/adsorption process is obtained, and finally the change in the shrinkage/swelling of the sample to be measured is obtained.
In step S3, the test surface of the test sample is placed on the cushion block 4, and the tester can adjust the positions of the cushion block 4 and the test sample in the quartz tray according to the object to be photographed.
The determination method combines the dynamic moisture adsorption analyzer 1 with the video white light microscope 2, the video white light microscope 2 shoots and obtains images of the wood sample to be measured, a series of picture sets of the wood sample surface to be measured under different relative humidity are obtained, and the data of the size variation of the shrinkage/swelling under different equilibrium water content are obtained in situ and in real time by matching with the image processing technology in the cell scale.
Preferably, in step S3, the temperature in the sample chamber 101 is 5 to 50 ℃, and the relative humidity is 0 to 98%.
The temperature and the relative humidity in the sample bin 101 are adjustable, during experiments, different temperatures and different humidities can be adjusted to test the shrinkage/swelling size variation of the sample to be tested under different conditions, the range of the relative humidity which can be tested by the instrument is 0-98%, the highest relative humidity of a common instrument can be 90%, and the shrinkage/swelling variation data of the sample to be tested under different relative humidity conditions can be more comprehensively obtained by the method.
Preferably, in step S4, the pixels of the image captured by the video white light microscope 2 are 1280 × 960, and the interval time between the two images captured by the video white light microscope 2 can be adjusted according to the needs of the experimenter, which is 20S, 1min or 2min respectively.
Preferably, the analyzing the image obtained in step S4 in step S5 specifically includes: and adjusting the brightness, contrast, exposure, tone (RGB) curve and color level of the picture to enhance the details of the measuring region.
In step S5, the image is analyzed and processed, and a series of images captured by the video white light microscope 2 are imported into a photoshop (adobe system), so as to adjust the brightness, contrast, exposure, hue (RGB) curve and color level of the image, enhance the details of the measurement region, and achieve the purpose of image denoising.
Preferably, step S6 includes:
s61: importing the processed picture into Image processing software (Image J), firstly opening the Image processing software (Image J), selecting 'file-open', importing the picture, selecting 'analysis-set proportion' to scale for conversion and calibration;
s62: selecting 'image-type-8 bit' to modify the format of the picture to change the picture into a gray-scale picture, and selecting 'image-adjustment-threshold' to process the picture by using a threshold method;
s63: the area of the catheter cavity to be measured is selected by using a magic wand tool in Image processing software (Image J), and the area of the selected catheter cavity can be measured and recorded by selecting analysis-measurement.
As shown in fig. 2, the pictures processed by Photoshop processing and imported into Image processing software (Image J) are a grayscale picture in "8-bit" mode, a picture processed by thresholding, and a picture obtained by selecting the catheter lumen area using a "magic wand tool", respectively.
The wood wet swelling size variation calculation formula is as follows:
△Ssw＝Ssw-S0(1)
in the formula:
△Sswthe change of the swelling size of the tested catheter cavity in any relative humidity environment during the moisture absorption process is measured in the unit of mum2；
SswIs the area size of the tested catheter cavity when the water content reaches the equilibrium water content in any relative humidity environment in the water absorption process, and the unit is mum2；
S0Is the area size of the tested catheter cavity in an absolute dry state and has the unit of mum2；
The wood drying shrinkage size variation calculation formula is as follows:
△Ssh＝Ssh-S0(2)
in the formula:
△Sshthe change quantity of the drying shrinkage size of the tested catheter cavity in any relative humidity environment in the moisture desorption process is expressed in the unit of mum2；
SshThe area size of the measured catheter cavity when the water content reaches the equilibrium water content in any relative humidity environment in the water desorption process is expressed in the unit of mu m2；
S0Is the area size of the tested catheter cavity in an absolute dry state and has the unit of mum2。
S above0The area size of the tested catheter cavity in an oven-dry state is shown, and the oven-dry state refers to the state that the water content of the test sample is 0%.
As shown in fig. 3 and 4, the present invention also provides a wood drying shrinkage/swelling behavior measuring device used in the above measuring method, comprising:
a dynamic moisture adsorption analyzer 1 and a video white light microscope 2;
the dynamic moisture adsorption analyzer 1 comprises a sample bin 101 and a gas flow controller 102;
the sample bin 101 is positioned at the upper part of the gas flow controller 102, and the top of the sample bin 101 is provided with a cover body;
the video white light microscope 2 is positioned at the lower part of the dynamic moisture adsorption analyzer 1 and is electrically connected with the dynamic moisture adsorption analyzer 1;
the quartz tray 3 and the cushion block 4 are also included;
the quartz tray 3 is a bearing platform of a sample to be tested, the bottom of the quartz tray 3 is transparent, two support rods are symmetrically and fixedly arranged on the outer edge of the quartz tray 3, the two support rods extend upwards and intersect at one point to form a support, and a horizontal cross rod is fixedly arranged between the two support rods;
the cushion block 4 is made of rubber materials and is placed on the upper portion of the quartz tray 3.
The measuring equipment adopts the dynamic moisture adsorption analyzer 1 and the video white light microscope 2 to be used together, the cushion block is arranged on the quartz tray, the surface to be measured of the sample to be measured is supported by the cushion block, the surface to be measured of the sample to be measured can be freely and fully contacted with the gaseous water molecules in the sample bin 101 at the first time, and the picture shot by the video white light microscope 2 is real and accurate.
Preferably, the inner diameter of the quartz tray 3 is 17mm, the outer diameter is 19mm, and the top of the support of the quartz tray 3 is connected with a suspension wire 5 for lifting the quartz tray 3 in the sample chamber 101.
As shown in fig. 5, two support rods are symmetrically and fixedly arranged on the outer edge of the quartz tray 3 and extend upwards to intersect at a point to form a support, a cross rod is arranged on the support formed by the two support rods for supporting, a suspension wire 5 is connected to the top of the support, and the suspension wire 5 is used for hoisting the quartz tray 3 to put in or pull out the sample chamber 101.
As shown in fig. 6, the cushion block 4 is placed on the upper portion of the quartz tray 3 for cushioning a sample to be tested, during an experiment, the cushion block 4 is placed in the sample bin 101 along with the quartz tray 3, the cushion block 4 is made of a rubber material, an adjustable damp-heat environment (0-98% humidity, 5-50 ℃) exists in the sample bin 101, and the cushion block 4 needs to meet the conditions of no hygroscopicity, light weight and long-term work in the damp-heat environment;
the cushion block 4 should not influence the determination result of the hygroscopicity of the sample to be measured when the moisture desorption/sorption test is carried out;
the cushion block 4 ensures that the weight of the sample to be tested is lighter while the sample to be tested is supported, the weight is controlled to be 28-34mg, and the quartz tray 3 carrying the cushion block 4 and the sample to be tested sinks due to the overlarge weight of the cushion block 4, so that the bottom of the quartz tray 3 is in contact with the lens of the video white light microscope 2 below the quartz tray, and test data cannot be obtained; however, the mass of the cushion block 4 is too small, the cushion block 4 cannot support a sample to be tested, and the test cannot be carried out.
Preferably, the cushion block 4 is a rubber ring, the inner diameter of the rubber ring is 5.8-6.2mm, the outer diameter of the rubber ring is 6.8-7.2mm, the height of the rubber ring is 0.9-1.2 mm, and the rubber ring is provided with an opening.
The size of the cushion block 4 can meet the requirement that the mass of the cushion block 4 is between 28 and 34mg, the function of supporting the surface to be tested of the sample to be tested and not directly contacting the quartz tray 3 is achieved, and meanwhile, the phenomenon that the bottom of the quartz tray 3 is contacted with the lens of the video white light microscope 2 below the quartz tray 3 and test data cannot be obtained due to the fact that the quartz tray 3 sinks due to overlarge mass of the cushion block 4 is avoided.
Preferably, the inner diameter of the rubber ring is 6mm, the outer diameter of the rubber ring is 7mm, the height of the rubber ring is 1mm, and the opening of the rubber ring occupies 1/6-1/4 of the outer circumference of the rubber ring.
The cushion block 4 is designed by adopting a rubber ring, the inner diameter is 6mm, the outer diameter is 7mm, the height is 1mm, the quality requirement of the cushion block 4 can be met, and meanwhile, the rubber ring is provided with an opening occupying the outer circumference of 1/6-1/4, so that the surface to be measured of the sample to be measured can be freely and fully contacted with gaseous water molecules in the humidity environment of the sample bin 101;
when the rubber ring is subjected to opening treatment, the opening size can be 1/8, 1/6, 1/4 and 1/3 with the outer circumference, and through experiments, when a sample to be detected is placed on the rubber ring with the opening 1/3, the surface to be detected of the sample to be detected and the bottom of the quartz tray 3 cannot be in a completely parallel state, so that the sample to be detected is abandoned; rubber rings with other opening sizes and the same sample to be tested are respectively placed into a dynamic moisture adsorption analyzer 1 to measure the dry shrinkage/wet expansion size variation, and the dry shrinkage/wet expansion size variation is compared with that obtained by using rubber rings without openings or placing rubber rings;
the result is: 1/4 is approximately equal to 1/6 > 1/8 is approximately equal to no opening and no accessory, which indicates that when the size of the opening of the rubber ring is 1/8, the gaseous water molecules are blocked from entering the surface to be measured; when the size of the opening of the rubber ring is 1/6 or 1/4, gaseous water molecules can freely and sufficiently contact the surface to be measured, and the size of the opening of the rubber ring is preferably 1/4 of the outer circumference in consideration of easy processability and quality requirements.
The cushion block 4 is used for ensuring that the surface to be measured of the sample to be measured can freely and fully contact with gaseous water molecules in the humidity environment in the sample bin 101, so that the cushion block 4 can be a rubber ring with an opening, can be replaced by two cuboids, or a U-shaped ring body and the like, and plays a role in supporting the surface to be measured of the sample to be measured not to be attached to the bottom surface of the quartz tray 3;
the method has the advantages that the dry shrinkage/wet expansion behavior of the to-be-detected surface of the to-be-detected sample can synchronously respond to desorption/adsorption of moisture, synchronous real-time determination of the moisture content of the to-be-detected sample and the dry shrinkage/wet expansion size variation is realized, and the accuracy of the dry shrinkage/wet expansion size variation data is improved.
According to the method for determining the wood drying shrinkage/swelling behavior, a dynamic moisture adsorption analyzer 1 is combined with a video white light microscope 2, a series of picture sets of the wood sample surface to be measured under different relative humidity can be obtained, and drying shrinkage/swelling size variable quantity data under different equilibrium moisture content can be obtained in situ and in real time by matching with an image processing technology.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, and that such changes and modifications are to be considered as within the scope of the invention.
Claims (10)
1. A method for measuring wood drying shrinkage/wet swelling behavior is characterized by comprising the following steps:
s1: preparing a sample to be tested of the wood, and smoothing the surface to be tested of the sample by a slicer;
s2: cleaning a quartz tray (3) for placing a sample to be tested by using distilled water, and placing a cushion block (4) in the middle of the cleaned quartz tray (3);
s3: placing the sample to be tested obtained in the step S1 on the cushion block (4), then placing the quartz tray (3) into the sample bin (101), covering the cover body, and adjusting the temperature and the relative humidity of the sample bin (101) to be constant until the water content of the sample to be tested reaches a water content equilibrium state;
s4: setting a video white light microscope (2) which is used together with the dynamic moisture adsorption analyzer (1), keeping a fixed time interval, and continuously photographing the surface to be measured of the sample to be measured;
s5: analyzing the image obtained in the step S4;
s6: and (4) introducing the image obtained in the step (S5) into image processing software for measurement, obtaining the size change of the sample to be measured in the moisture desorption/adsorption process, and finally obtaining the dry shrinkage/wet expansion change quantity of the sample to be measured.
2. The method of measuring according to claim 1,
in step S3, the temperature in the sample bin (101) is 5-50 ℃, and the relative humidity is 0-98%.
3. The method of measuring according to claim 1,
in step S4, the pixels of the image taken by the video white light microscope (2) are 1280 × 960, and the interval between the automatic picture taking by the video white light microscope (2) is 20S, 1min or 2 min.
4. The method of measuring according to claim 1,
in the step S5, the analyzing process performed on the image obtained in S4 specifically includes: and adjusting the brightness, contrast, exposure, tone curve and color level of the picture, and enhancing the details of the measurement area.
5. The method of measuring according to claim 4,
step S6 includes:
s61: importing the processed picture into image processing software, firstly opening the image processing software, selecting 'file-open', importing the picture, and selecting 'analysis-set proportion' to carry out conversion calibration on a scale;
s62: selecting 'image-type-8 bit' to modify the format of the picture to change the picture into a gray-scale picture, and selecting 'image-adjustment-threshold' to process the picture by using a threshold method;
s63: the area of the catheter cavity to be determined is selected by using a magic stick tool in the image processing software, and the area of the selected catheter cavity can be measured and recorded by selecting analysis-measurement.
6. The method of measuring according to claim 5,
the wood wet swelling size variation calculation formula:
△Ssw＝Ssw-S0 (1)
in the formula:
△Sswthe change of the swelling size of the tested catheter cavity in any relative humidity environment during the moisture absorption process is measured in the unit of mum2；
SswIs the area size of the tested catheter cavity when the water content reaches the equilibrium water content in any relative humidity environment in the water absorption process, and the unit is mum2；
S0Is the area size of the tested catheter cavity in an absolute dry state and has the unit of mum2；
The wood drying shrinkage size variation calculation formula is as follows:
△Ssh＝Ssh-S0 (2)
in the formula:
△Sshthe change quantity of the drying shrinkage size of the tested catheter cavity in any relative humidity environment in the moisture desorption process is expressed in the unit of mum2；
SshThe area size of the measured catheter cavity when the water content reaches the equilibrium water content in any relative humidity environment in the water desorption process is expressed in the unit of mu m2；
S0Is the area size of the tested catheter cavity in an absolute dry state and has the unit of mum2。
7. A wood drying/swelling behavior measuring apparatus used in the measuring method according to any one of claims 1 to 6, comprising:
the device comprises a dynamic moisture adsorption analyzer (1) and a video white light microscope (2);
the dynamic moisture adsorption analyzer (1) comprises a sample bin (101) and a gas flow controller (102);
the sample bin (101) is positioned at the upper part of the gas flow controller (102), and the top of the sample bin (101) is provided with a cover body;
the video white light microscope (2) is positioned at the lower part of the dynamic moisture adsorption analyzer (1) and is electrically connected with the dynamic moisture adsorption analyzer (1);
the quartz tray (3) and the cushion block (4) are also included;
the quartz tray (3) is a bearing platform for a sample to be tested, the bottom of the quartz tray (3) is transparent, two support rods are symmetrically and fixedly arranged on the outer edge of the quartz tray (3), the upper parts of the two support rods extend and intersect at one point to form a support, and a horizontal cross rod is fixedly arranged between the two support rods;
the cushion block (4) is made of rubber materials and is placed on the upper portion of the quartz tray (3).
8. The measuring device according to claim 7, wherein the quartz tray (3) has an inner diameter of 17mm and an outer diameter of 19 mm;
the top of the quartz tray (3) support is connected with a suspension wire (5) for lifting the quartz tray (3) in the sample bin (101).
9. The assay device according to claim 7,
the cushion block (4) is a rubber ring, the inner diameter of the rubber ring is 5.8-6.2mm, the outer diameter of the rubber ring is 6.8-7.2mm, the height of the rubber ring is 0.9-1.2 mm, and the rubber ring is provided with an opening.
10. The assay device according to claim 9,
the inner diameter of the rubber ring is 6mm, the outer diameter of the rubber ring is 7mm, the height of the rubber ring is 1mm, and the opening size of the rubber ring accounts for 1/6-1/4 of the outer circumference of the rubber ring.
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