Wood drying shrinkage measuring method, medium and equipment

Abstract

The invention discloses a wood drying shrinkage measuring method, medium and equipment, and relates to the field of wood drying, and the wood drying shrinkage measuring method comprises the following steps: obtaining measured wood, obtaining a wood test piece and a wood cross section slice, drying the wood test piece, and determining the relationship between the water content and the chordwise drying shrinkage rate and the radial drying shrinkage rate of the wood test piece; the wood cross section slice is evenly divided into a plurality of layers, each layer is evenly divided into a plurality of sub-areas, and the texture angle of each sub-area in a certain layer of the wood cross section slice is determined; according to the chordwise dry shrinkage rate and the radial dry shrinkage rate of the wood test piece and the texture angle of each sub-region in a certain layer of the wood cross section slice, the free dry shrinkage rate of a corresponding layer is determined; and repeating the steps to obtain the free dry shrinkage rate of each layer of the tested wood. According to the method, the free dry shrinkage of each layer of the wood is obtained by obtaining the relationship among the chordwise dry shrinkage, the radial dry shrinkage and the water content of the tested wood and the texture angle, so that the free dry shrinkage of each layer of the wood is rapidly and accurately obtained.

Description

Technical Field

[0001] The invention relates to the technical field of wood drying, and in particular to a wood shrinkage measurement method, medium and equipment. Background Art

[0002] With the improvement of the living standards of Chinese people, wood with many advantages such as natural, environmentally friendly and heat-insulating has become popular. Drying is an important part of wood utilization. The uneven distribution of moisture content at each point of wood during drying and the anisotropy of wood shrinkage lead to asynchronous shrinkage at different positions of wood and cause drying stress in wood. Drying stress is the main factor causing cracking, bending and other drying defects in wood, which seriously affects the utilization of wood.

[0003] The slicing method is currently the most widely used means of measuring drying strain. The slicing method is to saw slices off the wood and determine the condition of the entire wood by the strain of the slices. Free shrinkage is a necessary item in the research related to wood drying strain. Nowadays, the measurement of free shrinkage also uses the slicing method. When the wood has not yet produced drying stress, such as in a saturated state, slices are taken and decomposed into multiple layers so that each layer is in a free shrinkage state, and the relationship between the free shrinkage and the moisture content of each layer in the thickness of the wood is determined; however, when the slicing method is used to measure free shrinkage, it is necessary to measure the relationship between the shrinkage rate and the moisture content of all layers in the thickness direction. When there are many layers, the workload is too large, resulting in a slow shrinkage rate measurement speed; and the shrinkage of wood is greatly affected by the growth ring texture. There are certain differences in the growth ring texture of each cross section in the length direction of the wood. Therefore, when the slicing method is used to measure free shrinkage, the obtained free shrinkage of the wood is not accurate enough. Summary of the invention

[0004] The present invention provides a wood shrinkage measurement method, medium and device to solve the above-mentioned problem existing in the prior art, that is, how to quickly and accurately obtain the free shrinkage rate of each layer of wood in the prior art. The present invention provides a wood shrinkage measurement method, which comprises:

[0005] Obtaining the wood to be tested, obtaining the wood specimen and the wood cross-sectional slice;

[0006] The wood specimens were dried to determine the relationship between moisture content and tangential shrinkage and radial shrinkage;

[0007] Divide the wood cross section slice into several layers along the wood thickness direction, divide each layer into several sub-regions, and determine the texture angle of each sub-region in a certain layer of the wood cross section slice; wherein the texture angle is the angle between the texture in the sub-region and the layer separation line;

[0008] According to the relationship between moisture content and tangential shrinkage rate, radial shrinkage rate, and the texture angle of each sub-region in a certain layer of the wood cross-section slice, the shrinkage length of each sub-region is obtained, and the shrinkage length of the corresponding layer is obtained according to the shrinkage length of each sub-region, and the free shrinkage rate of the corresponding layer is determined;

[0009] Repeat the above steps to obtain the free shrinkage rate of each layer of the tested wood.

[0010] Optionally, the drying of the wood specimen to determine the relationship between the moisture content and the tangential shrinkage and radial shrinkage may include:

[0011] During the drying process of the wood specimens, the measured values ​​of the tangential shrinkage and radial shrinkage corresponding to the moisture content at different times were obtained to determine the relationship between the moisture content and the tangential shrinkage and radial shrinkage.

[0012] Optionally, determining the relationship between the moisture content and the tangential shrinkage rate and the radial shrinkage rate specifically includes:

[0013] According to the relationship between moisture content and tangential shrinkage and radial shrinkage, when the moisture content is lower than the fiber saturation point, the tangential shrinkage and radial shrinkage are obtained using the following formula:

[0014]

[0015] Among them, MC is the water content, MC fsp is the fiber saturation point, S t is the chord-wise shrinkage, S tmax is the tangential total shrinkage, S r is the radial shrinkage rate, S rmax is the radial total shrinkage rate;

[0016] When the moisture content is higher than the fiber saturation point, the tangential shrinkage and radial shrinkage are both 0.

[0017] Optionally, the step of slicing the wood cross section into a plurality of layers along the thickness direction of the wood and dividing each layer into a plurality of sub-regions specifically includes:

[0018] The wood cross section is sliced ​​into a layer every 5 mm along the thickness direction of the wood, and each layer is divided into several sub-areas at intervals of 10 mm along the inter-layer dividing line.

[0019] Optionally, the method of obtaining the shrinkage length of each sub-region according to the relationship between the moisture content and the tangential shrinkage rate and the radial shrinkage rate, and the texture angle of each sub-region in a certain layer of the wood cross-sectional slice, obtaining the shrinkage length of the corresponding layer according to the shrinkage length of the sub-region, and determining the free shrinkage rate of the corresponding layer specifically includes:

[0020] According to the tangential shrinkage rate, radial shrinkage rate, and the texture angle of each sub-region in a certain layer of the wood cross-section slice, the following formula is used to obtain the length of each sub-region after shrinkage:

[0021]

[0022] Among them, l' is the length of the sub-region after shrinkage, l is the original length of the sub-region, and α is the texture angle.

[0023] According to the length after shrinkage of each region, the following formula is used to obtain the length after shrinkage of the corresponding layer:

[0024]

[0025] Wherein, L' is the length after shrinkage, i is the sub-region number;

[0026] According to the length of the corresponding layer after shrinkage, the free shrinkage rate of the layer is obtained using the following formula:

[0027]

[0028] Among them, L is the original length of a layer, and S is the free shrinkage rate corresponding to the layer.

[0029] The present invention provides a computer-readable storage medium, wherein the storage medium stores a computer program, and when the computer program is executed by a processor, the above-mentioned wood shrinkage measurement method is implemented.

[0030] The present invention provides a computer device, comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the above-mentioned wood shrinkage measurement method when executing the program.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention provides a method for measuring wood shrinkage, which obtains the wood to be tested, obtains a wood specimen and a wood cross-sectional slice, dries the wood specimen, and determines the relationship between its moisture content and the tangential shrinkage rate and the radial shrinkage rate; divides the wood cross-sectional slice into several layers, divides each layer into several sub-regions, and determines the texture angle of each sub-region in a certain layer of the wood cross-sectional slice; determines the free shrinkage rate of the corresponding layer according to the tangential shrinkage rate and radial shrinkage rate of the wood specimen, and the texture angle of each sub-region in a certain layer of the wood cross-sectional slice; repeats the above steps to obtain the free shrinkage rate of each layer of the wood to be tested, and since the tangential and radial shrinkage rates at each position in the same root of wood have small variability, the free shrinkage rate of each layer of the wood can be obtained quickly and accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0033] Figure 1 A flow chart of a wood shrinkage measurement method provided by an embodiment of the present invention;

[0034] Figure 2 A comparison scatter plot between a theoretical value of the free shrinkage rate of each layer and an actual measured value of the free shrinkage rate of each layer in a wood shrinkage measurement method provided by an embodiment of the present invention;

[0035] Figure 3 A schematic diagram of a computer device for a wood shrinkage measurement method provided by an embodiment of the present invention.

[0036] The above drawings have shown clear embodiments of the present invention, which will be described in more detail below. These drawings and text descriptions are not intended to limit the scope of the present invention in any way, but to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] At present, the slicing method is a traditional strain measurement method. When measuring free shrinkage, it is necessary to measure the shrinkage rate of all layers in the thickness direction as it changes with the moisture content. When there are many layers, the workload is too large, and the growth ring texture of the wood cross section has certain differences. Only by measuring the shrinkage properties of the slice layer, the measurement results of the entire piece of wood have certain limitations, which leads to inaccurate measurement results.

[0039] In view of the above problems, the present invention provides a method for measuring wood shrinkage. The method obtains the relationship between the tangential shrinkage rate, radial shrinkage rate and moisture content of the wood specimen, as well as the texture angle α, to obtain the free shrinkage rate of each layer of the wood, thereby achieving fast and accurate acquisition of the free shrinkage rate of each layer of the wood.

[0040] The technical solution of the present invention and how the technical solution of the present invention solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present invention will be described below in conjunction with the accompanying drawings.

[0041] Figure 1 : is a flow chart of a wood shrinkage measurement method provided by an embodiment of the present invention, such as Figure 1 As shown, this embodiment shows a method for measuring wood shrinkage, comprising:

[0042] S101: Obtain the wood to be tested, and obtain the wood specimen and the wood cross-sectional slice.

[0043] For example, a slice with a thickness of 10 mm can be sawed from 50 mm away from the end of the wood, and a square wood specimen can be taken from the slice. The thickness of the square wood specimen is the same as the slice, and its length and width directions correspond to the chord and radial directions of the slice cross section, respectively.

[0044] Optionally, the wood specimen size is 20 mm × 20 mm × 10 mm.

[0045] It should be noted that when taking square wood specimens, all positions of the slices should be included as much as possible, and as many as possible should be taken to effectively reflect the shrinkage characteristics of the wood.

[0046] S102: Dry the wood specimens to determine the relationship between the moisture content and the tangential shrinkage and radial shrinkage.

[0047] Optionally, the wood specimen is placed in water to make it saturated with water, and then the saturated wood specimen is dried, and the tangential shrinkage rate, radial shrinkage rate, and mass of the wood are measured at intervals until the mass of the specimen no longer changes, which is the absolute dry mass of the specimen, thereby determining the moisture content of the specimen; for example, the saturated wood specimen can be placed in an oven for drying, and the temperature can be set to 103±2°C;

[0048] For example, with the moisture content as the horizontal axis and the shrinkage rate as the vertical axis, a scatter plot of the tangential shrinkage rate-moisture content and radial shrinkage rate-moisture content of the wood to be tested is drawn. For example, points with a moisture content greater than 30% can be removed, and the tangential shrinkage rate scatter points are fitted into a straight line, and the radial shrinkage rate scatter points are fitted into the same way, and the horizontal intercepts of the two fitted straight lines are made equal. The horizontal intercepts of the chord and radial shrinkage rate-moisture content straight lines are the fiber saturation point MC. fsp The vertical axis intercepts of the two straight lines are respectively used as the chord-wise total shrinkage rate S of the wood to be tested. tmax , radial total shrinkage rate S rmaxIn this embodiment, a total of 8 (ah) woods were tested. After measurement and sorting, the tangential total shrinkage rate, tangential total shrinkage rate variation coefficient, radial total shrinkage rate and radial total shrinkage rate variation coefficient of each wood are shown in Table 1.

[0049] Table 1 Total shrinkage of each test piece

[0050]

[0051] Combined with the data in Table 1, when the moisture content is lower than the fiber saturation point, the following formula is used to obtain the relationship between the chord shrinkage rate St (%), radial shrinkage rate Sr (%) and moisture content MC (%):

[0052]

[0053] It should be noted that when the moisture content is higher than the fiber saturation point, the chord shrinkage S t (%), radial shrinkage rate S r Both are 0.

[0054] S103: Divide the wood cross section slice into a plurality of layers along the wood thickness direction, divide each layer into a plurality of sub-regions, and determine the texture angle of each sub-region in a certain layer of the wood cross section slice.

[0055] Optionally, the wood cross-section slice is divided into several layers every 5 mm, each layer is equally divided into 10 sub-regions and each sub-region is numbered, and the texture angles α of the 10 sub-regions in each layer are obtained respectively.

[0056] The texture angle is the angle between the texture and the layer separation line in the sub-region.

[0057] S104: According to the relationship between the moisture content and the tangential shrinkage rate and the radial shrinkage rate, and the texture angle of each sub-region in a certain layer of the wood cross-sectional slice, the shrinkage length of each sub-region is obtained, and the shrinkage length of the corresponding layer is obtained according to the shrinkage length of the sub-region, and the free shrinkage rate of the corresponding layer is determined.

[0058] Optionally, the length of each sub-region after shrinkage is obtained by using the following formula according to the tangential shrinkage rate, radial shrinkage rate, and the grain angle of each sub-region in a certain layer of the wood cross-section slice:

[0059]

[0060] Among them, l' is the length of the sub-region after shrinkage, l is the original length of the sub-region, and α is the texture angle.

[0061] According to the length after shrinkage of each region, the following formula is used to obtain the length after shrinkage of the corresponding layer:

[0062]

[0063] Wherein, L' is the length after shrinkage, i is the sub-region number;

[0064] According to the length of the corresponding layer after shrinkage, the free shrinkage rate of the layer is obtained using the following formula:

[0065]

[0066] Among them, L is the original length of a layer, and S is the free shrinkage rate corresponding to the layer.

[0067] S105: Repeat the above steps to obtain the free shrinkage rate of each layer of the tested wood.

[0068] The measured values ​​of the free shrinkage rates of each layer measured by the actual measurement are compared with the theoretical values ​​of the free shrinkage rates of each layer obtained by the present invention. Taking the total shrinkage rate when absolutely dry as an example, the total shrinkage rates of each layer of 8 wood materials are as follows: Figure 2 As shown, the theoretical value and the measured value are relatively close, indicating that the method of measuring the relationship between the texture angle, chordal shrinkage, radial shrinkage and moisture content and calculating the free shrinkage of each layer based on the two is feasible.

[0069] The present invention also provides a computer-readable storage medium, which stores a computer program. The computer program can be used to execute the wood shrinkage measurement method provided above.

[0070] The present invention also provides Figure 3 The structural diagram of the computer device shown in FIG. Figure 3 As shown, at the hardware level, the computer device includes a processor, an internal bus, a network interface, a memory, and a non-volatile memory, and may also include hardware required for other services. The processor reads the corresponding computer program from the non-volatile memory into the memory and then runs it to implement the wood shrinkage measurement method provided in the above embodiment.

[0071] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided by the present invention can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory or optical memory, etc. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0072] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of the present invention.

Claims

1. A method for measuring wood shrinkage, characterized in that: include: Obtaining the wood to be tested, obtaining the wood specimen and the wood cross-sectional slice; The wood specimens were dried to determine the relationship between moisture content and tangential shrinkage and radial shrinkage; Divide the wood cross section slice into several layers along the wood thickness direction, divide each layer into several sub-regions, and determine the texture angle of each sub-region in a certain layer of the wood cross section slice; wherein the texture angle is the angle between the texture in the sub-region and the layer separation line; According to the relationship between moisture content and tangential shrinkage rate, radial shrinkage rate, and the texture angle of each sub-region in a certain layer of the wood cross-section slice, the shrinkage length of each sub-region is obtained, and the shrinkage length of the corresponding layer is obtained according to the shrinkage length of each sub-region, and the free shrinkage rate of the corresponding layer is determined; Repeat the above steps to obtain the free shrinkage rate of each layer of the tested wood.

2. The method for measuring wood shrinkage according to claim 1, characterized in that: The drying of the wood specimen to determine the relationship between the moisture content and the tangential shrinkage and radial shrinkage specifically includes: During the drying process of the wood specimens, the measured values ​​of the tangential shrinkage and radial shrinkage corresponding to the moisture content at different times were obtained to determine the relationship between the moisture content and the tangential shrinkage and radial shrinkage.

3. The method for measuring wood shrinkage according to claim 2, characterized in that: Determining the relationship between the moisture content and the tangential shrinkage rate and the radial shrinkage rate specifically includes: According to the relationship between moisture content and tangential shrinkage and radial shrinkage, when the moisture content is lower than the fiber saturation point, the tangential shrinkage and radial shrinkage are obtained using the following formula: Among them, MC is the water content, MC fsp is the fiber saturation point, S t is the chord-wise shrinkage, S tmax is the tangential total shrinkage, S r is the radial shrinkage rate, S rmax is the radial total shrinkage rate; When the moisture content is higher than the fiber saturation point, the tangential shrinkage and radial shrinkage are both 0.

4. The method for measuring wood shrinkage according to claim 1, characterized in that: The method of slicing the wood cross section into a plurality of layers along the thickness direction of the wood and dividing each layer into a plurality of sub-regions specifically includes: The wood cross section is sliced ​​into a layer every 5 mm along the thickness direction of the wood, and each layer is divided into several sub-areas at intervals of 10 mm along the inter-layer dividing line.

5. The method for measuring wood shrinkage according to claim 1, characterized in that: The method of obtaining the shrinkage length of each sub-region according to the relationship between the moisture content and the tangential shrinkage rate and the radial shrinkage rate, and the texture angle of each sub-region in a certain layer of the wood cross-section slice, obtaining the shrinkage length of the corresponding layer according to the shrinkage length of the sub-region, and determining the free shrinkage rate of the corresponding layer specifically includes: According to the tangential shrinkage rate, radial shrinkage rate, and the texture angle of each sub-region in a certain layer of the wood cross-section slice, the following formula is used to obtain the length of each sub-region after shrinkage: Among them, l' is the length of the sub-region after shrinkage, l is the original length of the sub-region, and α is the texture angle. According to the length after shrinkage of each region, the following formula is used to obtain the length after shrinkage of the corresponding layer: Wherein, L' is the length after shrinkage, and i is the sub-region number; According to the shrinkage length of the corresponding layer, the free shrinkage rate of the layer is obtained using the following formula: Among them, L is the original length of a layer, and S is the free shrinkage rate corresponding to the layer.

6. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and when the computer program is executed by a processor, the wood shrinkage measurement method according to any one of claims 1 to 5 is implemented.

7. A computer device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method for measuring wood shrinkage according to any one of claims 1 to 5 is implemented.

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