Online testing method and device for strain field during hot pressing of reconstituted bamboo slabs

Abstract

The present invention discloses an online testing method and device for the strain field during the hot pressing process of a reconstructed bamboo slab. The testing method uses the end face of a painted bamboo bundle as a strain observation surface to obtain the displacement deformation between the same strain observation surface and the reference strain observation surface at different hot pressing moments, thereby detecting the strain behavior of the reconstructed bamboo slab during the hot pressing process. Compared with the displacement strain sensors currently used, the present invention can accurately obtain the strain of the reconstructed bamboo slab during the hot pressing process, greatly reducing the measurement error caused by small differences in the slab strain field. Compared with other popular stress field detection methods based on image recognition on the market, the present invention uses the end face of the painted bamboo bundle as the strain observation surface to solve the problem of difficulty in taking points due to uneven levels of the slab end face. It has low cost and small strain field measurement error, effectively overcoming the limitations of the current mainstream digital speckle method on the complex production site of reconstructed bamboo, while ensuring that the measurement accuracy meets actual production needs while reducing the measurement cost.

Description

Technical Field

[0001] The present invention relates to the technical field of stress-strain research during hot pressing of reconstituted bamboo slabs, and in particular to an online testing method and device for strain field during hot pressing of reconstituted bamboo slabs. Background Art

[0002] Recombinant bamboo is made into bamboo-based composites using impregnated bamboo bundles that have undergone fiber orientation separation, heat treatment, resin impregnation, and drying as the basic unit. Prior to hot pressing, the impregnated bamboo bundles are manually laid out into impregnated bamboo bundle slabs approximately 200 mm thick. During the hot pressing process, as the hot press platens rapidly close, heat is first transferred to the upper and lower surfaces (layers) of the slab, and then gradually to the core layer, until the slab is compressed to the target thickness (20-35 mm). Due to the large size of the impregnated bamboo bundles and the varying width, thickness, and degree of debonding within each bundle, manual laying cannot guarantee uniformity in all directions. Consequently, during hot pressing, the strain distribution in the impregnated bamboo bundle slabs exhibits non-uniformity in both thickness and width. Furthermore, when the target slab thickness is large, the heat transfer path from the surface to the core is long and inefficient, resulting in a prolonged softening and resin curing time for the core layer. This creates a temperature gradient through the thickness, which is higher on the outside and lower on the inside, leading to more pronounced variations in the strain field through the thickness. Similar to the thickness direction, the width direction is also affected by thermal stress. However, because the width direction is much larger and subject to less thermal compression constraints, the strain in the width direction is less pronounced than in the thickness direction. However, it can still affect the uniformity of the density distribution of reconstructed bamboo after hot pressing. The strain characteristics during hot pressing significantly affect the physical and mechanical properties of the reconstructed bamboo mat after hot pressing, such as density uniformity, flexural strength, and internal bond strength. Deciphering the strain characteristics of the hot pressing process is of great significance.

[0003] Currently, displacement sensors are commonly used to measure strain during the hot pressing of artificial board blanks. This method is commonly used for measuring strain during the hot pressing of traditional artificial boards such as particleboard and fiberboard. Particleboard and fiberboard have small basic unit dimensions (particle length, width, and thickness are approximately 3 mm × 1 mm × 0.25 mm, fiber length is approximately 2 mm, and diameter is approximately 15 μm). These materials are easily compressed during hot pressing, resulting in minimal strain field variability. Displacement sensors can therefore meet the required strain measurement accuracy requirements. However, reconstructed bamboo blanks, which use bamboo bundles as basic units (length, width, and thickness are 2500 mm, 30-50 mm, and 5-8 mm), experience high compression (approximately 80%) and long compression paths (approximately 140-180 mm) during hot pressing. This results in significant variability in the compressive strain field through the thickness of the blank. Measuring only the total strain through the thickness of the blank during hot pressing is insufficient to support research on the effects of hot pressing on the physical and mechanical properties of reconstructed bamboo.

[0004] Image recognition technology has applications in many fields. Digital image quantization (DIC) strain measurement, derived from this technology, is a novel non-contact optical measurement method that obtains surface motion and deformation information based on grayscale analysis of speckle images on the surface of an object. Existing digital speckle measurement equipment, such as the ARAMIS system from GOM (Germany) and the VIC3D from CSI (USA), is expensive and requires high quality and shape of the sprayed speckle patterns. However, the end surfaces of artificially installed impregnated bamboo bundles have numerous cracks and gaps, resulting in irregular surfaces. Measuring the strain field during hot pressing using planar digital speckle measurement requires flattening the end surfaces, which is not practical in actual production. In the actual production of reconstructed bamboo, a cyclic multi-layer hot press is used. The slabs are large, approximately 2500 mm (length) × 1300 mm (width) × 300 mm (thickness). The hot pressing environment is subject to frequent high-temperature steam leakage, resulting in a poor working environment. Therefore, implementing digital speckle measurement in this environment is complex, costly, and limited in applicability.

[0005] For example, there is a technical solution that uses image processing to measure the shear strain of certain slabs after loading. Before image processing, grid nodes are used to mark the upper and lower surfaces of the slabs, and the total strain is calculated by the displacement offset of the marked grid nodes. The applicant found that these slabs themselves are a whole plane, the plane is complete and there is no interference from other elements. The grid nodes on the upper surface can correspond one to one with the grid nodes on the lower surface. However, for reconstructed bamboo slabs, the reconstructed bamboo slabs are based on bamboo bundles as the basic units. After the bamboo bundle slabs are laid, the bamboo bundles are easily intertwined and entangled with each other, resulting in the slab surface not being completely flat, and there are a large number of uneven cracks on the surface. The use of grid node marking on the surface is prone to large errors in image processing, and it is difficult to truly reflect the production and development of strain during the hot pressing process of the bamboo bundle slabs. Summary of the Invention

[0006] In order to solve the problems existing in the prior art, the present invention provides a method and device for online testing the strain field during the hot pressing process of a reconstituted bamboo slab with low cost and high measurement accuracy.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] An online testing method for strain field during hot pressing of a reconstituted bamboo slab comprises the following steps:

[0009] S1, obtaining end surface images of the reconstituted bamboo slab at different times during the hot pressing process;

[0010] S2, respectively identifying the painted end faces of the bamboo bundles in each end face image as the strain observation faces;

[0011] S3, respectively calculating the distance between each strain observation surface and the specified reference strain observation surface;

[0012] S4. Calculate the strain amount ε of each strain observation surface based on the change in the spacing between each strain observation surface and the specified reference strain observation surface in the end face image, thereby obtaining a hot pressing process strain field composed of the strain amounts ε of each strain observation surface during the hot pressing process.

[0013] As a further improvement to the above technical solution:

[0014] Preferably, in step S2, the reconstituted bamboo slab is a multi-layer structure formed by paving a plurality of bamboo bundles, and the bamboo bundles with painted ends are spaced apart in rows and columns along the transverse and longitudinal ends of the reconstituted bamboo slab.

[0015] Preferably, in step S2, in each column of bamboo bundles of the reconstructed bamboo slab, the number of bamboo bundles with painted end surfaces is 3 to 6, and in each row of bamboo bundles, the number of bamboo bundles with painted end surfaces is 3 to 6.

[0016] Preferably, in step S2, the end surface color of the bamboo bundle with painted end surface is red, and the end surface color of the bamboo bundles other than the painted end surface bamboo bundles is white or the original color of the bamboo bundle (the original color of the bamboo bundle refers to the color of the bamboo bundle itself, which is not painted).

[0017] Preferably, in step S2, identifying the painted bamboo bundle end faces in each end face image includes: adjusting the contrast and brightness of the end face image, and adjusting the color sampling value based on the color of the painted bamboo bundle end faces so that all the painted bamboo bundle end faces have clear boundaries with the background color.

[0018] Preferably, in step S3, the designated reference strain observation surface corresponding to each strain observation surface is specifically one of the following definitions: Definition 1: the strain observation surface where the bamboo bundle is located in the same column of the reconstructed bamboo slab as the strain observation surface and whose end surface in the middle of the column is painted; Definition 2: the strain observation surface where the bamboo bundle is located in the same row of the reconstructed bamboo slab as the strain observation surface and whose outermost end surface is painted.

[0019] Preferably, when the reference strain observation surface is the strain observation surface located in the same row as the reconstituted bamboo slab and where the bamboo bundle with the painted end surface in the middle of the row is located, step S3 includes the following steps:

[0020] C1. The strain observation surface where the bamboo bundle in the middle of the row of reconstructed bamboo slabs is located is designated as the reference strain observation surface;

[0021] C2. Measure the distance between the strain observation surface and the reference strain observation surface in the same column of the end-face image at adjacent moments and calculate the distance change Δl;

[0022] C3. Divide the spacing change Δl by the spacing l between the strain observation surface and the reference strain observation surface in the end face image at the previous moment to obtain the strain value ε, thereby obtaining the hot pressing process strain field composed of the strain values ​​ε of each strain observation surface during the hot pressing process.

[0023] When the reference strain observation surface is the strain observation surface of the bamboo bundle located in the same row as the reconstituted bamboo slab and having the outermost end surface painted, step S3 includes the following steps:

[0024] D1. The strain observation surface where the outermost bamboo bundle of the reconstructed bamboo slab is located is designated as the reference strain observation surface;

[0025] D2. Measure the distance between the strain observation surface and the reference strain observation surface in the same row of the end-face image at adjacent moments and calculate the distance change Δl;

[0026] D3. Divide the spacing change Δl by the spacing l between the strain observation surface and the reference strain observation surface in the end face image at the previous moment to obtain the strain value ε, thereby obtaining the hot pressing process strain field composed of the strain values ​​ε of each strain observation surface during the hot pressing process.

[0027] Preferably, the calculation function expression of the spacing change Δl is Δl=l1-l2, l1 is the spacing between the strain observation surface and the reference strain observation surface at time T1, l2 is the spacing between the strain observation surface and the reference strain observation surface at time T2, T1 is the previous moment, and T2 is the next moment.

[0028] Preferably, when the reference strain observation surface is the strain observation surface located in the same column as the reconstituted bamboo slab and where the bamboo bundle with the painted end surface in the middle of the column is located, in step C2, when the strain observation surface is located above the reference strain observation surface, the distance between the upper boundary of the reference strain observation surface and the lower boundary of the strain observation surface is used as the spacing between the strain observation surface and the reference strain observation surface; when the strain observation surface is located below the reference strain observation surface, the distance between the lower boundary of the reference strain observation surface and the upper boundary of the strain observation surface is used as the spacing between the strain observation surface and the reference strain observation surface.

[0029] When the reference strain observation surface is the strain observation surface located in the same row as the reconstituted bamboo slab and having the outermost end surface of the bamboo bundle painted, in step D2, when the strain observation surface is located to the left of the reference strain observation surface, the distance between the right boundary of the reference strain observation surface and the left boundary of the strain observation surface is used as the spacing between the strain observation surface and the reference strain observation surface;

[0030] When the strain observation surface is located on the right side of the reference strain observation surface, the distance between the left boundary of the reference strain observation surface and the right boundary of the strain observation surface is the spacing between the strain observation surface and the reference strain observation surface.

[0031] As a general inventive concept, the present invention also provides an online testing device for strain field during hot pressing of reconstituted bamboo slabs, comprising the following modules:

[0032] An image processing module is used to obtain end surface images of the reconstituted bamboo slab at different times during the hot pressing process;

[0033] An image recognition module is used to respectively identify the painted end faces of the bamboo bundles in each end face image as strain observation faces;

[0034] A first calculation module is used to calculate the distance between each strain observation surface and a specified reference strain observation surface;

[0035] The second calculation module is used to calculate the strain amount ε of each strain observation surface based on the change in the distance between each strain observation surface and the specified reference strain observation surface in the end face image, thereby obtaining the hot pressing process strain field composed of the strain amount ε of each strain observation surface during the hot pressing process.

[0036] As a general inventive concept, the present invention also provides an online testing device for the strain field during the hot pressing process of reconstituted bamboo slabs. The device includes a memory and a processor. The memory stores a computer program. When the computer program is executed by the processor, an online testing method for the strain field during the hot pressing process of reconstituted bamboo slabs is implemented.

[0037] As a general inventive concept, the present invention also provides a storage medium having a computer program stored thereon, which can be executed by one or more processors to implement an online testing method for the strain field during the hot pressing process of reconstituted bamboo slabs.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention presents an online strain field measurement method and device for hot-pressing reconstituted bamboo slabs. Using the end faces of painted bamboo bundles as strain observation surfaces, the displacement deformation between the same strain observation surface and a reference strain observation surface at different hot-pressing moments is obtained, thereby detecting the strain behavior of the reconstituted bamboo slab during hot-pressing. In this method, rather than simply acquiring images after the hot-pressing process, the method performs in-process detection, obtaining overall shear strain and strain field measurements using the strain observation surface. Compared to displacement strain sensors currently used in production, the present invention can accurately measure the strain of the reconstituted bamboo slab during hot-pressing (especially in different thickness directions), significantly reducing measurement errors caused by small differences in the slab strain field. Compared to other popular stress field detection methods based on image recognition, the present invention uses the end faces of painted bamboo bundles as strain observation surfaces to solve the problem of difficult point acquisition due to uneven slab end faces. This method offers low cost and low strain field measurement errors, effectively overcoming the limitations of current mainstream digital speckle methods in complex reconstituted bamboo production sites. While ensuring measurement accuracy that meets actual production needs, it also reduces measurement costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the calibration of the slab strain measurement surface when the hot pressing time is 0 ms in Example 1.

[0041] Figure 2 This is a schematic diagram of the end face of the slab after image enhancement processing at a hot pressing time of 0 ms in Example 1.

[0042] Figure 3 This is a schematic diagram of image distance calibration when the hot pressing time is 0ms in Example 1.

[0043] Figure 4 This is a schematic diagram of image distance calibration when the hot pressing time is 200ms in Example 1.

[0044] Figure 5 This is a schematic diagram of image distance calibration when the hot pressing time is 400ms in Example 1.

[0045] Figure 6 for Figure 3 Strain diagram of the calibrated surface b.

[0046] Figure 7 Schematic diagram of the calibration of the slab strain measurement surface when the hot pressing time is 0 ms in Example 2.

[0047] Figure 8 This is a schematic diagram of the end face of the slab after image enhancement processing at a hot pressing time of 0 ms in Example 2.

[0048] Figure 9 This is a schematic diagram of image distance calibration when the hot pressing time is 0ms in Example 2.

[0049] Figure 10 This is a schematic diagram of image distance calibration when the hot pressing time is 200ms in Example 2.

[0050] Figure 11 This is a schematic diagram of image distance calibration when the hot pressing time is 400ms in Example 2.

[0051] Figure 12 for Figure 7 Strain diagram of the calibration surface f.

[0052] Figure 13 Flowchart of the present invention. DETAILED DESCRIPTION

[0053] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0054] Example 1:

[0055] like Figure 13 As shown, the online strain field testing method of the hot pressing process of the reconstituted bamboo slab of this embodiment includes the following steps:

[0056] (1) Slab paving: The size of a single impregnated bamboo bundle is 450mm (length) × 30mm (width) × 8mm (thickness). The slabs are assembled according to the grain and laid manually, with 5 bamboo bundles per layer, for a total of 9 layers. The final slab size is 150mm (length) × 72mm (width). The thickness of the impregnated bamboo bundle slab after laying is approximately 3 times the thickness of the final hot-pressed reconstituted bamboo.

[0057] (2) Strain observation surface calibration: The end face of the slab is used as the observation surface, and a scale ruler is arranged on the observation surface. 15 bamboo bundles (3×5 in length and width) are evenly selected as the strain observation surface. The observation surface selected from the end face of the bamboo bundle is painted red, as shown in the following example: Figure 1 As shown, the first column of observation surfaces are named a, b, c, d, e from top to bottom, the second column are named f, g, h, i, j, and the third column are named k, l, m, n, o. After the paint is completely dry, it is hot-pressed.

[0058] (3) Hot pressing process setting: Place the calibrated impregnated bamboo slab on the hot press plate, set the hot pressing temperature to 140℃, the hot pressing pressure to 4MPa, and the hot pressing time to 35min.

[0059] (4) Image acquisition: The end face of the slab with color markings is used as the identification reference surface. A CCD camera and a zoom lens are used to continuously capture images of the slab during the stamping process at a speed of 200 ms / sheet, and the end face image of the slab from the beginning to the end of the hot pressing process is recorded in real time.

[0060] (5) Image enhancement: Import the above-mentioned captured images into Image-pro plus software, use Image proplus software to measure and analyze the hot pressing process images, use the image enhancement function to adjust the contrast of the captured images to 55, use the brightness adjustment function to adjust the brightness to 58, and then use the color measurement tool to select the colored bamboo bundle strain observation surface. Select it three times in a row until all strain observation surfaces have clear boundaries with the background image, as shown in the figure. Figure 2 shown.

[0061] (6) Image data acquisition: Set the scale length in Image-Pro Plus software, enter the actual unit and apply. The reference coloring surface is: c, h, m, such as Figure 1 As shown in , the strain observation surface where the bamboo bundles located in the same row of the reconstructed bamboo slab and whose end faces are painted in the middle of the row are located is the reference strain observation surface. Figure 3 As shown, the distance between the upper boundary of the 0ms image reference painted surface c and the lower boundary of the first adjacent painted surface b in the hot pressing process is measured, b1 = 12.69mm, and the distance from the lower boundary of the painted surface above is named a1 = 29.24mm. According to this method, d1 = 18.46mm, e1 = 32.69mm are obtained respectively. The distances of other columns are measured, f1 = 11.92mm, g1 = 25.01mm, i1 = 21.15 mm, j = 32.69mm, k1 = 18.85mm, l1 = 31.54mm, n1 = 15.38mm, o1 = 27.31mm. All images obtained by the camera during the hot pressing process are processed in the same way to obtain the distance between each marked surface and the reference painted surface in the same column. For example, the distance of the first column at 200ms is b2 = 11.8mm, a2 = 23.24mm, d2 = 15.35mm, e2 = 25mm.

[0062] (7) Data analysis: Figure 3 and Figure 4 As shown, the distance measured at 0ms is subtracted from the distance at 200ms by the displacement formula (1). 12 = b1-b2 = 0.89 mm, thus obtaining the displacement Δb of the red mark during the first 200ms interval during the hot pressing process of the impregnated bamboo slab. 12 As shown in the strain calculation formula (2), the strain of the b surface during the hot pressing process from 0ms to 200ms is recorded as ε b12 , ε b12 =Δb 12 / b1=0.07, according to the above method, the displacement during the hot pressing process from 200ms to 400ms is measured and used to calculate the strain, such as Figure 5According to this method, the longitudinal strains of 12 marked surfaces in 13 displacements during the slab pressing process are obtained, thereby obtaining the strain field during hot pressing in different thickness directions, as shown in Figure 6 shown.

[0063] Δl=l1-l2 (1)

[0064]

[0065] In the above formula, l1 is the distance between the strain observation surface and the reference strain observation surface at time T1, l2 is the distance between the strain observation surface and the reference strain observation surface at time T2, T1 refers to the time before a certain time period, T2 refers to the time after a certain time period, and so on.

[0066] The present invention has lower requirements for the image acquisition device and does not require an expensive high-definition camera. By using image processing software (Image-pro plus software) to obtain the color of the image, each painted surface can be clearly obtained, thereby obtaining the displacement during the hot pressing process. The equipment cost is low and it is easy to install and maintain.

[0067] Example 2:

[0068] The method for online testing the strain field during hot pressing of a reconstituted bamboo slab according to this embodiment includes the following steps:

[0069] (1) Slab paving: The size of a single impregnated bamboo bundle is 350mm (length) × 30mm (width) × 8mm (thickness). The slabs are assembled and laid manually according to the grain, with 10 bamboo bundles per layer, for a total of 9 layers. The final slab size is 370mm (length) × 90mm (width). The thickness of the impregnated bamboo bundle slab after laying is approximately 3 times the thickness of the final hot-pressed reconstituted bamboo.

[0070] (2) Strain measurement surface calibration: The end face of the slab is used as the observation surface, and a scale ruler is arranged on the observation surface. A total of 25 bamboo bundles with a length of 5×5 are evenly selected as the strain observation surface. The end face of the bamboo bundle is spray-painted white, and the observation surface is painted red. Figure 7 As shown, the first column of observation surfaces are named a, b, c, d, e from top to bottom, the second column are f, g, h, i, j, the third column are k, l, m, n, o, the fourth column are p, q, r, s, t, and the fifth column are u, v, w, x, y. After the paint is completely dry, it is hot-pressed.

[0071] (3) Hot pressing process setting: Place the calibrated impregnated bamboo slab on the hot press plate, set the hot pressing temperature to 140℃, the hot pressing pressure to 4MPa, and the hot pressing time to 35min.

[0072] (4) Image acquisition: The end face of the slab with color markings is used as the identification reference surface. A CCD camera and a zoom lens are used to continuously capture images of the slab during the stamping process at a speed of 200 ms / sheet, and the original end face image of the slab is recorded in real time from the beginning to the end of the hot pressing process.

[0073] (5) Image enhancement: Import the above-mentioned captured images into Image-pro plus software, use Image proplus software to measure and analyze the hot pressing process images, use the image enhancement function to adjust the contrast of the captured images to 55, use the brightness adjustment function to adjust the brightness to 58, and then use the color measurement tool to select the reconstructed bamboo mark surface, and select it 5 times in a row until all the mark surfaces have clear boundaries with the image, as shown in the figure. Figure 8 shown.

[0074] (6) Image data acquisition: Set the scale length in Image-pro plus software, enter the actual unit and apply. The reference coloring surface is: a, b, c, d, e, such as Figure 7 As shown, the strain observation surface of the bamboo bundle with the outermost end surface painted on the same row as the strain observation surface of the reconstructed bamboo blank is used as the reference strain observation surface. In this embodiment, the reference strain observation surface is the column of bamboo bundles with the leftmost end surface painted on the reconstructed bamboo blank (in other embodiments, the reference strain observation surface may be the column of bamboo bundles with the rightmost end surface painted on the reconstructed bamboo blank). Figure 9 As shown, the distances between the left boundary of the reference painted surface a and the left boundary of the first painted surface f on the right of the 0ms image during the hot pressing process are measured, f1 = 85.2 mm, and the distance between the left boundary of the reference painted surface a and the left boundary of the calibration point k is named k1 = 149.2 mm. According to this method, p1 = 249.4 mm, u1 = 349.8 mm are obtained respectively. The distances of other rows are measured, g1 = 105.4 mm, l1 = 184.5 mm, q1 = 272.3 mm, v = 369.5 mm, h1 = 84.5 mm, m1 = 177.3 mm, r1 = 273.5 mm. mm, w1=359.4mm, i1=87.3mm, n1=177.6mm, s1=266.4mm, x1=351.2mm, j1=98.6mm, o1=187.9mm, t1=279.4mm, y1=355.7mm. All images obtained by the camera during the hot pressing process are processed in the same way, and the distance between the left boundary of the first column of reference painted surface and the left boundary of the second column of painted surface is obtained as f2=85.3mm, g2=106.2mm, h2=84.7mm, i2=87.5mm, j2=98.9mm.

[0075] (7) Data analysis: Figure 9 and Figure 10As shown, the distance measured at 0ms is subtracted from the distance at 200ms by the displacement formula (1). 12 = f2-f1 = 0.1 mm, thus obtaining the displacement Δf of the red mark during the first 200ms interval during the hot pressing process of the impregnated bamboo slab. 12 As shown in the strain calculation formula (2), the strain of the calibration surface f during the hot pressing process from 0ms to 200ms is recorded as ε f12 , ε f12 =Δf 12 / f1=0.00117, according to the above method, the displacement during the hot pressing process from 200ms to 400ms is measured and used to calculate the strain, such as Figure 11 The transverse strains of 20 marks in 9 displacements during the slab pressing process were obtained respectively, thereby obtaining the strain field during the hot pressing process in different width directions, as shown in FIG. Figure 12 shown.

[0076] Δl=l1-l2 (1)

[0077]

[0078] In the above formula, l1 is the distance between the strain observation surface and the reference strain observation surface at time T1, l2 is the distance between the strain observation surface and the reference strain observation surface at time T2, T1 refers to the time before a certain time period, T2 refers to the time after a certain time period, and so on.

[0079] Example 3

[0080] As a general inventive concept, the present invention provides an online testing device for strain field during hot pressing of reconstituted bamboo slabs, comprising the following modules:

[0081] An image processing module is used to obtain end surface images of the reconstituted bamboo slab at different times during the hot pressing process;

[0082] An image recognition module is used to respectively identify the painted end faces of the bamboo bundles in each end face image as strain observation faces;

[0083] A first calculation module is used to calculate the distance between each strain observation surface and a specified reference strain observation surface;

[0084] The second calculation module is used to calculate the strain amount ε of each strain observation surface based on the change in the distance between each strain observation surface and the specified reference strain observation surface in the end face image, thereby obtaining the hot pressing process strain field composed of the strain amount ε of each strain observation surface during the hot pressing process.

[0085] Example 4

[0086] As a general inventive concept, the present invention provides an online testing device for the strain field during the hot pressing process of reconstituted bamboo slabs. The device includes a memory and a processor. The memory stores a computer program. When the computer program is executed by the processor, all or part of the steps of the online testing method for the strain field during the hot pressing process of reconstituted bamboo slabs of the aforementioned embodiments are implemented.

[0087] Example 5

[0088] As a general inventive concept, the present invention provides a storage medium on which a computer program is stored, which can be executed by one or more processors to implement all or part of the steps of the online testing method of the strain field during the hot pressing process of the reconstituted bamboo slab in the aforementioned embodiments.

[0089] Storage media, such as flash memory, hard disk, multimedia card, card-type memory (for example, SD or DX memory), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), magnetic storage, disk, optical disk, server, App application store, etc.

[0090] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of processes and / or boxes in the flowchart and / or block diagram, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the functions described in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including the instruction device, which implements the function specified in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0091] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Any person skilled in the art can utilize the methods and techniques disclosed above to make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments with equivalent variations, without departing from the spirit and technical solutions of the present invention.

Claims

1. A method for online testing of strain field during hot pressing of reconstituted bamboo slabs, characterized by: The following steps are involved: S1, obtaining end surface images of the reconstituted bamboo slab at different times during the hot pressing process; S2, respectively identifying the painted end faces of the bamboo bundles in each end face image as the strain observation faces; S3, respectively calculating the distance between each strain observation surface and the specified reference strain observation surface; S4, calculating the strain of each strain observation surface based on the change in the distance between each strain observation surface in the end face image and the specified reference strain observation surface ε , thus obtaining the strain of each strain observation surface during the hot pressing process ε The strain field of the hot pressing process; In step S2, the reconstituted bamboo slab is a multi-layer structure formed by paving multiple bamboo bundles, and the bamboo bundles with painted ends are arranged in rows and columns along the transverse and longitudinal ends of the reconstituted bamboo slab; In step S2, in each column of bamboo bundles of the reconstructed bamboo slab, the number of bamboo bundles with painted end surfaces is 3 to 6, and in each row of bamboo bundles, the number of bamboo bundles with painted end surfaces is 3 to 6; In step S3, the designated reference strain observation surface corresponding to each strain observation surface is specifically one of the following definitions: Definition 1: The strain observation surface is located in the same row of the reconstituted bamboo slab as the strain observation surface and the bamboo bundle with the end surface painted in the middle of the row is located there; Definition 2: The strain observation surface of the bamboo bundle that is located in the same row as the reconstituted bamboo slab and whose outermost end surface is painted.

2. The method for online strain field testing during hot pressing of reconstituted bamboo slabs according to claim 1, characterized in that: In step S2, identifying the painted bamboo bundle end faces in each end face image includes: adjusting the contrast and brightness of the end face image, and adjusting the color sampling value based on the color of the painted bamboo bundle end faces so that all the painted bamboo bundle end faces have clear boundaries with the background color.

3. The method for online strain field testing during hot pressing of reconstituted bamboo slabs according to claim 1, characterized in that: When the reference strain observation surface is the strain observation surface of the bamboo bundle located in the same row as the reconstituted bamboo slab and having the colored end surface in the middle of the row, step S3 includes the following steps: C1. The strain observation surface where the bamboo bundles are located at the end of the middle row of the reconstructed bamboo slabs painted with color is designated as the reference strain observation surface; C2. Measure the distance between the strain observation surface and the reference strain observation surface in the same column of the end face image at adjacent moments and calculate the distance change l ; C3. Change the spacing l Divide by the distance between the strain observation surface and the reference strain observation surface in the end face image at the previous moment l , and get the dependent variable ε, Thus, the strain of each strain observation surface during the hot pressing process is obtained ε The strain field of the hot pressing process; When the reference strain observation surface is the strain observation surface of the bamboo bundle located in the same row as the reconstituted bamboo slab and having the outermost end surface painted, step S3 includes the following steps: D1. The strain observation surface where the outermost bamboo bundle of the reconstructed bamboo slab is located is designated as the reference strain observation surface; D2. Measure the distance between the strain observation surface and the reference strain observation surface in the same row of the end face image at adjacent moments and calculate the distance change l ; D3, change the spacing l Divide by the distance between the strain observation surface and the reference strain observation surface in the end face image at the previous moment l , and get the dependent variable ε, Thus, the strain of each strain observation surface during the hot pressing process is obtained ε The strain field of the hot pressing process.

4. The method for online strain field testing during hot pressing of reconstituted bamboo slabs according to claim 3, characterized in that: When the reference strain observation surface is a strain observation surface located in the same column as the reconstituted bamboo slab and having a colored end surface in the middle of the column where the bamboo bundle is located, in step C2, when the strain observation surface is located above the reference strain observation surface, the distance between the upper boundary of the reference strain observation surface and the lower boundary of the strain observation surface is defined as the spacing between the strain observation surface and the reference strain observation surface; When the strain observation surface is located below the reference strain observation surface, the distance between the lower boundary of the reference strain observation surface and the upper boundary of the strain observation surface is the distance between the strain observation surface and the reference strain observation surface; When the reference strain observation surface is the strain observation surface located in the same row as the reconstituted bamboo slab and having the outermost end surface of the bamboo bundle painted, in step D2, when the strain observation surface is located to the left of the reference strain observation surface, the distance between the right boundary of the reference strain observation surface and the left boundary of the strain observation surface is used as the spacing between the strain observation surface and the reference strain observation surface; When the strain observation surface is located on the right side of the reference strain observation surface, the distance between the left boundary of the reference strain observation surface and the right boundary of the strain observation surface is the spacing between the strain observation surface and the reference strain observation surface.

5. An online testing device for strain field during hot pressing of a reconstituted bamboo slab for implementing the online testing method for strain field during hot pressing of a reconstituted bamboo slab according to any one of claims 1 to 3, characterized in that: Includes the following modules: An image processing module is used to obtain end surface images of the reconstituted bamboo slab at different times during the hot pressing process; An image recognition module is used to respectively identify the painted end faces of the bamboo bundles in each end face image as strain observation faces; A first calculation module is used to calculate the distance between each strain observation surface and a specified reference strain observation surface; The second calculation module is used to calculate the strain of each strain observation surface based on the change in the distance between each strain observation surface and the specified reference strain observation surface in the end face image. ε , thus obtaining the strain of each strain observation surface during the hot pressing process ε The strain field of the hot pressing process.

6. An online testing device for strain field during hot pressing of reconstituted bamboo slabs, characterized in that: The device includes a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the online testing method for strain field during hot pressing of reconstituted bamboo slabs according to any one of claims 1 to 3 is implemented.

7. A storage medium having a computer program stored thereon, characterized in that: The computer program can be executed by one or more processors to implement the online strain field testing method during hot pressing of reconstituted bamboo slabs according to any one of claims 1 to 3.

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