A laminated dowel and method of making the same

Abstract

The present application relates to the technical field of green building materials, in particular to a kind of layerboard pin joint wood and its preparation method.Layerboard pin joint wood is made of two or more than two layerboards stacked and connected by memory recovery wood pin, and the layerboard and memory recovery wood pin use the same tree species wood or tree species wood with similar physical and mechanical properties.Layerboard pin joint wood is prepared by memory recovery wood pin made by low-temperature hydrothermal compression wood, including preheating, pressure application, preliminary shaping, deformation fixation and wood pin preparation steps, which can solve the problem of inconsistent deformation coordination between wood pin and layerboard in long-term use of layerboard pin joint wood, and ensure the bearing performance and long-term safe application of layerboard pin joint wood.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of green building materials, in particular to a laminated dowel timber and a preparation method thereof. BACKGROUND

[0002] Glued timber is an engineered wood product formed by structural adhesive and laminated pressure gluing, and is one of the most important structural materials in modern wood structure in China. However, the adhesive used in glued timber is generally polyurethane, isocyanate, phenolic resin, etc., which will release harmful chemicals during the production and use of glued timber, endangering the health of producers and users, and the subsequent recycling cost is high. In addition, the adhesive is easily affected by environmental humidity and temperature, and has durability problems.

[0003] Dowel laminated timber (DLT) is a glue-free and nail-free, pure solid wood engineered wood product composed of only wood dowels and laminates, which can be used to replace glued timber. In traditional timber structure buildings in China, dowel laminated timber is often used as spliced columns and spliced beams, etc. The wood dowels are generally made of hard hardwood, and the laminates are generally made of pine, larch and other coniferous wood. However, due to the scarcity of domestic hard hardwood resources, the wood dowels and laminates are currently manufactured based on the same tree species or tree species with similar physical and mechanical properties to meet the load-bearing requirements of dowel laminated timber used in different components. In addition, due to the significant difference in the physical and mechanical properties of the wood used for wood dowels and laminates in traditional dowel laminated timber, the deformation coordination is inconsistent during long-term use, which may cause the wood dowels to loosen or even fall off, seriously affecting the load-bearing safety performance of dowel laminated timber.

[0004] To solve the problems faced by traditional dowel laminated timber, modern dowel laminated timber manufacturing technology has begun to try to use compressed wood prepared by hydrothermal method, steam treatment method, high-frequency heating method, microwave heating method and chemical method to manufacture wood dowels, and the wood used for wood dowels is generally the same tree species as the wood used for laminates, which can be used for beams, walls and floors, etc. However, the above methods involve high-temperature heat treatment above 140℃ in the process of manufacturing compressed wood, and when the temperature of wood exceeds 140℃, the main chemical component of wood, hemicellulose, begins to decompose. In addition, the chemical method will decompose lignin and hemicellulose in wood. These methods of using compressed wood to prepare wood dowels result in changes in the main chemical components of wood, the wood loses its memory recovery of deformation, the physical and mechanical properties of the wood used for wood dowels and laminates are significantly different, and the deformation coordination of the wood dowels and laminates is inconsistent during long-term use, which may cause the wood dowels to loosen or even fall off.

[0005] The Chinese invention patent application "A wood nail jointed glued wood and its preparation method and application" (CN202210247233.6), "A wood nail jointed orthogonal glued wood and its preparation method" (CN202111608090.9), "A manufacturing method of wood nail welded laminated timber floor assembly" (CN201910595658.4), "A method for fixing deformation of compressed wood" (CN201710441897.5), and the compressed wood and its wood pin products involved in the papers "Research on mechanical properties of compressed wood pin connection" and "Research on uplift resistance of compressed wood pin rotary friction welding" of Dalian University of Technology, all do not solve the problem of loss of deformation memory recovery of compressed wood, leading to the problem of inconsistent deformation coordination between wood pins and laminated boards during long-term use of laminated pin jointed wood, which poses a safety hazard to the bearing capacity and limits its practical application in the market.

[0006] From the above literature disclosure, it can be seen that there is still a lack of corresponding technology for laminated pin jointed wood and its preparation method, which cannot meet the needs of manufacturing and safe use in the field. SUMMARY

[0007] The present application aims to provide a laminated pin jointed wood and its preparation method, which uses compressed wood under the action of low-temperature hydrothermal and long-term pressure viscoelastic deformation to prepare memory recovery wood pins, solves the problem of inconsistent deformation coordination between wood pins and laminated boards during long-term use of laminated pin jointed wood, and guarantees the bearing capacity and long-term safe application of laminated pin jointed wood. At the same time, the laminated pin jointed wood provided by the present application is a pure solid wood engineering product, which can simultaneously have good bearing capacity, stiffness and ductility, and can be used to replace glued wood.

[0008] Specifically, the present application provides the following technical solutions:

[0009] A laminated pin jointed wood is made of two or more layers of laminated boards connected by at least one memory recovery wood pin, the laminated boards are provided with through holes for inserting the memory recovery wood pin, the laminated boards and the memory recovery wood pin are made of wood of the same species or wood of similar physical and mechanical properties, and the memory recovery wood pin is prepared by low-temperature hydrothermal compression of wood.

[0010] The density of the memory recovery wood pin ranges from 0.5 to 1.3 g / cm 3 , which is 1.5 to 3 times the density of the laminated board.

[0011] The shape of the memory recovery wood pin can be circular, square or polygonal, and the side length D ranges from 10 to 100 mm.

[0012] The number of memory recovery wood pins can be controlled according to n = w / 150, where n is the number of memory recovery wood pins, and w is the width of the laminated board.

[0013] When the force bearing surface of the laminated pin-jointed wood is the wide surface xz of the laminated board, it can be used as a beam component; when the force bearing surface of the laminated pin-jointed wood is the narrow surface xy of the laminated board, it can be used as a floor component; and when the force bearing surface of the laminated pin-jointed wood is the end surface yz of the laminated board, it can be used as a column component.

[0014] A laminated pin-jointed wood preparation method, comprising the following steps:

[0015] (1) preparing a memory recovery wood pin for connecting laminated boards by a compression device; specifically comprising:

[0016] (1-1) preheating; placing wood into a hot press, preheating by upper and lower pads, and heating the core temperature of the wood to 70-140℃;

[0017] (1-2) applying pressure; applying pressure to the upper pad by the hot press to compress the wood in the cross grain, the compression speed being 1-10 mm / min, and the hot press being kept in place for 0.5-3 min after each compression of 3-8 mm;

[0018] (1-3) preliminary shaping; controlling the final compression amount of the wood by a thickness gauge, and stopping the compression of the hot press when the upper pad contacts the thickness gauge, and immediately anchoring and fixing the upper pad by a bolt and a screw rod, and unloading and stopping the heating of the hot press after the bolt is anchored to the predetermined position, and completing the preliminary shaping of the wood;

[0019] (1-4) deformation fixation; cooling the wood after the preliminary shaping to 50℃, placing the preliminarily shaped wood into a conventional drying box under the pressure applied by the upper pad, and performing low-temperature heat treatment at 60-100℃ to make the moisture content of the wood less than 5%, and then naturally cooling the wood to about normal temperature 20℃, and placing the wood into a normal temperature environment for 2-7 days for health maintenance;

[0020] repeating the above steps of low-temperature heat treatment, cooling and health maintenance for 3-7 times to complete the compression deformation fixation of the wood;

[0021] (1-5) wood pin preparation; unloading the pressure on the upper pad by loosening the bolt, taking out the wood fixed by compression deformation, and processing the wood pin by a milling machine to prepare the memory recovery wood pin.

[0022] (2) preparing a laminated board; specifically comprising:

[0023] planing the four surfaces of the laminated board, and laminating and assembling the laminated board in the thickness direction of the laminated board, and fixing by a clamping device.

[0024] (3) connecting and assembling; specifically comprising:

[0025] (3-1) The fixed laminated board is drilled;

[0026] (3-2) The memory recovery wood pin is vertically nailed into the drilled hole of the laminated board to obtain a laminated board pin joint wood, and the laminated board pin joint wood is placed in a normal temperature environment for 7-10 days.

[0027] The wood in the step (1-1) can be green wood or wood with a moisture content exceeding the fiber saturation point.

[0028] The compression rate of the preliminary shaping of the wood in the step (1-3) can be controlled according to δ=aε, wherein δ is the compression rate of the preliminary shaping of the wood, a is an adjustment coefficient with a value range of 0.8-0.95, and ε is the hardening point strain value of the wood.

[0029] The moisture content of the laminated board in the step (2) is 5%-10% higher than that of the memory recovery wood pin.

[0030] The diameter of the laminated board drilled hole in the step (3-1) is 0-0.5 mm smaller than that of the memory recovery wood pin.

[0031] Compared with the prior art, the laminated board pin joint wood and the preparation method thereof have at least the following beneficial effects:

[0032] The present application creatively proposes to prepare the wood pin by the compression wood under the action of low-temperature hydrothermal and long-term pressure viscoelastic deformation, and the wood pin retains the deformation memory recovery because the main chemical components of the wood do not change, which can significantly improve the ability of the wood pin and the laminated board to be consistent in deformation during long-term use; the preparation method of the laminated board pin joint wood proposed by the present application has simple preparation equipment, low energy consumption, no pollution, and can significantly reduce the manufacturing cost of the laminated board pin joint wood.

[0033] The laminated board pin joint wood and the preparation method thereof will be further described below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of the laminated board pin joint wood of the present application.

[0035] Figure 2 It is a shape schematic diagram of the memory recovery wood pin in the laminated board pin joint wood of the present application.

[0036] Figure 3 It is a structural schematic diagram of the compression device for preparing the memory recovery wood pin in the preparation process of the laminated board pin joint wood of the present application.

[0037] Figure 4 It is a selection diagram of the compression rate of the preliminary shaping of the wood for preparing the memory recovery wood pin in the preparation process of the laminated board pin joint wood of the present application.

[0038] Figure 5 Schematic diagram of the pull-out test device for wooden pins in the examples and comparative examples.

[0039] Among them, 10-layer board, 20-memory recovery wooden pins, 30-pressure clamp;

[0040] 1-bolt, 2-upper spacer, 3-wood, 4-thickness gauge, 5-lower spacer, 6-screw. DETAILED DESCRIPTION

[0041] The following is combined with Figures 1-5 The present invention will be further described.

[0042] A type of veneer pinned wood, such as Figure 1 As shown, the laminated pinned timber is made of two or more laminated layers 10 connected by nine memory-recovery pins 20. The laminates 10 are provided with through-holes for inserting the memory-recovery pins 20. The laminates 10 and the memory-recovery pins 20 are made of the same wood species or wood species with similar physical and mechanical properties. The memory-recovery pins 20 are made by low-temperature hydrothermal compression of the wood. In other advantageous embodiments, the number of memory-recovery pins 20 can be increased or decreased according to actual needs.

[0043] The density of the memory recovery wooden pin 20 is in the range of 0.5 to 1.3 g / cm 3 , which is 1.5 to 3 times the density of the layer board 10.

[0044] The shape of the memory restorative wooden pin 20 can be circular, square and polygonal (such as regular octagon), such as Figure 2 As shown, the side length D ranges from 10 to 100 mm.

[0045] The number of arrangement of the memory restorative wooden pins 20 can be controlled according to n=w / 150, where n is the number of arrangement of the memory restorative wooden pins, and w is the width of the layer board.

[0046] When the load-bearing surface of the pin-jointed timber layer is the wide xz surface of the layer, it can be used as a beam component. When the load-bearing surface of the pin-jointed timber layer is the narrow xy surface of the layer, it can be used as a floor component. When the load-bearing surface of the pin-jointed timber layer is the end yz surface of the layer, it can be used as a column component.

[0047] A method for preparing veneer pin-jointed wood comprises the following steps:

[0048] (1) Using a compression device to make memory recovery wood pins for connecting laminates, such as Figure 3 As shown; specifically including:

[0049] (1-1) Preheating; put the wood 3 into the hot press, preheat through the upper pad 2 and the lower pad 5, heat the core temperature of the wood 3 to 70-140℃;

[0050] (1-2) Pressing; apply pressure to the upper pad 2 through the hot press, compress the wood 3 in the cross-grain direction, the compression speed is 1-10mm / min, the hot press remains in place for 0.5-3min after each compression of 3-8mm;

[0051] (1-3) Preliminary shaping; control the final compression amount of the wood 3 with the thickness gauge 4, when the upper pad 2 contacts the thickness gauge 4, the hot press stops compression, immediately anchor the upper pad 2 through the bolt 1 and the screw rod 6, after the bolt 1 is anchored to the predetermined position, the hot press unloads and stops heating, complete the preliminary shaping of the wood;

[0052] (1-4) Deformation fixation; after the wood 3 is cooled to 50℃ after the preliminary shaping, put the preliminarily shaped wood 3 into the conventional drying box under the pressure of the upper pad 2, low-temperature heat treatment is adopted at 60-100℃ to make the moisture content of the wood 3 less than 5%, then naturally cool the wood 3 to about normal temperature 20℃, and then place it in the normal temperature environment for 2-7 days for curing;

[0053] After the wood 3 is cured, it is placed into the conventional drying box, and the above steps of low-temperature heat treatment, cooling, and curing are repeated for 3-7 times to complete the compression deformation fixation of the wood;

[0054] (1-5) Wood pin preparation; release the pressure on the upper pad 2 by loosening the bolt 1, take out the wood that has been compressed and deformed and fixed, process the wood pin with a milling machine to prepare a memory recovery wood pin.

[0055] (2) Preparation of a plywood; specifically comprising:

[0056] Plane the four sides of the plywood 20, stack the plywood in the thickness direction, and fix it with a clamping device.

[0057] (3) Connection and assembly; specifically comprising:

[0058] (3-1) Drill holes in the plywood 20 after stacking and fixing;

[0059] (3-2) vertically nail the memory recovery wood pin 10 prepared above into the hole of the plywood 20 to prepare a plywood pinned wood, and then place the plywood pinned wood in a normal temperature environment for 7-10 days for curing.

[0060] The wood in step (1-1) can be green wood or wood with a moisture content exceeding the fiber saturation point.

[0061] The compression ratio of the preliminary shaping of the wood in the step (1-3) can be controlled according to δ=aε, where δ is the compression ratio of the preliminary shaping of the wood, a is an adjustment coefficient, and ε is the strain value of the hardening point of the wood. Figure 4

[0062] The moisture content of the layer in the step (2) is 5% to 10% greater than that of the memory recovery wood pin.

[0063] The diameter of the layer opening in the step (3-1) is 0 to 0.5 mm smaller than that of the memory recovery wood pin.

[0064] Example 1

[0065] A layer pin joint wood, as shown in Figure 1 , is made of six layers of fir layer boards and connected by nine memory recovery wood pins, the memory recovery wood pins are made of low-temperature hydrothermal compression fir, and the size of the fir layer board is 35 mm (thickness) x 150 mm (width) x 4000 mm (length).

[0066] The average density of the layer is 0.41 g / cm 3 , and the density of the memory recovery wood pin is not less than 0.80 g / cm 3 .

[0067] The shape of the memory recovery wood pin is circular, as shown in the left figure of Figure 2 , and the side length D is 30 mm.

[0068] The number of the memory recovery wood pin arrangement is one row, which is arranged in the middle position of the layer width, and the pin spacing is 200 mm.

[0069] The force surface of the layer pin joint wood is the wide surface xz of the layer, which is used as a beam member.

[0070] The preparation method of the layer pin joint wood comprises the following steps:

[0071] (1) The memory recovery wood pin for connecting the fir layer board is prepared by a compression device, as shown in Figure 3 ; specifically comprising:

[0072] (1-1) Preheating; the fir wood 3 with moisture content exceeding the fiber saturation point is put into the hot press, and preheating is performed by the upper pad 2 and the lower pad 5, so that the core temperature of the fir wood is heated to 100℃, and the size of the fir wood 3 is 100 mm (thickness) x 200 mm (width) x 500 mm (length);

[0073] ​(1-2) Pressing: applying pressure to the upper pad 2 by the hot press to compress the fir wood 3 transversely at a compression rate of 5 mm / min. The hot press remains in place for 1 minute for every 5 mm of compression;

[0074] (1-3) Preliminary shaping: According to the compression stress-strain curve of Chinese fir wood, the strain value at the hardening point of Chinese fir wood is greater than 60%, such as Figure 4 As shown, a thickness gauge 4 is used to control the final compression amount of the fir wood 3. The thickness gauge height is 45 mm. When the upper pad 2 contacts the thickness gauge 4, the hot press stops compression and immediately anchors the upper pad 2 with the bolt 1 and the screw 6. After the bolt 1 is anchored to the predetermined position, the hot press is unloaded and the heating is stopped, completing the preliminary shaping of the fir wood 3.

[0075] (1-4) Deformation and Fixation: After the preliminarily shaped fir wood is cooled to 50° C., the preliminarily shaped fir wood is placed in a conventional drying oven while maintaining the pressure exerted by the upper pad 2 on the fir wood. The preliminarily shaped fir wood is subjected to a low-temperature heat treatment at 80° C. to reduce the moisture content of the fir wood to less than 5%. The fir wood is then naturally cooled to a room temperature of about 20° C. and then placed in a room temperature environment for curing for 2-7 days.

[0076] The cured Chinese fir wood is then placed in a conventional drying oven and the above steps of low-temperature heat treatment, cooling, and curing are repeated 5 times to complete the compression deformation fixation of the Chinese fir wood;

[0077] (1-5) Preparation of wooden pins: The upper pad 2 is unscrewed by loosening the bolt 1 to relieve pressure, and the compressed and deformed fir wood is taken out and processed into a memory-restorative wooden pin with a diameter of 30 mm using a milling machine. The moisture content of the memory-restorative wooden pin is 5%.

[0078] (2) Preparation of fir veneer; specifically including:

[0079] The four sides of the fir veneer are planed. The size of each fir veneer is 35mm (thickness) × 150mm (width) × 4000mm (length). Six fir veneers are stacked and assembled along the thickness direction of the board and fixed with a clamping device. The moisture content of the fir veneer is 15%.

[0080] (3) Connection and assembly; specifically including:

[0081] (3-1) Drilling holes in the assembled and fixed laminates, with a diameter of 29.5 mm;

[0082] (3-2) The memory recovery wood pins prepared above are vertically nailed into the openings of the layer boards to prepare layer board pin-jointed wood, and the layer board pin-jointed wood is then placed in a room temperature environment for curing for 7 to 10 days.

[0083] Comparative Example 1

[0084] The Chinese fir plywood was prepared according to Example 1, except that the plywood was connected directly using a structural polyurethane adhesive.

[0085] Comparative Example 2

[0086] The Chinese fir plywood was prepared according to Example 1, except that in the process of preparing the dowel, the dowel was directly prepared using air-dried elm wood, and the wood was not subjected to any heat treatment or chemical treatment. The density of the dowel was 0.72 g / cm 3 , and the moisture content was 15%.

[0087] Comparative Example 3

[0088] The Chinese fir plywood was prepared according to Example 1, except that in the process of preparing the dowel, the core temperature of the Chinese fir wood was heated to 140°C by preheating, and the deformation fixation was performed by directly high-temperature hot pressing at 180°C for 2 h.

[0089] The beam members with a size of 210 mm (height) x 150 mm (width) x 4000 mm (length) were prepared according to the above examples and comparative examples, and the beam bending test was performed according to GB / T 50329-2012 “Standard for Test Methods of Timber Structures”, to obtain the bending strength, bending stiffness and ductility coefficient of the beam members. In addition, the plywood glued wood prepared in the above examples and comparative examples was sawn into anti-pull test pieces with a size of 35 (thickness) x 150 mm (width) x 150 mm (length), and the dowel was located at the center of the anti-pull test piece. The anti-pull test of the dowel was carried out in a normal temperature environment (temperature of 20±2°C, humidity of 65±5%) and in a cyclic temperature and humidity environment (firstly maintained in an environment with a temperature of 20°C and a humidity of 90% for 30 days, then dried in a dry box at 103°C for 48 h, and the cycle was repeated for 10 times), as shown in Table 1. The statistical results of the mechanical properties of the beam members and the dowel anti-pull are shown in Table 1. Figure 5

[0090] ​The results show that the wood dowel according to the wood dowel and the preparation method thereof has good anti-pulling bearing capacity at normal temperature and in a cyclic temperature and humidity environment, that is, the wood dowel and the plywood can be consistent in deformation during long-term use. In addition, the wood dowel according to the wood dowel and the preparation method thereof has the best ductility coefficient, and the bending strength and the bending stiffness are only slightly lower than those of the glued wood beam component. The wood dowel is prepared by compressing wood under the action of low-temperature hydrothermal and long-term pressure viscoelastic deformation, and the wood dowel retains the deformation memory recovery of the wood material due to no change in the main chemical components of the wood, thereby significantly improving the ability of the wood dowel and the plywood to be consistent in deformation during long-term use. The preparation method of the wood dowel is simple in equipment, low in energy consumption, pollution-free, and can significantly reduce the manufacturing cost of the wood dowel.

[0091] Table 1 statistical results of the mechanical properties of the bending component and the wood dowel

[0092]

[0093] In summary, the wood dowel and the preparation method thereof are provided, the memory recovery of the wood dowel is retained, the deformation of the wood dowel and the plywood is consistent, the bearing performance of the wood dowel and the long-term safe application are ensured, which is of great significance for promoting the high value-added application of the artificial forest wood mainly used as structural material in the wood structure, and promoting the establishment of the wood structure system with independent intellectual property rights in China.

[0094] The above-described embodiments are merely preferred embodiments of the present application, and are not intended to limit the scope of the present application. Various modifications and improvements to the technical solutions of the present application made by those of ordinary skill in the art without departing from the design spirit of the present application shall fall within the scope of protection of the present application as defined by the claims.

Claims

1. A method for preparing veneer pin-jointed wood, characterized by: The laminate pin-jointed wood is made of two or more laminates (10) stacked and connected by at least one memory-restorative wood pin (20), the laminates (10) are provided with through holes for inserting the memory-restorative wood pin (20), the laminates and the memory-restorative wood pin are made of the same species of wood or wood of similar physical and mechanical properties, and the memory-restorative wood pin (20) is made by low-temperature hydrothermal compression of wood; The preparation method comprises the following steps: (1) A memory recovery wooden pin (20) for connecting laminates (10) is produced by a compression device; specifically comprising: (1-1) Preheating: Place the wood (3) in a hot press and preheat it with the upper pad (2) and the lower pad (5) to heat the wood core to a temperature of 70-140°C; (1-2) applying pressure: applying pressure to the upper pad (2) by the hot press to compress the wood (3) transversely at a compression speed of 1 to 10 mm / min. The hot press remains in place for 0.5 to 3 minutes for every 3 to 8 mm of compression; (1-3) Preliminary shaping: A thickness gauge (4) is used to control the final compression amount of the wood. When the upper pad (2) contacts the thickness gauge (4), the hot press stops compression and immediately anchors the upper pad (2) through the bolt (1) and the screw (6). After the bolt (1) is anchored to the predetermined position, the hot press is unloaded and the heating is stopped, completing the preliminary shaping of the wood (3); (1-4) Deformation and fixation: After the wood (3) is initially shaped and cooled to 50°C, the wood (3) is placed in a conventional drying oven while the upper pad (2) is kept pressing the wood (3) and subjected to low-temperature heat treatment at 60-100°C to reduce the moisture content of the wood (3) to less than 5%. The wood (3) is then naturally cooled to a room temperature of about 20°C and then placed in a room temperature environment for curing for 2-7 days. The cured wood (3) is then placed in a conventional drying oven, and the above low-temperature heat treatment, cooling, and curing steps are repeated 3-7 times to complete the compression deformation and fixation of the wood (3); (1-5) Preparation of wooden pins: loosening the bolts (1) to release the pressure on the upper pad (2), taking out the compressed and deformed wood (3), and processing the wooden pins with a milling machine to obtain memory-restorative wooden pins; (2) Preparation of laminates; specifically including: Plane the four sides of the veneer, stack and assemble the veneer along the thickness direction, and fix them with a clamping device; (3) Connection and assembly; specifically including: (3-1) drilling holes in the assembled and fixed layers; (3-2) The prepared memory recovery wood pins are vertically nailed into the openings of the layer boards to prepare layer board pin-jointed wood, and the layer board pin-jointed wood is then placed in a room temperature environment for curing for 7 to 10 days.

2. The method for preparing veneer pin-jointed wood according to claim 1, characterized in that: The wood in the step (1-1) is green wood or wood with a moisture content exceeding the fiber saturation point.

3. The method for preparing veneer pin-jointed wood according to claim 1, characterized in that: The compression rate of the initial shaping of the wood in the steps (1-3) is based on δ = aε To control, δ The compression rate for the initial shaping of the wood, a is the adjustment coefficient, and its value range is 0.8~0.

95. ε is the strain value at the hardening point of wood.

4. The method for preparing veneer pin-jointed wood according to claim 1, characterized in that: The moisture content of the middle layer board in step (2) is 5% to 10% greater than the moisture content of the memory-restorative wood pin.

5. The method for preparing veneer pin-jointed wood according to claim 1, characterized in that: The diameter of the hole in the middle layer board in the step (3-1) is 0-0.5 mm smaller than the diameter of the memory restorative wooden pin.

6. The method for preparing veneer pin-jointed wood according to claim 1, characterized in that: The density of the memory recovery wooden pin (20) is in the range of 0.5 to 1.3 g / cm 3 , which is 1.5 to 3 times the density of the layer plate (10).

7. The method for preparing veneer pin-jointed wood according to claim 1, characterized in that: The shape of the memory restorative wooden pin (20) is circular or polygonal. When the shape is polygonal, the side length D The range is 10~100mm.

8. The method for preparing veneer pin-jointed wood according to claim 1, characterized in that: The number of arrangement of the memory restorative wooden pins (20) is as follows: n = w / 150 to control, n To set the number of arrangement of the memory restorative wooden pins, w is the width of the layer.

9. The method for preparing veneer pin-jointed wood according to claim 1, characterized in that: The stress-bearing surface of the veneer pin-jointed wood is the wide side of the veneer xz When the surface is not smooth, it is used for beam components; the stress surface of the layer pin joint wood is the narrow surface of the layer xy When the surface is not smooth, it is used for floor components; the load-bearing surface of the layer pin joint wood is the end face of the layer yz When the surface is large, it is used for column components.

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