CN110991113B - Design method of lightweight double-layer structure of palm mattress - Google Patents
Design method of lightweight double-layer structure of palm mattress Download PDFInfo
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Abstract
The invention discloses a design method of a lightweight double-layer structure of a palm mattress. The method comprises the steps of designing a palm mattress into an upper mattress layer and a lower mattress layer, establishing a palm mattress model, carrying out stress deformation analysis on the palm mattress model after applying a human body load, measuring the deflection values of the upper mattress layer and the lower mattress layer in the palm mattress model, and setting the density of each mattress layer according to the deflection values of the upper mattress layer and the lower mattress layer to obtain the lightweight double-layer structure of the palm mattress. The method can guide the lightweight structural design of the palm mattress, design the palm mattress into an upper mattress layer structure and a lower mattress layer structure, and respectively design the densities of the upper mattress layer and the lower mattress layer, so that the lightweight of the mattress is realized. Through the design of the invention, the total density of the palm mattress can be reduced, the material consumption of the mattress is saved, the production cost is reduced, and the quality of the product can be ensured.
Description
Technical Field
The invention relates to the field of palm mattress design, in particular to a design method of a lightweight double-layer structure of a palm mattress.
Background
The palm mattress is made of palm fiber, coconut shell and the like, and belongs to plant fiber elastic materials. CN90100464.2 discloses a method for producing plant fiber elastic material, which can be used for producing palm mattress, palm fibers (palm fibers) are curled and blown into a three-dimensional distribution by air flow, glue is sprayed, the palm fibers are bonded by joints to obtain palm fiber elastic sheets, then the palm fiber elastic sheets are stacked to obtain a layered palm fiber elastic material, and the palm fiber elastic material is bonded by adding latex, pressed into a sheet, hot-pressed, shaped, vulcanized and the like to produce the palm mattress.
From the research situation of the mattress made of the plant fiber elastic material at home and abroad at present, most of researchers of the mattress are based on the comfort of the mattress and try to establish the incidence relation between the human body and the design of the mattress. The researches are based on functional requirements, few researches are carried out on the relation between the structure of the mattress and the cost, the product is judged based on empirical values during development due to no scientific theoretical guidance, and the structure of the mattress is not optimally designed in many cases.
In order to meet the durable use index of the mattress, the palm fiber mattress is generally made by superposing palm fiber sheet materials as much as possible at present, and the safe use coefficient is enlarged. This in fact results in an excess of material being used for the coir mattress, which increases the production costs of the coir mattress. Therefore, there is a need for a design method that optimizes the structure of a coir mattress.
Disclosure of Invention
The invention aims to provide a design method of a lightweight double-layer structure of a palm mattress. The method can guide the lightweight structural design of the palm mattress, design the palm mattress into an upper mattress layer structure and a lower mattress layer structure, and respectively design the densities of the upper mattress layer and the lower mattress layer, so that the lightweight of the mattress is realized. By the design of the invention, the total density of the palm mattress can be reduced, the material consumption of the mattress can be saved, the production cost can be reduced, and the quality of the product can be ensured.
The technical scheme of the invention is as follows: a design method of a lightweight double-layer structure of a palm mattress comprises the steps of designing the palm mattress into an upper mattress layer and a lower mattress layer, establishing a palm mattress model, carrying out stress deformation analysis on the palm mattress model after applying human body load, measuring the deflection values of the upper mattress layer and the lower mattress layer in the palm mattress model, and setting the density of each mattress layer according to the deflection values of the upper mattress layer and the lower mattress layer to obtain the lightweight double-layer structure of the palm mattress.
In the design method of the lightweight double-layer structure of the palm mattress, the method for establishing the palm mattress model and performing stress deformation analysis on the palm mattress model after applying the human body load is preferably to establish a material model and a mattress model by using ANSYS software and apply the human body load. Firstly establishing a material model of the mattress, then setting the size of the mattress by adopting a finite element solution method, establishing the mattress model by using the material model, applying human body load on the mattress model, and carrying out stress deformation test on the mattress model after applying the human body load to obtain a corresponding deflection value; the mattress has the size of 2000mm in length, 1000mm in width and 120mm in thickness; the weight of the human body load is 80kg, and the area is 1700mm multiplied by 400mm; the finite element method is a method for solving a numerical solution of a specific problem, a structural part of a structure is firstly cut into a plurality of units, the behavior of each unit is described, then the units are connected by nodes again, and a group of simultaneous algebraic equations is generated in the process.
In the design method of the lightweight double-layer structure of the palm mattress, the thickness of the lower mattress layer is 1-4 times that of the upper mattress layer.
In the design method of the lightweight double-layer structure of the palm mattress, the thickness of the lower mattress layer is 1-3 times of that of the upper mattress layer.
In the design method of the lightweight double-layer structure of the palm mattress, the thickness of the lower mattress layer is 1-2 times of that of the upper mattress layer.
In the method for designing a lightweight double-layer structure of a palm mattress, the deflection value is a circular measurement region having a radius of 12mm and having a stress center as a circle in a plane in which the stress center of the upper mattress layer or the lower mattress layer is located, and the deflection value obtained in the measurement region is the deflection value of the mattress layer.
In the method for designing the lightweight double-layered structure of the palm mattress, the density of each mattress layer is set according to the deflection values of the upper mattress layer and the lower mattress layer by setting the density of the lower mattress layer to be lower than the density of the upper mattress layer.
In the design method of the lightweight double-layer structure of the coir mattress, the method for setting the deflection values of the upper mattress layer and the lower mattress layer to the densities of the mattress layers comprises the following steps:
let a mattress layer have a down-deflection value of 0.1x (mm) and a density of y (kg/m) 3 ) The minimum density of the mattress layer is k (kg/m) 3 ) K is 78 to 90;
y = k when x < 1;
y = k +5 × (x-1) when x < 3 > is 1 ≦ 1;
when x is larger than or equal to 3, y = k +20+10 x (x-3).
In the design method of the lightweight double-layer structure of the palm mattress, k is 80-88.
In the design method of the lightweight double-layer structure of the palm mattress, k is 85.
The research process of the invention comprises the following steps:
1. adopting ANSYS to carry out super-elastic model research on the palm mattress so as to derive the deformation distribution of the interlayer parts of the elastic supporting layer of the mattress. And establishing a palm material model, in particular a mountain palm material model. Specifically, the elastic modulus 46.7KPa and the Poisson ratio 0.2 of the palm mattress are input in ANSYS software, and a typical constitutive model combining the super-elastic material is established, wherein the strain energy function is described as follows:
and when N =3, the special reduction form of the polynomial is a constitutive model of the Yeoh form, and the model is subjected to curve fitting to obtain the mountain palm super-elastic material model.
2. Finite element solution is carried out, the size of the mattress is selected to be a =200cm in length, b =100cm in width and 12cm in thickness, and due to the symmetry of the structure and the convenience of calculation, one half of the mattress can be taken for finite element analysis, so that the length of the mattress is a =200m, the width of the mattress is b =50cm, and the model is shown in figure 1. In FIG. 1, the length is along the X-direction, the width is along the Z-direction, and the thickness is along the Y-direction.
Referring to the biological geometric data of the common general human body, the load application area is 1.7m multiplied by 0.4m, and the weight is 80kg (considering the safety operation, the human body mass is a larger value). Thus, the pressure applied to the model is: p = F ÷ S =80 × 10 ÷ 1.7 × 0.4=1176.5 (pa). Due to the symmetry of the structure, the load application area is 1.7m multiplied by 0.2m, the uniform force application range is on the axis of the mattress, the structure and the load are symmetrical about the XY plane, and the load distribution is shown in figure 2.
3. And (5) carrying out interlayer stress deformation analysis on the mattress model. Under the action of applying human body simulation load, the downwarping values of the mattress in the positions respectively 1cm, 3cm, 5cm, 7cm, 9cm and 11cm away from the upper surface of the mattress are analyzed, the distance from the measuring point of each layer to the stress center of the surface is 15cm, and fig. 3 is a downwarping value curved surface diagram of nodes of different cross sections along the central line. As shown in fig. 3, the closer to the upper surface of the mattress, the less the compression deformation there. When the distance from the upper surface of the mattress is 1cm, the compression deformation with the distance more than 0.25m from the central line is positive, which shows that the part is pressed upwards, and the compression stress of the layer is more concentrated at the position of 0-0.25 m. From fig. 3, the layer 11cm from the upper surface is still under compressive stress at a distance of 0.3m from the centerline. The further away from the upper surface, the greater the area that is deformed by compression. Since the total load of the human body on the object is constant under a certain condition, the larger the pressure area is, the more dispersed the pressure stress is.
4. Analyzing stress distribution of each layer of the mattress, and analyzing stress cloud charts in a model of the mattress with human body load, wherein the analysis distances from the upper surface of the mattress are respectively 1cm, 3cm, 5cm, 7cm, 9cm and 11cm, and stress charts of each layer are shown in figures 4-9. The application of stress is a locally distributed force applied to the upper surface of the mattress. The stress cloud is a cloud of horizontal sections at different thicknesses of the mattress, which is a top view. In the original drawing of the attached drawings, the bar-shaped cloud charts at the bottom of each drawing gradually change from left to right in the changing trends of yellow, orange, red, purple and blue, and indicate that the stress is larger and larger. The closer to the force application surface shown in the original drawing, the closer the color of the force application area is to the color of the right part of the bar cloud chart, which shows that the stress applied to the area is larger. Meanwhile, it can be clearly seen in fig. 4-9 that as the distance between the force-bearing surface and the force-applying surface increases, the stress area increases and the stress distribution tends to be uniform. From figures 4-9, there is a stress concentration in the upper left corner of the mattress, the more pronounced the effect of the concentration closest to the bottom layer, primarily due to the fact that the cross-section near the bottom is more affected by the fixed constraint of the bottom, which is due to the fixed constraint.
5. The lightweight mattress model is established, and the analysis according to the analysis of the stress deformation analysis among the layers and the stress distribution analysis of the layers of the mattress can be obtained, when the elastic supporting layer of the mattress is under the action of the weight of a human body, the stress borne by each layer is smaller along with the farther distance between the layer surface and the contact surface, and the stress tends to be uniformly distributed, namely the stress borne by the whole elastic supporting layer is a process of gradually reducing the gradient, theoretically, the final stress distribution can be in integral uniform distribution when the elastic supporting layer is thick enough, and the stress at the moment only needs to ensure the minimum stress required by the rigidity of the mattress. The plant fiber mattress manufactured under the same production process condition ensures the rigidity of the product mainly through the density of the mattress, and when the stress requirement is higher, the corresponding density of the mattress is required to be higher. Therefore, we can correlate the density of the mattress with the required stress, so as to build a structural model of the mattress, as shown in fig. 10. The density of the 1 st layer is the maximum, the density gradually decreases with the increase of the layer number, and the density of the bottommost layer is the minimum. The density of the layer 1 should meet the rigidity requirement corresponding to the local maximum stress of the human body, and the bottommost layer must meet the integral supporting rigidity requirement of the human body, namely the average compressive stress requirement of the human body.
6. The stress conditions of elastic materials such as memory cotton, latex sponge, environment-friendly palm, sisal, coconut palm, spandex, palm substitute cotton, common sponge, bamboo charcoal cotton, blasting cotton and the like are the same as the stress conditions of the mountain palm material analyzed by the method, so the method can be used for research. The mattresses made of various elastic materials can be layered according to the stress condition, and the supporting force provided by each layer of material accords with the average pressure of a human body on the layer. Because the more the density and the more the stress are, the more uniform the elastic material is, the more the mattress is made of the uniform elastic material, the lighter layered structure can be provided for the mattresses made of the respective elastic materials. The research results of various elastic materials are similar to the research results of the invention, and finally, the functional relation between the downwarping value of the mattress layer of various materials and the layer density can be obtained, the functional formula can be similar to the formula of the method for setting the layer density by the deflection value of each mattress layer provided by the invention, and the difference lies in that the values of k, x and x are different along with the change rate of the deflection value.
The applicant has carried out a large number of experimental studies on the present invention, some of which are as follows:
according to the research process of the invention, the mattress can be theoretically divided into a plurality of layers to be arranged with density gradient, so that the lightweight structure of the mattress is realized, but according to the prior art, if the number of layers of the mattress is too large, the problems of complex process and low production efficiency are caused. The mattress with the lightweight structure is designed into a two-layer structure, so that the production process of the mattress with the lightweight structure is simplest and convenient to produce. In order to examine the lightweight double-layer structure model provided by the invention, the inventor manufactures a lightweight double-layer structure palm mattress and carries out experimental analysis on the lightweight double-layer structure palm mattress.
The same thickness specification of the prior plant fiber mattress is manufactured by adopting single density molding, and the density value of the mattress is formulated by referring to the durability index meeting the standard requirement of 'soft furniture palm fiber elastic mattress'. This experiment has made the palm mattress of mountain palm mattress two kinds of different density, forms the palm mattress of lightweight bilayer structure.
1. Experimental method
(1) Two different density units are produced from the palm material respectively. The production method comprises the processes of adding latex into the palm fiber, pressing into a sheet, hot-pressing and shaping, vulcanizing and the like. According to the method of the invention, k value is set to be 85, a palm mattress with the total thickness of 120mm is manufactured and is designed to be 30mm thick at the upper mattress layer and 90mm thick at the lower mattress layer, and according to the relation between the deflection value and the density value of the invention, the density of the upper mattress layer is 120kg/m 3 (ii) a The density of the lower mattress layer is 90kg/m 3 。
(2) The two bed layers are combined after hot pressing and vulcanization. The assembled mattress structure is shown in fig. 11.
(3) Tests show that the overall density of the experimental double-layer mattress is 94-100kg/m 3 Compared with the whole lowest density (114 kg/m) of the prior common mattress 3 ) The decrease is close to 15%.
2. Results and analysis of the experiments
(1) Mattress durability performance test
In order to effectively verify the durability performance of the mattress structure, the experiment is mainly carried out on samples of three batches with different comprehensive densities and the specification of the mattress being 2000 × 1200 × 120mm according to the requirements of GB-T26706-2011 'Soft furniture palm fiber elastic mattress standard'. The test results are shown in table 1.
TABLE 1 comparative analysis table of durability test results
According to the index requirements of GB-T26706-2011 'Soft furniture palm fiber elastic mattress standard', the durability is equal to or larger than 90%, the mechanical index of the durability of the lightweight double-layer structure mattress is good, the quality requirement is met, and the durability is larger than 92% and reaches the level of the existing product.
(2) Mattress hydrostatic compression performance test
In order to judge the static compression mechanical property index of the mattress more scientifically and accurately, the mechanical test of the lightweight double-layer structure mattress is carried out by adopting a detection method required by GB-T26706-2011 'Soft furniture palm fiber elastic mattress standard'. The test data are shown in table 2.
TABLE 2 GB-T26706-2011 static compression Experimental data
According to the index requirements of GB-T26706-2011 'Soft furniture palm fiber elastic mattress standard', the product is qualified when the static compression is more than or equal to 88%. The lightweight double-layer structure mattress has the static compression index of about 93 percent, not only reaches the national standard and is a qualified product, but also reaches the level of the existing product.
Compared with the prior art, the invention has the following beneficial effects:
1. according to the invention, through the analysis of the palm mattress, the distance between the stressed deformation area of the mattress and the force application surface is increased and increased after the mattress is applied with load. Because the total load of a human body lying on the mattress is constant, the stress is diffused to the periphery along with the stress center along with the downward transmission of the load, and the average stress borne by the lower part of the mattress is reduced. Therefore, the lower part of the mattress made of the palm fiber material does not need to keep higher supporting strength, and only needs to meet the corresponding supporting force. However, since the conventional mattresses are produced at a uniform density, there is a case where the supporting force is excessive in the lower part of the mattress. The invention can carry out layered design on the palm mattress and reduce part of the density of the lower part of the mattress, thereby realizing the effects of reducing the total density of the mattress, saving the material consumption and the production cost.
2. According to the invention, the palm mattress is designed into a two-layer structure by utilizing the research result of the lightweight structure of the palm mattress, and the production process of the lightweight structure of the mattress is simplest and easy to realize. According to the limitation of the thickness relation of the upper mattress layer and the lower mattress layer, the thickness of the upper mattress layer is not too thin, and the upper mattress layer can be well supported by combining the thickness and the density of the upper mattress layer which are designed according to the limitation. And the thickness of the lower mattress layer is designed to be not less than that of the upper mattress layer, so that the upper mattress layer and the load can be well supported by the lower mattress layer, and the structure is reasonable.
3. Through the lightweight double-layer structure of the palm mattress designed by the invention, the mattress can still ensure the durability and the static compression index on the basis of reducing the total density of the palm mattress. The indexes not only meet the national standard, but also reach the level of the existing products.
4. The invention establishes the relation between the downwarping value of the mountain palm mattress and the designed density of the mattress, and the lightweight structure of the palm mattress meeting the standard can be conveniently and quickly designed by the method.
5. Through estimation, the total density of the lightweight palm mattress designed by the invention is reduced by about 15% compared with the total density of the existing palm mattress, and the total production cost can be reduced by about 12%. Because the palm mattress is a popular consumer product, the invention has good market prospect and can generate extremely high economic benefit.
In conclusion: by the design of the invention, the total density of the palm mattress can be reduced, the material consumption of the mattress can be saved, and the production cost can be reduced; the lightweight structure of the mattress designed by the invention has simple production process and reasonable structure; the lightweight double-layer structure of the palm mattress designed by the invention has the advantages that on the basis of reducing the total density of the palm mattress, the quality not only meets the national standard, but also can reach the level of the existing product; when the lightweight double-layer structure of the palm mattress is designed, the palm mattress is convenient and quick; the invention reduces the total density of the prior palm mattress, has large degree of cost and large market potential.
Drawings
FIG. 1 is a finite element mesh partition of a mattress;
FIG. 2 is a load distribution of the mattress;
FIG. 3 is a graph of the sag values of nodes along the centerline for different cross-sections;
FIG. 4 is a stress cloud of Mises 1cm from the upper surface;
FIG. 5 is a graph of Mises stress clouds 3cm from the upper surface;
FIG. 6 is a graph of Mises stress clouds 5cm from the upper surface;
FIG. 7 is a graph of Mises stress clouds 7cm from the upper surface;
FIG. 8 is a graph of Mises stress clouds at 9cm from the upper surface;
FIG. 9 is a cloud of Mises stress at 11cm from the upper surface;
FIG. 10 is a structural model of a lightweight mattress;
figure 11 is a schematic structural view of a double-layered palm mattress.
The labels in the figures are: 1-upper mattress layer, 2-lower mattress layer.
Detailed Description
The present invention is further illustrated by the following examples, which are not to be construed as limiting the invention. Processes not specifically mentioned for the present invention are all common in the art.
Example 1. A design method of a lightweight double-layer structure of a palm mattress comprises the following steps:
palm mattresses 2000mm long, 1800mm wide and 120mm thick were designed. The coir mattress is divided into an upper mattress layer and a lower mattress layer, the thickness of the lower mattress layer is designed to be 4 times of that of the upper mattress layer, namely the thickness of the upper mattress layer is 24mm, and the thickness of the upper mattress layer is 96mm.
Firstly, establishing a palm material model of the mattress by using ANSYS software. A finite element solving method is adopted, and a palm mattress model corresponding to the length, the width and the thickness is built by using a palm material model. Then applying human body load on the palm mattress model, wherein the load area is 1700mm multiplied by 800mm, and the weight is 80kg; and (3) carrying out a stress deformation test on the mattress model after the human body load is applied to obtain the downwarping values of the upper mattress layer and the lower mattress layer, selecting the selection point of the downwarping value on the plane where the stress center of the mattress layer is located, and selecting a deflection value within 12mm from the stress center of the mattress layer as the downwarping value.
Finally, setting the density of the mattress layer according to the deflection values of the upper mattress layer and the lower mattress layer, wherein the deflection value of one mattress layer is 0.1x (mm), and the density of the mattress layer is y (kg/m) 3 ) The minimum density of the mattress layer is k (kg/m) 3 ) K is 78; according to when x < 1, y =78; when x is more than or equal to 1 and less than 3, y =78+5 (x-1); when x is larger than or equal to 3, y =98+10 x (x-3), calculated as: the density of the upper mattress layer is 117kg/m 3 The density of the lower mattress layer is 88kg/m 3 。
That is, the palm fiber mattress with the length of 2000mm, the width of 1800mm and the thickness of 120mm is designed into a light double-mattress layer structure by the invention. Wherein the upper mattress layer has a thickness of 24mm and a density of 117kg/m 3 (ii) a The lower mattress layer has a thickness of 96mm and a density of 88kg/m 3 。
Example 2. A design method of a lightweight double-layer structure of a palm mattress is disclosed, and a model establishing method and a stress deformation testing method of the embodiment are the same as those of embodiment 1. This embodiment designs a palm mattress of 1800mm in length, 1600mm in width and 120mm in thickness into a lightweight double mattress structure. The thickness of the lower bed cushion layer is designed to be 3.5 times of the thickness of the upper bed cushion layer, the thickness of the upper bed cushion layer is 26.7mm, the thickness of the lower bed cushion layer is 93.3mm, the downwarping values of the upper bed cushion layer and the lower bed cushion layer are selected on the plane where the stress center of the mattress layer is located, and a warping value within 10mm from the stress center of the bed cushion layer is selected as the downwarping value. Setting the density of the mattress layer by using the deflection values of the upper mattress layer and the lower mattress layer, wherein the k value is 80, and the designed density of the upper mattress layer is calculated to be 118kg/m 3 The design density of the lower mattress layer is 91kg/m 3 。
That is, the palm fibre mattress with the length of 2000mm, the width of 1800mm and the thickness of 120mm is designed into a light-weight double-mattress layer structure by the invention. Wherein the upper mattress layer has a thickness of 26.7mm and a density of 118kg/m 3 (ii) a The lower mattress layer has a thickness of 93.3mm and a density of 91kg/m 3 。
Example 3. Palm fiberThe design method of the lightweight double-layer structure of the mattress, the model building method and the stress deformation testing method of the embodiment are the same as those of the embodiment 1. The embodiment designs a coir mattress with the length of 1800mm, the width of 1600mm and the thickness of 150mm into a light-weight double-mattress layer structure. The thickness of the lower bed layer is designed to be 3 times of the thickness of the upper bed layer, the thickness of the upper bed layer is 37.5mm, the thickness of the lower bed layer is 112.5mm, the downwarping values of the upper bed layer and the lower bed layer are selected on the plane where the stress center of the mattress layer is located, and a deflection value within 6mm from the stress center of the bed layer is selected as the downwarping value. Setting the density of the mattress layer by using the deflection values of the upper mattress layer and the lower mattress layer, wherein the k value is 85, and the designed density of the upper mattress layer is calculated to be 122kg/m 3 The design density of the lower bed cushion layer is 94kg/m 3 。
Namely, the palm mattress with the length of 2000mm, the width of 1800mm and the thickness of 150mm is designed into a light-weight double-mattress layer structure by the invention. Wherein the upper mattress layer has a thickness of 37.5mm and a density of 122kg/m 3 (ii) a The lower bed cushion layer has a thickness of 112.5mm and a density of 94kg/m 3 。
Example 4. A design method of a lightweight double-layer structure of a palm mattress is disclosed, and a model establishing method and a stress deformation testing method of the embodiment are the same as those of embodiment 1. This embodiment designs a palm mattress of 1800mm in length, 180mm in width and 180mm in thickness into a lightweight double mattress layer structure. The thickness of the lower bed cushion layer is designed to be 2.5 times of the thickness of the upper bed cushion layer, the thickness of the upper bed cushion layer is 51.4mm, the thickness of the lower bed cushion layer is 128.6mm, the downwarping values of the upper bed cushion layer and the lower bed cushion layer are selected on the plane where the stress center of the mattress layer is located, and a warping value within 3mm away from the stress center of the bed cushion layer is selected as the downwarping value. Setting the density of the mattress layer by using the deflection values of the upper mattress layer and the lower mattress layer, wherein the k value is 88, and the designed density of the upper mattress layer is calculated to be 120kg/m 3 The design density of the lower bed cushion layer is 96kg/m 3 。
The palm mattress with the length of 2000mm, the width of 1800mm and the thickness of 180mm is designed into a light-weight double-mattress layer structure through the invention. Wherein the upper mattress layer has a thickness of 51.4mm and a density of 120kg/m 3 (ii) a The lower bed cushion layer has a thickness of 128.6mm and a density of 96kg/m 3 。
Example 5. A design method of a lightweight double-layer structure of a palm mattress is provided, and a model building method and a stress deformation testing method of the embodiment are the same as those of embodiment 1. Wherein the applied area of the human body load is 1800mm multiplied by 800mm, and the weight is 90kg. The embodiment designs the coir mattress with the length of 1800mm, the width of 180mm and the thickness of 180mm into a light-weight double-mattress layer structure. The thickness of the lower bed cushion layer is designed to be 2 times of the thickness of the upper bed cushion layer, the thickness of the upper bed cushion layer is 60mm, the thickness of the lower bed cushion layer is 120mm, the downwarping values of the upper bed cushion layer and the lower bed cushion layer are selected on the plane where the stress center of the mattress layer is located, and a downwarping value within 4mm from the stress center of the bed cushion layer is selected as the downwarping value. Setting the density of the mattress layer by using the deflection values of the upper mattress layer and the lower mattress layer, wherein the k value is 90, and the designed density of the upper mattress layer is calculated to be 119kg/m 3 The design density of the lower bed cushion layer is 96kg/m 3 。
The palm mattress with the length of 2000mm, the width of 1800mm and the thickness of 180mm is designed into a light-weight double-mattress layer structure by the invention. Wherein the upper mattress layer has a thickness of 60mm and a density of 119kg/m 3 (ii) a The lower bed cushion layer has a thickness of 120mm and a density of 96kg/m 3 。
Example 6. A design method of a lightweight double-layer structure of a palm mattress is provided, and a model building method and a stress deformation testing method of the embodiment are the same as those of embodiment 1. Wherein the applied area of the human body load is 1800mm multiplied by 750mm, and the weight is 90kg. The embodiment designs the palm mattress with the length of 1800mm, the width of 180mm and the thickness of 300mm into a light-weight double-mattress layer structure. The thickness of the lower bed cushion layer is designed to be 1 time of that of the upper bed cushion layer, the thicknesses of the upper bed cushion layer and the lower bed cushion layer are both 150mm, the downwarping values of the upper bed cushion layer and the lower bed cushion layer are selected on the plane where the stress center of the mattress layer is located, and a downwarping value within 4mm from the stress center of the bed cushion layer is selected as the downwarping value. Setting the density of the mattress layer by using the deflection values of the upper mattress layer and the lower mattress layer, wherein the k value is 88, and the designed density of the upper mattress layer is calculated to be 117kg/m 3 The design density of the lower bed cushion layer is 97kg/m 3 。
That is, the length is 2000mm, the width is 1800mm andthe palm mattress with the thickness of 300mm is designed into a light-weight double-mattress layer structure. Wherein the upper mattress layer has a thickness of 150mm and a density of 117kg/m 3 (ii) a The lower bed cushion layer has a thickness of 150mm and a density of 97kg/m 3 。
Example 7. A design method of a lightweight double-layer structure of a palm mattress is disclosed, and a model establishing method and a stress deformation testing method of the embodiment are the same as those of embodiment 1. Wherein the applied area of the human body load is 1850mm multiplied by 800mm, and the weight is 85kg. The embodiment designs the coir mattress with the length of 1800mm, the width of 180mm and the thickness of 180mm into a light-weight double-mattress layer structure. The thickness of the lower bed cushion layer is designed to be 1.5 times of the thickness of the upper bed cushion layer, the thickness of the upper bed cushion layer is 72mm, the thickness of the lower bed cushion layer is 108mm, the downwarping values of the upper bed cushion layer and the lower bed cushion layer are selected on the plane where the stress center of the mattress layer is located, and a warping value within 6mm from the stress center of the bed cushion layer is selected as the downwarping value. Setting the density of the mattress layer by using the deflection values of the upper mattress layer and the lower mattress layer, wherein the k value is 84, and the designed density of the upper mattress layer is calculated to be 115kg/m 3 The design density of the lower bed cushion layer is 95kg/m 3 。
The palm mattress with the length of 2000mm, the width of 1800mm and the thickness of 180mm is designed into a light-weight double-mattress layer structure through the invention. Wherein the upper mattress layer has a thickness of 72mm and a density of 115kg/m 3 (ii) a The lower bed cushion layer has a thickness of 108mm and a density of 95kg/m 3 。
Claims (7)
1. A design method of a lightweight double-layer structure of a palm mattress is characterized by comprising the following steps: designing a coir mattress into an upper mattress layer and a lower mattress layer, establishing a coir mattress model, carrying out stress deformation analysis on the coir mattress model after applying human body load, determining the deflection values of the upper mattress layer and the lower mattress layer in the coir mattress model, and setting the density of each mattress layer according to the deflection values of the upper mattress layer and the lower mattress layer to obtain a coir mattress lightweight double-layer structure;
the flexibility values of the upper bed cushion layer and the lower bed cushion layer refer to a circular measuring area with the radius of 12mm, which is set in a plane where a stress center of the upper bed cushion layer or the lower bed cushion layer is located and takes the stress center as a circle center, and the flexibility value measured in the measuring area is the flexibility value of the mattress layer;
the method for setting the density of each mattress layer by using the deflection values of the upper mattress layer and the lower mattress layer as the lower deflection value of the mattress layer comprises the following steps:
let the down deflection value of a mattress layer be 0.1x (mm), the density of the mattress layer be y (kg/m) 3 ) The minimum density of the mattress layer is k (kg/m) 3 ) K is 78 to 90;
when x < 1, y = k;
y = k +5 × (x-1) when x < 3 > is 1 ≦ 1;
when x is larger than or equal to 3, y = k +20+10 x (x-3).
2. The design method of the lightweight double-layer structure of the palm mattress according to claim 1, characterized in that: the thickness of the lower mattress layer is 1-4 times of the thickness of the upper mattress layer.
3. The design method of the lightweight double-layer structure of the palm mattress according to claim 2, characterized in that: the thickness of the lower mattress layer is 1-3 times of the thickness of the upper mattress layer.
4. The design method of the light-weight double-layer structure of the palm mattress according to claim 3, characterized in that: the thickness of the lower mattress layer is 1-2 times of the thickness of the upper mattress layer.
5. The design method of the lightweight double-layer structure of the palm mattress according to claim 1, characterized in that: the method for setting the density of each mattress layer according to the deflection values of the upper mattress layer and the lower mattress layer is to reduce the density of the lower mattress layer relative to the density of the upper mattress layer.
6. The design method of the lightweight double-layer structure of the palm mattress according to claim 1, characterized in that: and k is 80-88.
7. The design method of the lightweight double-layer structure of the palm mattress according to claim 6, characterized in that: k is 85.
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