Cortex phellodendri texture characterization method based on mechanical property analysis and application of cortex phellodendri texture characterization method in water content prediction

Abstract

The invention discloses a golden cypress texture characterization method based on mechanical property analysis and application of the golden cypress texture characterization method in water content prediction. The golden cypress texture characterization method comprises the following steps: determining a physical property test suitable for detecting golden cypress texture and parameters for characterizing the texture; preparing an amur corktree bark sample for physical property testing; basic parameters for three-point bending finite element simulation are determined; establishing a finite element model for detecting the texture physical property of the cortex phellodendri; verifying the reliability of the finite element model; and establishing the relationship between the cortex phellodendri texture parameters and the water content by applying finite element simulation. The invention relates to a characterization method of cortex phellodendri texture and application of the characterization method in water content prediction, the method can accurately, objectively and comprehensively characterize the cortex phellodendri texture, provides convenience for rapid prediction of the water content of the cortex phellodendri, and has important significance for guaranteeing the quality of traditional Chinese medicines such as cortex phellodendri in a storage link.

Description

[0001] Technical field: The present invention relates to the field of traditional Chinese medicine, and in particular to a method for characterizing the texture of Phellodendron chinense based on mechanical property analysis and its application in predicting water content. Background technology:

[0002] Phellodendron chinense Schneid. is derived from the dried bark of the Rutaceae plant Phellodendron chinense Schneid. It has the effects of clearing away heat and dampness, purging fire and removing steam, detoxifying and curing sores, and is widely used in the market. Storage is an important link to ensure the quality of Phellodendron, and its water content should be strictly controlled. Phellodendron is easily damp and softened during storage. If the water content is too high, microorganisms will grow in the Phellodendron, and the active ingredients will decompose, which will lead to mold and rot, and the quality will be damaged.

[0003] The typical method to determine the moisture content of Phellodendron chinense is the drying method. Although this method can accurately determine the moisture content, it is time-consuming and requires equipment. Texture is an important indicator for the identification of traditional Chinese medicine properties and is closely related to moisture content. It is more convenient and faster to predict the moisture content of Phellodendron chinense based on texture characteristics. How to characterize the texture of Phellodendron chinense and its relationship with moisture content need to be studied.

[0004] In the field of medicine, in-depth research on the texture characteristics of traditional Chinese medicine is extremely limited. Most studies on the characterization of the texture of traditional Chinese medicine are still subjective and vague, and still use qualitative indicators such as toughness, brittleness, looseness, stickiness, firmness, powderiness, and hornyness to describe the texture of traditional Chinese medicine based on human sensory results. A few studies have used an artificial quantitative scoring system to characterize the texture of traditional Chinese medicine. Because its quantitative scoring system is still based on personal judgment, the characterization of the texture of traditional Chinese medicine in the above studies still has subjective limitations and cannot accurately reflect the differences between textures. There are also a few studies that use physical property analyzers such as texture analyzers to detect the texture of traditional Chinese medicine. Due to the lack of in-depth mining of texture data and the lack of mathematical analysis of the mechanical behavior of traditional Chinese medicine during stress, the characterization of the texture of traditional Chinese medicine in the above studies needs to be improved. In summary, there are limitations such as subjectivity, ambiguity, and roughness in the current texture characterization methods, which hinder the study of the texture characteristics of Phellodendron chinense and its relationship with water content.

[0005] In the field of agriculture and forestry, mechanical properties analysis has been widely used in the study of biomechanical properties of plant samples. Mechanical properties analysis is to analyze the mechanical characteristics of the research object under different environments (temperature, medium, humidity) when subjected to various external loads such as tension, compression, bending, torsion, impact, and alternating stress. The mechanical characteristics such as elastic modulus, shear modulus, constitutive curve, etc. obtained based on mechanical properties analysis can more objectively, accurately and comprehensively characterize the texture of Phellodendron and predict the moisture content, and achieve quality control of the texture sensory properties of leather plant samples represented by Phellodendron.

[0006] Finite element simulation is a numerical method that can simulate complex mechanical responses, including deformation, stress and energy. It facilitates the solution of complex engineering problems by using approximate solutions of partial differential equations. With the development of finite element software such as Abaqus, finite element simulation of physical property testing to assist mechanical performance analysis has become a new trend in biomechanical performance analysis.

[0007] In summary, it is possible to establish a more comprehensive method for characterizing the texture of Phellodendron amurense by combining mechanical properties analysis with finite element simulation technology, so as to more reliably and conveniently predict the moisture content of Phellodendron amurense to ensure its storage quality. Summary of the invention:

[0008] In view of this, it is necessary to establish a texture characterization method of Phellodendron chinense based on mechanical properties analysis for application in the prediction of moisture content.

[0009] A method for characterizing the texture of Phellodendron chinense and its application in predicting moisture content, comprising the following steps:

[0010] Step 1: Determine the physical property test suitable for detecting the texture of Phellodendron chinense and the parameters for characterizing its texture;

[0011] Step 2: preparing cork samples for physical property testing;

[0012] Step 3: Determine the basic parameters of cork for three-point bending finite element simulation;

[0013] Step 4: Establish a finite element model for testing the physical properties of cork;

[0014] Step 5: Verify the reliability of the finite element model;

[0015] Step 6: Use finite element simulation to establish the relationship between the texture parameters and moisture content of Phellodendron chinense.

[0016] Preferably, in step 1, the physical property test for detecting the texture of Phellodendron chinense is determined to be a three-point bending test based on the traditional manual bending test. Based on the material mechanics hypothesis, the parameters characterizing its texture are determined to be bending strength, bending stiffness and bending modulus by analyzing the mechanical properties of Phellodendron chinense during the three-point bending process.

[0017] Preferably, in step 2, in order to reduce the influence of shear force on the three-point bending of Phellodendron chinense, the length of the Phellodendron chinense sample is determined to be 40 mm. Considering that the maximum moisture content of Phellodendron chinense within the hygroscopic range is about 25%, a total of 5 Phellodendron chinense samples with moisture content levels (0% to 5%, 5% to 10%, 10% to 15%, 15% to 20%, 20% to 25%) were prepared.

[0018] Preferably, in step three, the basic parameters of the cork for constructing the three-point bending finite element model include size (length, thickness, width), density, failure stress, failure strain, elastic modulus, and Poisson's ratio.

[0019] Preferably, in step 4, Abaqus simulation technology is used to establish a three-point bending model of Phellodendron chinense with different moisture contents.

[0020] Preferably, in step 5, the mechanical behavior of Phellodendron chinense under the real physical property test and the simulated physical property test, the probe loading force-displacement curve and the parameters characterizing the texture are compared. If the above results are consistent or the error is less than 20%, it proves that the finite element model is reliable and can be used for moisture content prediction. The three-point bending loading speed, loading displacement speed and loading displacement are set to 10mm / min, 5mm / min and 10mm respectively in the Y-axis direction, and the contact trigger force between the loading probe and Phellodendron chinense is set to 0.5N.

[0021] Preferably, in step six, three parallel experiments are conducted on three-point bending tests on Phellodendron chinense with different moisture contents (2.5%, 7.5%, 12.5%, 17.5%, 22.5%), and linear regression is performed between the moisture content of Phellodendron chinense and the parameters characterizing the texture of Phellodendron chinense.

[0022] In the present invention, the three-point bending test is used to detect the texture of Phellodendron chinense, and the bending strength, bending stiffness, and bending modulus are determined as indicators to measure its texture. These indicators are linearly correlated with the moisture content of Phellodendron chinense. A 5% increase in moisture content will result in a decrease in bending strength of about 2.44MPa, a decrease in bending modulus of about 22.17MPa, and a decrease in bending stiffness of about 19.36N.mm. 2 .

[0023] The present invention relates to a method for characterizing the texture of Phellodendron chinense based on mechanical property analysis and its application in predicting water content. The method can accurately, objectively and comprehensively characterize the texture of Phellodendron chinense, provide convenience for quickly predicting its water content, and is of great significance for ensuring the quality control of traditional Chinese medicines such as Phellodendron chinense in the processing and storage links. Description of the drawings:

[0024] Figure 1 It is a typical method for manually testing the texture of cork.

[0025] Figure 2 It is a three-point bending physical property test method for cork texture.

[0026] Figure 3 It is a simplified diagram of the force in a three-dimensional three-point bending test. Note: F represents the force applied by the loading probe at the middle position.

[0027] Figure 4 The distribution diagram of the internal force of Phellodendron chinense along the X-axis. (a) Shear force diagram. (b) Bending moment diagram. Note: F Q represents the shear force on the cross section. M represents the bending moment on the cross section.

[0028] Figure 5It is the linear distribution diagram of the normal stress in the middle cross section of Phellodendron chinense.

[0029] Figure 6 This is a typical force-displacement curve of the tensile test of cork at five moisture contents.

[0030] Figure 7 The bar graphs of cork material parameters at five water contents. (a) Poisson's ratio. (b) Failure strain. (c) Failure stress. (d) Elastic modulus. Note: * indicates significant difference compared with the water content of 0% to 5% (p<0.05).

[0031] Figure 8 This is the assembly diagram of the three-point bending simulation model. (a) Front view. (b) Side view. (c) Top view.

[0032] Fig. 9 The mesh diagram of the three-point bending simulation model. (a) Front view. (b) Side view. (c) Top view.

[0033] Fig.10 It is a schematic diagram of an actual three-point bending test in a three-dimensional Cartesian coordinate system.

[0034] Fig.11 Comparison diagram of the deformation process of cork in simulation and actual experiment. (a)-(c) Simulation process.

[0035] (d)-(f) Actual process.

[0036] Fig.12 It is a comparison diagram of the force-displacement curves of three-point bending between simulation and actual experiment.

[0037] Fig.13 It is a typical force-displacement curve of the simulated three-point bending test under five water contents.

[0038] Fig.14 The following are the cloud diagrams of the final stress state of Phellodendron chinense at five moisture content levels. (a) Moisture content 2.5%. (b) Moisture content 7.5%. (c) Moisture content 12.5%. (d) Moisture content 17.5%. (e) Moisture content 22.5%.

[0039] Fig.15 The following are the cloud diagrams of the final strain state of Phellodendron chinense at five moisture content levels. (a) Moisture content 2.5%. (b) Moisture content 7.5%. (c) Moisture content 12.5%. (d) Moisture content 17.5%. (e) Moisture content 22.5%.

[0040] Fig.16 It is the design flow chart of this invention patent. Specific implementation method:

[0041] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0042] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] The present invention provides the following specific embodiments.

[0044] A method for characterizing the texture of cork based on mechanical property analysis and its application in predicting moisture content, comprising the following steps:

[0045] Step 1, determining the physical property test suitable for detecting the texture of Phellodendron chinense and the parameters for characterizing its texture;

[0046] Step 2, preparing a cork sample for physical property testing;

[0047] Step 3, determine the basic parameters for three-point bending finite element simulation;

[0048] Step 4, establishing a finite element model for testing the physical properties of cork;

[0049] Step 5: Verify the reliability of the finite element model;

[0050] Step six, use finite element simulation to establish the relationship between the texture parameters and moisture content of Phellodendron chinense.

[0051] In step 1, the physical property test for detecting the texture of Phellodendron chinense was determined to be a three-point bending test based on the traditional manual bending test. Based on the material mechanics hypothesis, the mechanical properties of Phellodendron chinense were analyzed during the three-point bending process, and the parameters characterizing its texture were determined to be bending strength, bending stiffness and bending modulus.

[0052] In step 2, in order to reduce the influence of shear force on the three-point bending of Phellodendron, the length of the Phellodendron sample was determined to be 40 mm. Considering that the maximum moisture content of Phellodendron in the hygroscopic range is about 25%, a total of 5 Phellodendron samples with moisture content levels were prepared (0% to 5%, 5% to 10%, 10% to 15%, 15% to 20%, 20% to 25%).

[0053] In step three, the basic parameters of Phellodendron chinense for constructing a three-point bending finite element model include size (length, thickness, width), density, failure stress, failure strain, elastic modulus, and Poisson's ratio.

[0054] In step 4, Abaqus simulation technology was used to establish a three-point bending mold for cork with different moisture contents.

[0055] In step 5, the mechanical behavior of Phellodendron chinense under the real physical property test and the simulated physical property test, the probe loading force-displacement curve and the parameters characterizing the texture are compared. If the above results are consistent or the error is less than 20%, it proves that the finite element model is reliable and can be used for moisture content prediction. The three-point bending loading speed, loading displacement speed and loading displacement are set to 10mm / min, 5mm / min and 10mm respectively along the Y-axis, and the contact trigger force between the loading probe and Phellodendron chinense is set to 0.5N.

[0056] In step six, three parallel experiments were conducted on three-point bending tests of Phellodendron chinense with different moisture contents (2.5%, 7.5%, 12.5%, 17.5%, and 22.5%), and linear regression was performed between the moisture content of Phellodendron chinense and the parameters characterizing the texture of Phellodendron chinense.

[0057] In the present invention, the texture of Phellodendron chinense refers to the mechanical properties of Phellodendron chinense when it is bent.

[0058] The shortcomings of existing texture characterization methods are mainly manifested in the following aspects: due to the limitations of human senses, the texture characterization results of most methods are still very subjective and ambiguous. The current method of using texture analyzer to test the texture of traditional Chinese medicine lacks mechanical analysis of the test process, and the texture characterization results are too rough.

[0059] The main purpose of the present invention is to provide a texture characterization method to address the shortcomings of existing methods. The method can accurately, objectively and comprehensively characterize the texture of Phellodendron chinense, provide convenience for quickly predicting its water content, and is of great significance for ensuring the quality of Chinese medicines such as Phellodendron chinense during storage.

[0060] The present invention provides the following preferred embodiments:

[0061] Example 1 (Determination of physical property tests suitable for detecting the texture of Phellodendron chinense and parameters for characterizing its texture)

[0062] Texture detection is a method to obtain the texture characteristics of traditional Chinese medicine, which is usually done manually. Figure 1 The manual bending test shown is considered to be a typical method for testing the texture of cork, which can only obtain a subjective and vague feeling of the texture characteristics without quantitative indicators. Figure 2 As shown, a three-point bending test simulating a manual bending test was investigated, which helps to find the potential parameters characterizing the texture of cork.

[0063] In order to simplify the calculation, the mechanical properties of cork were analyzed during the three-point bending process based on the material mechanics theory. The assumptions about the cork material properties are as follows:

[0064] (1) Cork is solid and has no internal gaps, which means that the mechanical parameters characterizing the texture of Cork can be expressed by continuous coordinate functions, including force, bending moment, stress, strain, displacement, energy density, etc.

[0065] (2) Phellodendron chinense is homogeneous, which means that the components inside Phellodendron chinense are evenly distributed, so the texture characteristics obtained locally can represent the overall texture characteristics of Phellodendron chinense.

[0066] (3) Cork is isotropic, which means that it has the same mechanical properties when the probe applies load from different directions.

[0067] (4) The deformation of cork during three-point bending is very small compared to its physical size, which means that the geometric dimensions and loading conditions before deformation can be used for static analysis during the entire deformation process.

[0068] The analysis procedure is as follows:

[0069] (1) First, the statics analysis of Phellodendron chinense during three-point bending was carried out.

[0070] (2) Secondly, the internal forces and deformations of Phellodendron chinense during three-point bending were analyzed.

[0071] (3) Finally, the mechanical properties parameters of Phellodendron chinense under the three-point bending test were calculated as potential indicators to characterize its texture.

[0072] Through physical analysis, it is found that the three-point bending process of Phellodendron chinense is similar to the bending process of a simply supported beam. First, through static analysis, the external force applied to the bark of Phellodendron chinense is represented by a two-dimensional force diagram of the three-point bending test, as shown in Figure 2. Figure 3 As shown in the figure, the cork is simplified as a horizontal line fixed at two ends at two supporting points. Considering that the weight of the cork is much smaller than the load applied by the load probe, the weight of the cork is ignored in the static analysis. It can be inferred that the support force at each supporting point is equal to half of the force applied by the load probe at the middle position.

[0073] Then, by the method of sections and the balance of external and internal forces, Figure 4The shear force diagram and bending moment diagram along the X-axis are given. The shear force that causes the truncated part of the cork to rotate clockwise is defined as positive, and vice versa. The bending moment that causes the lower surface to stretch and the upper surface to compress is defined as a positive bending moment, and vice versa. It can be observed that in the shear force diagram, the magnitude of the shear force along the X-axis is always F / 2, and the direction is reversed at 2mm, which means that the bending moment increases linearly from the left support point to the middle position, and decreases linearly from the middle position to the right support point. Correspondingly, the bending moment diagram shows that the bending moment along the X-axis reaches a maximum value F at 2mm, indicating that the internal force is concentrated in the middle cross-section of the cork during the three-point bending process. Considering that the length of the cortex of the cork is sufficient to ensure pure bending, the contribution of the shear force to the deformation is ignored, which means that the middle cross-section remains flat and does not deform during the entire deformation process. Therefore, the positive stress that forms the bending moment on the middle cross-section is linearly distributed from the neutral plane to the upper and lower surfaces, as shown in Figure 5 As shown. Above the neutral plane is compressive stress, and below the neutral plane is tensile stress. It can be observed that the maximum normal stress is distributed at the top and bottom of the middle cross section, which can reflect how much effort is required to manually bend the cork.

[0074] Finally, the flexural strength based on the maximum normal stress in the middle cross section was calculated using the following equation:

[0075]

[0076] In addition, to evaluate the degree of deformation of cork during bending, the bending stiffness was calculated using the following equation:

[0077]

[0078] To evaluate the flexural properties of yellow cork, the flexural modulus was calculated using the following equation:

[0079]

[0080] where σ max Indicates the bending strength of cork based on the maximum normal stress (MPa), M z is the bending moment of the middle cross section (N.mm), b is the width of the cork (mm), and h is the thickness of the cork (mm).

[0081] Through the above physical analysis, flexural strength, flexural stiffness and flexural modulus were selected as potential mechanical indicators to characterize the texture of Phellodendron chinense. Flexural strength reflects the ability of Phellodendron chinense to withstand bending loads. Flexural stiffness reflects the degree of deformation of Phellodendron chinense under bending loads. Flexural modulus reflects the ability of Phellodendron chinense to resist bending deformation.

[0082] Example 2 (Determining basic parameters for three-point bending finite element simulation)

[0083] In this embodiment, basic parameters of Phellodendron chinense at various moisture contents were measured to construct a three-point bending finite element model, including size, density, failure stress, failure strain, elastic modulus, and Poisson's ratio.

[0084] 2.1 Determination of size

[0085] The shape of Phellodendron chinense is approximately a rectangular beam with a relatively flat surface. In order to determine its size, its width and thickness were measured using a vernier caliper (precision: 0.01 mm). Considering that the load was applied at the middle of the length in the three-point bending test, the width and thickness were also measured at the middle of the length. Considering that the effect of moisture content on the size of Phellodendron chinense is small, the actually measured width and thickness were used as the basic geometric parameters for finite element simulation instead of calculating the average value at each moisture content level. The width and thickness of Phellodendron chinense vary in the range of 6.5 mm to 9.5 mm and 2 mm to 4.5 mm, respectively, which are relatively small and are not significantly affected by moisture content (see Table 1).

[0086] 2.2 Determination of density

[0087] The mass of each sample is measured in advance with an electronic balance (accuracy: 0.001g), which is represented by M. After measuring the mass, each sample is immersed in water for half an hour to ensure that it is completely saturated. Then, a beaker containing 100mL of water is placed on the electronic balance, and the metal needle is immersed 1cm below the water surface. The reading on the electronic balance is represented by M. 1 Finally, remove the metal needle and insert it into the water-saturated sample and immerse it to the same depth. In this step, the sample cannot come into contact with the beaker wall to ensure the accuracy of weighing. The reading on the electronic balance is expressed in M 2 Assume that the density of water is 1g.cm -3 , then the volume of each sample is equal to M 2 -M 1 The density of Phellodendron chinense is expressed as:

[0088]

[0089] Where ρ is the density of Phellodendron chinense (g.cm -3 ), M represents the mass of Phellodendron chinense (g), M 1 represents the mass (g) of the metal needle part that is immersed 1 cm below the water surface, M 2 It represents the total mass (g) of the metal needles and Phellodendron chinense immersed 1 cm below the water surface.

[0090] It has been determined that the density of Phellodendron chinense is 0.66 g.cm when the moisture content is 0% to 5%, 5% to 10%, 10% to 15%, 15% to 20% and 20% to 25%. -3 、0.70g.cm -3 、0.75g.cm-3 、0.78g.cm -3 and 0.83g.cm -3 (See Table 1).

[0091] 2.3 Determination of failure stress, failure strain, elastic modulus and Poisson’s ratio

[0092] The tensile test was used to measure the material parameters of Phellodendron chinense, including failure stress, failure strain, elastic modulus and Poisson's ratio. The tensile test was performed by a texture analyzer with an A / TG probe, and the tensile speed was set to 5 mm / min. During the test, the texture analyzer analysis software Texture Lab Pro recorded the real-time force-displacement curve with failure point. The failure stress, failure strain, elastic modulus and Poisson's ratio of Phellodendron chinense can be expressed by equations (2) to (5):

[0093]

[0094]

[0095]

[0096]

[0097] Where σ is the breaking stress of Phellodendron chinense (MPa), F max is the force at the failure point (N), A is the area of ​​the middle cross section (mm 2 ), ε x is the axial failure strain (%), L is the length of the cork before the tensile test (mm), ΔL is the displacement of the failure point (mm); E is the elastic modulus of the cork (MPa); υ is the Poisson's ratio of the cork.

[0098] By comparison Figure 6 From the typical force-displacement curves of the tensile test at five moisture content levels, it can be observed that two main stages are common. The first stage is the elastic stage, and the curve increases linearly. The slope of the curve in this stage decreases with the increase of moisture content. Another stage after the elastic stage is the fracture stage, when the cork suddenly breaks, the curve shows a sharp linear decline. The slope of the curve in this stage also decreases with the increase of moisture content. The results show that the mechanical behavior of cork under tensile test is similar to that of brittle materials, especially at low moisture content, there is no obvious yield stage. Therefore, the failure point in the force-displacement curve is roughly located at the end of the elastic stage and the beginning of the fracture stage, which can be used to calculate the failure stress, failure strain, elastic modulus and Poisson's ratio.

[0099] In order to show the effect of moisture content on cork material parameters, Figure 7The changes of failure strain, failure stress, elastic modulus and Poisson's ratio with water content are shown. At the water content of 0% to 5%, 5% to 10%, 10% to 15%, 15% to 20% and 20% to 25%, the failure strain of Phellodendron chinense was 23.80%, 3.84%, 3.88%, 3.95% and 4.01% respectively. The results showed that the change of failure strain with the increase of water content was not significant (p>0.05). At the water content of 0% to 5%, 5% to 10%, 10% to 15%, 15% to 20% and 20% to 25%, the Poisson's ratio of Phellodendron chinense was 0.225, 0.227, 0.228, 0.230 and 0.232 respectively. With the increase of water content, its change trend is similar to that of failure strain. The water content has little effect on the failure strain and Poisson's ratio, that is, the force-displacement curve of Phellodendron chinense is more like that of a brittle material, which means that the deformation at the failure point is very small, while the failure strain and Poisson's ratio are parameters that describe the degree of deformation. At a water content of 0% to 5%, 5% to 10%, 10% to 15%, 15% to 20%, and 20% to 25%, the failure stress of Phellodendron chinense is 16.25MPa, 14.67MPa, 12.58MPa, 8.75MPa, and 7.87MPa, respectively. At a water content of 0% to 5%, 5% to 10%, 10% to 15%, 15% to 20%, and 20% to 25%, the elastic modulus of Phellodendron chinense is 428MPa, 382MPa, 323MPa, 221MPa, and 196MPa, respectively. Variance analysis showed that when the moisture content reached more than 15%, the moisture content had a significant effect on the failure stress and elastic modulus of Phellodendron chinense (p<0.05). Increasing the moisture content weakened the adhesion between fibers, which in turn led to a significant decrease in the failure stress and elastic modulus of the wood material. Overall, with the increase in moisture content, the failure stress and elastic modulus decreased significantly, while the failure strain and Poisson's ratio increased slightly.

[0100] Table 1

[0101]

[0102]

[0103] Example 3 (Construction of three-point bending finite element model)

[0104] According to the measured basic parameters of Phellodendron chinense, five finite element models corresponding to five moisture content levels were constructed for three-point bending simulation based on the assumptions of material mechanics theory, including small deformation, continuity, homogeneity, and isotropic linear elasticity of Phellodendron chinense.

[0105] 3.1 Solid Modeling

[0106] First, a geometric model of the three-point bending test was constructed. The finite element model of the three-point bending test consists of three parts, including the cork, the loading probe, and two support beams, which are established by the three-dimensional deformable solid stretching method. In order to simplify the force-deformation analysis during the three-point bending process, the shape of the cork is regarded as a regular rectangular block with no wrinkles on the surface and no gaps inside.

[0107] 3.2 Assignment of material properties

[0108] Assign material properties to the geometry model created above. First, create a material using the basic parameters of the cork. Then, create a solid homogenous cross-section using the above material and assign it to the cork. The material properties of the load probe and the two support beams are assigned based on the material parameters of the steel.

[0109] 3.3 Assembly

[0110] First, the solid models of the loading probe and two support beams were introduced to create the corresponding independent instances. On the top of each support beam, there is a support point in the middle of the Z direction. Reference points were created at the center of mass of the loading probe and the two support beams, respectively. Then, the corresponding independent instances were created from the solid model of the cork. Finally, the cork instance was placed horizontally on the two support beams, with both ends placed on the two support points, as shown in Figure 1. Figure 8 shown.

[0111] 3.4 Finite element analysis step

[0112] Considering that the actual three-point bending process is quasi-static and the deformation of PCC in this study is very small, the general static analysis step is selected as the analysis step of the finite element analysis. The maximum increment is set to 10000. The increment size is set in the range of 0.00000001 to 1, and the initial value is 0.1. The stress components and invariants (S), total strain components (E), translation and rotation (U) of the entire model, and the reaction force (RF) in the contact area between the loading probe and the cork are selected as field output variables. The created analysis step is denoted as analysis step 1.

[0113] 3.5 Contact Definition

[0114] The loading probe and two supporting beams were controlled by controlling the reference point at the center of mass. The two ends of the cork were fixed to the two supporting beams using binding constraints. A reference point was created between the loading probe and the cork, which was coupled to the contact area between the loading probe and the cork skin by coupling constraints to obtain the reaction force and displacement in this area. The contact pair algorithm was used to define the contact between the lower surface of the loading probe and the upper surface of the cork skin. Node-to-surface contact was selected as the contact type. Usually, the more rigid surface material in the contact alignment is considered as the master surface, while the other surface is considered as the secondary surface. Therefore, the lower surface of the loading probe was designated as the master surface, while the upper surface of the cork was designated as the slave surface. Then, the interactive contact properties were created. The normal behavior was defined by hard contact and augmented Lagrangian method. The friction coefficient for tangential behavior was set to 0.3. The above method was also applied to define the interaction between the lower surface of the cork and the upper surfaces of the two supporting beams.

[0115] 3.6 Definition of boundary conditions

[0116] In the initial analysis step, the degrees of freedom of the two loading probes are completely restricted by applying the fully fixed type boundary conditions to the corresponding reference points. Then, by using the displacement type boundary conditions at the reference point of the loading probe, a displacement of 10 mm downward in the Y direction is set in analysis step 1, and the other degrees of freedom are set to 0.

[0117] 3.7 Grid Division

[0118] Meshing is a key step in the preprocessing of finite element models. It is time-consuming and directly affects the accuracy of simulation results. Hexahedron is suitable for meshing of three-dimensional finite element models and can improve the mesh quality. Considering that all parts of the finite element model in this study are simple geometric shapes, the domain of each part is decomposed into smaller hexahedral blocks using a traditional structured method. Then, the above blocks are meshed using the C3D8R unit type. It is crucial to strike a balance between efficiency and accuracy in finite element simulation. Initially, a preliminary meshing is achieved using a cell size of 2mm. Next, according to Saint-Venant's principle, both stress and strain within the cork will be concentrated near the applied loading force. Therefore, denser meshes are placed in the middle and nearby areas of the cork's length to accurately capture the mechanical behavior under load. The generated mesh is as follows Fig. 9 shown.

[0119] 3.8 Assignments and Visualization

[0120] After completing the above preprocessing, submit the model in the Job module and analyze the results in the Visualization module. The stress and strain state of the cork is displayed in the cloud diagram. The force-displacement curve is derived based on the displacement of the loading probe and the reaction force on the contact surface of the cork. The entire process of three-point bending is exported as a video to compare with the deformation process in the actual experiment.

[0121] Example 4 (Verification of three-point bending finite element model)

[0122] To verify the accuracy of the constructed finite element model, the results of actual and simulated three-point bending tests were compared at five moisture content levels, including the mechanical behavior of Phellodendron chinense, probe loading force-displacement curves, and parameters characterizing texture.

[0123] 4.1 Actual three-point bending test of texture analyzer

[0124] The actual three-point bending test was conducted using a texture analyzer with a 1000N sensor. Before the experiment, the width and thickness of the cork were measured in advance. In order to facilitate the description of the following operations, a three-dimensional Cartesian coordinate system was established at the center of the middle cross section of the cork, as shown in Fig.10 The three-point bending test is shown in the simplified diagram in Figure 1. The span between the two fixed support points was adjusted to 40 mm to match the length of the sample. Each sample was placed on two support beams with the outer surface facing downward and the two ends along the X-axis direction fixed on the two support points. The loading probe was located 5 mm above the middle cross section and parallel to the Z-axis direction. The loading speed, loading displacement speed and loading displacement were set to 10 mm / min, 5 mm / min and 10 mm downward along the Y-axis direction, respectively, ensuring that the entire process was quasi-static and the deformation of the cortex of Phellodendron was small. The contact trigger force between the loading probe and Phellodendron was set to 0.5 N. During the three-point bending test, a digital camera was placed in the front view to record the entire deformation process. The texture analyzer analysis software Texture Lab Pro recorded the probe loading force-displacement curve during the test as the raw data for comparison and further mathematical calculations. Considering that the change in moisture content caused by water evaporation in the three-point bending test will affect the accuracy of the experimental results, the time required to complete a test was controlled within 1 minute, and one sample was taken for measurement at a time.

[0125] 4.2 Simulated three-point bending test in the finite element model

[0126] In the constructed finite element model, simulated three-point bending tests were performed on Phellodendron chinense at each moisture content. The geometric model of Phellodendron chinense was adjusted according to the width and thickness measured in the actual three-point bending test. The stress and strain distribution inside Phellodendron chinense during the three-point bending process was displayed by cloud diagrams and compared with the deformation of Phellodendron chinense in the actual test. In addition, the probe loading force-displacement curve was derived and the bending strength, bending stiffness, and bending modulus were calculated to analyze the error between the experimental and calculated results.

[0127] like Fig.11As shown. When the displacement increases from 0 mm to about 1 mm, Phellodendron chinense undergoes elastic deformation. In the finite element simulation, at this stage, the tensile stress is concentrated at the midpoint of the lower surface, while the compressive stress is concentrated at the midpoint of the upper surface. At the same stage, in the actual experiment, the lower surface of Phellodendron chinense is stretched and the upper surface of Phellodendron chinense is obviously squeezed. When the displacement changes from about 1 mm to about 1.5 mm, the deformation of Phellodendron chinense enters the destruction stage. In the finite element simulation of this stage, the tensile stress concentrated at the midpoint of the lower surface exceeds the destruction stress. At the same stage, in the actual experiment, a small crack appears in the middle of the lower surface of Phellodendron chinense and extends upward along the Y-axis. Overall, the deformation process of Phellodendron chinense in the simulation is consistent with the experimental results at various moisture content levels, which preliminarily proves the reliability of the model.

[0128] like Fig.12 As shown. The study found that the simulation curves were in good agreement with the experimental curves, especially in the initial elastic stage when the moisture content was less than 10%. The flexural strength, flexural stiffness and flexural modulus of Phellodendron chinense at various moisture contents were extracted from the probe loading force-displacement curves and are listed in Table 2. At each moisture content level, the flexural strength error between the simulation and the actual experiment was less than 15%, and the minimum error was 4.58% at a moisture content of 0-5%. A good correlation between the flexural modulus was also obtained between the simulation and the actual measurement, with a minimum error of 6.32% at a moisture content of 0-5%. In contrast, the flexural stiffness error between the simulation and the actual experiment was relatively large, but still within 20%, which may be due to the fact that during the actual three-point bending process, Phellodendron chinense was only non-rigidly fixed by friction, resulting in slight sliding, which led to an increase in the degree of freedom of deformation and a decrease in stiffness.

[0129] Table 2 Simulation and experimental results of potential indicators for characterizing texture

[0130]

[0131] In order to evaluate the reliability of the finite element model, it is necessary to discuss the errors between the simulation and the actual experiment. First, the assignment of geometric properties plays an important role in obtaining accurate simulation results. There are microscopic pores such as cell gaps inside the actual cork, which are ignored when constructing the solid finite element model. Generally, gaps in the structure will lead to a decrease in strength and stiffness, which leads to the simulation results generally being higher than the experimental results. However, the fibers and matrix are densely distributed inside the cork, which means that the volume of the gaps is negligible. Therefore, the defects in the geometric model are not the main factor causing the error. In addition, the definition of material properties is also crucial to ensure the required accuracy of the analysis and the reliability of the results. In the three-point bending test, plastic deformations such as cracks and fractures occur outside the elastic region, and the plastic material properties of cork are not fully considered in the construction of the finite element model, which can lead to errors between the simulation results and the calculated results. However, due to its brittleness, cork only experiences a small plastic deformation during the three-point bending process, which controls the plastic deformation within an acceptable range. Therefore, the error caused by plastic deformation is acceptable and will not affect the performance of the finite element model in predicting moisture content. It is worth noting that Phellodendron chinense, as a bark, has anisotropic material properties similar to wood. Compared with isotropic materials, the stress-strain coupling inside anisotropic materials is more complicated and requires more elastic constants to describe. However, for convenience, only one elastic modulus was measured when constructing the finite element model, and most of the errors between the simulation results and the experimental results are likely to be caused by this. Overall, the errors are within an acceptable range, and the three-point bending finite element model is proven to be accurate enough to study the relationship between Phellodendron chinense texture and moisture content.

[0132] Example 5 (Study on the relationship between texture characteristics and water content of Cortex Phellodendri using finite element model)

[0133] Five groups of moisture content (2.5%, 7.5%, 12.5%, 17.5%, 22.5%) were set up, and the relationship between them and the texture characteristics of Phellodendron chinense was studied using the finite element method, with three repeated experiments in each group. SPSS software (version 9.2, IMB Inc., Chicago, IL, USA) was used to perform variance analysis (ANOVA) on the simulation results, and a linear regression analysis was performed on the relationship between moisture content and simulation results. The significance level was set at 0.05. The flexural strength, flexural stiffness, and flexural modulus of Phellodendron chinense extracted from the simulation results were set as the dependent variables in the linear regression equation as parameters representing texture characteristics. The moisture content of Phellodendron chinense was set as the independent variable affecting the texture characteristics.

[0134] Fig.13A typical force-displacement curve of a simulated three-point bending test is shown as a function of moisture content. Similar to the tensile test results, the elastic stage and the failure stage are also the two main stages in the three-point bending process, and the slope gradually decreases with the increase of moisture content. However, when the moisture content reaches above 12.5%, a short plastic stage emerges between the elastic stage and the failure stage, which becomes slightly more obvious with the increase of moisture content. In this stage, the curve shows a nonlinear growth and the slope decreases compared to the elastic stage. In addition, with the increase of moisture content, a delay in the failure point can be observed, indicating that more deformation has occurred. The decrease in slope, the delay in the failure point, and the appearance of the plastic stage shown by the force-displacement curve mean a decrease in the brittleness of the cork, which is a sign that the cork is affected by moisture.

[0135] like Fig.14 and Fig.15 As shown, the ultimate stress and strain state of Phellodendron chinense displayed by the cloud map also shows the effect of water content on texture. It can be observed that with the increase of water content, the maximum principal stress at the bottom of the middle cross section decreases, while the maximum principal strain increases. Corresponding to the water content of 2.5%, 7.5%, 12.5%, 17.5%, and 22.5%, the obtained flexural strength is 16.33MPa, 14.44MPa, 12.43MPa, 8.75MPa, and 6.99MPa, and the flexural stiffness is 130.41N.mm 2 、110.4N.mm 2 、93.65N.mm2、63.98N.mm 2 、56.8N.mm 2 , and the bending modulus is 147.56MPa, 126.19MPa, 114.81MPa, 77.78MPa, and 60.53MPa. The above results show that due to the increase in water content, Phellodendron chinense is easier to bend and break, and the deformation caused by bending increases, which is also consistent with the change of the typical force-displacement curve.

[0136] Table 3 lists three linear models of flexural strength, flexural stiffness, and flexural modulus related to moisture content. All correlation coefficients R 2 All of them are greater than 0.90, which means that in the simulated three-point bending process, the change in water content can explain more than 90% of the changes in bending strength, bending stiffness and bending modulus. Overall, a 5% increase in water content will lead to a significant decrease in bending strength by 2.44MPa, a significant decrease in bending modulus by 22.17MPa, and a slight decrease in bending stiffness by 19.36N.mm 2 , which is consistent with the subjective results of manual testing.

[0137] Table 3 Three linear models of flexural strength, flexural stiffness, flexural modulus and water content.

[0138]

[0139] Note: max is the flexural strength of cork based on maximum normal stress (MPa), EI z is the bending stiffness of Phellodendron chinense (N.mm 2 ), E b is the flexural modulus of Phellodendron chinense (MPa), w is the water content of Phellodendron chinense (%), R 2 is the correlation coefficient.

[0140] According to the design of this experiment, the following conclusions can be drawn:

[0141] (1) Flexural strength, flexural stiffness and flexural modulus are three potential mechanical indicators that can accurately and objectively characterize the texture of Phellodendron chinense.

[0142] (2) The measured basic parameters of Phellodendron chinense show that Phellodendron chinense is a brittle material. The brittleness of Phellodendron chinense decreases with the increase of water content.

[0143] (3) The established three-point bending finite element model is reliable and can successfully simulate the traditional manual inspection of the texture of cork with an error within 20%.

[0144] (4) The flexural strength, flexural stiffness and flexural modulus of Phellodendron chinense ranged from 6.99MPa to 16.33MPa, 56.8N.mm2 to 130.41N.mm2 and 60.93MPa to 147.56MPa, respectively. The water content has a significant effect on the flexural strength and flexural modulus of PCC, but has little effect on its flexural stiffness. The study found that the relationship between mechanical properties and moisture is linear. A 5% increase in moisture content will lead to a decrease in flexural strength of about 2.44MPa, a decrease in flexural modulus of about 22.17MPa, and a decrease in flexural stiffness of about 19.36N.mm2.

[0145] 1) The present invention is objective, accurate and scientific in characterizing the texture of Phellodendron chinense, avoiding the subjectivity and ambiguity of human sensory characterization, and comprehensively expounds the mechanical properties of Phellodendron chinense in physical property testing in combination with mechanical property analysis to scientifically characterize its texture.

[0146] 2) The present invention predicts the moisture content of Phellodendron chinense based on its texture characteristics. Compared with the traditional drying method, this method can quickly and accurately infer the moisture content of Phellodendron chinense, which is of great significance for ensuring the quality of Phellodendron chinense and other traditional Chinese medicines during the storage process.

[0147] 3) The application of the characterization method of the texture of Phellodendron chinense in the quality assurance of the present invention is not limited to predicting the moisture content during storage, but can also be applied to other links such as harvesting, transportation and processing. It is of great significance to improve the efficiency of Phellodendron chinense harvesting, reduce damage during transportation, and standardize operations during processing.

Claims

1. A method for characterizing the texture of Phellodendron chinense based on mechanical properties analysis and its application in predicting moisture content, characterized in that The mechanical properties of Phellodendron chinense were analyzed by using the texture analyzer and finite element method, and a texture characterization method of Phellodendron chinense was established and applied to the prediction of its moisture content. The method includes the following steps: Step 1: Determine the physical property test suitable for detecting the texture of Phellodendron chinense and the parameters for characterizing its texture; Step 2: preparing cork samples for physical property testing; Step 3: Determine the basic parameters for three-point bending finite element simulation; Step 4: Establish a finite element model for testing the physical properties of cork; Step 5: Verify the reliability of the finite element model; Step 6: Use finite element simulation to establish the relationship between the texture parameters and moisture content of Phellodendron chinense.

2. The method for characterizing the texture of Phellodendron chinense and its application in predicting moisture content according to claim 1, characterized in that: In step 1, the physical property test for detecting the texture of Phellodendron chinense was determined to be a three-point bending test based on the traditional manual bending test. Based on the material mechanics hypothesis, the mechanical properties of Phellodendron chinense were analyzed during the three-point bending process, and the parameters characterizing its texture were determined to be bending strength, bending stiffness and bending modulus.

3. The method for characterizing the texture of Phellodendron chinense and its application in predicting moisture content according to claim 2, characterized in that: In step 2, in order to reduce the influence of shear force on the three-point bending of Phellodendron, the length of the Phellodendron sample was determined to be 40 mm. Considering that the maximum moisture content of Phellodendron in the hygroscopic range is about 25%, a total of 5 Phellodendron samples with moisture content levels were prepared (0% to 5%, 5% to 10%, 10% to 15%, 15% to 20%, 20% to 25%).

4. The method for characterizing the texture of Phellodendron chinense and its application in predicting the moisture content as claimed in claim 3, characterized in that: In step three, the basic parameters of Phellodendron chinense for constructing a three-point bending finite element model include size (length, thickness, width), density, failure stress, failure strain, elastic modulus, and Poisson's ratio.

5. The method for characterizing the texture of Phellodendron chinense and its application in predicting the moisture content as claimed in claim 4, characterized in that: In step 4, Abaqus simulation technology was used to establish a three-point bending model of cork with different moisture contents.

6. The method for characterizing the texture of Phellodendron chinense and its application in predicting the moisture content as claimed in claim 5, characterized in that: In step 5, the mechanical behavior of Phellodendron chinense under the real physical property test and the simulated physical property test, the probe loading force-displacement curve and the parameters characterizing the texture are compared. If the above results are consistent or the error is less than 20%, it proves that the finite element model is reliable and can be used for moisture content prediction. The three-point bending loading speed, loading displacement speed and loading displacement are set to 10mm / min, 5mm / min and 10mm respectively along the Y-axis, and the contact trigger force between the loading probe and Phellodendron chinense is set to 0.5N.

7. The method for characterizing the texture of Phellodendron chinense and its application in predicting the moisture content as claimed in claim 6, characterized in that: In step six, three parallel experiments were conducted on three-point bending tests of Phellodendron chinense with different moisture contents (2.5%, 7.5%, 12.5%, 17.5%, and 22.5%), and linear regression was performed between the moisture content of Phellodendron chinense and the parameters characterizing the texture of Phellodendron chinense.

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