Metal wire mesh mechanical analysis method considering inter-wire slippage

Abstract

The invention discloses a metal wire mesh mechanical analysis method considering inter-wire slippage, which comprises the following steps of: obtaining a minimum repetitive unit coordinate of a metal wire mesh through a model parameter of the metal wire mesh, and establishing a geometry model of the metal wire mesh based on three-dimensional modeling software according to a minimum repetitive unit coordinate point matrix; according to the obtained geometry model, defining contact parameters of the wire mesh, dividing grids, and setting analysis conditions and boundary conditions; solving the geometry model by adopting a time integration method to obtain a deformed metal wire mesh geometry model; and carrying out extraction and arrangement on the solved stress deformation result. Compared with an approximately equivalent film model of an existing wire mesh, the mechanical analysis method of the wire mesh is more accurate in calculation, and the result is closer to the actual working condition; the overall strain of the wire mesh can be calculated, the deformation conditions of meshes at different positions under the load condition can be obtained, and the method has guiding significance for design weaving and actual laying work of the wire mesh.

Description

Technical Field

[0001] The invention belongs to the technical field of mechanical analysis of metal wire mesh for deployable mesh antennas, and in particular relates to a mechanical analysis method of metal wire mesh taking inter-wire slip into consideration. Background Art

[0002] Modern deployable antennas are required to be larger and larger in size to meet the increasing signal transmission capacity requirements. Among the different types of deployable antennas, the antenna with a peripheral truss structure has the largest diameter, and the wire mesh is a structure laid on the truss cable net. After the antenna is deployed to form a parabola, it relies on the wire mesh to gather and reflect electromagnetic waves. Therefore, the performance of the wire mesh directly determines the performance of the deployable antenna.

[0003] During the antenna deployment process, the wire mesh is subjected to tension from all directions. The intertwined metal wires will first produce relative friction and slippage after being subjected to force, and then intertwine and produce elastic-plastic deformation. The displacement between the metal wires and the deformation of the material itself will cause the shape and size of the mesh to change, which will eventually affect the electrical performance of the antenna. Therefore, it is necessary to analyze the mechanical properties of the flexible metal wire mesh.

[0004] At present, there are very few studies on the mechanical properties of flexible metal mesh. In the past, some people used the equivalent film model for mechanical analysis, but the accuracy was poor. Due to the lack of relevant theoretical basis, engineering units can only process the finished metal mesh and then conduct experimental analysis to obtain feedback data, which is costly and inefficient. Therefore, there is an urgent need for a method that can predict the mechanical properties of metal mesh quickly and accurately at low cost. Summary of the invention

[0005] The purpose of the present invention is to provide a metal wire mesh mechanical analysis method taking into account the slippage between wires, thereby solving the problem that the friction, slippage and hooking between the metal wires after tension deformation cannot be considered when using the existing wire mesh approximation with a porous film model for analysis, thereby improving the analysis accuracy.

[0006] The technical solution adopted by the present invention is: a mechanical analysis method of a metal wire mesh considering inter-wire slippage, establishing an assembly model of the metal wire mesh, and considering the friction, slippage and collusion between the metal wires during the deformation process of the wire mesh under stress, specifically comprising the following steps:

[0007] Step 1: Obtain the minimum repeating unit coordinates of the wire mesh through the model parameters of the wire mesh, and then establish a geometric model of the wire mesh based on the three-dimensional modeling software SolidWorks according to the minimum repeating unit coordinate point matrix;

[0008] Step 2: Based on the geometric model obtained in step 1, define the contact parameters of the wire mesh, divide the mesh, and set the analysis conditions and boundary conditions;

[0009] Step 3, using the time integration method to solve the geometric model to obtain the deformed metal wire mesh geometric model;

[0010] Step 4: Extract and organize the stress and deformation results obtained in step 3.

[0011] The present invention is also characterized in that:

[0012] Step 1: The model parameters of the wire mesh include: the mesh structure P, the coil height b, the row spacing w, the wire diameter d and the coil inclination angle α.

[0013] Step 2 is as follows:

[0014] Step 2.1, determine the density, Young's modulus and Poisson's ratio of the wire mesh material;

[0015] Step 2.2, comb segmenting the metal wire mesh, wherein the comb segmentation is to divide a whole metal wire into a plurality of small segments, each segment having and only having one complete coil;

[0016] Step 2.3, set the contact parameters between the geometric bodies generated after comb segmentation, define the contact surface generated by comb segmentation as binding, define the contact surface between the sub-components generated after different comb segmentation in the geometric body as friction; define the friction coefficient as 0.2; considering that the speed of applying force is very slow, define the dynamic coefficient as 1;

[0017] Step 2.4, meshing the geometric model using eight-node hexahedral mesh units;

[0018] Step 2.5: Set the analysis conditions and determine the minimum time step according to formula (2.1):

[0019]

[0020] Where f is the safety factor, which is usually 0.9 for quasi-static analysis, h is the minimum unit size of the grid obtained in step 2.3, and c is the wave speed of sound in the wire mesh;

[0021] Step 2.6: Set the boundary conditions of the wire mesh, completely constrain the edge wires, and apply loads to the wire mesh in layers.

[0022] Step 3 is as follows:

[0023] Step 3.1, set the total duration of the analysis process and divide the total duration into j time sub-steps;

[0024] Step 3.2: Based on the mesh units divided in step 2, the applied loads and boundary conditions, first analyze the resultant external force on the mesh nodes. The resultant external force F on each mesh node is i It can be determined according to formula (3.1):

[0025]

[0026] Among them, f is the friction force, F1 is the external force on the grid node, and the friction force f is obtained according to formula (3.2):

[0027] f=μF p (3.2)

[0028] μ is the relative friction coefficient between steel and steel, which is set to 0.2. p is the normal pressure between the contact surfaces;

[0029] Step 3.3: After obtaining the net external force on the grid nodes, solve the acceleration on each grid node at time k according to equation (3.3), k = 1, 2, ..., j:

[0030]

[0031] In the formula, represents the acceleration at time k, It represents the total external force on the grid node at time k, m is the mass of the grid node, and λ is the dynamic coefficient;

[0032] Step 3.4: Integrate the acceleration at time k on the time scale. The length of the integration is the length of a time substep. According to formula (3.4), the velocity of the grid node at time k is obtained:

[0033]

[0034] In the formula, represents the speed at time k, Represents the speed at time k-1, with an initial value of 0;

[0035] Step 3.5: Integrate the velocity at time k on the time scale. The length of the integration is the length of a time substep. According to formula (3.5), the displacement of the grid node at time k is obtained:

[0036]

[0037] In the formula, x i k represents the displacement at time k, x i k-1 Represents the displacement at time k-1, with an initial value of 0;

[0038] Step 3.6, continue to iterate the process of steps 3.2-3.4. When the time reaches the specified end time or the velocity and acceleration of all mesh nodes are 0, the solution process ends and the deformed wire mesh geometry model is output.

[0039] Step 4 is as follows:

[0040] Step 4.1: Use the probe to obtain the coordinates of the edge points on each side of the mesh, and make a difference to the specified node coordinates. Calculate the strain value of a single mesh according to the strain calculation formula (4.1).

[0041]

[0042] In the formula, ε xi represents the x-strain of the ith mesh, x li 'Indicates the x-coordinate value of the left endpoint of the mesh after the change, x ri ' represents the x-coordinate value of the right end point of the mesh after the change, x li Indicates the x-coordinate value of the left endpoint of the mesh before it changes, x ri Indicates the x-coordinate value of the right end point of the mesh before it changes; ε yi represents the y-strain of the ith mesh, y bi ' represents the y-coordinate value of the lower endpoint of the mesh after the change, y ui ' represents the y-coordinate value of the mesh endpoint after the change, y bi Indicates the y-coordinate value of the lower endpoint of the mesh before it changes, y ui Indicates the y-coordinate value of the mesh endpoint before it changes;

[0043] Then calculate the average strain of all meshes according to formula (4.2):

[0044]

[0045] Where Ave.ε x represents the average strain in the x-direction, Ave.ε y represents the average strain in the y direction, and n is the number of meshes;

[0046] The deformation of all mesh holes of the wire mesh can be obtained through the calculation results of formulas (4.1) and (4.2).

[0047] The beneficial effects of the present invention are:

[0048] The present invention provides a mechanical analysis method for metal mesh that takes into account inter-wire slippage. The method uses a more accurate metal mesh geometric model and a pre-processing method that is closer to the actual situation for analysis. Traditionally, a bonding model is always used to analyze the stress and deformation of metal mesh, which is approximately equivalent to a film with holes. Therefore, the friction, slippage and collusion between the metal wires after the mesh is stretched and deformed cannot be considered, and the analysis accuracy is poor. Compared with the existing analysis method, the results obtained by the present invention are more accurate and closer to the actual working conditions.

[0049] The invention discloses a mechanical analysis method for metal wire mesh taking into account inter-wire slippage, which can not only calculate the overall strain of the wire mesh, but also obtain different deformation conditions of mesh holes at different positions under load, thus filling the gap in local analysis of the overall model of the wire mesh and providing guidance for the design, weaving and actual laying of the metal wire mesh. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic flow chart of a method for mechanical analysis of a metal wire mesh taking inter-wire slip into consideration according to the present invention;

[0051] Figure 2 It is a schematic diagram of a single comb bar of the present invention after being divided into coil units;

[0052] Figure 3 is a structural diagram of a metal wire mesh assembled in Example 2 of the present invention;

[0053] Figure 4 This is the mesh shape of Example 2 of the present invention after being deformed by a longitudinal load. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0055] Example 1

[0056] The present invention considers the wire mesh mechanical analysis method of inter-wire slippage, and the process is as follows Figure 1 The specific steps are as follows:

[0057] Step 1: Obtain the minimum repeating unit coordinates of the wire mesh through the model parameters of the wire mesh, and then establish a geometric model of the wire mesh based on the three-dimensional modeling software SolidWorks according to the minimum repeating unit coordinate point matrix;

[0058] Step 2: Based on the geometric model obtained in step 1, define the contact parameters of the wire mesh, divide the mesh, and set the analysis conditions and boundary conditions;

[0059] Step 3, using the time integration method to solve the geometric model to obtain the deformed metal wire mesh geometric model;

[0060] Step 4: Extract and organize the stress and deformation results obtained in step 3.

[0061] Example 2

[0062] The present invention discloses a metal wire mesh mechanical analysis method considering inter-wire slippage, and the specific implementation process is as follows:

[0063] Step 1.1: Set the model parameters of the wire mesh as follows: the wire mesh structure P is a one-through-one-hole warp satin structure, the coil height b is 1 cm, the wire diameter d is 0.05 mm, the knitting machine number E is 7, the number of needle back yarns n is 1, and the wire mesh inclination angle α is 20°. The minimum repeating unit coordinates of the wire mesh are obtained using the technology "Automated Modeling of Typical Warp Knitted Wire Meshes" proposed by Zhang Han et al. in 2020;

[0064] Step 1.2: According to the minimum repeating unit coordinate point matrix, a geometric model of the wire mesh is established based on the 3D modeling software SolidWorks. Figure 2 As shown in the figure, the metal wire mesh is divided into comb bars according to the coil positions; finally, it is assembled to form Figure 3 The 3×3 wire mesh geometry model is exported as Parasolid.x_t format;

[0065] Step 1.3: Pre-process the geometric model: Select the explicit dynamics module in the WB interface of the finite element analysis software, define the name of the material used for the wire mesh as nickel-plated stainless steel, and the density is 7900kg / m 3 , Young's modulus is 210 GPa, Poisson's ratio is 0.3, and then the defined material is assigned to all geometries;

[0066] Step 2: Based on the geometric model obtained in step 1, define the contact parameters of the wire mesh, divide the mesh, and set the analysis conditions and boundary conditions;

[0067] Step 2.1: Define different contact types: Select the contact surface generated by comb segmentation in step 1.3, that is, the contact surface between the outer cylindrical surface of the wires and the connection surface of the normal of the elliptical surface between the units, and define it as binding, and define the contact behavior as symmetry; select the contact surface between the sub-components generated by different comb segmentation in the geometry, define it as friction, and define the contact behavior as symmetry; the friction coefficient between the metal wires is defined as 0.2; considering that the speed of applying force is very slow, the dynamic amplification factor is defined as 1;

[0068] Step 2.2: Select all geometric bodies and use explicit linear mesh for meshing. The side length of the mesh is set to be the same as the diameter d of the wire mesh, which is 0.05 mm. Use the adaptive mesh option to make the meshing of the coils denser and the meshing of the intersections sparser. After the meshing is completed, check the meshing quality.

[0069] Step 2.3: Set up the analysis. First, determine the minimum time step according to formula (2.1):

[0070]

[0071] Where f is the safety factor, which is usually 0.9 for quasi-static analysis, h is the minimum unit size of the divided grid, and c is the wave speed of sound in the wire mesh;

[0072] Step 2.4: Set the wire mesh boundary conditions, fully constrain the edge wires, and apply loads to the wire mesh in layers.

[0073] The loading method is set as follows: set full constraints on the leftmost comb bar and the bottom layer of coils; because the interference removal model is used, there is no contact between the metal wires. In order to allow the force to be evenly transmitted layer by layer in the metal mesh, it is necessary to apply loads to the metal mesh in layers. For the load in the X direction, set the corresponding geometry to all the geometry on the selected comb bar, and define the load size in the X direction as +F in the form of components. 2i (i=1,2,...,n), repeat several times until force is applied to all combs except the comb at the left edge; for the load in the Y direction, considering the characteristics of the mesh form, that is, the coil density in the Y direction is twice the coil density in the X direction, the corresponding geometric body is set to all geometric bodies in a certain layer of the metal mesh, and the load size in the Y direction is defined as +F in the component form i (i=1,2,...,n), repeat the steps several times until force is applied to coils of all layers except the coils at the bottom edge; for a 3×3 wire mesh geometry model with a side length of 9mm, a uniformly distributed load of 5N / m can be equivalent to a load of 0.45N on each comb bar in the X direction and a load of 0.225N on each layer of coils in the Y direction.

[0074] Step 3: Solve the geometric model using the time integration method to obtain the deformed metal wire mesh geometric model;

[0075] Let the solver start working and output the results. When analyzing the unidirectional strain in the X direction, the constraints and loads in the Y direction need to be suppressed. Similarly, when analyzing the unidirectional strain in the Y direction, the constraints and loads in the X direction need to be suppressed. After the analysis is completed, the deformed wire mesh geometry model is obtained.

[0076] Step 4, post-process the solution results: check the deformation results after the analysis, use the probe to obtain the specified node coordinates, and obtain the coordinate return values ​​shown in Table 1; Marking point 1 and marking point 2 are the points with the maximum horizontal distance on the mesh, and marking point 3 and marking point 4 are the points with the maximum vertical distance on the mesh;

[0077] Table 1 Result coordinate values ​​returned by the probe

[0078]

[0079] Subtract the corresponding node coordinates and calculate the change of a single mesh according to the strain calculation formula:

[0080] Then calculate the average strain of all meshes;

[0081] like Figure 4 The figure shows the mesh shape after being deformed by the longitudinal load in Example 2 of the present invention. The deformation of all meshes of the metal wire mesh can be obtained through the change of a single mesh and the average strain of all meshes. The applied load is adjusted in increments of 5N / m, that is, 0.45N is increased in the X direction each time and 0.225N is increased in each layer in the Y direction. After solving again, step 4 is repeated, and finally the deformation of the mesh under a load of 5N / m to 50N / m is obtained as shown in Table 2:

[0082] Table 2 Strain of metal wire mesh

[0083]

[0084] The above simulation experiments show that the present invention can effectively analyze the shape of the metal wire mesh after being deformed by force.

[0085] Example 3

[0086] Based on Example 2, step 3 is as follows:

[0087] Step 3.1, set the total duration of the analysis process and divide the total duration into j time sub-steps;

[0088] Step 3.2: Based on the mesh units divided in step 2, the applied loads and boundary conditions, first analyze the resultant external force on the mesh nodes. The resultant external force F on each mesh node is i It can be determined according to formula (3.1):

[0089]

[0090] Among them, f is the friction force, F1 is the external force on the grid node, and the friction force f is obtained according to formula (3.2):

[0091] f=μF p (3.2)

[0092] μ is the relative friction coefficient between steel and steel, which is set to 0.2. p is the normal pressure between the contact surfaces;

[0093] Step 3.3: After obtaining the net external force on the grid nodes, solve the acceleration on each grid node at time k according to equation (3.3), k = 1, 2, ..., j:

[0094]

[0095] In the formula, represents the acceleration at time k, represents the total external force on the grid node at time k, m is the mass of the grid node, and λ is the dynamic coefficient;

[0096] Step 3.4: Integrate the acceleration at time k on the time scale. The length of the integration is the length of a time substep. According to formula (3.4), the velocity of the grid node at time k is obtained:

[0097]

[0098] In the formula, represents the speed at time k, Represents the speed at time k-1, with an initial value of 0;

[0099] Step 3.5: Integrate the velocity at time k on the time scale. The length of the integration is the length of a time substep. According to formula (3.5), the displacement of the grid node at time k is obtained:

[0100]

[0101] In the formula, x i k represents the displacement at time k, x i k-1 Represents the displacement at time k-1, with an initial value of 0;

[0102] Step 3.6, continue to iterate the process of steps 3.2-3.4. When the time reaches the specified end time or the velocity and acceleration of all mesh nodes are 0, the solution process ends and the deformed wire mesh geometry model is output.

[0103] Step 4 is as follows:

[0104] Step 4.1: Use the probe to obtain the coordinates of the edge points on each side of the mesh, and make a difference to the specified node coordinates. Calculate the strain value of a single mesh according to the strain calculation formula (4.1).

[0105]

[0106] In the formula, ε xi represents the x-strain of the ith mesh, x li 'Indicates the x-coordinate value of the left endpoint of the mesh after the change, x ri ' represents the x-coordinate value of the right end point of the mesh after the change, x li Indicates the x-coordinate value of the left endpoint of the mesh before it changes, x ri Indicates the x-coordinate value of the right end point of the mesh before it changes; ε yi represents the y-strain of the ith mesh, y bi ' represents the y-coordinate value of the lower endpoint of the mesh after the change, y ui ' represents the y-coordinate value of the mesh endpoint after the change, y bi Indicates the y-coordinate value of the lower endpoint of the mesh before it changes, y ui Indicates the y-coordinate value of the mesh endpoint before it changes;

[0107]

[0108] In the formula, ε xi represents the x-strain of the ith mesh, x li 'Indicates the x-coordinate value of the left endpoint of the mesh after the change, x ri ' represents the x-coordinate value of the right end point of the mesh after the change, x li Indicates the x-coordinate value of the left endpoint of the mesh before it changes, x ri Indicates the x-coordinate value of the right end point of the mesh before it changes; ε yi represents the y-strain of the ith mesh, y bi ' represents the y-coordinate value of the lower endpoint of the mesh after the change, y ui ' represents the y-coordinate value of the mesh endpoint after the change, y bi Indicates the y-coordinate value of the lower endpoint of the mesh before it changes, y ui Indicates the y-coordinate value of the mesh endpoint before it changes;

[0109] Then calculate the average strain of all meshes

[0110]

[0111] Where Ave.ε x represents the average strain in the x-direction, Ave.ε y represents the average strain in the y direction, and n is the number of meshes.

[0112] The existing analysis of the force of the wire mesh mostly adopts an implicit solution method, which requires solving equations. However, friction and slip are nonlinear problems, which often lead to the equations not being able to obtain convergent solutions. Therefore, conventional analysis methods often simplify the overall model into a film with holes, that is, setting the metal wires to be in bonding contact, ignoring the friction, slip and collusion between the metal wires. The time integration method used in the present invention does not need to solve equations, but only needs to calculate the grid node position at the next moment from the state at the previous moment. Because there is no problem that the analytical solution of the equation may not converge (no need to solve the equation), nonlinear factors such as friction and sliding between the metal wires can be considered.

[0113] In the present invention, the friction coefficient is 0.2, which is the maximum static friction coefficient between steel and steel. The friction force follows Coulomb's law: f=μF, where f is the friction force, μ is the friction coefficient, and F is the positive pressure in the normal direction of the contact surface. The dynamic coefficient is defined as 1 because the speed of applying the force is very slow. The parameters set in the above pre-processing part are used in the finite element analysis calculation process.

Claims

1. A method for mechanical analysis of metal wire mesh considering inter-wire slippage, characterized in that: The specific steps are as follows: Step 1: Obtain the minimum repeating unit coordinates of the wire mesh through the model parameters of the wire mesh, and then establish a geometric model of the wire mesh based on the three-dimensional modeling software SolidWorks according to the minimum repeating unit coordinate point matrix; Step 2: Based on the geometric model obtained in step 1, define the contact parameters of the wire mesh, divide the mesh, and set the analysis conditions and boundary conditions; Step 3: Solve the geometric model using the time integration method to obtain the simulation analysis result; Step 4: Extract and organize the stress and deformation results obtained from the simulation analysis in step 3.

2. According to the method for mechanical analysis of metal wire mesh taking into account inter-wire slippage as claimed in claim 1, the model parameters of the metal wire mesh in step 1 include: The wire mesh’s organizational structure P, coil height b, row spacing w, wire diameter d and coil inclination angle α.

3. The method for mechanical analysis of metal wire mesh considering inter-wire slippage according to claim 1, characterized in that: Step 2 is as follows: Step 2.1, determine the density, Young's modulus and Poisson's ratio of the wire mesh material; Step 2.2, comb segmenting the metal wire mesh, wherein the comb segmentation is to divide a whole metal wire into a plurality of small segments, each segment having and only having one complete coil; Step 2.3, set the contact parameters between the geometric bodies generated after comb segmentation, define the contact surface generated by comb segmentation as binding, define the contact surface between the sub-components generated after different comb segmentation in the geometric body as friction; the friction coefficient is defined as 0.2; the dynamic coefficient is defined as 1; Step 2.4, meshing the geometric model using eight-node hexahedral mesh units; Step 2.5: Set the analysis conditions and determine the minimum time step according to formula (2.1): Where f is the safety factor, which is usually 0.9 for quasi-static analysis, h is the minimum unit size of the grid obtained in step 2.3, and c is the wave speed of sound in the wire mesh; Step 2.6: Set the boundary conditions of the wire mesh, completely constrain the edge wires, and apply loads to the wire mesh in layers.

4. The method for mechanical analysis of metal wire mesh considering inter-wire slippage according to claim 3, characterized in that: Step 3 is as follows: Step 3.1, set the total duration of the analysis process and divide the total duration into j time sub-steps; Step 3.2: Based on the mesh units divided in step 2, the applied loads and boundary conditions, first analyze the resultant external force on the mesh nodes. The resultant external force F on each mesh node is i It can be determined according to formula (3.1): Among them, f is the friction force, F1 is the external force on the grid node, and the friction force f is obtained according to formula (3.2): f=μF p (3.2) μ is the relative friction coefficient between steel and steel, which is set to 0.

2. p is the normal pressure between the contact surfaces; Step 3.3: After obtaining the net external force on the grid node, solve the acceleration on each grid node at time k according to equation (3.3), k = 1, 2, ... j, In the formula, represents the acceleration at time k, represents the total external force on the grid node at time k, m is the mass of the grid node, and λ is the dynamic coefficient; Step 3.4: Integrate the acceleration at time k on the time scale. The length of the integration is the length of a time substep. According to formula (3.4), the velocity of the grid node at time k is obtained: In the formula, represents the speed at time k, Represents the speed at time k-1, with an initial value of 0; Step 3.5: Integrate the velocity at time k on the time scale. The length of the integration is the length of a time substep. According to formula (3.5), the displacement of the grid node at time k is obtained: In the formula, x i k represents the displacement at time k, x i k-1 Represents the displacement at time k-1, with an initial value of 0; Step 3.6, continue to iterate the process of steps 3.2-3.

4. When the time reaches the specified end time or the velocity and acceleration of all mesh nodes are 0, the solution process ends and the deformed wire mesh geometry model is output.

5. The metal wire mesh mechanical analysis method considering inter-wire slippage according to claim 1, characterized in that: Step 4 is as follows: Step 4.1: Use the probe to obtain the coordinates of the edge points on each side of the mesh, and make a difference to the specified node coordinates. Calculate the strain value of a single mesh according to the strain calculation formula (4.1). In the formula, ε xi represents the x-strain of the ith mesh, x li 'Indicates the x-coordinate value of the left endpoint of the mesh after the change, x ri ' represents the x-coordinate value of the right end point of the mesh after the change, x li Indicates the x-coordinate value of the left endpoint of the mesh before it changes, x ri Indicates the x-coordinate value of the right endpoint of the mesh before it changes; ε yi represents the y-strain of the ith mesh, y bi ' represents the y-coordinate value of the lower endpoint of the mesh after the change, y ui ' represents the y-coordinate value of the mesh endpoint after the change, y bi Indicates the y-coordinate value of the lower endpoint of the mesh before it changes, y ui Indicates the y-coordinate value of the mesh endpoint before it changes; Then calculate the average strain of all meshes according to formula (4.2): Where Ave.ε x represents the average strain in the x-direction, Ave.ε y represents the average strain in the y direction, and n is the number of meshes; The deformation of all mesh holes of the wire mesh can be obtained through the calculation results of formulas (4.1) and (4.2).

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