CN113378427A - Calculation method for evaluating wind load fracture resistance of branches and trunks of arbor - Google Patents
Calculation method for evaluating wind load fracture resistance of branches and trunks of arbor Download PDFInfo
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Abstract
The invention provides a calculation method for evaluating the wind load fracture resistance of an arbor branch, which comprises the steps of firstly establishing an arbor finite element model by means of Creo and Hypermesh, establishing a wind domain model by using ABAQUS, then leading the two models into ABAQUS to be assembled in the same model, establishing a wind-arbor model, secondly setting material parameters, analysis steps, interaction and boundary conditions of wind and arbor branches, thirdly setting a damage standard of the arbor model, and finally comparing the mechanical parameters in a stress cloud chart after the model is loaded: the maximum tensile stress, the maximum compressive stress, the maximum bending stress and the maximum shearing stress are in the size relationship with the wind load resistant fracture standard of the branches and the trunks of the arbor under the action of wind load, the wind load resistant fracture property of the branches and the trunks of the arbor is judged, and a decision basis is provided for manual regulation and control of the field arbor.
Description
Technical Field
The invention relates to a calculation method for evaluating wind load fracture resistance of branches and trunks of arbors, and belongs to the technical field of vegetation community regulation and control.
Background
The branches and trunks of trees are often broken and damaged under the action of wind load, which causes serious loss to the vegetation ecosystem of China. Due to the limitations of the field and the existing equipment, the wind load fracture resistance of the branches and the trunks of the arbor can not be directly measured in the field.
Disclosure of Invention
The invention aims to provide a calculation method for evaluating the wind load fracture resistance of branches and trunks of arbors, which judges the wind load fracture resistance of the branches and trunks of arbors by comparing the magnitude relation between the mechanical parameters such as maximum tensile stress, maximum compressive stress, maximum bending stress, maximum shearing stress and the like in a stress cloud picture after model loading and the fracture damage standard of the branches and trunks of arbors under the action of wind load, and provides decision basis for manual regulation and control of field arbors.
In order to achieve the technical features, the invention is realized as follows: a calculation method for evaluating the wind load fracture resistance of branches and trunks of arbors comprises the following steps:
firstly, establishing an initial geometric model of a tree branch;
dividing a finite element grid of the branches and the trunks of the arbor;
step three, establishing a wind domain model;
determining parameters of the branches and the trunks of the trees and the wind material;
step five, assembling a wind-arbor branch finite element model;
step six, defining wind-arbor branch finite element model analysis step and field output;
defining interaction of wind-arbor branch finite element models;
step eight, defining boundary conditions of a wind-arbor branch finite element model;
step nine, submitting a work task and performing solution calculation;
step ten, extracting a calculation result of the wind-arbor branch finite element model;
step eleven, defining the wind-load fracture damage standard of the branches and the trunks of the arbor;
and step twelve, evaluating the wind load fracture resistance of the branches and the trunks of the arbor.
In the first step, an initial geometric model of the tree trunk is established, the geometric model is established in a Cartesian coordinate system and comprises a tree trunk part and a branch part of the tree, and the method comprises the following specific steps:
step 1.1: creating an arbor trunk: in the business software Creo, a top plane and a right plane are selected, and a central axis Z is created; selecting a top plane for sketching, and creating a line segment L with the height H along the positive direction of the Y axis by taking coordinates (0,0,0) as an origin1Selecting and determining; selecting a line segment L1Scanning and mixing; clicking a section 1 in the section option, sketching, creating a circle with a top diameter r by taking the coordinate center of the interface as the center of the circle, and selecting and determining; inserting the section 2 into the section option, sketching, creating a circle with the bottom diameter R by taking the coordinate center of the section as the center of a circle, and selecting and determining; selecting and determining again to finish the creation of the tree trunk;
step 1.2: creating tree branches z1: selecting a front plane for sketching, and creating a line segment a in any direction by taking the coordinate center of the interface as an origin1(ii) a With a1Creating a plane x with reference to the central axis Z1(ii) a Selection of x1Sketching on the plane in a line segment L1From bottom to top h1To create a line segment l1Line segment l1An included angle theta (0 DEG) with the central axis Z<θ<180 deg.), selection is determined; selecting line segment l1And performing scanning mixing: clicking section 1 in the section options, sketching, taking the coordinate center of the interface as the circle center, and creating a top diameter r11Selecting and determining the circle of (1); inserting the section 2 into the section option, sketching, taking the coordinate center of the section as the center of a circle, and creating a base diameter R12Selecting and determining the circle of (1) and selecting and determining again; completing the creation of a single branch of the arbor;
step 1.3: creating multiple branches of the same layer of the arbor: selection of branches z1Performing array, selecting the array type as an axis, selecting a central axis Z as an array axis, selecting the number of array members as n, n as a natural number, and selecting and determining the angle between the members as 360 degrees/n to complete the establishment of a plurality of branches on the same layer of the arbor;
step 1.4: creating multilayer branches of the arbor: repeating the step 1.2 and the step 1.3 to complete the creation of the multilayer branches of the arbor;
step 1.5: and (3) leading out an arbor model: and storing as Parasolid (. x _ t) format file.
And in the second step, the arbor branch finite element mesh is divided, wherein the arbor branch finite element mesh is divided by meshes of an arbor trunk part and a branch part, and the method specifically comprises the following steps:
step 2.1: entering into Hypermesh software, selecting abaqus and explore and ok in User Profiles; importing an arbor model Parasolid (. x _ t) format file in Hypermesh;
step 2.2: creating a component named 2 d;
step 2.3.1: cutting the branch part: selecting solid edges in the Geom, trimwith ines, selecting solid in the bounding lines, selecting a geometric model, selecting lines, selecting a boundary line at the junction of a branch and a trunk in the geometric model, selecting trim and finishing the cutting of the branches of the arbor;
step 2.3.2: replication of the 2d surfaces of the top and bottom ends of the branch parts: selecting a mask in a main interface Tool, selecting a solid type, selecting a solid part except the branch grid needing to be divided, selecting a mask, selecting an orgnaize in the interface, selecting a surf type, selecting 2d by a dest component, selecting surfaces of the top end and the bottom end of a branch in the main interface, selecting copy, and finishing copying the surfaces of the top end and the bottom end 2d of the branch part;
step 2.3.3: cutting 2d surfaces of the branch parts: selecting a mask in a main interface Tool, selecting a solid type, selecting a solid part needing to divide a branch grid, selecting the mask, selecting a quick edge in a main interface Geom, selecting an add point on line, selecting a 2d surface boundary line at the bottom end of a branch in the interface, adding 4 points, equally dividing the 2d surface boundary line into 4 curves, selecting a split surf-node, selecting a point in the boundary line and an opposite angle point, selecting the split surf-line, and selecting a line segment generated by connecting any one of the other two points in the boundary line with the opposite angle point; selecting the last point and the line segment generated in the previous operation, repeating the step 2.3.3, and cutting the 2d surface of the top end of the branch;
step 2.3.4: dividing the 2 d-surface grids of the branch part: selecting a 2D tool of a main interface, selecting automesh, selecting a 2D surface at the bottom end of a branch, and selecting mesh; adding 4 seeds on the free boundary of the bottom surface of the branch on average, wherein the number of the seeds on the free boundary is 2; selecting elemtype in mesh style, selecting qusds only, selecting set all, selecting mesh, repeating the step 2.3.4, and completing mesh division of the 2d surface at the top end of the branch;
step 2.3.5: generation of single branch 3d mesh: selecting a 3D tool in a main interface, selecting a solid map, selecting a linear solid, selecting elements to a drag, selecting a 2D grid at the bottom end of a branch in the interface, selecting elements to a match, selecting a 2D grid at the top end of the branch, selecting an upper parameter-density as m, selecting a grid density as required, selecting a mesh, and generating a branch 3D grid; selecting 2d component in the left side of the interface, selecting delete, and generating a single branch 3d grid.
Step 2.3.6: generating multiple branch grids on the same layer of the arbor: selecting position in the tool in the main interface, selecting elems types, selecting the tree branch 3D grid generated in the step 5, and selecting the upper side N at the bottom end of the tree branch in the from1Upper side N of top of branch2Lower side N of the top end of the branch3Selecting the upper side N at the bottom ends of three points of branches of other branches which are not divided into grids on the same layer in the to1Upper side N of top of branch2Lower side N of the top end of the branch3Clicking elements, clicking elements again, selecting duplicate, selecting original comp, selecting position, repeating the step 2.3.6, and creating the rest branch grids of the same layer;
step 2.3.7: generation of branch part 3d mesh: repeating step 2.2 and steps 2.3.1-2.3.6;
step 2.4.1: cutting the trunk part: step 2.3, cutting the trunk part after all the branch parts are cut;
step 2.4.2: replication of the 2d faces of the top and bottom ends of the trunk section: selecting a mask in a main interface Tool, selecting a solid type, selecting a solid part except for the trunk grid to be divided, selecting a mask, selecting an orgnaize in an interface, selecting a surf type, selecting 2d by a dest component, selecting the top end and the bottom end of a trunk in the main interface, selecting copy, and finishing the copying of the top end and the bottom end 2d surfaces of the trunk part;
step 2.4.3: trunk part 2d face cut: selecting a mask in a main interface Tool, selecting a solid type, selecting a solid part needing to divide a trunk grid, selecting the mask, selecting a quick edge in a main interface Geom, selecting an add point on line, selecting a 2d surface boundary line at the bottom end of a trunk in the interface, adding 4 points, equally dividing the 2d surface boundary line into 4 curves, selecting a split surf-node, selecting a point in the boundary line and an opposite angle point, selecting the split surf-line, and selecting a line segment generated by connecting any one of the other two points in the boundary line with the opposite angle point; selecting a line segment generated by connecting the last point with the diagonal point, repeating the step 2.4.3, and finishing cutting the 2d surface at the top end of the trunk;
step 2.4.4: trunk part 2d face grid division: selecting a 2D tool of a main interface, selecting automesh, selecting a 2D surface of the bottom end of a trunk, and selecting mesh; adding 4 seeds on the free boundary of the bottom surface of the trunk on average, wherein the number of the seeds on the free boundary is 2; selecting elemtype in mesh style, selecting qusds only, selecting set all, selecting mesh, repeating the step 2.4.4, and generating a 2d grid at the top end of the trunk;
step 2.4.5: generation of the trunk portion 3d mesh: selecting a 3D tool in a main interface, selecting a solid map, selecting a linear solid, selecting elements to a drag, selecting a 2D grid at the bottom end of a trunk in the interface, selecting elements to a match, selecting a 2D grid at the top end of the trunk, selecting an upper parameters-density as a, selecting a grid density as required, selecting a mesh, and generating a 3D grid of the trunk; selecting 2d component in the left side of the interface, and selecting delete;
step 2.5: branch part component: creating a new component, renamed as z; selecting origanze in a main interface, selecting elements, selecting 3D grids of all branch parts, selecting z from dest components in the origanze interface, selecting move, and finishing the creation of branch part components;
step 2.6: trunk part component: creating a new component, renamed as g; selecting origanze in a main interface, selecting elements, selecting 3D grids of all trunk parts, selecting g from dest components in the origanze interface, selecting move, selecting the rest components except the components named z and g, and selecting delete;
step 2.7.1: exporting the arbor inp file: selecting an export solution deck in the main interface, selecting a file, determining a storage path, wherein the file format is inp and the storage name is zg;
step 2.7.2: export of the stem part inp file: selecting z-component in the model, selecting delete, leaving g-component, repeating the step 2.7.1, and saving the name g;
step 2.7.3: exporting the branch part inp file: selecting g-component, and selecting delete; selecting an import solution deck in the main interface, selecting a saved zg. inp file, selecting g in a model, selecting delete and leaving z-component, repeating the step 2.7.1, and saving as z.
Establishing a wind domain model in the third step, and establishing a length, width and height b in a Han version abaqus1、b2、 b3The three-dimensional Euler solid model is used as a wind domain, and the created wind domain range is larger than the size range of the arbor; in the grid module, the selected object is an Euler component, q is input in the size control of the seed component, the size control is close to the size of the arbor grid, the selection is determined, the grid is divided for the component, and the selection is yes.
Determining the material parameters of branches and stems of trees and wind, and inputting the density rho of trees in the material module of ABAQUS1Young's modulus E1Poisson ratio μ1(ii) a The flowing air forms wind, and the air density rho is set2The equation of state is of the Us-Up type, where c0Is 340, s is 0, Gamma00, viscosity medium dynamic viscosity 1.711 x 10-5Pa · s, the material parameters are assigned to the wind field and the arbor, respectively.
Assembling a wind-arbor branch finite element model, importing an arbor inp file from an ABAQUS component module, creating an example in an assembly module, and importing a wind domain and arbor model; creating a reference point S at the center of the bottom end of a tree trunk1Creating a reference point S at the center of the bottom surface of the wind field2Translating the trunk and branch model to make S1And S2And (4) overlapping.
Defining wind-arbor branch finite element model analysis step and field output, analyzing step and field output, creating analysis step, selecting step-1 and making program type be power displayFormula (b) for a time period1/v1，v1Is the set wind speed; f-output-1 is created in the field output, and the output variables are S selected in the stress, namely the stress component and the invariant.
Defining interaction of a wind-arbor branch finite element model, creating universal contact in an interaction module, and setting interaction attributes as defaults; creating binding constraints, selecting the main surface type as a surface, selecting the area type as a grid, selecting an arbor trunk, and completing selection; selecting nodes on the connection surface of the branch and the trunk, finishing selection and selecting and determining in editing constraints, wherein the surface type is a node area, the area type is a grid, and the nodes are selected from the connection surface of the branch and the trunk.
Defining boundary conditions of a wind-arbor branch finite element model, creating a load in a load module, selecting gravity, continuing selection, creating a gravity acceleration g in a downward direction, and finishing creating the load; creating an initial boundary condition v-in, selecting speed and continuing selection, selecting the region type as geometry, selecting the surface of a wind domain according to wind direction, completing selection, selecting step-1 in the boundary condition of v-in, and setting the initial speed v according to the wind direction and coordinates1(ii) a Creating a boundary condition flow-in, wherein the types of the boundary condition flow-in are other, the types of the boundary condition flow-in are Euler boundaries, the selection is continued, the selection area is geometric, the inflow boundary surface of wind is selected according to the wind direction, the selection is completed, and the flow type is free inflow in a popped editing boundary condition frame; creating a boundary condition flow-out, selecting continuous boundary, selecting geometric region, selecting an outflow boundary surface of wind according to the wind direction, and finishing selection, wherein the flow type is zero-pressure outflow in a popped editing boundary condition frame; establishing an initial boundary condition, wherein the type is mechanics, the type is symmetrical/antisymmetric/completely fixed, selecting to continue, selecting the type of the area as a grid, selecting the bottom surface of the arbor model, completing selection, selecting to completely fix in a popped editing boundary condition frame, and selecting to determine.
Creating an analysis task in an operation module, and submitting solution calculation;
extracting a calculation result of the wind-arbor branch finite element model, which specifically comprises the following steps: extracting the maximum tensile stress, the maximum compressive stress, the maximum bending stress and the maximum shearing stress of the arbor in the movement process under the action of wind load in a visualization module;
defining a wind-load fracture damage standard of an arbor branch, selecting tensile, bending and shearing strength of the arbor in 'the physical and mechanical properties of the wood of the main tree species in China' as a criterion, taking the influence of knots on the quality of the arbor into consideration, taking 85% of the four strengths as the wind-load fracture damage standard of the arbor, and evaluating the wind-load fracture resistance of the arbor under the action of wind load;
evaluating the wind load fracture resistance of the branches and the trunks of the arbor, and defining the damage criterion of the arbor model, wherein the criterion is as follows:
when the maximum compressive stress of the trunk or the branch of the arbor is greater than the standard of compressive strength, or the maximum bending stress of the trunk or the branch of the arbor is greater than the standard of bending strength, or the maximum shear stress of the trunk or the branch of the arbor is greater than the standard of shear strength, or the maximum tensile stress of the trunk or the branch of the arbor is greater than the standard of tensile strength, judging that the trunk or the branch of the arbor is subjected to stress failure, and breaking failure is carried out under wind load;
and when the maximum compressive stress of the trunk or the branch of the arbor is smaller than the compressive strength standard in the standard, or the maximum bending stress of the trunk or the branch of the arbor is smaller than the bending strength standard, or the maximum shear stress of the trunk or the branch of the arbor is smaller than the shear strength standard, or the maximum tensile stress of the trunk or the branch of the arbor is smaller than the tensile strength standard, judging that the trunk or the branch of the arbor is not subjected to stress damage, and not subjected to fracture damage under wind load.
The invention has the following beneficial effects:
1. the wind-arbor branch model in the calculation method integrates field, wind speed and arbor branch geometric simplified dimension, and an arbor branch wind load fracture resistance destructive test is developed on the calculation model, so that the technical bottleneck that the arbor branch wind load fracture resistance is difficult to directly evaluate in the field is broken through.
2. By adjusting the diameters of the two ends of the branches of the arbor, the wind speed and other related parameters in the calculation model, different site and wind speed conditions can be simulated and calculated, and the practicability is high.
3. The animation generated by the calculation model result records the movement process of the arbor under the action of wind load in the whole process, and the authenticity and the accuracy of the evaluation conclusion are enhanced.
Drawings
The invention is further illustrated by the following figures and examples.
FIG. 1 is a flow chart of a calculation method for evaluating the wind load fracture resistance of a tree branch according to the invention;
FIG. 2 is a schematic diagram of a finite element model of a tree limb according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a finite element mesh of tree branches according to an embodiment of the present invention;
FIG. 4 is a schematic view of a wind domain model of an embodiment of the present invention;
FIG. 5 is a schematic view of a wind-arbor model of an embodiment of the present invention;
table 1 shows the wind resistance criteria of the trees according to the embodiment of the present invention.
Table 2 is the material properties of the wind for an embodiment of the invention;
table 3 shows arbor material parameters for examples of embodiments of the present invention;
table 4 is a boundary condition of an embodiment example of the present invention;
table 5 shows the maximum stress of the arbor under wind load according to the embodiment of the present invention;
table 6 shows the wind resistance criteria of the trees according to the embodiment of the present invention.
Detailed Description
Embodiments of the present invention will be further described with reference to the accompanying drawings.
Example 1:
as shown in fig. 1, a calculation method for evaluating the wind load fracture resistance of a tree branch comprises the following steps: firstly, establishing an initial geometric model of a tree branch;
dividing a finite element grid of the branches and the trunks of the arbor;
step three, establishing a wind domain model;
determining parameters of the branches and the trunks of the trees and the wind material;
step five, assembling a wind-arbor branch finite element model;
step six, defining wind-arbor branch finite element model analysis step and field output;
defining interaction of wind-arbor branch finite element models;
step eight, defining boundary conditions of a wind-arbor branch finite element model;
step nine, submitting a work task and performing solution calculation;
step ten, extracting a calculation result of the wind-arbor branch finite element model;
step eleven, defining the wind-load fracture damage standard of the branches and the trunks of the arbor;
and step twelve, evaluating the wind load fracture resistance of the branches and the trunks of the arbor.
As a further preferable scheme of the calculation method for evaluating the wind load fracture resistance of the branches and the trunks of the arbor, the first step is to establish an initial geometric model of the branches and the trunks of the arbor, wherein the geometric model is established in a cartesian coordinate system and comprises an arbor trunk part and a branch part, and the specific steps are as follows:
step 1.1: creating an arbor trunk: in the business software Creo, a top plane and a right plane are selected, and a central axis Z is created; the top plane is selected for sketching, and a line segment L with the height of 13m is created in the positive direction of the Y axis by taking coordinates (0,0,0) as an origin1Selecting and determining; selecting a line segment L1Scanning and mixing; clicking a section 1 in the section option, sketching, creating a circle with the top diameter of 0.01m by taking the coordinate center of the interface as the center of the circle, and selecting and determining; inserting a section 2 into the section option, sketching, creating a circle with the bottom diameter of 0.178m by taking the coordinate center of the section as the center of the circle, and selecting and determining; and selecting and determining again to finish the creation of the tree trunk.
Step 1.2: creating tree branches z1: selecting a front plane for sketching, and creating a line segment a in any direction by taking the coordinate center of the interface as an origin1(ii) a With a1Creating a plane x with reference to the central axis Z1(ii) a Selection of x1Sketching on the plane in a line segment L1From bottom to toph1To create a line segment l1Line segment l1An included angle theta (0 DEG) with the central axis Z<θ<180 deg.), selection is determined; selecting line segment l1And performing scanning mixing: clicking section 1 in the section options, sketching, taking the coordinate center of the interface as the circle center, and creating a top diameter r11Selecting and determining the circle of (1); inserting the section 2 into the section option, sketching, taking the coordinate center of the section as the center of a circle, and creating a base diameter R12Selecting and determining the circle of (1) and selecting and determining again; completing the creation of a single branch of the arbor; the distance between the branches of the arbor is 1m from bottom to top, and the bottom diameter is decreased progressively by 0.01 m.
Step 1.3: creating multiple branches of the same layer of the arbor: selection of branches z1And performing array, selecting the array type as an axis, selecting a central axis Z as an array axis, selecting the number of array members as n, n as a natural number, and selecting and determining the angle between the members as 360 degrees/n to complete the establishment of the multiple branches on the same layer of the arbor.
Step 1.4: creating multilayer branches of the arbor: repeating the step 1.2 and the step 1.3 to complete the creation of the multilayer branches of the arbor; the arbor finite element model completed through the above steps is shown in fig. 2, and the reduced dimensions are shown in table 1.
TABLE 1 arbor wind resistance criteria
Step 1.5: and (3) leading out an arbor model: and storing as Parasolid (. x _ t) format file.
As a further preferable scheme of the calculation method for evaluating the wind load fracture resistance of the branches and the trunks of the arbor, in the step 2, a finite element mesh of the branches and the trunks of the arbor is divided, wherein the finite element mesh comprises a trunk part and a branch part of the arbor, and the mesh division specifically comprises the following steps:
step 2.1: entering into Hypermesh software, selecting abaqus and explore and ok in User Profiles; and importing a arbor model Parasolid (. x _ t) format file in Hypermesh.
Step 2.2: create component, named 2 d.
Step 2.3.1: cutting the branch part: selecting solid edge in Geom, selecting trim with lines, selecting solid in bounding lines, selecting geometric model, selecting lines, selecting boundary line at junction of branch and trunk in geometric model, selecting trim, and finishing cutting of arbor branch.
Step 2.3.2: replication of the 2d surfaces of the top and bottom ends of the branch parts: selecting a mask in a main interface Tool, selecting a solid type, selecting a solid part except the solid part needing to divide the branch grid, selecting a mask, selecting an orgnaize in the interface, selecting a surf type, selecting 2d by a dest component, selecting the top end and the bottom end of a branch in the main interface, selecting a copy, and finishing the copying of the top end and the bottom end 2d surfaces of the branch part.
Step 2.3.3: cutting 2d surfaces of the branch parts: selecting a mask in a main interface Tool, selecting a solid type, selecting a solid part needing to divide a branch grid, selecting the mask, selecting a quick edge in a main interface Geom, selecting an add point on line, selecting a 2d surface boundary line at the bottom end of a branch in the interface, adding 4 points, equally dividing the 2d surface boundary line into 4 curves, selecting a split surf-node, selecting a point in the boundary line and an opposite angle point, selecting the split surf-line, and selecting a line segment generated by connecting any one of the other two points in the boundary line with the opposite angle point; and (4) selecting the last point and the line segment generated in the previous operation, repeating the step 2.3.3, and cutting the 2d surface of the top end of the branch.
Step 2.3.4: dividing the 2 d-surface grids of the branch part: selecting a 2D tool of a main interface, selecting automesh, selecting a 2D surface at the bottom end of a branch, and selecting mesh; adding 4 seeds on the free boundary of the bottom surface of the branch on average, wherein the number of the seeds on the free boundary is 2; selecting elemtype in mesh style, selecting qusds only, selecting set all, selecting mesh, repeating the step 2.3.4, and completing mesh division of the 2d surface at the top end of the branch.
Step 2.3.5: generation of single branch 3d mesh: selecting a 3D tool in a main interface, selecting a solid map, selecting a linear solid, selecting elements to a drag, selecting a 2D grid at the bottom end of a branch in the interface, selecting elements to a match, selecting a 2D grid at the top end of the branch, selecting an upper parameter-density of 10, and selecting a mesh according to the required grid density to generate a branch 3D grid; selecting 2d component in the left side of the interface, selecting delete, and generating a single branch 3d grid.
Step 2.3.6: generating multiple branch grids on the same layer of the arbor: selecting position in the tool in the main interface, selecting elems types, selecting the tree branch 3D grid generated in the step 5, and selecting the upper side N at the bottom end of the tree branch in the from1Upper side N of top of branch2Lower side N of the top end of the branch3Selecting the upper side N at the bottom ends of three points of branches of other branches which are not divided into grids on the same layer in the to1Upper side N of top of branch2Lower side N of the top end of the branch3Click elements, click elements again, select duplicate, select original comp, select position, repeat step 2.3.6, create the rest of the same level branch grid.
Step 2.3.7: generation of branch part 3d mesh: and repeating the step 2.2 and the step 2.3.1-2.3.6.
Step 2.4.1: cutting the trunk part: and 2.3, cutting the trunk part after all the branch parts are cut.
Step 2.4.2: replication of the 2d faces of the top and bottom ends of the trunk section: selecting a mask in a main interface Tool, selecting a solid type, selecting a solid part needing to divide a trunk grid, selecting a mask, selecting an orgnaize in an interface, selecting a surf type, selecting 2d by a dest component, selecting the top end and the bottom end of a trunk in the main interface, selecting copy, and finishing the copying of the top end and the bottom end 2d surfaces of the trunk part.
Step 2.4.3: trunk part 2d face cut: selecting a mask in a main interface Tool, selecting a solid type, selecting a solid part needing to divide a trunk grid, selecting the mask, selecting a quick edge in a main interface Geom, selecting an add point on line, selecting a 2d surface boundary line at the bottom end of a trunk in the interface, adding 4 points, equally dividing the 2d surface boundary line into 4 curves, selecting a split surf-node, selecting a point in the boundary line and an opposite angle point, selecting the split surf-line, and selecting a line segment generated by connecting any one of the other two points in the boundary line with the opposite angle point; selecting a line segment generated by connecting the last point with the diagonal point, repeating the step 2.4.3, and finishing cutting the 2d surface at the top end of the trunk;
step 2.4.4: trunk part 2d face grid division: selecting a 2D tool of a main interface, selecting automesh, selecting a 2D surface of the bottom end of a trunk, and selecting mesh; adding 4 seeds on the free boundary of the bottom surface of the trunk on average, wherein the number of the seeds on the free boundary is 2; selecting elemtype in mesh style, selecting qusds only, selecting set all, selecting mesh, repeating the step 2.4.4, and generating a 2d grid at the top end of the trunk;
step 2.4.5: generation of the trunk portion 3d mesh: selecting a 3D tool in a main interface, selecting a solid map, selecting a linear solid, selecting elements to a drag, selecting a 2D grid at the bottom end of a trunk in the interface, selecting elements to a match, selecting a 2D grid at the top end of the trunk, selecting an upper parameters-density of 87, selecting a mesh according to the required grid density, and generating a 3D grid of the trunk; selecting 2d component in the left side of the interface, and selecting delete;
step 2.5: branch part component: creating a new component, renamed as z; selecting origanze in a main interface, selecting elements, selecting 3D grids of all branch parts, selecting z from dest components in the origanze interface, selecting move, and finishing the creation of branch part components;
step 2.6: trunk part component: creating a new component, renamed as g; selecting origanze in a main interface, selecting elements, selecting 3D grids of all trunk parts, selecting g from dest components in the origanze interface, selecting move, selecting the rest components except the components named z and g, and selecting delete; through the above steps, the division of the arbor mesh is completed, as shown in fig. 3.
Step 2.7.1: exporting the arbor inp file: selecting an export solution deck in the main interface, selecting a file, determining a storage path, wherein the file format is inp and the storage name is zg;
step 2.7.2: export of the stem part inp file: selecting z-component in the model, selecting delete, leaving g-component, repeating the step 2.7.1, and saving the name g;
step 2.7.3: exporting the branch part inp file: selecting g-component, and selecting delete; selecting an import solution deck in the main interface, selecting a saved zg. inp file, selecting g in a model, selecting delete and leaving z-component, repeating the step 2.7.1, and saving as z.
As a further preferable scheme of the calculation method for evaluating the wind-load fracture resistance of the branches and the trunks of the arbor, a wind domain model is established in the third step, a three-dimensional Euler entity model with the length, width and height of 7.5m, 5m and 22.75m is established in a Han version abaqus as a wind domain, and the established wind domain range is larger than the size range of the arbor; in the grid module, the selected object is an Euler component, 0.15 is input in the size control of the seed component, the size control is close to the size of the arbor grid, the selection is determined, the component is selected to divide the grid, and the selection is yes. Through the above steps, the establishment of the wind domain is completed, as shown in fig. 4.
As a further preferable scheme of the calculation method for evaluating the wind-load fracture resistance of the branches and the trunks of the arbor, in the step 4, the material parameters of the branches and the trunks of the arbor and the wind are determined, and the arbor density of 3.24g/cm is input into a material module of ABAQUS3Young's modulus 9.2Gpa, poisson's ratio 0.37; the flowing air forms wind, and the air density is set to be 1.29g/cm3The equation of state is of the Us-Up type, where c0Is 340, s is 0, Gamma00, viscosity medium dynamic viscosity 1.711 x 10-5Pa · s, the material parameters are assigned to the wind field and the arbor, respectively. Specific properties of the wind and arbor materials are shown in tables 2 and 3.
TABLE 2 Material Properties of the wind
Note: 1. the air tightness of the watch is selected from Baidu encyclopedia;
2. the dynamic viscosity is extracted from calculation of aerodynamic viscosity and dynamic viscosity at different temperatures;
3、C0is the intercept of the Us-Up curve, S is the slope dependence of the Us-Up curveThe constant, Gamma0, is the Gruneisen Gamma constant, Us stress wave propagation velocity, Up particle velocity.
TABLE 3 arbor Material parameters
Note: the arbor density is taken as the base density.
As a further preferable scheme of the calculation method for evaluating the wind-load fracture resistance of the tree branches, in the step 5, a wind-tree branch finite element model is assembled, a tree inp file is imported from an ABAQUS component module, an example is created in an assembly module, and a wind domain and a tree model are imported; creating a reference point S at the center of the bottom end of a tree trunk1Creating a reference point S at the center of the bottom surface of the wind field2Translating the trunk and branch model to make S1And S2And (4) overlapping. The wind-arbor model is shown in fig. 5.
As a further preferable scheme of the calculation method for evaluating the wind load fracture resistance of the branches and the trunks of the arbor, the step 6 is to define a wind-arbor branch finite element model analysis step and field output, analyze the step and the field output, establish an analysis step, select step-1, select a program type of a power display type, time length of 0.35s and wind speed of 20 m/s; f-output-1 is created in the field output, and the output variables are S selected in the stress, namely the stress component and the invariant.
As a further preferable scheme of the calculation method for evaluating the wind-load fracture resistance of the tree branches, in the step 7, the interaction of a wind-tree branch finite element model is defined, in an interaction module, a universal contact is created, and the interaction attribute is set as a default; creating binding constraints, selecting the main surface type as a surface, selecting the area type as a grid, selecting an arbor trunk, and completing selection; selecting nodes on the connection surface of the branch and the trunk, finishing selection and selecting and determining in editing constraints, wherein the surface type is a node area, the area type is a grid, and the nodes are selected from the connection surface of the branch and the trunk.
The invention relates to a calculation method for evaluating the wind load fracture resistance of branches and trunks of arborsIn the step 8, defining boundary conditions of the wind-arbor branch finite element model, creating load in the load module, selecting gravity, selecting continuous, and creating the gravitational acceleration 9.8m/s in the downward direction2Completing the creation of the load; establishing an initial boundary condition v-in, wherein the type is mechanics, selecting speed, continuing selection, selecting the type of an area as geometry, selecting the surface of a wind area according to wind direction, completing selection, selecting step-1 in the boundary condition of v-in, and setting the initial speed to be 20m/s according to the wind direction and coordinates; creating a boundary condition flow-in, wherein the types of the boundary condition flow-in are other, the types of the boundary condition flow-in are Euler boundaries, the selection is continued, the selection area is geometric, the inflow boundary surface of wind is selected according to the wind direction, the selection is completed, and the flow type is free inflow in a popped editing boundary condition frame; creating a boundary condition flow-out, selecting continuous boundary, selecting geometric region, selecting an outflow boundary surface of wind according to the wind direction, and finishing selection, wherein the flow type is zero-pressure outflow in a popped editing boundary condition frame; establishing an initial boundary condition, wherein the type is mechanics, the type is symmetrical/antisymmetric/completely fixed, selecting to continue, selecting the type of the area as a grid, selecting the bottom surface of the arbor model, completing selection, selecting to completely fix in a popped editing boundary condition frame, and selecting to determine. The boundary conditions are shown in table 4.
TABLE 4 boundary conditions
As a further preferable scheme of the calculation method for evaluating the wind-load fracture resistance of the branches and the trunks of the arbor, in the step 9, an analysis task is created in the operation module, and solution calculation is submitted.
As a further preferable scheme of the calculation method for evaluating the wind load fracture resistance of the branches and the trunks of the arbor, in the step 10, the calculation result of the wind-arbor branch finite element model is extracted, which specifically comprises the following steps: the method comprises the steps of extracting maximum tensile stress, maximum compressive stress, maximum bending stress and maximum shearing stress of a tree in a movement process under the action of wind load in a visualization module. The maximum tensile stress, maximum compressive stress, maximum bending stress and maximum shear stress of the arbor under wind load are shown in table 5.
TABLE 5 stress values of arbors under wind load
As a further preferable scheme of the calculation method for evaluating the wind-load fracture resistance of the branches and the trunks of the arbor, in the step 11, a wind-load fracture damage standard of the branches and the trunks of the arbor is defined, tensile, compression, bending and shear strengths of the arbor in the physical and mechanical properties of wood of Chinese main tree species are selected as criteria, the influence of knots on the quality of the arbor is considered, 85% of the four strengths are taken as the wind-load fracture damage standard of the arbor, and the wind-load fracture resistance of the arbor under the action of wind load is evaluated; the arbor wind resistance criteria are shown in table 6.
TABLE 6 arbor wind resistance criteria
As a further preferable scheme of the calculation method for evaluating the wind load fracture resistance of the branches and the stems of the trees, in the step 12, the wind load fracture resistance of the branches and the stems of the trees is evaluated, and the branches of the trees are judged to be subjected to shear failure only if the maximum shear stress in all maximum stress values of the branches of the trees is greater than the shear strength standard; and the maximum compressive stress, the maximum bending stress, the maximum shearing stress and the maximum tensile stress of the tree trunk are all smaller than the corresponding strength in the wind-resistant design criterion, and the tree trunk is judged to be not subjected to stress failure. In conclusion, under the action of the wind speed of 20m/s, the branches of the arbor are sheared and broken, and the trunk is not broken.
Claims (10)
1. A calculation method for evaluating the wind load fracture resistance of branches and trunks of arbors is characterized by comprising the following steps:
firstly, establishing an initial geometric model of a tree branch;
dividing a finite element grid of the branches and the trunks of the arbor;
step three, establishing a wind domain model;
determining parameters of the branches and the trunks of the trees and the wind material;
step five, assembling a wind-arbor branch finite element model;
step six, defining wind-arbor branch finite element model analysis step and field output;
defining interaction of wind-arbor branch finite element models;
step eight, defining boundary conditions of a wind-arbor branch finite element model;
step nine, submitting a work task and performing solution calculation;
step ten, extracting a calculation result of the wind-arbor branch finite element model;
step eleven, defining the wind-load fracture damage standard of the branches and the trunks of the arbor;
and step twelve, evaluating the wind load fracture resistance of the branches and the trunks of the arbor.
2. The calculation method for evaluating the wind load fracture resistance of the branches and the stems of the arbor according to claim 1, which is characterized in that: in the first step, an initial geometric model of the tree trunk is established, the geometric model is established in a Cartesian coordinate system and comprises a tree trunk part and a branch part of the tree, and the method comprises the following specific steps:
step 1.1: creating an arbor trunk: in the business software Creo, a top plane and a right plane are selected, and a central axis Z is created; selecting a top plane for sketching, and creating a line segment L with the height H along the positive direction of the Y axis by taking coordinates (0,0,0) as an origin1Selecting and determining; selecting a line segment L1Scanning and mixing; clicking a section 1 in the section option, sketching, creating a circle with a top diameter r by taking the coordinate center of the interface as the center of the circle, and selecting and determining; inserting the section 2 into the section option, sketching, creating a circle with the bottom diameter R by taking the coordinate center of the section as the center of a circle, and selecting and determining; selecting and determining again to finish the creation of the tree trunk;
step 1.2: creating tree branches z1: selecting a front plane for sketching, and creating a line segment a in any direction by taking the coordinate center of the interface as an origin1(ii) a With a1Creating a plane x with reference to the central axis Z1(ii) a Selection of x1Sketching on the plane in a line segment L1From bottom to top h1To create a line segment l1Line segment l1An included angle theta (0 DEG) with the central axis Z<θ<180 deg.), selection is determined; selecting line segment l1And performing scanning mixing: clicking section 1 in the section options, sketching, taking the coordinate center of the interface as the circle center, and creating a top diameter r11Selecting and determining the circle of (1); inserting the section 2 into the section option, sketching, taking the coordinate center of the section as the center of a circle, and creating a base diameter R12Selecting and determining the circle of (1) and selecting and determining again; completing the creation of a single branch of the arbor;
step 1.3: creating multiple branches of the same layer of the arbor: selection of branches z1Performing array, selecting the array type as an axis, selecting a central axis Z as an array axis, selecting the number of array members as n, n as a natural number, and selecting and determining the angle between the members as 360 degrees/n to complete the establishment of a plurality of branches on the same layer of the arbor;
step 1.4: creating multilayer branches of the arbor: repeating the step 1.2 and the step 1.3 to complete the creation of the multilayer branches of the arbor;
step 1.5: and (3) leading out an arbor model: and storing as Parasolid (. x _ t) format file.
3. The calculation method for evaluating the wind load fracture resistance of the branches and the stems of the arbor according to claim 1, which is characterized in that: and in the second step, the arbor branch finite element mesh is divided, wherein the arbor branch finite element mesh is divided by meshes of an arbor trunk part and a branch part, and the method specifically comprises the following steps:
step 2.1: entering into Hypermesh software, selecting abaqus and explore and ok in User Profiles; importing an arbor model Parasolid (. x _ t) format file in Hypermesh;
step 2.2: creating a component named 2 d;
step 2.3.1: cutting the branch part: selecting solid edge in Geom, selecting trim with lines, selecting solid in bounding lines, selecting geometric models, selecting lines, selecting boundary line at junction of branches and trunks in geometric models, selecting trim, and finishing cutting of branches of trees;
step 2.3.2: replication of the 2d surfaces of the top and bottom ends of the branch parts: selecting a mask in a main interface Tool, selecting a solid type, selecting a solid part except the branch grid needing to be divided, selecting a mask, selecting an orgnaize in the interface, selecting a surf type, selecting 2d by a dest component, selecting surfaces of the top end and the bottom end of a branch in the main interface, selecting copy, and finishing copying the surfaces of the top end and the bottom end 2d of the branch part;
step 2.3.3: cutting 2d surfaces of the branch parts: selecting a mask in a main interface Tool, selecting a solid type, selecting a solid part needing to divide a branch grid, selecting the mask, selecting a quick edge in a main interface Geom, selecting an add point on line, selecting a 2d surface boundary line at the bottom end of a branch in the interface, adding 4 points, equally dividing the 2d surface boundary line into 4 curves, selecting a split surf-node, selecting a point in the boundary line and an opposite angle point, selecting the split surf-line, and selecting a line segment generated by connecting any one of the other two points in the boundary line with the opposite angle point; selecting the last point and the line segment generated in the previous operation, repeating the step 2.3.3, and cutting the 2d surface of the top end of the branch;
step 2.3.4: dividing the 2 d-surface grids of the branch part: selecting a 2D tool of a main interface, selecting automesh, selecting a 2D surface at the bottom end of a branch, and selecting mesh; adding 4 seeds on the free boundary of the bottom surface of the branch on average, wherein the number of the seeds on the free boundary is 2; selecting an elem type in the mesh style, selecting qusds only, selecting set all, selecting mesh, and repeating the step 2.3.4 to complete the grid division of the 2d surface at the top end of the branch;
step 2.3.5: generation of single branch 3d mesh: selecting a 3D tool in a main interface, selecting a solid map, selecting a linear solid, selecting elements to a drag, selecting a 2D grid at the bottom end of a branch in the interface, selecting elements to a match, selecting a 2D grid at the top end of the branch, selecting an upper parameter-density as m, selecting a grid density as required, selecting a mesh, and generating a branch 3D grid; selecting 2d component in the left side of the interface, selecting delete, and generating a single branch 3d grid.
Step 2.3.6: generating multiple branch grids on the same layer of the arbor: selecting position in the tool in the main interface, selecting elems types, selecting the tree branch 3D grid generated in the step 5, and selecting the upper side N at the bottom end of the tree branch in the from1Upper side N of top of branch2Lower side N of the top end of the branch3Selecting the upper side N at the bottom ends of three points of branches of other branches which are not divided into grids on the same layer in the to1Upper side N of top of branch2Lower side N of the top end of the branch3Clicking elements, clicking elements again, selecting duplicate, selecting original comp, selecting position, repeating the step 2.3.6, and creating the rest branch grids of the same layer;
step 2.3.7: generation of branch part 3d mesh: repeating step 2.2 and steps 2.3.1-2.3.6;
step 2.4.1: cutting the trunk part: step 2.3, cutting the trunk part after all the branch parts are cut;
step 2.4.2: replication of the 2d faces of the top and bottom ends of the trunk section: selecting a mask in a main interface Tool, selecting a solid type, selecting a solid part except for the trunk grid to be divided, selecting a mask, selecting an orgnaize in an interface, selecting a surf type, selecting 2d by a dest component, selecting the top end and the bottom end of a trunk in the main interface, selecting copy, and finishing the copying of the top end and the bottom end 2d surfaces of the trunk part;
step 2.4.3: trunk part 2d face cut: selecting a mask in a main interface Tool, selecting a solid type, selecting a solid part needing to divide a trunk grid, selecting the mask, selecting a quick edge in a main interface Geom, selecting an add point on line, selecting a 2d surface boundary line at the bottom end of a trunk in the interface, adding 4 points, equally dividing the 2d surface boundary line into 4 curves, selecting a split surf-node, selecting a point in the boundary line and an opposite angle point, selecting the split surf-line, and selecting a line segment generated by connecting any one of the other two points in the boundary line with the opposite angle point; selecting a line segment generated by connecting the last point with the diagonal point, repeating the step 2.4.3, and finishing cutting the 2d surface at the top end of the trunk;
step 2.4.4: trunk part 2d face grid division: selecting a 2D tool of a main interface, selecting automesh, selecting a 2D surface of the bottom end of a trunk, and selecting mesh; adding 4 seeds on the free boundary of the bottom surface of the trunk on average, wherein the number of the seeds on the free boundary is 2; selecting an elem type in the mesh style, selecting qusds only, selecting set all, selecting mesh, repeating the step 2.4.4, and generating a tree trunk top 2d grid;
step 2.4.5: generation of the trunk portion 3d mesh: selecting a 3D tool in a main interface, selecting a solid map, selecting a linear solid, selecting elements to a drag, selecting a 2D grid at the bottom end of a trunk in the interface, selecting elements to a match, selecting a 2D grid at the top end of the trunk, selecting an upper parameters-density as a, selecting a grid density as required, selecting a mesh, and generating a 3D grid of the trunk; selecting 2d component in the left side of the interface, and selecting delete;
step 2.5: branch part component: creating a new component, renamed as z; selecting origanze in a main interface, selecting elements, selecting 3D grids of all branch parts, selecting z from dest components in the origanze interface, selecting move, and finishing the creation of branch part components;
step 2.6: trunk part component: creating a new component, renamed as g; selecting origanze in a main interface, selecting elements, selecting 3D grids of all trunk parts, selecting g from dest components in the origanze interface, selecting move, selecting the rest components except the components named z and g, and selecting delete;
step 2.7.1: exporting the arbor inp file: selecting an export solution deck in the main interface, selecting a file, determining a storage path, wherein the file format is inp and the storage name is zg;
step 2.7.2: export of the stem part inp file: selecting z-component in the model, selecting delete, leaving g-component, repeating the step 2.7.1, and saving the name g;
step 2.7.3: exporting the branch part inp file: selecting g-component, and selecting delete; selecting an import solution deck in the main interface, selecting a saved zg. inp file, selecting g in a model, selecting delete and leaving z-component, repeating the step 2.7.1, and saving as z.
4. The calculation method for evaluating the wind load fracture resistance of the branches and the stems of the arbor according to claim 1, wherein: establishing a wind domain model in the third step, and establishing a length, width and height b in a Han version abaqus1、b2、b3The three-dimensional Euler solid model is used as a wind domain, and the created wind domain range is larger than the size range of the arbor; in the grid module, the selected object is an Euler component, q is input in the size control of the seed component, the size control is close to the size of the arbor grid, the selection is determined, the grid is divided for the component, and the selection is yes.
5. The calculation method for evaluating the wind load fracture resistance of the branches and the stems of the arbor according to claim 1, wherein: determining the material parameters of branches and stems of trees and wind, and inputting the density rho of trees in the material module of ABAQUS1Young's modulus E1Poisson ratio μ1(ii) a The flowing air forms wind, and the air density rho is set2The equation of state is of the Us-Up type, where c0Is 340, s is 0, Gamma00, viscosity medium dynamic viscosity 1.711 x 10-5Pa · s, the material parameters are assigned to the wind field and the arbor, respectively.
6. The calculation method for evaluating the wind load fracture resistance of the branches and the stems of the arbor according to claim 1, wherein: assembling a wind-arbor branch finite element model, importing an arbor inp file from an ABAQUS component module, creating an example in an assembly module, and importing a wind domain and arbor model; creating a reference point S at the center of the bottom end of a tree trunk1Creating a reference point S at the center of the bottom surface of the wind field2Translating the trunk and branch model to make S1And S2And (4) overlapping.
7. The calculation method for evaluating the wind load fracture resistance of the branches and the stems of the arbor according to claim 1, wherein: defining wind-arbor branch finite element model analysis step and field output, analyzing step and field output, creating analysis step, selecting step-1, program type is power display type and time length is b1/v1，v1Is the set wind speed; f-output-1 is created in the field output, and the output variables are S selected in the stress, namely the stress component and the invariant.
8. The calculation method for evaluating the wind load fracture resistance of the branches and the stems of the arbor according to claim 1, wherein: defining interaction of a wind-arbor branch finite element model, creating universal contact in an interaction module, and setting interaction attributes as defaults; creating binding constraints, selecting the main surface type as a surface, selecting the area type as a grid, selecting an arbor trunk, and completing selection; selecting nodes on the connection surface of the branch and the trunk, finishing selection and selecting and determining in editing constraints, wherein the surface type is a node area, the area type is a grid, and the nodes are selected from the connection surface of the branch and the trunk.
9. The calculation method for evaluating the wind load fracture resistance of the branches and the stems of the arbor according to claim 1, wherein: defining boundary conditions of a wind-arbor branch finite element model, creating a load in a load module, selecting gravity, continuing selection, creating a gravity acceleration g in a downward direction, and finishing creating the load; creating an initial boundary condition v-in, selecting speed and continuing selection, selecting the region type as geometry, selecting the surface of a wind domain according to wind direction, completing selection, selecting step-1 in the boundary condition of v-in, and setting the initial speed v according to the wind direction and coordinates1(ii) a Creating a boundary condition flow-in, wherein the types of the boundary condition flow-in are other, the types of the boundary condition flow-in are Euler boundaries, the selection is continued, the selection area is geometric, the inflow boundary surface of wind is selected according to the wind direction, the selection is completed, and the flow type is free inflow in a popped editing boundary condition frame; creating a boundary condition flow-out, selecting continuous boundary, selecting geometric region, selecting an outflow boundary surface of wind according to the wind direction, and finishing selection, wherein the flow type is zero-pressure outflow in a popped editing boundary condition frame; creating initial boundary conditions, selecting the type of mechanics, the type of symmetry/antisymmetry/complete fixation, continuing, selecting the type of region as grid, selecting the bottom surface of arbor model, finishing selection, and popping upIn the edit boundary condition box of (1), the selection is completely fixed and the selection is determined.
10. The calculation method for evaluating the wind load fracture resistance of the branches and the stems of the arbor according to claim 1, wherein: creating an analysis task in an operation module, and submitting solution calculation;
extracting a calculation result of the wind-arbor branch finite element model, which specifically comprises the following steps: extracting the maximum tensile stress, the maximum compressive stress, the maximum bending stress and the maximum shearing stress of the arbor in the movement process under the action of wind load in a visualization module;
defining a wind-load fracture damage standard of an arbor branch, selecting tensile, bending and shearing strength of the arbor in 'the physical and mechanical properties of the wood of the main tree species in China' as a criterion, taking the influence of knots on the quality of the arbor into consideration, taking 85% of the four strengths as the wind-load fracture damage standard of the arbor, and evaluating the wind-load fracture resistance of the arbor under the action of wind load;
evaluating the wind load fracture resistance of the branches and the trunks of the arbor, and defining the damage criterion of the arbor model, wherein the criterion is as follows:
when the maximum compressive stress of the trunk or the branch of the arbor is greater than the standard of compressive strength, or the maximum bending stress of the trunk or the branch of the arbor is greater than the standard of bending strength, or the maximum shear stress of the trunk or the branch of the arbor is greater than the standard of shear strength, or the maximum tensile stress of the trunk or the branch of the arbor is greater than the standard of tensile strength, judging that the trunk or the branch of the arbor is subjected to stress failure, and breaking failure is carried out under wind load;
and when the maximum compressive stress of the trunk or the branch of the arbor is smaller than the compressive strength standard in the standard, or the maximum bending stress of the trunk or the branch of the arbor is smaller than the bending strength standard, or the maximum shear stress of the trunk or the branch of the arbor is smaller than the shear strength standard, or the maximum tensile stress of the trunk or the branch of the arbor is smaller than the tensile strength standard, judging that the trunk or the branch of the arbor is not subjected to stress damage, and not subjected to fracture damage under wind load.
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