Virtual patch measurement method and system for mechanical structure fatigue analysis process

Abstract

The present application relates to the technical field of fatigue analysis of mechanical structures, and discloses a virtual patch measurement method and system for the fatigue analysis process of a mechanical structure, the method comprising: obtaining a target unit surface corresponding to each virtual patch in a finite element model of the mechanical structure; determining the position of the center of each target unit surface in a first coordinate system and the stress / strain tensor matrix of the center of each target unit surface relative to the first coordinate system; establishing a corresponding second coordinate system with the center of each target unit surface, and determining the stress / strain tensor matrix of the center of the target unit surface relative to the second coordinate system through the angle cosine matrix between the second coordinate system of the target unit surface and each axis of the first coordinate system; determining the fatigue endurance life, and / or damage, and / or safety factor of the virtual patch corresponding to the target unit surface according to the stress / strain tensor matrix. The stress / strain determination technology in the fatigue analysis process of the present application can significantly improve the fatigue analysis accuracy of the mechanical structure, reduce the amount of calculation, and improve the calculation speed.

Description

Technical Field

[0001] The present application relates to the field of computer and mechanical technology, and in particular to the field of fatigue analysis technology of mechanical structures. Background Art

[0002] Usually, the fatigue durability analysis of mechanical structures is based on the stress and strain state of the structure. At present, there are two methods to determine the stress and strain state of the structure. Among them, the experimental method obtains the stress and strain distribution on the surface of the structure, and the finite element analysis method obtains the stress / strain tensor distribution of the structure position expressed by the nodes and units.

[0003] However, the current fatigue durability performance analysis directly based on finite element analysis results is not accurate enough, requires a lot of calculations, and has a slow calculation speed, and cannot accurately and efficiently express the actual life of the structure. Summary of the invention

[0004] The purpose of this application is to provide a virtual patch measurement method and system for a mechanical structure fatigue analysis process, which can significantly improve the fatigue analysis accuracy of the mechanical structure, reduce the amount of calculation, and increase the calculation speed.

[0005] The present application discloses a virtual patch measurement method for a mechanical structure fatigue analysis process, comprising:

[0006] Obtaining a target unit surface corresponding to each virtual patch in a finite element model of the mechanical structure;

[0007] Determine the position of the center of each target unit surface in the first coordinate system and the stress / strain tensor matrix of the center of each target unit surface relative to the first coordinate system;

[0008] Establishing a corresponding second coordinate system with the center of each target unit surface, determining an angle cosine matrix between the second coordinate system of the target unit surface and each axis of the first coordinate system, and determining a stress / strain tensor matrix of the center of the target unit surface relative to the second coordinate system based on the angle cosine matrix between the second coordinate system of the target unit surface and each axis of the first coordinate system and the stress / strain tensor matrix of the center of the target unit surface relative to the first coordinate system; and

[0009] According to the stress / strain tensor matrix of the center of each target unit surface in the corresponding second coordinate system, the fatigue endurance life, and / or damage, and / or safety factor of the virtual patch corresponding to the target unit surface is determined.

[0010] In a preferred embodiment, the step of obtaining a target unit surface corresponding to each virtual patch in the finite element model of the mechanical structure further comprises:

[0011] Obtaining the unit numbers corresponding to each unit face in the finite element model of the mechanical structure and all units to which the unit face belongs;

[0012] Each unit surface having a unique corresponding unit number among the unit surfaces is used as a target unit surface corresponding to the virtual patch.

[0013] In a preferred example, determining the stress / strain tensor matrix of the center of each target unit surface relative to the first coordinate system further includes: first determining the stress / strain tensor of each corner point of each target unit surface relative to the first coordinate system, and then determining the stress / strain tensor matrix of the center of the target unit surface relative to the first coordinate system based on the stress / strain tensor of each corner point relative to the first coordinate system.

[0014] In a preferred example, in the step of establishing a corresponding second coordinate system with the center of each target unit surface, the axis through the center that is parallel to the normal of the target unit surface and pointing in the positive direction of the normal is used as the virtual measurement coordinate axis Z axis; the projection of the line direction of two adjacent nodes on the plane passing through the center and perpendicular to the normal direction of the target unit surface is used as the virtual measurement coordinate axis X axis; and the virtual measurement coordinate axis Y axis is determined by the right-hand rule based on the X axis and the Z axis.

[0015] In a preferred example, the angular cosine matrix between the second coordinate system and each axis of the first coordinate system refers to the angular cosine matrix between the second coordinate system with the center of the target unit surface as the origin and each axis of the first coordinate system.

[0016] The present application also discloses a virtual patch measurement system for a mechanical structure fatigue analysis process, comprising:

[0017] An acquisition module, used for acquiring a target unit surface corresponding to each virtual patch in a finite element model of a mechanical structure;

[0018] A positioning module, used to determine the position of the center of each target unit surface in the first coordinate system and the stress / strain tensor matrix of the center of each target unit surface relative to the first coordinate system;

[0019] a virtual measurement module, configured to establish a corresponding second coordinate system with the center of each target unit surface, determine an angle cosine matrix between the second coordinate system of the target unit surface and each axis of the first coordinate system, and determine a stress / strain tensor matrix of the center of the target unit surface relative to the second coordinate system based on the angle cosine matrix between the second coordinate system of the target unit surface and each axis of the first coordinate system and the stress / strain tensor matrix of the center of the target unit surface relative to the first coordinate system; and

[0020] The fatigue calculation module is used to determine the fatigue endurance life, and / or damage, and / or safety factor of the virtual patch corresponding to the target unit surface according to the stress / strain tensor matrix of the center of each target unit surface in the corresponding second coordinate system.

[0021] In a preferred embodiment, the acquisition module includes:

[0022] A reading submodule is used to obtain the unit numbers corresponding to each unit face in the finite element model of the mechanical structure and all the units to which the unit face belongs;

[0023] The identification submodule is used to use each unit surface with a unique corresponding unit number among the unit surfaces as a target unit surface corresponding to the virtual patch.

[0024] In a preferred example, the virtual measurement module first determines the stress / strain tensor of each corner point of each target unit surface relative to the first coordinate system, and then determines the stress / strain tensor matrix of the center of the target unit surface relative to the first coordinate system based on the stress / strain tensor of each corner point relative to the first coordinate system.

[0025] The present application also discloses a virtual patch measurement system for a mechanical structure fatigue analysis process, including:

[0026] a memory for storing computer executable instructions; and,

[0027] A processor is used to implement the steps in the method described above when executing the computer executable instructions.

[0028] The present application also discloses a computer-readable storage medium in which computer-executable instructions are stored. When the computer-executable instructions are executed by a processor, the steps in the method described above are implemented.

[0029] In the implementation mode of the present application, according to the actual engineering phenomenon that cracks in the structure often initiate on the surface of the structure, the outer surface of the finite element model is first determined as the patch area through the "non-shared unit surface recognition technology", and then the patch position is determined through the "virtual patch positioning technology", and the "virtual strain gauges" are automatically pasted on the outer surface of the finite element model, and a virtual "measurement coordinate system" is established. The mapping of the finite element stress / strain tensor is realized through the "virtual measurement technology", and the finite element node stress and strain results on the non-shared node surface are converted into the "virtual patch" position and the stress and strain in the corresponding direction in the "measurement coordinate system" for fatigue calculation, and the calculation of the fatigue durability performance of the structure is returned to the surface consistent with the material test. The "virtual patch technology" of fatigue analysis can greatly reduce the unnecessary calculation amount of the internal units of the structure, which not only improves the calculation accuracy, but also improves the calculation speed.

[0030] The present application proposes a non-shared unit face recognition technology. Specifically, based on searching for surfaces where fatigue may occur, the technology greatly reduces the amount of calculation compared to traditional methods that calculate all units or nodes of the entire model.

[0031] Furthermore, the present application proposes a virtual patch positioning technology. Specifically, a virtual patch is performed on a non-shared unit surface, a virtual measurement coordinate system is determined, and a patch position and orientation consistent with the test are obtained, thereby improving the consistency between calculation and test.

[0032] Furthermore, the present application proposes a virtual measurement technology to obtain stress and strain consistent with the test, which is beneficial to improving the accuracy of fatigue durability analysis.

[0033] A large number of technical features are recorded in the specification of this application, which are distributed in various technical solutions. If all possible combinations of technical features of this application (i.e., technical solutions) are to be listed, the specification will be too long. In order to avoid this problem, the various technical features disclosed in the above-mentioned invention content of this application, the various technical features disclosed in the various embodiments and examples below, and the various technical features disclosed in the accompanying drawings can be freely combined with each other to form various new technical solutions (these technical solutions are all deemed to have been recorded in this specification), unless the combination of such technical features is technically infeasible. For example, in one example, feature A+B+C is disclosed, and in another example, feature A+B+D+E is disclosed, and features C and D are equivalent technical means that play the same role. Technically, only one can be used, and it is impossible to use them at the same time. Feature E can be combined with feature C technically. Then, the solution of A+B+C+D should not be deemed to have been recorded because it is technically infeasible, and the solution of A+B+C+E should be deemed to have been recorded. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a flow chart of a virtual patch measurement method for a mechanical structure fatigue analysis process according to a first embodiment of the present application;

[0035] Figure 2 is a schematic diagram of a virtual patch in a virtual patch measurement method in a mechanical structure fatigue analysis process according to a first embodiment of the present application;

[0036] Figure 3 is a schematic diagram of a global coordinate system and a virtual measurement coordinate system in a virtual patch measurement method in a mechanical structure fatigue analysis process according to a first embodiment of the present application;

[0037] Figure 4 It is a schematic diagram of a first-order hexahedral solid element model;

[0038] Figure 5It is a schematic diagram of the node coordinate system and patch coordinate system of the product structure;

[0039] Figure 6 It is a schematic diagram of the patch coordinate system and unit coordinate system of the entity unit;

[0040] Figure 7 It is a schematic diagram of the corner points and nodes of adjacent elements in the entire model composed of several finite elements;

[0041] Figure 8 It is a structural schematic diagram of a virtual patch measurement system for a mechanical structure fatigue analysis process according to a second embodiment of the present application. DETAILED DESCRIPTION

[0042] In the following description, many technical details are provided to help readers better understand the present application. However, those skilled in the art can understand that the technical solution claimed in the present application can be implemented even without these technical details and various changes and modifications based on the following embodiments.

[0043] Description of some concepts:

[0044] Non-shared element face, in English, is called “Nonshared Element Face”, where the element face refers to the face contained in all the elements in the model, and the element face exposed on the surface of the model is called “non-shared element face”. In addition, the element face shared by several elements and hidden inside the model is called “shared element face”.

[0045] Element Corner, see Figure 7 .

[0046] Nodes. In a model composed of several finite elements, the corner points of adjacent elements coincide with each other. That is, for the entire model, it is called a node, and for each element, it is called a corner point. See Figure 7 .

[0047] Stress / strain tensor, in English “Stress / Strain Tensor”, is a mathematical representation of the stress / strain state. The symbol “ / ” here represents “and and or”.

[0048] The center of face, called “Central of Face” in English, refers to the geometric center position of the face.

[0049] Damage, in English, is a physical quantity corresponding to life span. The greater the damage, the shorter the life span.

[0050] Measuring coordinate system, in English, is “Measuring Coordinate Systems”, which refers to the reference system used to determine the strain / strain tensor.

[0051] Fatigue, or “Fatigue” in English, refers to the destruction of a structure under repeated stress / strain. Life is often used to measure the fatigue durability of a structure.

[0052] The following is a brief description of some of the innovative features of this application:

[0053] After long-term research, the inventors of this application found that different positions in the structure have different stress and strain values ​​due to their different stress states. The durability of the structure (fatigue life, cumulative damage and fatigue safety factor) is extremely sensitive to the stress and strain state of the structure. At the same time, the material SN curve used to calculate the fatigue durability of the structure is also obtained based on the measurement data of the strain gauges posted on the surface of the structure. The stress and strain obtained by experimental measurement can be directly used for fatigue durability performance calculation; while the stress / strain tensor obtained by finite element analysis, especially for complex structures and stress states, is often not suitable for direct use in fatigue algorithms to calculate fatigue durability performance. This is because the direct use of stress and strain from finite element analysis will cause speed and accuracy problems in fatigue durability performance analysis. The reason is:

[0054] 1) It is not easy to make the coordinate plane of the finite element node (analogous to the strain patch) consistent with the section of the structure surface. The stress / strain tensor of the finite element node is often not the stress / strain value measured by the strain gauge on the structure surface, which will lead to further fatigue durability performance calculation accuracy problems. 2) The stress and strain of the solid element is the stress and strain value at the center of the solid element. The center of the solid finite element is not on the surface. The stress and strain at the center of the solid element and the stress and strain measured on the structure surface are often different, which will lead to further fatigue durability performance calculation accuracy problems. 3) Since the solid element inside the structure is not located on the surface where the crack initiates, the life calculated for the internal solid element cannot express the actual life of the structure, and it consumes a lot of calculation cost. 4) It is not easy to make the coordinate plane of the finite element corner point consistent with the section of the structure surface. The stress / strain tensor of the finite element corner point is often not the stress and strain value measured by the surface strain gauge, which will lead to further fatigue durability performance calculation accuracy problems. 5) The stress and strain values ​​of the shared corner points of several finite elements are often different. If the fatigue durability performance calculation is performed for each corner point of the unit, the calculation amount is too large and the calculation speed is slow.

[0055] Specifically, Figure 4As shown in the figure, taking the first-order hexahedral solid unit model (solid unit without intermediate nodes) as an example, there are n1 grids in the length direction, n2 grids in the width direction, and n3 grids in the height direction. The number of non-shared unit faces, the number of all faces, the number of units, the number of nodes, and the number of corner points contained in the model vary with n1, n2, and n3 as follows:

[0056] Number of non-shared unit faces = 2×(n1×n2+n2×n3+n1×n3)

[0057] Total number of faces = n1×n2+n2×n3+n1×n3+3×n1×n2×n3

[0058] Number of units = n1×n2×n3

[0059] Number of nodes = 4×(n1+1)+2×(n1+1)×(n2-1)+(n3-1)×[2×(n1+1)+(n1+1)×(n2-1)]

[0060] Number of corner points = 8×n1×n2×n3

[0061] Further shown in the following table:

[0062]

[0063] The above table shows that as the size of the finite element increases, the difference between the number of non-shared element faces and the number of all element faces increases, which means that the method based on non-shared element faces has a greater computational advantage.

[0064] Further, such as Figure 5 As shown in the figure, the plane of the finite element node coordinate system (analogous to the strain patch) is not easy to be consistent with the section of the structure surface. The stress / strain tensor of the finite element node is often not the stress and strain value measured by the strain gauge on the structure surface, which will lead to further fatigue durability performance calculation accuracy problems, such as Figure 5 The left figure in is the node coordinate system. Figure 5 The right picture is the patch coordinate system.

[0065] The structural appearance of actual products is ever-changing, and it is often difficult to use very neat and regular blocks to divide the grid in actual calculations. Especially for structures whose surfaces are not completely flat, the patch coordinate system is located on the section of the structural surface, while the node coordinate system is located on the node, and the directions of the axes of the coordinate system are often not parallel or perpendicular to the structural surface. The different directions of the coordinate axes lead to great differences in the measured strains. Taking the angle difference of a single axis as an example, the following table illustrates the relative strain error caused by the angle difference:

[0066] Angle error (degrees) Strain relative error 5 0.38％ 10 1.52％ 15 3.41％ 20 6.03％ 25 9.37％ 30 13.40％ 35 18.08％ 40 23.40％ 45 29.29％

[0067] Strain error will lead to further errors of greater magnitude in fatigue durability performance. The following table lists the changes in life corresponding to changes in strain. It can be seen that a 10% strain error will lead to several times the life error.

[0068] strain life 0.00010 1.287E+17 0.00011 4.720E+16 0.00012 1.889E+16 0.00013 8.134E+15 0.00014 3.728E+15 0.00015 1.803E+15

[0069] The stress and strain of the solid element are the stress and strain values ​​at the center of the solid element. The center of the solid finite element is not on the surface. The stress and strain at the center of the solid element and the stress and strain measured on the surface of the structure are often different, which will lead to further problems in the calculation accuracy of fatigue durability performance.

[0070] As Figure 6 Take the solid element shown as an example, Figure 6 The left picture in the figure is the patch coordinate system, and the right picture is the unit coordinate system. The unit coordinate system is located inside the unit, which is different from the position measured by the patch coordinate system. The directions of the two coordinate systems are also different, so there are errors in the measured strain / stress, which will lead to greater errors in further fatigue life results.

[0071] Figure 7 The left picture is the patch coordinate system, and the right picture is the corner coordinate system. The stress and strain values ​​of the shared corners of several finite elements are often different. If fatigue durability performance calculations are performed for each corner of each unit, the amount of calculation is too large and the calculation speed is slow. The coordinate plane of the finite element corner point is not easy to be consistent with the section of the structure surface. The stress / strain tensor of the finite element corner point is often not the stress and strain value measured by the surface strain gauge, which will lead to further fatigue durability performance calculation accuracy problems.

[0072] In the entire model composed of several finite elements, the corner points of adjacent elements coincide with each other as nodes, that is, for the entire model, it is called a node, and for each element, it is called a corner point. A node corresponds to several corner points, so the amount of calculation based on corner points is several times (at least 2 times) the amount of calculation based on nodes.

[0073] Figure 7 There are patch coordinate system and corner point coordinate system. The difference between corner point coordinate system and patch coordinate system results in the difference between strain / stress measured by corner point coordinate system and strain / stress measured by patch coordinate system, thus bringing greater error to further fatigue calculation.

[0074] In view of the above analysis, in this application, according to the actual engineering phenomenon that cracks in the structure often initiate on the surface of the structure, the outer surface of the finite element model is first determined as the patch area through the "non-shared unit surface recognition technology", and then the patch position is determined through the "virtual patch positioning technology". The "virtual strain gauges" are automatically pasted on the outer surface of the finite element model, and a virtual "measurement coordinate system" is established. The mapping of the finite element stress / strain tensor is realized through the "virtual measurement technology", and the finite element node stress and strain results on the non-shared node surface are converted into the "virtual patch" position and the stress and strain in the corresponding direction in the "measurement coordinate system" for fatigue calculation, and the calculation of the fatigue durability performance of the structure is returned to the surface consistent with the material test. The "virtual patch technology" of fatigue analysis can greatly reduce the unnecessary calculation amount of the internal units of the structure, which not only improves the calculation accuracy, but also improves the calculation speed.

[0075] The present application proposes a non-shared unit face recognition technology. Specifically, based on searching for surfaces where fatigue may occur, the technology greatly reduces the amount of calculation compared to traditional methods that calculate all units or nodes of the entire model.

[0076] Furthermore, the present application proposes a virtual patch positioning technology. Specifically, a virtual patch is performed on a non-shared unit surface, a virtual measurement coordinate system is determined, and a patch position and orientation consistent with the test are obtained, thereby improving the consistency between calculation and test.

[0077] Furthermore, the present application proposes a virtual measurement technology to obtain stress and strain consistent with the test, which is beneficial to improving the accuracy of fatigue durability analysis.

[0078] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below in conjunction with the accompanying drawings.

[0079] The first embodiment of the present application relates to a virtual patch measurement method for a mechanical structure fatigue analysis process, and the process is as follows: Figure 1 As shown, the method comprises the following steps:

[0080] First, through steps 110-120, the target unit surface corresponding to each virtual patch in the finite element model of the mechanical structure is obtained. Specifically, as follows:

[0081] Step 110: Obtain the unit numbers corresponding to each unit face in the finite element model of the mechanical structure and all units to which the unit face belongs.

[0082] Specifically, the unit surface is a shared unit surface or a non-shared unit surface.

[0083] The unit face refers to the face contained in all the units in the finite element model, including the unit faces exposed on the surface of the finite element model, called "non-shared unit faces", and the unit faces shared by several units and hidden inside the finite element model, called "shared unit faces".

[0084] Among them, each unit has a unique and fixed unit number.

[0085] Among them, each unit is composed of several unit faces, for example, a tetrahedral unit has 4 unit faces, and a hexahedral unit has 6 unit faces.

[0086] Preferably, by traversing the number of unit numbers corresponding to the units to which each unit face belongs, it is possible to determine how many units the unit face belongs to in total.

[0087] Step 120: Use each unit surface with a unique corresponding unit number among the unit surfaces as a target unit surface corresponding to the virtual patch.

[0088] Specifically, it is determined whether the unit numbers corresponding to all units to which each unit surface obtained in the above step belongs are unique. If so, the unit surface is determined as a non-shared unit surface and used as the target unit surface of the virtual patch.

[0089] For example, if it is a hexahedral element, it has 6 element faces, one of which is an element face exposed on the surface of the finite element model, called a "non-shared element face", and the remaining 5 are element faces shared by several elements and hidden inside the finite element model, called "shared element faces".

[0090] When the target unit face of the virtual patch is identified, a judgment is made based on whether the unit numbers corresponding to all units to which each unit face belongs are unique.

[0091] It should be pointed out that the applicant of this application has found through research that since the shared unit surface is located inside the mechanical structure and fatigue crack initiation often starts from the surface, calculating the fatigue life of the shared unit surface inside the structure (whose life value is greater than the life of the structure surface) is not valuable for judging the minimum life of the structure, but will instead cause excessive calculation.

[0092] Step 130: Determine the position of the center of each target unit surface in the global coordinate system and the stress / strain tensor matrix relative to the global coordinate system.

[0093] Preferably, the stress / strain tensor of each corner point of each target unit surface relative to the overall coordinate system can be determined first, and then the stress / strain tensor matrix of the center of the target unit surface relative to the overall coordinate system can be determined based on the stress / strain tensor of each corner point relative to the overall coordinate system.

[0094] Specifically, the normal direction r of each target unit surface, the corner points, and the stress / strain tensor of each corner point are read.

[0095] See also Figure 2 The hexahedral element Element-1 has two target element faces of virtual patches, namely, the target element face A1 composed of nodes C1-C2-C3-C4, and the target element face A2 composed of nodes C5-C6-C2-C1. The normal directions of the target element faces A1 and A2 are set to r1 and r2, respectively (not shown in the figure).

[0096] The following takes the target unit surface A1 as an example to further explain the specific implementation method of the target unit surface positioning of the virtual patch:

[0097] Determine the number of nodes NA1=4 of the target unit surface A1, the coordinate values ​​C1(x_C1, y_C1, z_C1), C2(x_C2, y_C2, z_C2), C3(x_C3, y_C3, z_C3), C4(x_C4, y_C4, z_C4) of each node on the target unit surface A1 in the global coordinate system o-xyz, and the normal direction r1 of the target unit surface A1, and determine the stress / strain tensor s of each node relative to the global coordinate system o-xyz. Taking node C1 as an example, the stress / strain tensor of node C1 in the global coordinate system is:

[0098] s_c1(sxx_c1,syy_c1,szz_c1,sxy_c1,syz_c1,sxz_c1)

[0099] in,

[0100] sxx_c1, syy_c1, szz_c1 are the normal stress / strain of point C1 in the x-direction, y-direction and z-direction in the global coordinate system o-xyz, respectively;

[0101] sxy_c1, syz_c1, and sxz_c1 are the shear stress / strain at the point in the xy plane, yz plane, and xz plane, respectively.

[0102] It should be pointed out that the overall coordinate system o-xyz is a global coordinate system and is a relative system benchmark for the overall model of the mechanical structure.

[0103] In this embodiment, the global coordinate system may be referred to as a first coordinate system.

[0104] According to the statistically obtained coordinate values ​​of each node (node ​​C1, node C2, node C3, node C4), the coordinate oA1 (x_oA1, y_oA1, z_oA1) of the center position oA1 of the target unit surface of the virtual patch is determined according to the following formula:

[0105]

[0106]

[0107] Furthermore, according to the stress / strain tensor of each corner point of the target unit surface A1 relative to the global coordinate system, the stress / strain tensor of the center point oA1 of the target unit surface A1 in the global coordinate system is determined (uniformly represented by s_oA1(sxx_oA1,syy_oA1,szz_oA1,sxy_oA1,syz_oA1,sxz_oA1)).

[0108] Take the normal stress / strain tensor sxx_oA1 of the center point oA1 of the target unit surface A1 in the x direction in the global coordinate system o-xyz as an example:

[0109]

[0110] By the same method, the stress / strain tensor matrix [s_oA1] of the center of the target unit surface relative to the global coordinate system can be determined according to the stress / strain tensor of each corner point relative to the global coordinate system.

[0111] Among them, sxx_oA1, syy_oA1, szz_oA1 are the normal stress / strain of point oA1 in the x direction, y direction and z direction in the overall coordinate system o-xyz respectively; sxy_oA1, syz_oA1, sxz_oA1 are the shear stress / strain of the point in the xy plane, yz plane and xz plane respectively.

[0112] Step 140: Establish a corresponding virtual measurement coordinate system with the center of each target unit surface, determine the angle cosine matrix between the virtual measurement coordinate system of the target unit surface and the axes of the overall coordinate system, and determine the stress / strain tensor matrix of the center of the target unit surface relative to the virtual measurement coordinate system based on the angle cosine matrix between the virtual measurement coordinate system of the target unit surface and the axes of the overall coordinate system, and the stress / strain tensor matrix of the center of the target unit surface relative to the overall coordinate system.

[0113] Preferably, the angle cosine matrix between the virtual measurement coordinate system and each axis of the global coordinate system refers to the angle cosine matrix between the virtual measurement coordinate system and each axis of the global coordinate system respectively taking the center of the target unit surface as the origin.

[0114] Preferably, a virtual measurement coordinate system can be established at the center of the target unit surface of the virtual patch in the following specific manner:

[0115] 1) The axis passing through the center point oA1 and parallel to the normal line r1 of the target unit surface A1 and pointing in its positive direction is taken as the virtual measurement coordinate axis oA1-zA1; 2) The projection of the line from node C1 to node C2 on the plane passing through the center point oA1 and perpendicular to the normal line r1 of the target unit surface A1 is taken as the virtual measurement coordinate axis oA1-xA1. It should be pointed out that C1 and C2 are two points on the unit surface, and there is no specific association requirement between the two. The virtual measurement coordinate axis oA1-xA1 is located on a plane perpendicular to the virtual measurement coordinate axis oA1-zA1, and its direction is the projection of the ray from node C1 to node C2 on this plane. ; 3) According to oA1-xA1 and oA1-zA1, the virtual measurement coordinate axis oA1-yA1 is determined according to the right-hand rule.

[0116] In this embodiment, the virtual measurement coordinate system may be referred to as a second coordinate system.

[0117] See also Figure 3 In this step, the angle cosine matrix [L] between each axis of the virtual measurement coordinate system with the center oA1 of the target unit surface as the origin and each axis of the global coordinate system is determined.

[0118] The stress / strain tensor matrix s′_oA1 of the center oA1 of the target unit surface under the virtual measurement coordinate axis oA1-xA1, yA1, zA1 is:

[0119]

[0120] Step 150: Determine the fatigue endurance life, and / or damage, and / or safety factor of the virtual patch corresponding to each target unit surface according to the stress / strain tensor matrix of the center of each target unit surface in the corresponding virtual measurement coordinate system.

[0121] Preferably, the stress / strain tensor matrix of the center of each target unit surface in the corresponding virtual measurement coordinate system at different times can be obtained first to determine the amplitude and mean of the time history of the stress / strain tensor matrix of the center of the target unit surface in the corresponding virtual measurement coordinate system, and then a fatigue algorithm is used to calculate the fatigue endurance life, and / or damage, and / or safety factor of the center position of the virtual patch corresponding to each target unit surface.

[0122] The following uses an alternating stress cycle as an example to illustrate how the stress / strain tensor obtained from virtual measurement is used in the biaxial Manson-Coffin strain fatigue calculation:

[0123] time <![CDATA[s ′ xx oA1 ]]> <![CDATA[s ′ yy oA1 ]]> <![CDATA[s ′ zz oA1 ]]> <![CDATA[s ′ xy oA1 ]]> <![CDATA[s ′ yz oA1 ]]> <![CDATA[s ′ xz oA1 ]]> T1 0 0 0 0 0 0 T2 <![CDATA[s ′ xx oA1 ]]> <![CDATA[s ′ yy oA1 ]]> <![CDATA[s ′ zz oA1 ]]> <![CDATA[s ′ xy oA1 ]]> <![CDATA[s ′ yz oA1 ]]> <![CDATA[s ′ xz oA1 ]]> T3 0 0 0 0 0 0

[0124] Assume s ′ yy oA1 ′ xx oA1 , first calculate the biaxial ratio r and strain amplitude Δε:

[0125]

[0126] Then the biaxial ratio r and strain amplitude Δε are substituted into the biaxial Manson-Coffin strain life calculation formula, and the life N is calculated by nonlinear solution. f :

[0127]

[0128] Among them, Young's modulus E, fatigue strength coefficient σ f ′ , Poisson's ratio μ, fatigue strength index b, fatigue ductility coefficient ε f ′ , fatigue ductility index c are the corresponding material parameters of the structure.

[0129] The stress / strain tensor obtained by virtual measurement can be used in various fatigue algorithms. When other fatigue algorithms are used for life / damage calculation or fatigue safety factor calculation, other items of the s′_oA1 matrix may be used, which will not be described here one by one.

[0130] The second embodiment of the present application relates to a virtual patch measurement system for a mechanical structure fatigue analysis process, and its structure is as follows: Figure 8 As shown, the system includes:

[0131] An acquisition module, used for acquiring a target unit surface corresponding to each virtual patch in a finite element model of a mechanical structure;

[0132] A positioning module, used to determine the position of the center of each target unit surface in the first coordinate system and the stress / strain tensor matrix of the center of each target unit surface relative to the first coordinate system;

[0133] a virtual measurement module, configured to establish a corresponding second coordinate system with the center of each target unit surface, determine an angle cosine matrix between the second coordinate system of the target unit surface and each axis of the first coordinate system, and determine a stress / strain tensor matrix of the center of the target unit surface relative to the second coordinate system based on the angle cosine matrix between the second coordinate system of the target unit surface and each axis of the first coordinate system and the stress / strain tensor matrix of the center of the target unit surface relative to the first coordinate system; and

[0134] ​The fatigue calculation module is used to determine the fatigue endurance life, and / or damage, and / or safety factor of the virtual patch corresponding to the target unit surface according to the stress / strain tensor matrix of the center of each target unit surface in the corresponding second coordinate system.

[0135] Preferably, the acquisition module comprises:

[0136] A reading submodule is used to obtain the unit numbers corresponding to each unit face in the finite element model of the mechanical structure and all the units to which the unit face belongs;

[0137] The identification submodule is used to use each unit surface with a unique corresponding unit number among the unit surfaces as a target unit surface corresponding to the virtual patch.

[0138] Preferably, the virtual measurement module first determines the stress / strain tensor of each corner point of each target unit surface relative to the first coordinate system, and then determines the stress / strain tensor matrix of the center of the target unit surface relative to the first coordinate system based on the stress / strain tensor of each corner point relative to the first coordinate system.

[0139] The first implementation manner is a method implementation manner corresponding to the present implementation manner. The technical details in the first implementation manner can be applied to the present implementation manner, and the technical details in the present implementation manner can also be applied to the first implementation manner.

[0140] It should be noted that those skilled in the art should understand that the implementation functions of each module shown in the implementation of the virtual patch measurement system of the mechanical structure fatigue analysis process can be understood by referring to the relevant description of the virtual patch measurement method of the mechanical structure fatigue analysis process. The functions of each module shown in the implementation of the virtual patch measurement system of the mechanical structure fatigue analysis process can be realized by a program (executable instruction) running on a processor, or by a specific logic circuit. If the virtual patch measurement system of the mechanical structure fatigue analysis process of the embodiment of the present application is implemented in the form of a software function module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiment of the present application can be essentially or partly reflected in the form of a software product, which is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the methods described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read Only Memory), disk or CD and other media that can store program code. Thus, embodiments of the present application are not limited to any specific combination of hardware and software.

[0141] Accordingly, an embodiment of the present application further provides a computer storage medium, in which computer executable instructions are stored. When the computer executable instructions are executed by a processor, the various method embodiments of the present application are implemented.

[0142] In addition, the embodiment of the present application also provides a virtual patch measurement system for a mechanical structure fatigue analysis process, which includes a memory for storing computer executable instructions, and a processor; the processor is used to implement the steps in the above-mentioned method implementation when executing the computer executable instructions in the memory. Among them, the processor can be a central processing unit (Central Processing Unit, referred to as "CPU"), or other general-purpose processors, digital signal processors (Digital Signal Processor, referred to as "DSP"), Application Specific Integrated Circuit (Application Specific Integrated Circuit, referred to as "ASIC"), etc. The aforementioned memory can be a read-only memory (read-only memory, referred to as "ROM"), a random access memory (random access memory, referred to as "RAM"), a flash memory (Flash), a hard disk or a solid-state hard disk, etc. The steps of the method disclosed in each embodiment of the present invention can be directly embodied as a hardware processor execution, or a combination of hardware and software modules in the processor.

[0143] It should be noted that in the application documents of this patent, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one" do not exclude the existence of other identical elements in the process, method, article or device including the elements. In the application documents of this patent, if it is mentioned that an action is performed according to an element, it means that the action is performed at least according to the element, which includes two situations: performing the action only according to the element, and performing the action according to the element and other elements. Expressions such as multiple, multiple, and multiple include 2, 2 times, 2 kinds, and more than 2, more than 2 times, and more than 2 kinds.

[0144] All documents mentioned in this application are considered to be included in the disclosure of this application as a whole, so that they can be used as the basis for modification when necessary. In addition, it should be understood that after reading the above disclosure of this application, those skilled in the art can make various changes or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. A virtual patch measurement method for a mechanical structure fatigue analysis process, characterized in that: Include: Obtaining a target unit surface corresponding to each virtual patch in a finite element model of the mechanical structure; Determine the position of the center of each target unit surface in the global coordinate system and the stress / strain tensor matrix of the center of each target unit surface relative to the global coordinate system, wherein the global coordinate system is a first coordinate system, wherein the stress / strain tensor of each corner point of each target unit surface relative to the first coordinate system is first determined, and then the stress / strain tensor matrix of the center of the target unit surface relative to the first coordinate system is determined according to the stress / strain tensor of each corner point relative to the first coordinate system; Establishing a corresponding virtual measurement coordinate system with the center of each target unit surface, the virtual measurement coordinate system is a second coordinate system, wherein an axis through the center parallel to the normal of the target unit surface and pointing in the positive direction of the normal is used as a virtual measurement coordinate axis Z axis, a projection of a line connecting two adjacent nodes on a plane passing through the center and perpendicular to the normal direction of the target unit surface is used as a virtual measurement coordinate axis X axis, the virtual measurement coordinate axis Y axis is determined by using the right-hand rule according to the X axis and the Z axis, an angle cosine matrix between the second coordinate system of the target unit surface and each axis of the first coordinate system is determined, and a stress / strain tensor matrix of the center of the target unit surface relative to the second coordinate system is determined according to the angle cosine matrix between the second coordinate system of the target unit surface and each axis of the first coordinate system, and a stress / strain tensor matrix of the center of the target unit surface relative to the first coordinate system; and According to the stress / strain tensor matrix of the center of each target unit surface in the corresponding second coordinate system, the fatigue endurance life, and / or damage, and / or safety factor of the virtual patch corresponding to the target unit surface is determined.

2. The method according to claim 1, characterized in that The step of obtaining a target unit surface corresponding to each virtual patch in the finite element model of the mechanical structure further comprises: Obtaining the unit numbers corresponding to each unit face in the finite element model of the mechanical structure and all units to which the unit face belongs; Each unit surface with a unique corresponding unit number among the unit surfaces is used as a target unit surface corresponding to the virtual patch.

3. The method according to claim 1, characterized in that The angle cosine matrix between the second coordinate system and each axis of the first coordinate system refers to the angle cosine matrix between the second coordinate system with the center of the target unit surface as the origin and each axis of the first coordinate system.

4. A virtual patch measurement system for mechanical structure fatigue analysis process, characterized in that: Include: An acquisition module, used for acquiring a target unit surface corresponding to each virtual patch in a finite element model of a mechanical structure; A positioning module, used to determine the position of the center of each target unit surface in the overall coordinate system and the stress / strain tensor matrix of the center of each target unit surface relative to the overall coordinate system, wherein the overall coordinate system is a first coordinate system, wherein the stress / strain tensor of each corner point of each target unit surface relative to the first coordinate system is first determined, and then the stress / strain tensor matrix of the center of the target unit surface relative to the first coordinate system is determined based on the stress / strain tensor of each corner point relative to the first coordinate system; a virtual measurement module, for establishing a corresponding virtual measurement coordinate system with the center of each target unit surface, wherein the virtual measurement coordinate system is a second coordinate system, wherein an axis through the center parallel to the normal of the target unit surface and pointing in the positive direction of the normal is used as a virtual measurement coordinate axis Z axis, a projection of a line connecting two adjacent nodes on a plane passing through the center and perpendicular to the normal direction of the target unit surface is used as a virtual measurement coordinate axis X axis, a virtual measurement coordinate axis Y axis is determined by using the right-hand rule according to the X axis and the Z axis, an angle cosine matrix between the second coordinate system of the target unit surface and each axis of the first coordinate system is determined, and a stress / strain tensor matrix of the center of the target unit surface relative to the second coordinate system is determined according to the angle cosine matrix between the second coordinate system of the target unit surface and each axis of the first coordinate system, and a stress / strain tensor matrix of the center of the target unit surface relative to the first coordinate system; and The fatigue calculation module is used to determine the fatigue endurance life, and / or damage, and / or safety factor of the virtual patch corresponding to the target unit surface according to the stress / strain tensor matrix of the center of each target unit surface in the corresponding second coordinate system.

5. The system according to claim 4, characterized in that The acquisition module contains: A reading submodule is used to obtain the unit numbers corresponding to each unit face in the finite element model of the mechanical structure and all the units to which the unit face belongs; The identification submodule is used to use each unit surface with a unique corresponding unit number among the unit surfaces as a target unit surface corresponding to the virtual patch.

6. A virtual patch measurement system for mechanical structure fatigue analysis process, characterized in that: include: A memory for storing computer executable instructions; as well as, A processor, configured to implement the steps in the method according to any one of claims 1 to 3 when executing the computer executable instructions.

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a processor, the steps in the method according to any one of claims 1 to 3 are implemented.

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