A method for visualizing the dynamic mechanical properties of shield machine cutterhead

Abstract

The present invention provides a method for visualizing the dynamic mechanical properties of a shield machine cutterhead, comprising: constructing a finite element mesh model of the shield machine cutterhead; constructing a prediction model, and predicting the stresses of all nodes through the prediction model; using the center of the shield machine cutterhead as the rotation axis, obtaining a rotation formula for the rotation angle θ around the axis, and calculating the coordinates of all nodes of the shield machine cutterhead after the rotation angle θ through the rotation formula; reconstructing the finite element mesh model; inserting the stress information corresponding to the node, and performing color mapping and rendering to visualize the dynamic mechanical properties of the shield machine cutterhead. Compared with the limitation of traditional finite element simulation methods that can only display the dynamic performance at different times under the same working condition, the dynamic mechanical performance visualization method provided by the present invention can display the dynamic performance of the shield machine cutterhead under different working conditions, different postures, and different times, and has better engineering applicability.

Description

Technical Field

[0001] The present invention relates to the technical field of shield machine cutter head simulation, and in particular to a method for visualizing the dynamic mechanical performance of a shield machine cutter head. Background Art

[0002] The cutterhead of a shield machine is one of the main components of the shield machine. Its dynamic performance such as stress and displacement during the excavation process directly affects the service life, production capacity and economic benefits of the device. If a certain part of the cutterhead of a shield machine runs in a state of excessive stress for a long time, it will cause the cutterhead of the shield machine to fail and be damaged. Therefore, measures must be taken to reflect the performance of the cutterhead during operation. At present, the performance of the cutterhead of a shield machine is mostly strength-checked through finite element simulation software, etc., to obtain the stress condition of the equipment, and then displayed through post-processing software. The main problems in the existing technology are as follows:

[0003] First, the cutterhead of a shield machine experiences different operating conditions and boundary conditions at every moment during tunneling. Finite element simulation requires model modification and debugging for each operating condition. Calculating stress performance states for each condition inherently involves a significant amount of repetitive work, making the entire process inefficient and time-consuming.

[0004] Secondly, because shield machines are complex underground engineering equipment, finite element simulation grids typically reach over a million, requiring significant computing resources and time. This makes it difficult to simulate and display the stress state of the cutterhead in real time during construction, hindering operators' ability to understand the stress state of the cutterhead in real time and thus enable intelligent operation and maintenance decisions.

[0005] Finally, the finite element-based simulation technology mainly performs offline simulation. The simulation results corresponding to each simulation are usually carried out under the same working conditions. As for the dynamic performance, it can usually only calculate the stress state of the shield machine cutter head under the same working conditions at different times. It cannot meet the needs of displaying the dynamic performance of the shield machine cutter head under different postures, different working conditions, and different times.

[0006] Therefore, in response to the above problems, how to quickly and efficiently obtain the results of the shield machine cutter head under different working conditions, how to effectively extract the post-processing results, and how to realize the visualization of the real-time dynamic three-dimensional model after calculation are difficult problems that need to be solved urgently.

[0007] In summary, there is an urgent need for a method to visualize the dynamic mechanical properties of the shield machine cutterhead to solve the problems existing in the existing technology. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for visualizing the dynamic mechanical properties of a shield machine cutterhead. The specific technical solution is as follows:

[0009] A method for visualizing the dynamic mechanical properties of a shield machine cutterhead, comprising:

[0010] S1: Construct a finite element mesh model of the shield machine cutterhead, obtain result files of the finite element mesh model under different working conditions, and extract characteristic information of the result files; the characteristic information includes node coordinate information, node information contained in the mesh unit, and node stress and displacement information;

[0011] S2: Generate a sample matrix X through node coordinate information and node stress, reduce the dimension of the sample matrix X to generate a new space matrix C and a principal component matrix B, fit the shield machine dynamic parameters to the new space matrix C to obtain the function relationship C1, obtain the new space matrix C2 under the new working condition through the function relationship C1, and calculate the inverse matrix B of the principal component matrix B. -1 After multiplying by the new spatial matrix C2, the prediction model is obtained, and the stress of all nodes is predicted by the prediction model;

[0012] S3: Taking the center of the shield machine's cutterhead as the rotation axis, obtain the rotation formula for the rotation angle θ around the axis. Calculate the coordinates of all nodes of the shield machine's cutterhead after the rotation angle θ using the rotation formula.

[0013] S4: In the VTK module, the finite element mesh model is reconstructed according to the node information contained in the mesh unit in step S1 and the node coordinates rotated in step S3; the stress information corresponding to the node is inserted and color mapping and rendering are performed to realize the visualization of the dynamic mechanical properties of the shield machine cutter head.

[0014] Preferably, the result file includes an odb file and an inp file.

[0015] Preferably, the step S2 specifically includes:

[0016] S2-1: Generate sample matrix X through node coordinate information and node stress;

[0017] S2-2: Standardize the sample matrix to obtain the matrix X1;

[0018] S2-3: Calculate the covariance matrix X2 of matrix X1,

[0019] S2-4: Solve the eigenvalues of the covariance matrix X2, and arrange them in descending order to obtain m eigenvalues (α1, α2, α3, α4...α m ), and the eigenvectors corresponding to the above eigenvalues are solved as (β1,β2,β3,β4...β m );

[0020] S2-5: Take the first z eigenvalues whose cumulative contribution rate is greater than the set value, and take the transpose of the z eigenvectors corresponding to the first z eigenvalues (β1, β2, β3, β4...β z ) T Generate the principal component matrix B.

[0021] S2-6: Multiply the principal component matrix B by the sample matrix X to obtain a new spatial matrix C after dimensionality reduction, and fit the dynamic parameters of the shield machine to the new spatial matrix to obtain the functional relationship C1;

[0022] S2-7: Input the dynamic parameters of the shield machine under the new working condition into the function relationship C1 to obtain the new spatial matrix C2 under the new working condition, and convert the inverse matrix B of the principal component matrix -1 Multiplying by the new spatial matrix C2 yields the nodal stresses of all nodes under the new working condition.

[0023] Preferably, the dynamic parameters of the shield machine include torque and thrust.

[0024] Preferably, the expression of the cumulative contribution rate is as follows:

[0025]

[0026] Among them, α i Represents the i-th eigenvalue in the eigenvalue set.

[0027] Preferably, the method used for dimensionality reduction is principal component analysis.

[0028] Preferably, the step S1 further includes pre-processing, specifically: the four node information contained in each grid unit is arranged and combined in a manner such that any three nodes form a group to form a new topological unit.

[0029] Preferably, the step S4 specifically includes:

[0030] S4-1: Inserting original data: Insert the feature information obtained in S1 into the VTK module and save it as polygon geometry data type;

[0031] S4-2: Create a mapper: convert the input polygon geometry data into geometric primitives for rendering;

[0032] S4-3: Added actors: Combine geometric transformations to form a complete scene, and update actors in real time through callback functions;

[0033] S4-4: Added renderer: render the cutter head;

[0034] S4-5: Added a new window: Connect the operating system with the VTK rendering engine;

[0035] S4-5: Add an interactor: add clock response events and shield mouse events, and embed the VTK window into the PyQT platform; trigger the callback function bound to the clock response event, read the angle and working condition of the shield machine cutterhead at different times through the callback function, calculate the node stress and node coordinates at different times based on the prediction model in step S2 and the rotation formula in S3, and update the actors in VTK in real time to realize the visualization of the dynamic mechanical properties of the cutterhead.

[0036] The application of the technical solution of the present invention has the following beneficial effects:

[0037] (1) The dynamic mechanical performance visualization method provided by the present invention can solve the problem in the prior art that the three-dimensional model of the shield machine cutter head is relatively complex and the number of grids involved in the simulation calculation is huge (usually reaching the million level). Therefore, there is a lot of repetitive work when debugging the model and calculating the stress state under different working conditions, resulting in low process efficiency and long time consumption. The principle is: therefore, the node stress of all nodes under different working conditions is reduced to a new low-dimensional space matrix by a dimensionality reduction method, and a mapping relationship (functional relationship) between the dynamic parameters of the shield machine and the new space matrix is constructed. The new space matrix is quickly calculated by inputting the dynamic parameters of the shield machine under the new working condition. Subsequently, the node stress under different working conditions is calculated by inverse matrix of the principal component matrix. Compared with the previous method, there is no need to solve the differential equation of the finite element mesh model, and the calculation speed is faster, meeting the real-time requirements.

[0038] (2) In the present invention, by constructing a rotation formula for the rotation of the shield machine cutter head, the value of the node coordinate that changes with the cutter head rotation angle is calculated, thereby realizing the reconstruction of the cutter head during the movement process. The dynamic performance of the shield machine cutter head can be displayed after combining the rotated node coordinates with the corresponding stress information. Compared with the limitation of the traditional finite element simulation method that can only display the dynamic performance at different times under the same working condition, the present invention can realize the dynamic performance display of the shield machine cutter head under different working conditions, different postures and different times, and has better engineering applicability.

[0039] (3) The present invention reconstructs the finite element mesh model based on the VTK module; inserting the stress information corresponding to the nodes and performing color mapping and rendering achieves efficient and fast visualization. At the same time, the VTK module also provides an interface for the visualization interface. Based on work requirements, the VTK module can be embedded in the WPF or QT platform to produce a more aesthetically pleasing visualization interface, which has better scalability and compatibility than existing technologies.

[0040] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0042] Figure 1 A schematic flow chart of a method for visualizing the dynamic mechanical properties of a shield machine cutterhead provided by the present invention;

[0043] Figure 2 Schematic diagram of the process of step S2 in the present invention;

[0044] Figure 3 Schematic diagram of the process of step S4 in the present invention;

[0045] Figure 4 This is a visualization effect diagram of the dynamic mechanical properties of the shield machine cutter head in the present invention. DETAILED DESCRIPTION

[0046] To facilitate understanding of the present invention, the present invention will be described more fully below, along with preferred embodiments thereof. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0048] Example 1:

[0049] See also Figure 1 A method for visualizing the dynamic mechanical properties of a shield machine cutterhead is characterized by comprising:

[0050] S1: Construct a finite element mesh model of the shield machine cutterhead, obtain the result files of the finite element mesh model under different working conditions through Abaqus, and extract the characteristic information of the result files; the characteristic information includes node coordinate information, node information contained in the mesh unit, and node stress and displacement information; the result files include odb files and inp files; open the obtained odb files and inp files with python, and write a secondary development script based on python to read the node coordinate information contained in the inp file, the node information contained in the mesh unit, and the node stress information and displacement information contained in the odb file.

[0051] Since the structure used for subsequent color mapping and rendering in VTK is triangular facets, and tetrahedral units are used in simulation, the node information of the unit needs to be pre-processed. Specifically: each unit extracted from the inp file contains four node information, and every three node information constitutes a face. These four node information are arranged and combined in a way that any three nodes form a group to form a new topological unit. All units are saved after the above processing.

[0052] S2: Generate a sample matrix X through node coordinate information and node stress, reduce the dimension of the sample matrix X to generate a new space matrix C and a principal component matrix B, fit the shield machine dynamic parameters to the new space matrix C to obtain the function relationship C1, and calculate the inverse matrix B of the principal component matrix B. -1 After multiplying the functional relationship, the prediction model is obtained, and the stress of all nodes is predicted by the prediction model. Figure 2 Specifically:

[0053] S2-1: Generate a sample matrix X using node coordinate information and node stresses. Each row of the sample matrix X represents the node stresses of different nodes under the same operating condition, and each column of the matrix represents the node stresses of the same node under different operating conditions. In this case, assuming that the cutterhead has n nodes and m sample operating conditions, the size of the sample matrix is m×n, and the sample dimension is n. The sample matrix X is expressed as follows:

[0054]

[0055] Among them, x m,n represents the nodal stress at the nth node in the mth sample condition.

[0056] S2-2: Standardize the sample matrix. After standardizing the sample matrix X, you get the matrix X1. The standardization calculation formula is as follows:

[0057]

[0058]

[0059]

[0060] Among them, x i,j is the nodal stress in the sample matrix X, is the normalized data of the node stress in the sample matrix X, is the average value of the jth column in the sample matrix X, δ j is the variance of the jth column in the sample matrix X, the value range of j is greater than or equal to 1 and less than or equal to m, and the value of i is greater than or equal to 1 and less than or equal to n.

[0061] S2-3: Consider the matrix X1 as a matrix consisting of n column vectors, that is, X1 = (γ1,γ2,γ3,γ4...γ n ), where y n is a column vector, and an example is given where γ1=(x 1,1 ,x 2,1 ,x 3,1 ,x 4,1 ...x m,1 ), calculate the covariance matrix X2 of matrix X1, and assume that the sample condition m is less than the number of nodes n, so the size of the covariance matrix X2 is m×m, and the calculation formula is as follows:

[0062]

[0063] S2-4: Solve the eigenvalues of the covariance matrix X2, and arrange them in descending order to obtain m eigenvalues (α1, α2, α3, α4...α m ). And the eigenvectors corresponding to the above eigenvalues are solved as (β1,β2,β3,β4...β m ).

[0064] S2-5: The cumulative contribution rate of the first z eigenvalues of the transformed covariance matrix:

[0065]

[0066] When the cumulative contribution rate of the current z eigenvalues is greater than 95%, only the first z eigenvalues can be retained, and the transpose of the z eigenvectors corresponding to the first z eigenvalues (β1, β2, β3, β4...β m ) T Produce the principal component matrix B.

[0067] S2-6: Multiply the principal component matrix B by the sample matrix X to obtain the new spatial matrix C after dimensionality reduction. Fit the dynamic parameters of the shield machine (torque T, thrust F) with the new spatial matrix to obtain the functional relationship C1=f(T, F) between the new spatial matrix C and the torque T and thrust F.

[0068] S2-7: When the dynamic parameters of the shield machine (torque T1, thrust F1) under the new working condition are input, the corresponding new space matrix C2 is obtained according to the function relationship C1 = f(T, F), and the inverse matrix B of the principal component matrix is converted to -1 After multiplying by the new spatial matrix C2, the node stresses of all nodes under the new working condition are obtained, realizing the shield machine cutterhead stress calculation based on model order reduction.

[0069] S3: The shield machine's cutterhead primarily moves in rotation, so this invention primarily constructs a rotational kinematics formula for the cutterhead. Considering the cutterhead as a cylinder, with its center as the axis of rotation, a rotation formula for the angle θ around the axis is derived. This rotation formula is then used to calculate the coordinates of all nodes of the shield machine cutterhead after the rotation angle θ is reached.

[0070] S4: In the VTK module, the finite element mesh model is reconstructed according to the node information contained in the mesh unit in step S1 and the node coordinates rotated in step S3; the stress information corresponding to the node is inserted and color mapping and rendering are performed to realize the visualization of the dynamic mechanical performance of the shield machine cutter head, referring to Figure 3 , as follows:

[0071] S4-1: inserting raw data (Data): inserting the feature information of the cutter head obtained in S1 into the VTK module and saving it as a polygon geometry data type (vtkPolyData);

[0072] S4-2: Create a mapper: used to render polygon geometry data (vtkPolyData); convert the input data into geometric primitives (points, lines, polygons) for rendering;

[0073] S4-3: Added Actor: Combines geometric transformations to form a complete scene, and updates the actor in real time through callback functions;

[0074] S4-4: New Renderer (Render): Mainly responsible for the rendering process of the scene; render the cutter head;

[0075] S4-5: Added a new window (RenderWindow): connects the operating system to the VTK rendering engine;

[0076] S4-6: Added an interactor (RenderWindowInteractor): used to provide a platform-independent interactive mechanism for responding to clock events; add clock response events and shield mouse events, and embed the VTK window into the PyQT platform, so that the clock response event can be triggered even when the mouse does not stay on the VTK interface or clicks on the VTK interface. After adding the clock response event, the callback function bound to the clock event will be triggered at a certain time interval (0.01s in this embodiment). The angle and working condition of the shield machine cutterhead at different times are read in the callback function, and the prediction model built in S2 and the rotation formula built in S3 are added to calculate the node stress and node coordinates at different times, and the actor in VTK is updated in real time. In this way, the three-dimensional stress cloud map of the cutterhead can be reconstructed and visualized in real time according to different input working conditions, realizing the visualization of the dynamic mechanical properties of the cutterhead.

[0077] The above process can be used to reduce the order of calculation and visualize the dynamic mechanical performance of the cutter head. The final effect can be referred to Figure 4 When new angle data and working conditions are input, the cutterhead will rotate and update the stress value of the cutterhead. Compared with traditional finite element simulation, it has the advantages of high efficiency, fast speed and real-time dynamic simulation.

[0078] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for visualizing the dynamic mechanical properties of a shield machine cutterhead, characterized in that: include: S1: Construct a finite element mesh model of the shield machine cutterhead, obtain the result files of the finite element mesh model under different working conditions, and extract the characteristic information of the result files; The characteristic information includes node coordinate information, node information contained in the grid unit, and node stress and displacement information; S2: Generate sample matrix based on node coordinate information and node stress X , the sample matrix X Dimensionality reduction to generate a new space matrix C With the principal component matrix B , the shield machine dynamic parameters and the new space matrix C Fitting function relationship C 1. Through functional relationship C 1 Get the new space matrix under the new working condition C 2. The principal component matrix B The inverse matrix of B -1 Multiply by the new space matrix C 2. The prediction model is obtained and the stress of all nodes is predicted by the prediction model; S3: Take the center of the shield machine's cutterhead as the rotation axis and get the rotation angle around the axis The rotation formula is used to calculate the rotation angle All node coordinates of the cutterhead of the rear shield machine; S4: In the VTK module, the finite element mesh model is reconstructed based on the node information contained in the mesh cells in step S1 and the node coordinates rotated in step S3; the stress information corresponding to the nodes is inserted and color mapping and rendering are performed to visualize the dynamic mechanical properties of the shield machine cutterhead; The step S4 specifically comprises: S4-1: Inserting original data: Insert the feature information obtained in S1 into the VTK module and save it as polygon geometry data type; S4-2: Create a mapper: convert the input polygon geometry data into geometric primitives for rendering; S4-3: Added actors: Combine geometric transformations to form a complete scene, and update actors in real time through callback functions; S4-4: Added renderer: render the cutter head; S4-5: Added a new window: Connect the operating system with the VTK rendering engine; S4-5: Added new interactor: added clock response events and shielded mouse events, and embedded the VTK window into the PyQT platform; The callback function bound to the trigger clock response event is used to read the angle and working condition of the shield machine cutterhead at different times through the callback function. Based on the prediction model in step S2 and the rotation formula in S3, the node stress and node coordinates at different times are calculated, and the actors in VTK are updated in real time to realize the visualization of the dynamic mechanical properties of the cutterhead.

2. The dynamic mechanical properties visualization method according to claim 1, characterized in that: The result files include odb files and inp files.

3. The dynamic mechanical properties visualization method according to claim 1, characterized in that: The step S2 specifically comprises: S2-1: Generate sample matrix from node coordinate information and node stress ; S2-2: Standardize the sample matrix to obtain the matrix ; S2-3: Calculation Matrix The covariance matrix of , S2-4: Solving the covariance matrix The eigenvalues of are arranged in descending order to obtain m eigenvalues. , and solve the eigenvalue corresponding to the eigenvector as ; S2-5: Take the front z The cumulative contribution rate of the eigenvalue is greater than the set value, and the first z The corresponding eigenvalues z The transpose of the eigenvectors Generate principal component matrix B ; S2-6: The principal component matrix B Multiply by the sample matrix Get the new space matrix after dimensionality reduction C , the shield machine dynamic parameters are fitted with the new space matrix to obtain the functional relationship C 1; S2-7: When the dynamic parameters of the shield machine under new working conditions are input, according to the functional relationship C 1 Obtain the new space matrix corresponding to the new working condition C 2. The inverse matrix of the principal component matrix B -1 Multiply by the new space matrix C 2 and then the nodal stresses of all nodes under the new working condition are obtained.

4. The dynamic mechanical properties visualization method according to claim 3, characterized in that: The dynamic parameters of the shield machine include torque and thrust.

5. The dynamic mechanical properties visualization method according to claim 4, characterized in that: The expression of cumulative contribution rate is as follows: ； in, Indicates the first eigenvalues.

6. The dynamic mechanical properties visualization method according to claim 1, characterized in that: The method used for dimension reduction is principal component analysis.

7. The dynamic mechanical properties visualization method according to claim 1, characterized in that: The step S1 also includes pre-processing, specifically: the four node information contained in each grid unit is arranged and combined in a manner such that any three nodes form a group to form a new topological unit.

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