Cylinder cover static strength optimization method based on joint simulation technology

Abstract

The invention discloses a cylinder cover static strength optimization method based on a joint simulation technology, and belongs to the field of cylinder covers for internal combustion engines. The implementation method comprises the following steps of: quickly updating a cylinder cover model, drawing a self-adaptive finite element grid of the cylinder cover, quickly updating a cylinder cover assembly body model and automatically simulating and analyzing the static strength performance of the cylinder cover by virtue of data transmission among a plurality of modules; static strength performance analysis of various cylinder covers of different structures is achieved by repeatedly and automatically operating the pre-processing and solving process, a sample data set representing the corresponding relation between the cylinder cover structure and the static strength performance is formed, and optimal parameters are selected as optimization results for cylinder cover production and application. By means of the method, the problem that a large amount of manual operation is needed in a traditional method for optimizing the static strength performance of the air cylinder cover can be solved, meanwhile, it can be guaranteed that the air cylinder cover has qualified grid quality during automatic grid drawing, the time needed for updating an air cylinder cover assembly model is saved, and the precision and efficiency for optimizing the static strength of the air cylinder cover are improved.

Description

Technical Field

[0001] The present invention relates to a cylinder head optimization method, and in particular to a method for optimizing cylinder head parameters based on UG, Hypermesh, Abaqus and Isight software joint simulation technology, which is suitable for optimizing the static strength performance and lightweight degree of a cylinder head model, and belongs to the field of energy and power engineering, and cylinder heads for internal combustion engines. Background Art

[0002] The cylinder head is one of the main parts of a diesel engine. It is used to seal the top of the cylinder and together with the piston top and the inner wall of the cylinder, it forms the combustion space of the internal combustion engine. During the operation of the diesel engine, the cylinder head is subjected to a large mechanical load (such as bolt tightening force, gas explosion pressure, etc.). Therefore, how to achieve a lightweight design of the cylinder head while ensuring the static strength performance of the cylinder head has always been a major problem in the development of diesel engines. With the continuous improvement of the power density of diesel engines, the load borne by the cylinder head will also become larger and larger, and the design of the cylinder head will become more and more difficult. On the one hand, in order to meet the design requirements of high combustion peak pressure of future power units, designers need to adjust the material distribution of each area of ​​the cylinder head to ensure the final static strength performance of the cylinder head; on the other hand, in order to meet the design requirements of high power density, designers also need to reduce the use of materials as much as possible and reduce the weight of the cylinder head to ensure that the design goal of lightweighting the entire machine is achieved.

[0003] In the traditional process, the optimization of the static strength performance of the cylinder head is mainly to determine the stress and displacement data of the cylinder head corresponding to a certain structural scheme through simulation, analyze the data and adjust the structure in combination with the weight of each scheme to complete the optimization of the cylinder head. For example, the optimization method given in the mature cylinder head thermal-mechanical coupling simulation analysis and optimization technology [1] (see Zhang Min, Zhang Yi, Zhang Qinxiu. Cylinder head structure optimization design based on thermal-mechanical coupling [J]. Combined Machine Tool and Automation Processing Technology, 2017, (6): 126-129.) is based on the orthogonal experimental design method to create multiple groups of experiments and manually calculate the structural parameter values ​​corresponding to each experimental sample point. When there are fewer parameters involved and the variation level of each parameter is small, the workload and calculation time of the orthogonal experimental design method are not large. However, when the structural design requirements are higher and multiple features need to be optimized at the same time, the total number of experiments created by the orthogonal experimental design method will increase exponentially, and the workload and calculation time will also increase exponentially. At this point, manually editing calculation tasks and performing trial calculations using traditional methods can no longer meet the ever-increasing demands of optimization design tasks. There is an urgent need to research new optimization methods that are highly automated and more efficient.

[0004] In response to the need to establish highly automated calculation processes, a variety of parameter optimization software such as Isight have emerged. Isight has already appeared in many other simple structure optimization fields. For example, the optimization process shown in the prior art [2] (Fan Jiang, Zeng Weiwei, Wang Rongqiao, Shen Xiuli, Chen Zhiying. Optimization design of turbine blade shroud based on iSIGHT [J]. Journal of Aerospace Power, 2011, Vol. 26 (4): 745-751.) has demonstrated the construction method of automated optimization process for models such as turbine blades with relatively regular surfaces and simple geometric expressions. However, at present, this type of method is still rarely used in the static strength optimization of cylinder heads. The cylinder head design is different from the design of these geometrically simple parts in the following ways: (1) The cylinder head has a more complex geometry, with multiple structural dimensions affecting each other. It is more difficult to establish its parametric model and it is difficult to obtain a reasonable range of parameter changes. (2) The cylinder head will continuously generate new models as its structural parameters change. Therefore, before each round of simulation analysis, it is necessary to draw a finite element mesh for the cylinder head model and assemble the mesh model of the cylinder head with the mesh models of other parts related to the cylinder head. This process is more difficult than for geometrically smooth blades, and it is more difficult to simplify the finite element model. (3) In each round of simulation analysis, it is necessary to reassign the boundary conditions and loads applied to the cylinder head. Since the cylinder head mesh model used in each round of simulation analysis is constantly changing, it is difficult to reassign the boundary conditions and loads through the classic method of associating mesh numbers. Summary of the invention

[0005] The purpose of the present invention is to provide a cylinder head static strength optimization method based on joint simulation technology, which realizes the rapid update of the cylinder head model, cylinder head adaptive finite element mesh drawing, cylinder head assembly model rapid update and cylinder head static strength performance automatic simulation analysis by means of data transmission between multiple modules, and realizes the static strength performance analysis of cylinder heads with various structures by repeatedly and automatically running the pre- and post-processing and solution processes, forms a sample data set that characterizes the corresponding relationship between the cylinder head structure and the static strength performance, and selects the optimal parameter value as the optimization result for cylinder head production application. The present invention can solve the problem that the traditional cylinder head static strength performance optimization method requires a lot of manual operation, and at the same time can ensure that the cylinder head has qualified mesh quality when the mesh is automatically drawn, and updates the cylinder head assembly model based on the mesh model replacement algorithm, saving the time required for updating the cylinder head assembly model, and fully improving the accuracy and efficiency of the cylinder head static strength performance optimization work.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] The present invention discloses a cylinder head static strength optimization method based on joint simulation technology. The cylinder head geometric model is constructed based on a parametric modeling method, and the structural shape of the cylinder head geometric model is controlled by using a cylinder head expression to realize rapid updating of the cylinder head geometric model; the cylinder head model is finite element meshed based on an automated meshing method, and the shape of the low-quality mesh is adjusted based on a mesh quality repair algorithm to ensure the mesh quality of the cylinder head mesh model; the cylinder head component in the cylinder head assembly mesh model is replaced with the cylinder head mesh model with an updated structural shape based on a mesh model replacement algorithm, and the selected boundary condition area on the cylinder head component is synchronized to the updated cylinder head mesh model; based on the cylinder head static strength The simulation analysis is set up according to the degree analysis method, and the macro command is used to drive the solver to perform automated static strength simulation analysis of the cylinder head, so as to obtain the stress distribution and displacement distribution of each position on the cylinder head, and extract the mass of the cylinder head model; a sample space is constructed based on the parameter variation range of the cylinder head geometric model, and each sample point is repeatedly and independently subjected to automated simulation analysis, and a sample data set characterizing the correspondence between the cylinder head structure and the static strength performance is obtained after screening and removing the data with non-convergence and substandard accuracy; a comprehensive evaluation function is established, and the stress, displacement and mass data corresponding to each sample point are comprehensively weighed and scored, and a group of samples with the best scores are selected as the structural optimization results of the cylinder head, that is, the static strength performance optimization of the cylinder head based on the joint simulation technology is realized.

[0008] The present invention discloses a cylinder head static strength optimization method based on joint simulation technology, comprising the following steps:

[0009] Step 1: Parametrically model the cylinder head to obtain a cylinder head parametric model. Determine the initial value and boundary value of each parameter of the cylinder head parametric model, and gradually modify the cylinder head parametric model by combining global parameter changes with modification error reporting features until the cylinder head model meets the preset stability qualification requirements. By calling the API function of the UG software, the cylinder head parametric model can be automatically updated with one click, thereby improving the update efficiency of the cylinder head parametric model.

[0010] The specific implementation method of step one is:

[0011] S11: Select UG as the modeling platform to complete the parametric modeling of the cylinder head. Use the stretching or rotation modeling method to establish the external features of the cylinder head, and the features include the top plate, the bottom plate, and the side wall. Use the projection curve modeling method to draw the feature lines on the wall surfaces of the cylinder head intake and exhaust ducts, and use the fitting surface modeling method to connect the closed projection curves to generate the surface features of the intake and exhaust duct walls. The surface features that constitute the intake and exhaust ducts are stitched to form a solid, and the external features of the cylinder head are subtracted from the intake and exhaust duct entities by Boolean operations to obtain a cylinder head model that completes the airway modeling. Use the stretching, rotation, punching or rounding modeling method to establish the assembly features of the cylinder head on the cylinder head model that completes the airway modeling, and the features include fastening threaded holes, intake and exhaust pipe assembly holes, inlet and outlet assembly holes, injector assembly holes, and locating pin holes. The water inlet and outlet of the flow channel are drawn on the cylinder head with completed assembly feature modeling by using the stretching modeling method. Starting from the water inlet, the flow channel geometry of the cylinder head is drawn by stretching, rotating, and stitching the surface at the position where the wall thickness on the cylinder head model is greater than the minimum wall thickness requirement of the process, until the flow channel geometry connects the water inlet and the water outlet, and the flow channel geometry is arranged at the position where the wall thickness is greater than the minimum wall thickness requirement of the process. When setting the size of the flow channel geometry, the minimum wall thickness requirement of the processing technology must be strictly met. All the flow channel geometries are summed by Boolean operation to obtain the flow channel entity of the cylinder head model, and then the cylinder head model with completed airway modeling and the flow channel entity of the cylinder head model are subtracted by Boolean operation to obtain the cylinder head model with completed airway and flow channel modeling. After the external features, airways, assembly features and runners of the cylinder head are modeled, weight-reducing geometries are established by stretching, rotating and stitching surfaces at locations on the top plate, bottom plate and side walls of the cylinder head that are not involved in assembly and sealing, and the size of the weight-reducing geometries is associated with the size of the runner geometries to always ensure that the minimum wall thickness on the cylinder head is greater than the minimum wall thickness requirement of the process. Boolean operations are used to subtract the cylinder head with completed assembly feature modeling from all weight-reducing geometries to obtain a cylinder head model that has completed parametric modeling.

[0012] S12: Setting parameter initial values ​​and parameter boundary values ​​for structural parameters on the cylinder head parametric model. One of the parameter boundary values ​​of the cylinder head parametric model is set to the limit parameter when the wall thickness at each position of the cylinder head is the minimum wall thickness requirement of the process, and the other is set to other limit dimensions under the cylinder head design requirements, wherein the cylinder head design requirements include that the hydraulic diameter at each position of the flow channel shall not be less than the limit dimension that causes flow obstruction, the narrowest part of the cylinder head surface shall not be less than one-third of the minimum wall thickness requirement of the process, and there shall be no interference between the cylinder head flow channel, air channel, assembly feature, weight reduction feature and external wall surface. Some cylinder head dimensions are the reference dimensions set when the cylinder head parametric model is modeled, and the reference dimension parameter initial value is set to the initial value used when the cylinder head parametric model is modeled, and the reference dimension does not change when the cylinder head parametric model is updated. After the upper and lower boundary values ​​of the parameter change are determined for the parameters other than the reference dimensions, the initial values ​​of the parameters other than the reference dimensions are set to the median of the upper boundary value and the lower boundary value, so as to reduce the probability of error reporting when the cylinder head parametric model is updated.

[0013] S13: The cylinder head parametric model is gradually modified by the method of "combining global parameter changes with error feature modification". When the cylinder head parametric model selects parameter values ​​within the parameter variation range obtained in S12 and substitutes them into the expression to update the model, and the model update exceeds the preset number of times and still does not report an error, it is determined that the stability of the cylinder head parametric model meets the conditions required for optimization. The function of this step S13 is to repeatedly test whether the cylinder head parametric model reports an error under different parameter values, and modify the error feature to gradually improve the cylinder head parametric model. Name all parameters except the reference size in the cylinder head parametric model expression, configure the data interface between Excel and UG, and import the parameter names of the cylinder head except the reference size and their corresponding parameter variation range into an Excel table, use a random number formula to randomly select a parameter value for all parameters except the reference size within the variation range, and then select all newly generated random parameter values ​​together with the names of all parameters except the reference size as the data source of the cylinder head parametric model, and use the Excel table to drive UG to update the model many times to test the parameter stability of the cylinder head parametric model under random parameter values. The parameter stability of the cylinder head parametric model is determined to be qualified when no error occurs when the cylinder head parametric model is updated for a preset number of consecutive times using random parameter values; if an error occurs, the error feature prompted in the UG software is modified or the dimensional variation range corresponding to the feature is modified until the cylinder head parametric model is updated for a preset number of consecutive times using random parameter values ​​without any error.

[0014] S14: Automatically update the cylinder head model by calling the API function of UG. Call the API function of UG to read the cylinder head parametric model path, read the cylinder head parametric model expression path, automatically update the cylinder head parametric model using the expression parameter value, and save the cylinder head parametric model corresponding to the new parameter value, so as to realize the one-key automatic update of the cylinder head parametric model.

[0015] Step 2: Perform 2D meshing on the cylinder head parameterized model, repair the meshes with unqualified mesh quality, and then draw the cylinder head 3D mesh model. Assemble the cylinder head 3D mesh model and various components related to the service status of the cylinder head, draw structured meshes for each component related to the service status of the cylinder head, and select mesh faces on the cylinder head 3D mesh model and the 3D mesh models of each component related to the service status of the cylinder head as the main face and the slave face of the boundary conditions to be applied during the static strength analysis of the cylinder head. Perform static strength analysis of the cylinder head assembly to obtain the stress and displacement distribution at various positions on the cylinder head. Perform mesh independence analysis on the static strength calculation of the cylinder head, and select a mesh size with a short calculation time and a deviation of the stress and displacement calculation results from the calculation results at other mesh sizes that is less than a preset threshold as the finite element mesh size used for optimization. The short calculation time refers to a calculation time that is shorter than the preset threshold.

[0016] The specific implementation method of step 2 is:

[0017] S21: Mesh the cylinder head parametric model separately. Use the minimum wall thickness requirement of the process as the initial mesh size for mesh drawing, import the cylinder head parametric model into Hypermesh, set the mesh size to the minimum wall thickness requirement of the process, and use the surface deviation meshing method to divide it into 2D meshes. Repair meshes with unqualified mesh quality based on the QIoptimization mesh repair algorithm and the size corrected mesh repair algorithm, and use the place node method to modify the meshes that are difficult to adjust with the mesh repair algorithm to qualified mesh quality, and obtain a high-quality cylinder head 2D mesh model. Set the mesh size to the minimum wall thickness requirement of the process, use the tetramesh meshing method to draw a 3D mesh, and obtain a cylinder head 3D mesh model.

[0018] S22: Establish a mesh model of the cylinder head assembly. Import the cylinder head 3D mesh model into Hypermesh, import various components related to the service status of the cylinder head, and assemble the various components related to the service status of the cylinder head with the cylinder head 3D mesh model according to the engine assembly requirements, wherein the components include an engine body, a bushing, a gasket, and fastening bolts. Perform 2D structured mesh division on the various components related to the service status of the cylinder head using the automesh method, and perform 3D structured mesh division on the components related to the service status of the cylinder head using the solidmap method, to obtain 3D mesh models of the various components related to the service status of the cylinder head. Based on the cylinder head static strength analysis method, mesh surfaces are selected on the cylinder head 3D mesh model and the 3D mesh models of various components related to the cylinder head service status as the main surface and the secondary surface of the boundary conditions to be applied during the cylinder head static strength analysis. The main surface and the secondary surface include the main and secondary surfaces of the contact relationship between the bolt and the cylinder head, the main and secondary surfaces of the connection relationship between the bolt and the body assembly hole, the main and secondary surfaces of the contact relationship between the cylinder head and the body, and the action surface of the explosion pressure of the combustion chamber. The material properties of the cylinder head 3D model and the 3D mesh models of various components related to the cylinder head service status are set and saved to obtain the mesh model of the cylinder head assembly.

[0019] S23: Set up simulation based on the static strength analysis method of the cylinder head, perform static strength analysis of the cylinder head assembly, and obtain the stress and displacement distribution at each position on the cylinder head. Import the mesh model of the cylinder head assembly into Abaqus, set the explosion pressure and bolt preload force that the cylinder head is subjected to during operation, select the contact pair between the bolt and the cylinder head and the contact pair between the cylinder head and the engine body to set the contact relationship and use the small slip and small deformation calculation method, select the connection pair between the bolt and the engine body assembly hole to set the coupling relationship and use the small slip and small deformation calculation method, and set the bottom of the engine body as a fixed support constraint. Select the simulation analysis type as static analysis, set the initial iteration step and maximum iteration step of the simulation according to the computing power conditions, submit the simulation calculation and obtain the stress distribution and displacement distribution results of the cylinder head in the service state.

[0020] S24: Perform mesh independence analysis for static strength calculation of cylinder head. Starting from the initial value of the mesh size required by the minimum wall thickness of the process, expand or reduce the mesh size used when drawing the cylinder head 2D mesh model and the cylinder head 3D mesh model, import the cylinder head 3D model into the cylinder head assembly mesh model, update the assembly, and calculate the static strength simulation results of the cylinder head under different mesh sizes. Compare the effects of different mesh sizes on the calculation time and stress and displacement calculation results, and select a mesh size with a short calculation time and a deviation of the stress and displacement calculation results from the calculation results under other mesh sizes that is less than a preset threshold as the finite element mesh size used for optimization, and complete the mesh independence analysis. The short calculation time refers to a calculation time that is shorter than the preset threshold.

[0021] Step 3: Adjust the structural parameters of the cylinder head model to generate a cylinder head model with parameters different from the initial values. Record the script for the cylinder head mesh drawing phase in Hypermesh and the script for the cylinder head component update phase in the cylinder head assembly model. Record the script for the cylinder head static strength calculation phase in Abaqus and extract the performance index data that can characterize the static strength of the cylinder head and the quality of the cylinder head.

[0022] The specific implementation method of step three is:

[0023] S31: Adjust the structural parameters of the cylinder head model, automatically update the cylinder head model and the cylinder head cooling channel model, and generate a cylinder head model with parameters different from the initial values. Modify all parameters except the reference size in the expression of the cylinder head parameterized model, call the UG API function, read the cylinder head parameterized model expression, and automatically update the cylinder head model and the cylinder head cooling channel model with one click.

[0024] S32: Record the script for the cylinder head mesh drawing process. Based on the mesh size determined after mesh independence analysis, start script recording in Hypermesh, edit the mesh quality judgment criteria, cancel the algorithm's detection of the maximum mesh size and the minimum mesh size, and improve the repair rate of low-quality meshes. Use the surface deviation mesh division method to divide it into 2D meshes, repair meshes with unqualified mesh quality based on the QI optimization mesh repair algorithm and the size corrected mesh repair algorithm, and use the place node method to modify the mesh that is difficult to adjust by the mesh repair algorithm to a qualified mesh quality, and obtain a high-quality cylinder head 2D mesh model. Use the tetramesh mesh division method to draw a 3D mesh to obtain a cylinder head 3D mesh model. Complete the drawing of the cylinder head mesh model and obtain the script for the cylinder head mesh drawing process.

[0025] S33: Record the script for updating the cylinder head components in the cylinder head assembly model. Start the script recording in Hypermesh, import the cylinder head assembly mesh model, replace the cylinder head components in the cylinder head assembly mesh model with the cylinder head 3D mesh model with updated structure shape based on the mesh model replacement algorithm, export the new cylinder head assembly mesh model and obtain the script for updating the cylinder head mesh model.

[0026] S34: Record the script for the static strength calculation of the cylinder head. Start the script recording in Abaqus, import the mesh model of the cylinder head assembly, set the explosion pressure and bolt preload that the cylinder head is subjected to during operation, select the contact pairs between the bolt and the cylinder head and the contact pairs between the cylinder head and the engine body to set the contact relationship and use the small slip and small deformation calculation method, select the connection pairs between the bolt and the engine body assembly hole to set the coupling relationship and use the small slip and small deformation calculation method, and set the bottom of the engine body as a fixed support constraint. Select the simulation analysis type as static analysis, set the initial iteration step and the maximum iteration step of the simulation according to the computing power conditions, submit the simulation calculation and obtain the stress distribution and displacement distribution results of the cylinder head in the service state. Extract the mass of the cylinder head and the index data that characterizes the static strength performance of the cylinder head and obtain the script for the static strength calculation of the cylinder head. The performance index data that can characterize the static strength of the cylinder head include the maximum Mises stress, the maximum displacement, the maximum partial displacement in the three positive directions, and the stress gradient.

[0027] Step 4: Build a cylinder head static strength optimization model based on co-simulation technology, use the Latin hypercube algorithm to plan the sample space for cylinder head static strength optimization, call the script recorded during the cylinder head static strength calculation process through batch commands, and automatically run the cylinder head parameterized model update, cylinder head mesh drawing, cylinder head component update in the cylinder head assembly model, cylinder head static strength simulation analysis, and cylinder head static strength performance index data extraction in the cylinder head static strength optimization test design process to obtain a sample data set that characterizes the corresponding relationship between the cylinder head structure and static strength. Establish a comprehensive evaluation function, comprehensively weigh multiple cylinder head static strength performance index data to score each sample point, select the best scoring group of samples as the optimization result, and obtain the optimal cylinder head structure in the sample space, that is, to achieve cylinder head static strength optimization based on co-simulation technology.

[0028] The specific implementation method of step 4 is:

[0029] S41: Build a cylinder head static strength optimization model in Isight, set the total number of samples according to the computing power conditions, and use the Latin hypercube algorithm to plan the sample space for cylinder head static strength optimization, so that the sample points are evenly distributed in the high-dimensional Euclidean space to ensure the quality of sample data. Call the commands for updating the cylinder head parametric model, drawing the cylinder head mesh, updating the cylinder head components in the cylinder head assembly model, simulating and analyzing the static strength of the cylinder head, and extracting the static strength performance index data of the cylinder head through batch commands. After the settings are completed, the cylinder head static strength optimization model is automatically run to obtain a sample data set that characterizes the corresponding relationship between the cylinder head structure and the static strength performance.

[0030] S42: Establish a comprehensive evaluation function, comprehensively consider the floating degree and importance of multiple cylinder head static strength performance indicators, and score the static strength of each sample point. As a preferred embodiment, the comprehensive evaluation function is shown in the following formula:

[0031]

[0032] Among them, g j is the comprehensive score of the jth evaluated sample point, λ i is the weight of the i-th evaluated indicator, y ij is the actual value of the i-th evaluated indicator of the j-th evaluated sample point, Z i is the ideal value of the i-th evaluated indicator of the evaluated sample point, σ i is the standard deviation of the i-th evaluated indicator data, and n is the total number of indicators evaluated at the sample point.

[0033] The weight of the i-th evaluated indicator can be calculated using the following formula:

[0034]

[0035] C i is the significance coefficient of the ith indicator, C i The larger the value is, the greater the impact of the i-th indicator on the comprehensive evaluation results, and the higher the weight is. i The standard deviation σ i and the correlation coefficient R i The product of is:

[0036] C i =σ i R i (3)

[0037] Standard deviation i Calculated using the following formula:

[0038]

[0039] In the formula, m is the total number of sample points used to calculate the standard deviation, x ij is the dimensionless data of the i-th performance index of the j-th sample point, is the dimensionless data average of the i-th performance indicator. The dimensionless data of the i-th performance indicator at the j-th sample point can be dimensionlessized by the following formula to obtain the data average:

[0040]

[0041] Correlation coefficient R i It can be calculated using the following formula:

[0042]

[0043] r ik is the linear correlation coefficient between the i-th indicator and the k-th indicator, which can be calculated using the following formula:

[0044]

[0045] After calculating all the above variables according to the sample data set, each sample point is scored through the comprehensive evaluation function, and the group of samples with the best scores are selected as the optimization results to obtain the optimal cylinder head structure in the sample space, that is, to achieve the optimization of the static strength performance of the cylinder head based on the joint simulation technology.

[0046] The method further includes step 5, performing process adaptability design according to the optimal cylinder head structure obtained in step 4, and obtaining a cylinder head design scheme that meets production constraints. Compared with the cylinder head before optimization, the cylinder head manufactured by the cylinder head design scheme can improve static strength performance, reduce the maximum stress of the cylinder head, reduce deformation effect, improve material distribution, and significantly achieve lightweight.

[0047] Beneficial effects:

[0048] 1. The present invention discloses a cylinder head static strength optimization method based on joint simulation technology, which uses a parametric modeling method to build a parametric model of the cylinder head, thereby achieving the effect of directly controlling the structural shape of the cylinder head through the expression of the cylinder head parametric model, and improving the efficiency of modifying and updating the cylinder head parametric model.

[0049] 2. The present invention discloses a cylinder head static strength optimization method based on joint simulation technology, which determines the initial value and upper and lower boundary values ​​of each parameter of the cylinder head parametric model, and gradually modifies the cylinder head parametric model by "combining global parameter changes with modification error reporting features", thereby ensuring that the cylinder head model has sufficient stability and achieving the effect that the cylinder head parametric model can be stably updated when any value of the cylinder head parametric model expression within the parameter variation range is taken.

[0050] 3. The present invention discloses a cylinder head static strength optimization method based on joint simulation technology, which realizes one-key automatic update of the cylinder head parametric model by calling the API function of UG software, omits the step of opening the UG graphical window and then modifying the cylinder head parametric model, improves the update efficiency of the cylinder head parametric model, meets the necessary conditions for automating the cylinder head static strength calculation process, and improves the accuracy and efficiency of the cylinder head static strength optimization.

[0051] 4. The present invention discloses a cylinder head static strength optimization method based on joint simulation technology. Based on a mesh model replacement algorithm, the cylinder head components in the cylinder head assembly mesh model are replaced with a cylinder head 3D mesh model with an updated structural shape, thereby realizing rapid updating of the cylinder head assembly model. This can solve the problem that the cylinder head assembly is difficult to automatically update in the cylinder head static strength automatic calculation process, and significantly improve the optimization efficiency of the cylinder head.

[0052] 5. The present invention discloses a cylinder head static strength optimization method based on joint simulation technology, which completes the preliminary static strength calculation of the cylinder head under the grid size required by the process for the minimum wall thickness and performs a grid independence analysis of the static strength calculation of the cylinder head. A grid size with a short calculation time and a small deviation between the calculation result and the calculation result under other grid sizes is selected as the finite element grid size used in the optimization, thereby ensuring the accuracy of the cylinder head optimization result and significantly saving the time cost of the cylinder head static strength optimization link.

[0053] 6. The present invention discloses a method for optimizing the static strength of a cylinder head based on joint simulation technology, which records the script of the cylinder head mesh drawing link and the script of the automatic update link of the cylinder head components in the cylinder head assembly model in Hypermesh. The script of the cylinder head static strength calculation link is recorded in Abaqus and the performance index data that can characterize the static strength of the cylinder head and the quality of the cylinder head are extracted, so as to realize the accurate reproduction and automatic operation of the finite element mesh division work and the simulation analysis setting work in the process of static strength performance calculation of the cylinder head, and improve the efficiency of static strength optimization of the cylinder head.

[0054] 7. The present invention discloses a cylinder head static strength optimization method based on joint simulation technology. The cylinder head static strength optimization model is built based on the joint simulation technology. The Latin hypercube algorithm is used to plan the sample space during the static strength optimization of the cylinder head. The total number of samples can be set according to the computing power conditions for experimental design. The sample points in the sample data set used for the static strength optimization of the cylinder head are sufficiently uniform, and the sample number and computing time cost are controllable.

[0055] 8. The present invention discloses a cylinder head static strength optimization method based on joint simulation technology. Based on the joint simulation technology, a cylinder head static strength performance optimization model is built. The script recorded during the cylinder head static strength calculation process is called through a batch command to automatically run the cylinder head parameterized model update, cylinder head mesh drawing, cylinder head component update in the cylinder head assembly model, cylinder head static strength simulation analysis, and cylinder head static strength performance index data extraction operations, so as to realize the effect of automatically calculating the sample point structural parameters in the sample space corresponding to the cylinder head static strength performance, and improve the efficiency of cylinder head optimization. During the calculation process, the model will automatically filter and remove sample points with non-convergence of calculation and substandard mesh quality to ensure the quality of the sample data set.

[0056] 9. The present invention discloses a cylinder head static strength optimization method based on joint simulation technology, establishes a comprehensive evaluation function, weighs multiple cylinder head static strength performance indicators to score the static strength performance of each sample point, and realizes a comprehensive evaluation of the cylinder head static strength performance, ensuring that the cylinder head static strength optimization result has the greatest improvement in comprehensive performance, and each sub-indicator can be balanced. The cylinder head processed using the optimization result scheme selected by the comprehensive evaluation function has a longer service life and better load resistance, and effectively achieves lightweight. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a flow chart of a cylinder head static strength optimization method based on joint simulation technology of the present invention;

[0058] Figure 2 A parameterized model of a cylinder head established in combination with the optimization method of the present invention;

[0059] Figure 3 This is the completed 3D mesh model of the cylinder head;

[0060] Figure 4 It is the cylinder head assembly mesh model formed after all parts are assembled and meshed;

[0061] FIG5 is a cylinder head temperature field cloud diagram obtained by using a 5 mm grid size after the grid independence analysis is performed in Example 1 to obtain the optimal grid size of 5 mm, wherein: FIG5(a) is the cylinder head stress distribution result, and FIG5(b) is the cylinder head displacement distribution result;

[0062] Figure 6 This is a workflow diagram for building a cylinder head static strength optimization model in Isight.

[0063] Figure 7 It is the optimized cylinder head model structure. DETAILED DESCRIPTION

[0064] The invention is further described below with reference to the accompanying drawings and embodiments.

[0065] Embodiment 1:

[0066] like Figure 1 The figure shows a cylinder head static strength optimization method based on the joint simulation technology disclosed in this embodiment, and the specific implementation steps are as follows:

[0067] Step 1: Parametrically model the cylinder head to obtain a cylinder head parametric model. Determine the initial value and boundary value of each parameter of the cylinder head parametric model, and gradually modify the cylinder head parametric model by combining global parameter changes with modification error reporting features until the cylinder head model meets the preset stability qualification requirements. By calling the API function of the UG software, the cylinder head parametric model can be automatically updated with one click, thereby improving the update efficiency of the cylinder head parametric model.

[0068] The specific implementation method of step one is:

[0069] Step 1.1: Use the stretching or rotation modeling method in UG to create the top plate, bottom plate and side wall of the cylinder head. Use projection curves to draw the feature lines on the cylinder head intake and exhaust duct walls, use fitting surfaces to generate the surface features of the intake and exhaust duct walls, stitch the surface features to form entities, and use Boolean operations to subtract the air duct from the cylinder head top plate, bottom plate and side wall to complete the intake and exhaust duct modeling. Use stretching, rotation, punching or rounding modeling methods to create the 22mm fastening threaded holes, 8.5mm intake and exhaust pipe assembly holes, 42mm injector assembly holes and 20mm locating pin holes of the cylinder head. The water inlet and outlet of the flow channel are drawn on the cylinder head by stretching modeling. Starting from the water inlet, 20 flow channel geometries of the cylinder head are drawn by stretching, rotating, and stitching surfaces at the position where the wall thickness of the cylinder head model is greater than 6mm, until the water inlet and the water outlet are connected and the flow channel is spread throughout the cylinder head. The flow channel geometries are summed by Boolean operation to obtain the flow channel entity of the cylinder head model. The cylinder head model that has completed the air channel modeling is subtracted from the flow channel entity of the cylinder head model by Boolean operation to obtain the cylinder head model that has completed the air channel and flow channel modeling; 6 weight-reducing geometries are established by stretching, rotating, and stitching surfaces at positions on the top plate, bottom plate, and side wall of the cylinder head that do not involve assembly and sealing, and the size of the weight-reducing geometries is associated with the size of the flow channel geometries to always ensure that the minimum wall thickness on the cylinder head is greater than 6mm. The cylinder head that has completed the assembly feature modeling is subtracted from all weight-reducing geometries by Boolean operation to obtain the cylinder head model that has completed the parametric modeling as shown in the figure. Figure 2 shown.

[0070] Step 1.2: Set the initial values ​​of the 96 reference dimension parameters constituting this embodiment as the initial values ​​used in the parametric modeling of the cylinder head, and then set their boundary values ​​equal to the reference values. These dimensions do not change when the model is updated. Among the 100 parameters other than the reference dimensions, this embodiment only optimizes the parameters controlling the flow channel shape. After determining the upper and lower boundary values ​​of the parameter changes for the 31 parameters controlling the flow channel shape, set the initial values ​​of the parameters of the 31 parameters controlling the flow channel shape to the median of the upper boundary value and the lower boundary value.

[0071] Step 1.3: Configure the data interface between Excel software and UG software, import the names of the 31 parameters that control the flow channel shape and their corresponding parameter variation ranges into the Excel table, insert a random number formula to randomly select a parameter value within the variation range for the 31 parameters that control the flow channel shape, and then select all the random parameter values ​​generated by the random number formula together with the names of the 31 parameters that control the flow channel shape as the data source of the cylinder head parametric model. Use the Excel table to drive UG to update the model to test the parameter stability of the cylinder head parametric model under random parameter values. The parameter stability of the cylinder head parametric model is considered qualified when no error occurs when the cylinder head parametric model is updated with random parameter values ​​for ten consecutive times.

[0072] Step 1.4: Call the UG API function to achieve one-key automatic update of the cylinder head parameterized model and the cylinder head cooling channel model in this embodiment.

[0073] Step 2: Perform 2D meshing on the cylinder head parameterized model, repair the meshes with unqualified mesh quality, and then draw the cylinder head 3D mesh model. Assemble the cylinder head 3D mesh model and various components related to the service status of the cylinder head, draw structured meshes for each component related to the service status of the cylinder head, and select mesh faces on the cylinder head 3D mesh model and the 3D mesh models of each component related to the service status of the cylinder head as the main face and the slave face of the boundary conditions to be applied during the static strength analysis of the cylinder head. Perform static strength analysis of the cylinder head assembly to obtain the stress and displacement distribution at various positions on the cylinder head. Perform mesh independence analysis on the static strength calculation of the cylinder head, and select a mesh size with a short calculation time and a deviation of the stress and displacement calculation results from the calculation results at other mesh sizes that is less than a preset threshold as the finite element mesh size used for optimization. The short calculation time refers to a calculation time that is shorter than the preset threshold.

[0074] The specific implementation method of step 2 includes the following steps:

[0075] Step 2.1: Use 6mm as the initial mesh size for mesh drawing, import the cylinder head parametric model into Hypermesh, set the mesh size to 6mm, and use the surface deviation meshing method to divide it into 2D meshes. Use the QI optimization mesh repair algorithm and the size corrected mesh repair algorithm to repair meshes with unqualified mesh quality, and use the place node method to modify the meshes that are difficult to adjust with the mesh repair algorithm to qualified mesh quality, and obtain a high-quality cylinder head 2D mesh model. Set the mesh size to 6mm, use the tetramesh meshing method to draw a 3D mesh, and obtain the cylinder head 3D mesh model as shown below. Figure 3 shown.

[0076] Step 2.2: Import the cylinder head 3D mesh model into Hypermesh, import the engine block, bushing, gasket and fastening bolts, and assemble the engine block, bushing, gasket and fastening bolts with the cylinder head 3D mesh model. Set the mesh size to 10mm, use the automesh method to perform 2D structured mesh division on the engine block, bushing, gasket and fastening bolts, and use the solid map method to perform 3D structured mesh division on the engine block, bushing, gasket and fastening bolts. Select mesh surfaces on the cylinder head 3D mesh model and the 3D mesh models of the engine block, bushing, gasket and fastening bolts as the main surface and slave surface of the boundary conditions to be applied during the static strength analysis of the cylinder head. Set the material properties for the cylinder head 3D model and the 3D mesh models of each component related to the service status of the cylinder head and save them to obtain the mesh model of the cylinder head assembly as shown below. Figure 4 shown.

[0077] Step 2.3: Import the mesh model of the cylinder head assembly into Abaqus, set the explosion pressure of the fire surface to 25Mpa, the explosion pressure of the intake and exhaust valve seats to 48Mpa and 37Mpa respectively, and the preload of the four bolts to 115000N; select the contact pairs between the bolts and the cylinder head and the contact pairs between the cylinder head and the engine body to set the contact relationship and use the small slip and small deformation calculation method, with a friction coefficient of 0.15; select the connection pairs between the bolts and the engine body assembly holes to set the coupling relationship and use the small slip and small deformation calculation method, with a friction coefficient of 0.15; set the bottom of the engine body as a fixed support constraint. Select the simulation analysis type as static analysis, set the initial iteration step of the simulation to 0.01 and the maximum iteration step to 0.5 according to the computing power conditions, submit the simulation calculation and obtain the stress distribution and displacement distribution results of the cylinder head in the service state.

[0078] Step 2.4: Perform mesh independence analysis for static strength calculation of cylinder head. Starting from the initial value of 6mm mesh size, expand or reduce the mesh size used when drawing cylinder head 2D mesh model and cylinder head 3D mesh model, import cylinder head 3D model into cylinder head assembly mesh model, update assembly, calculate static strength simulation results of cylinder head under different mesh sizes, compare the influence of different mesh sizes on calculation time and stress and displacement calculation results, and select a mesh size with short calculation time and stress and displacement calculation results with deviation less than preset threshold value from calculation results under other mesh sizes as finite element mesh size used for optimization. After mesh independence analysis was performed in this embodiment, 5mm mesh size was finally selected as the optimal mesh size that takes into account both calculation speed and calculation accuracy, and 5mm mesh size was used for subsequent optimization. The stress distribution result of cylinder head calculated with 5mm mesh size is shown in Figure 5(a), and the displacement distribution result is shown in Figure 5(b).

[0079] Step 3: Adjust the structural parameters of the cylinder head model to generate a cylinder head model with parameters different from the initial values. Record the script for the cylinder head mesh drawing phase in Hypermesh and the script for the cylinder head component update phase in the cylinder head assembly model. Record the script for the cylinder head static strength calculation phase in Abaqus and extract the performance index data that can characterize the static strength of the cylinder head and the quality of the cylinder head.

[0080] The specific implementation method of step three includes the following steps:

[0081] Step 3.1: Adjust the structural parameters of the cylinder head model to generate a cylinder head model whose parameters are random numbers within a variation range.

[0082] Step 3.2: Start script recording in Hypermesh, edit the mesh quality criteria with a mesh size of 5mm as the standard, cancel the algorithm's detection of the maximum mesh size and the minimum mesh size, and improve the repair rate of low-quality meshes. Use the surface deviation meshing method to divide the 2D mesh, repair the meshes with unqualified mesh quality based on the QI optimization mesh repair algorithm and the size corrected mesh repair algorithm, and use the place node method to modify the meshes that are difficult to adjust with the mesh repair algorithm to a qualified mesh quality, and obtain a high-quality cylinder head 2D mesh model. Use the tetramesh meshing method to draw a 3D mesh to obtain a cylinder head 3D mesh model. Complete the drawing of the cylinder head mesh model and obtain the script for the cylinder head mesh drawing link.

[0083] Step 3.3: Start script recording in Hypermesh, import the cylinder head assembly mesh model, replace the cylinder head components in the cylinder head assembly mesh model with the cylinder head 3D mesh model with updated structural shape based on the mesh model replacement algorithm, export the new cylinder head assembly mesh model and obtain the script for the cylinder head mesh model update link.

[0084] Step 3.4: Record the script for the static strength calculation of the cylinder head. Start the script recording in Abaqus, import the mesh model of the cylinder head assembly, set the burst pressure of the fire surface to 25Mpa, the burst pressure of the intake and exhaust valve seats to 48Mpa and 37Mpa respectively, and the preload of the four bolts to 115000N; select the contact pair between the bolt and the cylinder head and the contact pair between the cylinder head and the engine body to set the contact relationship and use the small slip and small deformation calculation method, and the friction coefficient is 0.15; select the connection pair between the bolt and the engine body assembly hole to set the coupling relationship and use the small slip and small deformation calculation method, and the friction coefficient is 0.15; set the bottom of the engine body as a fixed support constraint. Select the simulation analysis type as static analysis, set the initial iteration step of the simulation to 0.01 and the maximum iteration step to 0.5 according to the computing power conditions, submit the simulation calculation and obtain the stress distribution and displacement distribution results of the cylinder head in the service state. Extract the mass of the cylinder head and the index data characterizing the static strength performance of the cylinder head and obtain the script for the static strength calculation of the cylinder head.

[0085] Step 4: Build a cylinder head static strength optimization model based on co-simulation technology, use the Latin hypercube algorithm to plan the sample space for cylinder head static strength optimization, call the script recorded during the cylinder head static strength calculation process through batch commands, and automatically run the cylinder head parameterized model update, cylinder head mesh drawing, cylinder head component update in the cylinder head assembly model, cylinder head static strength simulation analysis, and cylinder head static strength performance index data extraction during the cylinder head static strength optimization test design process to obtain a sample data set that characterizes the corresponding relationship between the cylinder head structure and static strength. Establish a comprehensive evaluation function, comprehensively consider multiple cylinder head static strength performance indicators to score the static strength performance of each sample point, select the best scoring group of samples as the optimization result, and obtain the optimal cylinder head structure in the sample space, that is, to achieve cylinder head static strength optimization based on co-simulation technology.

[0086] The specific implementation method of step 4 includes the following steps:

[0087] Step 4.1: Build a cylinder head static strength optimization model in Isight. The workflow is available Figure 6 The flowchart is represented by . Based on the i5-10500CPU and 16GB memory computing device used, the total number of samples in the sample space is set to 500, and the Latin hypercube algorithm is used to plan the sample space for the static strength optimization of the cylinder head, so that the sample points are evenly distributed in the high-dimensional Euclidean space to ensure the quality of the sample data. The commands for updating the cylinder head parametric model, drawing the cylinder head mesh, updating the cylinder head components in the cylinder head assembly model, simulating and analyzing the static strength of the cylinder head, and extracting the static strength performance index data of the cylinder head are called through batch commands. After the settings are completed, the cylinder head static strength optimization model is automatically run to obtain a sample data set that characterizes the corresponding relationship between the cylinder head structure and the static strength performance.

[0088] Step 4.2: Establish a comprehensive evaluation function, comprehensively consider the floating degree and importance of multiple cylinder head static strength performance indicators, and score the static strength performance of each sample point. In this embodiment, the cylinder head weight, maximum stress and maximum deformation are selected as evaluation indicators, and the ideal value of each indicator is set to the minimum value of the indicator data. The weight of each indicator is calculated and scored using the comprehensive evaluation function. The group of samples with the best scores are selected as the optimization results to complete the optimization of the cylinder head. The final optimized cylinder head model structure is as follows: Figure 7 shown.

[0089] The process also includes step 5, performing process adaptability design according to the optimal cylinder head structure obtained in step 4, and obtaining a cylinder head design scheme that meets production constraints. The cast iron cylinder head manufactured by this scheme is 11% lighter than the cylinder head before optimization, the maximum stress is reduced from 398.6MPa to 316.4MPa, and the maximum deformation is reduced from 0.0745mm to 0.0703mm. It can be seen that the optimized cylinder head has improved static strength and lightweight.

[0090] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A cylinder head static strength optimization method based on joint simulation technology, characterized in that: The cylinder head geometry model is constructed based on the parametric modeling method, and the cylinder head expression is used to control the structural shape of the cylinder head geometry model to achieve rapid update of the cylinder head geometry model; the cylinder head model is meshed by finite element method based on the automated meshing method, and the shape of the low-quality mesh is adjusted based on the mesh quality repair algorithm to ensure the mesh quality of the cylinder head mesh model; Based on the mesh model replacement algorithm, the cylinder head component in the cylinder head assembly mesh model is replaced with the cylinder head mesh model with an updated structural shape, and the selected boundary condition area on the cylinder head component is synchronized to the updated cylinder head mesh model; Set up simulation analysis based on the static strength analysis method of the cylinder head, use macro commands to drive the solver to perform automated static strength simulation analysis of the cylinder head, obtain the stress distribution and displacement distribution at each position on the cylinder head, and extract the mass of the cylinder head model; A sample space is constructed based on the parameter variation range of the cylinder head geometric model, and automated simulation analysis is repeated and performed independently on each sample point. After screening out data with non-convergence and substandard accuracy, a sample data set that characterizes the correspondence between the cylinder head structure and static strength performance is obtained. A comprehensive evaluation function is established to comprehensively weigh the stress, displacement and quality data corresponding to each sample point for scoring, and the group of samples with the best scores are selected as the structural optimization results of the cylinder head, thereby achieving optimization of the static strength performance of the cylinder head based on joint simulation technology.

2. The cylinder head static strength optimization method based on joint simulation technology according to claim 1, characterized in that: The following steps are included: Step 1: parametrically model the cylinder head to obtain a cylinder head parametric model; determine the initial value and boundary value of each parameter of the cylinder head parametric model, and gradually modify the cylinder head parametric model by combining global parameter changes with modification error reporting features until the cylinder head model meets the preset stability qualification requirements; By calling the API function of UG software, the cylinder head parametric model can be automatically updated with one click, thus improving the updating efficiency of the cylinder head parametric model; Step 2: Perform 2D meshing on the cylinder head parameterized model, repair meshes with unqualified mesh quality and then draw a 3D mesh model of the cylinder head; assemble the 3D mesh model of the cylinder head and various components related to the service status of the cylinder head, draw structured meshes for various components related to the service status of the cylinder head, and select mesh surfaces on the 3D mesh model of the cylinder head and the 3D mesh models of various components related to the service status of the cylinder head as the main surface and the secondary surface of the boundary conditions to be applied during the static strength analysis of the cylinder head; perform static strength analysis of the cylinder head assembly to obtain stress and displacement distribution at various positions on the cylinder head; perform mesh independence analysis of the static strength calculation of the cylinder head, and select a mesh size with a short calculation time and a deviation of the stress and displacement calculation results from the calculation results under other mesh sizes that is less than a preset threshold as the finite element mesh size used for optimization, wherein the short calculation time refers to a calculation time that is shorter than the preset threshold; Step 3: Adjust the structural parameters of the cylinder head model to generate a cylinder head model with parameters different from the initial values; record the script of the cylinder head mesh drawing link and the script of the cylinder head component update link in the cylinder head assembly model in Hypermesh; Record the script of the static strength calculation of the cylinder head in Abaqus and extract the performance index data that can characterize the static strength of the cylinder head and the quality of the cylinder head; Step 4: Build a cylinder head static strength optimization model based on joint simulation technology, use Latin hypercube algorithm to plan the sample space for cylinder head static strength optimization, call the script recorded during the cylinder head static strength calculation process through batch commands, and automatically run the cylinder head parameterized model update, cylinder head mesh drawing, cylinder head component update in the cylinder head assembly model, cylinder head static strength simulation analysis and cylinder head static strength performance index data extraction in the cylinder head static strength optimization test design process to obtain a sample data set that characterizes the correspondence between the cylinder head structure and static strength; establish a comprehensive evaluation function, comprehensively weigh multiple cylinder head static strength performance index data to score each sample point, select the best scoring group of samples as the optimization result, and obtain the optimal cylinder head structure in the sample space, that is, to achieve cylinder head static strength optimization based on joint simulation technology.

3. The cylinder head static strength optimization method based on joint simulation technology as claimed in claim 2, characterized in that: The method further includes step five, performing process adaptability design according to the optimal cylinder head structure obtained in step four, and obtaining a cylinder head design scheme that meets production constraints; the cylinder head manufactured by the cylinder head design scheme can improve static strength performance, reduce maximum stress of the cylinder head, reduce deformation effect, improve material distribution and significantly achieve lightweight compared to the cylinder head before optimization.

4. The cylinder head static strength optimization method based on joint simulation technology as claimed in claim 3, characterized in that: The specific implementation method of step one is: S11: Select UG as the modeling platform to complete the parametric modeling of the cylinder head; use the stretching or rotation modeling method to establish the external features of the cylinder head, the features include the top plate, the bottom plate, and the side wall; use the projection curve modeling method to draw the characteristic lines on the wall surfaces of the intake and exhaust ducts of the cylinder head, use the fitting surface modeling method to connect the closed projection curves to generate the surface features of the intake and exhaust duct walls, sew the surface features that constitute the intake and exhaust ducts to form a solid, and use the Boolean operation method to subtract the external features of the cylinder head from the intake and exhaust duct entities to obtain a cylinder head model that completes the airway modeling; use the stretching, rotation, punching or rounding modeling method to draw the characteristic lines on the cylinder head that completes the airway modeling The assembly features of the cylinder head are established on the head model, and the features include fastening threaded holes, intake and exhaust pipe assembly holes, water inlet and outlet assembly holes, fuel injector assembly holes, and positioning pin holes; the water inlet and outlet of the flow channel are drawn on the cylinder head after the assembly feature modeling is completed by using the stretching modeling method, and the flow channel geometry of the cylinder head is drawn by stretching, rotating, and stitching surfaces at the position where the wall thickness on the cylinder head model is greater than the minimum wall thickness requirement of the process, starting from the water inlet, until the flow channel geometry connects the water inlet and the water outlet, and the flow channel geometry is arranged at the position where the wall thickness is greater than the minimum wall thickness requirement of the process, and the flow channel geometry needs to strictly meet the minimum wall thickness requirement of the processing technology when setting the size; All the flow channel geometries are summed up by Boolean operation to obtain the flow channel entity of the cylinder head model, and then the cylinder head model with completed air channel modeling and the flow channel entity of the cylinder head model are subtracted by Boolean operation to obtain the cylinder head model with completed air channel and flow channel modeling; after the external features, air channels, assembly features and flow channels of the cylinder head are modeled, weight-reducing geometries are established at the top plate, bottom plate and side wall of the cylinder head at positions not involving assembly and sealing by stretching, rotating and stitching surfaces, and the size of the weight-reducing geometries is associated with the size of the flow channel geometries to always ensure that the minimum wall thickness on the cylinder head is greater than the minimum wall thickness requirement of the process; Boolean operation is used to subtract the cylinder head with completed assembly feature modeling from all weight-reducing geometries to obtain the cylinder head model with completed parametric modeling; S12: setting parameter initial values ​​and parameter boundary values ​​for structural parameters on the cylinder head parametric model; setting one parameter boundary value of the cylinder head parametric model to a limit parameter when the wall thickness at each position of the cylinder head is the minimum wall thickness requirement of the process, and setting the other parameter boundary value to other limit dimensions that meet the cylinder head design requirements, wherein the cylinder head design requirements include that the hydraulic diameter at each position of the flow channel shall not be less than the limit dimension that causes flow obstruction, the narrowest part of the cylinder head surface shall not be less than one-third of the minimum wall thickness requirement of the process, and no interference shall occur between the cylinder head flow channel, air channel, assembly features, weight reduction features and external wall surface; Some cylinder head dimensions are the reference dimensions set when the cylinder head parametric model is built. The initial values ​​of the reference dimension parameters are set to the initial values ​​used when the cylinder head parametric model is built. The reference dimensions do not change when the cylinder head parametric model is updated. After the upper and lower boundary values ​​of the parameter changes are determined for the parameters other than the reference dimensions, the initial values ​​of the parameters other than the reference dimensions are set to the median of the upper and lower boundary values ​​to reduce the probability of errors when the cylinder head parametric model is updated. S13: gradually modify the cylinder head parametric model by "combining global parameter changes with error feature modification"; when the cylinder head parametric model selects parameter values ​​within the parameter variation range obtained in S12 and substitutes them into the expression to update the model, and when the model is updated for more than a preset number of times and still no error occurs, it is determined that the stability of the cylinder head parametric model meets the conditions required for optimization; the function of this step S13 is to repeatedly test whether the cylinder head parametric model reports an error under different parameter values, and to modify the error feature, and gradually improve the cylinder head parametric model; name all parameters other than the reference size in the cylinder head parametric model expression, configure the data interface between Excel and UG, and import the parameter names of the cylinder head other than the reference size and their corresponding parameter variation ranges into an Excel table, use a random number formula to randomly select a parameter value for all parameters other than the reference size within the variation range, and then select all newly generated random parameter values ​​together with the names of all parameters other than the reference size as the data source of the cylinder head parametric model, and use the Excel table to drive UG to update the model multiple times to test the parameter stability of the cylinder head parametric model under random parameter values; When the cylinder head parametric model does not report an error when the random parameter value is used continuously for the preset number of model updates, the parameter stability of the cylinder head parametric model is determined to be qualified; if an error occurs, the error feature prompted in the UG software is modified or the size variation range corresponding to the feature is modified until the cylinder head parametric model is updated continuously for the preset number of times using the random parameter value without reporting an error; S14: Automatically update the cylinder head model by calling the UG API function; Call UG's API function to read the cylinder head parametric model path, read the cylinder head parametric model expression path, automatically update the cylinder head parametric model using the expression parameter value, and save the new parameter value corresponding to the cylinder head parametric model, thereby realizing one-click automatic update of the cylinder head parametric model.

5. The cylinder head static strength optimization method based on joint simulation technology as claimed in claim 4, characterized in that: The specific implementation method of step 2 is: S21: Mesh the cylinder head parametric model separately; draw the mesh using the minimum wall thickness requirement of the process as the initial mesh size, import the cylinder head parametric model into Hypermesh, set the mesh size to the minimum wall thickness requirement of the process, and use the surface deviation meshing method to divide it into 2D meshes; repair the meshes with unqualified mesh quality based on the QIoptimization mesh repair algorithm and the size corrected mesh repair algorithm, and use the place node method to modify the meshes that are difficult to adjust by the mesh repair algorithm to a qualified mesh quality, so as to obtain a high-quality cylinder head 2D mesh model; Set the mesh size to the minimum wall thickness required by the process, use the tetramesh meshing method to draw the 3D mesh, and obtain the cylinder head 3D mesh model; S22: Establish a mesh model of the cylinder head assembly; import the cylinder head 3D mesh model into Hypermesh, import various components related to the service status of the cylinder head, and assemble the various components related to the service status of the cylinder head with the cylinder head 3D mesh model according to the engine assembly requirements, wherein the components include an engine body, a bushing, a gasket, and a fastening bolt; perform 2D structured mesh division on the various components related to the service status of the cylinder head using the automesh method, and use solid map method to perform 3D structured mesh division on the components related to the service status of the cylinder head, and obtain the 3D mesh models of the components related to the service status of the cylinder head; based on the cylinder head static strength analysis method, mesh surfaces are respectively selected on the cylinder head 3D mesh model and the 3D mesh models of the components related to the service status of the cylinder head as the master surface and slave surface of the boundary conditions to be applied during the static strength analysis of the cylinder head, and the master surface and slave surface include the master and slave surface of the contact relationship between the bolt and the cylinder head, the master and slave surface of the connection relationship between the bolt and the assembly hole of the body, the master and slave surface of the contact relationship between the cylinder head and the body, and the action surface of the explosion pressure of the combustion chamber; the material properties are set and saved for the 3D mesh model of the cylinder head and the 3D mesh models of the components related to the service status of the cylinder head, and the mesh model of the cylinder head assembly is obtained; S23: Set up simulation based on the static strength analysis method of the cylinder head, perform static strength analysis of the cylinder head assembly, and obtain the stress and displacement distribution at each position on the cylinder head; import the mesh model of the cylinder head assembly into Abaqus, set the explosion pressure and bolt preload force that the cylinder head is subjected to during operation, select the contact pair between the bolt and the cylinder head and the contact pair between the cylinder head and the engine body to set the contact relationship and use the small slip and small deformation calculation method, select the connection pair between the bolt and the engine body assembly hole to set the coupling relationship and use the small slip and small deformation calculation method, and set the bottom of the engine body as a fixed support constraint; select the simulation analysis type as static analysis, set the initial iteration step and maximum iteration step of the simulation according to the computing power conditions, submit the simulation calculation and obtain the stress distribution and displacement distribution results of the cylinder head in the service state; S24: Performing a mesh independence analysis for static strength calculation of the cylinder head; starting from the mesh size initial value of the minimum wall thickness requirement of the process, expanding or reducing the mesh size used when drawing the cylinder head 2D mesh model and the cylinder head 3D mesh model, importing the cylinder head 3D model into the cylinder head assembly mesh model, updating the assembly, and calculating the static strength simulation results of the cylinder head under different mesh sizes, comparing the effects of different mesh sizes on the calculation time and the stress and displacement calculation results, selecting a mesh size with a short calculation time and a stress and displacement calculation result with a deviation less than a preset threshold value from the calculation result under other mesh sizes as the finite element mesh size used for optimization, and completing the mesh independence analysis, wherein the short calculation time refers to a calculation time that is shorter than the preset threshold value.

6. The cylinder head static strength optimization method based on joint simulation technology as claimed in claim 5, characterized in that: The specific implementation method of step three is: S31: adjusting the structural parameters of the cylinder head model, automatically updating the cylinder head model and the cylinder head cooling channel model, and generating a cylinder head model with parameters different from the initial values; modifying all parameters except the reference size in the expression of the cylinder head parameterized model, calling the UG API function, reading the cylinder head parameterized model expression, and automatically updating the cylinder head model and the cylinder head cooling channel model with one key; S32: Script for recording the cylinder head mesh drawing process; Based on the mesh size determined after mesh independence analysis, start script recording in Hypermesh, edit the mesh quality evaluation criteria, cancel the algorithm's detection of the maximum and minimum mesh sizes, and improve the repair rate of low-quality meshes; Use the surface deviation meshing method to divide it into 2D meshes, use the QI optimization mesh repair algorithm and the size corrected mesh repair algorithm to repair meshes with unqualified mesh quality, and use the place node method to modify the meshes that are difficult to adjust with the mesh repair algorithm to qualified mesh quality, so as to obtain a high-quality cylinder head 2D mesh model; use the tetramesh meshing method to draw the 3D mesh to obtain the cylinder head 3D mesh model; complete the drawing of the cylinder head mesh model and obtain the script for the cylinder head mesh drawing link; S33: recording the script for updating the cylinder head components in the cylinder head assembly model; starting the script recording in Hypermesh, importing the cylinder head assembly mesh model, replacing the cylinder head components in the cylinder head assembly mesh model with the cylinder head 3D mesh model with updated structural shape based on the mesh model replacement algorithm, exporting the new cylinder head assembly mesh model and obtaining the script for updating the cylinder head mesh model; S34: Script for recording the static strength calculation of cylinder head; Start script recording in Abaqus, import the cylinder head assembly mesh model, set the explosion pressure and bolt preload that the cylinder head is subjected to during operation, select the contact pairs between the bolts and the cylinder head and the contact pairs between the cylinder head and the engine body to set the contact relationship and use the small slip and small deformation calculation method, select the connection pairs between the bolts and the engine body assembly holes to set the coupling relationship and use the small slip and small deformation calculation method, and set the bottom of the engine body as a fixed constraint; select the simulation analysis type as static analysis, set the initial iteration step and the maximum iteration step of the simulation according to the computing power conditions, submit the simulation calculation and obtain the stress distribution and displacement distribution results of the cylinder head in the service state; extract the mass of the cylinder head and the index data characterizing the static strength performance of the cylinder head and obtain the script for the static strength calculation link of the cylinder head, and the performance index data that can characterize the static strength of the cylinder head include the maximum Mises stress, the maximum displacement, the maximum partial displacement in the three positive directions, and the stress gradient.

7. The cylinder head static strength optimization method based on joint simulation technology as claimed in claim 6, characterized in that: The specific implementation method of step 4 is: S41: Build a cylinder head static strength optimization model in Isight, set the total number of samples according to the computing power conditions, and use the Latin hypercube algorithm to plan the sample space for cylinder head static strength optimization, so that the sample points are evenly distributed in the high-dimensional Euclidean space to ensure the quality of sample data; call the commands for updating the cylinder head parametric model, drawing the cylinder head mesh, updating the cylinder head parts in the cylinder head assembly model, simulating and analyzing the static strength of the cylinder head, and extracting the static strength performance index data of the cylinder head through batch processing commands; After the setup is completed, the cylinder head static strength optimization model is automatically run to obtain a sample data set that characterizes the corresponding relationship between the cylinder head structure and static strength performance; S42: Establish a comprehensive evaluation function, comprehensively consider the floating degree and importance of multiple cylinder head static strength performance indicators, and score the static strength of each sample point. As a preferred embodiment, the comprehensive evaluation function is shown in the following formula: Among them, g j is the comprehensive score of the jth evaluated sample point, λ i is the weight of the i-th evaluated indicator, y ij is the actual value of the i-th evaluated indicator of the j-th evaluated sample point, Z i is the ideal value of the i-th evaluated indicator of the evaluated sample point, σ i is the standard deviation of the u-th evaluated indicator data, and n is the total number of indicators evaluated at the sample point. The weight of the i-th evaluated indicator can be calculated using the following formula: C i is the significance coefficient of the ith indicator, C i The larger the value is, the greater the impact of the i-th indicator on the comprehensive evaluation results, and the higher the weight is. i The standard deviation σ i and the correlation coefficient R i The product of is: C i =s i R i (3) Standard deviation i Calculated using the following formula: In the formula, m is the total number of sample points used to calculate the standard deviation, x ij is the dimensionless data of the i-th performance index of the j-th sample point, is the dimensionless data average of the i-th performance indicator. The dimensionless data of the i-th performance indicator at the j-th sample point can be dimensionlessized by the following formula to obtain the data average: Correlation coefficient R i Calculated using the following formula: r ik is the linear correlation coefficient between the i-th indicator and the k-th indicator, which can be calculated using the following formula: After calculating all the above variables according to the sample data set, each sample point is scored through the comprehensive evaluation function, and the group of samples with the best scores are selected as the optimization results to obtain the optimal cylinder head structure in the sample space, that is, to achieve the optimization of the static strength performance of the cylinder head based on the joint simulation technology.

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