Casting machining deformation prediction method and system

Abstract

The invention provides a casting machining deformation prediction method which comprises a casting simulation step, a node coordinate conversion step and a simulation machining step, in the casting simulation step, after a casting model is subjected to tetrahedral mesh division, casting simulation is conducted in a low-pressure casting mode, and the casting deformation is obtained. A casting residual stress simulation result is obtained; a node coordinate conversion step: performing curve fitting on the casting residual stress simulation result to obtain a stress curve formed by fitting each node coordinate on the tetrahedral mesh; calculating by substituting a stress curve to obtain the stress of each node coordinate on the hexahedral mesh; a simulation processing step: loading the stress of each node coordinate on the hexahedral mesh to the mesh nodes of the casting model, and then simulating a part material removal process to obtain a deformation result after the casting model is processed; according to the method, the casting residual stress simulation result is subjected to curve fitting, so that the problem that node stress data cannot be directly transmitted by different software is solved.

Description

Technical Field

[0001] The present application belongs to the field of casting processing technology, and in particular relates to a casting processing deformation prediction method and system. Background Art

[0002] Casting refers to a processing method in which solid metal is melted into liquid and poured into a mold of a specific shape, and then waited for it to solidify into shape.

[0003] Cast aluminum alloy thin-walled parts are prone to deformation after machining due to high internal residual stress, thin wall thickness, low overall rigidity, and high material removal rates during machining. Furthermore, the distribution of casting residual stress is even more complex, making it difficult to measure experimentally.

[0004] Existing technology allows for conveniently obtaining casting residual stresses using casting simulation software and applying these to machining simulation software. However, due to the varying meshing methods used in different software, the resulting casting residual stress results vary widely, resulting in completely different mesh node locations, numbers, and connection methods. This makes it impossible to directly transfer nodal stress data and apply them directly to machining simulation software. Summary of the Invention

[0005] In response to the shortcomings in the relevant technologies, the present application provides a casting processing deformation prediction method and system, which performs curve fitting on the casting residual stress simulation results through the node coordinate conversion step, thereby converting the stress of each node coordinate on the tetrahedral grid into the stress of each node coordinate on the hexahedral grid through the stress curve, thereby solving the problem that different software cannot directly transmit node stress data, so that the node stress data of other software can be applied to the processing simulation software, and the entire process of parts from casting to machining is simulated, which reduces the cost of part research and development and improves production efficiency.

[0006] In one aspect, the present application provides a method for predicting casting machining deformation, comprising: a casting simulation step, establishing a casting model using 3D modeling software; dividing the casting model into a tetrahedral mesh, and then performing a casting simulation using a low-pressure casting mode to obtain a casting residual stress simulation result, wherein the casting residual stress simulation result includes the stress of each node coordinate on the tetrahedral mesh; a node coordinate conversion step, performing curve fitting on the casting residual stress simulation result to obtain a stress curve formed by fitting the coordinates of each node on the tetrahedral mesh; after dividing the casting model into a hexahedral mesh, the stress curve is substituted into the stress curve for calculation to obtain the stress of each node coordinate on the hexahedral mesh; The stress of each node coordinate on the hexahedral mesh is loaded to the grid node of the casting model by simulating the processing step, and then the deformation result of the casting model after processing is obtained by simulating the material removal process of the part.

[0007] In some embodiments, the casting simulation step further comprises: The modeling step comprises establishing the casting model by a three-dimensional modeling software, wherein the casting model comprises a casting part model, a chill model and a riser model. The first mesh division step comprises importing the casting model into a Mesh module of a Procast software, and establishing a sand box model in the Mesh module to perform tetrahedral mesh division. The parameter setting step comprises setting casting process simulation parameters and result output configuration in a Cast module of the Procast software, and performing casting simulation on the casting model in a low-pressure casting mode to obtain the casting residual stress simulation result.

[0008] In some embodiments, the node coordinate conversion step further comprises: The fitting preparation step comprises drawing a stress scatter plot of each node coordinate on the tetrahedral mesh according to the casting residual stress simulation result in a numerical analysis software. The fitting selection step comprises selecting a curve fitting method based on the contour shape of the stress scatter plot to obtain a stress curve fitted by each node coordinate on the tetrahedral mesh, wherein the curve fitting method comprises a least square method, a kernel method and a spline method.

[0009] In some embodiments, the node coordinate conversion step further comprises: The second mesh division step comprises importing the casting model into an ABAQUS software to perform hexahedral mesh division. The transformation calculation step comprises calculating the stress of each node coordinate on the hexahedral mesh according to the stress curve.

[0010] In some embodiments, the simulation processing step further comprises: The stress loading step comprises importing the stress of each node coordinate on the hexahedral mesh into a Load module of the ABAQUS software, and loading the stress of each node coordinate on the hexahedral mesh to the grid node of the casting model by the Load module. The processing simulation step comprises simulating the material removal process of the part by the ABAQUS software to obtain the deformation result of the casting model after processing.

[0011] In another aspect, the application also provides a casting processing deformation prediction system, comprising: The casting simulation module establishes a casting model through a three-dimensional modeling software; after the casting model is divided into tetrahedral meshes, casting simulation is performed through a low-pressure casting mode to obtain a casting residual stress simulation result, the casting residual stress simulation result including stresses of node coordinates on the tetrahedral meshes; The node coordinate conversion module performs curve fitting on the casting residual stress simulation result to obtain a stress curve formed by fitting the node coordinates on the tetrahedral meshes; after the casting model is divided into hexahedral meshes, calculation is performed through the stress curve to obtain stresses of node coordinates on the hexahedral meshes. The simulation machining module loads the stresses of node coordinates on the hexahedral meshes to grid nodes of the casting model, and then obtains a deformation result of the casting model after machining by simulating a material removal process of a part.

[0012] In some embodiments, the casting simulation module further includes: The modeling unit is configured to establish the casting model through a three-dimensional modeling software, the casting model including a casting part model, a chill model and a riser model. The first mesh division unit is configured to import the casting model into a Mesh module of a Procast software, and establish a sand box model in the Mesh module to divide the casting model into tetrahedral meshes. The parameter setting unit is configured to set casting process simulation parameters and result output configurations in a Cast module of the Procast software, and perform casting simulation on the casting model in a low-pressure casting mode to obtain the casting residual stress simulation result.

[0013] In some embodiments, the node coordinate conversion module further includes: The fitting preparation unit is configured to draw a stress scatter plot of node coordinates on the tetrahedral meshes in a numerical analysis software according to the casting residual stress simulation result. The fitting selection unit is configured to select a curve fitting method based on a contour shape of the stress scatter plot to obtain a stress curve formed by fitting the node coordinates on the tetrahedral meshes, the curve fitting method including a least square method, a kernel method and a spline method.

[0014] In some embodiments, the node coordinate conversion module further includes: The second mesh division unit is configured to import the casting model into an ABAQUS software to divide the casting model into hexahedral meshes. The transformation calculation unit is configured to calculate stresses of node coordinates on the hexahedral meshes according to the stress curve.

[0015] In some embodiments, the simulation machining module further includes: a stress loading unit, configured to introduce the stress of each node coordinate on the hexahedral mesh into a Load module of the ABAQUS software, and load the stress of each node coordinate on the hexahedral mesh to the grid node of the casting model through the Load module; a machining simulation unit, configured to simulate a part material removal process through the ABAQUS software, and obtain a deformation result of the casting model after machining.

[0016] In summary, the casting machining deformation prediction method and system provided in the application can solve the problem that different software cannot directly transfer node stress data by curve fitting the casting residual stress simulation result through the node coordinate conversion step, so that the node stress data of other software can be applied to machining simulation software, the whole process simulation from casting to machining of a part is realized, the part research and development cost is reduced, and the production efficiency is improved; the casting process is simulated through the casting simulation step, the casting residual stress simulation result is conveniently obtained, and the subsequent machining simulation is laid a foundation; the machining process is simulated through the simulated machining step, the deformation result of the casting model at each machining stage is conveniently obtained, and the casting process can be optimized according to the deformation condition.

[0017] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art upon examination of the following or can be learned by practice of the present application. The objects and other advantages of the present application can be realized and attained by the structure particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the present application and serve to explain the present application. In the drawings: Figure 1 a total flowchart of the casting machining deformation prediction method of the present application; Figure 2 a casting simulation step flowchart of the casting machining deformation prediction method of the present application; Figure 3 a node coordinate conversion step flowchart of the casting machining deformation prediction method of the present application; Figure 4 a simulated machining step flowchart of the casting machining deformation prediction method of the present application; Figure 5 an implementation flowchart of the casting machining deformation prediction method of the present application; Figure 6A cylindrical tetrahedral meshing diagram for a cast piece machining deformation prediction method of the present application; Figure 7 A casting residual stress simulation result diagram for a cast piece machining deformation prediction method of the present application; Figure 8 A stress scatter plot of node coordinates on a tetrahedral mesh for a cast piece machining deformation prediction method of the present application; Figure 9 A 0-3cm fitting result diagram for a cast piece machining deformation prediction method of the present application; Figure 10 A 33-36cm fitting result diagram for a cast piece machining deformation prediction method of the present application; Figure 11 A cylindrical hexahedral meshing diagram for a cast piece machining deformation prediction method of the present application; Figure 12 A machining deformation prediction result diagram for a cast piece machining deformation prediction method of the present application. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0020] In the description of the present application, it should be understood that the terms "center", "transverse", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0021] The terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second", "third" can explicitly or implicitly include one or more of the features.

[0022] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integrally connected; can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. Embodiment one Reference is made to the accompanying drawings Figures 1 to 12 , Figure 1 The total flow chart of the casting processing deformation prediction method of the present application; Figure 2 The casting simulation step flow chart of the casting processing deformation prediction method of the present application; Figure 3 The node coordinate conversion step flow chart of the casting processing deformation prediction method of the present application; Figure 4 The simulated processing step flow chart of the casting processing deformation prediction method of the present application; Figure 5 The implementation flow chart of the casting processing deformation prediction method of the present application; Figure 6 The cylindrical tetrahedral mesh division diagram of the casting processing deformation prediction method of the present application; Figure 7 The casting residual stress simulation result schematic diagram of the casting processing deformation prediction method of the present application; Figure 8 The stress scatter diagram of each node coordinate on the tetrahedral mesh of the casting processing deformation prediction method of the present application; Figure 9 The 0-3cm fitting result schematic diagram of the casting processing deformation prediction method of the present application; Figure 10 The 33-36cm fitting result schematic diagram of the casting processing deformation prediction method of the present application; Figure 11 The cylindrical hexahedral mesh division diagram of the casting processing deformation prediction method of the present application; Figure 12 The processing deformation prediction result schematic diagram of the casting processing deformation prediction method of the present application; the specific embodiments will be described below in combination with the above drawings.

[0024] Reference is made to the accompanying drawings Figure 1 The present application provides a casting processing deformation prediction method, which comprises a casting simulation step S1, a node coordinate conversion step S2 and a simulated processing step S3.

[0025] The casting simulation step S1, a three-dimensional modeling software is used to establish a casting model; after the casting model is divided into a tetrahedral mesh, a low-pressure casting mode is used to simulate the casting, and a casting residual stress simulation result is obtained, which includes the stress of each node coordinate on the tetrahedral mesh; The node coordinate conversion step S2, the casting residual stress simulation result is carried out curve fitting, and the stress curve formed by fitting each node coordinate on the tetrahedral grid is obtained; after the casting model is divided into hexahedral grid, the stress curve is substituted for calculation, and the stress of each node coordinate on the hexahedral grid is obtained; The simulation processing step S3, the stress of each node coordinate on the hexahedral grid is loaded to the grid node of the casting model, and then the material removal process of the casting model is simulated to obtain the deformation result after the casting model is processed.

[0026] Reference to the accompanying drawings Figure 2 In some embodiments, the casting simulation step S1 further comprises the following steps: The modeling step S11, the casting model is established by a three-dimensional modeling software, and the casting model comprises a casting part model, a chill model and a riser model.

[0027] Specifically, the three-dimensional modeling software is used to establish the geometric model required in the casting process, and the three-dimensional modeling software includes but is not limited to UG, CATIA and SolidWorks, and the casting model includes a casting part model, a chill model and a riser model.

[0028] The casting part model is the final geometric shape of the casting to be produced.

[0029] The chill model is a metal insert block for accelerating local cooling, which is used to control the solidification rate, define the heat conduction boundary of the local rapid cooling area, so that the local cooling effect is accurately simulated, and the residual stress prediction distortion is avoided.

[0030] The riser model provides a cavity for molten metal feeding, which is used to prevent shrinkage defects, define the flow and solidification boundary of the feeding metal source, ensure that the feeding process is dynamically simulated, and reduce the stress concentration error caused by shrinkage.

[0031] The modeling step S11 converts the actual casting into a digital model, and saves it as an.igs format file for backup, and the generated geometric model is the input basis for all subsequent simulations.

[0032] The first mesh division step S12, the casting model is imported into the Mesh module of the Procast software, and a sand box model is established in the Mesh module to divide the tetrahedral grid.

[0033] Specifically, the casting model is imported into the Mesh module of the Procast software, and the sand box model is created in the Mesh module, which is used to simulate the real environment of the casting in the sand mold, and avoid the interference of boundary effect.

[0034] Then, a surface mesh is divided on the casting model, a volume mesh is divided according to the surface mesh, and the volume mesh is a tetrahedral mesh, so that the mesh nodes are shared at the contact surface of the chill model and the connecting position of the riser model.

[0035] The first mesh division step S12 is used to convert the continuous geometric model into a calculable discrete unit, and provides a carrier for the casting process simulation, in which the interaction boundary between the casting and the sand is automatically processed by the sand box model, and the error caused by manually defining the contact pair is avoided; the tetrahedral mesh can flexibly fit the complex topologies such as the embedded chill curved surface and the riser taper transition, and a mesh file including node coordinates and unit mapping relationship is generated.

[0036] The parameter setting step S13 sets the casting process simulation parameters and the result output configuration in the Cast module of the Procast software, and performs the casting simulation on the casting model in the low pressure casting mode to obtain the casting residual stress simulation result.

[0037] Specifically, the low pressure diecasting mode is selected in the Cast module of the Procast software, and the casting process simulation parameters are set to perform the casting simulation, and the casting process simulation parameters include material properties, pouring port liquid pressure, boundary conditions, filling control, solidification calculation and stress calculation.

[0038] Finally, the casting residual stress simulation result is obtained, and the casting residual stress simulation result includes the stress of each node coordinate on the tetrahedral mesh, the node coordinates on the tetrahedral mesh, the node stress tensor and the equivalent residual stress.

[0039] The result output configuration is that the output type is set to Profile by selecting the data extraction mode, the stress field sampling area is specified by defining the coordinate range, and the output is set to.xyn file by setting the output data storage format.

[0040] It should be noted that the coordinate space range and the storage format of the output data should be adjusted according to the actual needs of those skilled in the art, the coordinate space range includes the X-axis coordinate, the Y-axis coordinate and the Z-axis coordinate, and the storage format includes.xyn; the above-mentioned variants of the result output configuration all belong to the protection scope of the claims.

[0041] Reference is made to the accompanying drawings Figure 3 In some embodiments, the node coordinate conversion step S2 further includes the following steps: The fitting preparation step S21 draws a stress scatter plot of each node coordinate on the tetrahedral mesh according to the casting residual stress simulation result in the numerical analysis software.

[0042] Specifically, the casting residual stress simulation results output from Procast include the coordinates and stress tensors of each node on the tetrahedral mesh, but the total data volume of the coordinates and stress tensors of each node on the tetrahedral mesh is huge and the spatial distribution is disordered.

[0043] Moreover, the mesh partitioning of Procast software is different from that of ABAQUS software. In ABAQUS, the part is meshed into regular hexahedral structures, which is different from the tetrahedral mesh partitioning of the part in Procast. The casting residual stress simulation results of Procast cannot be directly loaded onto the mesh nodes of ABAQUS.

[0044] By inputting the casting residual stress simulation results into a numerical analysis software, a stress scatter plot of the coordinates of each node on the tetrahedral mesh is drawn for analysis, wherein the numerical analysis software includes Matlab, Origin and Mathmatic.

[0045] The stress distribution pattern, including the circumferential periodicity and the radial decay trend, can be identified through the stress scatter plot, and abnormal outliers can be identified through the stress scatter plot, so as to eliminate them before fitting to improve the fault tolerance of the casting model.

[0046] In the fitting selection step S22, a curve fitting method is selected based on the contour shape of the stress scatter plot, to obtain a stress curve fitted by the coordinates of each node on the tetrahedral mesh. The curve fitting method includes the least square method, the kernel method and the spline method.

[0047] Specifically, the curve fitting method is selected based on the contour shape of the stress scatter plot, and the curve fitting method includes the least square method, the kernel method and the spline method.

[0048] When the linear trend is obvious, the least square method is selected to retain the long-range stress trend; when the local fluctuation is obvious, the spline method is selected to capture the stress peak value in the geometric mutation area; and when the noise interference is serious, the kernel method is selected to filter the false oscillation at the sand box boundary.

[0049] The above-mentioned curve fitting method can fit the coordinates of each node on the tetrahedral mesh into a continuous stress curve, which is actually a continuous function expression or a discrete function point set, and can describe the residual stress distribution trend at any spatial position. The continuous stress curve serves as an interpolation basis for the stress of the hexahedral mesh node, so as to convert the disordered tetrahedral node stress into a physically faithful continuous curve, break through the transfer obstacle caused by the difference in mesh types, and make the stress calculation more accurate and the simulation results more accurate.

[0050] In the second mesh partitioning step S23, the casting model is imported into the ABAQUS software for hexahedral mesh partitioning.

[0051] Specifically, the tetrahedral mesh divided based on the casting model in the first mesh dividing step S12 has the advantage of fast stress calculation, but low precision, and is suitable for complex casting process; if the tetrahedral mesh is directly used for machining simulation, it will lead to non-convergence of material removal algorithm, thus distorting the deformation prediction.

[0052] The hexahedral mesh divided based on the casting model in the second mesh dividing step S23 has the advantage of fast material removal calculation, and higher precision, and is suitable for tool path simulation.

[0053] The regular topology of the hexahedral mesh is used to make the gradient direction of the stress curve parallel to the mesh edge, and the hexahedral mesh also provides a layered discrete basis, so that the Element Birth / Death technology of ABAQUS can accurately simulate the milling process.

[0054] In the conversion calculation step S24, the stress of each node coordinate on the hexahedral mesh is calculated according to the stress curve.

[0055] Specifically, for each node coordinate on the hexahedral mesh, the stress curve generated in the fitting selection step S22 is used for interpolation calculation.

[0056] The interpolation method includes one-dimensional interpolation along three spatial directions respectively, or a multivariate interpolation method, which includes three-dimensional spline interpolation and Kriging method, so as to map the stress corresponding to each node coordinate on the tetrahedral mesh to the position of each node coordinate on the hexahedral mesh, and output the stress data of each node coordinate on the hexahedral mesh.

[0057] Reference is made to the accompanying drawings Figure 4 In some embodiments, the simulation machining step S3 further comprises the following steps: In the stress loading step S31, the stress of each node coordinate on the hexahedral mesh is introduced into the Load module of the ABAQUS software, and the stress of each node coordinate on the hexahedral mesh is loaded onto the grid nodes of the casting model through the Load module.

[0058] Specifically, using the Load module of the ABAQUS software or through the script interface, the stress data of each node coordinate on the hexahedral mesh output by the node coordinate conversion step S24 is loaded and introduced into the hexahedral mesh nodes of the divided casting model output by the second mesh dividing step S23, and a hexahedral mesh casting model to which stress is applied is output.

[0059] The stress loading step S31 is used to accurately apply the casting residual internal pressure field calculated and converted in the foregoing steps to the finite element model used for machining simulation, so that the theoretical data becomes the input boundary condition and material state in the actual finite element solution.

[0060] The machining simulation step S32 simulates the part material removal process by ABAQUS software to obtain the deformation result of the machined casting model.

[0061] Specifically, the hexahedral mesh casting model subjected to stress output by the stress loading step S31 is imported into the Step module of the ABAQUS software, and the machining process is simulated based on the Element Birth / Death technology in the Step module.

[0062] Among them, Element Death is to set some elements in the finite element model to the "deactivated" state, lose the bearing capacity and do not participate in the calculation, which is equivalent to the material being removed.

[0063] Element Birth is to reactivate the previously deactivated elements to restore their bearing capacity and calculation participation.

[0064] In the machining simulation, "element death" is generally used to represent the material cutting or milling process, that is, the elements corresponding to the region are removed from the model, thereby simulating the process of gradually removing the material.

[0065] Based on the Element Birth / Death technology in the Step module to simulate the machining process, multiple analysis steps are established in ABAQUS, and each step corresponds to a machining stage or a cutting region.

[0066] The first step is usually the initial state, which is used to maintain the residual stress loading balance; each subsequent step is used to perform element death processing.

[0067] The hexahedral mesh casting model subjected to stress is imported into the Step module of the ABAQUS software and is in the initial state of the first step.

[0068] When the Element Death operation is applied once in each subsequent step, the element death processing of the preset cutting region is performed, the elements in the preset cutting region are set to "Death", and the stiffness matrix of these elements is set to zero, which is equivalent to removing the part of the material from the hexahedral mesh casting model.

[0069] After each Element Death operation is applied, the ABAQUS solver recalculates the stress deformation response of the hexahedral mesh casting model to obtain the deformation caused by the release of residual stress and the change in stiffness.

[0070] According to the deformation caused by the release of residual stress and the change in stiffness, it can be judged whether the casting deformation meets the accuracy, if so, the casting parameters are applicable.

[0071] Otherwise, the foundryman will optimize the setting of the casting parameters, such as setting the chill in the stress concentration area to reduce the casting stress, setting the stiffener in the area of weak rigidity to increase the rigidity of the casting to achieve the purpose of reducing deformation, and repeating the above casting simulation step S1, node coordinate conversion step S2 and simulation processing step S3 again until the foundryman obtains the applicable casting parameters, optimizes the casting parameters according to the casting processing deformation result, and reduces the casting cost.

[0072] Reference is made to the accompanying drawings Figure 5 In some embodiments, the implementation process of the casting processing deformation prediction method of the present application is described by taking the casting of an aluminum alloy thin-walled cylindrical shell as an example: First, the casting process simulation of the cylindrical shell is performed using Procast.

[0073] As shown in Figure 6 , a three-dimensional model of the cylindrical shell is established using a three-dimensional modeling software, and is saved as a file in.igs format. The model is imported into the Mesh module of Procast, a mold model is established in the Mesh module, the surface mesh is divided, and the body mesh is divided according to the surface mesh. The body mesh is a tetrahedral mesh.

[0074] In the Cast module, the casting process simulation parameters are set. The casting type is set to low pressure die casting, the material is aluminum alloy, the pouring port liquid pressure is 0.6 MPa (the actual pouring pressure is 0.6 MPa), and other parameters are set to conventional settings. Those skilled in the art should set them according to the actual situation, which will not be described here.

[0075] As shown in Figure 7 , the casting residual stress result is obtained after the simulation calculation is completed. When the casting residual stress result is output, the output type is set to Profile, the coordinate of the output parameter is from z=0 to z=40, the step increment Δ=01, the coordinates of x and y are points on the circular ring from r=150 mm to r=180 mm, and the coordinate increment of x and y is taken as 10°. Since the structure is symmetrical, the coordinate increment of x and y is taken as 180°, and the x and y radial direction values are set by default by the program. The output data result file is in.xyn format.

[0076] Secondly, the casting residual stress data is fitted.

[0077] As shown in Figure 8The data in the residual stress results of this casting simulation. xyn file is read, and Origin software is used for curve fitting for each set of data. According to the stress distribution characteristics, the least squares method is used for curve fitting this time. The data x-coordinate unit is cm, and the y-coordinate unit is MPa. Taking the coordinates z=20, x=0 to 36, and y=0 as an example for illustration.

[0078] In the data scatter plot, the x-axis is the x-coordinate value, and the y-axis is the equivalent stress value. Because the model is cylindrical and the wall thickness is 3 cm, there is no stress data in the range of x=3 cm to 33 cm, which is hollow.

[0079] As Figure 9 shown, Origin curve fitting is used in the range of x=0 to 3 cm, and the result expression is as follows: y=108.844+0.668x+0.521x^2-0.284x^3+0.047x^4; As Figure 10 shown, Origin curve fitting is used in the range of x=33 to 36 cm, and the result expression is as follows: y=-11704.944+1378.447x-60.185x^2+1.166x^3-0.008x^4.

[0080] Finally, the casting residual stress is loaded into the ABAQUS finite element model for machining simulation.

[0081] As Figure 11 shown, ABAQUS finite element meshing is different from Procast meshing. According to the result expression obtained by fitting the casting residual stress data, the stress at the grid nodes is calculated, and the stress value is loaded onto the grid nodes through the Load module of ABAQUS software. The "Element Birth / Death" technology is used to simulate the machining process.

[0082] The implementation process of the "Element Birth / Death" technology is set in the Step module. This machining simulation simulates turning two knives, and the turning thickness is 9 mm. Two analysis steps are set in the Step module. The first analysis step "kills" (Element Death) the first layer of 9 mm geometry, and the second analysis step "kills" the second layer of 9 mm geometry.

[0083] As Figure 12 Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 shown, it can be seen from the figure that under the action of casting stress, the casting has a tendency to shrink after machining. The reason is that the wall thickness of the casting becomes thinner after machining. The residual stress on the outside of the casting is compressive stress, and the residual stress on the inside is tensile stress. After the material on the outside of the casting is removed, the tensile stress is released, and the casting shrinks towards the inside.

[0084] Based on the above simulation process, the predicted result of the machining deformation can be obtained. Based on the wall thickness of the simulated casting, the wall thickness after simulation is 12, the maximum deformation of the casting is 0.19, and the actual wall thickness of the casting after machining is between 3 and 5 mm. The actual deformation is larger than the simulation result, so it is necessary to control the casting residual stress to reduce the deformation.

[0085] For the above obtained casting deformation result, the casting stress can be reduced by setting the chill, the riser at different positions of the casting. After setting the chill, the riser, the above casting machining deformation prediction method can be repeated to optimize the casting structure. Specific embodiment two The application also provides a casting machining deformation prediction system for realizing any one of the casting machining deformation prediction methods in the above specific embodiment one.

[0087] The casting machining deformation prediction system comprises a casting simulation module, a node coordinate conversion module and a simulation machining module.

[0088] The casting simulation module establishes a casting model through a three-dimensional modeling software; after the casting model is divided into tetrahedral meshes, the casting simulation is performed through a low-pressure casting mode to obtain a casting residual stress simulation result, and the casting residual stress simulation result comprises stresses of node coordinates on the tetrahedral meshes; The node coordinate conversion module performs curve fitting on the casting residual stress simulation result to obtain a stress curve formed by fitting the node coordinates on the tetrahedral meshes; after the casting model is divided into hexahedral meshes, the stresses of node coordinates on the hexahedral meshes are obtained by substituting the stress curve for calculation; The simulation machining module loads the stresses of node coordinates on the hexahedral meshes to the grid nodes of the casting model, and then obtains the deformation result of the casting model after machining by simulating the material removal process of the part.

[0089] In some embodiments, the casting simulation module further comprises: The modeling unit is configured to establish a casting model through a three-dimensional modeling software, and the casting model comprises a casting part model, a chill model and a riser model; The first mesh division unit is configured to import the casting model into a Mesh module of Procast software, and establish a sand box model in the Mesh module to divide the casting model into tetrahedral meshes; The parameter setting unit is configured to set casting process simulation parameters and result output configurations in a Cast module of the Procast software, and perform casting simulation on the casting model in a low-pressure casting mode to obtain the casting residual stress simulation result.

[0090] In some embodiments, the node coordinate conversion module further comprises: a fitting preparation unit configured to draw a stress scatter plot of each node coordinate on the tetrahedral mesh in the numerical analysis software according to the casting residual stress simulation result; a fitting selection unit configured to select a curve fitting method based on the contour shape of the stress scatter plot, to obtain a stress curve fitted by each node coordinate on the tetrahedral mesh, the curve fitting method including a least square method, a kernel method, and a spline method.

[0091] In some embodiments, the node coordinate conversion module further comprises: a second mesh division unit configured to import the casting model into the ABAQUS software to perform hexahedral mesh division; a conversion calculation unit configured to calculate the stress of each node coordinate on the hexahedral mesh according to the stress curve.

[0092] In some embodiments, the simulation machining module further comprises: a stress loading unit configured to import the stress of each node coordinate on the hexahedral mesh into the Load module of the ABAQUS software, and load the stress of each node coordinate on the hexahedral mesh to the grid nodes of the casting model through the Load module; a machining simulation unit configured to simulate the material removal process of the part through the ABAQUS software to obtain the deformation result of the casting model after machining.

[0093] The present application provides a casting machining deformation prediction method and system. The casting residual stress simulation result is curve fitted through the node coordinate conversion step, so that the stress of each node coordinate on the tetrahedral mesh is converted to the stress of each node coordinate on the hexahedral mesh through the stress curve, thereby solving the problem that different software cannot directly transfer node stress data, enabling the node stress data of other software to be applied to machining simulation software, simulating the whole process from casting to machining of the part, reducing the part development cost, and improving the production efficiency. The casting process is simulated through the casting simulation step, facilitating the obtaining of the casting residual stress simulation result, laying the foundation for subsequent machining simulation. The machining process is simulated through the simulation machining step, facilitating the obtaining of the deformation result of the casting model at each machining stage, so that the casting process can be optimized according to the deformation condition.

[0094] Finally, it should be noted that: the embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts of each embodiment can be referred to each other.

[0095] The above examples are only used to illustrate the technical solutions of the present application but not to limit the present application; although the present application has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that the specific implementation of the present application can be modified or equivalent replacements can be made to some technical features without departing from the spirit of the technical solutions of the present application, and all of them should be covered in the technical solution range of the present application claimed.

Claims

1. A method for predicting casting deformation, characterized in that: include: a casting simulation step, establishing a casting model using 3D modeling software; dividing the casting model into a tetrahedral mesh, and then performing a casting simulation using a low-pressure casting mode to obtain a casting residual stress simulation result, wherein the casting residual stress simulation result includes the stress of each node coordinate on the tetrahedral mesh; a node coordinate conversion step, performing curve fitting on the casting residual stress simulation result to obtain a stress curve formed by fitting the coordinates of each node on the tetrahedral mesh; after dividing the casting model into a hexahedral mesh, the stress curve is substituted into the stress curve for calculation to obtain the stress of each node coordinate on the hexahedral mesh; The simulation processing step loads the stress of each node coordinate on the hexahedral grid to the grid node of the casting model, and then obtains the deformation result of the casting model after processing by simulating the part material removal process.

2. The casting processing deformation prediction method according to claim 1, characterized in that: The casting simulation step further comprises: A modeling step, establishing the casting model using three-dimensional modeling software, wherein the casting model includes a casting part model, a chill model, and a riser model; The first meshing step is to import the casting model into the Mesh module of the Procast software, and establish a sand box model in the Mesh module to perform tetrahedral meshing; The parameter setting step is to set the casting process simulation parameters and result output configuration in the Cast module of the Procast software, perform casting simulation on the casting model in a low-pressure casting mode, and obtain the casting residual stress simulation result.

3. The casting processing deformation prediction method according to claim 1, characterized in that: The node coordinate conversion step further comprises: A fitting preparation step, drawing a stress scatter plot of each node coordinate on a tetrahedral mesh in numerical analysis software according to the casting residual stress simulation results; The fitting selection step selects a curve fitting method based on the contour shape of the stress scatter plot to obtain a stress curve formed by fitting the coordinates of each node on the tetrahedral grid. The curve fitting method includes the least squares method, the kernel method and the spline method.

4. The casting processing deformation prediction method according to claim 3, characterized in that: The node coordinate conversion step further includes: The second meshing step is to import the casting model into ABAQUS software to perform hexahedral meshing; The conversion calculation step calculates the stress of each node coordinate on the hexahedral grid according to the stress curve.

5. The casting processing deformation prediction method according to claim 1, characterized in that: The simulation processing step further includes: a stress loading step, importing the stress of each node coordinate on the hexahedral mesh into the Load module of ABAQUS software, and loading the stress of each node coordinate on the hexahedral mesh onto the mesh nodes of the casting model through the Load module; The processing simulation step is to simulate the part material removal process through the ABAQUS software to obtain the deformation result of the casting model after processing.

6. A casting processing deformation prediction system, characterized in that: include: A casting simulation module is used to establish a casting model using 3D modeling software; after dividing the casting model into a tetrahedral mesh, a casting simulation is performed using a low-pressure casting mode to obtain a casting residual stress simulation result, wherein the casting residual stress simulation result includes the stress of each node coordinate on the tetrahedral mesh; A node coordinate conversion module performs curve fitting on the casting residual stress simulation result to obtain a stress curve formed by fitting the coordinates of each node on the tetrahedral mesh; after dividing the casting model into a hexahedral mesh, the stress curve is substituted into the stress curve for calculation to obtain the stress of each node coordinate on the hexahedral mesh; The simulation processing module loads the stress of each node coordinate on the hexahedral grid to the grid nodes of the casting model, and then obtains the deformation result of the casting model after processing by simulating the part material removal process.

7. The casting processing deformation prediction system according to claim 6, characterized in that: The casting simulation module further includes: A modeling unit, configured to establish the casting model using three-dimensional modeling software, wherein the casting model includes a casting part model, a chill model, and a riser model; a first meshing unit, for importing the casting model into a Mesh module of Procast software, and establishing a sand box model in the Mesh module for tetrahedral meshing; The parameter setting unit is used to set the casting process simulation parameters and result output configuration in the Cast module of the Procast software, perform casting simulation on the casting model in a low-pressure casting mode, and obtain the casting residual stress simulation result.

8. The casting processing deformation prediction system according to claim 6, characterized in that: The node coordinate conversion module further includes: A fitting preparation unit, used for drawing a stress scatter diagram of the coordinates of each node on the tetrahedral grid in a numerical analysis software according to the casting residual stress simulation result; A fitting selection unit is used to select a curve fitting method based on the contour shape of the stress scatter plot to obtain a stress curve formed by fitting the coordinates of each node on the tetrahedral grid. The curve fitting method includes a least squares method, a kernel method, and a spline method.

9. The casting processing deformation prediction system according to claim 8, characterized in that: The node coordinate conversion module further includes: A second meshing unit is used to import the casting model into ABAQUS software to perform hexahedral meshing; The conversion calculation unit is used to calculate the stress of each node coordinate on the hexahedral grid according to the stress curve.

10. The casting processing deformation prediction system according to claim 6, characterized in that: The simulation processing module further includes: A stress loading unit, configured to import the stress of each node coordinate on the hexahedral mesh into the Load module of the ABAQUS software, and load the stress of each node coordinate on the hexahedral mesh onto the mesh nodes of the casting model through the Load module; The processing simulation unit is used to simulate the part material removal process through the ABAQUS software to obtain the deformation result of the casting model after processing.

Images