Method for predicting residual stress of die casting based on finite volume method, computer and storage medium
Based on a limited volume method, the solidification process of simulation castings and calculation of residual stress solves the problem of large workload, long time and low accuracy in the existing technology, and realizes the fast, accurate, accurate, accurate, accurate, and accurate of large casting residual stress and contraction. Forecasting has reduced calculation costs.
Patent Information
- Application Number
- CN202411463308.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-21
- Publication Date
- 2025-01-21
AI Technical Summary
The prior art simulates the residual stress in the casting process of large-scale die castings of aluminum alloys, and the calculation workload is huge, time-consuming and errors in accuracy, especially the coupling processing of semi-solid and liquid phase areas formed during the mold filling process is complicated. .
A method based on the finite volume method is used to construct a three-dimensional model of the die casting, simulate the solidification process to obtain the solidification temperature gradient, calculate the residual temperature and finally obtain the residual stress. This method simplifies the calculation process and reduces the calculation cost.
It achieves fast and accurate prediction of residual stress and shrinkage of large castings during the casting process, reduces calculation costs, and improves the efficiency of engineering applications.
Smart Images
Figure CN119337680A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of casting technology, and in particular to a residual stress prediction method for die castings based on a finite volume method, a computer and a storage medium. Background Art
[0002] In practical engineering applications, various commercial simulation tools have been developed in the field of casting technology to calculate the filling, solidification and residual stresses in the production of metal castings, molds and plastic technology. To calculate these problems, these tools use complex numerical methods in fluid and solid mechanics. In most cases, the calculation of each step involves the coupling of fluid and solid. Commercial software such as Flow3D has been developed for this simulation calculation process to simplify the calculation operation process. Although the development uses the finite element method to provide fully coupled fluid-solid interaction and thermal stress evolution, the stress modeling in the casting process usually leads to a coupled three-dimensional thermal physics problem, including solidification with time-varying boundary conditions. However, the simulation calculation amount of these commercial software is very large, time-consuming, and there are errors in the calculation accuracy.
[0003] The residual stresses in the casting process of large die castings of aluminum alloys are simulated and evaluated. During the filling process, partially solidified areas and semi-solid areas with liquid and solid phases are formed. At the current state of the art, the filling calculation uses fluid mechanics and changes in solid mechanics during solidification to deal with the stresses that occur. The solid phase expands as a moving interface, which can be numerically represented by coupled and moving field equations, but leads to a high computational workload. The coupling process and the formation of mixed zones with unknown material properties lead to a high degree of complexity. These mixed zones cannot be calculated like elastic-plastic regions. Summary of the invention
[0004] The purpose of this application is to provide a residual stress prediction method for die castings based on the finite volume method, a computer and a storage medium, which simulates the solidification of the casting and the resulting shrinkage to obtain the residual stress and shrinkage generated by the large casting during the casting process; at the same time, the simulated material properties and boundary conditions can produce faster and more accurate results for engineering applications. The proposed solution is easy to use and has low computational cost.
[0005] To achieve the above objectives, this application provides the following solutions:
[0006] In a first aspect, the present application provides a method for predicting residual stress of a die casting based on a finite volume method, comprising:
[0007] Build a model of the part to be die-cast;
[0008] Obtaining a solidification temperature gradient based on the solidification process simulated by the model;
[0009] calculating a residual temperature based on the curing temperature gradient;
[0010] A corresponding residual stress is calculated based on the residual temperature.
[0011] Preferably, the step of constructing a die casting model comprises:
[0012] constructing a three-dimensional model of the die casting;
[0013] Boundary conditions and material properties are set for the three-dimensional model.
[0014] Preferably, the boundary conditions include at least: temperature, displacement, and residual temperature.
[0015] Preferably, the material properties include at least: mechanical properties and thermal properties of the material.
[0016] Preferably, the step of calculating the residual stress of the die casting based on the solidification process comprises:
[0017] Controlling the model to simulate the solidification process through solidification process field calculation and processing software;
[0018] When it is detected that the temperature reaches the solidus temperature, the temperature gradient and solidification time of the solidification cell are recorded;
[0019] The curing temperature gradient is constructed based on the recorded temperature gradient and solidification time of each solidification cell.
[0020] Preferably, the step of calculating the residual temperature based on the curing temperature gradient comprises:
[0021] interpolating the curing temperature gradient from the cell center to the cell face;
[0022] Obtaining a cell with the longest solidification time, and setting the residual temperature of the cell to zero;
[0023] Create a priority list based on curing time;
[0024] Selecting a cell with the shortest curing time as the current cell based on the priority list;
[0025] Searching for adjacent cells of the current cell;
[0026] When the adjacent cells meet the preset conditions, the adjacent cells and the corresponding solidification time are added to the priority list;
[0027] Continue to execute the step of selecting the cell with the shortest curing time as the current cell based on the priority list, and stop executing when the priority list is empty;
[0028] The residual temperature is obtained by integrating the solidification temperature gradient along the solidification path of the model.
[0029] Preferably, the adjacent cells satisfying a preset condition include:
[0030] When the residual temperature of the adjacent cell has been set, skipping the adjacent cell;
[0031] If the residual temperature of the adjacent cell is not set, updating the residual temperature of the adjacent cell based on the residual temperature of the current cell and applying the residual temperature as an increment;
[0032] When the solidification time of the adjacent cell is less than the solidification time of the current cell, the update value is subtracted.
[0033] Preferably, the step of calculating the corresponding residual stress based on the residual temperature comprises:
[0034] The residual stress is obtained by calculating the residual temperature through field calculation and processing software of the residual stress.
[0035] In a second aspect, the present application provides a computer, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-mentioned method for predicting residual stress of die castings based on finite volume.
[0036] In a third aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method for predicting residual stress of a die casting based on finite volume as described above.
[0037] According to the specific embodiments provided in this application, this application discloses the following technical effects:
[0038] The present application provides a method, computer and storage medium for predicting residual stress of die castings based on the finite volume method. The method constructs a model of a large casting and controls the model to simulate the solidification and the resulting shrinkage of the casting, so as to obtain the residual stress and shrinkage generated by the large casting during the casting process. At the same time, the simulated material properties and boundary conditions can produce faster and more accurate results for engineering applications. The proposed solution is easy to use and has low computational cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0039] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0040] Figure 1 A schematic flow chart of a method for predicting residual stress of die castings based on the finite volume method provided in an embodiment of the present application.
[0041] Figure 2 A schematic diagram of a flow chart for calculating the residual stress of the die casting based on the solidification process provided in an embodiment of the present application;
[0042] Figure 3 A schematic diagram of the solidification process effect provided in an embodiment of the present application;
[0043] Figure 4 A schematic diagram of a flow chart for calculating the residual temperature based on the curing temperature gradient provided in an embodiment of the present application. DETAILED DESCRIPTION
[0044] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0045] The casting filling process is a typical multiphase flow problem, which involves the liquid-solid transition of the metal phase and the interaction between the air and the metal phase, such as the gas hindering the flow of the metal phase and the gas being drawn into the molten metal. The deformation and displacement caused by the residual stress during the filling and solidification process in the die casting are a serious defect in the casting process. Excessive residual stress and deformation will cause the casting to fail. In order to improve the qualified rate of the casting, the residual stress and deformation in the casting process can be predicted first, and the accuracy of the numerical simulation calculation can be improved first, and then mass production can be carried out, reducing the research and development cost. The present invention establishes a gas-liquid-solid multiphase mathematical model based on openfoam, and then performs numerical simulation of the casting filling process, simulates the filling and solidification process, and predicts the strain and displacement that may be generated in the casting.
[0046] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.
[0047] Example 1
[0048] refer to Figure 1 As shown, the present application provides a method for predicting residual stress of a die casting based on a finite volume method, comprising:
[0049] Build a model of the part to be die-cast;
[0050] Obtaining a solidification temperature gradient based on the solidification process simulated by the model;
[0051] calculating a residual temperature based on the curing temperature gradient;
[0052] A corresponding residual stress is calculated based on the residual temperature.
[0053] In an embodiment of the present application, before predicting the residual stress of a large casting, a three-dimensional model of the die casting is first constructed using modeling software, such as using CAD software, SolidWorks software, UG software, and pro / e software to construct a three-dimensional model corresponding to the casting for which the residual stress is to be predicted. Furthermore, the mesh tool snappyHexMesh in the computational fluid dynamics (CFD) class library openFoam is used to generate a mesh model from the three-dimensional model, and the edge length information is set. The computational fluid dynamics (CFD) class library openFoam is further used to set the boundary conditions of the three-dimensional model, such as temperature, displacement, and residual temperature. In this embodiment, the model can also adopt the boundary condition of a fixed value of the outer surface to avoid the introduction of the heat transfer coefficient. The model inputs material properties such as the mechanical properties and thermal properties of the material to simulate and evaluate the residual stress in the casting process of large aluminum alloy die castings.
[0054] In the embodiments of the present application, the relationship between the mechanical properties and thermal properties of the material is expressed as follows:
[0055]
[0056] Mechanical properties: E is Young's modulus, ρ is density, ν is Poisson's ratio, α is thermal expansion coefficient, where Young's modulus is obtained from the bending strength test of the rod, as shown in Table 1 for the mechanical properties used for simulation:
[0057] <![CDATA[E[N / m 2 ]]]> <![CDATA[ρ[kg / m 3 ]]]> ν[-] <![CDATA[α[K -1 ]]]> 2.925e+09 2060 0.26 3.8e-05
[0058] Table 1
[0059] Thermal properties: where s and l are the solid and liquid phases, respectively, c is the isobaric heat capacity, T is the phase transition temperature, λ is the thermal conductivity, and L is the latent heat of fusion, as shown in Table 2 for the simulated thermal properties:
[0060]
[0061] Table 2
[0062] After the casting model is constructed, the model is further controlled to simulate the solidification process of the casting, and the solidification temperature gradient of the model is obtained based on the simulated solidification process through the solidification process field calculation and processing software solidification Foam. res Integrator calculates the residual temperature based on the curing temperature gradient of the obtained model, and further calculates the residual stress field and processes it with the software T res StressFoam calculates the residual stress of the model based on the obtained residual temperature and confirms the residual stress as a prediction of the residual stress generated in the casting during the casting process.
[0063] refer to Figure 2 As shown, the step of calculating the residual stress of the die casting based on the solidification process provided by the present application includes:
[0064] Controlling the model to simulate the solidification process through solidification process field calculation and processing software;
[0065] When it is detected that the temperature reaches the solidus temperature, the temperature gradient and solidification time of the solidification cell are recorded;
[0066] The curing temperature gradient is constructed based on the recorded temperature gradient and solidification time of each solidification cell.
[0067] In the embodiment of the present application, when simulating the solidification process based on the constructed model, the following assumptions are first made: a. At the beginning of the solidification process, the mold is completely filled with liquid salt at a given temperature. Liquid shrinkage has no effect on the later deformation and is not considered; b. The solidified salt is demolded early enough, so its deformation can be considered to be completely elastic. Further, the model is controlled by the solidification process field calculation and processing software solidification Foam to simulate the solidification process. In the simulated solidification composition, when the solidification temperature reaches the solidus temperature T s When , strain is generated in the front of the material solidification, and the calculation expression of the strain force at this unit cell of the model is as follows:
[0068] Δε fr =α(T s )ΔT
[0069] Among them, Δε fr is the volume increment of the freezing strain, α(T s ) is the thermal expansion coefficient, ΔT is the temperature difference between the layers on both sides of the interface;
[0070] Further expanding the temperature difference through the Taylor series, we get:
[0071] Δε fr (r) = αT res (r)
[0072]
[0073] Among them, Tres represents the residual temperature field, which is defined as the contour integral of the temperature gradient at the solidification moment. Tres is the gradient field representing the strength of solidification shrinkage. Figure 3 Schematic diagram of the solidification process shown.
[0074] Furthermore, during the solidification simulation, the temperature gradient and solidification time of each cell in the model are recorded. The solidification temperature gradient of the model is formed through the temperature gradient and solidification time of all cells. Figure 3 As shown, for solidification, simplified boundary conditions assume that the material properties of each phase are constant, and the latent heat of fusion is taken into account during the phase change from liquid to solid.
[0075] refer to Figure 4 As shown, the step of calculating the residual temperature based on the curing temperature gradient provided in the present application includes:
[0076] interpolating the curing temperature gradient from the cell center to the cell face;
[0077] Obtaining a cell with the longest solidification time, and setting the residual temperature of the cell to zero;
[0078] Create a priority list based on curing time;
[0079] Selecting a cell with the shortest curing time as the current cell based on the priority list;
[0080] Searching for adjacent cells of the current cell;
[0081] When the adjacent cells meet the preset conditions, the adjacent cells and the corresponding solidification time are added to the priority list;
[0082] Continue to execute the step of selecting the cell with the shortest curing time as the current cell based on the priority list, and stop executing when the priority list is empty;
[0083] The residual temperature is obtained by integrating the solidification temperature gradient along the solidification path of the model.
[0084] In the embodiment of the present application, the temperature integrator T res The Integrator calculates the residual temperature of the model and passes the result of the first calculation to the next step to calculate the residual temperature. In this step, the solidification temperature gradient is integrated along the solidification path using the following formula:
[0085]
[0086] In the specific calculation process, the curing temperature gradient is first Interpolate from the cell center to the cell face, further search for the cell with the longest curing time, and set the residual temperature of the cell to zero, further create a priority list based on curing time to determine the order of processing cells, select the cell with the shortest curing time from the created priority list or the top item of the priority list, and use the cell with the shortest curing time as the current cell, further search all adjacent cells of the current cell, in the embodiment of the present application, if the residual temperature of the adjacent cell has been set, skip the cell, if not set, use the value in the current cell to update the residual temperature in the adjacent cell, and apply the residual temperature increment, the calculation expression of the increment is as follows: Among them, Δr is the distance between the current unit and the adjacent unit. When the solidification time of the adjacent unit is less than the solidification time of the current unit, the updated value is subtracted. Further, the adjacent unit together with the corresponding solidification time is added to the priority list of the wearer, and the step of selecting the cell with the shortest solidification time from the created priority list or the top entry of the priority list is continued until the priority list is empty, and the solidification temperature gradient is integrated along the solidification path of the model, that is, the residual temperature is calculated by integrating the temperature gradient recorded by each cell during the solidification process.
[0087] In the embodiment of the present application, after the residual temperature of the model is calculated, further calculating the corresponding residual stress based on the residual temperature specifically includes: using the residual stress field calculation and processing software T res StressFoam calculates the residual temperature to obtain the residual stress. Specifically, the following formula is used to solve the thermoelastic problem to calculate the residual stress:
[0088]
[0089] Example 2
[0090] The present application provides a computer, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-mentioned method for predicting residual stress of die castings based on finite volume.
[0091] Example 3
[0092] The present application provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the method for predicting residual stress of a die casting based on a finite volume as described in the above embodiment 1 are implemented.
[0093] In summary, the method of the present application can greatly reduce the computational workload. When calculating the residual temperature, if the local maximum value of the solidification time is inconsistent, a simplified integrated method will be used to solve this problem, thereby avoiding common problems in complex welding line detection.
[0094] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0095] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.
Claims
1. A method for predicting residual stress of die castings based on finite volume method, characterized in that: The residual stress prediction method for die castings based on the finite volume method includes: Build a model of the part to be die-cast; Obtaining a solidification temperature gradient based on the solidification process simulated by the model; calculating a residual temperature based on the curing temperature gradient; A corresponding residual stress is calculated based on the residual temperature.
2. The residual stress prediction method for die casting based on finite volume according to claim 1 is characterized in that: The step of constructing a die casting model comprises: constructing a three-dimensional model of the die casting; Boundary conditions and material properties are set for the three-dimensional model.
3. The residual stress prediction method for die casting based on finite volume according to claim 2 is characterized in that: The boundary conditions include at least: temperature, displacement, and residual temperature.
4. The residual stress prediction method for die casting based on finite volume according to claim 2 is characterized in that: The material properties include at least: mechanical properties and thermal properties of the material.
5. The residual stress prediction method for die casting based on finite volume according to any one of claims 1 to 4, characterized in that: The step of calculating the residual stress of the die casting based on the solidification process comprises: Controlling the model to simulate the solidification process through solidification process field calculation and processing software; When it is detected that the temperature reaches the solid phase temperature, the temperature gradient and solidification time of the solidification cell are recorded; and a solidification temperature gradient is constructed based on the recorded temperature gradient and solidification time of each solidification cell.
6. The residual stress prediction method for die casting based on finite volume according to claim 5 is characterized in that: The step of calculating the residual temperature based on the curing temperature gradient comprises: interpolating the curing temperature gradient from the cell center to the cell face; Obtaining a cell with the longest solidification time, and setting the residual temperature of the cell to zero; Create a priority list based on curing time; Selecting a cell with the shortest curing time as the current cell based on the priority list; Searching for adjacent cells of the current cell; When the adjacent cells meet the preset conditions, the adjacent cells and the corresponding solidification time are added to the priority list; Continue to execute the step of selecting the cell with the shortest curing time as the current cell based on the priority list, and stop executing when the priority list is empty; The residual temperature is obtained by integrating the solidification temperature gradient along the solidification path of the model.
7. The residual stress prediction method for die casting based on finite volume according to claim 6 is characterized in that: The adjacent cells satisfying the preset conditions include: When the residual temperature of the adjacent cell has been set, skipping the adjacent cell; If the residual temperature of the adjacent cell is not set, updating the residual temperature of the adjacent cell based on the residual temperature of the current cell and applying the residual temperature as an increment; When the solidification time of the adjacent cell is less than the solidification time of the current cell, the update value is subtracted.
8. The residual stress prediction method for die casting based on finite volume according to claim 6 is characterized in that: The step of calculating the corresponding residual stress based on the residual temperature comprises: The residual stress is obtained by calculating the residual temperature through field calculation and processing software of the residual stress.
9. A computer comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method for predicting residual stress of a die casting based on finite volume as described in any one of claims 1 to 8.
10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for predicting residual stress of a die casting based on finite volume described in any one of claims 1 to 8 are implemented.