A cross-software platform joint mechanical simulation method considering the uneven distribution of mechanical properties of castings

Abstract

The present invention provides a cross-software platform joint mechanical simulation method that takes into account the uneven distribution of mechanical properties of castings, which solves the problem of the current lack of an effective mechanical simulation method that takes into account the uneven mechanical properties of metal casting parts. The present invention is a mechanical simulation method that takes into account the uneven mechanical properties of metal casting parts based on casting mold flow analysis software to determine the cooling rate of each part of the casting, by establishing a material mechanical constitutive model related to the melt cooling rate, and on this basis, using finite element mechanical analysis software to implement a mechanical simulation method that takes into account the uneven mechanical properties of metal casting parts.

Description

Technical Field

[0001] The present invention belongs to the technical field of mechanical property simulation and structural design of metal material castings, and specifically relates to a cross-platform joint mechanical simulation method that takes into account the uneven mechanical property distribution of castings. Background Art

[0002] Casting is a widely used metal parts forming technology. Metal castings have complex structures and uneven wall thickness is common in various parts. During the solidification of molten metal in the casting cavity, the cooling rate of the parts with uneven wall thickness will also be different, and the uneven cooling rate will lead to differences in the microstructure and mechanical properties of various parts. Therefore, castings, especially complex castings, generally have uneven mechanical properties in various parts.

[0003] At present, most of the mechanical simulation and structural design methods of metal castings assume that the mechanical properties of each part of the component are the same and adopt a single material mechanical constitutive model. This treatment will inevitably lead to poor reliability and accuracy of force simulation and structural design, large structural redundancy of parts, and poor lightweight effect. Therefore, how to obtain a mechanical constitutive model related to the position of the casting by considering the uneven mechanical properties caused by the difference in wall thickness of the casting, and realize mechanical simulation that takes into account the uneven distribution of the mechanical properties of the casting, is of great significance to the force simulation and structural design of metal castings.

[0004] Therefore, it is possible to consider importing the model information and mechanical information of the casting simulation software into the mechanical simulation software for simulation, thereby obtaining the position in the model that needs structural optimization. For example: the Chinese patent document with the announcement date of April 29, 2009 and the announcement number of CN101419644A discloses a stress numerical analysis method of wheel external load considering residual stress, wherein the casting residual stress of the integral cast aluminum alloy automobile wheel is calculated by using the stress calculation module of Procast, and then a program is written to import the node information, unit information and residual stress data of the finite element grid of the wheel casting into the Ansys software, apply load to the wheel, and perform stress numerical analysis of the integral cast aluminum alloy wheel considering residual stress. This patent adds residual stress to the original mechanical properties of the wheel, but does not consider the uneven mechanical properties of the wheel. Therefore, its analysis results still have certain errors. Summary of the invention

[0005] In view of the current problem that there is still a lack of effective mechanical simulation methods that take into account the uneven mechanical properties of metal casting parts, the present invention provides a cross-software platform joint mechanical simulation method that takes into account the uneven distribution of mechanical properties of castings.

[0006] The concept of the present invention is:

[0007] Firstly, the mechanical constitutive model of casting alloy material related to cooling rate is obtained through standard casting experiments, mechanical property tests and material mechanics constitutive modeling methods; then, the cooling rate of different positions of the casting during the filling process is simulated by mold flow analysis software (EASYCAST, ProCAST, etc.), and the original file containing the casting position coordinate information and cooling rate is exported; further, through programming, based on the obtained mechanical constitutive model related to cooling rate, the material mechanics constitutive equations corresponding to different positions of the casting are calculated; finally, according to the data format of commercial finite element software (such as ABAQUS, etc.), Matlab programming is used to convert the casting position coordinates and material mechanics constitutive equations into a format readable by the software, and the finite element model of the casting coupled with the inhomogeneous mechanical constitutive equation is obtained, and mechanical simulation is carried out through finite element software.

[0008] To achieve the above purpose, the technical solution provided by the present invention is:

[0009] A cross-software platform joint mechanical simulation method considering the uneven distribution of mechanical properties of castings is special in that it includes the following steps:

[0010] S1. Obtain stress-strain curves of heat-treated / cast samples at different cooling rates

[0011] S1.1 By designing casting molds with different wall thicknesses, the cooling rate distribution is between 0 and 120 K / s, and more than 7 groups of samples with different cooling rates are obtained. The technicians in this field may perform or not perform subsequent heat treatment according to the specific situation, and perform standard mechanical property tests on the prepared heat-treated / cast samples to obtain stress-strain curves of heat-treated / cast samples with different cooling rates;

[0012] S1.2 Using the stress-strain curve of a sample at a certain cooling rate

[0013]

[0014] The specific values ​​of K1 and K2 at the cooling rate were obtained by fitting (obtained by fitting with Origin software);

[0015] Where σ is stress, K1 is the strain hardening coefficient, K2 is the dynamic recovery coefficient, ε is strain, σ 0.002 is the yield strength when the strain reaches 0.002, obtained experimentally;

[0016] Establish K1, K2, σ 0.002 Corresponding relationship with cooling rate;

[0017] S1.3 Using K1, K2, σ 0.002 Corresponding relationship with cooling rate, K1, K2, σ are obtained by data fitting0.002 The quantitative relationship between the measured material and the cooling rate can be obtained by substituting the quantitative relationship into formula (1).

[0018] Specifically, a new function is established in the Origin software for fitting; K1, K2 and σ 0.002 All of them are related to the cooling rate, and these three parameters can be replaced by their quantitative relationship with the cooling rate.

[0019] S2. Obtain the corresponding relationship between the casting position coordinates and the cooling rate in the mold flow analysis software:

[0020] Through mold flow analysis software, the temperature field changes at different positions of the casting after the melt fills the casting cavity under different casting process conditions (different casting processes, i.e., different casting conditions such as gravity casting and low-pressure casting) are analyzed. The cooling rate of the melt before the casting solidifies is selected as the cooling rate at each position to obtain the corresponding relationship between the casting position coordinates and the cooling rate.

[0021] S3, using the corresponding relationship between the casting position coordinates and the cooling rate obtained in S2 to solve the material mechanics constitutive equation of each position coordinate point of the casting, and assigning the constitutive equation to the specific coordinate position through programming according to the data format required by the mechanical simulation software, and compiling the input file of the simulation software;

[0022] S4. Use finite element analysis software to open the input file compiled in S3 to obtain the finite element model of the casting coupled with the inhomogeneous mechanical constitutive equation. By setting the force conditions, the mechanical simulation and structural optimization design of the metal casting considering the inhomogeneity of mechanical properties can be realized.

[0023] Furthermore, in S2, the mold flow analysis software is EASYCAST or ProCAST.

[0024] Furthermore, in S3, the data format is the .inp file of ABAQUS.

[0025] Furthermore, in S4, the finite element analysis software is ABAQUS.

[0026] The advantages of the present invention are:

[0027] 1. The present invention is a mechanical simulation method that takes into account the non-uniformity of mechanical properties of metal casting parts by determining the cooling rate of each part of the casting based on casting mold flow analysis software, establishing a material mechanics constitutive model related to the melt cooling rate, and on this basis using finite element mechanics analysis software.

[0028] 2. Although the cooling rate of different parts of the casting during the solidification process is different due to the difference in wall thickness, which leads to differences in microstructure and mechanical properties, it is a common phenomenon in almost all metal castings. However, due to the lack of effective and reliable mechanical simulation methods, the current simulation of metal castings has to adopt a single material constitutive model, assuming that the mechanical properties of various parts of the casting are the same everywhere. Therefore, the method proposed in the present invention can determine the material constitutive equation according to the melt cooling rate during the solidification process at different positions of the casting through cross-platform joint simulation of casting filling process and finite element stress, and make the stress-strain interval smaller through programming. The smaller the interval, the higher the accuracy of the casting mechanical simulation, the more accurate the prediction of the mechanical response of the casting under load conditions, and the more accurate the structural optimization of the casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a flowchart for implementing a cross-software platform joint mechanical simulation method that takes into account the uneven distribution of mechanical properties of castings.

[0030] Figure 2 This is a distribution cloud diagram of the melt cooling rate in the three-dimensional space of an A356 aluminum alloy casting under typical metal mold casting conditions obtained by performing filling simulation using ProCAST casting simulation software in Example 1.

[0031] Figure 3 The tensile stress-strain curve of A356 cast aluminum alloy in the T6 heat treatment state was experimentally measured for Example 1.

[0032] Figure 4 The corresponding relationship between the mechanical constitutive parameters of A356 aluminum alloy in Example 1 and the melt cooling rate and the parameter values ​​obtained by data fitting.

[0033] Figure 5 This is the finite element model of the casting coupled with the inhomogeneous mechanical constitutive equation of Example 1.

[0034] Figure 6 For Example 1, the stress distribution cloud diagram of the casting under specific load conditions was simulated using ABAQUS finite element simulation software. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0036] A cross-software platform joint mechanical simulation method considering the uneven distribution of mechanical properties of castings is special in that it includes the following steps:

[0037] S1. Obtain stress-strain curves of heat-treated / cast samples at different cooling rates

[0038] S1.1 By designing casting molds with different wall thicknesses, the cooling rate distribution is between 0 and 120 K / s, and more than 7 groups of samples with different cooling rates are obtained. The technicians in this field may perform or not perform subsequent heat treatment according to the specific situation, and perform standard mechanical property tests on the prepared heat-treated / cast samples to obtain stress-strain curves of heat-treated / cast samples with different cooling rates;

[0039] S1.2 Using the stress-strain curve of a sample at a certain cooling rate

[0040]

[0041] The specific values ​​of K1 and K2 at the cooling rate were obtained by fitting (obtained by fitting with Origin software);

[0042] Where σ is stress, K1 is the strain hardening coefficient, K2 is the dynamic recovery coefficient, ε is strain, σ 0.002 is the yield strength when the strain reaches 0.002, obtained experimentally;

[0043] Establish K1, K2, σ 0.002 Corresponding relationship with cooling rate;

[0044] S1.3 Using K1, K2, σ 0.002 Corresponding relationship with cooling rate, K1, K2, σ are obtained by data fitting 0.002 The quantitative relationship between the measured material and the cooling rate can be obtained by substituting the quantitative relationship into formula (1).

[0045] Specifically, a new function is established in the Origin software for fitting; K1, K2 and σ 0.002 All of them are related to the cooling rate, and these three parameters can be replaced by their quantitative relationship with the cooling rate.

[0046] S2. Obtain the corresponding relationship between the casting position coordinates and the cooling rate in the mold flow analysis software:

[0047] Through mold flow analysis software (EASYCAST, ProCAST), analyze the temperature field changes at different positions of the casting after the melt fills the casting cavity under different casting process conditions (different casting processes, i.e., different casting conditions such as gravity casting and low-pressure casting), select the cooling rate of the melt before the casting solidifies as the cooling rate at each position, and obtain the corresponding relationship between the casting position coordinates and the cooling rate;

[0048] S3, using the corresponding relationship between the casting position coordinates and the cooling rate obtained in S2 to solve the material mechanics constitutive equation of each position coordinate point of the casting, and assigning the constitutive equation to the specific coordinate position through programming according to the data format required by the mechanical simulation software (.inp file of ABAQUS), and compiling the input file of the simulation software;

[0049] S4. Use finite element analysis software (ABAQUS) to open the input file compiled in S3 and obtain the finite element model of the casting coupled with the inhomogeneous mechanical constitutive equation. By setting the stress conditions, the mechanical simulation and structural optimization design of the metal casting considering the inhomogeneity of mechanical properties can be realized.

[0050] The following are specific embodiments:

[0051] The model and cooling rate information were obtained through ProCAST casting simulation software, and then imported into ABAQUS to perform mechanical simulation on a typical A356 casting. The specific steps include:

[0052] Step 1. Obtain the mesh file in ProCAST. After the casting simulation is completed, open the g.unf file in the Viewer section, then click Mesh in the upper left corner, click Export in the File drop-down menu, and output the g.inp file.

[0053] Step 2: Obtain the cooling rate file in ProCAST. The cooling rate is distributed in three dimensions in the casting. Figure 2 As shown. In the Viewer section of ProCAST, click Metallurgical Tools in the Results drop-down menu, select R, G, L, and according to the nyiamacriterion calculation criteria, fill in 1 for A, 0 for B, 1 for C, -0.5 for D, 615 (Tliquidus+2) for L upper temperature, 548 (Tsolidus) for L lower temperature, and 554.5 (Tsolidus+0.1*(Tliquidus-Tsolidus)) for R and G temperature. Then calculate the cooling rate distribution of ProCAST casting simulation, select node in the selection menu bar, select the model (select only the casting), click Export As in the File drop-down menu, and then select PATRAN, I-DEAS, STL, G3D... This item outputs the cooling rate file .ntl with node numbers.

[0054] Step 3. Open the cold speed file .ntl, delete the first four lines, and obtain the cold speed file lengsu.txt which only contains two columns of information: node number and cold speed.

[0055] Step 4: Get the element information in the g.inp file. Obtain the file element.txt containing the element number and the corresponding node number through Matlab programming.

[0056] Step 5: Get the node information in the g.inp file. Obtain the file node.txt containing the node number and its coordinates through Matlab programming.

[0057] Step 6. Obtain the pro01.inp file that can be imported into ABAQUS. Through Matlab programming, combined with lengsu.txt, element.txt, and node.txt, set each element as a set, and then set each set as a section. The material corresponding to each section is the property obtained by substituting the cooling rate of each element into the mechanical constitutive model. The mechanical constitutive model is obtained based on Figure 3 The stress-strain curve shown in the figure obtains the mechanical constitutive equation at each cooling rate, and the data fitting results are as follows: Figure 4 K1, K2, YS (σ 0.002 ) and the cooling rate, and substitute it into formula (1) to obtain formula (2), which is the mechanical constitutive model of A356 aluminum alloy after T6 treatment. Finally, it is integrated into the pro01.inp file that can be imported into ABAQUS. This file is imported into ABAQUS and the pressure around the hub and the central constraint are applied to it, such as Figure 5 As shown. After calculation in ABAQUS, the stress results are as follows Figure 6 shown.

[0058] Formula 2 is the material constitutive equation of the A356 aluminum alloy coupled with the melt cooling rate in Example 1.

[0059]

[0060] where σ is the stress, is the cooling rate and ε is the strain.

[0061] In summary, by using the cross-software platform joint mechanical simulation method proposed in the present invention that takes into account the uneven distribution of mechanical properties of castings, a casting model with uneven mechanical properties based on cooling rate can be obtained, which is used to adjust the casting model and casting conditions.

[0062] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. A cross-software platform joint mechanical simulation method considering the uneven distribution of mechanical properties of castings, It is characterized in that The following steps are involved: S1. Obtain the mechanical constitutive equation related to the measured material and cooling rate: S1.1 By designing casting molds with different wall thicknesses, the cooling rate distribution is between 0 and 120 K / s, and more than 7 groups of samples with different cooling rates are obtained. Depending on the specific situation, subsequent heat treatment is performed or not performed, and standard mechanical properties tests are performed on the prepared heat-treated / cast samples to obtain stress-strain curves of heat-treated / cast samples with different cooling rates; S1.2 Using the stress-strain curve of a sample at a certain cooling rate The specific values ​​of K1 and K2 at this cooling rate are obtained by fitting; Where σ is stress, K1 is the strain hardening coefficient, K2 is the dynamic recovery coefficient, ε is strain, σ 0.002 is the yield strength when the strain reaches 0.002, obtained experimentally; Establish K1, K2, σ 0.002 Corresponding relationship with cooling rate; S1.3 Using K1, K2, σ 0.002 Corresponding relationship with cooling rate, K1, K2, σ are obtained by data fitting 0.002 The quantitative relationship between the measured material and the cooling rate can be obtained by substituting the quantitative relationship into formula (1). S2. Obtain the corresponding relationship between the casting position coordinates and the cooling rate in the mold flow analysis software: Through mold flow analysis software, the temperature field changes at different positions of the casting are analyzed after the melt fills the casting cavity under different casting process conditions. The cooling rate of the melt before the casting solidifies is selected as the cooling rate at each position to obtain the corresponding relationship between the casting position coordinates and the cooling rate. S3, using the corresponding relationship between the casting position coordinates and the cooling rate obtained in S2 to solve the material mechanics constitutive equation of each position coordinate point of the casting, and assigning the constitutive equation to the specific coordinate position through programming according to the data format required by the mechanical simulation software, and compiling the input file of the simulation software; S4. Use finite element analysis software to open the input file compiled in S3 to obtain the finite element model of the casting coupled with the inhomogeneous mechanical constitutive equation. By setting the force conditions, the mechanical simulation and structural optimization design of the metal casting considering the inhomogeneity of mechanical properties can be realized.

2. The cross-software platform joint mechanical simulation method considering the uneven mechanical property distribution of castings according to claim 1, Features: In S2, the mold flow analysis software is EASYCAST or ProCAST.

3. According to claim 2, the cross-software platform joint mechanical simulation method considering the uneven distribution of mechanical properties of castings, Features: In S3, the data format is ABAQUS .inp file.

4. The cross-software platform joint mechanical simulation method considering the uneven distribution of mechanical properties of castings according to claim 3, Features: In S4, the finite element analysis software is ABAQUS.

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