Parameter acquisition method of Shima-Oyane constitutive model of metal and nonmetal mixed powder

Abstract

The invention discloses a method for acquiring parameters of a Shima-Oyane constitutive model of metal and non-metal mixed powder, which comprises the following steps of: 1, acquiring a pressure-density relationship of powder compression through an experiment, 2, acquiring the pressure-density relationship through simulation, 3, constructing a target function by taking the minimum difference between the pressure-density relationship and the pressure-density relationship as a target, and performing optimization solution on the target function by adopting a simplex method to obtain the parameter of the Shima-Oyane constitutive model of the metal and non-metal mixed powder. The optimal constitutive parameters of the non-single material powder are obtained. According to the method, the optimal constitutive model parameters in the pressing process of the metal and non-metal mixed powder can be effectively obtained, so that the production efficiency of the pressing process of the metal and non-metal mixed powder is improved.

Description

Technical Field

[0001] The present invention relates to the finite element simulation direction of powder pressing process, and more specifically to solving the problem that the parameters of the constitutive model of metal and non-metal mixed powder simulation are difficult to obtain accurately through experiments. Background Art

[0002] With the continuous development of modern technology, the design process of various modern weapons and equipment based on explosives increasingly requires higher energy density and better charge quality. In the process of design and optimization of explosive pressing process, the use of finite element simulation technology to simulate and predict the pressing process is an important link. The numerical simulation of explosive powder pressing requires accurate constitutive model parameters. Traditionally, the determination of material model parameters depends on molding experiments, uniaxial compression tests, triaxial compression tests or some special experiments. The purpose of most material parameter experiments is to obtain stress, pressure, strain and other related state variables under the same conditions. However, it is very difficult and expensive to achieve the same conditions, and it is almost impossible to obtain them completely in experiments. Therefore, how to efficiently and accurately obtain the simulation constitutive model parameters of powder materials is an important step.

[0003] The known powder material simulation constitutive model parameters are obtained through experimental methods. The powder after compression molding is sintered and its constitutive model parameters are obtained by testing its mechanical curve. However, metal and non-metal mixed powders cannot be sintered, and accurate material parameters cannot be obtained by this method, which affects the simulation accuracy of the metal and non-metal mixed powder pressing process. In production, the pressing process parameters are still determined by experiments, which results in high production costs and low efficiency of mixed powder compression. Summary of the invention

[0004] In order to solve the deficiencies of the above-mentioned prior art, the present invention provides a method for obtaining parameters of the Shima-Oyane constitutive model of metal and non-metal mixed powder, so as to accurately determine the constitutive model parameters of the metal and non-metal mixed powder, thereby improving the production efficiency of the metal and non-metal mixed powder pressing process.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme:

[0006] The method for obtaining parameters of the Shima-Oyane constitutive model of a metal and non-metal mixed powder of the present invention is characterized in that it comprises the following steps:

[0007] Step 1: Make a groups of samples, and each group of samples contains A sample, each sample is composed of a powder material mixed with metal and non-metal;

[0008] use Different pressure Respectively The samples of each group are pressed, and the density of each sample in each group after pressing is measured, and the average density of each group of samples is taken to obtain the average density of each group of samples. ;in, represents the i-th pressure, represents the average density of the i-th group of samples, i∈[1,n];

[0009] Step 2: In the finite element software The sample group Different pressure The pressing process under the condition of ;in, represents the simulated average density of the i-th group of samples, i∈[1,n];

[0010] Step 2.1: Set the model geometry type of the plane entity in the finite element software, and set the material type of the model to plastic deformation material. The plastic deformation material is described using the Shima-Oyane constitutive model, which has 8 material parameters: ; thus establishing Axisymmetric model of group specimens;

[0011] Step 2.2: Set the relative density of the axisymmetric model to be the same as the initial density of the experimental pressing;

[0012] Step 2.3: Set the boundary conditions of the axisymmetric model to limit the displacement of the axis of symmetry of the axisymmetric model in the Y direction, and select any point on its axis of symmetry to limit the displacement of the axis of symmetry in the X direction;

[0013] Step 2.4: According to n different pressures , establish the same pressure-time curve as that in the experimental pressing, so as to establish n unit edge distributed force constraints on the outer boundary of the axisymmetric model;

[0014] Step 2.5: Use n different unit edge distribution force constraints to establish n corresponding working conditions for the axisymmetric model, and solve the axisymmetric model under each working condition to obtain the simulation average density corresponding to the n pressures. ;

[0015] Step 3: Solve the objective function using the simplex method with reflection strategy and obtain:

[0016] Step 3.1: Constitutive model parameters of powder material is a set of decision vectors X, so the objective function is constructed using formula (3) :

[0017] (3)

[0018] Step 3.2: Use the Nelder-Mead optimization algorithm to optimize the objective function Solve and find the initial vector , The constitutive model parameters of the metal powder in the mixed powder are obtained, and the optimal decision vector X is finally optimized. * These are the optimal constitutive model parameters for powder materials.

[0019] An electronic device of the present invention includes a memory and a processor, wherein the memory is used to store a program that supports the processor to execute the parameter acquisition method, and the processor is configured to execute the program stored in the memory.

[0020] The present invention provides a computer-readable storage medium, wherein a computer program is stored on the computer-readable storage medium, and the computer program executes the steps of the parameter acquisition method when the computer program is executed by a processor.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The method of the present invention obtains the Shima-Oyane constitutive parameters of metal and non-metal mixed powders based on the pressure-density relationship. The traditional method can only obtain the constitutive model parameters of powder materials containing only metal because it is necessary to test the mechanical properties of the pressed powder after sintering. The present invention solves the problem that the accurate Shima-Oyane constitutive model parameters of metal and non-metal mixed powders cannot be obtained, and provides a feasible method for realizing high-precision prediction of the powder pressing process in engineering.

[0023] 2. The present invention only needs to measure the density of the sample after the experiment. Compared with the prior art which requires a triaxial compression experiment to fit the constitutive model parameters, the method of the present invention has a simple principle, the required experimental equipment is easier to obtain, and the operating cost is low, making it easy to use in practice.

[0024] 3. The traditional "trial and error" experimental method requires repeated tests on metal and non-metal mixed powders to determine the optimal pressing process parameters, which is not only difficult and costly, but also inefficient. The present invention uses finite element software combined with a simplex optimization method, thereby reducing the number of actual pressing experiments and improving the efficiency of determining process parameters.

[0025] 4. The present invention obtains accurate constitutive model parameters of metal and non-metal mixed powders through simplex optimization. Using accurate constitutive model parameters for finite element simulation, designers can intuitively observe the density distribution and internal stress changes of explosives under different pressing parameters. This information provides a reliable basis for optimizing mold design, thereby improving the quality and consistency of molded explosives. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a flow chart of the method of the present invention;

[0027] Figure 2 It is a comparison chart of the density value simulated by the present invention and the density value obtained by experiment. DETAILED DESCRIPTION

[0028] In this embodiment, a method for obtaining parameters of a Shima-Oyane constitutive model of a metal and non-metal mixed powder is provided. Figure 1 As shown, it is carried out in the following steps:

[0029] Step 1: Make a groups of samples, and each group of samples contains A sample, each sample is composed of a powder material mixed with metal and non-metal;

[0030] use Different pressure Respectively The samples of each group are pressed, and the density of each sample in each group after pressing is measured, and the average density of each group of samples is taken to obtain the average density of each group of samples. ;in, represents the i-th pressure, Represents the average density of the i-th group of samples, i∈[1,n].

[0031] Step 2: In the finite element software The sample group Different pressure The pressing process under the condition of ;in, represents the simulated average density of the i-th group of samples, i∈[1,n];

[0032] Step 2.1: Set the model geometry type of the plane entity in the finite element software, and set the material type of the model to plastic deformation material. The plastic deformation material is described using the Shima-Oyane constitutive model, as shown in formula (1):

[0033] (1)

[0034] In formula (1): represents the principal stress; represents hydrostatic pressure; Indicates hydrostatic pressure The degree of influence on porous yielding materials is the relative density In formula (1), F is related to the yield stress of the material matrix. related to, and , where is the relative density The function of is the apparent yield strength of the non-dense body (i.e., powder material), is the yield stress of the dense body (i.e. the material matrix).

[0035] In formula (1) and All relative densities In practical applications, the function is usually expressed as shown in formula (2):

[0036] (2)

[0037] In formula (2): is the Shima-Oyane constitutive model parameter, which is the target parameter optimized by the simplex method. An axisymmetric model of the specimen is constructed, and the model material is defined as the above material.

[0038] Step 2.2: In the initial condition setting interface, create a new relative density initial condition, set the initial density value, and define the initial density attribute to all units. Set the relative density of the axisymmetric model to be the same as the initial density of the experimental compression.

[0039] Step 2.3: Set the boundary conditions of the axisymmetric model. Select the left boundary of the axisymmetric model and set its Y displacement to 0 to limit the Y displacement of the axis of symmetry of the axisymmetric model. Select any point on its symmetry axis to limit the X displacement of the axis of symmetry.

[0040] Step 2.4: According to n different pressures , establish the same pressure-time curve as that in the experimental pressing, so as to establish n unit edge distributed force constraints on the outer boundary of the axisymmetric model;

[0041] Step 2.5: Use n different unit edge distribution force constraints to establish n corresponding working conditions for the axisymmetric model, and solve the axisymmetric model under each working condition. After the solution is completed, the simulation average density corresponding to the n pressures is obtained by reading the result file data. .

[0042] Step 3: Solve the objective function using the simplex method with reflection strategy and obtain:

[0043] Step 3.1: Constitutive model parameters of powder material is a set of decision vectors X, so the objective function is constructed using formula (3) :

[0044] (3)

[0045] Step 3.2: Use the Nelder-Mead optimization algorithm to optimize the objective function Solve and optimize the initial vector to , The constitutive model parameters of the metal powder in the mixed powder are obtained, and the optimal decision vector X is finally optimized. * These are the optimal constitutive model parameters for powder materials.

[0046] In the specific implementation, 15 sizes are made. The material is 40.0% aluminum powder, 55.5% ammonium sulfate, 4.50% binder, and the initial density is 0.6. The pellets are then divided into 5 groups and the 5 groups of pellets are used respectively. After compression, the density is measured, and the average density of each group of medicine columns is obtained. , the experimental pressure density table is shown in Table 1:

[0047] Table 1 Experimental pressure density table

[0048]

[0049] Use Marc software to set the analysis problem type to plane entity and draw a symmetrical cross-section model of the cylindrical column in the modeling interface. rectangle and mesh the model.

[0050] Then the initial conditions are set, and the initial density of the powder metal and non-metal mixed powder material model is set to 0.6. In the boundary condition setting stage, 5 sets of pressure Establish different boundary conditions, and use boundary conditions of different pressures to establish corresponding analysis conditions, and then establish corresponding analysis tasks. After the settings are completed, you can submit the work in sequence for solution.

[0051] By referring to the existing data, the Shima-Oyane constitutive model parameters of aluminum powder material are obtained as follows: , that is, the initial vector The pressure density table before optimization obtained by using the Shima-Oyane constitutive model parameters of aluminum powder material as simulation parameters is shown in Table 2:

[0052] Table 2 Pressure density table before optimization

[0053]

[0054] The objective function in this embodiment is shown in formula (4):

[0055] (4)

[0056] The Nelder-Mead algorithm is used to optimize the parameters. The initial vector is , so that the difference between the density obtained by simulation and the experimental density gradually decreases, that is, the optimal constitutive model parameters of powder materials are obtained. The optimized pressure density table obtained using the optimal powder material constitutive parameters is shown in Table 3:

[0057] Table 3 Optimized pressure density table

[0058]

[0059] Figure 2 The comparison results of the compaction test density, the simulation density before optimization, and the density obtained by simulating with the optimal constitutive model parameters are shown. The dashed line represents the density obtained by simulating with the parameters before optimization, the solid line represents the density obtained by simulating with the optimal constitutive model parameters after optimization, and the black dotted line represents the density measured by the compaction test. Figure 2 It can be seen that the matching degree between the simulation results and the experimental data is significantly improved after optimization, which verifies the effectiveness of the optimization method of the present invention in the field of powder pressing.

[0060] In this embodiment, an electronic device includes a memory and a processor, wherein the memory is used to store a program that supports the processor to execute the above method, and the processor is configured to execute the program stored in the memory.

[0061] In this embodiment, a computer-readable storage medium stores a computer program on the computer-readable storage medium, and the computer program executes the steps of the above method when executed by a processor.

Claims

1. A method for obtaining parameters of the Shima-Oyane constitutive model of metal and non-metal mixed powders, characterized in that: The steps include: Step 1: Make a groups of samples, and each group of samples contains A sample, each sample is composed of a powder material mixed with metal and non-metal; use Different pressure Respectively The samples of each group are pressed, and the density of each sample in each group after pressing is measured, and the average density of each group of samples is taken to obtain the average density of each group of samples. ;in, represents the i-th pressure, represents the average density of the i-th group of samples, i∈[1,n]; Step 2: In the finite element software The sample group Different pressure The pressing process under the condition of ;in, represents the simulated average density of the i-th group of samples, i∈[1,n]; Step 2.1: Set the model geometry type of the plane entity in the finite element software, and set the material type of the model to plastic deformation material. The plastic deformation material is described using the Shima-Oyane constitutive model, which has 8 material parameters: ; thus establishing Axisymmetric model of group specimens; Step 2.2: Set the relative density of the axisymmetric model to be the same as the initial density of the experimental pressing; Step 2.3: Set the boundary conditions of the axisymmetric model to limit the displacement of the axis of symmetry of the axisymmetric model in the Y direction, and select any point on its axis of symmetry to limit the displacement of the axis of symmetry in the X direction; Step 2.4: According to n different pressures , establish the same pressure-time curve as that in the experimental pressing, so as to establish n unit edge distributed force constraints on the outer boundary of the axisymmetric model; Step 2.5: Use n different unit edge distribution force constraints to establish n corresponding working conditions for the axisymmetric model, and solve the axisymmetric model under each working condition to obtain the simulation average density corresponding to the n pressures. ; Step 3: Solve the objective function using the simplex method with reflection strategy and obtain: Step 3.1: Constitutive model parameters of powder material is a set of decision vectors X, so the objective function is constructed using formula (3) : (3) Step 3.2: Use the Nelder-Mead optimization algorithm to optimize the objective function Solve and find the initial vector , The optimal decision vector X is obtained by optimizing the constitutive model parameters of the metal powder in the mixed powder. * These are the optimal constitutive model parameters for powder materials.

2. An electronic device, comprising a memory and a processor, characterized in that: The memory is used to store a program that supports the processor to execute the parameter acquisition method according to claim 1, and the processor is configured to execute the program stored in the memory.

3. 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 parameter acquisition method according to claim 1 are executed.

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