A residual stress simulation optimization design method for the entire process of rocket tank manufacturing

Abstract

The present invention provides a method for simulating and optimizing residual stress in the entire manufacturing process of a rocket tank, comprising the following steps: scaling the bottom and barrel structures of the rocket tank in equal proportions and formulating forming process parameters; assigning material properties to the geometric model, setting the boundary conditions and mesh size of the first process, and extracting stress and deformation data through a custom function solution; mapping the stress and deformation data of the first process to the model of the second process by calculating node distances, completing the simulation of the subsequent forming process of the bottom and barrel components; continuously transmitting the forming stress to simulate the stir friction joining process of the bottom and barrel, and finally obtaining the overall residual stress and deformation of the rocket tank. By using the method of the present invention, the residual stress of the entire manufacturing process of the rocket tank can be accurately solved in time series, achieving the purpose of accurately predicting and regulating the residual stress and deformation of the rocket tank.

Description

Technical Field

[0001] The present invention relates to the field of mechanical manufacturing and processing, and in particular to a method for simulating and optimizing residual stress in the entire manufacturing process of a rocket tank. Background Art

[0002] The development of space launch vehicles reflects a country's overall strength in aerospace technology and is a key indicator of its ability to enter outer space. As the primary load-bearing structure of a space launch vehicle, the propellant rocket tank is a critical component affecting its safety and reliability, accounting for 60% of the rocket's total mass. The lightweight design and high-quality manufacturing of this structure strongly support the development of space launch vehicle technology.

[0003] The overall manufacturing process of rocket tanks is complex, resulting in large deformations, high residual stresses, and a strong redistribution effect. The superposition of residual stresses caused by different processes significantly impacts the evolution of residual stress within the tank structure. Accurately understanding the distribution of residual stresses within rocket tanks during manufacturing and the interaction mechanisms between residual stresses in each process is a crucial prerequisite for improving the overall reliability of the tank and the foundation for optimizing its process parameters. Using current technology, traditional experimental methods to accurately measure the residual stress and deformation distribution of rocket tank components in real time is time-consuming, labor-intensive, and costly.

[0004] With the rapid development of computer simulation technology, there have been some cases of using computer numerical simulation calculation methods to calculate the residual stress and deformation of complex structural parts during the forming process. For example, CN113673055A discloses a modeling and analysis method for calculating the residual stress of a marine diesel fuselage using stress genetics and processing stress coupling; CN116090306A discloses a finite element modeling method for stress and deformation of a connecting rod coupled with multiple processes. The above cases are all calculated under the premise of the same model or the same model grid size. It is difficult to meet the data transfer requirements of models with different grid sizes and densities, which hinders the simulation of residual stress in multiple processes of complex structure manufacturing and is not conducive to stress transfer analysis. Therefore, it is urgent to develop a data transfer method suitable for different grid sizes. Based on this method, the residual stress and deformation calculation of the rocket tank manufacturing process is carried out. By dynamically calculating the stress and deformation of different parameters to continuously optimize the forming parameters, it is of great significance to realize the simulation optimization and control of the rocket tank stress and deformation and reduce the residual stress of the overall structure. Summary of the Invention

[0005] The purpose of the present invention is to design a residual stress simulation optimization design method for the entire process of rocket tank manufacturing.

[0006] The main problems to be solved by the present invention are: the traditional experimental method of accurately measuring the residual stress of the entire rocket tank manufacturing process is costly, time-consuming and labor-intensive; during simulation calculations, the grids between different process models are non-coherent, and the model data transmission is relatively difficult, making it difficult to fully and comprehensively consider the residual stress size under the entire manufacturing process. At present, there are difficulties in the time-series calculation of the residual stress of multiple processes in the rocket tank manufacturing process.

[0007] The present invention relates to a method for optimizing the residual stress simulation of the entire process of rocket tank manufacturing. The specific contents are as follows:

[0008] (1) Based on the simplified model of the rocket tank structure, the tank bottom and barrel section components were studied in detail. After scaling them up and down, they were imported into the finite element software to develop the forming processes for the tank bottom and barrel section components respectively.

[0009] (2) Set the material properties and boundary conditions for the first forming process model of the box bottom and barrel section to calculate the stress field and deformation results, and further extract the stress and deformation data of the nodes of the first process model;

[0010] (3) Data mapping is performed based on the differences in mesh size and type between different process models. The weighted average calculation of node distance is used to realize the stress and deformation transfer between different models. The influence of the stress of the previous process on the forming of the current process is considered and used as the initial condition of the current process model. This step is repeated until the forming simulation of the box bottom and barrel section components is completed respectively.

[0011] (4) For the friction stir welding process of the combined forming of the tank bottom and barrel section, the forming stress and deformation data of the components are transferred respectively, and the final residual stress and deformation distribution results of the rocket tank manufacturing are calculated.

[0012] Preferably, step (1) takes into account the structural characteristics of the rocket tank and the main research objects, ignores structures that have little impact on the residual stress of the rocket tank (such as fork rings, short shells, etc.) and unnecessary processes (such as vibration and bumps during transportation), and the simplified rocket tank structure includes 2 integral box bottoms and 4 long cylindrical sections.

[0013] Preferably, in step (1), the forming processes of the bottom and barrel section of the rocket tank are formulated as follows: the bottom of the tank includes primary spinning, stress relief annealing, secondary spinning, and stress relief annealing processes; the barrel section includes rolling forming, rough milling of the inner wall, fine milling of the inner wall, and stir friction welding processes; and the two are finally connected and formed by stir friction welding.

[0014] Preferably, step (2) is to simulate and calculate the first forming process of the box bottom and the barrel section, set the material properties and boundary conditions for the blank, divide the geometric model into grids after applying the constraint load and set the grid properties to C3D10MT, and traverse and read the grid node numbers in the model result file .odb after the calculation of the first forming process is completed, and extract the model node stress and deformation data, including the following steps: reading the component forming process result file .odb; setting the grid numbers (A1, A2...A n ), node number (N1, N2…N n ) to traverse and search and read; according to the extracted grid number A i With node number N i , traverse and search to read the corresponding node stress σ i , deformation δ i Repeat the previous step until there is no traversal interval, and extract the stress and deformation results.

[0015] Preferably, step (3) is the stress and deformation transfer between different models, comprising the following steps: reading the current process model and the previous process model .inp file of the component; finding the corresponding position point M' of the grid node M of the current process model .inp file in the previous process model .inp; establishing a local coordinate system at point M', and calculating the distance d from M' to each quadrant node N1, N2, N3, N4 i (If the model is two-dimensional, the number of nodes i is 4; if the model is three-dimensional, the number of nodes i is 8), the distance d from M' to each node N1, N2, N3, N4 i for (i=1, 2, 3, 4) where quadrant node N i The coordinates of M' are (N i (x), N i (y)), (M'(x), M'(y)); calculate the distance ratio coefficient k between each node and M' i , whose expression is (i=1,2,3,4); according to the distance proportional coefficient k i , calculate the stress σ of node M' mapped to node M M , deformation δ M , whose expression is By performing operations on the .inp grid nodes of the current process model in sequence, the stress and deformation transfer of the previous process can be completed, and then the residual stress calculation of the current process can be performed; the forming of the rocket tank bottom and barrel section components are simulated respectively to obtain the forming stress and deformation data of the components.

[0016] Preferably, step (4) is to calculate the residual stress field and deformation distribution of the stir friction connection forming of the box bottom and barrel section components after they are formed separately. After the calculation of each process is completed, the methods of steps (2) and (3) are used to complete the stress and deformation mapping, thereby obtaining the residual stress and deformation results of the entire rocket tank manufacturing process.

[0017] Beneficial effects of the present invention: Compared with the prior art, the present invention comprehensively considers the residual stress and deformation distribution of the entire process of rocket tank manufacturing, and realizes data transfer between models of different grid sizes. By decomposing the process of tank structure, component forming process simulation, model node data extraction and mapping, and overall part forming simulation, the residual stress calculated in the previous process is mapped to the current process model through node distance weighted calculation, and the residual stress and deformation results of the final rocket tank forming are outputted. The optimal process parameters are screened through simulation calculation to accurately control the residual stress and deformation of the rocket tank. In addition, the present invention proposes a node distance weighted calculation method for data transfer between different models, which is simple, feasible, and easy to develop. Different process models can be rewritten as needed, thereby improving adaptability to complex processes and facilitating calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the simplified structure of the rocket tank and the forming process of different components described in the present invention.

[0019] Figure 2 This is a flow chart for residual stress calculation in the entire process of rocket tank manufacturing described in the present invention.

[0020] Figure 3 This is a flow chart for extracting residual stress and deformation data of nodes in the model of the rolling bending process of the rocket tank barrel section structure described in the present invention.

[0021] Figure 4 It is a schematic diagram of mapping the node data of the rolling bending model file of the rocket tank barrel section structure described in the present invention to the rough milling model file.

[0022] Figure 5 The present invention is a flowchart of a rocket tank barrel section structure rolling bending model file that uses a node distance weighted method to calculate stress and deformation and maps the result to a rough milling model file. DETAILED DESCRIPTION

[0023] In order to facilitate understanding by those skilled in the art, the present invention will be further described in detail below with reference to the accompanying drawings. The contents mentioned in the embodiment are not intended to limit the present invention.

[0024] Reference Figure 1As shown in the figure, the rocket tank mainly consists of upper and lower tank bottoms and a central barrel section. The forming processes of the two structures vary significantly. The tank bottom is formed by step-by-step spinning from a circular blank. After the first spinning process, stress relief annealing is performed to reduce internal residual stress. Then, secondary spinning and stress relief annealing are performed to further eliminate residual stress generated during metal plastic forming. The barrel section is formed by first roll-bending a square blank and then welding it. After the roll-bending process, the inner wall is rough-milled to remove most of the sheet metal to machine the internal rib structure. The internal ribs are then fine-milled to achieve the required forming accuracy. The barrel section is then spliced ​​together using stir friction welding. The barrel section and the tank bottom are then connected by stir friction welding to form the rocket tank.

[0025] Reference Figure 2 The figure shows the residual stress and deformation simulation calculation of the entire rocket tank manufacturing process, including:

[0026] (1) Establish a geometric model of the rocket tank structure. Considering the model size and solution efficiency, the actual size is scaled proportionally to improve the calculation speed. The blank is designed based on the scaled size and imported into the finite element software;

[0027] (2) Formulate the forming process parameters for the bottom and barrel of the rocket tank. For the bottom of the tank, design the simulation of the first spinning, stress relief annealing, second spinning, and stress relief annealing process; for the barrel, design the simulation of the rolling, rough milling of the inner wall, fine milling of the inner wall, and stir friction welding process; finally, simulate the stir friction welding process for both, ignoring some other processes such as deburring the bottom of the tank and hammering the barrel, and carry out the simulation of the main processes;

[0028] (3) Assign material properties to the model. Call the material properties in the material library and load them into the blank, mainly including physical quantities such as density, elastic modulus, thermal expansion coefficient, thermal conductivity, Poisson's ratio, etc. For physical quantities that change with temperature, set corresponding functions to accurately describe the physical quantity values;

[0029] (4) Apply force-displacement boundary conditions. For the primary and secondary spinning processes of the box bottom, the roller speed is set to 2 rad / s, the spindle speed is set to 3 rad / s, and the stress relief annealing process is set to a heating temperature of 260°C, a holding time of 1.5 h, and air cooling. The force-displacement boundary conditions mainly impose rigid constraints on the edge of the workpiece. Three points that are not in the same plane are selected, and each point constrains the displacement in one direction.

[0030] (5) Solve the residual stress and deformation of the first process of the box bottom. Set the mesh attribute to C3D10MT, check the model and submit the calculation, and output the residual stress and deformation distribution results after the box bottom is spun once;

[0031] (6) Extract the residual stress and deformation of the first process of the box bottom. Select the box bottom spinning result file .odb and read it. Use Python language to write a custom program to extract the grid numbers (A1, A2...A n ), node number (N1, N2…N n ) and the corresponding nodal stress σ i , deformation δ i Perform traversal reading and output as .vtk format file;

[0032] (7) Transfer the residual stress and deformation of the first process of the box bottom to the second process model. Open the .vtk format file and the box bottom stress relief annealing .inp file output in step (6), write a custom node distance weighted calculation method Python program, map the node stress and deformation in the .vtk file to the stress relief annealing .inp file, realize the loading of the initial conditions, and thus complete the stress transfer from the first process to the second process;

[0033] (8) After completing the calculation of the second process of the box bottom, repeat the calculation of the third and fourth processes. Establish the secondary spinning and stress relief annealing process models of the box bottom respectively, and realize the loading of initial residual stress and deformation between different models through non-coherent node data mapping, and then complete the simulation;

[0034] (9) Perform calculations in steps (5) to (8) on the barrel section. After completing the forming simulation of the box bottom, formulate the corresponding forming process for the barrel section structure, establish the model calculation results, complete the model data mapping, and obtain the final forming residual stress and deformation results of the barrel section structure;

[0035] (10) Friction stir welding of tank bottom and barrel section. Based on the calculation results of the components obtained in steps (5) to (8) and (9), a friction stir welding model is established for it, and the boundary conditions and residual stress and deformation results of the components are loaded. Finally, the overall stress and deformation of the rocket tank are calculated.

[0036] Reference Figure 3 The figure shows the process of extracting mesh, node number, stress and deformation from the result file .odb after the cylinder section is rolled. The box bottom one-time spinning result file .odb is selected and read. A custom program is written in Python to extract the mesh number (A1, A2...A n ), node number (N1, N2…N n ) and the corresponding nodal stress σ i , deformation δ i Perform traversal reading and output as .vtk format file.

[0037] Reference Figure 4 、 Figure 5The figure shows a schematic diagram of mapping the stress and deformation results calculated by the barrel section rolling model to the rough milling model. Since different models have different local encryption areas and different grid sizes, it is necessary to solve the problem of data transfer between different models if stress simulation of the entire manufacturing process is to be realized. The method proposed by the present invention is: find the corresponding position point M of the rough milling model node M in the rolling model, establish a local coordinate system at the position point M to calculate the distance to the nearest point in each quadrant. i=1, 2, 3, 4, calculate the distance ratio coefficient k between each node and M' i , whose expression is i=1,2,3,4;according to the distance proportional coefficient k i Calculate the stress σ of the output node M' mapped to the node M M , deformation δ M , whose expression is

[0038] It should be understood that the above-mentioned embodiments are merely illustrative and non-restrictive. It is obvious that those skilled in the art can easily make various modifications to this example. Therefore, the present invention is not limited to the examples herein. As long as they are within the scope of the essential spirit of the present invention, various simple modifications or replacements of the above-mentioned details will be included in the scope of the claims of the present invention.

Claims

1. A method for residual stress simulation optimization design of the whole process of rocket tank manufacturing, characterized by: The steps are as follows: (1) Based on the simplified model of the rocket tank structure, the tank bottom and barrel section components were studied in detail. After scaling them up and down, they were imported into the finite element software to develop the forming processes for the tank bottom and barrel section components respectively. (2) Set the material properties and boundary conditions for the first forming process model of the box bottom and barrel section to calculate the stress field and deformation results, and further extract the stress and deformation data of the nodes of the first process model; (3) Data mapping is performed based on the differences in mesh size and type between different process models. The weighted average calculation of node distance is used to realize the stress and deformation transfer between different models. The influence of the stress of the previous process on the forming of the current process is considered and used as the initial condition of the current process model. This step is repeated until the forming simulation of the box bottom and barrel section components is completed respectively. (4) For the friction stir welding process of the combined forming of the tank bottom and barrel section, the forming stress and deformation data of the components are respectively transferred to calculate the final residual stress and deformation distribution results of the rocket tank manufacturing; Extracting the model node stress and deformation data in the above step (2) includes the following steps: reading the component forming process result file .odb; The grid numbers of the .odb file (A1, A2...A n ), node number (N1, N2…N n ) to traverse and search and read; according to the extracted grid number A i With node number N i , traverse and search to read the corresponding node stress σ i , deformation δ i Repeat the previous step until there is no traversal interval, and extract the stress and deformation results; The stress and deformation mapping between different models in the above step (3) includes the following steps: reading the current process model and the previous process model .inp file of the component; finding the corresponding position point M' of the grid node M of the current process model .inp file in the previous process model .inp; Establish a local coordinate system at point M' and calculate the distance d from M' to each quadrant node N1, N2, N3, N4 i (If the model is two-dimensional, the number of nodes i is 4, if the model is three-dimensional, the number of nodes i is 8), M' is the distance d from each node N1, N2, N3, N4 i for (i=1, 2, 3, 4) where quadrant node N i The coordinates of M' are (N i (x), N i (y)), (M'(x), M'(y)); calculate the distance ratio coefficient k between each node and M' i , whose expression is (i=1,2,3,4); according to the distance proportional coefficient k i , calculate the stress σ of node M' mapped to node M M , deformation δ M , whose expression is By performing operations on the .inp grid nodes of the current process model in sequence, the stress and deformation mapping of the previous process can be completed, and then the residual stress calculation of the current process can be performed; the forming of the rocket tank bottom and barrel section components are simulated respectively to obtain the forming stress and deformation data of the components.

2. A rocket tank manufacturing full-process residual stress simulation optimization design method according to claim 1, characterized in that: The above step (1) takes into account the structural characteristics of the rocket tank and the main research objects, ignoring the structure that has little impact on the residual stress of the rocket tank and unnecessary vibration and bumpy processes during transportation. The simplified rocket tank structure includes 2 integral box bottoms and 4 long cylindrical sections.

3. The method for residual stress simulation optimization design of the whole process of rocket tank manufacturing according to claim 1 is characterized in that: In the above step (1), the forming processes of the bottom and barrel of the rocket tank are formulated as follows: the bottom of the tank includes the first spinning, stress relief annealing, second spinning, and stress relief annealing processes; the barrel includes the rolling forming, rough milling of the inner wall, fine milling of the inner wall, and stir friction welding processes; the two are finally connected and formed by stir friction welding.

4. A rocket tank manufacturing full-process residual stress simulation optimization design method according to claim 1, characterized in that: The above step (2) is to simulate the first forming process of the box bottom and barrel section, set the material properties and boundary conditions for the blank, apply the constraint load, divide the geometric model into grids and set the grid properties to C3D10MT. After the calculation of the first forming process is completed, the grid node numbers in the model result file .odb are traversed and the node stress σ is extracted. i , deformation δ i .

5. The method for residual stress simulation optimization design of the whole process of rocket tank manufacturing according to claim 1, characterized in that: The above step (4) is to calculate the residual stress field and deformation distribution of the stir friction joining of the box bottom and barrel section components after they are formed separately. After the calculation of each process is completed, the stress and deformation mapping is completed using the methods of step (2) and step (3), thereby obtaining the residual stress and deformation results of the entire process of rocket tank manufacturing. By pre-simulation calculation and screening of the optimal process parameters, the residual stress simulation optimization design is realized, which greatly reduces the experimental cost.

6. A rocket tank manufacturing full-process residual stress simulation optimization design method as claimed in claim 1, characterized in that: The finite element simulation software used is ABAQUS, and the analysis modes include dynamics-explicit and dynamics-implicit combined analysis.

Images