A method for setting rack boundary conditions based on ANSYS-APDL language

Abstract

This invention relates to a method for setting frame boundary conditions based on ANSYS-APDL language, belonging to the field of structural design simulation analysis. Based on previous static test results of the frame, the radial and tangential displacements of the fixed end of the frame under static test conditions are statistically determined. An ANSYS-APDL finite element model of the frame is established, and the fixed end of the frame is constrained by fixed fixtures. The support reactions at the fixed support points are calculated. The radial and tangential stiffness of the fixed end of the frame under static test conditions are calculated. Spring elements are added radially and tangentially at each constraint point of the frame's ANSYS-APDL finite element model, with spring coefficients equal to the calculated radial and tangential stiffness, to achieve elastic constraints. Simultaneously, the constraint points are axially fixed, thus completing the setting of the frame boundary conditions. This invention improves the accuracy of frame simulation calculations, making the calculation results closer to the experimental results.

Description

Technical Field

[0001] This invention belongs to the field of structural design simulation analysis, and relates to a method for setting frame boundary conditions based on ANSYS-APDL language. Background Technology

[0002] As the force-transmitting and connecting element of the rocket engine, the load-bearing capacity and structural stiffness of the hydrogen-oxygen engine frame are crucial design parameters. To ensure successful design on the first attempt and avoid repeated design iterations, finite element simulation analysis must be performed during the design process to verify the correctness of the design.

[0003] The more accurate the simulation results, the closer the actual product's test results will be to the calculated results. The setting of the calculation boundary conditions directly affects the accuracy of the simulation calculation; selecting appropriate boundary conditions can ensure the accuracy of the calculation. Currently, relevant literature describes two methods for setting frame boundary conditions: one is fixed-support constraint, which has low calculation accuracy, large deviations, and cannot obtain satisfactory results. Subsequent design modifications to the frame may be necessary after static testing. Another method is to establish a finite element model of the components connected to the frame (tank bottom) together with the frame for joint simulation analysis. While this can obtain more accurate results, the calculation model is very large, consuming computational resources and time, and delaying the development schedule. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a rack boundary condition setting method based on ANSYS-APDL language to improve the accuracy of rack simulation calculation and make the calculation results closer to the experimental results.

[0005] The solution of the present invention is:

[0006] In a first aspect, the present invention provides a method for setting rack boundary conditions based on ANSYS-APDL language, including:

[0007] Based on previous static test results of the frame, the radial and tangential displacements of the fixed end of the frame under static test conditions were statistically analyzed.

[0008] Establish an ANSYS-APDL finite element model of the frame, with fixed support constraints at the fixed end of the frame, and calculate the support reaction forces at the fixed support points.

[0009] Calculate the radial and tangential stiffness of the fixed end of the frame under static test conditions;

[0010] Spring elements are added radially and tangentially to each constraint point in the ANSYS-APDL finite element model of the frame, with spring coefficients equal to the calculated radial and tangential stiffness, to achieve elastic constraints; at the same time, the constraint points are axially fixed, thus completing the frame boundary condition setting.

[0011] Preferably, the radial displacement of the fixed end is obtained from the results of N previous static tests of the frame, and the average value is taken as the radial displacement of the fixed end of the frame under static test conditions.

[0012] Preferably, the tangential displacement of the fixed end is obtained from the results of N previous static tests of the frame, and the average value is the tangential displacement of the fixed end of the frame under static test conditions.

[0013] Preferably, under static test conditions, the radial stiffness of the fixed end of the frame = the support reaction force at the fixed support point / the radial displacement of the fixed end of the frame.

[0014] Preferably, under static test conditions, the tangential stiffness of the fixed end of the frame = the support reaction force at the fixed support point / the tangential displacement of the fixed end of the frame.

[0015] Preferably, after the rack boundary conditions are set, loads are applied and rack simulation calculations are performed.

[0016] In a second aspect, the present invention provides a terminal device, comprising:

[0017] Memory, used to store at least one instruction executed by a processor;

[0018] A processor for executing instructions stored in memory to implement the method described in the first aspect above.

[0019] Thirdly, the present invention provides a computer-readable storage medium storing computer instructions that, when executed on a computer, cause the computer to perform the method described in the first aspect.

[0020] The advantages of this invention compared to existing technologies are as follows: The radial and tangential displacements measured in previous static tests of the frame are statistically analyzed. The support reactions calculated using the ANSYS-APDL finite element model of the frame are divided by the statistical average values ​​of the radial and tangential displacements to obtain the boundary stiffness of the static test—that is, the elastic boundary. The elastic boundary replaces the fixed boundary: COMBIN14 spring elements are added to the radial and tangential directions of the constraint points in the ANSYS-APDL finite element model, with spring coefficients equal to the calculated radial and tangential stiffness. Simultaneously, a fixed constraint is applied to the axial direction of the constraint points. The ANSYS-APDL finite element model of the frame using elastic boundaries has boundary conditions closer to reality. Therefore, the calculation results are closer to the experimental results.

[0021] The model of this invention is simple, saves resources and time, improves the accuracy of rack simulation calculations, and makes the calculation results basically consistent with the actual situation. It realizes the refinement and one-time success of rack product design and avoids repeated design adjustments. Attached Figure Description

[0022] Figure 1 This is a finite element model with elastically constrained boundaries;

[0023] Figure 2 The results are from a finite element analysis with elastically constrained boundaries (equivalent stress). Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] The present invention provides a boundary condition setting method for simulating real elastic boundary conditions using spring elements, comprising the following steps:

[0026] (1) Based on previous static test results of the frame, the radial and tangential displacements of the fixed end of the frame under static test conditions were statistically determined.

[0027] Based on the results of N previous static tests on the frame, N radial displacements of the fixed ends are obtained. The average value is then calculated to obtain the radial displacement of the fixed ends of the frame under static test conditions. Similarly, based on the results of N previous static tests on the frame, N tangential displacements of the fixed ends are obtained. The average value is then calculated to obtain the tangential displacement of the fixed ends of the frame under static test conditions.

[0028] (2) Establish the ANSYS-APDL finite element model of the frame, fix the fixed end of the frame with fixed support constraints, and solve to calculate the support reaction force at the fixed support point.

[0029] (3) Radial stiffness and tangential stiffness of the fixed end of the computer frame in static test.

[0030] Under static test conditions, the radial stiffness of the fixed end of the frame = the support reaction force at the fixed support point / the radial displacement of the fixed end of the frame. Under static test conditions, the tangential stiffness of the fixed end of the frame = the support reaction force at the fixed support point / the tangential displacement of the fixed end of the frame.

[0031] (4) Add spring elements COMBIN14 to the radial and tangential directions of the constraint points in the ANSYS-APDL finite element model of the frame, with spring coefficients equal to the calculated radial and tangential stiffness, to achieve elastic constraints. Simultaneously, the constraint points are axially fixed. This completes the frame boundary condition setting.

[0032] Then rack simulation calculations can be performed.

[0033] The present invention also provides a terminal device, comprising: a memory for storing at least one instruction executed by a processor; and a processor for executing the instructions stored in the memory to implement the above method.

[0034] The present invention also provides a computer-readable storage medium storing computer instructions that, when executed on a computer, cause the computer to perform the above-described method.

[0035] Example:

[0036] (1) Based on previous static test results of the frame, the radial and tangential displacements of the fixed end of the frame under static test conditions were statistically determined;

[0037] (2) Establish the ANSYS-APDL finite element model of the frame, fix the fixed end of the frame with fixed support constraints, and solve to calculate the support reaction force R at the fixed support point.

[0038] (3) Calculate the radial stiffness and tangential stiffness. Tangential stiffness = support reaction force at the fixed support point / tangential displacement at the fixed end of the frame, radial stiffness = support reaction force at the fixed support point / radial displacement at the fixed end of the frame. The results are shown in Table 1.

[0039] Table 1. Test data and analysis of axial stiffness of the engine twin-frame.

[0040]

[0041] (4) Add radial and tangential spring elements COMBIN14 to the four constraint points at the fixed end of the frame, with spring coefficients equal to the calculated radial and tangential stiffness. Simultaneously, fix the constraint points axially to complete the boundary condition settings. The resulting finite element model with elastically constrained boundaries is shown below. Figure 1 As shown.

[0042] (5) Apply the load, run the ANSYS solver, and view the calculation results. For example... Figure 2 The results of the finite element analysis (equivalent stress) are shown.

[0043] The calculated axial displacement of the frame in the above example is 4.14 mm, which is very close to the experimental value of 3.93–4.11 mm. The maximum equivalent stress of 226 MPa is also very close to the experimental value of 240 MPa, indicating that the method of this invention can effectively improve the calculation accuracy of the ANSYS-APDL finite element model.

[0044] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for setting rack boundary conditions based on ANSYS-APDL language, characterized in that, include: Based on previous static test results of the frame, the radial and tangential displacements of the fixed end of the frame under static test conditions were statistically analyzed. Establish an ANSYS-APDL finite element model of the frame, with fixed support constraints at the fixed end of the frame, and calculate the support reaction forces at the fixed support points. Calculate the radial stiffness and tangential stiffness of the fixed end of the frame under static test conditions; Radial stiffness of the fixed end of the frame under static test conditions = support reaction force at the fixed support point / radial displacement of the fixed end of the frame; Tangential stiffness of the fixed end of the frame under static test conditions = support reaction force at the fixed support point / tangential displacement of the fixed end of the frame. Spring elements are added radially and tangentially to each constraint point in the ANSYS-APDL finite element model of the frame, with spring coefficients equal to the calculated radial and tangential stiffness, to achieve elastic constraints; at the same time, the constraint points are axially fixed, thus completing the frame boundary condition setting.

2. The method for setting rack boundary conditions based on ANSYS-APDL language according to claim 1, characterized in that, Based on the results of N previous static tests of the frame, the radial displacements of N fixed ends are obtained. The average value is the radial displacement of the fixed end of the frame under static test conditions.

3. The method for setting rack boundary conditions based on ANSYS-APDL language according to claim 1, characterized in that, Based on the results of N previous static tests of the frame, the tangential displacements of the fixed ends are obtained. The average value is the tangential displacement of the fixed ends of the frame under static test conditions.

4. The method for setting rack boundary conditions based on ANSYS-APDL language according to claim 1, characterized in that, After setting the rack boundary conditions, loads are applied, and rack simulation calculations are performed.

5. A terminal device, characterized in that, include: Memory, used to store at least one instruction executed by a processor; A processor for executing instructions stored in memory to implement the method as described in any one of claims 1-4.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions that, when executed on a computer, cause the computer to perform the method as described in any one of claims 1-4.

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