Dynamic modeling and verification method for foam interlayer common-bottom storage tank

Abstract

According to the dynamic modeling and verification method for the foam interlayer common-bottom storage tank, for interlayer common-bottom of the storage tank, during modeling, a linear elastic three-dimensional entity unit is adopted to simulate a heat insulation interlayer, and an upper bottom and a lower bottom which are arranged on the upper surface and the lower surface of the heat insulation interlayer respectively are simulated by adopting shell units endowed with isotropic material attributes; and the upper surface and the lower surface of the linear elastic three-dimensional entity unit share the same node with the shell unit. The interlayer common-bottom modeling thought can provide an effective model basis for simulating the dynamic characteristics of the liquid on the two sides, and accurate and efficient prediction of the dynamic characteristics of the whole rocket can be achieved. The method can be applied to modeling and verification of a new generation of carrier rockets containing the interlayer common-bottom storage tank.

Description

Technical Field

[0001] The invention belongs to the field of launch vehicles, and in particular relates to a dynamic modeling and verification method for a foam sandwich common bottom tank. Background Art

[0002] Rockets with a common bottom tank configuration have the advantages of a shorter rocket length and a smaller structural mass because there is no intertank section. Therefore, common bottom tanks are widely used in launch vehicles at home and abroad. For common bottom tanks with a large temperature difference between the propellants in the two tanks, the common bottom structure needs to have a certain insulation performance and is usually designed as a sandwich structure.

[0003] The traditional modeling method for this type of sandwich structure is to simplify it into a single-layer shell unit through equivalent or stiffness superposition. The modal test results of a certain type of sandwich common bottom tank show that this method uses a single-layer shell unit to simulate the three-layer structure (foam sandwich structure), which is difficult to provide an effective model basis for the virtual mass method to simulate the dynamic characteristics of the liquid on both sides, resulting in a certain deviation between the simulation results and the test results.

[0004] The sandwich common bottom tank has a complex structure. As the main load-bearing compartment of the rocket body, the accuracy of its finite element model directly affects the prediction accuracy of the whole rocket dynamic characteristics. Therefore, it is necessary to carry out compartment-level modal tests and model correction method research on the sandwich common bottom tank. Summary of the invention

[0005] The purpose of the present invention is to provide a foam sandwich common bottom tank dynamics modeling and verification method to solve the problem that there is a certain deviation between the simulation results of the existing modeling method and the actual dynamic characteristics.

[0006] In order to achieve the above-mentioned purpose, the present invention provides a dynamic modeling and verification method for a foam sandwich common bottom tank. For the sandwich common bottom of the tank, linear elastic three-dimensional solid units are used to simulate the insulating interlayer during modeling, and the upper bottom and lower bottom respectively arranged on the upper and lower surfaces of the insulating interlayer are simulated by shell units with isotropic material properties, and the upper and lower surfaces of the linear elastic three-dimensional solid units share nodes with the shell units.

[0007] The dynamic modeling and verification method of the foam sandwich common bottom tank comprises: step 1, simplifying the digital prototype of the foam sandwich common bottom tank, and dividing the tank structure into a load-bearing structure and a non-load-bearing structure according to its dynamic characteristics; step 2, geometrically processing the load-bearing structure to obtain a load-bearing structure geometric model of the tank; step 3, performing three-dimensional finite element meshing on the load-bearing structure geometric model of the tank, and assigning corresponding attributes, and at the same time modeling the non-load-bearing structure in the form of additional mass, thereby obtaining a three-dimensional finite element model of the foam sandwich common bottom tank; step 4, obtaining a modal test result of the foam sandwich common bottom tank through a modal test; step 5, simulating the modal test boundary, performing modal analysis based on the three-dimensional finite element model of the foam sandwich common bottom tank, and obtaining a modal simulation result; step 6, performing a correlation analysis on the modal test result obtained in step 4 and the modal simulation result obtained in step 5, and completing the model verification.

[0008] The above-mentioned foam sandwich common bottom tank dynamic modeling and verification method, wherein, in the step 1, according to the dynamic characteristics of the foam sandwich common bottom tank, the load-bearing structures are determined to be the front short shell, the cylinder section, the rear short shell, the front bottom, the sandwich common bottom, and the rear bottom, and the non-load-bearing structures are the instruments and equipment and their brackets, cables, ducts, anti-sway plates, and standard parts.

[0009] The above-mentioned foam sandwich common bottom tank dynamic modeling and verification method, wherein, in said step 2, the geometric processing principle is: do not change the structural dynamic characteristics; the geometric processing tools include: CAD software and finite element pre-processing software; the geometric processing work includes: removing chamfers and bolt holes, drawing the middle surface of the wall panel and the bottom, dividing the area according to the thickness of the wall panel and the bottom, and retaining hard lines according to the reinforcement position.

[0010] The above-mentioned dynamic modeling and verification method of the foam sandwich common bottom tank, wherein, in the step 3, the meshing principle is: the mesh scale can fully reflect the dynamic characteristics of the relevant structure and realize the efficient calculation of the modal; the meshing tool is: finite element pre-processing software; the meshing method is: using shell units with isotropic material properties to simulate the tank wall panels without insulation coating layer and the bottom without insulation coating layer, using laminated composite material units to simulate the tank wall panels with insulation coating layer and the bottom with insulation coating layer, using beam units with isotropic material properties to simulate the reinforcement on the wall panels, using linear elastic three-dimensional solid units to simulate the insulation interlayer, the upper and lower surfaces of the linear elastic three-dimensional solid units share nodes with the shell units, the mesh is assigned with the properties of the corresponding structure, and the non-load-bearing structure is modeled in the form of additional mass to obtain a three-dimensional finite element model of the foam sandwich common bottom tank.

[0011] The above-mentioned foam sandwich common bottom tank dynamic modeling and verification method, wherein the three-dimensional finite element model of the foam sandwich common bottom tank obtained in step 3 can be used for the dynamic analysis of the entire arrow structure.

[0012] The above-mentioned foam sandwich common bottom tank dynamic modeling and verification method, wherein, in order to be able to carry out targeted model verification of the insulating interlayer and the insulating coating layer, the modal test of step 4 and the modal analysis of step 5 should obtain the corresponding order modal parameters reflecting the local vibration of the three-layer structure of the sandwich common bottom, the tank wall panel with the insulating coating layer and the bottom with the insulating coating layer, wherein the modal parameters include frequency and vibration shape.

[0013] In the above-mentioned method for dynamic modeling and verification of the foam sandwich common bottom tank, in said step 5, the modal analysis tool adopts finite element analysis software.

[0014] In the above-mentioned method for dynamic modeling and verification of the foam sandwich common bottom tank, in said step 6, finite element model verification software is used to perform correlation analysis.

[0015] In the above-mentioned foam sandwich common bottom tank dynamics modeling and verification method, in said step 6, the correlation analysis includes frequency deviation calculation and vibration mode MAC value calculation.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are:

[0017] The method for dynamic modeling and verification of a foam sandwich common bottom tank proposed in the present invention can be actually applied to the three-dimensional dynamic modeling and verification of related structures in the field of launch vehicles. The dynamic model obtained by this method can be used for the dynamic analysis of the entire rocket structure to achieve accurate prediction of the dynamic characteristics of the entire rocket. The sandwich common bottom modeling idea in this method can provide an effective model basis for simulating the dynamic characteristics of liquid on both sides, improve the accuracy of dynamic simulation, and effectively solve the technical problem of lack of dynamic modeling and verification method for foam sandwich common bottom tank in this field. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The dynamic modeling and verification method of the foam sandwich common bottom tank of the present invention is given by the following examples and drawings.

[0019] Figure 1 This is a flow chart of the dynamic modeling and verification method of the foam sandwich common bottom tank according to an embodiment of the present invention.

[0020] Figure 2 It is a schematic diagram of a three-dimensional finite element model of a foam sandwich common bottom storage tank in an embodiment of the present invention.

[0021] Figure 3 It is a breathing order vibration mode matching diagram of the oxygen box barrel section in the correlation analysis between the modal test results and the modal simulation results in the embodiment of the present invention.

[0022] Figure 4 Schematic diagram of the three-layer structure of the common bottom storage tank.

[0023] Figure 5Schematic diagram of the three-layer structure in the three-dimensional finite element model of the foam sandwich common bottom tank. DETAILED DESCRIPTION

[0024] The following will be combined Figure 1 to Figure 5 The dynamic modeling and verification method of the foam sandwich common bottom tank of the present invention are further described in detail.

[0025] The dynamic modeling of a sandwich common bottom tank of a new generation of domestic launch vehicle was carried out, and the model verification was completed based on the modal test results of the compartment. The flow diagram is shown in the figure. Figure 1 As shown, the specific process is:

[0026] Step 1: Simplify the digital prototype of the foam sandwich common bottom tank, and divide the tank structure into a load-bearing structure and a non-load-bearing structure according to its dynamic characteristics;

[0027] According to the dynamic characteristics of the foam sandwich common bottom tank, the load-bearing structure is determined to be the front short shell, cylinder section (with insulation coating), rear short shell, front bottom, sandwich common bottom (i.e. three-layer structure), and rear bottom. The non-load-bearing structure is the instruments and equipment and their brackets, cables, conduits, anti-sway plates, and standard parts.

[0028] Step 2: geometrically process the load-bearing structure to obtain a geometric model of the load-bearing structure of the tank;

[0029] The principle of geometry processing is: do not change the dynamic characteristics of the structure; geometry processing tools include: CAD software (such as Creo), finite element pre-processing software (such as HyperMesh, MSC.Patran);

[0030] This embodiment uses Creo and HyperMesh to perform geometric processing on the load-bearing structure. The geometric processing includes: removing chamfers and bolt holes, extracting the middle surface of the wall plate and the bottom, dividing the area according to the thickness of the wall plate and the bottom, and retaining hard lines according to the reinforcement position;

[0031] Step 3, divide the load-bearing structure geometric model of the tank into three-dimensional finite element meshes and assign corresponding attributes, and at the same time model the non-load-bearing structure in the form of additional mass, thereby obtaining a three-dimensional finite element model of the foam sandwich common bottom tank;

[0032] The meshing principle is: the mesh size can fully reflect the dynamic characteristics of the relevant structure and realize efficient modal calculation; the meshing tools are: finite element pre-processing software, such as HyperMesh, MSC.Patran;

[0033] In this embodiment, HyperMesh is used to perform three-dimensional finite element meshing on the geometric model of the load-bearing structure of the tank obtained in step 2. The meshing method is as follows: shell units with isotropic material properties are used to simulate the tank wall panels and the bottom without insulation coating layers, laminated composite material units are used to simulate the tank wall panels and the bottom with insulation coating layers, beam units with isotropic material properties are used to simulate the reinforcement on the wall panels, linear elastic three-dimensional solid units are used to simulate the insulation interlayer (i.e., foam interlayer), and the upper and lower surfaces of the linear elastic three-dimensional solid unit (insulation interlayer) share nodes with the shell unit, and the mesh is assigned with the properties of the corresponding structure. At the same time, the non-load-bearing structure is modeled in the form of additional mass to obtain a three-dimensional finite element model of the tank with foam interlayer and common bottom, as shown in FIG. Figure 2 As shown;

[0034] like Figure 4 The three-layer structure of the common bottom tank includes a lower bottom 1, an insulating interlayer 2 and an upper bottom 3. The upper bottom 3 and the lower bottom 1 are respectively arranged on the upper and lower surfaces of the insulating interlayer 2. When dividing the mesh, the shell element 4 with isotropic material properties is used to simulate the upper and lower bottoms, and the linear elastic three-dimensional solid element 5 is used to simulate the insulating interlayer, and the upper and lower surfaces of the linear elastic three-dimensional solid element 5 share nodes with the shell element 4. Figure 5 As shown;

[0035] The three-dimensional finite element model of the foam sandwich common bottom tank obtained in this step can be used for the structural dynamic analysis of the whole arrow;

[0036] Step 4: Obtaining modal test results of the foam sandwich common bottom tank through modal testing;

[0037] In order to conduct targeted model verification of the thermal insulation interlayer and the thermal insulation coating, the modal test should obtain the corresponding order modal parameters of the local vibration of the three-layer structure of the interlayer, the tank wall with the thermal insulation coating, and the bottom with the thermal insulation coating, and the modal parameters include frequency and vibration mode;

[0038] Step 5: simulate the modal test boundary, perform modal analysis based on the three-dimensional finite element model of the foam sandwich common bottom tank, and obtain modal simulation results;

[0039] In order to verify the model of the insulation interlayer and insulation coating layer in a targeted manner, the modal analysis should obtain the corresponding order modal parameters of the local vibration of the three-layer structure of the interlayer, the tank wall with insulation coating layer and the bottom with insulation coating layer, and the modal parameters include frequency and vibration mode; the modal analysis tool adopts finite element analysis software, such as MSC.Nastran;

[0040] Step 6: Perform correlation analysis on the modal test results obtained in step 4 and the modal simulation results obtained in step 5 to complete model verification;

[0041] Use finite element model validation software, such as FEMtools, to perform correlation analysis;

[0042] In this embodiment, the breathing frequency of the oxygen box barrel section (tank wall with insulation coating) is obtained in step 4 as 74.35 Hz, and the breathing frequency of the oxygen box barrel section is obtained in step 5 as 71.12 Hz. In the correlation analysis result, the breathing frequency deviation of the oxygen box barrel section is -4%, and the vibration mode MAC value is 90%. The breathing order vibration mode matching diagram of the oxygen box barrel section is as follows: Figure 3 As shown, the simulation deviation is very small and the vibration mode matching is very high.

[0043] The present invention can obtain a three-dimensional dynamic model of a foam sandwich common bottom tank and verify it through the results of cabin modal tests. The present invention has been successfully applied to the elastic design and coupling analysis of the first flight state of a new generation of domestic carrier rockets. The dynamic modeling method of the foam sandwich common bottom tank of the present invention can fully reflect the dynamic characteristics of the sandwich common bottom tank and improve the accuracy of the prediction of the full dynamic characteristics of the carrier rocket in flight state.

[0044] The sandwich common bottom modeling concept in the present invention can provide an effective model basis for simulating the dynamic characteristics of liquid on both sides, and can achieve accurate and efficient prediction of the dynamic characteristics of the entire arrow.

[0045] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for dynamic modeling and verification of a foam sandwich common bottom tank, characterized in that: For the interlayer common bottom of the storage tank, linear elastic three-dimensional solid elements are used to simulate the insulating interlayer during modeling. The upper bottom and lower bottom respectively set on the upper and lower surfaces of the insulating interlayer are simulated by shell elements with isotropic material properties, and the upper and lower surfaces of the linear elastic three-dimensional solid elements share nodes with the shell elements.

2. A method for dynamic modeling and verification of a foam sandwich common bottom tank as claimed in claim 1, characterized in that: include: Step 1: Simplify the digital prototype of the foam sandwich common bottom tank, and divide the tank structure into a load-bearing structure and a non-load-bearing structure according to its dynamic characteristics; Step 2: geometrically process the load-bearing structure to obtain a geometric model of the load-bearing structure of the tank; Step 3, divide the load-bearing structure geometric model of the tank into three-dimensional finite element meshes and assign corresponding attributes, and at the same time model the non-load-bearing structure in the form of additional mass, thereby obtaining a three-dimensional finite element model of the foam sandwich common bottom tank; Step 4: Obtaining modal test results of the foam sandwich common bottom tank through modal testing; Step 5: simulate the modal test boundary, perform modal analysis based on the three-dimensional finite element model of the foam sandwich common bottom tank, and obtain modal simulation results; Step 6: Perform correlation analysis on the modal test results obtained in step 4 and the modal simulation results obtained in step 5 to complete model verification.

3. A method for dynamic modeling and verification of a foam sandwich common bottom tank as claimed in claim 2, characterized in that: In step 1, according to the dynamic characteristics of the foam sandwich common bottom tank, the load-bearing structures are determined to be the front short shell, the cylinder section, the rear short shell, the front bottom, the sandwich common bottom, and the rear bottom, and the non-load-bearing structures are the instruments and equipment and their brackets, cables, ducts, anti-sway plates, and standard parts.

4. A method for dynamic modeling and verification of a foam sandwich common bottom tank as claimed in claim 2, characterized in that: In step 2, the principle of geometric processing is: do not change the structural dynamic characteristics; Geometry processing tools include: CAD software and finite element pre-processing software; geometry processing work includes: removal of chamfers and bolt holes, extraction of mid-surfaces of wall panels and bottoms, area division based on the thickness of wall panels and bottoms, and retention of hard lines based on reinforcement positions.

5. The method for dynamic modeling and verification of a foam sandwich common bottom tank according to claim 2, characterized in that: In the step 3, the meshing principle is: the mesh scale can fully reflect the dynamic characteristics of the relevant structure and realize efficient modal calculation; the meshing tool is: finite element pre-processing software; the meshing method is: using shell units with isotropic material properties to simulate the tank wall panels without insulation coating layer and the bottom without insulation coating layer, using laminated composite material units to simulate the tank wall panels with insulation coating layer and the bottom with insulation coating layer, using beam units with isotropic material properties to simulate the reinforcement on the wall panels, using linear elastic three-dimensional solid units to simulate the insulation interlayer, the upper and lower surfaces of the linear elastic three-dimensional solid units share nodes with the shell units, the mesh is assigned with the properties of the corresponding structure, and the non-load-bearing structure is modeled in the form of additional mass to obtain a three-dimensional finite element model of the foam interlayer common bottom tank.

6. A method for dynamic modeling and verification of a foam sandwich common bottom tank as claimed in claim 5, characterized in that: The three-dimensional finite element model of the foam sandwich common bottom tank obtained in step 3 can be used for the structural dynamic analysis of the entire arrow.

7. A method for dynamic modeling and verification of a foam sandwich common bottom tank as claimed in claim 2, characterized in that: In order to carry out targeted model verification of the insulating interlayer and the insulating coating, the modal test in step 4 and the modal analysis in step 5 should obtain the corresponding order modal parameters reflecting the local vibration of the three-layer structure of the interlayer, the tank wall with the insulating coating and the bottom with the insulating coating, and the modal parameters include frequency and vibration mode.

8. A method for dynamic modeling and verification of a foam sandwich common bottom tank as claimed in claim 2, characterized in that: In step 5, the modal analysis tool adopts finite element analysis software.

9. A method for dynamic modeling and verification of a foam sandwich common bottom tank as claimed in claim 2, characterized in that: In step 6, finite element model verification software is used to perform correlation analysis.

10. The method for dynamic modeling and verification of a foam sandwich common bottom tank according to claim 2, characterized in that: In step 6, the correlation analysis includes frequency deviation calculation and vibration mode MAC value calculation.

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