A launch vehicle substructure dynamic response analysis method based on local refinement model

Abstract

The application provides a launch vehicle substructure dynamics response analysis method based on a local refinement model, first, a one-dimensional longitudinal-lateral-torsional integrated model of a launch vehicle in an actual flight state is established, second, a three-dimensional dynamics model of a relevant cabin section containing substructures such as inertia components, instruments and equipment and the like which are modified after a modal test is assembled, and the substructures are characterized in that they are not the main load-bearing structures of the launch vehicle, and their function is to provide installation platforms for inertia components, instruments and equipment and the like, and then, prior external excitations such as interstage separation flow, frame recovery deformation and the like which are borne by the launch vehicle in the actual flight state are considered and applied, so that the dynamics response of the launch vehicle substructure is extracted to provide a basis for subsequent stability control analysis and environmental condition formulation. The technical problem that there is currently a lack of accurate and efficient prediction methods for substructures is solved. The application can be applied to the dynamics response analysis of the substructure of the launch vehicle.

Description

Technical Field

[0001] This invention relates to the field of launch vehicles, and in particular to a method for analyzing the dynamic response of launch vehicle secondary structures based on a locally refined model. Background Technology

[0002] Besides the main force-transmitting sections of the launch vehicle, which are primarily constructed using riveted modules and mesh reinforcement, secondary structures within the rocket, such as inertial navigation system supports and instrument disks, do not bear force transmission responsibility. Their main function is to provide mounting platforms for inertial components and instruments. Due to the transmission of external excitation, local structures are susceptible to factors such as local deformation of the skin, deformation of nearby openings, and uncertainties in component connections. Their dynamic response is a crucial parameter for the stability design and environmental condition design of the launch vehicle's attitude control system. During the launch vehicle design process, one-dimensional models cannot reflect the true response at the secondary structures, while three-dimensional models are too inefficient for iterative model design. Therefore, environmental conditions at the secondary structures are mostly based on ground vibration tests. However, due to the differences between ground and space, environmental conditions are formulated based on the maximum envelope of ground vibration tests with a certain margin, lacking accurate and efficient methods for predicting the dynamic response of secondary structures. Therefore, research on relevant prediction methods is needed to replace some vibration tests and improve the efficiency of launch vehicle development. Summary of the Invention

[0003] The purpose of this invention is to provide a method for analyzing the dynamic response of launch vehicle secondary structures based on a locally refined model, so as to solve the technical problem that there is currently a lack of accurate and efficient prediction methods for secondary structures in the field.

[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is: to provide a method for dynamic response analysis of launch vehicle secondary structure based on a local refined model, comprising the following steps:

[0005] Step S1: Establish a three-dimensional finite element model of the section where the secondary structure of the modal test state is located;

[0006] Step S2: Based on the three-dimensional finite element model established in step S1, simulate the modal test state and perform modal analysis on the section where the secondary structure is located.

[0007] Step S3: Analyze the vibration mode characteristics of the secondary structure section and its differences from the test vibration mode, and correct the model of the secondary structure section.

[0008] Step S4: Establish a one-dimensional integrated longitudinal, transverse, and torsional model of the entire rocket in flight mode;

[0009] Step S5: Assemble the model modified in step S3 and the model established in step S4.

[0010] Step S6: Perform modal analysis on the model obtained in step S5;

[0011] Step S7: Compare and judge the difference between the modal analysis results in step S6 and the modal analysis results of the three-dimensional refined finite element model. If the difference exceeds the acceptable deviation range, the model established in step S4 is corrected and steps S5 to S7 are repeated until the modal analysis results meet the acceptable deviation range, and the dynamic response analysis model of the launch vehicle secondary structure is obtained.

[0012] Step S8: Apply external stimuli of actual flight state to the model obtained in step S5;

[0013] Step S9: Use the direct extraction method to obtain the dynamic response at the location of the secondary structure of interest in the entire arrow.

[0014] Furthermore, in step S1, the secondary structure refers to the structural form within the launch vehicle that does not bear the main force transmission function, and its function is to provide an installation platform for inertial components and instruments.

[0015] Furthermore, in step S1, the principle for modeling the section where the secondary structure is located is to fully reflect the dynamic characteristics of the secondary structure.

[0016] Furthermore, in step S2, when simulating the modal test state, the corresponding order modal parameters reflecting the local vibration of the inertial device should be obtained, so that the secondary structure can be specifically corrected in step S3.

[0017] Furthermore, during the assembly process in step S5, a three-dimensional finite element model is used for the sections that have a significant impact on the overall rocket modes to avoid losing important modes.

[0018] Furthermore, in step S7, the model established in step S4 is modified. The modification methods include reconstructing the connection relationships, modifying the measured dimensions and equivalent stiffness of the structure, and modifying the measured mass of the structure.

[0019] Furthermore, in step S8, the external stimulus is a priori distribution; the distribution of the external stimulus is updated by accumulating flight sample data.

[0020] The beneficial effects of the method for analyzing the dynamic response of launch vehicle secondary structures based on a locally refined model provided by this invention are as follows:

[0021] This invention proposes a method for analyzing the dynamic response of secondary structures in launch vehicles based on a locally refined model. This method can be practically applied to predicting the dynamic response of secondary structures during the entire flight state of launch vehicles. While ensuring efficient computation, this method can accurately output the dynamic response of secondary structures, improving the efficiency of launch vehicle development. On the one hand, this method is based on modal tests of the section containing the secondary structure, performing model correction on the three-dimensional model of the section. On the other hand, it updates the prior external excitations by accumulating flight test data, and uses a direct extraction method to output the displacement, velocity, and acceleration responses of the secondary structure of interest. This effectively solves the technical problem of lacking an accurate and efficient method for predicting the dynamic response of secondary structures during flight. Attached Figure Description

[0022] The invention will be further described below with reference to the accompanying drawings:

[0023] Figure 1 This is a flowchart of a method for analyzing the dynamic response of a launch vehicle secondary structure based on a locally refined model, as proposed in this invention.

[0024] Figure 2 This is a detailed model of the secondary structure of a certain new generation of launch vehicle.

[0025] Figure 3 This is the skin breathing order vibration mode of the corrected local refined model.

[0026] Figure 4 This is a dynamic response analysis model for the secondary structure of a certain new-generation launch vehicle.

[0027] Figure 5 This represents the pressure distribution in the interstage separated flow.

[0028] Figure 6 This represents the dynamic response of the secondary structure. Detailed Implementation

[0029] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a more detailed explanation of the proposed method for analyzing the dynamic response of launch vehicle secondary structures based on a locally refined model. The advantages and features of the invention will become clearer from the following description and claims. It should be noted that the accompanying drawings are in a very simplified form and use non-precise ratios, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0030] Example 1

[0031] Based on the satellite-rocket coupling analysis of a certain new-generation launch vehicle in China, the dynamic response of the secondary structure (rate gyroscope position) in the interstage section under the most severe lateral load conditions during the active flight phase of the rocket body is output. The flowchart is shown below. Figure 1 As shown, the specific process is as follows:

[0032] Step 1: Establish a three-dimensional finite element model of the section containing the secondary structure in the modal test state, such as... Figure 2 As shown;

[0033] Step 2: Based on the finite element model established in Step 1, simulate the modal test conditions and perform modal analysis on the section where the secondary structure is located, where the local skin breathing frequency of the rate gyroscope is 113.20Hz;

[0034] Step 3: Obtain interstage modal parameters through modal testing. To enable targeted model correction of the rate gyroscope mounting bracket and its surrounding components, modal testing should obtain the corresponding order modal parameters reflecting the local vibration of the rate gyroscope. The local skin breathing frequency of the rate gyroscope is 117.77 Hz. Based on the test results, the structural mass is corrected, and the connection between the rate gyroscope mounting bracket and the skin is adjusted. The corrected local refined model skin breathing mode shape is as follows: Figure 3 As shown;

[0035] Step 4: Establish a one-dimensional integrated longitudinal, transverse, and torsional model of the entire rocket in flight mode;

[0036] Step 5: Assemble the model modified in Step 3 and the model established in Step 4 to obtain the dynamic response analysis model of the secondary structure of a certain new generation launch vehicle, as shown below. Figure 4 As shown;

[0037] Step 6: Perform modal analysis on the model obtained in Step 5, and obtain the first-order bending frequency of 2.374Hz.

[0038] Step 7: Compare the modal analysis results obtained in Step 6 with the modal analysis results of the three-dimensional refined finite element model. The first-order bending frequency of the three-dimensional refined finite element model modal analysis is 2.397Hz, and the deviation does not exceed 1%.

[0039] Step 8: Apply a priori external excitation to the model obtained in Step 5. The inverted cone angle of the fairing of a certain new-generation launch vehicle causes severe airflow separation. The separated flow acts on the interstage section, generating large pulsating pressure, which causes skin and stringer vibration, resulting in significant vibration of the rate gyroscope. The external excitation distribution is as follows: Figure 5 As shown;

[0040] Step 9: The dynamic response of the secondary structure (rate gyroscope position) of the interstage segment is extracted using the direct extraction method. After verification by flight test, the relative deviation between the dynamic response simulation results and the flight test results is no more than 8%, and the results are in good agreement.

[0041] In step 7, the cyclical process is repeated if the modal analysis results exceed the acceptable deviation range after the initial model correction, until the modal analysis results meet the acceptable deviation range.

[0042] This invention has been successfully applied to the coupled analysis of the maiden flight of a new generation of launch vehicles in China. The method described in this invention can fully reflect the local dynamic response of the secondary structure and improve the prediction accuracy of the dynamic response of the secondary structure during the launch vehicle's flight.

[0043] The contents not described in detail in this specification are prior art known to those skilled in the art. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for analyzing the dynamic response of a substructure of a launch vehicle based on a locally refined model, characterized in that, The method comprises the following steps: Step S1, establishing a three-dimensional finite element model of a cabin section where a modal test state secondary structure is located; the secondary structure refers to a structure form in a launch vehicle that does not bear a main force transmission function, and the function is to provide an installation platform for inertial devices, instruments and equipment; Step S2, according to the three-dimensional finite element model established in the step S1, simulating a modal test state, and performing modal analysis on the cabin section where the secondary structure is located; when the modal test state is simulated, corresponding order modal parameters reflecting local vibration of the inertial device should be obtained, so that the secondary structure can be specifically corrected in the step S3; Step S3, analyzing vibration mode characteristics of the cabin section where the secondary structure is located and differences between the vibration mode characteristics and a test vibration mode, and correcting the model of the cabin section where the secondary structure is located; Step S4, establishing a one-dimensional longitudinal-lateral-torsional integrated model of the launch vehicle in a flight state; Step S5, assembling the model corrected in the step S3 and the model established in the step S4 to obtain a launch vehicle secondary structure dynamics response analysis model; Step S6, performing modal analysis on the model obtained in the step S5; Step S7, comparing and judging differences between the modal analysis result in the step S6 and a modal analysis result of a three-dimensional refined finite element model, if the differences exceed an acceptable deviation range, correcting the model established in the step S4 and repeating the steps S5 to S7 until the modal analysis result meets the acceptable deviation range, and obtaining the launch vehicle secondary structure dynamics response analysis model; Step S8, applying an actual flight state external excitation to the model obtained in the step S7; the external excitation is a prior distribution; by accumulating flight sample data, the distribution form of the external excitation is updated; Step S9, using a direct extraction method to obtain dynamics responses at positions of the secondary structure of the launch vehicle.

2. The local refined model based secondary structure dynamic response analysis method of launch vehicle of claim 1, wherein, In the step S1, the principle of modeling of the cabin section where the secondary structure is located is to sufficiently reflect dynamics characteristics of the secondary structure.

3. The local refined model based dynamics response analysis method of a launch vehicle substructure of claim 1, wherein, In the assembling process of the step S5, a three-dimensional finite element model is used for a cabin section that has a greater influence on a modal of the launch vehicle, so as to avoid losing important modes.

4. The local refined model based dynamics response analysis method of a launch vehicle substructure of claim 1, wherein, In the step S7, the model established in the step S4 is corrected, and the correction method includes reconstruction of a connection relationship, correction of a measured size and equivalent stiffness of the structure, and correction of a measured mass of the structure.

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