CN114218823A - Carrier rocket fatigue load assignment system and method based on three-dimensional model - Google Patents

Carrier rocket fatigue load assignment system and method based on three-dimensional model Download PDF

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CN114218823A
CN114218823A CN202111435859.1A CN202111435859A CN114218823A CN 114218823 A CN114218823 A CN 114218823A CN 202111435859 A CN202111435859 A CN 202111435859A CN 114218823 A CN114218823 A CN 114218823A
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fatigue load
finite element
pneumatic
carrier rocket
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邓思超
徐振亮
吴胜宝
汪小卫
肖肖
张恒浩
孔令超
庄方方
张展智
艾立强
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China Academy of Launch Vehicle Technology CALT
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Abstract

A carrier rocket fatigue load assignment system and method based on a three-dimensional model comprises the following steps: the system comprises a carrier rocket three-dimensional modeling module, a pneumatic fatigue load conversion module and a fatigue load post-processing module; a carrier rocket three-dimensional modeling module establishes a refined three-dimensional finite element model of the carrier rocket; the pneumatic fatigue load conversion module obtains a pneumatic fatigue load input by a superior level, and a minimum deformation energy is obtained by adopting a pneumatic fatigue load minimum deformation energy conversion algorithm suitable for a carrier rocket; obtaining the force and moment of the fatigue load relative to the mass center in the three-dimensional finite element model according to the minimum deformation energy to complete assignment processing; and the fatigue load post-processing module judges whether the pneumatic fatigue load conversion algorithm of the carrier rocket meets the use requirement or not according to the force and moment of the fatigue load relative to the mass center in the three-dimensional finite element model. The invention solves the problem of fine assignment of the fatigue load of the carrier rocket, so that the load design of the carrier rocket is more reasonable, the design margin is effectively reduced, and the safety and the reliability of the structure are improved.

Description

Carrier rocket fatigue load assignment system and method based on three-dimensional model
Technical Field
The invention relates to a carrier rocket load design method, in particular to a carrier rocket fatigue load refined assignment system and a carrier rocket fatigue load refined assignment method.
Background
At present, a particle beam model is adopted for calculating static load of a traditional carrier rocket structure in China, structural differences are not considered in the model, the model is provided by a method of adding a safety coefficient to the static load, regularity research on a load excitation source is lacked, load design conditions tend to be conservative, and the obtained load result is not high in fine design level and is not beneficial to structure weight estimation and rigidity design.
Disclosure of Invention
The technical problem of the invention is solved: the defects of the prior art are overcome, a novel load design system and a novel load design method of the carrier rocket are provided, and a more accurate three-dimensional load calculation model of the carrier rocket is established; the three-dimensional fluid-solid fatigue load conversion technology is researched, the structure quality and the continuous distribution characteristic of the pneumatic fatigue load can be truly reflected, and the conversion of the pneumatic grid node load and the structural finite element grid node load is realized; carrying out the fatigue load assignment result post-processing technical research to provide more detailed load input for strength design; the load reducing condition of the carrier rocket is realized, and the structure of the carrier rocket is used for reducing weight, so that the carrying capacity is improved.
The technical solution of the invention is as follows:
a fatigue load assignment system of a carrier rocket based on a three-dimensional model comprises: the system comprises a carrier rocket three-dimensional modeling module, a pneumatic fatigue load conversion module and a fatigue load post-processing module;
the three-dimensional modeling module of the carrier rocket comprises: establishing a refined three-dimensional finite element model of the carrier rocket; the three-dimensional finite element model can simulate the structural form, the layout, the mass center, the rotational inertia and the connection rigidity of the carrier rocket.
Pneumatic fatigue load conversion module: acquiring pneumatic fatigue load input by a superior level, and acquiring minimum deformation energy by adopting a pneumatic fatigue load minimum deformation energy conversion algorithm suitable for a carrier rocket; obtaining the force and moment of the fatigue load relative to the mass center in the three-dimensional finite element model according to the minimum deformation energy to complete assignment processing;
the method for obtaining the minimum deformation energy U by the pneumatic fatigue load conversion module specifically comprises the following steps:
Figure BDA0003381721820000021
Figure BDA0003381721820000022
Figure BDA0003381721820000023
Figure BDA0003381721820000024
wherein, UjThe deformation energy of the finite element node j is shown; EJ is the flexural stiffness of the hypothetical beam; pjForce of finite element node j; l isjThe distance from the finite element node j to the nearest aerodynamic fatigue load node is the length of the assumed beam; pAThe resultant force of the pneumatic fatigue model; x is the number ofj、yj、zjThree-direction coordinates of a finite element node j are shown; x is the number ofA、yA、zAThree-direction coordinates of the mass center of the pneumatic fatigue load model;
Figure BDA0003381721820000025
λ,λx,λy,λzand establishing a multiplier in an extreme function for the Lagrange multiplier method, wherein n is the number of nodes of the finite element model.
A fatigue load post-processing module: and judging whether the pneumatic fatigue load conversion algorithm of the carrier rocket meets the use requirement or not according to the force and moment of the fatigue load relative to the mass center in the three-dimensional finite element model.
The method for judging whether the pneumatic fatigue load conversion algorithm of the carrier rocket meets the use requirement by the fatigue load post-processing module specifically comprises the following steps:
21) calculating the resultant force F and the resultant moment M of the pneumatic fatigue load relative to the mass center of the carrier rocket;
22) calculating the resultant force and resultant moment of the finite element load based on the mass center according to the force and moment of the fatigue load relative to the mass center in the three-dimensional finite element model;
23) obtaining a difference x1 between the resultant force of the pneumatic fatigue load and the resultant force of the finite element load, and obtaining a difference x2 between the resultant moment of the pneumatic fatigue load and the resultant moment of the finite element load;
24) if x1< 0.5% F, and x2< 0.5% M; judging that the pneumatic fatigue load conversion algorithm meets the use requirement; otherwise, judging that the pneumatic fatigue load conversion algorithm does not meet the use requirement.
A three-dimensional model-based carrier rocket fatigue load assignment method comprises the following steps:
1) establishing a three-dimensional finite element model of the carrier rocket, and carrying out mesh division; simulating the real structural form, layout, mass center, rotational inertia and connection rigidity of the carrier rocket by using the three-dimensional finite element model in the step 1);
2) acquiring pneumatic fatigue load input by a superior level, and acquiring minimum deformation energy by adopting a pneumatic fatigue load minimum deformation energy conversion algorithm suitable for a carrier rocket;
3) obtaining the force and moment of the fatigue load relative to the mass center in the three-dimensional finite element model according to the minimum deformation energy, and finishing assignment processing;
4) judging whether the pneumatic fatigue load conversion algorithm of the carrier rocket meets the use requirement or not according to the force and the moment of the fatigue load relative to the mass center in the three-dimensional finite element model; if the requirements are not met, the grid is divided again and the step 1) is returned until the pneumatic fatigue load conversion algorithm of the carrier rocket meets the use requirements.
Compared with the prior art, the invention has the advantages that:
(1) a fatigue load assignment method based on a three-dimensional model is innovatively adopted in the load design of the reusable carrier rocket, the fatigue load assignment position is finer, a novel design method is provided for the load design of the carrier rocket, and more accurate input conditions are provided for the structural design.
(2) The carrier rocket complex structure is repeatedly used, a minimum deformation energy fatigue load three-dimensional conversion assignment method is adopted, the fatigue load conversion deviation is less than 0.5%, the fatigue load assignment precision is higher, and a favorable basis is provided for the weight reduction design of the carrier rocket structure.
(3) The method for circularly searching the finite element unit closest to the pneumatic point can accelerate the design iteration process and improve the calculation efficiency.
Drawings
FIG. 1 is a view of the assembly of the substages of a launch vehicle.
Fig. 2 is a geometrical model of a launch vehicle sublevel.
FIG. 3 is a finite element mesh for a launch vehicle sublevel.
Fig. 4 is a pneumatic grid.
FIG. 5 is a graphical representation of finite element node fatigue loading after transformation.
FIG. 6 is a flow chart of the method of the present invention.
Detailed Description
The invention relates to a fatigue load assignment system of a carrier rocket based on a three-dimensional model, which comprises the following components: the device comprises a carrier rocket three-dimensional modeling module, a pneumatic fatigue load conversion module and a fatigue load post-processing module.
The three-dimensional modeling module of the carrier rocket comprises: establishing a refined three-dimensional finite element model of the carrier rocket; the three-dimensional finite element model can simulate the structural form, the layout, the mass center, the rotational inertia and the connection rigidity of the carrier rocket.
Pneumatic fatigue load conversion module: acquiring pneumatic fatigue load input at the upper level, and acquiring minimum deformation energy by adopting a pneumatic fatigue load minimum deformation energy conversion algorithm suitable for a carrier rocket due to the inconsistency of pneumatic calculation model nodes and refined three-dimensional finite element model nodes; obtaining the force and moment of the fatigue load relative to the mass center in the three-dimensional finite element model according to the minimum deformation energy to complete assignment processing;
the method for obtaining the minimum deformation energy U by the pneumatic fatigue load conversion module specifically comprises the following steps:
Figure BDA0003381721820000041
Figure BDA0003381721820000042
Figure BDA0003381721820000043
Figure BDA0003381721820000044
wherein: u shapejThe deformation energy of the finite element node j is shown; EJ is the flexural stiffness of the hypothetical beam; pjForce of finite element node j; l isjThe distance from the finite element node j to the nearest aerodynamic fatigue load node is the length of the assumed beam; pAThe resultant force of the pneumatic fatigue model; x is the number ofj、yj、zjThree-direction coordinates of a finite element node j are shown; x is the number ofA、yA、zAThree-direction coordinates of the mass center of the pneumatic fatigue load model;
Figure BDA0003381721820000051
λ,λx,λy,λzand establishing a multiplier in an extreme function for the Lagrange multiplier method, wherein n is the number of nodes of the finite element model.
A fatigue load post-processing module: and judging whether the pneumatic fatigue load conversion algorithm of the carrier rocket meets the use requirement or not according to the force and moment of the fatigue load relative to the mass center in the three-dimensional finite element model. And carrying out rapid batch processing on the load calculation result data, and realizing visual display and text output in the form of graphs, charts and cloud pictures.
The method for judging whether the pneumatic fatigue load conversion algorithm of the carrier rocket meets the use requirement by the fatigue load post-processing module specifically comprises the following steps:
21) calculating the resultant force F and the resultant moment M of the pneumatic fatigue load relative to the mass center of the carrier rocket;
22) calculating the resultant force and resultant moment of the finite element load based on the mass center according to the force and moment of the fatigue load relative to the mass center in the three-dimensional finite element model;
23) obtaining a difference x1 between the resultant force of the pneumatic fatigue load and the resultant force of the finite element load, and obtaining a difference x2 between the resultant moment of the pneumatic fatigue load and the resultant moment of the finite element load;
24) if x1< 0.5% F, and x2< 0.5% M; judging that the pneumatic fatigue load conversion algorithm meets the use requirement; otherwise, judging that the pneumatic fatigue load conversion algorithm does not meet the use requirement.
As shown in fig. 6, a three-dimensional model-based method for assigning fatigue loads to a launch vehicle comprises the following steps:
1) establishing a three-dimensional finite element model of the carrier rocket, and carrying out mesh division; taking the shell unit as a main part, and dividing the grid into regular quadrangles as much as possible; simulating the real structural form, layout, mass center, rotational inertia and connection rigidity of the carrier rocket by using the three-dimensional finite element model in the step 1);
2) acquiring pneumatic fatigue load input by a superior level, and acquiring minimum deformation energy by adopting a pneumatic fatigue load minimum deformation energy conversion algorithm suitable for a carrier rocket;
3) obtaining the force and moment of the fatigue load relative to the mass center in the three-dimensional finite element model according to the minimum deformation energy, and finishing assignment processing;
4) judging whether the pneumatic fatigue load conversion algorithm of the carrier rocket meets the use requirement or not according to the force and the moment of the fatigue load relative to the mass center in the three-dimensional finite element model; and if the requirements are not met, re-dividing the meshes and returning to the step 1) until the aerodynamic fatigue load conversion algorithm of the carrier rocket meets the use requirements (different repeated cycles are that the mesh division is changed, namely three-direction coordinates of the three-dimensional finite element nodes are changed, and the steps 1) to 3) are repeated).
Examples
(1) Three-dimensional modeling module of carrier rocket
The launch vehicle structure is generally comprised of an unsealed hull section structure (tail section, transition section, tank section, staging section, instrument bay, fairing, etc.) and rocket valves, conduits, gas cylinders, and instrument cables. When a three-dimensional finite element model of the carrier rocket is established, instruments, cables and the like on each section are reasonably and equivalently simplified according to research requirements to form a proper finite element unit, so that the structural rigidity of the carrier rocket is reasonably simulated, and the fatigue load of the carrier rocket is conveniently assigned for multi-round repeated iterative analysis. For some special parts, such as connecting parts, on the carrier rocket, when the design needs to mainly investigate the structural strength of the special parts, a proper finite element model can be established according to the needs, and more accurate load distribution of the parts is provided, so that a basis is provided for the structural design of the special parts. A three-dimensional model is established through commercial three-dimensional modeling software, and a simplified model is obtained, wherein a certain carrier rocket sublevel consists of a stage section, an oxygen box, a box section, a combustion box, a rear transition section, an engine mounting bracket, a tail section, an engine and a frame, and an assembly diagram is shown as 1.
And processing the three-dimensional model into an intermediate conversion format, and importing the intermediate conversion format into CAE to obtain the initial model shown in FIG. 2.
The carrier rocket is mainly of a thin-wall structure, therefore, shell units are adopted to divide grids, the grids are divided into regular quadrangles as much as possible, structures such as a stage section, an oxygen box, a fuel box and the like are distributed and divided according to the characteristics of a sub-stage structure of the carrier rocket, and the carrier rocket is assembled. The finite element mesh is shown in fig. 3.
And (3) carrying out parameter setting on each section, wherein the main parameters comprise equivalent density, equivalent thickness, elastic modulus, Poisson ratio and shear modulus.
(2) Pneumatic fatigue load conversion module
1) Pneumatic fatigue load calculation
According to the characteristic ballistic data, specifically including flight time, altitude, speed, Mach number, dynamic pressure and separation time, selecting the working condition with the largest overload to calculate the pneumatic fatigue load, and calculating the pneumatic fatigue load through pneumatic software, as shown in FIG. 4, obtaining the pneumatic fatigue load of the carrier rocket, specifically including three-direction pneumatic force and moment coefficients.
2) Conversion of pneumatic fatigue loads into structural fatigue loads
And (3) equivalently converting the pneumatic fatigue load into the structural fatigue load by developing a load conversion program.
Figure BDA0003381721820000071
Inputting documents
Input file 1: this file is used to input the calculation of the aerodynamic fatigue load. The data are 6 columns in total, the first three columns are the Cartesian coordinates of the pneumatic nodes, and the last three columns are the components of the pneumatic nodes in the three directions of the Cartesian coordinates. The carrier rocket is divided into a shell, a tail section baffle, an engine and other parts according to a carrier rocket sublevel area, and the pneumatic fatigue load data of the parts are respectively made into input files 1 as pneumatic fatigue load input.
Input file 2: the file is used for inputting the information of the elements and the nodes in the finite element model. The former part is unit information and the latter part is node information. The method is characterized in that a sub-level area is divided into a shell, a tail section baffle, an engine and the like, and finite element model geometric data of the parts are respectively made into an input file 2 and used as unit and node information input.
The node information output by the finite element software is in a large-domain format, when the finite element model information is read in by the program, the large-domain format of the node information needs to be converted into a small-domain format, otherwise, the program reports errors.
Figure BDA0003381721820000072
Inputting parameters
Various control parameters required by program operation are divided into a forced type and a non-forced type. The mandatory type must be input by the user, and parameters which have a large influence on the result may be adopted as default values without the mandatory type. The input parameters mainly comprise unit types, unit orders, input file formats, pneumatic input fatigue load forms and units, structural output fatigue load forms and units, grid forms, moment point coordinates, pneumatic coordinate origins, structural coordinate origins and coordinate axis corresponding relations.
Figure BDA0003381721820000073
Finding finite element structure node closest to pneumatic node
Inputting fatigue loads on the pneumatic nodes, finding the finite element unit structural nodes closest to the pneumatic nodes, circulating all the pneumatic points, circulating the finite element structural units under each pneumatic point, comparing the distances between the pneumatic points and the centers of the finite element structural units, and finding the finite element units closest to the pneumatic nodes (the central coordinates of the finite element units are the average values of the coordinates of the nodes on the units), namely the finite element units to which the pneumatic nodes belong. And translating the force on the pneumatic node to each node of the finite element unit. The method for circularly searching the finite element unit closest to the pneumatic point can accelerate the design iteration process and improve the calculation efficiency.
Figure BDA0003381721820000081
Pneumatic grid andconversion algorithm for node load data of structural finite element grid
And after finding out the finite element unit with the pneumatic fatigue load closest to the pneumatic point, carrying out pneumatic fatigue load conversion through a minimum deformation energy algorithm. The structure is deformed by the force, thereby storing deformation energy, referred to as strain potential energy or deformation energy, within the structure. If the stress process is static or quasi-static, the structure does not generate kinetic energy, and the internal friction of the structure is assumed to be negligible, so that the temperature change of the structure caused by stress can be ignored, and the work of the external force in the structure deformation process is completely converted into deformation energy according to the law of energy conservation.
An intangible beam is assumed between the finite element node and the pneumatic node. The beam is a cantilever beam fixedly supported at one end of a pneumatic node, and the length of the cantilever beam is LjThen the finite element node at the free end of the cantilever beam is assigned to the load PjThe deformation energy is as follows:
Figure BDA0003381721820000082
in the formula: EJ is the bending stiffness of the hypothetical beam.
The number of finite element nodes in the three-dimensional model of the carrier rocket is n, and the deformation energy is as follows:
Figure BDA0003381721820000083
according to the principle of minimum deformation energy, the load distributed to the finite element nodes should minimize the deformation energy of the whole system, and at the same time, the static equivalent (equal resultant force and equal resultant moment) condition should be satisfied, that is, the following four equations should be satisfied:
Figure BDA0003381721820000084
Figure BDA0003381721820000091
in the formula: n is the number of nodes of the finite element model, and n is 1, 2, 3 … …
Taking the four equations of the formula (3) as constraint conditions, establishing an extremum function by adopting a Lagrange multiplier method as follows:
Figure BDA0003381721820000092
in the formula:
Figure BDA0003381721820000093
λ,λx,λy,λzis a multiplier.
As can be seen from the principle of minimum deformation energy, the actual load loading condition should minimize the deformation energy of the whole system. In order to minimize the deformation energy of the entire system, i.e. to minimize F (λ, λ)x,λy,λz) Taking the minimum value, the function pair PjThe partial derivative is equal to zero.
Order:
Figure BDA0003381721820000094
obtaining:
Figure BDA0003381721820000095
thus, the device is provided with
Figure BDA0003381721820000096
Substituting formula (3) for formula (4) to obtain:
Figure BDA0003381721820000097
solving the formula (8) by adopting a column principal element Gaussian elimination method to obtain lambda and lambdax,λy,λzAnd obtaining the node loads distributed to the finite element nodes in the influence domain by the subsequent formula (7). And executing the calculation process on all the finite element nodes, calculating the loads distributed to all the finite element nodes in the influence domain of each pneumatic node, and finally accumulating the loads distributed to the same node to obtain the load of the node.
The deformation energy is converted from pneumatic node fatigue load to finite element node load by a minimum deformation energy algorithm. And developing related numerical conversion software, and enabling the total load, the total pressure center and the force transmission route to be unchanged according to a static equivalent principle and a force transmission route invariance principle, so that the real transmission of the load is ensured, as shown in fig. 5. Deviation requirements before and after pneumatic fatigue load conversion: the resultant force is less than 0.5%, the resultant moment is less than 0.5%, the fatigue load assignment precision is higher, and a favorable basis is provided for the weight reduction design of the carrier rocket structure.
3) Fatigue load post-processing module
According to the traditional load output format, the load for most section structural design is usually provided in the form of section concentrated force, and the load output calculated by adopting a three-dimensional finite element model is finite element unit force which needs to be synthesized for structural design. After a complete three-dimensional finite element model is established for analysis, the post-processing of the load calculation result is planned to be realized. Compiling a corresponding result post-processing program to automatically extract the internal load of the required component, synthesizing the axial force, the shearing force and the bending moment of the required station and carrying out envelope analysis on the required working condition; and realizing visual display and text output of the load calculation result in the form of a graph, a chart and a cloud picture.
Post-processing and visualization techniques are employed. The load calculation result data is rapidly processed in batches, and visual display and text output are realized in the form of graphs, charts and cloud pictures. The main contents include the combination of station axis, bending, shearing and twisting loads, the extraction of internal loads and the interface with structural strength.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.
Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.

Claims (8)

1. A carrier rocket fatigue load assignment system based on a three-dimensional model is characterized by comprising: the system comprises a carrier rocket three-dimensional modeling module, a pneumatic fatigue load conversion module and a fatigue load post-processing module;
the three-dimensional modeling module of the carrier rocket comprises: establishing a refined three-dimensional finite element model of the carrier rocket;
pneumatic fatigue load conversion module: acquiring pneumatic fatigue load input by a superior level, and acquiring minimum deformation energy by adopting a pneumatic fatigue load minimum deformation energy conversion algorithm suitable for a carrier rocket; obtaining the force and moment of the fatigue load relative to the mass center in the three-dimensional finite element model according to the minimum deformation energy to complete assignment processing;
a fatigue load post-processing module: and judging whether the pneumatic fatigue load conversion algorithm of the carrier rocket meets the use requirement or not according to the force and moment of the fatigue load relative to the mass center in the three-dimensional finite element model.
2. The three-dimensional model-based launch vehicle fatigue load assignment system of claim 1, wherein a three-dimensional finite element model is used to simulate launch vehicle structural form, layout, center of mass, moment of inertia, and joint stiffness.
3. The three-dimensional model-based carrier rocket fatigue load assignment system according to claim 2, wherein the method for obtaining the minimum deformation energy U by the pneumatic fatigue load conversion module specifically comprises:
Figure FDA0003381721810000011
Figure FDA0003381721810000012
Figure FDA0003381721810000013
Figure FDA0003381721810000014
wherein: u shapejThe deformation energy of the finite element node j is shown; EJ is the flexural stiffness of the hypothetical beam; pjForce of finite element node j; l isjThe distance from the finite element node j to the nearest aerodynamic fatigue load node; pAThe resultant force of the pneumatic fatigue model; x is the number ofj、yj、zjThree-direction coordinates of a finite element node j are shown; x is the number ofA、yA、zAThree-direction coordinates of the mass center of the pneumatic fatigue load model;
Figure FDA0003381721810000021
λ,λx,λy,λzand establishing a multiplier in an extreme function for the Lagrange multiplier method, wherein n is the number of nodes of the finite element model.
4. The three-dimensional model-based carrier rocket fatigue load assignment system according to claim 2 or 3, wherein the fatigue load post-processing module is a method for judging whether the aerodynamic fatigue load conversion algorithm of the carrier rocket meets the use requirements, and specifically comprises the following steps:
21) calculating the resultant force F and the resultant moment M of the pneumatic fatigue load relative to the mass center of the carrier rocket;
22) calculating the resultant force and resultant moment of the finite element load based on the mass center according to the force and moment of the fatigue load relative to the mass center in the three-dimensional finite element model;
23) obtaining a difference x1 between the resultant force of the pneumatic fatigue load and the resultant force of the finite element load, and obtaining a difference x2 between the resultant moment of the pneumatic fatigue load and the resultant moment of the finite element load;
24) if x1< 0.5% F, and x2< 0.5% M; judging that the pneumatic fatigue load conversion algorithm meets the use requirement; otherwise, judging that the pneumatic fatigue load conversion algorithm does not meet the use requirement.
5. A carrier rocket fatigue load assignment method based on a three-dimensional model is characterized by comprising the following steps:
1) establishing a three-dimensional finite element model of the carrier rocket, and carrying out mesh division;
2) acquiring pneumatic fatigue load input by a superior level, and acquiring minimum deformation energy by adopting a pneumatic fatigue load minimum deformation energy conversion algorithm suitable for a carrier rocket;
3) obtaining the force and moment of the fatigue load relative to the mass center in the three-dimensional finite element model according to the minimum deformation energy, and finishing assignment processing;
4) judging whether the pneumatic fatigue load conversion algorithm of the carrier rocket meets the use requirement or not according to the force and the moment of the fatigue load relative to the mass center in the three-dimensional finite element model; and if the requirements are not met, re-dividing the meshes and returning to the step 1) until the aerodynamic fatigue load conversion algorithm of the carrier rocket meets the use requirements (different repeated cycles are that the mesh division is changed, namely three-direction coordinates of the three-dimensional finite element nodes are changed, and the steps 1) to 3) are repeated).
6. The three-dimensional model-based fatigue load assignment method for a launch vehicle according to claim 5, wherein the three-dimensional finite element model in step 1) simulates the real structural form, layout, center of mass, moment of inertia and joint stiffness of the launch vehicle.
7. The three-dimensional model-based carrier rocket fatigue load assignment method according to claim 6, wherein the step 2) is a method for obtaining the minimum deformation energy, and specifically comprises the following steps:
Figure FDA0003381721810000031
Figure FDA0003381721810000032
Figure FDA0003381721810000033
Figure FDA0003381721810000034
wherein: u shapejThe deformation energy of the finite element node j is shown; EJ is the flexural stiffness of the hypothetical beam; pjForce of finite element node j; l isjThe distance from the finite element node j to the nearest aerodynamic fatigue load node; pAThe resultant force of the pneumatic fatigue model; x is the number ofj、yj、zjThree-direction coordinates of a finite element node j are shown; x is the number ofA、yA、zAThree-direction coordinates of the mass center of the pneumatic fatigue load model;
Figure FDA0003381721810000035
λ,λx,λy,λzand establishing a multiplier in an extreme function for the Lagrange multiplier method, wherein n is the number of nodes of the finite element model.
8. The three-dimensional model-based carrier rocket fatigue load assignment method according to claim 6, wherein the step 4) is a method for determining whether the aerodynamic fatigue load conversion algorithm of the carrier rocket meets the use requirements, and specifically comprises the following steps:
21) calculating the resultant force F and the resultant moment M of the pneumatic fatigue load relative to the mass center of the carrier rocket;
22) calculating the resultant force and resultant moment of the finite element load based on the mass center according to the force and moment of the fatigue load relative to the mass center in the three-dimensional finite element model;
23) obtaining a difference x1 between the resultant force of the pneumatic fatigue load and the resultant force of the finite element load, and obtaining a difference x2 between the resultant moment of the pneumatic fatigue load and the resultant moment of the finite element load;
24) if x1< 0.5% F, and x2< 0.5% M; judging that the pneumatic fatigue load conversion algorithm meets the use requirement; otherwise, judging that the pneumatic fatigue load conversion algorithm does not meet the use requirement.
CN202111435859.1A 2021-11-29 2021-11-29 Carrier rocket fatigue load assignment system and method based on three-dimensional model Pending CN114218823A (en)

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