A Calculation Method for Aircraft Mass Distribution Based on Finite Element Model

Abstract

A method for calculating aircraft mass distribution based on a finite element model is disclosed. The total aircraft mass includes structural mass and non-structural mass. A finite element model of the aircraft is established based on a design digital model of the aircraft structure, and the structural mass characteristics of the aircraft are obtained based on the finite element model. The segmented mass distribution characteristics of the aircraft, including the distribution characteristics of the structural mass and non-structural mass, are obtained based on a total mass distribution report of the aircraft design. The finished product mass in the non-structural mass is added to the aircraft finite element model as a concentrated mass according to its installation position. The remaining non-structural mass is segmented according to its location, and the distance between the center of mass of each segment and the node of the finite element model is used as a control parameter of the Gaussian distribution, and the non-structural mass is calculated at the nodes of the finite element model according to the Gaussian distribution.

Description

Technical Field

[0001] The present application relates to aircraft design strength calculation technology, specifically a method for calculating aircraft mass distribution based on a finite element model. Background Art

[0002] In aircraft design, the aircraft's mass distribution includes: the distribution of structural mass characteristics of large components, such as along the span of the wings (or tail) and the length of the fuselage; the distribution of fuel mass, the distribution of passenger and cargo mass, and the distribution of internal cable and conduit mass; and the mass of finished components, such as engines, landing gear, and bombs. These various mass distributions collectively contribute to the aircraft's mass characteristics, such as mass, center of mass, moment of inertia about the center of mass, and product of inertia. The calculation and design of aircraft mass distribution generally employ unique methods, such as computational estimation, statistics, experimental weighing correction, and physical cutting (disassembly) and weighing. Aircraft mass distribution data is the most fundamental design data for the aircraft's flight qualities, performance, strength, and stiffness.

[0003] The iterative process of aircraft design refinement dictates that the aircraft's mass distribution must be an iterative update process. Calculating an aircraft's mass distribution is an independent discipline, and its calculation methods and models are independent of the models and methods used in other aircraft design disciplines. With the advancement of computer simulation technology, particularly finite element structural analysis, aircraft load, strength, and stiffness design techniques are becoming increasingly integrated, with increasingly unified calculation models and methods. Coordinating aircraft mass distribution data with the mass distribution of the structural finite element model has become a major technical challenge in aircraft structural strength design.

[0004] The current method for calculating aircraft mass distribution uses a segmented (along wing ribs and fuselage frames) mass distribution model. This model condenses the structure, fuel, and payload into one or more mass points within a specific segment (or local area), providing the mass, center of mass, moment of inertia about the center of mass, and product of inertia of each point. Finished components such as engines, landing gear, and bombs are simplified to one or more mass points. This mass model matches the traditional engineering beam theory model and has dominated traditional aircraft load, vibration, strength, and stiffness design.

[0005] With the advancement of structural finite element technology, structural design has become increasingly sophisticated. Aircraft mass is divided into structural mass and non-structural mass. Structural loads (internal forces and stresses) can only be borne by the specific force-transmitting structure. The mass distribution of the force-transmitting structure is determined by the structural finite element model and is referred to as structural mass. The remaining mass is referred to as non-structural mass. The inertial distributed force or concentrated inertial force generated by the non-structural mass acts on the force-transmitting structure. Its force field properties differ from those of the inertial distributed force generated by the structural mass, and their modes of action are not entirely consistent. Currently available aircraft mass distribution calculation models do not consider the required characteristics of the structural finite element model (doing so would be prohibitively expensive and unrealistic). Therefore, reconciling the aircraft mass distribution data with the mass distribution of the structural finite element model is an unavoidable technical challenge. If structural and non-structural masses are treated the same without considering specific realities and ignoring their differences in force-transmitting characteristics, structural stress calculation deviations will occur, leading to structural design errors or significantly increasing the workload of subsequent supplementary design. Summary of the Invention

[0006] The present invention aims to provide a method for calculating aircraft mass distribution based on a finite element model. The method rationally distributes the mass distribution characteristics of the aircraft along structural segments (along wing ribs and fuselage frames) to the nodes of the aircraft structure finite element model, forming a mass distribution based on the finite element model, and maintaining the mass distribution of the two models in a coordinated and consistent manner. The overall mass characteristics of the aircraft, such as mass, center of mass, moment of inertia about the center of mass, and product of inertia, remain the same.

[0007] A method for calculating aircraft mass distribution based on a finite element model, wherein the total aircraft mass includes structural mass and non-structural mass, is characterized by comprising the following: 1) establishing an aircraft finite element model based on a design digital model of the aircraft structure, and obtaining the structural mass characteristics of the aircraft based on the finite element model; 2) obtaining the aircraft segmented mass distribution characteristics, including the structural mass and non-structural mass distribution characteristics, based on a total aircraft design mass distribution report; 3) attaching the finished product mass in the non-structural mass to the aircraft finite element model as a concentrated mass according to its installation position; and segmenting the remaining non-structural mass according to its location. The distance between the center of mass of each segment and a node of the finite element model is used as a control parameter of a Gaussian distribution, and the non-structural mass is calculated at the nodes of the finite element model according to the Gaussian distribution.

[0008] The beneficial effects of the present invention are: (1) the mass distribution of the finite element model is consistent with the mass distribution data model of the aircraft segment (along the wing ribs and fuselage frame), and the overall mass characteristics of the aircraft, such as mass, center of mass, moment of inertia about the center of mass, and product of inertia, maintain optimal compliance, thereby obtaining a higher-level aircraft mass distribution model; (2) the structural finite element model naturally simulates the aircraft stiffness, and combined with the aircraft finite element mass model that fits the actual situation, an optimal aircraft vibration characteristic calculation model is obtained, which provides a more solid design foundation for the aircraft's vibration characteristic design, flutter design, deformation prediction and load design; (3) the application of inertial force and fuel tank fuel pressure is more reasonable, which is conducive to improving the quality of aircraft structural strength design and enhancing the safety of the aircraft platform.

[0009] The following is a further detailed description of the present application in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is the finite element model of the aircraft nose section. 1 is the aircraft nose; 2 is the finished radar, which is attached to the finite element model as a concentrated mass; 3 is the finite element structural model of the fuselage frame; 4 is the finite element model node; 5 is the radar door frame; the radar door is not included in the finite element model.

[0011] Figure 2 This is the mass distribution data model of the aircraft head segment (along the fuselage frame). 6 is the aircraft head frame segment, and 7 is the mass point of each frame segment.

[0012] Figure 3 This is an example of the mass distribution of the finite element model of the aircraft nose section. Figure 3 The data corresponding to the "Quality Model (Control Target)" row must be the data provided by the aircraft weight design department. DETAILED DESCRIPTION

[0013] The aircraft mass distribution calculation method based on the finite element model of the present application is characterized in that the total aircraft mass includes structural mass and non-structural mass, and includes the following contents: 1) establishing an aircraft finite element model based on the design digital model of the aircraft structure, and obtaining the structural mass characteristics of the aircraft based on the finite element model; 2) obtaining the aircraft segmented mass distribution characteristics, including the structural mass and non-structural mass distribution characteristics, based on the total mass distribution report of the aircraft design; 3) attaching the finished product mass in the non-structural mass to the aircraft finite element model as a concentrated mass according to its installation position; dividing the remaining non-structural mass into segments according to their locations, and using the distance from the center of mass of each segment to the node of the finite element model as the control parameter of the Gaussian distribution, and calculating the Gaussian distribution at the node of the finite element model.

[0014] The aircraft mass distribution calculation method based on the finite element model is characterized in that, in step 1), the aircraft finite element model is segmented according to the aircraft mass distribution report, the nodes and position coordinates of the structural finite element model contained in each segment are clarified, and the aircraft structural mass characteristics are obtained.

[0015] The aircraft mass distribution calculation method based on the finite element model is characterized in that the non-structural mass characteristics at each segment corresponding to the finite element model node are calculated based on the aircraft total mass distribution characteristics and the aircraft structural mass characteristics.

[0016] The aircraft structural finite element model is established according to the actual structure of the aircraft, so the mass model of the structural finite element model is a collection of mass points with model nodes as the model nodes. The mass of the actual force-transmitting structure of the finite element model is simplified to the model nodes, that is, the structural mass. The known non-structural mass attached to the specific force-transmitting structure can also be simplified to the model nodes.

[0017] The aircraft segmented mass distribution characteristic data model obtained based on the overall mass distribution report of the aircraft design is a discrete mass model of structural geometric segments with properties such as mass, center of mass, moment of inertia about the center of mass, and product of inertia, obtained by dividing the continuous structure into small area segments. It contains non-structural mass, structural mass, and finished product mass.

[0018] The difference between the mass distribution of the aircraft segment (along the wing ribs and fuselage frame) mass distribution data model and the structural mass distribution of the finite element model is the non-structural mass and finished product mass of the aircraft.

[0019] The composition of the nodes in the finite element model can be adjusted to better fit the actual force transmission path.

[0020] To clarify the technical solutions implemented by the present invention, embodiments of the present invention are described with reference to the accompanying tables and figures. Taking the nose section of an aircraft as an example, the nose section 1 typically houses a finished radar 2, which has a significant opening. The radar is a finished product connected to the aircraft via a mounting bracket. The radar and the hatch with the structural opening are typically non-structural masses and do not constitute the aircraft's load-bearing structure.

[0021] First, establish the finite element structure model of the aircraft head. Figure 1 According to the geometric area division regulations of the mass model, the nodes and geometric positions of the structural finite element model contained in the nose segment are found on the structural finite element model. The coordinates and mass of the structural nodes of the nose segment are obtained using the finite element analysis software. After integration and summation, its mass, center of mass and inertia can be obtained. Figure 3 The corresponding row data of "Finite Element Model Structure".

[0022] Then, the aircraft head section mass distribution characteristic data model is obtained based on the aircraft design total mass distribution report, see Figure 2. Figure 2 In the figure, 6 represents the aircraft head frame segment, and 7 represents the mass point of each frame segment. By dividing the continuous aircraft head structure into small segments, a discrete mass model of the structural geometry segment is obtained, which has properties such as mass, center of mass, moment of inertia about the center of mass, and product of inertia. This mass model includes nonstructural mass, structural mass, and finished product mass.

[0023] Figure 3 The row corresponding to "Mass Model (Control Target)" contains the aircraft nose section mass characteristic data specified by the aircraft weight reporting model. This value is significantly larger than that of the finite element structural model. It includes all masses and serves as the control target for the calculation. The center of mass is calculated from the difference between this row and the previous row (non-structural mass, including finished product mass).

[0024] The finished product mass in the non-structural mass is attached as a concentrated mass to the nodes of the aircraft finite element model according to its installation position.

[0025] Then, the calculation method described in technical solution 3) of this specification is used to calculate the mass of each finite element model node corresponding to the non-structural mass.

[0026] Add the mass distribution of each finite element model node corresponding to all non-structural masses and the mass distribution of the nodes of the finite element model bearing structure to calculate the finite element model node distribution corresponding to the "mass model (control target)". After integration and summation, its mass and center of mass can be obtained. Figure 3 The corresponding row data of "Finite element model mass distribution (calculated value)".

Claims

1. A method for calculating aircraft mass distribution based on a finite element model, wherein the total mass of the aircraft includes structural mass and non-structural mass, characterized in that The method includes the following contents: 1) establishing an aircraft finite element model according to a design digital model of the aircraft structure, and obtaining the structural mass characteristics of the aircraft according to the finite element model; 2) obtaining the segmented mass distribution characteristics of the aircraft according to the total mass distribution report of the aircraft design, including the distribution characteristics of the structural mass and the non-structural mass; 3) attaching the finished product mass in the non-structural mass to the aircraft finite element model as a concentrated mass according to its installation position; dividing the remaining non-structural mass into segments according to their positions, and using the distance from the center of mass of each segment of the non-structural mass to the node of the finite element model as a control parameter of the Gaussian distribution, and calculating the non-structural mass at the node of the finite element model according to the Gaussian distribution.

2. The method for calculating aircraft mass distribution based on a finite element model according to claim 1, wherein: In step 1), the aircraft finite element model is segmented according to the aircraft mass distribution report, the nodes and position coordinates of the structural finite element model included in each segment are clarified, and the aircraft structural mass characteristics are obtained.

3. The method for calculating aircraft mass distribution based on a finite element model according to claim 1, wherein: The non-structural mass characteristics of each segment at the finite element model node are calculated based on the total mass distribution characteristics and the aircraft structural mass characteristics.

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