An equivalent simplification method of finite element mass model of helicopter body

Abstract

The application belongs to the technical field of helicopter modeling, and particularly relates to a helicopter body finite element quality model equivalent simplification method. The method comprises the following steps: obtaining a helicopter quality list; distributing the quality of each element to two frame positions adjacent to the quality point according to the lever principle; creating a quality card of the finite element quality model for each frame position; reading the quality card and comparing each quality point with the position of the finite element node; according to the position of the quality point and the finite element node, merging and adjusting each quality point in the frame position according to a preset rule, and equivalently converting the quality and center of gravity of the frame position; and the above steps are repeated until the equivalent conversion of the quality and center of gravity of each frame position is completed, so that the helicopter body quality distribution calculation method is more accurate and the calculation efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of helicopter modeling technology, and in particular relates to an equivalent simplification method for a finite element mass model of a helicopter fuselage. Background Technology

[0002] Finite element modeling has become a well-known tool for structural strength analysis. In finite element modeling of helicopter fuselages, the finite element method typically delineates the main load-bearing structures of the fuselage, while the mass model of the fuselage needs to accurately simulate the mass distribution. In finite element analysis, the simplification of secondary load-bearing structures leads to a significant difference between the mass distribution and the actual total mass. Therefore, reasonable simplification is necessary in finite element analysis to accurately simulate the mass distribution. Currently, there are many articles on finite element analysis in China, but few on the stress model of the entire helicopter, and even fewer on a finite element model of the entire helicopter including mass attributes.

[0003] Typically, allocating the total mass distribution data of a helicopter into a finite element model is done manually. This process is extremely time-consuming and becomes impractical as the scale and complexity of finite element analyses increase. For example, in the total mass distribution of a four-ton helicopter, the empty mass alone contains thousands or more mass distribution elements. Therefore, the equivalent transformation process of the finite element mass model becomes very complex and labor-intensive. Thus, it is necessary to refine, streamline, and standardize the method for calculating the total mass distribution of helicopters to improve the efficiency and accuracy of finite element model creation. Summary of the Invention

[0004] The purpose of this invention is to design a process and algorithm for equivalently allocating a large amount of overall aircraft mass distribution data to the material density and nodal data in a helicopter fuselage finite element model. This algorithm can quickly discretize a large amount of data into specified fuselage frame locations through mathematical calculations. In each frame location of the finite element model, the mass distribution data is accurately equivalently allocated to the finite element model using density (scaling adjustment factor), lumped mass node data, or a combination of both. This makes the helicopter fuselage mass allocation calculation method more accurate and improves computational efficiency.

[0005] The technical solution of the present invention:

[0006] An equivalent simplification method for a finite element mass model of a helicopter fuselage, the method comprising:

[0007] S1, Obtain the helicopter mass list, which includes the mass of each component, the heading center of gravity coordinates, the lateral center of gravity coordinates, and the vertical center of gravity coordinates, as well as the total weight of the entire aircraft, the heading center of gravity coordinates, the lateral center of gravity coordinates, and the vertical center of gravity coordinates of the entire aircraft.

[0008] S2, according to the lever principle, the mass of each component is equivalently distributed to the two frame occupants adjacent to the mass point;

[0009] S3. For each frame space, create a mass card for the finite element mass model. The mass card records the mass and three-dimensional coordinates of each mass point within the frame space.

[0010] S4, read in the mass card and compare the position of each mass point with the position of the finite element node;

[0011] S5. Based on the positions of the mass points and finite element nodes, and according to preset rules, each mass point within the frame is merged and adjusted to perform an equivalent transformation of the mass and center of gravity of the frame.

[0012] S6, repeat S3-S5 until the quality of each box place and the equivalent transformation of the center are completed.

[0013] Furthermore, the feature is that S1 specifically comprises:

[0014] The helicopter mass list includes the mass m of the i-th component. i The heading and barycenter coordinates x of the i-th node i The lateral centroid coordinate y of the i-th element i And the vertical centroid coordinate z of the i-th one. i It also includes the total weight M0 of the aircraft and the heading center of gravity coordinates x0, lateral center of gravity coordinates y0 and vertical center of gravity coordinates z0 of the aircraft. The center of gravity coordinate values ​​are all the center of gravity position values ​​in the overall coordinate system of the aircraft, i = 1, ..., I, where I is the total number of components.

[0015] Furthermore, S2 specifically refers to:

[0016] According to the lever principle, the mass of each element is equivalently allocated to the i-th frame and the (i+1)-th frame adjacent to the mass point;

[0017]

[0018]

[0019] m m(i) The equivalent mass of the i-th element, m, allocated to the i-th frame space, m m(i+1) The equivalent mass of the i-th element, m, allocated to the (i+1)-th frame space, m m(i) With m m(i+1) The lateral and vertical coordinates remain unchanged.

[0020] Furthermore, after S2, the method further includes:

[0021] Calculate the overall theoretical centroid CG0 and the overall theoretical weight M of the i-th frame.

[0022] Furthermore, S5 specifically refers to:

[0023] For mass points whose distance from the finite element node is less than or equal to 0.5 mm, the mass point is directly merged with the corresponding finite element node.

[0024] Furthermore, S5 specifically refers to:

[0025] S51: Output and delete mass points whose distance from the finite element node is greater than 0.5mm;

[0026] S52, obtain the actual material density of each box occupant, and calculate the centroid CG of the finite element model for each box occupant under the actual material density value. FEM ;

[0027] S53, Obtain the centroid CG of the finite element model with the placeholder box at the actual material density value. FEM The distance L from the centroid CG0 of the overall theory occupied by this frame;

[0028] S54, determine the mass point for adjusting the center of gravity, and measure the distance L between the theoretical center of gravity CG0 of the overall frame positioning and the mass point for adjusting the center of gravity. max ;

[0029] S55, calculate the mass of the mass point for adjusting the center of gravity and the material density adjustment coefficient.

[0030] Furthermore, in S54, the specific mass point for determining the center of gravity is as follows:

[0031] Determine the placeholder frame for the centroid CG of the finite element model at the actual material density. FEM Draw a line connecting the center of gravity CG0 of the overall theory of the frame occupant, and extend the line to the intersection point with the finite element model. This intersection point serves as the mass point for adjusting the center of gravity.

[0032] Furthermore, the S55 specifically refers to:

[0033] Adjust the mass of the center of gravity.

[0034] Material density adjustment coefficient

[0035] This invention utilizes the density of structural elements in a scaling frame placeholder sub-model to incorporate non-structural mass into the structural mass within the sub-model. This improves efficiency. Furthermore, the method of adding mass elements to nodes for center-of-gravity adjustment makes the helicopter fuselage mass distribution calculation more accurate. The mathematically-based equivalent distribution method accurately reflects the overall mass distribution of the helicopter, ensuring the accuracy of the strength calculation process. Attached Figure Description

[0036] Figure 1 These are the distribution points of a large number of helicopter empty weights;

[0037] Figure 2 Flowchart for mathematical analysis of mass points;

[0038] Figure 3 Schematic diagram for mathematical analysis of mass points;

[0039] Figure 4 Execution procedure diagram for mathematical analysis of mass points;

[0040] Figure 5 A distribution diagram of mass points discretized to a frame using mathematical analysis methods;

[0041] Figure 6 A comparison diagram of the distribution of mass points occupying a certain frame and the nodes of a finite element method.

[0042] Figure 7 The density coefficient and mass element are adjusted to define a placeholder for a certain frame. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and examples. The described embodiments are only a part of the examples of this invention, and not all of them.

[0044] This invention provides a process and algorithm for equivalently allocating a large amount of overall aircraft mass point data to the material density and nodal data in a helicopter fuselage finite element model. This makes the mass allocation calculation method in the helicopter fuselage finite element model more accurate and effectively solves the problems of large workload, time consumption, and low efficiency in existing technologies.

[0045] This invention provides an equivalent simplification method for a finite element mass model of a helicopter fuselage, the method comprising:

[0046] S1, Obtain the helicopter mass list, which includes the mass of each component, the heading center of gravity coordinates, the lateral center of gravity coordinates, and the vertical center of gravity coordinates, as well as the total weight of the entire aircraft, the heading center of gravity coordinates, the lateral center of gravity coordinates, and the vertical center of gravity coordinates of the entire aircraft.

[0047] S1 specifically refers to:

[0048] The helicopter mass list includes the mass m of the i-th component. i The heading and barycenter coordinates x of the i-th node i The lateral centroid coordinate y of the i-th element i And the vertical centroid coordinate z of the i-th one. i It also includes the total weight M0 of the aircraft and the heading center of gravity coordinates x0, lateral center of gravity coordinates y0 and vertical center of gravity coordinates z0 of the aircraft. The center of gravity coordinate values ​​are all the center of gravity position values ​​in the overall coordinate system of the aircraft, i = 1, ..., I, where I is the total number of components.

[0049] S2, according to the lever principle, the mass of each component is equivalently distributed to the two frame occupants adjacent to the mass point;

[0050] S2 specifically refers to:

[0051] According to the lever principle, the mass of each element is equivalently allocated to the i-th frame and the (i+1)-th frame adjacent to the mass point;

[0052]

[0053]

[0054] m m(i) The equivalent mass of the i-th element, m, allocated to the i-th frame space, m m(i+1) The equivalent mass of the i-th element, m, allocated to the (i+1)-th frame space, m m(i) With m m(i+1) The lateral and vertical coordinates remain unchanged.

[0055] Following S2, the method further includes:

[0056] Calculate the overall theoretical centroid CG0 and the overall theoretical weight M of the i-th frame.

[0057] S3. For each frame space, create a mass card for the finite element mass model. The mass card records the mass and three-dimensional coordinates of each mass point within the frame space.

[0058] S4, read in the mass card and compare the position of each mass point with the position of the finite element node;

[0059] S5. Based on the positions of the mass points and finite element nodes, and according to preset rules, each mass point within the frame is merged and adjusted to perform an equivalent transformation of the mass and center of gravity of the frame.

[0060] S5 specifically refers to:

[0061] For mass points whose distance from the finite element node is less than or equal to 0.5 mm, the mass point is directly merged with the corresponding finite element node.

[0062] S5 specifically refers to:

[0063] S51: Output and delete mass points whose distance from the finite element node is greater than 0.5mm;

[0064] S52, obtain the actual material density of each box occupant, and calculate the centroid CG of the finite element model for each box occupant under the actual material density value. FEM ;

[0065] S53, Obtain the centroid CG of the finite element model with the placeholder box at the actual material density value. FEM The distance L from the centroid CG0 of the overall theory occupied by this frame;

[0066] S54, determine the mass point for adjusting the center of gravity, and measure the distance L between the theoretical center of gravity CG0 of the overall frame positioning and the mass point for adjusting the center of gravity. max ;

[0067] S55, calculate the mass of the mass point for adjusting the center of gravity and the material density adjustment coefficient.

[0068] In S54, the specific mass point for determining the center of gravity is as follows:

[0069] Determine the placeholder frame for the centroid CG of the finite element model at the actual material density. FEM Draw a line connecting the center of gravity CG0 of the overall theory of the frame occupant, and extend the line to the intersection point with the finite element model. This intersection point serves as the mass point for adjusting the center of gravity.

[0070] S55 specifically refers to:

[0071] Adjust the mass of the center of gravity.

[0072] Material density adjustment coefficient

[0073] S6, repeat S3-S5 until the quality of each box place and the equivalent transformation of the center are completed.

[0074] The following is combined with Figures 1 to 7 Further explanation of this application is provided.

[0075] This invention provides a process and algorithm for equivalently allocating a large amount of overall aircraft mass point scatter data to a helicopter fuselage finite element model. Figure 1 This is a scatter plot of the total mass of a helicopter in one embodiment.

[0076] The block diagram for calculating the equivalent mass distribution of the entire helicopter in the finite element model is shown below. Figure 2 As shown, the implementation method is explained step by step with an example below:

[0077] Step 1: Obtain the helicopter's empty state mass list. The mass list includes multiple mass individuals, the coordinates of each mass individual, and the center of gravity position of the empty mass. For example, an excerpt of the mass list is shown in the table below:

[0078] Table 1

[0079]

[0080]

[0081] Step 2: Using mathematical analysis and the lever principle, the mass m of each component on the helicopter empty mass list is equivalently distributed to the two boxes adjacent to that mass point using the following formulas. The mathematical calculation methods are shown in Formulas 1 and 2, and the principle is explained in [the original text is missing]. Figure 3 As shown, in this embodiment, the above mathematical calculations are performed using a program for analysis. Figure 4 ;

[0082] Step 3: Create a mass card for the finite element software. In this embodiment, the CONM2 card from the PATRAN finite element analysis software is used. After the analysis and calculation in the above steps, all scattered mass points are distributed to the mass points in each sub-model of the frame. Figure 5 ;

[0083] Step 4: Read in the mass card and perform a positional comparison analysis between the mass points and finite element nodes. In this example, one sub-placement is selected in frame 4. The comparison relationship between the mass points and nodes is shown in [link to example]. Figure 6 Points with a distance of 0.5 mm or less are directly merged; in the main interface of PATRAN finite element software, the CONM2 card is imported through the file-import function, and then the Equivalencing Tolerance is set to 0.05 in Element-equivalence-list in the main interface before merging.

[0084] Step 5.1: In the finite element analysis software, output and delete mass elements for mass points with a distance greater than 0.5 mm. In this example, the Element-Delete function in the PATRAN main interface is used.

[0085] Step 5.2: Fill in the material density of each box and calculate the centroid CG of the finite element model for each box under the actual material density value. FEMIn this example, we will use the Tool-Mass Property function in the PATRAN main interface, taking 4 boxes as an example.

[0086] Step 5.3, based on the centroid CG of the finite element of the calculation frame. FEM The distance L to the centroid CG0 of the overall theory is shown in Figure 7 in this example.

[0087] Step 5.4, from the centroid CG of the finite element FEM Draw a line connecting to CG0 and extend it. The intersection point of this line with the finite element model is taken as the mass point for adjusting the center of gravity. Measure the distance L between the theoretical center of gravity of CG0 and the center of gravity of the adjusting mass element in the finite element Patran software. max In this example, L max See Figure 7;

[0088] Step 5.5: Calculate the mass of the locally adjusted mass element using Formula 3;

[0089] Step 5.6: Calculate the material density scaling adjustment factor using Formula 4;

[0090] Step 6: Repeat the previous step for each frame of the fuselage to achieve equivalent transformation of the sub-model mass and center of gravity of each frame. Finally, check the weight and center of gravity of the whole machine. The verification of this example is shown in Table 2. When the error between the weight center of gravity of the simplified finite element model and the weight center of gravity of the whole machine in the overall mass distribution is within 1%, the finite element model simplification is completed.

[0091] Table 2

[0092]

[0093] This invention provides a process and algorithm for equivalently allocating a large amount of overall aircraft mass point data to the material density and nodal data in a helicopter fuselage finite element model. This makes the mass allocation calculation method in the helicopter fuselage finite element model more accurate and effectively solves the problems of large workload, time consumption, and low efficiency in existing technologies.

[0094] In summary, the above are merely embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, or improvements made within the principles of the present invention are included within the scope of protection of the present invention.

Claims

1. An equivalent simplification method for a finite element mass model of a helicopter fuselage, characterized in that, The method includes: S1, Obtain the helicopter mass list, which includes the mass of each component, the heading center of gravity coordinates, the lateral center of gravity coordinates, and the vertical center of gravity coordinates, as well as the total weight of the entire aircraft, the heading center of gravity coordinates, the lateral center of gravity coordinates, and the vertical center of gravity coordinates of the entire aircraft. S2, according to the lever principle, the mass of each component is equivalently distributed to the two frame occupants adjacent to the mass point; S3. For each frame space, create a mass card for the finite element mass model. The mass card records the mass and three-dimensional coordinates of each mass point within the frame space. S4, read in the mass card and compare the position of each mass point with the position of the finite element node; S5, based on the positions of the mass points and finite element nodes, and according to preset rules, merges and adjusts each mass point within the frame's occupancy, performing an equivalent transformation of the frame's mass and center of gravity; S5 specifically involves: S51: Output and delete mass points whose distance from the finite element node is greater than 0.5mm; S52, obtain the actual material density of each box occupant, and calculate the centroid CG of the finite element model for each box occupant under the actual material density value. FEM ; S53, Obtain the centroid CG of the finite element model with the placeholder box at the actual material density value. FEM The distance L from the centroid CG0 of the overall theory occupied by this frame; S54, determine the mass point for adjusting the center of gravity, and measure the distance L between the theoretical center of gravity CG0 of the overall frame positioning and the mass point for adjusting the center of gravity. max In S54, the specific mass point for determining the center of gravity is as follows: Determine the placeholder frame for the centroid CG of the finite element model at the actual material density. FEM Draw a line connecting the center of gravity CG0 of the overall theory of the frame occupant, and extend the line to the intersection point with the finite element model. This intersection point serves as the mass point for adjusting the center of gravity. S55, calculate the mass of the mass point for adjusting the center of gravity and the material density adjustment coefficient; S6, repeat S3-S5 until the quality of each box place and the equivalent transformation of the center are completed.

2. The equivalent simplification method for a finite element mass model of a helicopter fuselage according to claim 1, characterized in that, S1 specifically refers to: The helicopter mass list includes the mass of the i-th component. The coordinates of the heading barycenter of the i-th node The lateral centroid coordinates of the i-th element and the vertical centroid coordinates of the i-th element. This also includes the total weight of the entire machine. and the coordinates of the aircraft's heading and center of gravity. Lateral centroid coordinates and vertical centroid coordinates The center of gravity coordinates are all the center of gravity position values ​​in the overall coordinate system of the machine body, i=1,…,I, where I is the total number of components.

3. The equivalent simplification method for a finite element mass model of a helicopter fuselage according to claim 2, characterized in that, S2 specifically refers to: According to the lever principle, the mass of each element is equivalently allocated to the i-th frame and the (i+1)-th frame adjacent to the mass point; The equivalent mass of the i-th element, m, allocated to the i-th frame space. The equivalent mass of the i-th element, m, is allocated to the (i+1)-th frame space. and The lateral and vertical coordinates remain unchanged.

4. The equivalent simplification method for a finite element mass model of a helicopter fuselage according to claim 3, characterized in that, Following S2, the method further includes: Calculate the overall theoretical centroid CG0 and the overall theoretical weight M of the i-th frame.

5. The equivalent simplification method for a finite element mass model of a helicopter fuselage according to claim 3, characterized in that, S5 specifically refers to: For mass points whose distance from the finite element node is less than or equal to 0.5 mm, the mass point is directly merged with the corresponding finite element node.

6. The equivalent simplification method for a finite element mass model of a helicopter fuselage according to claim 4, characterized in that, S55 specifically refers to: Adjust the mass of the center of gravity. Material density adjustment coefficient .

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