Finite element modeling method and device for strut type undercarriage structure

Abstract

The invention provides a finite element modeling method and device for a strut type undercarriage structure, and the method comprises the steps: 1, building finite element models of a wheel fork, an inner cylinder, an outer cylinder and an anti-torsion arm of an undercarriage in a preset coordinate system through employing a tetrahedron entity unit TET10; and 2, connecting finite element models of a wheel fork, an inner cylinder, an outer cylinder and an anti-torsion arm by adopting a finite rigid body element, and setting the degree of freedom of a steel body element to obtain a finite element model of the undercarriage structure. More accurate component stress and connection load can be obtained, weak points of all components can be obtained, and weight reduction optimization work can be better carried out; compared with an engineering algorithm, the calculation accuracy is improved, and the time is saved; the key points and the method for finite element modeling of the undercarriage structure are provided, and the method is suitable for strength analysis of various strut type undercarriages.

Description

Technical Field

[0001] The invention belongs to the technical field of helicopter structural strength design, and in particular relates to a finite element modeling method and device for a strut-type landing gear structure. Background Art

[0002] The landing gear structure transfers the large loads during landing and ground operation to the fuselage, and is a key part of the helicopter. If the landing gear is designed too weak, it will affect the landing safety of the helicopter, and if it is designed too strong, it will cause unnecessary waste of weight. Therefore, how to effectively and quickly calculate the strength of the landing gear is very critical.

[0003] Traditional landing gear strength analysis generally simplifies the mechanical model of the landing gear and uses engineering algorithms to calculate the load at each point. Its disadvantages are: first, the calculation method is relatively complicated and time-consuming; second, the simplified calculation method does not match the actual load and can easily lead to load loss; third, it is not easy for engineering algorithms to find the weak points of components. Summary of the invention

[0004] The purpose of the present invention is to provide a finite element modeling method and device for a strut-type landing gear structure, by means of patran finite element analysis software, a detailed finite element model of the landing gear structure is established and the real force transmission is simulated and the real boundary conditions are applied, so as to obtain a more accurate landing gear strength calculation result.

[0005] A first aspect of the present invention provides a finite element modeling method for a strut-type landing gear structure, comprising:

[0006] Step 1: In the preset coordinate system, a finite element model of the wheel fork, inner tube, outer tube, and anti-torsion arm of the landing gear is established using the tetrahedron solid unit TET10;

[0007] Step 2: Use finite element rigid body elements to connect the finite element models of the wheel fork, inner tube, outer tube, and anti-torsion arm, and set the degrees of freedom of the steel body elements to obtain a finite element model of the landing gear structure.

[0008] Optionally, the finite element model of the wheel fork and the inner cylinder wall is connected through two RBE3 units and one BEAM unit, wherein a single point of one RBE3 unit only constrains Ux, Uy, Rx, and Ry, and releases the Uz and Rz degrees of freedom; the RBE3 unit belongs to the category of multi-point constraints in the finite element analysis software, and is used to realize the transmission of force from one node to multiple nodes, and the BEAM unit is a beam unit in the finite element software, and is used to realize the simulation of a straight segment structure whose cross section is a simple geometric shape;

[0009] The fork end face is connected to the inner tube shoulder by two RBE3 units and one BEAM unit, in which one RBE3 unit has a single point that only constrains Uz, and the rest of the degrees of freedom are released;

[0010] The lock pin is connected by two RBE2 units and one BEAM unit, where the single point of one RBE2 unit only constrains Ux and releases the remaining degrees of freedom; the RBE2 unit is a rigid unit in the finite element analysis software, which is used to connect the two parts into one;

[0011] The inner cylinder contacts the inner wall of the outer cylinder through two bushings. Each contact area is connected by two RBE3 units and one BEAM unit, in which a single point of one RBE3 unit only constrains Ux and Uy, and the other four degrees of freedom are released. The top of the inner cylinder is connected to the top of the outer cylinder through two RBE3 units and one BEAM unit, in which a single point of one RBE3 unit only constrains Uz, and the other degrees of freedom are released.

[0012] The anti-torsion arm is connected to the inner tube and outer tube ear pieces through the RBE2 unit and the BEAM unit, releasing the rotational freedom of the BEAM unit;

[0013] An RBE2 unit is established at the double ears where the outer tube is connected to the fuselage structure to constrain the Ux, Uy, and Uz degrees of freedom of the RBE2 single point; an RBE2 unit is established at the tube wall where the outer tube is connected to the fuselage structure to constrain the Ux and Uy degrees of freedom of the RBE2 single point.

[0014] Optionally, the axial direction of the inner cylinder is consistent with the Z-axis direction of the preset coordinate system, the axial direction of the wheel axle is consistent with the Y-axis direction of the preset coordinate system, and the reverse heading direction of the helicopter is consistent with the X-axis direction.

[0015] Optionally, Ux, Uy, Uz, Rx, Ry, and Rz are translational degrees of freedom and rotational degrees of freedom in x, y, and z directions, respectively.

[0016] A second aspect of the present invention provides a finite element modeling device for a strut-type landing gear structure, comprising:

[0017] A modeling unit is used to establish a finite element model of the wheel fork, inner tube, outer tube and anti-torsion arm of the landing gear in a preset coordinate system using a tetrahedral solid unit TET10;

[0018] The connection unit is used to connect the finite element models of the wheel fork, inner tube, outer tube and anti-torsion arm by using finite element rigid body elements, and to set the degrees of freedom of the steel body elements to obtain the finite element model of the landing gear structure.

[0019] Optionally, the finite element model of the wheel fork and the inner cylinder wall is connected through two RBE3 units and one BEAM unit, wherein a single point of one RBE3 unit only constrains Ux, Uy, Rx, and Ry, and releases the Uz and Rz degrees of freedom; the RBE3 unit belongs to the category of multi-point constraints in the finite element analysis software, and is used to realize the transmission of force from one node to multiple nodes, and the BEAM unit is a beam unit in the finite element software, and is used to realize the simulation of a straight segment structure whose cross section is a simple geometric shape;

[0020] The fork end face is connected to the inner tube shoulder by two RBE3 units and one BEAM unit, in which one RBE3 unit has a single point that only constrains Uz, and the rest of the degrees of freedom are released;

[0021] The lock pin is connected by two RBE2 units and one BEAM unit, where the single point of one RBE2 unit only constrains Ux and releases the remaining degrees of freedom; the RBE2 unit is a rigid unit in the finite element analysis software, which is used to connect the two parts into one;

[0022] The inner cylinder contacts the inner wall of the outer cylinder through two bushings. Each contact area is connected by two RBE3 units and one BEAM unit, in which a single point of one RBE3 unit only constrains Ux and Uy, and the other four degrees of freedom are released. The top of the inner cylinder is connected to the top of the outer cylinder through two RBE3 units and one BEAM unit, in which a single point of one RBE3 unit only constrains Uz, and the other degrees of freedom are released.

[0023] The anti-torsion arm is connected to the inner tube and outer tube ear pieces through the RBE2 unit and the BEAM unit, releasing the rotational freedom of the BEAM unit;

[0024] An RBE2 unit is established at the double ears where the outer tube is connected to the fuselage structure to constrain the Ux, Uy, and Uz degrees of freedom of the RBE2 single point; an RBE2 unit is established at the tube wall where the outer tube is connected to the fuselage structure to constrain the Ux and Uy degrees of freedom of the RBE2 single point.

[0025] Optionally, the axial direction of the inner cylinder is consistent with the Z-axis direction of the preset coordinate system, the axial direction of the wheel axle is consistent with the Y-axis direction of the preset coordinate system, and the reverse heading direction of the helicopter is consistent with the X-axis direction.

[0026] Optionally, Ux, Uy, Uz, Rx, Ry, and Rz are translational degrees of freedom and rotational degrees of freedom in x, y, and z directions, respectively.

[0027] The present invention provides a finite element modeling method and device for a strut-type landing gear structure. The method of the present invention can be used to analyze the landing gear to obtain more accurate component stress and connection load, and the weak points of each component can be obtained, which is more conducive to weight reduction optimization work; compared with calculations using engineering algorithms, the calculation accuracy is improved and time is saved; the key points and methods of finite element modeling of the landing gear structure are given, which is suitable for strength analysis of various strut-type landing gears. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the landing gear in the present invention;

[0029] Figure 2 This is a schematic diagram of the landing gear finite element model of the present invention. Figure 1 ;

[0030] Figure 3 This is a schematic diagram of the landing gear finite element model of the present invention. Figure 2 . DETAILED DESCRIPTION

[0031] The finite element modeling method and device for the strut-type landing gear structure provided by the present invention are explained below with reference to the accompanying drawings.

[0032] like Figure 1-3 The present invention provides a finite element modeling method for a strut-type landing gear structure, comprising the following contents:

[0033] [1] Define the coordinate system, where the positive X direction is the direction opposite to the heading of the helicopter, the positive Z direction is vertically upward along the axis of the inner cylinder, and the positive Y direction is along the wheel axis. The positive direction is determined by the right-hand rule.

[0034] [2] Analyze the correct load transmission path. The six load elements (Fx0, Fy0, Fz0, Mx0, My0, Mz0) from the wheel axle are transmitted to the wheel fork through the contact between the wheel axle and the wheel fork lug. Figure 1In the middle C area, the inner tube is inserted into the wheel fork, the end face of the wheel fork contacts the inner tube shoulder, and Fx0, Fy0, Mx0, and My0 on the wheel fork are transferred to the inner tube through the contact surface between the two. Fz0 on the wheel fork is transferred to the inner tube through the contact between the end face and the inner tube shoulder, and Mz0 on the wheel fork is transferred to the inner tube through the shearing of the locking pin; the inner tube contacts the outer tube through the bushing in the A and B areas, and Fx0 and Fy0 on the inner tube are directly transferred to the outer tube through the contact in the A and B areas, and Mx0 on the inner tube , My0 are transferred to the outer cylinder by converting into tensile and compressive loads at points A and B; Fz0 on the inner cylinder is transferred to the inner end surface of the top of the outer cylinder by the oil pressure in the outer cylinder cavity, and Mz0 on the inner cylinder is transferred to the outer cylinder through the anti-torsion arm; Fx0, Fy0, Fz0 and Mz0 can be transferred at the ear piece connecting the outer cylinder with the fuselage structure, and only Fx0 and Fy0 can be transferred at the wall connecting the outer cylinder with the fuselage structure, and Mx0 and My0 on the outer cylinder are transferred together by converting into tensile and compressive loads at the ear piece and the wall.

[0035] [3] The finite element model of each landing gear component was established, and the landing gear fork, inner tube, outer tube and anti-torsion arm were simulated using solid element TET10.

[0036] [4] The fork and the inner cylinder wall are connected by 2 RBE3 units and 1 BEAM unit, of which the single point of the RBE3 unit only constrains Ux, Uy, Rx, and Ry, and the Uz and Rz degrees of freedom are released; the fork end face and the inner cylinder shoulder are connected by 2 RBE3 units and 1 BEAM unit, of which the single point of the RBE3 unit only constrains Uz, and the other degrees of freedom are released; the lock pin is connected by 2 RBE2 units and 1 BEAM unit, of which the single point of the RBE2 unit only constrains Ux, and the other degrees of freedom are released. Figure 2 shown.

[0037] [5] The contact area between the inner cylinder and the outer cylinder at points A and B is connected by two RBE3 units and one BEAM unit, respectively. The single point of one RBE3 unit only constrains Ux and Uy, and the other four degrees of freedom are released. The top of the inner cylinder and the top of the outer cylinder are connected by two RBE3 units and one BEAM unit, and the single point of one RBE3 unit only constrains Uz, and the other degrees of freedom are released. Figure 2 shown.

[0038] [6] The anti-torsion arm is connected to the inner and outer tube ears through the RBE2 unit and the BEAM unit, releasing the rotational freedom of the BEAM unit.

[0039] [7] An RBE2 unit is established at the double ears where the outer tube is connected to the fuselage structure, and the Ux, Uy, and Uz degrees of freedom of the RBE2 single point are constrained; an RBE2 unit is established at the wall where the outer tube is connected to the fuselage structure, and the Ux and Uy degrees of freedom of the RBE2 single point are constrained.

[0040] [8] For different landing and ground conditions of the landing gear, the compression of the inner tube and the tire will change. The inner tube of the finite element model is in a free extension state. For different working conditions, different Mx0 and My0 caused by Fx0 and Fy0 will be added to the axle. The load on the axle is evenly distributed to the two wheel fork ears for loading. The strength result of the landing gear structure can be calculated, the weak parts of the landing gear structure can be obtained, and the connection load between the components can be obtained by reading the RBE3 unit node load.

[0041] The component models of the present invention are all established by using tetrahedron 10-node units, and the calculation results are more accurate than those of shell elements or 4-node units. The present invention simulates the real force transmission path by releasing the relevant degrees of freedom of the RBE3 units connecting the components. More accurate component stress and connection load can be obtained, and the weak points of each component can be obtained, which is more conducive to weight reduction optimization. Compared with calculations using engineering algorithms, the calculation accuracy is improved and time is saved. The key points and methods of finite element modeling of the landing gear structure are given, which is suitable for strength analysis of various strut-type landing gears.

Claims

1. A finite element modeling method for a strut-type landing gear structure, characterized in that: include: Step 1: In the preset coordinate system, a finite element model of the wheel fork, inner tube, outer tube, and anti-torsion arm of the landing gear is established using the tetrahedron solid unit TET10; Step 2: Use finite element rigid body elements to connect the finite element models of the wheel fork, inner tube, outer tube, and anti-torsion arm, and set the degrees of freedom of the steel body elements to obtain a finite element model of the landing gear structure.

2. The method according to claim 1, characterized in that The finite element model of the wheel fork and the inner cylinder wall is connected by two RBE3 units and one BEAM unit, in which the single point of one RBE3 unit only constrains Ux, Uy, Rx, and Ry, and releases the Uz and Rz degrees of freedom; the RBE3 unit belongs to the category of multi-point constraints in the finite element analysis software, and is used to realize the transmission of force from one node to multiple nodes. The BEAM unit is a beam unit in the finite element software, and is used to realize the simulation of a straight segment structure with a simple geometric shape in cross section; The fork end face is connected to the inner tube shoulder by two RBE3 units and one BEAM unit, in which one RBE3 unit has a single point that only constrains Uz, and the rest of the degrees of freedom are released; The lock pin is connected by two RBE2 units and one BEAM unit, where the single point of one RBE2 unit only constrains Ux and releases the remaining degrees of freedom; the RBE2 unit is a rigid unit in the finite element analysis software, which is used to connect the two parts into one; The inner cylinder contacts the inner wall of the outer cylinder through two bushings. Each contact area is connected by two RBE3 units and one BEAM unit, in which a single point of one RBE3 unit only constrains Ux and Uy, and the other four degrees of freedom are released. The top of the inner cylinder is connected to the top of the outer cylinder through two RBE3 units and one BEAM unit, in which a single point of one RBE3 unit only constrains Uz, and the other degrees of freedom are released. The anti-torsion arm is connected to the inner tube and outer tube ear pieces through the RBE2 unit and the BEAM unit, releasing the rotational freedom of the BEAM unit; An RBE2 unit is established at the double ears where the outer tube is connected to the fuselage structure to constrain the Ux, Uy, and Uz degrees of freedom of the RBE2 single point; an RBE2 unit is established at the tube wall where the outer tube is connected to the fuselage structure to constrain the Ux and Uy degrees of freedom of the RBE2 single point.

3. The finite element modeling method for a strut-type landing gear structure according to claim 1, characterized in that: The axial direction of the inner cylinder is consistent with the Z-axis direction of the preset coordinate system, the axial direction of the wheel axle is consistent with the Y-axis direction of the preset coordinate system, and the reverse heading direction of the helicopter is consistent with the X-axis direction.

4. The landing gear structure finite element modeling method according to claim 1, characterized in that: Ux, Uy, Uz, Rx, Ry, and Rz are the translational and rotational degrees of freedom in the x, y, and z directions respectively.

5. A finite element modeling device for a strut-type landing gear structure, characterized in that: include: A modeling unit is used to establish a finite element model of the wheel fork, inner tube, outer tube and anti-torsion arm of the landing gear in a preset coordinate system using a tetrahedral solid unit TET10; The connection unit is used to connect the finite element models of the wheel fork, inner tube, outer tube and anti-torsion arm by using finite element rigid body elements, and to set the degrees of freedom of the steel body elements to obtain the finite element model of the landing gear structure.

6. The device according to claim 5, characterized in that The finite element model of the wheel fork and the inner cylinder wall is connected by two RBE3 units and one BEAM unit, in which the single point of one RBE3 unit only constrains Ux, Uy, Rx, and Ry, and releases the Uz and Rz degrees of freedom; the RBE3 unit belongs to the category of multi-point constraints in the finite element analysis software, and is used to realize the transmission of force from one node to multiple nodes. The BEAM unit is a beam unit in the finite element software, and is used to realize the simulation of a straight segment structure with a simple geometric shape in cross section; The fork end face is connected to the inner tube shoulder by two RBE3 units and one BEAM unit, in which one RBE3 unit has a single point that only constrains Uz, and the rest of the degrees of freedom are released; The lock pin is connected by two RBE2 units and one BEAM unit, where the single point of one RBE2 unit only constrains Ux and releases the remaining degrees of freedom; the RBE2 unit is a rigid unit in the finite element analysis software, which is used to connect the two parts into one; The inner cylinder contacts the inner wall of the outer cylinder through two bushings. Each contact area is connected by two RBE3 units and one BEAM unit, in which a single point of one RBE3 unit only constrains Ux and Uy, and the other four degrees of freedom are released. The top of the inner cylinder is connected to the top of the outer cylinder through two RBE3 units and one BEAM unit, in which a single point of one RBE3 unit only constrains Uz, and the other degrees of freedom are released. The anti-torsion arm is connected to the inner tube and outer tube ear pieces through the RBE2 unit and the BEAM unit, releasing the rotational freedom of the BEAM unit; An RBE2 unit is established at the double ears where the outer tube is connected to the fuselage structure to constrain the Ux, Uy, and Uz degrees of freedom of the RBE2 single point; an RBE2 unit is established at the tube wall where the outer tube is connected to the fuselage structure to constrain the Ux and Uy degrees of freedom of the RBE2 single point.

7. The device according to claim 5, characterized in that The axial direction of the inner cylinder is consistent with the Z-axis direction of the preset coordinate system, the axial direction of the wheel axle is consistent with the Y-axis direction of the preset coordinate system, and the reverse heading direction of the helicopter is consistent with the X-axis direction.

8. The device according to claim 5, characterized in that Ux, Uy, Uz, Rx, Ry, and Rz are the translational and rotational degrees of freedom in the x, y, and z directions respectively.

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