An aircraft tooling base thickness evaluation method based on force value feedback

Abstract

This invention discloses a method for evaluating the thickness of aircraft tooling foundations based on force feedback. It includes the following steps: establishing a reasonably simplified finite element model of the tooling jig; establishing reasonably simplified mechanical boundary conditions; finite element simulation calculation; and establishing a foundation thickness evaluation method. This method can consider factors such as the thickness of the tooling-specific foundation, the tooling geometry, the tooling material type, support angles and ground friction, force and moment balance, etc., to calculate and evaluate whether the foundation thickness of large aircraft tooling can meet the requirements for resisting deformation under the tooling's own weight. Combined with the established evaluation method, it can optimize the design of tooling foundation thickness, further improve the stability of large aircraft tooling foundations, and prevent the decrease in tooling accuracy caused by insufficient foundation thickness design. It is a fast and effective evaluation calculation method.

Description

Technical Field

[0001] This invention relates to a method for evaluating the thickness of aircraft tooling foundations based on force feedback, specifically an evaluation method for whether the foundation thickness of large aircraft tooling can meet the requirements for resisting deformation due to the tooling's own weight. Background Technology

[0002] During aircraft assembly, the assembly system undergoes a dynamic change over time due to variations in the tooling foundation. Non-uniform changes in the tooling foundation directly impact the stability of the assembly jig, thereby reducing assembly accuracy and efficiency. To prevent assembly accuracy degradation caused by non-uniform settlement, dedicated tooling foundations of a certain thickness are required in the factory. However, increasing the thickness of these foundations significantly increases construction costs. Therefore, an evaluation method is needed that considers factors such as foundation thickness, tooling geometry, tooling material type, support angles and ground friction, force and moment balance, and the evolution of foundation deformation with load magnitude and time. This method calculates whether the foundation thickness for large aircraft tooling is sufficient to resist deformation under its own weight, thus evaluating whether the foundation thickness meets requirements. Based on the calculation results, the tooling thickness can be optimized to further improve the stability of large aircraft tooling foundations and prevent accuracy degradation due to insufficient foundation thickness. Traditional calculation and evaluation methods require constitutive equations to describe the mechanical properties of tooling foundations. However, constitutive equations contain a large number of influencing parameters, which require extensive laboratory measurement data and cannot be directly used for rapid engineering calculations. Summary of the Invention

[0003] To address the aforementioned issues, this invention establishes a method for evaluating the thickness of aircraft tooling foundations based on force feedback using the finite element method.

[0004] The technical solution of this invention is: a method for evaluating the thickness of aircraft tooling foundations based on force feedback, comprising the following steps: Step 1: Establish a reasonably simplified finite element model of the tooling fixture. The specific process is as follows: 1-1 A three-dimensional geometric model of the large aircraft assembly tooling was established using CAD software. All parts except the upper beam, frame column, bottom beam, and support corners were deleted from the aircraft assembly tooling model to create a simplified model. The simplified model was made to ensure that the length, width, and height of the original aircraft tooling were the same as those of the original aircraft tooling. The position and size of the support corners at the bottom of the tooling in the simplified model were consistent with those of the original aircraft tooling. 1-2 Build a ground model below the simplified model. The length and width of the ground model should be no less than 1.2 times the length and width of the actual aircraft tooling, and the height should be equal to the actual factory foundation height.

[0005] Step two involves establishing reasonably simplified mechanical boundary conditions, the specific process of which is as follows: 2-1 Adjust the material density of the tooling finite element model according to Formula 1 (1) in, The material density in the finite element model; The actual material density of the aircraft tooling; The actual quality of aircraft tooling; For the quality of the finite element model; 2-2 Based on the type of aircraft tooling material, set the Young's modulus and Poisson's ratio of the actual aircraft tooling; the Young's modulus of the ground material is 20 times that of the actual aircraft tooling, and the Poisson's ratio is the same as that of concrete material; 2-3 Set constraints at the bottom of the ground model to limit 6 degrees of freedom; provide support force from the friction between the support corner and the ground in the simplified tooling model, and give the friction coefficient between the two. Step 3: Finite element simulation calculation. The specific process is as follows: 3-1 Mesh Generation: The maximum dimensions of the mesh cells in the ground model and simplified model shall not exceed 1% of the length, width, and height of the aircraft tooling; 3-2 In the finite element method software, a gravity load is applied and the statics module is used to calculate the displacement and stress fields of the aircraft tooling under its own weight, obtaining the maximum vertical displacement of the support angle under normal working conditions. .

[0006] Step four establishes a basic thickness evaluation method, the specific process of which is as follows: 4-1 The vertical support reaction force of the ground in the ground model on any support corner in the simplified model is obtained by integrating the contact stress using Formula 2.

[0007] (2) in, Let be the stress component along the vertical direction of a mesh element. A The contact area between the support and the ground is given; the vertical support reaction force is obtained by integrating over the entire contact area. ; 4-2 Repeat step 4-1 to obtain the tooling in sequence. n Vertical support reaction force at each support angle to The maximum vertical support reaction force occurs. The branch corner number is m ; 4-3 Repeat step 1-1, and in the simplified model, delete the item numbered in step 4-2. m The supporting angle; 4-4 Repeat steps 3-2 and 4-1 to obtain the maximum vertical displacement of the support angle under this unfavorable working condition. ; 4-5 Establish the basic evaluation criteria for tooling based on Formula 3: (3) in, This is the ratio of the vertical displacement caused by the removal of the support corner under this working condition to the design allowable value; The maximum allowable deformation value for the tooling base design; n For safety factor; when If the calculation result is less than or equal to 1, it indicates that the tooling foundation design value is sufficient; when If the calculated result is greater than 1, it indicates that the deformation of the aircraft tooling is out of tolerance. In this case, it is necessary to increase the thickness of the tooling base and repeat steps one through four until the calculated result is obtained. Until it is less than or equal to 1.

[0008] The beneficial effects of this invention are as follows: This invention establishes a method for evaluating the thickness of aircraft tooling foundations based on force feedback using the finite element method. Considering factors such as the thickness of the dedicated foundation, the geometry of the tooling, the type of tooling material, the support angles and ground friction, and force and moment balance, the method first calculates the magnitude of the reaction force and vertical displacement of each support angle under normal operating conditions. Then, the support angle with the maximum reaction force is removed from the calculation model, and the magnitude of the reaction force and vertical displacement of each support angle under unfavorable operating conditions are calculated. Finally, the ratio of the displacement difference between the two operating conditions to the design allowable value is used as the evaluation benchmark for the foundation design. The calculation results can be used to optimize the design of the tooling foundation thickness, further improving the stability of large aircraft tooling foundations and preventing the decrease in tooling accuracy caused by insufficient foundation thickness.

[0009] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0010] Figure 1 This is a finite element model of the aircraft tooling, support bracket, and ground in step one of this invention; Figure 2 The displacement result calculated by finite element method in step three of this invention; Figure 3 This refers to the stress component along the vertical direction of a support angle calculated in step four of this invention. Figure 4 This refers to the vertical support reaction force results of each support corner of the tooling under different working conditions calculated in step four of this invention.

[0011] The numbering in the diagram is explained as follows: 1. Upper beam; 2. Left column; 3. Right column; 4. Bottom beam; 5. Corner support; 6. Ground; 7. Grid unit. Detailed Implementation

[0012] like Figure 1-4 As shown, a method for evaluating the thickness of aircraft tooling foundations based on force feedback includes the following steps: Step 1: Establish a reasonably simplified finite element model of the tooling fixture. The specific process is as follows: 1-1 In this embodiment, a three-dimensional geometric model of a large aircraft assembly tooling is established using CAD software. All parts except the upper beam 1, the left column 2 and right column 3 of the frame column, the bottom beam 4, and the support corner 5 of the aircraft assembly tooling model are deleted to create a simplified model. The simplified model is guaranteed to have the same length, width, and height dimensions as the original aircraft tooling. The position and size of the support corner at the bottom of the tooling in the simplified model are consistent with the actual aircraft tooling. 1-2 A ground model 6 is created below the simplified model. The length and width of the ground model are no less than 1.2 times the length and width of the actual aircraft tooling, and the height is equal to the actual height of the factory ground 6. In this embodiment, the length, width, and height of the ground model 6 are 25000mm, 3000mm, and 100mm, respectively. The calculation model is as follows: Figure 1 As shown.

[0013] Step two involves establishing reasonably simplified mechanical boundary conditions, the specific process of which is as follows: 2-1 Adjust the material density of the tooling finite element model according to Formula 1 (1) in, The actual material density for aircraft tooling is taken as 7.8 × 10⁻⁶. -9 t / mm 3 ; The actual weight of the aircraft tooling is taken as 50t. Given a finite element model with a mass of 5.1t, the calculation yielded... The material density of the finite element model is 7.94 × 10⁻⁶. -10 t / mm 3 ; 2-2 Based on the material type of the aircraft tooling, the Young's modulus and Poisson's ratio of the upper beam 1, left column 2 and right column 3, bottom beam 4 and support 5 of the aircraft tooling are set to 210 GPa and 0.30, respectively; the Young's modulus of the ground 6 is 20 times that of the actual Young's modulus of the aircraft tooling (i.e. 4200 GPa), and the Poisson's ratio is 0.25 for concrete material; 2-3 Set constraints at the bottom of the ground model to limit 6 degrees of freedom; provide support force from the friction between the support corner and the ground in the simplified tooling model, and give the coefficient of friction for their contact. μ =0.2.

[0014] Step 3: Finite element simulation calculation. The specific process is as follows: 3-1 Mesh Generation: In the ground model and simplified model, the maximum dimensions of mesh cell 7 (length, width, and height) shall not exceed 1% of the length, width, and height of the aircraft tooling; 3-2 In the finite element software ABAQUS 6.14, a gravity load was applied and the statics module was used to calculate the displacement and stress fields of the aircraft tooling under its own weight, obtaining the maximum vertical displacement of the support angle under normal working conditions. =0.008mm, the displacement field results are as follows Figure 2 As shown.

[0015] Step four establishes a basic thickness evaluation method, the specific process of which is as follows: 4-1 Using Formula 2, the contact stress (i.e., CPRESS stress result, such as...) Figure 3 (As shown) Integrating the forces yields the vertical support reactions of ground 6 against any support corner in the simplified model.

[0016] (2) in, For a mesh element 7, the stress component along the vertical direction is represented by the first element in this embodiment. =8.418MPa A The contact area between the support corner and ground 6 is 100mm². 2 By summing up each element and integrating over the entire contact area, the vertical support reaction force of the ground where the wheel is located can be obtained. =55000N, such as Figure 4 As shown. 4-2 Repeat step 4-1 to calculate the vertical support reactions at each of the 24 support corners of the tooling. to The maximum vertical support reaction force occurs. The branch corner number is m= 13; 4-3 Repeat step 1-1, and in the simplified model, delete the item numbered in step 4-2. m= 13 supporting angles; 4-4 Repeat steps 3-2 and 4-1 to obtain the maximum vertical displacement of the support angle under this unfavorable working condition. =0.02mm; 4-5 Establish the basic evaluation criteria for tooling based on Formula 3: (3) in, n For safety reasons, this embodiment takes... n =1; The maximum allowable deformation for the tooling base design is 0.1 mm; This is the ratio of the vertical displacement caused by the removal of the support corner under this working condition to the design allowable value. =0.12, at this time The calculation result is less than or equal to 1, indicating that the tooling foundation design value is sufficient.

[0017] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for evaluating the thickness of aircraft tooling foundations based on force feedback, characterized in that, Includes the following steps: Step 1: Establish a reasonably simplified finite element model of the tooling fixture. The specific process is as follows: 1-1 A three-dimensional geometric model of the large aircraft assembly tooling was established using CAD software. All parts except the upper beam, frame column, bottom beam, and support corners were removed from the aircraft assembly tooling model to create a simplified model. The simplified model was made to ensure that the length, width, and height of the original aircraft tooling were the same as those of the original aircraft tooling. The position and size of the support corners at the bottom of the tooling in the simplified model were consistent with those of the original aircraft tooling. 1-2 Build a ground model below the simplified model. The length and width of the ground model shall not be less than 1.2 times the length and width of the actual aircraft tooling, and the height shall be equal to the actual height of the factory foundation. Step two involves establishing reasonable and simplified mechanical boundary conditions, including the following steps: 2-1 Adjust the material density of the tooling finite element model according to Formula 1 （1） in, The material density in the finite element model; The actual material density of the aircraft tooling; The actual quality of aircraft tooling; For the quality of the finite element model; 2-2 Based on the type of aircraft tooling material, set the Young's modulus and Poisson's ratio of the actual aircraft tooling; the Young's modulus of the ground material is 20 times that of the actual aircraft tooling, and the Poisson's ratio is the same as that of concrete material; 2-3 Set constraints at the bottom of the ground model to limit 6 degrees of freedom; provide support force from the friction between the support corner and the ground in the simplified tooling model, and give the friction coefficient between the two. Step 3, finite element simulation calculation, includes the following steps: 3-1 Mesh Generation: The maximum dimensions of the mesh cells in the ground model and simplified model shall not exceed 1% of the length, width, and height of the aircraft tooling; 3-2 In the finite element method software, a gravity load is applied and the statics module is used to calculate the displacement and stress fields of the aircraft tooling under its own weight, obtaining the maximum vertical displacement of the support angle under normal working conditions. ; Step four establishes a basic thickness evaluation method, including the following steps: 4-1 The vertical support reaction force of the ground in the ground model on any support corner in the simplified model is obtained by integrating the contact stress using Formula 2. （2） in, Let be the stress component along the vertical direction of a mesh element. A The contact area between the support and the ground is given; the vertical support reaction force is obtained by integrating over the entire contact area. ; 4-2 Repeat step 4-1 to obtain the tooling in sequence. n Vertical support reaction force at each support angle to The maximum vertical support reaction force occurs. The branch corner number is m ; 4-3 Repeat step 1-1, and in the simplified model, delete the item numbered in step 4-2. m The supporting angle; 4-4 Repeat steps 3-2 and 4-1 to obtain the maximum vertical displacement of the support angle under unfavorable working conditions. ; 4-5 Establish the basic evaluation criteria for tooling based on Formula 3: （3） in, This is the ratio of the vertical displacement caused by the removal of the support corner under unfavorable working conditions to the maximum allowable deformation value under design conditions. The maximum allowable deformation value for the tooling base design; n For safety factor; when If the calculation result is less than or equal to 1, it indicates that the tooling foundation design value is sufficient; when If the calculated result is greater than 1, it indicates that the deformation of the aircraft tooling is out of tolerance. In this case, it is necessary to increase the thickness of the tooling base and repeat steps one through four until the calculated result is obtained. Until it is less than or equal to 1.

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