Aircraft engine oil tank bracket and design method thereof

Abstract

The present invention provides an aircraft engine oil tank bracket and a design method thereof, belonging to the field of aerospace bracket structures. The aircraft engine oil tank bracket is an integral structure; the aircraft engine oil tank bracket includes a plurality of lugs and a connecting structure connecting adjacent lugs, the connecting structure being hollowed out; and each lug is provided with a through hole. Compared with traditional bracket structures, the overall stiffness of the bracket structure of the present invention and the local stiffness of the lug connections are significantly improved. Moreover, the improvement in the local stiffness of the lug connections can also improve the stress distribution of the hoop structure connected thereto, so that it no longer bears eccentric tension, thereby reducing the stress level of the hoop structure.

Description

Technical Field

[0001] The present invention belongs to the field of aerospace support structures, and in particular relates to an aerospace engine oil tank support and a design method thereof. Background Art

[0002] The oil tank system consists of the oil tank, oil tank housing, bracket, strap, and rubber. Applying bolt preload to the bolts on the bracket tightens the strap and secures the oil tank housing to the aircraft engine, as shown in Figures 1-1 and Figure 1-2 As shown, it includes a left bracket and a right bracket B, wherein the right bracket B includes three brackets, namely B1, B2 and B3, and 7 parallel ears are provided on the right bracket B. Specifically, a first ear piece 1, a second ear piece 2 and a fifth ear piece 5 are provided on the bracket B1, a third ear piece 3, a fourth ear piece 4 and a sixth ear piece 6 are provided on the bracket B2, and a seventh ear piece 7 is provided on the bracket B3. The bracket B is connected to a hoop through the first ear piece 1 and the second ear piece 2, is connected to another hoop through the third ear piece 3 and the fourth ear piece 4, is connected to other parts of the aircraft engine through the fifth ear piece, is connected to other parts of the aircraft engine through the sixth ear piece 6, and is connected to other parts of the aircraft engine through the seventh ear piece 7.

[0003] The hoop is subjected to tension due to the bolt preload and transmits this tension to the bracket structure. However, bracket B1 has mounting holes only on one side and is fixed. This structural form and service conditions result in a significant difference in stiffness between the left and right sides of bracket B1, causing the connected hoop to be eccentrically tensile, resulting in stress concentration and easily leading to fatigue failure during service. Therefore, it is necessary to optimize the bracket design to improve overall stiffness while also taking into account local stiffness, so as to achieve a more reasonable stiffness distribution and thus improve the stress distribution of the connected hoop structure.

[0004] In recent years, thanks to the development of advanced manufacturing technology, the production and manufacturing costs of complex structures have been reduced, and topology optimization methods have been widely used in the aerospace field. Compared with traditional size optimization and shape optimization, topology optimization does not rely on the initial configuration and has a larger design space, which can provide designers with a new conceptual design model. Many scholars at home and abroad have introduced topology optimization methods into the design of bracket structures. Most of these studies start from the mechanical problems of the bracket itself, with the improvement of the overall stiffness of the bracket structure as the design requirement, without considering the local stiffness of the bracket structure connection, which may cause the mechanical properties of the connection structure connected to the bracket to fail to meet the design requirements. Most of the existing bracket structure designs start from the mechanical problems of the bracket itself, with the improvement of the overall stiffness of the bracket structure as the design requirement, without considering the local stiffness of the bracket structure connection, which may cause the mechanical properties of the connection structure connected to the bracket to fail to meet the design requirements. Summary of the Invention

[0005] The purpose of the present invention is to solve the difficulties existing in the above-mentioned prior art and provide an aircraft engine oil tank bracket and a design method thereof, which fully solves the problem of eccentric force on the split bracket, effectively improves the overall stiffness of the bracket structure and the local stiffness of the bracket connection, improves the stress distribution state of the hoop structure connected thereto, and reduces the stress levels of the hoop structure and the bracket structure.

[0006] The present invention is achieved through the following technical solutions:

[0007] A first aspect of the present invention provides an aircraft engine oil tank bracket, wherein the aircraft engine oil tank bracket is an integral structure;

[0008] The aircraft engine oil tank bracket includes a plurality of lugs and a connecting structure connecting adjacent lugs, and the connecting structure is hollowed out;

[0009] Each ear piece is provided with a through hole.

[0010] A further improvement of the present invention is that the aircraft engine oil tank bracket includes seven parallel lugs, namely the first lug to the seventh lug;

[0011] The first lug is located at one end of the aircraft engine oil tank bracket, and the seventh lug is located at the other end of the aircraft engine oil tank bracket;

[0012] The first ear piece, the second ear piece, the third ear piece, the fourth ear piece and the seventh ear piece are each provided with a through hole, and the fifth ear piece and the sixth ear piece are each provided with two through holes.

[0013] A second aspect of the present invention provides a method for designing an aircraft engine oil tank bracket, the aircraft engine oil tank bracket comprising seven parallel lugs and a connecting structure connecting adjacent lugs, the seven lugs being respectively a first lug to a seventh lug;

[0014] The method designs the aircraft engine oil tank bracket as an integral structure;

[0015] The method adopts a topology optimization method to optimize the aircraft engine oil tank bracket to obtain an optimized aircraft engine oil tank bracket.

[0016] A further improvement of the present invention is that the method comprises:

[0017] Step 1: Determine the topology optimization design domain based on the assembly relationship between the aircraft engine oil tank system and other aircraft engine components;

[0018] Step 2: Establish a geometric model of the topology optimization design domain and perform finite element discretization on the geometric model to obtain a discretized network model;

[0019] Step 3: Perform topology optimization based on the discretized mesh model to obtain the optimized aircraft engine oil tank bracket.

[0020] A further improvement of the present invention is that the optimization formula used in the topology optimization in step 3 is as follows:

[0021]

[0022] Where K, U and F are the overall stiffness matrix, displacement vector and equivalent nodal load vector respectively;

[0023] is the node displacement vector of the ith element, is the element stiffness matrix of the i-th element, ρ i is the cell density of the i-th cell;

[0024] V i is the volume of the i-th unit, V * is the upper limit constraint of the material volume;

[0025] U 12 , U 22 , U 32 and U 42 are the displacements of the first, second, third and fourth lugs along the y direction respectively;

[0026] C is the overall strain energy of the structure, and N is the number of elements;

[0027] h(ρ) is a volume constraint function, g1(ρ) is a constraint function for controlling the relative displacement between the first ear and the second ear, and g2(ρ) is a constraint function for controlling the relative displacement between the third ear and the fourth ear.

[0028] A further improvement of the present invention is that the operation of step three includes:

[0029] (31), giving the topology optimization design domain a random initial structure density field ρ = ρ (0) , set the iteration step ite=1, set the maximum number of iterations ite max ;

[0030] (32), based on the current structural density field ρ, assemble the overall stiffness matrix K and solve the equilibrium equation KU = F to obtain the displacement vector U;

[0031] (33) According to U obtained in step (32) and the current structural density field ρ, the values ​​of the objective function C, constraint functions h(ρ), g1(ρ), and g2(ρ) in formula (1) are calculated, and the values ​​of the sensitivity of the constraint function and the objective function are calculated;

[0032] (34), submit the values ​​of objective function, constraint function, objective function sensitivity, and constraint function sensitivity to the optimization solver to obtain the updated structural density field ρ (ite) ;

[0033] (35), determine whether the convergence condition is met. If so, let the final structural density field be ρ (ite) , then go to step (36), if not, set ite=ite+1, then return to step (32);

[0034] (36) The optimization is completed and the optimized finite element model of the aircraft engine oil tank bracket is obtained;

[0035] (37) Feature extraction is performed on the finite element model of the optimized aircraft engine oil tank bracket to obtain the optimized aircraft engine oil tank bracket.

[0036] A further improvement of the present invention is that in step (33), the value of the constraint function sensitivity is calculated using the following formula:

[0037] The sensitivity calculation formula of g1(ρ) is as follows:

[0038]

[0039] The sensitivity calculation formula of g2(ρ) is as follows:

[0040]

[0041] The sensitivity calculation formula of h(ρ) is as follows:

[0042]

[0043] Among them, A 12 、A 22 They represent a vector in which only the p-th item is 1 and all other items are 0, and a vector in which only the q-th item is 1 and all other items are 0;

[0044] A 32 、A 42 They represent a vector in which only the rth item is 1 and all other items are 0, and a vector in which only the sth item is 1 and all other items are 0.

[0045] A further improvement of the present invention is that in step (33), the value of the sensitivity of the objective function is calculated using the following formula:

[0046]

[0047] A further improvement of the present invention is that the convergence condition in step (35) is:

[0048] max(ρ (ite) -ρ (0) )≤0.001 or ite≥ite max .

[0049] Compared with the prior art, the beneficial effects of the present invention are: compared with the traditional bracket structure, the overall stiffness of the bracket structure of the present invention and the local stiffness of the ear connection are significantly improved, and the improvement of the local stiffness of the ear connection can also improve the stress distribution of the hoop structure connected thereto, so that it no longer bears eccentric tension, thereby reducing the stress level of the hoop structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1-1 It is a schematic diagram of the working status of the existing bracket;

[0051] Figure 1-2 Schematic diagram of the structure of bracket B in the existing bracket;

[0052] Figure 2 This is a schematic diagram of the three-dimensional structure of the aircraft engine oil tank bracket of the present invention;

[0053] Figure 3 This is a schematic diagram of the main structure of the aircraft engine oil tank bracket of the present invention;

[0054] Figure 4 is the effect of the relative displacement constraint function;

[0055] Figure 5 The deformation cloud diagram of the stent of the present invention and the traditional stent (deformation coefficient: 100);

[0056] Figure 6 is a stress cloud diagram of a cuff connected to the stent of the present invention and a conventional stent;

[0057] Figure 7-1 This is a schematic diagram of the main structure of an aircraft engine oil tank bracket according to an embodiment of the present invention;

[0058] Figure 7-2 for Figure 7-1 Schematic diagram of the structure of the AA section;

[0059] Figure 7-3 for Figure 7-1 Schematic diagram of the structure of the BB section. DETAILED DESCRIPTION

[0060] The present invention is further described in detail below with reference to the accompanying drawings:

[0061] Figure 1-1 The structures of the left and right brackets are not exactly the same. The current split bracket design is mainly based on experience and considerations of lightweight design. Due to the assembly relationship between the bracket and other engine components, the bracket B1 has a mounting hole at only one end, i.e. Figure 1-2 The two holes on the fifth ear piece 5 in.

[0062] This structural form will cause the stiffness of the end with the mounting hole to be much greater than the end without the mounting hole, causing the hoop connected to it to bear eccentric tension. Because of this special structural form, simply optimizing the design of bracket B1 will obviously not be able to balance the stiffness of both ends of the bracket and improve the stress state of the hoop structure. Therefore, it is necessary to include three split brackets ( Figure 1-1 The bracket B of B1, B2 and B3 is considered as an integral bracket and optimized. The left bracket needs to be used to load the bolt preload, so its structure is not changed. The present invention only optimizes the design of the right bracket B.

[0063] like Figure 2 、 Figure 3 、 Figure 7-1 to Figure 7-3 As shown, the aircraft engine oil tank bracket of the present invention is an integral structure, including a plurality of lugs and a connecting structure connecting adjacent lugs. The connecting structure is hollowed out, and each lug is provided with a through hole.

[0064] Specifically, the aircraft engine oil tank bracket includes seven parallel lugs, namely a first lug 1 to a seventh lug 7. The first lug 1 is located at one end of the aircraft engine oil tank bracket, and the seventh lug 7 is located at the other end of the aircraft engine oil tank bracket.

[0065] like Figure 3 As shown, the total length L of the bracket in this embodiment is 332 mm, and there are 7 ears in total. Figure 7-1 arrive Figure 7-3 As shown, each of the first ear piece 1, the second ear piece 2, the third ear piece 3, the fourth ear piece 4, and the seventh ear piece 7 has a through hole with a diameter of 8.5 mm. Each of the fifth ear piece 5 and the sixth ear piece 6 has two through holes with a diameter of 5 mm. The present invention does not redesign the ear pieces or the through holes therein. The positions and numbers of all the ear pieces and through holes in the newly designed bracket of the present invention and the existing bracket are the same.

[0066] More specifically, the first and second tabs 1 and 2 are located at the same height, and the central axes of their through holes lie on the same straight line, referred to as the first straight line. The third and fourth tabs 4 and 4 are located at the same height, and the central axes of their through holes lie on the same straight line, referred to as the second straight line. The first straight line is parallel to the second straight line and vertically 17.75 mm higher than the second straight line. The fifth tab 5 is located below the first tab, and the central axes of the two through holes in the fifth tab 5 are symmetrically distributed on either side of the through hole in the first tab 1. Vertically, the central axes are 30.98 mm lower than the first straight line (i.e., the central axes of the two through holes in the fifth tab 5 are both 30.98 mm away from the first straight line). The sixth ear piece 6 is located between the second ear piece 2 and the third ear piece 3. In the vertical direction, the central axis of the two through holes on the sixth ear piece is 47.33 mm lower than the first straight line, and the central axis of the through hole of the seventh ear piece 7 is 40.86 mm lower than the first straight line in the vertical direction. These dimensions are exactly the same as those on the existing bracket.

[0067] Because the lugs are used to connect to other parts of the engine, the aircraft engine oil tank bracket of the present invention is the same as the existing bracket, also including 7 lugs. Moreover, the size, position, distance between adjacent lugs, height difference between adjacent lugs, and the size of the through holes opened on each lug are the same as those of the existing bracket. However, the connection structure between adjacent lugs is designed using a topology optimization method.

[0068] like Figure 3 As shown, the size and distribution relationship of each ear piece are as follows: d1 = d2 = d3 = d4 = 6.5 mm, d5 = d6 = 6 mm, d7 = 5 mm, l1 = 30 mm, l2 = 168 mm, l3 = 30 mm, l4 = 145 mm, l5 = 173 mm, which are exactly the same as those of the existing bracket.

[0069] The design method of the aircraft engine oil tank bracket of the present invention is as follows:

[0070] By using a topological optimization method that considers the local stiffness of the bracket connection, bracket B is designed as an integral bracket, so that the stiffness of the bracket structure is reasonably distributed, the relative displacement between the first ear piece 1 and the second ear piece 2, and the third ear piece 3 and the fourth ear piece 4 on bracket B is reduced, the stress distribution of the hoop structure connected thereto is improved, and the stress level of the hoop structure and bracket B is reduced.

[0071] The topology optimization design domain is determined based on the assembly relationship between the aircraft engine oil tank system and other aircraft engine components. The topology optimization design domain in this invention is determined based on two main criteria: 1. The area between the seven tabs of the bracket should be as large as possible to ensure sufficient design space. 2. Since the oil tank system is an assembly, the bracket's topology optimization design domain must be determined to ensure that the bracket does not interfere with other components in the oil tank system.

[0072] Based on the constructed design domain, the structure is optimized using the topology optimization method. The optimization formula of the design of the present invention is as follows:

[0073]

[0074] Formula (1) is a topology optimization formula, which includes objective function and constraint function.

[0075] Where K, U and F are the overall stiffness matrix, displacement vector and equivalent node load vector respectively. is the node displacement vector of the ith element, is the element stiffness matrix of the i-th element, ρ i is the cell density of the i-th cell, V i is the volume of the i-th unit, V * is the upper limit constraint of the material volume, U 12 , U 22 , U 32 and U 42 are the displacements of the first lug 1, the second lug 2, the third lug 3, and the fourth lug 4 along the y direction, respectively. C is the overall strain energy of the structure, i.e., the objective function. N is the number of units. h(ρ) is the volume constraint function. g1(ρ) is the constraint function controlling the relative displacement between the first lug 1 and the second lug 2. g2(ρ) is the constraint function controlling the relative displacement between the third lug 3 and the fourth lug 4. Figure 4 is the effect of the relative displacement constraint function, from Figure 4 It can be seen that when the relative displacement function is not considered, there is a relative displacement between the third ear piece 3 and the fourth ear piece 4. This relative displacement will cause the hoop connected thereto to bear eccentric tension. After considering the relative displacement function, the relative displacement between the third ear piece 3 and the fourth ear piece 4 is almost zero. Therefore, the method of the present invention effectively improves the stress state of the hoop.

[0076] Because the objective function C in formula (1) is to minimize the strain energy of the overall structure, that is, to maximize the overall stiffness of the structure, g1(ρ) is the constraint function that controls the relative displacement between the first lug 1 and the second lug 2, and g2(ρ) is the constraint function that controls the relative displacement between the third lug 3 and the fourth lug 4. Therefore, the topology optimization based on this optimization formula can maximize the stiffness of the bracket structure while controlling the local stiffness of the bracket structure connection through the constraint functions g1(ρ) and g2(ρ) and reducing the relative displacement between the first lug 1 and the second lug 2, and the third lug 3 and the fourth lug 4, making the stiffness distribution of the bracket structure more reasonable, thereby improving the stress distribution of the connected hoop structure and reducing the stress level of the hoop structure and the bracket.

[0077] Traditional topology optimization that considers structural stiffness issues minimizes the structural strain energy under a specified volume ratio. The method of the present invention adds a relative displacement constraint function to the optimization formula, which minimizes the structural strain energy and improves the overall stiffness of the structure while also taking into account the structural stiffness of the bracket structure ears.

[0078] Sensitivity analysis is a prerequisite for effectively solving topology optimization models based on gradient algorithms.

[0079] Next, we solve the sensitivity of the relative displacement constraint function g1(ρ) proposed by the method of the present invention to the unit design variable ρ (the pseudo density of the unit, used to distinguish whether the unit should be deleted). First, we directly derive g1(ρ) to obtain the following formula:

[0080]

[0081] Derivative KU=F with respect to the design variables yields:

[0082]

[0083]

[0084] make

[0085] U 12 =A 12 T U (5)

[0086] U 22 =A 22 T U (6)

[0087] Formula (5) and formula (6) are equivalent to screening out the required node displacement from the overall displacement U. In the above formula, A 12 and A 22They are vectors with only the pth and qth items being 1 and all other items being 0. p and q represent the position of the required node displacement in the overall displacement vector. For example, if a structure has 20 nodes, then vector U is a 60-row vector. If the displacement of node 10 along the y direction is required, then p is equal to 10*3+2=32, and A 12 It is a vector with only the 32nd row being 1 and the other rows being 0, representing the position of the displacement of node No. 10 along the y direction in the overall displacement vector U. The same is true for q, both of which represent the position of the displacement of the nodes they represent in the overall displacement vector.

[0088] By taking the derivative of formula (5) and combining it with formula (4), we can get the following formula:

[0089]

[0090] Similarly, we can get:

[0091]

[0092] Substituting equations (7) and (8) into equation (2), we can obtain the sensitivity formula of the relative displacement constraint function g1(ρ):

[0093]

[0094] In summary, directly deriving g1(ρ) yields formula (2), which is the intermediate form of the sensitivity expression of the relative displacement constraint function, because this expression contains and These two terms need to be expressed using existing variables (Formulas (7) and (8)). Substituting Formulas (7) and (8) back into Formula (2) yields Formula (9), the final form of the relative displacement constraint function sensitivity expression. When using the method of the present invention, Formula (9) can be used directly.

[0095] Similarly, the sensitivity formula of the constraint function g2(ρ) can be obtained as follows:

[0096]

[0097] Among them, A 32 and A 42 are vectors in which only the rth and sth items are 1 and all other items are 0. The definitions of r and s are the same as p and q, and they also represent the position of the required nodal displacement in the overall displacement vector.

[0098] Next, we solve the sensitivity of the objective function and constraint function h(ρ) in equation (1) to the unit design variable ρ.

[0099] First, directly derive C to obtain the following formula:

[0100]

[0101] Substituting formula (4) into formula (10), the sensitivity formula of the objective function can be obtained as follows:

[0102]

[0103] Directly deriving h(ρ) to obtain the sensitivity formula of the constraint function h(ρ) is as follows:

[0104]

[0105] Formula (1) is an optimization formula, which is equivalent to describing all the requirements for the optimal design of the bracket. The objective function of the optimization formula in the present invention is the overall strain energy of the bracket structure, and the constraint function is the volume of the bracket structure, the relative displacement between the first ear piece 1 and the second ear piece 2, and the relative displacement between the third ear piece 3 and the fourth ear piece 4. According to these requirements, a self-written program is used in combination with an optimization solver to design Figure 3 Bracket shown.

[0106] The specific steps are as follows:

[0107] Before the topology optimization process is carried out, it is necessary to establish a geometric model of the topology optimization design domain (the geometric model can be a CAD model, which is obtained by modeling with CAD software. As long as the size and assembly relationship of the bracket structure are input, the geometric model can be obtained through CAD software. I will not go into details here.), and use ABAQUS software for finite element discretization to obtain a discretized mesh model. Then, based on the discretized mesh model, the following topology optimization process is carried out:

[0108] The first step is to give the topology optimization design domain a random initial structure density field ρ = ρ (0) , iterative step ite=1. Assume the maximum number of iterations ite max =150;

[0109] The second step is to assemble the overall stiffness matrix K of the structure based on the current structural density field ρ (first form the unit stiffness matrix, then put the unit stiffness matrix of each unit into the corresponding position of the overall stiffness matrix to form the overall stiffness matrix), and solve the equilibrium equation KU=F to obtain the displacement vector U of the structure: U=K -1 F;

[0110] The third step is to calculate the objective function C, the constraint functions h(ρ), g1(ρ), and g2(ρ) in formula (1) based on U obtained in the second step and the current structural density field ρ. iis the cell density of the i-th cell. After obtaining ρ, a row vector A is given in which only the i-th column is 1 and the rest of the columns are 0. By the formula ρ i =Aρ to obtain the cell density of the i-th cell. Similarly, is the node displacement vector of the i-th unit. After obtaining U, the node displacement vector of the i-th unit can be obtained; U 12 , U 22 , U 32 and U 42 are the displacements of the first ear piece 1, the second ear piece 2, the third ear piece 3, and the fourth ear piece 4 along the y direction, and after obtaining U, the values ​​of these parameters can be obtained; is the unit stiffness matrix of the i-th unit. After obtaining K, the unit stiffness matrix of the i-th unit can be obtained; V i is the volume of the ith unit. After obtaining V, the volume of the ith unit can be obtained; V * is the upper limit constraint of the material volume, which is a known quantity and is an input condition determined before optimization. ), and the values ​​of the constraint function and the sensitivity of the objective function calculated according to equations (9), (11), and (12).

[0111] The values ​​of h(ρ), g1(ρ), and g2(ρ) are the values ​​of the constraint functions. The values ​​of the sensitivity of the constraint functions and the objective function need to be obtained through equations (9), (11), and (12). After the previous calculations, the parameter values ​​in equations (9), (11), and (12) have been obtained. By directly substituting these parameter values ​​into equations (9), (11), and (12), the values ​​of the sensitivity of the constraint functions and the objective function can be obtained.

[0112] The fourth step is to submit the values ​​of objective function, constraint function, objective function sensitivity and constraint function sensitivity to the optimization solver to obtain the updated structural density field ρ (ite) .

[0113] Specifically, the optimization solver is a function called MMA, which is included in the existing MATLAB software. It is briefly introduced as follows: Using this optimization solver requires some input parameters, which mainly include the number of constraints m, the number of design variables n, the number of loops loop, the current structure density field x, the lower limit of the design variable xmin, the upper limit of the design variable xmax, the design variable value xold1 of the previous iteration, the design variable value xold2 of the previous two iterations, the objective function value objlist(loop) of the current structure, the sensitivity of the objective function dc, the constraint function value v, the constraint Function sensitivity dv, lower asymptote low, upper asymptote upp, and scaling coefficients a0, a, ccc, d, where the number of constraints m, the number of design variables n, and the number of loops loop are given according to the optimization problem and do not need to be calculated; the objective function value objlist(loop), objective function sensitivity dc, constraint function value v, and constraint function sensitivity dv of the current structure are calculated according to the above formula and using the finite element analysis program; the lower asymptote low, upper asymptote upp, and scaling coefficients a0, a, ccc, d are given according to experience and do not need to be calculated.

[0114] The fifth step is to determine whether the convergence condition max(ρ (ite) -ρ (0) )≤0.001 or ite≥ite max , if the convergence condition is met, then the final structural density field is ρ (ite) , go to step 6. If the convergence condition is not met, set ite = ite + 1 and return to step 2.

[0115] Step 6: End optimization.

[0116] The seventh step is to obtain the final structural density field ρ after the optimization is completed. (ite) , after obtaining the structural density field, we can get Figure 3 The finite element model of the optimal bracket is shown, and then feature extraction is performed with the help of existing software to obtain Figure 3 The geometric model of the bracket is shown in FIG. These can be realized by using existing mature technologies and will not be described in detail here.

[0117] Figure 5 The deformation cloud diagram of the present invention stent and the traditional stent (deformation coefficient: 100) is shown in FIG. Figure 5 It can be seen that there is a large relative displacement between adjacent ears in the traditional bracket structure, and the bracket deformation amplitude is large. The relative displacement between adjacent ears in the bracket designed by the present invention is reduced compared with the traditional bracket. The relative displacement between the first ear piece 1 and the second ear piece 2, and the relative displacement between the third ear piece 3 and the fourth ear piece 4 are reduced by 96.56% and 71.25% respectively. The maximum deformation of the bracket designed by the present invention is reduced by 17.7%.

[0118] Figure 6 The stress cloud diagram of the cuff connected with the stent of the present invention and the traditional stent is shown in FIG. Figure 6 It can be seen that the bracket designed by the present invention ( Figure 6 The stiffness distribution of the new bracket (marked in the middle) is more reasonable, the hoop structure connected to it no longer bears eccentric tension, the stress distribution is more uniform, and the stress level is reduced by 30.84% ​​compared with before optimization.

[0119] Figure 7-2 and Figure 7-3 For example, the bracket of the present invention (such as Figure 7-1 The structural diagram of the two longitudinal sections is shown in FIG. Figure 7-2 and Figure 7-3 It can be seen that the fifth ear piece 5 and the sixth ear piece 6 each have two through holes, which are distributed on both sides of the ear piece and have a diameter of 5 mm.

[0120] Finally, it should be noted that the above technical solution is only one embodiment of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the application methods and principles disclosed in the present invention, and it is not limited to the method described in the above specific embodiment of the present invention. Therefore, the method described above is only preferred and does not have a restrictive meaning.

Claims

1. A design method for an aircraft engine oil tank bracket, the aircraft engine oil tank bracket comprising seven parallel lugs and a connecting structure connecting adjacent lugs, the seven lugs being respectively a first lug to a seventh lug, characterized in that: The method designs the aircraft engine oil tank bracket as an integral structure; The method uses a topology optimization method to optimize the aircraft engine oil tank bracket to obtain an optimized aircraft engine oil tank bracket; The method comprises: Step 1: Determine the topology optimization design domain based on the assembly relationship between the aircraft engine oil tank system and other aircraft engine components; Step 2: Establish a geometric model of the topology optimization design domain and perform finite element discretization on the geometric model to obtain a discretized network model; Step 3: Perform topology optimization based on the discretized mesh model to obtain the optimized aircraft engine oil tank bracket; The optimization formula used in the topology optimization in step 3 is as follows: Where K, U and F are the overall stiffness matrix, displacement vector and equivalent nodal load vector respectively; is the nodal displacement vector of the ith element, is the element stiffness matrix of the i-th element, ρ i is the cell density of the i-th cell; V i is the volume of the i-th unit, V * is the upper limit constraint of the material volume; U 12 , U 22 , U 32 and U 42 are the displacements of the first ear piece, the second ear piece, the third ear piece, and the fourth ear piece along the y direction respectively; C is the overall strain energy of the structure, and N is the number of elements; h(ρ) is a volume constraint function, g1(ρ) is a constraint function for controlling the relative displacement between the first ear and the second ear, and g2(ρ) is a constraint function for controlling the relative displacement between the third ear and the fourth ear.

2. The design method of an aircraft engine oil tank bracket according to claim 1, characterized in that: The operation of step three includes: (31), giving the topology optimization design domain a random initial structure density field ρ = ρ (0) , set the iteration step ite=1, set the maximum number of iterations ite max ; (32), based on the current structural density field ρ, assemble the overall stiffness matrix K and solve the equilibrium equation KU = F to obtain the displacement vector U; (33) According to U obtained in step (32) and the current structural density field ρ, the values ​​of the objective function C, constraint functions h(ρ), g1(ρ), and g2(ρ) in formula (1) are calculated, and the values ​​of the sensitivity of the constraint function and the objective function are calculated; (34), submit the values ​​of objective function, constraint function, objective function sensitivity, and constraint function sensitivity to the optimization solver to obtain the updated structural density field ρ (ite) ; (35), determine whether the convergence condition is met. If so, let the final structural density field be ρ (ite) , then go to step (36), if not, set ite=ite+1, then return to step (32); (36) The optimization is completed and the optimized finite element model of the aircraft engine oil tank bracket is obtained; (37) Feature extraction is performed on the finite element model of the optimized aircraft engine oil tank bracket to obtain the optimized aircraft engine oil tank bracket.

3. The design method of an aircraft engine oil tank bracket according to claim 2, characterized in that: In step (33), the value of the constraint function sensitivity is calculated using the following formula: The sensitivity calculation formula of g1(ρ) is as follows: The sensitivity calculation formula of g2(ρ) is as follows: The sensitivity calculation formula of h(ρ) is as follows: Among them, A 12 、A 22 They represent a vector in which only the p-th item is 1 and all other items are 0, and a vector in which only the q-th item is 1 and all other items are 0; A 32 、A 42 They represent a vector in which only the rth item is 1 and all other items are 0, and a vector in which only the sth item is 1 and all other items are 0.

4. The design method of an aircraft engine oil tank bracket according to claim 3, characterized in that: In step (33), the value of the objective function sensitivity is calculated using the following formula:

5. The design method of an aircraft engine oil tank bracket according to claim 4, characterized in that: The convergence condition in step (35) is: max(r (ite) -r (0) )≤0.001 orite≥ite max 。 6. An aircraft engine oil tank bracket, designed using the method according to any one of claims 1 to 5, characterized in that: The aircraft engine oil tank bracket is an integral structure; The aircraft engine oil tank bracket includes a plurality of lugs and a connecting structure connecting adjacent lugs, and the connecting structure is hollowed out; Each ear piece is provided with a through hole.

7. The aircraft engine oil tank bracket according to claim 6, characterized in that: The aircraft engine oil tank bracket includes seven parallel lugs, namely the first lug to the seventh lug; The first lug is located at one end of the aircraft engine oil tank bracket, and the seventh lug is located at the other end of the aircraft engine oil tank bracket; The first ear piece, the second ear piece, the third ear piece, the fourth ear piece and the seventh ear piece are each provided with a through hole, and the fifth ear piece and the sixth ear piece are each provided with two through holes.

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