A fast optimization method for buckling constraints of laminated plates based on criterion method

Abstract

The present application belongs to the field of computer-aided design, and particularly relates to a method for rapid optimization of laminate buckling constraints based on a criterion method, comprising: drawing a plurality of first relationship curves between critical buckling stress and ply thickness under different ply sequences and different ply ratios for all sample points; the first relationship curve also includes information labels of ply ratio, ply sequence and critical stress ratio in three directions; selecting a relationship curve that matches the stress level ratio information in three directions of the model to be optimized from the plurality of first relationship curves as a third relationship curve; fitting a fourth relationship curve between ply thickness and critical buckling strain under the ply sequence and ply ratio based on the third relationship curve and a stiffness solution function of a target laminate; based on the fourth relationship curve, combined with the law of initial stress level distribution, optimizing the target laminate by taking minimum ply thickness as the optimization target and taking critical buckling strain as the constraint.

Description

Technical Field

[0001] The present application relates to electrical digital data processing, and in particular to a fast optimization method for buckling constraints of laminated plates based on a criterion method. Background Art

[0002] With the growing demand for lightweight and high-strength aircraft structures in new aircraft, the proportion of composite materials used in aircraft has increased, and the load-bearing requirements for composite materials structures have become more stringent. Since the strength and stiffness of composite materials can be tailored, in order to give full play to the advantages of composite stiffened panels, their structures must be optimized. Due to the complexity of the analysis method of the buckling stability of composite structures, it is difficult to directly consider it in the multivariate optimization analysis of large-scale structural finite element models. It is mainly based on manual verification and adjustment, which results in the inability to consider the buckling design of composite structures in parallel with the strength design, and the best optimization results cannot be achieved. Summary of the invention

[0003] In order to solve the above problems, the present application provides a method for fast optimization of laminate buckling constraints based on a criterion method, comprising: step S1: drawing multiple first relationship curves between critical buckling stress and ply thickness under different ply orders and different ply ratios for all sample points; the first relationship curves also include information labels of ply ratio, ply order and critical stress ratio in three directions;

[0004] Step S2: selecting a relationship curve that matches the stress level ratio information in three directions of the model to be optimized from the multiple first relationship curves as the third relationship curve;

[0005] Step S3: Based on the third relationship curve and the stiffness solution function of the target laminate, a fourth relationship curve between the ply thickness and the critical buckling strain under the ply sequence and ply ratio is fitted;

[0006] Step S4: Based on the fourth relationship curve and in combination with the distribution law of the initial stress level, the target laminate is obtained by optimizing with the minimum ply thickness as the optimization target and the critical buckling strain as the constraint.

[0007] Preferably, before the optimization in step S4, the boundary line enveloping all the first relationship curves is used as the second relationship curve, and the point in the second relationship curve corresponding to the critical buckling stress being equal to the critical stress of the composite material's failure strength is used as the reference point, and the optimization elements in the optimization model that do not require buckling constraints are eliminated.

[0008] Preferably, the critical buckling stress includes a critical compressive buckling stress and a critical shear buckling stress.

[0009] Preferably, the sample points are generated by permutations and combinations of ply ratios, ply sequences, and ply thicknesses of the composite material.

[0010] Preferably, the method for calculating the critical buckling stress of a sample point includes:

[0011] Step S11: solving the bending stiffness matrix parameters of all sample points respectively according to the classical laminate theory, and solving the buckling coefficients of all sample points;

[0012] Step S12: Calculate the critical buckling stress of all sample points according to the bending stiffness matrix parameters and buckling coefficient.

[0013] Preferably, the specific steps of eliminating the optimization elements of the model to be optimized in the model to be optimized include:

[0014] Step S31: Obtain the critical buckling stress in the second relationship curve equal to the critical buckling stress of the composite material corresponding to the thickness T0 and the critical buckling stress corresponding to the minimum ply thickness ;

[0015] Step S32: Remove the thickness greater than T0 and the average stress less than The regional stability constraints.

[0016] Preferably, the total comprises N Different ply thicknesses, where:

[0017] ;

[0018] is the maximum ply thickness of the laminate, is the minimum ply thickness of the laminate, For equal thickness difference.

[0019] Preferably, the paving angles include four, and the total number of ply ratio combinations of the four angles is M , M =4×((1-4×u min ) / △u),u min It is the lower limit of the single angle ply ratio; △u is the proportional difference.

[0020] Preferably, the total number of sample points is Z, where Z = N × M × K; K is the number of ply sequences.

[0021] Preferably, the method for calculating the critical buckling stress of the sample points also includes: establishing a buckling coefficient input-output fast matching model according to the sample point boundary length, different boundary constraints and the bending stiffness matrix coefficient of the sample point, and calculating the critical buckling stress of all sample points according to the buckling coefficient input-output fast matching model.

[0022] The advantages of this application include: the present invention adopts the criterion method to optimize the design concept, evaluates the buckling stress law of laminates with different design parameters through theoretical analysis methods combined with structural finite element model analysis, and realizes composite material parameter optimization in combination with strength constraint optimization process. This method takes into account the buckling stability of composite laminates, and uses the criterion method optimization method to achieve rapid structural design, avoiding repeated iterations of strength and stability separation design, and provides a more effective means for composite material ply ratio and overall thickness design. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Flowchart of the fast optimization method for buckling constraints of laminates based on the criterion method. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the implementation of this application clearer, the technical scheme in the implementation of this application will be described in more detail in combination with the drawings in the implementation of this application. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described implementation is a part of the implementation of this application, not all of the implementations. The implementation described below with reference to the drawings is exemplary and is intended to be used to explain this application, and cannot be understood as a limitation on this application. Based on the implementation in this application, all other implementations obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The implementation of this application is described in detail below in combination with the drawings.

[0025] This application provides a fast optimization method for laminate buckling constraints based on the criterion method:

[0026] Step S1: Draw a plurality of first relationship curves between critical buckling stress and ply thickness at different ply sequences and different ply ratios for all sample points; the first relationship curves also include information labels of ply ratio, ply sequence and critical stress ratio in three directions.

[0027] Among them, the calculation method of critical buckling stress of sample points includes:

[0028] Step S11: solving the bending stiffness matrix parameters of all sample points respectively according to the classical laminate theory, and solving the buckling coefficients of all sample points;

[0029] Step S12: Calculate the critical buckling stress of all sample points according to the bending stiffness matrix parameters and buckling coefficient.

[0030] The critical buckling stress calculation method of the sample point also includes: establishing a buckling coefficient input-output fast matching model according to the sample point boundary length, different boundary constraints and the bending stiffness matrix coefficient of the sample point, and calculating the critical buckling stress of all sample points according to the buckling coefficient input-output fast matching model.

[0031] Step S2: selecting a relationship curve that matches the stress level ratio information in three directions of the model to be optimized from the multiple first relationship curves as the third relationship curve.

[0032] This step first gives the stress level ratio information in the three directions of the model to be optimized, and then for each first relationship curve, compares the given stress level ratio information in the three directions of the model to be optimized with the critical stress in the three directions of the ratio information label of the first relationship curve, finds the closest group, and obtains the corresponding ply ratio / ply sequence. The first relationship curve corresponding to this group can be used as the third relationship curve.

[0033] Based on the above technical features, in some optional implementations:

[0034] Through the stress level ratio information in three directions of the model to be optimized, for example, the stress level ratio information in the x direction, y direction, and shear direction of a certain area of ​​the model to be optimized is 6:3:1, and the closest critical stress ratio in the three directions is matched to 6.1:2.8:1.1 among the ratio information labels of all the first relationship curves, and the maximum proportion is taken as the main matching object. The ply ratio corresponding to the ratio information label is [2:2:5:1]s, and the ply sequence is [45, -45, 0, 90]s. The first relationship curve corresponding to the ratio information label can be used as the third relationship curve.

[0035] Step S3: Based on the third relationship curve and the stiffness solution function of the target laminate, a fourth relationship curve between the ply thickness and the critical buckling strain under the ply sequence and ply ratio is fitted;

[0036] Step S4: Based on the fourth relationship curve and in combination with the distribution law of the initial stress level, the target laminate is obtained by optimizing with the minimum ply thickness as the optimization target and the critical buckling strain as the constraint.

[0037] Based on the above technical features, for example, the critical buckling stress in the x-direction of a region of the model to be optimized is K nx ×t 2 , K nxis the fitting coefficient, t is the ply thickness, and the ply thickness of each region is optimized and analyzed in combination with the strength constraint. The goal is to minimize the structural weight, that is, the ply thickness of the optimized model is the smallest, that is, the thickness of the laminate is the smallest, and the stress of each region is closest to the critical stress as the constraint for optimization. The critical stress includes the critical buckling stress or the critical strength stress. For example, when the critical buckling stress in the x-direction of a certain region is 200, and the x-direction stress of the static analysis of the region is 250, the ply thickness needs to be adjusted. The adjustment formula is: t1=t0×(200 / 250)^0.5. t0 is the ply thickness before adjustment, and t1 is the ply thickness after adjustment.

[0038] Preferably, before the optimization in step S4, the boundary line enveloping all the first relationship curves is used as the second relationship curve, and the point in the second relationship curve corresponding to the critical buckling stress being equal to the critical stress of the composite material's failure strength is used as the reference point, and the optimization elements in the optimization model that do not require buckling constraints are eliminated.

[0039] Based on the above technical features, in some optional implementations:

[0040] Obtain the critical buckling stress in the second relationship curve equal to the critical stress of the composite material's failure strength corresponding to the thickness T0 and the critical buckling stress corresponding to the minimum ply thickness ; Eliminate the problem that the thickness of the model to be optimized is greater than T0 and the average stress is less than The regional stability constraints.

[0041] In some optional embodiments, the buckling stress includes compressive buckling stress and shear buckling stress.

[0042] In some optional embodiments, the N Different ply thicknesses, where:

[0043] ;

[0044] is the maximum ply thickness of the laminate, is the minimum ply thickness of the laminate, The thickness difference is equal.

[0045] In some optional embodiments, the paving angles include four, and the total number of ply ratio combinations of the four angles is M , M =4×((1-4×u min ) / △u),u min It is the lower limit of the single angle ply ratio; △u is the proportional difference.

[0046] In some optional implementations, the total number of sample points is Z, where Z = N × M × K ;K is the number of ply sequences.

[0047] In some optional embodiments, the method for calculating the critical buckling stress of the sample points also includes: establishing a buckling coefficient input-output fast matching model based on the sample point boundary length, different boundary constraints and the bending stiffness matrix coefficient of the sample point, and calculating the critical buckling stress of all sample points based on the buckling coefficient input-output fast matching model.

[0048] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A fast optimization method for buckling constraints of laminated plates based on a criterion method, characterized in that: include: Step S1: drawing a plurality of first relationship curves between critical buckling stress and ply thickness at different ply sequences and different ply ratios for all sample points; The first relationship curve also includes information labels of ply ratio, ply sequence and critical stress ratio in three directions; Step S2: selecting a relationship curve that matches the stress level ratio information in three directions of the model to be optimized from the multiple first relationship curves as the third relationship curve; Step S3: Based on the third relationship curve and the stiffness solution function of the target laminate, a fourth relationship curve between the ply thickness and the critical buckling stress under the ply sequence and ply ratio is fitted; Step S4: Based on the fourth relationship curve and in combination with the distribution law of the initial stress level, the target laminate is obtained by optimizing with the minimum ply thickness as the optimization target and the critical buckling stress as the constraint.

2. The fast optimization method for buckling constraints of laminated plates based on the criterion method according to claim 1, characterized in that: Before the optimization in step S4, the boundary line enveloping all the first relationship curves is taken as the second relationship curve, and the point in the second relationship curve corresponding to the critical buckling stress being equal to the critical stress of the composite material's failure strength is taken as the reference point, and the optimization elements in the optimization model that do not need to be subjected to buckling constraints are eliminated.

3. The fast optimization method for buckling constraints of laminated plates based on the criterion method according to claim 1, characterized in that: The critical buckling stress includes the critical compressive buckling stress and the critical shear buckling stress.

4. The fast optimization method for buckling constraints of laminated plates based on the criterion method according to claim 1, characterized in that: The sample points are generated by the arrangement and combination of the ply ratio, ply sequence and ply thickness of the composite material.

5. The fast optimization method for buckling constraints of laminated plates based on the criterion method according to claim 1, characterized in that: The critical buckling stress calculation method of the sample point includes: Step S11: solving the bending stiffness matrix parameters of all sample points respectively according to the classical laminate theory, and solving the buckling coefficients of all sample points; Step S12: Calculate the critical buckling stress of all sample points according to the bending stiffness matrix parameters and buckling coefficient.

6. The fast optimization method for buckling constraints of laminated plates based on the criterion method as claimed in claim 2, characterized in that: The specific steps to eliminate the optimization elements that do not need to be subjected to buckling constraints in the optimization model include: Step S31: Obtain the critical buckling stress in the second relationship curve equal to the critical buckling stress of the composite material corresponding to the thickness T0 and the critical buckling stress corresponding to the minimum ply thickness ; Step S32: Remove the thickness greater than T0 and the average stress less than The regional stability constraints.

7. The fast optimization method for buckling constraints of laminated plates based on the criterion method according to claim 4, characterized in that: Total includes N Different ply thicknesses, where: ； is the maximum ply thickness of the laminate, is the minimum ply thickness of the laminate, The thickness difference is equal.

8. The fast optimization method for buckling constraints of laminated plates based on the criterion method according to claim 7, characterized in that: There are four paving angles, and the total number of ply ratio combinations at the four angles is M , M =4×((1-4×u min ) / △u),u min It is the lower limit of the single angle ply ratio; △u is the proportional difference.

9. The fast optimization method for buckling constraints of laminated plates based on the criterion method according to claim 7, characterized in that: The total number of sample points is Z, Z = N × M × K; K is the number of ply sequences.

10. The fast optimization method for buckling constraints of laminated plates based on the criterion method according to claim 5, characterized in that: The critical buckling stress calculation method of the sample point also includes: establishing a buckling coefficient input-output fast matching model according to the sample point boundary length, different boundary constraints and the bending stiffness matrix coefficient of the sample point, and calculating the critical buckling stress of all sample points according to the buckling coefficient input-output fast matching model.

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