Method for calculating thermal buckling critical value of composite metal connecting structure

Abstract

A method for calculating the critical value of thermal buckling of a composite metal connection structure includes: obtaining the deformation relationship of the composite metal connection structure based on the stiffness ratio of the connection parts; then correcting the thermal expansion coefficient of the metal in the composite metal connection structure to obtain the corrected thermal expansion coefficient α of the metal in the composite metal connection structure. ′ 2; Based on the critical theory of structural thermal buckling, the modified thermal expansion coefficient α of the metal in the composite metal connection structure is used. ′ 2. The critical temperature difference for buckling instability of the composite metal connection structure was calculated: where ΔT is the critical temperature difference for buckling instability of the composite metal connection structure; μ2 is the Poisson's ratio of the metal material in the composite metal connection structure; m and n are the buckling half-wave numbers of the composite metal connection structure in the length and width directions; and a and b are the length and width of the composite metal connection structure.

Description

Technical Field

[0001] This application belongs to the field of determining the critical value of thermal buckling of composite metal connection structures, and specifically relates to a method for calculating the critical value of thermal buckling of composite metal connection structures. Background Technology

[0002] The extensive use of composite materials in aircraft structures results in a large number of composite metal connection structures, such as wing ribs, wing-body separation surfaces, and tail separation surfaces.

[0003] Due to the significant difference in thermal expansion coefficients between composite materials and metals, thermal stress is generated within the connecting structure when temperature changes occur during aircraft service. When the thermal stress accumulates to a certain extent, the composite material-metal connecting structure will experience thermal buckling instability.

[0004] The current lack of a method to quickly and accurately determine the critical value of thermal buckling of composite metal connection structures restricts the design and application of composite metal connection structures. Therefore, this application is proposed.

[0005] It should be noted that the above background information is only used to assist in understanding the inventive concept and technical solution of this invention, and it does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above information was disclosed on the filing date of this application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0006] The purpose of this application is to provide a method for calculating the critical value of thermal buckling of composite metal connection structures, so as to overcome or mitigate at least one of the known technical defects.

[0007] The technical solution of this application is:

[0008] A method for calculating the critical value of thermal buckling in a composite metal connection structure includes:

[0009] Based on the stiffness ratio of the connection parts of the composite metal connection structure, the deformation relationship of the composite metal connection structure is obtained, and then the thermal expansion coefficient of the metal in the composite metal connection structure is corrected to obtain the corrected thermal expansion coefficient α′2 of the metal in the composite metal connection structure.

[0010] Based on the critical theory of structural thermal buckling, the critical temperature difference for buckling instability of composite metal-connected structures is calculated using the corrected thermal expansion coefficient α′2 of the metal in the composite metal-connected structure:

[0011]

[0012] in,

[0013] ΔT is the critical temperature difference for buckling instability of the composite metal connection structure;

[0014] μ2 is the Poisson's ratio of the metal material in the composite metal connection structure;

[0015] m is the buckling half-wave number of the composite metal connection structure in the length direction;

[0016] n is the buckling half-wave number of the composite metal connection structure in the width direction;

[0017] 'a' represents the length of the composite metal connection structure;

[0018] b represents the width of the composite metal connection structure.

[0019] According to at least one embodiment of this application, in the above-described method for calculating the critical value of thermal buckling of composite metal connection structures,

[0020]

[0021] in,

[0022] k is an intermediate variable;

[0023] α1 is the coefficient of thermal expansion of the composite material in the composite metal connection structure;

[0024] α2 is the coefficient of thermal expansion of the metal in the composite metal connection structure;

[0025] E1 is the elastic modulus of the composite material in the composite metal connection structure;

[0026] t1 represents the thickness of the composite material in the composite metal connection structure;

[0027] μ1 is the Poisson's ratio of the composite material in the composite metal connection structure;

[0028] E2 is the elastic modulus of the metal in the composite metal connection structure;

[0029] t2 represents the thickness of the metal in the composite metal connection structure.

[0030] This application has at least the following beneficial technical effects:

[0031] A method for calculating the critical value of thermal buckling of composite metal connection structures is provided. The method is designed based on the stiffness ratio of the connection parts of the composite metal connection structure to obtain the deformation relationship of the composite metal connection structure. Then, the thermal expansion coefficient of the metal in the composite metal connection structure is corrected to obtain the corrected thermal expansion coefficient α′2 of the metal in the composite metal connection structure. Based on the critical theory of structural thermal buckling, the critical temperature difference for buckling instability of the composite metal connection structure is calculated using the corrected thermal expansion coefficient α′2 of the metal in the composite metal connection structure. This method can quickly and accurately determine the critical value of thermal buckling of composite metal connection structures. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the method for calculating the critical value of thermal buckling of composite metal connection structure provided in the embodiments of this application;

[0033] Figure 2 This is a schematic diagram of a 7050-T7451 aluminum alloy flat plate, provided in an embodiment of this application, which uses a composite material with a coefficient of thermal expansion much lower than that of the plate for constraint support.

[0034] Figure 3 This is a schematic diagram of the measurement of the flat thermal strain curve of 7050-T7451 aluminum alloy provided in the embodiments of this application. Detailed Implementation

[0035] To make the technical solution and advantages of this application clearer, the technical solution of this application will be described in a clearer and more complete manner below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only some embodiments of this application, and are only used to explain this application, not to limit this application. It should be noted that, for ease of description, only the parts related to this application are shown in the accompanying drawings. Other related parts can be referred to the general design. In the absence of conflict, the embodiments and technical features in the embodiments of this application can be combined with each other to obtain new embodiments.

[0036] Furthermore, unless otherwise defined, the technical or scientific terms used in this application description shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "upper," "lower," "left," "right," "center," "vertical," "horizontal," "inner," and "outer," etc., used in this application description to indicate relative direction or positional relationship are used only to indicate relative orientation or positional relationship, and do not imply that the device or component must have a specific orientation, or be constructed and operated in a specific orientation. When the absolute position of the described object changes, its relative positional relationship may also change accordingly, and therefore should not be construed as a limitation on this application. The terms "first," "second," "third," and similar terms used in this application description are used only for descriptive purposes to distinguish different components, and should not be construed as indicating or implying relative importance. The terms "a," "one," or "the," etc., used in this application description should not be construed as an absolute limitation on quantity, but should be construed as indicating the existence of at least one. The terms "including," "comprising," etc., used in this application description mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, without excluding other elements or objects.

[0037] Furthermore, it should be noted that, unless otherwise explicitly specified and limited, terms such as “installation,” “connection,” and “linkage” used in the description of this application should be interpreted broadly. For example, a connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; or it can be a connection within two components. Those skilled in the art can understand its specific meaning in this application according to the specific circumstances.

[0038] Under the four-sided constraint of composite materials, the critical temperature difference for buckling instability can be obtained from the theoretical calculation formula of the structural thermal buckling critical temperature for metal sheets:

[0039]

[0040] in,

[0041] μ2 is the Poisson's ratio of the metal material in the composite metal connection structure;

[0042] α2 is the coefficient of thermal expansion of the metal in the composite metal connection structure;

[0043] m is the buckling half-wave number of the composite metal connection structure in the length direction;

[0044] n is the buckling half-wave number of the composite metal connection structure in the width direction;

[0045] 'a' represents the length of the composite metal connection structure;

[0046] b represents the width of the composite metal connection structure.

[0047] The method for calculating the critical value of thermal buckling of composite metal connection structures provided in this application corrects the thermal expansion coefficient α2 of the metal in the composite metal connection structure and calculates the critical temperature difference for buckling instability of the composite metal connection structure, as follows:

[0048] Step 1: Based on the stiffness ratio of the connection parts of the composite metal connection structure, obtain the deformation relationship of the composite metal connection structure:

[0049] Force balance equation: A x1 σ x1 =A x2 σ x2 A y1 σ y1 =A y2 σ y2 ;

[0050] in,

[0051] A x1 The area of ​​the composite material connection part in the x-direction in the composite metal connection structure is numerically equal to the length along the x-direction multiplied by its thickness.

[0052] σ x1 This represents the stress in the x-direction at the composite material connection point in a composite metal connection structure.

[0053] A x2 The area of ​​the metal connection part in the composite metal connection structure in the x direction is numerically equal to the length along the x direction multiplied by its thickness.

[0054] σ x2 This represents the stress in the x-direction at the metal connection portion of a composite metal connection structure.

[0055] A y1 The area of ​​the composite material connection part in the y direction in the composite metal connection structure is numerically equal to the length along the y direction multiplied by its thickness.

[0056] σ y1 This represents the stress in the y-direction at the composite material connection point in a composite metal connection structure.

[0057] A y2 The area of ​​the metal connection part in the composite metal connection structure in the y direction is numerically equal to the length along the y direction multiplied by its thickness.

[0058] σ y2This represents the stress in the y-direction at the metal connection portion of a composite metal connection structure.

[0059] Stress-strain constitutive equations:

[0060]

[0061]

[0062] in,

[0063] E1 is the elastic modulus of the composite material in the composite metal connection structure;

[0064] ε x1 The strain of the composite material in the x-direction in the composite metal connection structure;

[0065] ε y1 The strain of the composite material in the y-direction in the composite metal connection structure;

[0066] μ1 is the Poisson's ratio of the composite material in the composite metal connection structure;

[0067] α1 is the coefficient of thermal expansion of the composite material in the composite metal connection structure;

[0068] T represents temperature;

[0069] E2 is the elastic modulus of the metal in the composite metal connection structure;

[0070] ε x2 The strain of the metal in the x-direction in the composite metal connection structure;

[0071] ε y2 The strain of the metal in the y-direction in the composite metal connection structure;

[0072] Deformation compatibility equations:

[0073] Step 2: Obtain the corrected coefficient of thermal expansion of the metal in the composite metal connection structure:

[0074]

[0075]

[0076] in,

[0077] The modified coefficient of thermal expansion of the metal in the α′2 composite metal connection structure;

[0078] t1 represents the thickness of the composite material in the composite metal connection structure;

[0079] t2 represents the thickness of the metal in the composite metal connection structure.

[0080] Step 3: Substitute the corrected coefficient of thermal expansion of the metal in the composite metal connection structure into the calculation of the critical temperature difference for buckling instability of the composite metal connection structure:

[0081]

[0082] In one specific embodiment, the 7050-T7451 aluminum alloy flat plate is constrained and supported on all four sides using a composite material with a coefficient of thermal expansion much lower than its own. Figure 2 As shown, strain gauges A7 and B7, A8 and B8, and A9 and B9 are bonded to each other on both sides of an aluminum alloy plate. When the ambient temperature rises from 20℃ to 70℃, the thermal deformation of the aluminum alloy plate is constrained, and thermal stress is generated in the structure. The accumulation of thermal stress leads to thermal buckling. The thermal strain curves measured by strain gauges A7 and B7, A8 and B8, and A9 and B9 are shown in the figure. Figure 3 As shown.

[0083] since Figure 3 As can be seen, the critical temperature difference for thermal buckling is: ΔT = 66.1 - 20 = 46.1℃;

[0084] Using the original coefficient of thermal expansion of the aluminum alloy plate, the critical temperature difference for thermal buckling instability is calculated as follows:

[0085]

[0086] Correction for the coefficient of thermal expansion of aluminum alloy flat plates:

[0087] Using the corrected coefficient of thermal expansion of the aluminum alloy plate, the critical temperature difference for thermal buckling instability is calculated as follows:

[0088]

[0089] As can be seen from the above, the calculation of the critical temperature difference for thermal buckling instability using the original thermal expansion coefficient of the aluminum alloy plate deviates significantly from the actual value. However, the calculation of the critical temperature difference for thermal buckling instability using the corrected thermal expansion coefficient of the aluminum alloy plate is closer to the actual value and can meet the needs of engineering design.

[0090] The technical solution of this application has been described in conjunction with the preferred embodiments shown in the accompanying drawings. Those skilled in the art should understand that the scope of protection of this application is obviously not limited to these specific embodiments. Without departing from the principles of this application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of this application.

Claims

1. A method for calculating the critical value of thermal buckling in a composite metal connection structure, characterized in that, include: Based on the stiffness ratio of the joints in the composite metal connection structure, the deformation relationship of the composite metal connection structure is obtained. Then, the thermal expansion coefficient of the metal in the composite metal connection structure is corrected to obtain the corrected thermal expansion coefficient α of the metal in the composite metal connection structure. ′ 2; Based on the critical theory of structural thermal buckling, the modified thermal expansion coefficient α of the metal in the composite metal connection structure is used. ′ 2. The critical temperature difference for buckling instability of the composite metal connection structure was calculated: in, ΔT is the critical temperature difference for buckling instability of the composite metal connection structure; μ2 is the Poisson's ratio of the metal material in the composite metal connection structure; m is the buckling half-wave number of the composite metal connection structure in the length direction; n is the buckling half-wave number of the composite metal connection structure in the width direction; 'a' represents the length of the composite metal connection structure; b represents the width of the composite metal connection structure; in, k is an intermediate variable; α1 is the coefficient of thermal expansion of the composite material in the composite metal connection structure; α2 is the coefficient of thermal expansion of the metal in the composite metal connection structure; E1 is the elastic modulus of the composite material in the composite metal connection structure; t1 represents the thickness of the composite material in the composite metal connection structure; μ1 is the Poisson's ratio of the composite material in the composite metal connection structure; E2 is the elastic modulus of the metal in the composite metal connection structure; t2 represents the thickness of the metal in the composite metal connection structure.

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