Method for evaluating thermal strength of c / sic skin skeleton structure based on cvi process forming

Abstract

The application provides a C / SiC skin framework structure thermal strength evaluation method based on a CVI process forming, and the method comprises the following steps: step one, modeling the C / SiC skin framework structure based on the CVI process forming, wherein rivets used for connecting the skin framework are realized by establishing equivalent connecting units; step two, calculating the thermal strength of the established C / SiC skin framework structure model, and applying thermal expansion deformation to the connecting units in the thermal strength calculation process to obtain a C / SiC stress field and three-direction internal force loads of the connecting units; and step three, processing the obtained C / SiC stress field and three-direction internal force loads of the connecting units to obtain the main strength of the C / SiC skin framework structure based on the CVI process forming and the rivet strength for connection. The technical scheme of the application can solve the technical problem of insufficient accuracy of the thermal strength data of the C / SiC skin framework structure based on the CVI process forming caused by not considering the connecting rivets in the prior art.

Description

Technical Field

[0001] This invention relates to the field of aircraft thermal strength calculation technology, and in particular to a method for evaluating the thermal strength of C / SiC skin skeleton structures formed by CVI process. Background Technology

[0002] High-speed aircraft operate at high Mach numbers and face severe aerodynamic heating under service conditions. As key lift and control components, the skin and frame structures such as wings and control surfaces generally require integrated thermal insulation and load-bearing designs to meet operational requirements under strong aerodynamic constraints. C / SiC material, a novel ceramic-based thermal structural material that has seen rapid development in the last decade following C / C materials, offers a series of significant advantages over homogeneous ceramics, including high temperature resistance, low density, high strength, high toughness, and the ability to avoid catastrophic damage. The excellent temperature resistance and load-bearing capacity of C / SiC materials have led to their widespread application in the skin and frame structures of high-speed aircraft, including wings and control surfaces.

[0003] The fabrication processes for C / SiC skin skeleton structures are mainly divided into CVI (Chemical Vapor Infiltration) and PIP (Precursor Infiltration Pyrolysis). Due to its sheet metal connection characteristics, the CVI process is highly suitable for fabricating large-size, complex, and lightweight skin skeleton structures, offering significant cost advantages. It is currently widely used in the fabrication of C / SiC skin skeleton structures for high-speed aircraft. A significant characteristic of the CVI process is that all components are connected online using numerous rivets, and the interfacial bonding force at the component joints is formed through vapor deposition. However, current techniques for analyzing the thermal strength of C / SiC skin skeleton structures formed using the CVI process do not consider the online connection effect of the large number of rivets during the CVI fabrication process, assuming that all skin skeleton parts constituting a certain C / SiC component have been formed as a whole through rivets and interfacial deposition. This method has a short modeling cycle and can simulate the overall stiffness characteristics of components well. However, it has problems such as the force transmission path in the calculation model may deviate significantly from the actual state, ignore the fact that rivets are the main load-bearing structures, overestimate the interface bonding strength between different components, overestimate the static and thermal strength performance of the skin frame structure as a whole, make it difficult to find the weak points in the structure, and cannot obtain the strength data of rivets. In particular, it will produce extremely high false thermal stress in the thermal stress calculation. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0005] This invention provides a method for evaluating the thermal strength of a C / SiC skin skeleton structure formed using the CVI process. The method includes: Step 1: Modeling the C / SiC skin skeleton structure formed using the CVI process, wherein the rivets used for connecting the skin skeleton are implemented by establishing equivalent connection units; Step 2: Performing thermal strength calculations on the established C / SiC skin skeleton structure model, applying thermal expansion deformation to the connection units during the calculation process to obtain the C / SiC stress field and the three-directional internal force loads of the connection units; Step 3: Processing the obtained C / SiC stress field and the three-directional internal force loads of the connection units to obtain the main strength and the strength of the connecting rivets of the C / SiC skin skeleton structure formed using the CVI process.

[0006] Further, in step one, establishing the equivalent connection unit specifically includes: S1.1: Traversing all rivets in the geometric model of the C / SiC skin skeleton structure and extracting the geometric information of the rivets based on their geometric models; S1.2: Grouping the rivet geometric information obtained in S1.1, with rivet geometric information being identical within the same group; S1.3: Defining independent connection unit Connector section attributes for each rivet group, including the connection unit type, stiffness values ​​in the three translational degrees of freedom, and stiffness values ​​in the three rotational degrees of freedom; S1.4: Traversing all rivets in S1.1, establishing local Connector connection units at the locations of all rivets, and assigning the local Connector connection units the connection unit Connector section attributes established in S1.3.

[0007] Furthermore, the geometric information of the rivet includes: rivet diameter, rivet length, and rivet axis direction.

[0008] Furthermore, in step one, HyperMesh is used to establish a finite element model of the C / SiC skin skeleton structure excluding the rivets. The rivets used for connecting the skin skeleton are automatically established by running the HyperMesh Tcl script program to create equivalent connection units (Connectors).

[0009] Further, in step two, applying thermal expansion deformation to the connecting unit specifically includes: S2.1: obtaining the temperature value of the finite element mesh node where the current connecting unit is located; S2.2: obtaining the amount of thermal deformation based on the temperature value obtained in S2.1 and the linear expansion coefficient of C / SiC at the current temperature; S2.3: decomposing the amount of thermal deformation obtained in S2.2 onto the three translational degrees of freedom of the connecting unit.

[0010] Furthermore, in step two, the thermal intensity of the established C / SiC skin skeleton structure model is calculated in Abaqus.

[0011] Furthermore, in step three, the main strength of the C / SiC skin skeleton structure is obtained by observing the stress field cloud map.

[0012] Further, in step three, obtaining the strength of the connecting rivet specifically includes: S3.1: Calculating the magnitude of the vector sum of the shear forces of the connecting unit perpendicular to its axis direction based on the three-directional internal force loads of the connecting unit obtained in step two; S3.2: Obtaining the stress of the rivet under shear force based on the vector sum of the shear forces obtained in S3.1 and the cross-sectional area of ​​the rivet corresponding to the connecting unit, and thus obtaining the strength of the connecting rivet.

[0013] Further, in step three, the strength of the rivets used for connection is calculated in Abaqus.

[0014] This invention provides a method for evaluating the thermal strength of C / SiC skin skeleton structures formed using the CVI process. This method models the C / SiC skin skeleton structure, including rivets used for connecting the skin skeleton, formed using the CVI process. During the thermal strength calculation, thermal expansion deformation is applied to the connecting units to obtain the C / SiC stress field and the three-directional internal force loads of the connecting units. This allows for the acquisition of the main strength of the C / SiC skin skeleton structure and the strength of the connecting rivets. This method automates the creation of a large number of rivet connecting units, accurately simulates the force transmission characteristics of rivets in C / SiC skin skeleton structures formed using the CVI process, and provides more realistic strength calculation results. Compared with existing technologies, this invention solves the technical problem of insufficient accuracy in thermal strength data for C / SiC skin skeleton structures formed using the CVI process due to the lack of consideration for connecting rivets. Attached Figure Description

[0015] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0016] Figure 1 A schematic flowchart of a method for evaluating the thermal strength of a C / SiC skin skeleton structure based on CVI process, according to a specific embodiment of the present invention, is shown. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0019] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0020] like Figure 1As shown in the figure, a method for evaluating the thermal strength of a C / SiC skin skeleton structure formed by CVI process is provided according to a specific embodiment of the present invention. The method includes: modeling the C / SiC skin skeleton structure formed by CVI process, wherein the rivets used for connecting the skin skeleton are realized by establishing equivalent connection units; performing thermal strength calculation on the established C / SiC skin skeleton structure model, applying thermal expansion deformation to the connection units during the thermal strength calculation process to obtain the C / SiC stress field and the three-directional internal force load of the connection units; processing the obtained C / SiC stress field and the three-directional internal force load of the connection units to obtain the main body strength and the strength of the connecting rivets of the C / SiC skin skeleton structure formed by CVI process.

[0021] This method provides a thermal strength evaluation method for C / SiC skin skeleton structures formed using the CVI process. The method models the C / SiC skin skeleton structure, including the rivets used for connecting the skin skeleton, and applies thermal expansion deformation to the connecting units during thermal strength calculation. This yields the C / SiC stress field and the three-directional internal force loads of the connecting units, thus obtaining the main strength and rivet strength of the C / SiC skin skeleton structure formed using the CVI process. This enables the automated creation of a large number of rivet connection units, accurately simulating the force transmission characteristics of the rivets in the C / SiC skin skeleton structure formed using the CVI process, resulting in more realistic strength calculation results. Compared with existing technologies, this invention solves the technical problem of insufficient accuracy in thermal strength data for C / SiC skin skeleton structures formed using the CVI process due to the lack of consideration for connecting rivets.

[0022] Furthermore, in this invention, to evaluate the thermal strength of the C / SiC skin skeleton structure formed using the CVI process, the C / SiC skin skeleton structure is first modeled. The rivets used for connecting the skin skeleton are implemented by establishing equivalent connection units. In this invention, the C / SiC skin skeleton structure is formed using the CVI process, and its typical structural feature is that all skin skeleton structures are connected online using a large number of rivets.

[0023] Furthermore, establishing equivalent connection units specifically includes:

[0024] S1.1: Traverse all rivets in the geometric model of the C / SiC skin skeleton structure and extract the geometric information of the rivets based on their geometric models. The geometric information of the rivets includes the rivet diameter, rivet length, and rivet axis direction. In this invention, the rivet geometric model should be complete and without defects, possessing a regular and uniform topological structure.

[0025] S1.2: Group the rivet geometry information obtained in S1.1, with rivets in the same group having the same geometry information. That is, rivets of the same length and orientation are placed in the same group.

[0026] S1.3: Define independent Connector section properties for each rivet group. The Connector section properties include the Connector type, stiffness values ​​in the three translational degrees of freedom, and stiffness values ​​in the three rotational degrees of freedom.

[0027] S1.4: Traverse all rivets in S1.1, create local Connector connection units at the locations of all rivets, and assign the Connector section properties created in S1.3 to the local Connector connection units.

[0028] As a specific embodiment of the present invention, HyperMesh can be used to establish a finite element model of the C / SiC skin skeleton structure excluding rivets. The rivets used for connecting the skin skeleton are automatically established by running the Tcl script program of HyperMesh to create equivalent connection units Connector.

[0029] Furthermore, in this invention, after modeling the C / SiC skin skeleton structure formed by CVI process, thermal strength calculation is performed on the established C / SiC skin skeleton structure model. During the thermal strength calculation, thermal expansion deformation is applied to the connecting unit to obtain the C / SiC stress field and the three-directional internal force load of the connecting unit.

[0030] Furthermore, applying thermal expansion deformation to the connecting unit specifically includes:

[0031] S2.1: Obtain the temperature value of the finite element mesh node where the current connected element is located;

[0032] S2.2: Obtain the thermal deformation amount based on the temperature value obtained in S2.1 and the linear expansion coefficient of C / SiC at the current temperature;

[0033] S2.3: Decompose the thermal deformation obtained in S2.2 onto the three translational degrees of freedom of the connecting element. This allows the thermal deformation to be transferred to the connecting element. This step can eliminate spurious thermal stress in the thermal strength calculation and improve the accuracy of the structural strength calculation.

[0034] As a specific embodiment of the present invention, thermal intensity calculations can be performed on the established C / SiC skin skeleton structure model in Abaqus.

[0035] Furthermore, in this invention, after obtaining the C / SiC stress field and the three-directional internal force loads of the connecting unit, the obtained C / SiC stress field and the three-directional internal force loads of the connecting unit are processed to obtain the main body strength and the connecting rivet strength of the C / SiC skin skeleton structure formed based on the CVI process.

[0036] Furthermore, obtaining the strength of the connecting rivets specifically includes:

[0037] S3.1: Calculate the magnitude of the vector sum of the shear forces of the connecting unit perpendicular to its axis based on the obtained three-directional internal force loads of the connecting unit;

[0038] S3.2: Based on the vector sum of shear forces obtained in S3.1 and the cross-sectional area of ​​the rivet corresponding to the connecting unit, obtain the stress of the rivet under shear force and obtain the strength of the connecting rivet.

[0039] As a specific embodiment of the present invention, the main strength of the C / SiC skin skeleton structure can be obtained by observing the stress field cloud map, and the strength of the connecting rivets can be calculated in Abaqus.

[0040] This invention provides a method for evaluating the thermal strength of C / SiC skin skeleton structures formed using the CVI process. This method automates the creation of large-scale rivet connection units, accurately simulates the force transmission characteristics of rivets in C / SiC skin skeleton structures formed using the CVI process, and yields more realistic strength calculation results. Compared with existing technologies, this invention has the following advantages:

[0041] 1) In the connection of skin skeleton of C / SiC structure formed by CVI process, the riveting connection effect is simulated by establishing the same proportional equivalent connection unit, accurately reproduces the force transmission characteristics of rivet, thereby solving the problem of force transmission path deviation, and can accurately obtain the stress field and temperature field of the structure.

[0042] 2) This invention, through accurate modeling of the force transmission path of C / SiC formed by CVI process, can effectively identify the weak points in the structure, avoid repeated iterations of structural schemes, and save the time for structural strength calculation.

[0043] 3) This invention, through accurate modeling of the force transmission path of C / SiC formed by CVI process, can obtain the tensile and shear loads of all rivets in C / SiC, obtain rivet strength data, and the rivet equivalent stiffness parameter adjustment is very flexible, improving the completeness of structural strength calculation.

[0044] 4) By applying thermal expansion deformation to the connecting unit, the present invention can eliminate false thermal stress in the thermal strength calculation and improve the accuracy of the structural strength calculation.

[0045] To provide a further understanding of the present invention, specific embodiments are provided below to illustrate the method for evaluating the thermal strength of C / SiC skin skeleton structures based on CVI process.

[0046] Example

[0047] Step 1: Use HyperMesh to build a finite element model of the C / SiC skin skeleton structure excluding the rivets. The rivets used for connecting the skin skeleton are automatically generated by running the HyperMesh Tcl script program to create equivalent connection units (Connectors).

[0048] Specifically, the Connector, which establishes the equivalent connection unit, includes:

[0049] S1.1: Create a component in HyperMesh and place all rivet geometries within it. The rivet geometries are not meshed. Run the HyperMesh Tcl script to traverse all rivets in the C / SiC skinned skeleton structure geometric model and extract the rivet geometric information based on the rivet geometric model. The rivet geometric information includes the rivet diameter, rivet length, and rivet axis direction. In this invention, the rivet geometric model should be complete and without defects, possessing a regular and uniform topological structure.

[0050] S1.2: Group the rivet geometry information obtained in S1.1, with rivets in the same group having the same geometry information. That is, rivets of the same length and orientation are placed in the same group.

[0051] S1.3: Define independent Connector section properties for each rivet group. The Connector section properties include the Connector type, stiffness values ​​in the three translational degrees of freedom, and stiffness values ​​in the three rotational degrees of freedom.

[0052] S1.4: Traverse all rivets in S1.1, create local Connector connection units at the locations of all rivets, and assign the Connector section properties created in S1.3 to the local Connector connection units.

[0053] Step 2: Perform thermal strength calculations on the C / SiC skin skeleton structure model established in Step 1 in Abaqus. During the thermal strength calculation, apply thermal expansion deformation to the connecting units to obtain the C / SiC stress field and the three-directional internal force loads of the connecting units.

[0054] Specifically, applying thermal expansion deformation to the connecting unit includes:

[0055] S2.1: Obtain the temperature value of the finite element mesh node where the current connected element is located through the Absqus subroutine MPC;

[0056] S2.2: In the subroutine MPC, the amount of thermal deformation is obtained based on the temperature value obtained in S2.1 and the coefficient of linear expansion of C / SiC at the current temperature;

[0057] S2.3: In the subroutine MPC, the thermal deformation obtained in S2.2 is decomposed onto the three translational degrees of freedom of the connecting elements. This allows the thermal deformation to be transferred to the connecting elements, eliminating spurious thermal stresses in the thermal strength calculation and improving the accuracy of structural strength calculations.

[0058] Step three involves processing the C / SiC stress field and the three-directional internal force loads of the connecting units obtained in step two to obtain the main strength and connecting rivet strength of the C / SiC skin skeleton structure formed by CVI process. The main strength of the C / SiC skin skeleton structure is obtained by observing the stress field contour map.

[0059] Specifically, obtaining the strength of the connecting rivets includes:

[0060] S3.1 Based on the three-directional internal force loads of the connecting unit obtained in step two, establish FieldOtput1 in Abaqus to calculate the magnitude of the vector sum of the shear forces of the connecting unit perpendicular to its axis.

[0061] S3.2 Based on the magnitude of the shear force vector sum obtained in S3.1 and the cross-sectional area of ​​the rivet corresponding to the connecting unit, a Field Otput2 is established in Abaqus to calculate the stress of the rivet under shear force. The stress cloud diagram is observed and compared with the rivet material strength to obtain the rivet strength.

[0062] In summary, this invention provides a method for evaluating the thermal strength of C / SiC skin skeleton structures formed using the CVI process. This method models the C / SiC skin skeleton structure, including the rivets used for connecting the skin skeleton, formed using the CVI process. During the thermal strength calculation, thermal expansion deformation is applied to the connecting units to obtain the C / SiC stress field and the three-directional internal force loads of the connecting units. This allows for the acquisition of the main strength of the C / SiC skin skeleton structure and the strength of the connecting rivets. This method automates the creation of a large number of rivet connecting units, accurately simulates the force transmission characteristics of the rivets in the C / SiC skin skeleton structure formed using the CVI process, and provides more realistic strength calculation results. Compared with existing technologies, this invention solves the technical problem of insufficient accuracy in thermal strength data for C / SiC skin skeleton structures formed using the CVI process due to the lack of consideration for connecting rivets.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for evaluating the thermal strength of a C / SiC skin skeleton structure formed by CVI process, characterized in that, The method for evaluating the thermal strength of the C / SiC skin skeleton structure formed by CVI process includes: Step 1: Model the C / SiC skin skeleton structure formed by CVI process, wherein the rivets used for skin skeleton connection are realized by establishing equivalent connection units; Step 2: Perform thermal strength calculation on the established C / SiC skin skeleton structure model. During the thermal strength calculation, apply thermal expansion deformation to the connecting unit to obtain the C / SiC stress field and the three-directional internal force load of the connecting unit. Step 3: Process the obtained C / SiC stress field and the three-directional internal force load of the connecting unit to obtain the main strength and the strength of the connecting rivets of the C / SiC skin skeleton structure formed by CVI process; In step one, establishing the equivalent connection unit specifically includes: S1.1: Traverse all rivets in the geometric model of the C / SiC skin skeleton structure and extract the geometric information of the rivets based on their geometric models; S1.2: Group the rivet geometry information obtained in S1.1, with rivet geometry information being the same within the same group; S1.3: Define independent Connector section properties for each rivet group. The Connector section properties include: Connector type, stiffness values ​​in three translational degrees of freedom, and stiffness values ​​in three rotational degrees of freedom. S1.4: Traverse all rivets in S1.1, create local Connector connection units at the locations of all rivets, and assign the Connector section properties of the connection unit created in S1.3 to the local Connector connection units; Step two, specifically, involves applying thermal expansion deformation to the connecting unit, including: S2.1: Obtain the temperature value of the finite element mesh node where the current connected element is located; S2.2: The amount of thermal deformation is obtained based on the temperature value obtained in S2.1 and the coefficient of linear expansion of C / SiC at the current temperature; S2.3: Decompose the thermal deformation obtained in S2.2 into the three translational degrees of freedom of the connecting unit; In step two, thermal strength calculations are performed on the established C / SiC skin skeleton structure model in Abaqus; Step three, specifically, includes obtaining the strength of the connecting rivet: S3.1: Calculate the magnitude of the vector sum of the shear forces of the connecting unit perpendicular to its axis direction based on the three-directional internal force loads of the connecting unit obtained in step two; S3.2: Based on the vector sum of shear forces obtained in S3.1 and the cross-sectional area of ​​the rivet corresponding to the connecting unit, obtain the stress of the rivet under shear force and obtain the strength of the connecting rivet.

2. The method for evaluating the thermal strength of a C / SiC skin skeleton structure formed by CVI process according to claim 1, characterized in that, The geometric information of the rivet includes: rivet diameter, rivet length, and rivet axis direction.

3. The method for evaluating the thermal strength of a C / SiC skin skeleton structure formed by CVI process according to claim 1, characterized in that, In step one, HyperMesh is used to establish a finite element model of the C / SiC skin skeleton structure excluding the rivets. The rivets used for connecting the skin skeleton are automatically established by running the HyperMesh Tcl script program to create equivalent connection units (Connectors).

4. The method for evaluating the thermal strength of a C / SiC skin skeleton structure formed by CVI process according to claim 1, characterized in that, In step three, the main strength of the C / SiC skin skeleton structure is obtained by observing the stress field cloud map.

5. The method for evaluating the thermal strength of a C / SiC skin skeleton structure formed by CVI process according to claim 1, characterized in that, In step three, the strength of the rivets used for connection is calculated in Abaqus.

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