Method, device and equipment for evaluating residual stress of composite material and medium

Abstract

The invention provides a residual stress assessment method, device and equipment for a composite material and a medium, relates to the field of composite material processing, manufacturing and forming, and aims to solve the problem of how to accurately assess residual stress after curing deformation and forced assembly of the composite material. The method comprises the following steps: establishing a composite material skin curing deformation analysis model, and simulating and calculating the skin curing deformation through a thermal-mechanical coupling method; by taking the frame as a benchmark, forcibly assembling the skin and the frame by applying a load; unloading the load after forced assembly to obtain an integral structure of the cabin door; according to the skin curing deformation, the deformation of the overall structure of the cabin door is solved through a mechanical equilibrium equation; calculating the strain of each position in the cabin door according to the deformation of the overall structure of the cabin door; and calculating the residual stress of each position in the cabin door according to the strain of each position in the cabin door and the elastic modulus of the composite material.

Description

Technical Field

[0001] The present application relates to the field of composite material processing, manufacturing and forming, and provides a method, device, equipment and medium for evaluating the residual stress of composite materials. Background Art

[0002] Thermosetting resin-based composite materials are widely used in the fields of aerospace, automobiles and rail transit tools. During the curing process, chemical reactions occur, transforming from a viscous flow state to a rubber state and finally to a glass state, and a certain amount of residual stress is stored during this process. Then, through demolding, the residual stress is released, resulting in a certain amount of curing deformation and residual stress. Higher residual stress will prematurely induce failure modes such as interlayer delamination, matrix-fiber interface damage, and matrix cracking in the composite material structure, leading to a decline in the performance of the composite material structure.

[0003] Currently, the main method for analyzing the strength of composite material connection structures is to assume that the assembly gap is uniform or wedge-shaped, and then analyze local details in combination with a finite element model. However, the existing technology ignores the actual assembly gap generated by curing deformation and the residual stress after removing the applied load after assembly is completed, resulting in low accuracy in the strength analysis of composite material structures. Summary of the Invention

[0004] The present application provides a method, device, equipment and medium for evaluating the residual stress of composite materials, which is used to solve the problem of how to accurately evaluate the residual stress after curing deformation and forced assembly of composite materials.

[0005] In a first aspect, the present application provides a method for evaluating the residual stress of composite materials, including: Establish an analysis model for the curing deformation of the composite skin, and simulate and calculate the skin curing deformation amount through a thermal-mechanical coupling method; Taking the frame as a reference, force the skin and the frame to be assembled by applying a load; After the forced assembly is completed, remove the load to obtain the overall structure of the hatch; According to the skin curing deformation amount, the stiffness matrix of the skin and the stiffness matrix of the overall structure of the hatch, calculate the deformation amount of the overall structure of the hatch; According to the deformation amount of the overall structure of the hatch and the strain matrix, calculate the strain at each position in the hatch; According to the strain at each position in the hatch and the elastic modulus of the composite material, calculate the residual stress at each position in the hatch.

[0006] Optionally, the step of forcing the skin and the frame to be assembled by applying a load with the frame as a reference includes: Apply a fixed support boundary condition to the frame; Taking the frame as a reference, a load is applied to the skin to make the skin fit with the frame; When the distance between the skin and the frame is less than a preset threshold, the connection unit is activated; the connection unit is used to simulate the connection between the skin and the frame.

[0007] Optionally, before activating the connection unit when the distance between the skin and the frame is less than a preset threshold, the method further includes: Determining the preset threshold according to half of the sum of the thickness of the skin and the thickness of the frame.

[0008] Optionally, the calculation formula of the preset threshold is as follows: d = t skin / 2 + t frame / 2 + Δ Wherein, d represents the preset threshold, t skin represents the thickness of the skin, t frame represents the thickness of the frame, and Δ represents the compensation amount.

[0009] Optionally, the calculation formula of the deformation amount of the overall structure of the hatch is as follows:

[0010] Wherein, {U} 1,all represents the deformation amount of the overall structure of the hatch, {U} 0,skin represents the curing deformation amount of the skin, [C] skin represents the stiffness matrix of the skin, [C] all represents the stiffness matrix of the overall structure of the hatch.

[0011] Optionally, the calculation formula of the strain is as follows:

[0012] Wherein, {ε} represents the strain at each position in the hatch, {U} 1,all represents the deformation amount of the overall structure of the hatch, represents the strain matrix.

[0013] Optionally, the calculation formula of the residual stress is as follows: {σ} = E·{ε} Wherein, {ε} represents the strain at each position in the hatch, E represents the elastic modulus of the composite material, and {σ} represents the residual stress at each position in the hatch.

[0014] In a second aspect, the present application provides a device for evaluating the residual stress of a composite material, including: A simulation module, configured to establish an analysis model for the curing deformation of a composite skin, and simulate and calculate the curing deformation amount of the skin through a thermal-mechanical coupling method; A forced assembly module, configured to, with the frame as a reference, perform forced assembly on the skin and the frame by applying a load; after the forced assembly is completed, remove the load to obtain the overall structure of the hatch; A deformation amount calculation module, configured to calculate the deformation amount of the overall structure of the hatch according to the curing deformation amount of the skin, the stiffness matrix of the skin, and the stiffness matrix of the overall structure of the hatch; A strain calculation module, configured to calculate the strain at each position in the hatch according to the deformation amount of the overall structure of the hatch and the strain matrix; A residual stress calculation module, configured to calculate the residual stress at each position in the hatch according to the strain at each position in the hatch and the elastic modulus of the composite material.

[0015] In a third aspect, the present application provides a computer device, which includes a memory and a processor. A computer program is stored in the memory, and the processor executes the computer program to implement the method for evaluating the residual stress of the composite material described in the first aspect.

[0016] In a fourth aspect, the present application provides a computer-readable storage medium, on which a computer program is stored. The processor executes the computer program to implement the method for evaluating the residual stress of the composite material described in the first aspect.

[0017] Compared with the prior art, the beneficial effects of the present application are as follows: The present application provides a method for evaluating the residual stress of a composite material, which includes: establishing an analysis model for the curing deformation of a composite skin, and simulating and calculating the curing deformation amount of the skin through a thermal-mechanical coupling method; with the frame as a reference, performing forced assembly on the skin and the frame by applying a load; after the forced assembly is completed, removing the load to obtain the overall structure of the hatch; calculating the deformation amount of the overall structure of the hatch according to the curing deformation amount of the skin, the stiffness matrix of the skin, and the stiffness matrix of the overall structure of the hatch; calculating the strain at each position in the hatch according to the deformation amount of the overall structure of the hatch and the strain matrix; calculating the residual stress at each position in the hatch according to the strain at each position in the hatch and the elastic modulus of the composite material. It can be seen that for the hatch structure with a large curvature, the present application considers the actual assembly gap generated by the curing deformation of the skin, accurately simulates the forced assembly process of the skin and the frame by applying a load to eliminate the assembly gap, and then combines mathematical formulas to deduce the residual stress after removing the load after the assembly is completed, thereby improving the accuracy of the strength analysis of the composite material connection structure. Description of the Drawings

[0018] To more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following will briefly introduce the drawings required for the description of the embodiments or related technologies. Obviously, the drawings in the following description are only the embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0019] Figure 1 Schematic diagram of the computer device structure of the hardware operating environment involved in the solution of the embodiment of the present application; Figure 2 Schematic flow chart of a method for evaluating the residual stress of a composite material provided by an embodiment of the present application; Figure 3 Schematic diagram of converting isolated grids into surfaces after curing and forming provided by an embodiment of the present application; Figure 4 Schematic diagram of the finite element grid of the hatch structure provided by an embodiment of the present application; Figure 5 Schematic diagram of the forced assembly process provided by an embodiment of the present application; Figure 6 Schematic diagrams before and after forced assembly provided by an embodiment of the present application; Figure 7 Schematic diagram of the residual stress after forced assembly provided by an embodiment of the present application; Figure 8 Schematic diagram of the structure of a device for evaluating the residual stress of a composite material provided by an embodiment of the present application.

[0020] Reference numerals in the figure: 101 - processor, 102 - communication bus, 103 - network interface, 104 - user interface, 105 - memory. Detailed implementation manners

[0021] To make the objectives, technical solutions, and advantages of the present application clearer and more understandable, the following will clearly and completely describe the technical solutions in the embodiments of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts fall within the protection scope of the present application. Without conflict, the embodiments in the present application and the features in the embodiments can be combined arbitrarily with each other. And although the logical order is shown in the flow chart, in some cases, the steps shown or described can be executed in a different order than here.

[0022] Thermosetting resin-based composites have the characteristics of light weight, high specific strength and specific modulus, good fatigue resistance, and strong corrosion resistance, and are widely used in the fields of aerospace aircraft, automobiles, and rail transit tools. During the curing process of composites, chemical reactions occur, transforming from a viscous flow state to a rubber state and finally to a glass state, and a certain amount of residual stress is stored during this process. Then, through demolding, the residual stress is released, generating a certain amount of curing deformation and residual stress.

[0023] The curing deformation of composites greatly affects the forming accuracy of structural parts, resulting in relatively large assembly stresses or even abnormal assembly during subsequent assembly processes, thus affecting the overall structural strength and aerodynamic efficiency of the aircraft. The residual stress of composites usually does not directly lead to the failure of the composite structure, but higher residual stress will prematurely induce failure modes such as interlaminar delamination, matrix-fiber interface damage, and matrix cracking in the composite structure, leading to a decline in the performance of the composite structure. The hatch door panel structure of composites consists of skins, frames, and beams, with a large number of assembly structures. The curing deformation of composites will lead to the formation of assembly gaps, and these assembly gaps will cause a sharp increase in assembly stress during the connection process, which may trigger the generation and expansion of assembly damage, further increasing the complexity of the design and performance evaluation of composite connection structures.

[0024] The existing methods for analyzing the strength of composite connection structures mainly target flat joints of composites, assuming that the assembly gap shape is a uniform or wedge-shaped assembly gap, and using finite element models to analyze local details. The existing technologies have the following disadvantages: 1. It mainly considers the assumed uniform gap or wedge-shaped gap of the assembly gap shape, without considering the actual assembly gap generated by curing deformation.

[0025] 2. It mainly considers the stress generated during the forced assembly process, without considering the residual stress after removing the load applied during the forced assembly after the assembly is completed.

[0026] 3. It mainly targets single-lap joints of flat components at the component level, lacking the stress analysis of forced assembly for complex structures with large curvatures such as hatches.

[0027] In view of this, the embodiments of this application provide a method for evaluating the residual stress of composites, which can be executed by a computer device. Please refer to Figure 1 for the structural schematic diagram of the computer device of the hardware operating environment involved in the solution of the embodiments of this application.

[0028] As Figure 1As shown in the figure, the computer device may include: a processor 101, such as a Central Processing Unit (CPU), a communication bus 102, a user interface 104, a network interface 103, and a memory 105. Among them, the communication bus 102 is used to realize the connection and communication between these components. The user interface 104 may include a display screen (Display) and an input unit such as a keyboard (Keyboard). The user interface 104 may include a standard wired interface and a wireless interface. The network interface 103 may include a standard wired interface and a wireless interface (such as a Wireless-Fidelity (WI-FI) interface). The memory 105 may be a high-speed Random Access Memory (RAM) or a stable Non-Volatile Memory (NVM), such as a disk memory. The memory 105 may also be a storage device independent of the aforementioned processor 101.

[0029] Those skilled in the art can understand that Figure 1 the structure shown in the figure does not constitute a limitation on the computer device, and it may include more or fewer components than shown in the figure, or combine some components, or have different component arrangements.

[0030] As Figure 1 shown, the memory 105, as a storage medium, may include an operating system, a network communication module, a user interface module, and a residual stress evaluation device for a composite material.

[0031] In Figure 1 the computer device shown in the figure, the network interface 103 is mainly used for data communication with a network server; the user interface 104 is mainly used for data interaction with a user; the processor 101 and the memory 105 in the computer device of the present invention may be provided in the computer device. The computer device calls, through the processor 101, the residual stress evaluation device stored in the memory 105 and executes a residual stress evaluation method for a composite material provided in an embodiment of the present application.

[0032] Figure 1 The computer device described above is installed with ABAQUS software. As a finite element analysis tool, ABAQUS software can implement the residual stress evaluation method for a composite material provided in an embodiment of the present application.

[0033] Please refer to Figure 2 , which is a schematic flow diagram of a residual stress evaluation for a composite material provided in an embodiment of the present application. Based on Figure 1 the computer device shown in the figure, for Figure 2An introduction is given to a method for evaluating the residual stress of a composite material as shown.

[0034] S201. Establish an analysis model for the curing deformation of the composite skin, and simulate and calculate the curing deformation amount of the skin through a thermal-mechanical coupling method.

[0035] The curing deformation of a composite material refers to the change in shape or size caused by uneven internal stress in the composite material during the manufacturing process.

[0036] In the specific implementation process, the ABAQUS software is used to establish an analysis model for the curing deformation of the composite skin, and the thermal-mechanical coupling method is used for simulation calculation to obtain the curing deformation amount of the skin. Here, the curing deformation amount of the skin refers to the deformation amount of the skin during the curing process.

[0037] S202. Using the frame as a reference, force-fit the skin and the frame by applying a load.

[0038] Force-fit means a process method in which when parts cannot fit naturally due to dimensional deviation, deformation, or tolerance accumulation, an external force is applied to force the parts into place.

[0039] In the specific implementation process, first, import the cured and formed hatch skin structure into the ABAQUS software, and convert the isolated meshes into surfaces through the function of generating surfaces from meshes, as Figure 3 shown. Then, import the converted surfaces into CATIA for assembly. CATIA is a powerful three-dimensional computer-aided design (CAD) software that can perform multi-component assembly design and virtual assembly analysis. After completing the assembly in CATIA, import the assembled structure back into the ABAQUS software to create a finite element mesh, as Figure 4 shown. Finally, assign attributes to this finite element mesh, set the hard contact attribute globally to prevent inaccurate results caused by mesh penetration, and create connection units at the fastener connection points between the skin and the frame to simulate the connection between the skin and the frame.

[0040] In a possible embodiment, the specific steps of S202 include: Apply a fixed support boundary condition to the frame; apply a load on the skin to make the skin fit the frame; when the distance between the skin and the frame is less than a preset threshold, activate the connection unit. The connection unit is used to simulate the connection between the skin and the frame.

[0041] In the specific implementation process, the user can select the fixed boundaries of the box in the ABAQUS software. These boundaries are usually the support points or the positions of rigid fixation. Apply the fixed support boundary conditions to these positions to ensure that the nodes or surfaces at these positions cannot move during the forced assembly process, so that the box is in a constrained state. Further, the user can select the force-bearing area of the skin in the ABAQUS software, determine the position and type of the applied load, and apply an appropriate load to the force-bearing area on the surface of the skin. Since the gap between the skin and the box is relatively large, after applying the load on the skin, the gap will gradually shrink until they fit. When the mesh distance at the edge connection of the skin and the box is less than the preset threshold, the connection unit is activated.

[0042] Please refer to Figure 5 , which is a schematic diagram of the forced assembly process provided by the embodiment of the present application. Among them, the curved structure represents the skin, and the arrow represents the position and direction of the applied load.

[0043] In the embodiment of the present application, the process of implementing the fixed support boundary condition, load application, contact analysis and activation of the connection unit between the skin and the frame in ABAQUS is carried out, so as to simulate the forced assembly process of the skin and the frame, and ensure the authenticity and reliability of the model.

[0044] In a possible embodiment, before activating the connection unit when the distance between the skin and the box is less than the preset threshold, the method further includes: Determine the preset threshold according to the thickness of the skin and the thickness of the box.

[0045] In a possible embodiment, the calculation formula of the preset threshold is as follows: d=t skin / 2+t frame / 2 Where d represents the preset threshold, and t skin represents the thickness of the skin, and t frame represents the thickness of the box.

[0046] In another possible embodiment, the calculation formula of the preset threshold is as follows: d=t skin / 2+t frame / 2+Δ Where d represents the preset threshold, and t skin represents the thickness of the skin, and t frame represents the thickness of the box, and Δ represents the compensation amount. Δ is usually an empirical value obtained based on experimental data or simulation verification, and generally takes 0.1mm.

[0047] In the embodiment of the present application, t skin / 2+t frame / 2 represents the middle position of the theoretical contact surface between the skin and the frame. When the mesh spacing reaches this value, it is considered that the skin and the frame have achieved physical contact. Considering factors such as geometric errors, discretization errors, and surface fitting deviations that may occur in actual engineering, adding a compensation amount when setting the preset threshold can effectively improve the accuracy of the simulation results and avoid misjudgment of the contact state due to minor errors. Especially in the case of complex curved surfaces and composite material skins, it is often necessary to compensate for errors to ensure more accurate contact determination.

[0048] S203. After the forced assembly is completed, unload the load to obtain the overall structure of the hatch.

[0049] After the forced assembly process between the skin and the frame is completed, unload the applied load. Since the applied pressure is small and the applied load is small, the skin is still in the elastic stage and has a tendency to return to the historical state before the load was applied after unloading, which can well simulate the forced assembly process between the skin and the frame.

[0050] Please refer to Figure 6 , which is a schematic diagram before and after the forced assembly provided by the embodiment of the present application. It can be seen that there is a gap between the skin and the frame before the forced assembly, and there is no gap between the skin and the frame after the forced assembly.

[0051] S204. Calculate the deformation amount of the overall structure of the hatch according to the curing deformation amount of the skin, the stiffness matrix of the skin, and the stiffness matrix of the overall structure of the hatch.

[0052] In the specific implementation process, since the deformation amount of the frame is much smaller than that of the skin, the skin is assembled onto the frame with the frame as the reference, that is, the frame is in a constrained state. At this time, the deformation amount of the frame is {U} 0,frame = 0. There is a gap between the skin and the frame due to the curing deformation of the skin, and the size of the gap is equal to the curing deformation amount {U} 0,skin . The process of forced assembly of the skin and the frame to make them fit is also the process of eliminating this gap. At this time, the deformation amount of the skin relative to the state after demolding is -{U} 0,skin .

[0053] It should be noted that with the frame with a smaller deformation amount as the reference, assuming that the skin has no curing deformation, the skin can fit with the frame edge without forced assembly after demolding. It is precisely because the skin has a curing deformation amount {U} 0,skin , at this time, the gap between the skin and the frame edge is equal to the curing deformation amount {U} 0,skin , and the process of forced assembly is to press the skin towards the frame edge to make it fit with the frame edge. Therefore, the deformation amount of the skin relative to the state after demolding is -{U} 0,skin .

[0054] After the applied load is removed after assembly, the internal skin force generated by forced assembly will cause the skin to rebound. Due to the connection effect of the fasteners, the skin and the frame edge are deformed in coordination at the fastener connection. At this time, the deformation of the overall structure of the hatch is {U} 1,all .

[0055] According to Hooke's law: F f-s =(-{ U} 0,skin +{ U} 1,all )· C ) skin F s-f ={ U} 1,all · C ) frame Among them, F f-s represents the force exerted by the frame edge on the skin, -{U} 0,skin represents the deformation of the skin relative to the state after demolding, { U} 1,all represents the deformation of the overall structure of the hatch, C ) skin represents the stiffness matrix of the skin. F s-f represents the force exerted by the skin on the frame edge, C ) frame represents the stiffness matrix of the frame.

[0056] At this time, the overall structure of the hatch is in a balanced state. According to Newton's third law: the force exerted by the frame edge on the skin and the reaction force of the skin on the frame edge are equal in magnitude and opposite in direction, that is F f-s =- F s-f , and then the following formula can be obtained: (-{ U} 0,skin +{ U} 1,all )· C ) skin =-{ U} 1,all · C ) frame Furthermore, through matrix operations, it can be obtained:

[0057] Among them, {U}1,all Indicates the deformation of the overall structure of the hatch door, {U} 0,skin Indicates the curing deformation of the skin, [C] skin Indicates the stiffness matrix of the skin, [C] all Indicates the stiffness matrix of the overall structure of the hatch door.

[0058] S205. Calculate the strain at each position in the hatch door according to the deformation and strain matrix of the overall structure of the hatch door.

[0059] In the specific implementation process, the calculation formula for strain is as follows:

[0060] Among them, {ε} represents the strain at each position in the hatch door, {U} 1,all Indicates the deformation of the overall structure of the hatch door, Indicates the strain matrix.

[0061] S206. Calculate the residual stress at each position in the hatch door according to the strain at each position in the hatch door and the elastic modulus of the composite material.

[0062] In the specific implementation process, the calculation formula for residual stress is as follows: {σ}=E·{ε} Among them, {ε} represents the strain at each position in the hatch door, E represents the elastic modulus of the composite material, and {σ} represents the residual stress at each position in the hatch door.

[0063] Please refer to Figure 7 , for the schematic diagram of the residual stress after forced assembly provided by the embodiment of the present application.

[0064] In summary, the present application provides a method for evaluating the residual stress of composite materials, which can accurately simulate the forced assembly stress during assembly of the assembly gap caused by the thermosetting deformation of the skin of a large-curvature composite material hatch door, and provide support for the damage assessment that may be caused by forced assembly. This method can consider the residual stress after forced assembly in the load analysis of the composite material hatch door structure, and can improve the accuracy of the strength analysis of the composite material connection structure. This method can be applied to similar analyses of aircraft composite material panel structures.

[0065] Based on the same inventive concept, please refer to Figure 8 , the present application also provides a device for evaluating the residual stress of composite materials, and the device includes: A simulation module, configured to establish an analysis model for the curing deformation of the composite material skin, and simulate and calculate the curing deformation of the skin by means of a thermal-mechanical coupling method; A forced assembly module is used to perform forced assembly on the skin and the frame by applying a load with the frame as a reference; after the forced assembly is completed, the load is removed to obtain the overall structure of the hatch. A deformation calculation module is used to calculate the deformation of the overall structure of the hatch according to the curing deformation of the skin, the stiffness matrix of the skin, and the stiffness matrix of the overall structure of the hatch. A strain calculation module is used to calculate the strain at each position in the hatch according to the deformation of the overall structure of the hatch and the strain matrix. A residual stress calculation module is used to calculate the residual stress at each position in the hatch according to the strain at each position in the hatch and the elastic modulus of the composite material.

[0066] It should be noted that in this embodiment, the processor corresponds to each step in the method for evaluating the residual stress of a composite material in the foregoing embodiment. Therefore, the specific implementation manner of this embodiment can refer to the implementation manner of the method for evaluating the residual stress of a composite material described above, and will not be elaborated here.

[0067] Based on the same inventive concept, the present application also provides a computer device, which includes a processor, a memory, and a computer program stored in the memory. When the computer program is run by the processor, it implements the foregoing method for evaluating the residual stress of a composite material.

[0068] Based on the same inventive concept, the present application also provides a computer storage medium, on which a computer program is stored. When the computer program is run by the processor, it implements the foregoing method for evaluating the residual stress of a composite material.

[0069] In some embodiments, the computer-readable storage medium may be a memory such as FRAM, ROM, PROM, EPROM, EEPROM, flash memory, magnetic surface memory, optical disc, or CD-ROM; or it may be various devices including one or any combination of the above memories. The computer may be various computing devices including intelligent terminals and servers.

[0070] In some embodiments, the executable instructions may be in the form of a program, software, software module, script, or code, and may be written in any form of programming language (including compiled or interpreted languages, or declarative or procedural languages), and may be deployed in any form, including being deployed as an independent program or being deployed as a module, component, subroutine, or other unit suitable for use in a computing environment.

[0071] By way of example, the executable instructions may or may not correspond to files in a file system, and may be stored as part of a file that holds other programs or data. For example, they may be stored in one or more scripts in a Hyper Text Markup Language (HTML) document, in a single file dedicated to the program in question, or in multiple cooperating files (such as files that store one or more modules, subroutines, or portions of code).

[0072] By way of example, the executable instructions may be deployed to execute on one computing device, or on multiple computing devices located at one site, or alternatively, on multiple computing devices distributed across multiple sites and interconnected by a communication network.

[0073] It should be noted that, in this document, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or system that includes a series of elements includes not only those elements but also other elements not expressly listed, or elements that are inherent to such process, method, article or system. Without further limitation, an element qualified by the phrase "including a..." does not exclude the presence of additional identical elements in the process, method, article or system that includes such element.

[0074] The serial numbers of the embodiments of the present application above are for description only and do not represent the superiority or inferiority of the embodiments.

[0075] From the description of the above embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus a necessary general hardware platform. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as a read-only memory / random access memory, magnetic disk, optical disk), and includes several instructions for causing a multimedia terminal device (which may be a mobile phone, a computer, a television receiver, or a network device, etc.) to execute the methods described in the various embodiments of the present application.

[0076] The above are only the preferred embodiments of the present application, and do not limit the patent scope of the present application accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present application.

Claims

1. A method for evaluating the residual stress of a composite material, characterized in that, Including: Establish a curing deformation analysis model for the composite skin, and simulate and calculate the curing deformation amount of the skin through a thermal-mechanical coupling method; Taking the frame as a reference, perform forced assembly on the skin and the frame by applying a load; After the forced assembly is completed, remove the load to obtain the overall structure of the hatch; Calculate the deformation amount of the overall structure of the hatch according to the curing deformation amount of the skin, the stiffness matrix of the skin, and the stiffness matrix of the overall structure of the hatch; Calculate the strain at each position in the hatch according to the deformation amount of the overall structure of the hatch and the strain matrix; Calculate the residual stress at each position in the hatch according to the strain at each position in the hatch and the elastic modulus of the composite material.

2. The method for evaluating the residual stress of the composite material according to claim 1, wherein, The step of performing forced assembly on the skin and the frame by applying a load with the frame as a reference includes: Apply a fixed support boundary condition to the frame; Taking the frame as a reference, apply a load on the skin to make the skin fit with the frame; When the distance between the skin and the frame is less than a preset threshold, activate the connection unit; the connection unit is used to simulate the connection between the skin and the frame.

3. The method for evaluating the residual stress of the composite material according to claim 2, wherein Before activating the connection unit when the distance between the skin and the frame is less than a preset threshold, the method further includes: Determine the preset threshold according to half of the sum of the thickness of the skin and the thickness of the frame.

4. The method for evaluating the residual stress of the composite material according to claim 3, wherein The calculation formula of the preset threshold is as follows: d = t skin / 2 + t frame / 2 + Δ where d represents the preset threshold, t skin represents the thickness of the skin, t frame represents the thickness of the frame, and Δ represents the compensation amount.

5. The method for evaluating the residual stress of the composite material according to claim 1, characterized in that, The calculation formula of the deformation amount of the overall structure of the hatch is as follows: Among them, {U} 1,all represents the deformation amount of the overall structure of the hatch, {U} 0,skin represents the curing deformation amount of the skin, [C] skin represents the stiffness matrix of the skin, [C] all represents the stiffness matrix of the overall structure of the hatch.

6. The method for evaluating the residual stress of the composite material according to claim 1, wherein The calculation formula of the strain is as follows: where {ε} represents the strain at each position in the hatch door, and {U} 1,all represents the deformation of the overall structure of the hatch door, represents the strain matrix.

7. The method for evaluating the residual stress of the composite material according to claim 1, characterized in that, The calculation formula of the residual stress is as follows: {σ}=E·{ε} Wherein, {ε} represents the strain at each position in the hatch, E represents the elastic modulus of the composite material, and {σ} represents the residual stress at each position in the hatch.

8. A residual stress evaluation device for a composite material, characterized in that, Including: A simulation module, which is used to establish a curing deformation analysis model for the composite skin, and simulate and calculate the curing deformation amount of the skin through a thermal-mechanical coupling method; A forced assembly module, which is used to perform forced assembly on the skin and the frame by applying a load with the frame as a reference; after the forced assembly is completed, remove the load to obtain the overall structure of the hatch; A deformation amount calculation module, which is used to calculate the deformation amount of the overall structure of the hatch according to the curing deformation amount of the skin, the stiffness matrix of the skin, and the stiffness matrix of the overall structure of the hatch; A strain calculation module, which is used to calculate the strain at each position in the hatch according to the deformation amount of the overall structure of the hatch and the strain matrix; A residual stress calculation module, which is used to calculate the residual stress at each position in the hatch according to the strain at each position in the hatch and the elastic modulus of the composite material.

9. A computer device, characterized in that, The computer device includes a memory and a processor, and a computer program is stored in the memory. The processor executes the computer program to implement the method for evaluating the residual stress of the composite material as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, A computer program is stored on the computer-readable storage medium, and the processor executes the computer program to implement the method for evaluating the residual stress of the composite material as described in any one of claims 1-7.

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