Method for quantizing single-layer loading of coupling structural member in movement process and application thereof

Abstract

The invention relates to the technical field of crossing of material mechanics and intelligent detection, and discloses a method for quantifying single-layer loading of a coupling structural member in a movement process and application of the method. The method comprises the following steps: 1, determining a mechanical property test item, and preparing a to-be-tested coupling structural member into a standard test piece corresponding to the mechanical property test item; 2, forming a speckle pattern on the standard test piece to obtain a test piece to be tested; 3, performing a mechanical property test on the test piece to be tested, and obtaining an axial dependent variable epsilon y of a single-layer material by adopting a DIC method in a material elastic deformation stage in the test process; and 4, calculating the axial load and / or the transverse load of the single-layer material according to the formula 1-the formula 4. The quantification method provided by the invention is combined with a DIC method and material mechanics calculation, can perform quantitative analysis on the loading condition of the single-layer material of the coupled structural member, and particularly has relatively high practical value and guiding significance on axial mechanical behavior analysis of the single-layer material in the multi-layer coupled structural member.

Description

Technical Field

[0001] The present invention relates to the technical field of intersection of material mechanics and intelligent detection, and in particular to a method for quantifying the single-layer load of a coupled structural component during movement and an application thereof. Background Art

[0002] Coupled structural components are high-performance components that combine multiple excellent properties by combining two or more different materials or functional layers through interlayer bonding / interface design. Taking organic glass coupled structural components as an example, PMMA (polymethyl methacrylate), TPU (polyurethane), and PC (polycarbonate) offer advantages such as high light transmittance (e.g., PMMA transmittance ≥92%, PC transmittance ≥85%), strong impact resistance, good resistance to environmental aging, and lightweight. Coupled structural components composed of PMMA, TPU, and PC are widely used in aircraft canopies, automotive windshields, and electronic equipment protective cases.

[0003] The mechanical properties of the various layers of material in a coupled structural component vary significantly. Failure of such a coupled structural component is often related to the performance shortcomings of the individual layers of glass. For example, in a PMMA+TPU+PC coupled transparent component, PMMA has poor impact resistance, TPU has low environmental stability, and PC has poor heat resistance. Furthermore, during actual use, the various layers of material in the coupled structural component experience different stress states and uneven stress distribution, which can lead to delamination of the TPU intermediate layer, the formation of silver streaks in the single layer, and the expansion of microcracks that can cause cracking or overall failure.

[0004] Currently, there are two main methods for quantitatively analyzing the stress conditions of single-layer materials in such coupled structural components during motion. One is to combine the Classical Lamination Theory (CLT) and treat the multilayer material as a single isotropic material, ignoring interlayer shear and interfacial bonding effects and mechanical responses in the thickness direction. For example, when testing the mechanical properties of typical glass components in coupled structures, the stiffness and strength of the single-layer materials of the multilayer glass are generally transformed and superimposed, and the final sum is regarded as the stiffness and strength of the coupled structural glass. However, due to the simplification of material properties and the neglect of interlayer forces, this test method has limited descriptions of the environment and damage mechanisms, and therefore cannot effectively quantify the stress conditions of the single-layer coupled structural glass. At the same time, because the multilayer material is treated as an isotropic material, the interlayer load cannot be evaluated, and there is a lack of experience with potential structural component failures caused by the anisotropy of the interlayer materials, which restricts reliability design.

[0005] Another method is to use strain gauges to measure the strain of a single layer of material. However, this method suffers from the corrosive effects of the glue used to attach the strain gauges to organic materials. Furthermore, attaching the strain gauges requires roughening the surface, which introduces defects into the material. In mechanical testing, especially fatigue testing, these defects can have a significant impact on test results. Furthermore, the strain gauges are connected to the test leads via solder joints, which can easily break during operation, increasing test costs and reducing success rates, making this a very uneconomical testing method.

[0006] Therefore, it is urgent to provide a method that can well quantify the loading conditions of a single layer of a coupled structure during motion. Summary of the Invention

[0007] To address the aforementioned issues in the prior art, the present invention provides a method and application for quantifying the loads applied to a single layer of a coupled structural component during motion. This quantification method, combined with DIC and material mechanics calculations, enables quantitative analysis of the loads applied to a single layer of a coupled structural component. This method, in particular, offers significant practical value and guidance for analyzing the axial mechanical behavior of a single layer of material in a multilayer coupled structural component.

[0008] In order to solve the above problem, a first aspect of the present invention provides a method for quantifying the load on a single layer of material during the movement of a coupling structure, wherein the method comprises the following steps: (1) Determine the mechanical performance test items and prepare the coupling structure to be tested into standard test pieces corresponding to the mechanical performance test items; (2) forming a speckle pattern on the standard test piece to obtain a test piece; (3) Perform the mechanical property test on the test piece. During the elastic deformation stage of the material during the test, the axial strain ε of the single-layer material is obtained by using the DIC method. y ; (4) Calculate the axial load and / or lateral load of a single layer of material according to Equations 1 to 4: ; Among them, ε y is the axial strain of the single-layer material,‰; ε x is the lateral strain of the single-layer material, ‰; ν is the Poisson's ratio of the single-layer material; A is the cross-sectional area of ​​the single-layer material, unit: mm 2 ; d is the width of the single layer material, unit is mm; h is the thickness of the single layer material, unit is mm; E is the elastic modulus of the single layer material, unit is MPa; F x is the lateral load of a single layer of material, in kN; F y It is the axial load of a single layer of material, in kN.

[0009] A second aspect of the present invention provides an application of the method described in the first aspect of the present invention in the refined design of coupling structural parts.

[0010] Compared with the prior art, the present invention has the following beneficial technical effects: 1) The present invention provides a method for quantifying the load on a single layer of material during the motion of a coupled structural component. The method utilizes DIC to obtain the axial strain of the single layer of material. Combined with the elastic modulus and Poisson's ratio of the single layer of material, the lateral and axial load analysis of the single layer of material under overall load conditions can be performed. 2) The method provided by the present invention quantifies the loads on single-layer materials during the motion of coupled structural components. By analyzing the stress conditions of the single-layer materials, it can qualitatively identify the stress concentration areas, strain distribution characteristics, and possible failure modes of each single-layer material during the elastic deformation stage under axial tension, compression, shear, fatigue, and other stress conditions. This qualitative analysis of stress distribution and stress state provides a theoretical basis for optimizing material design, selecting interlayer interfaces (such as adhesive selection and thickness matching), and improving the reliability and lifespan of coupled structural glass. It also provides measured data support for mechanical modeling and simulation of composite structures. 3) The method provided by this invention for quantifying the loads on a single layer of a coupled structural component during motion can evaluate the interlaminar mechanical behavior of the coupled material under complex loads. The test data can be used to verify theoretical models (such as classical laminate theory) and to inform material selection, structural optimization, and lifespan prediction. Under standardized loading conditions, it can provide a theoretical basis for the engineering applicability and reliability of coupled structural components. 4) The method provided by this invention for quantifying the loads on a single layer of material during the motion of a coupled structural component is particularly suitable for dynamic deformation analysis of multi-layer coupled structural components (e.g., the magnitude of the material force under axial tensile load). It can intuitively reveal the damage evolution path of a single layer of material under complex loads, has high application value for analyzing the axial mechanical behavior of multi-layer coupled structures, and facilitates the refined design of high-performance coupled transparent structures. 5) The application of the method described in the first aspect of the present invention in the refined design of coupled structural parts provided by the present invention, by using the initial load setting value for the axial load calculation conditional fatigue limit test of the coupled structural parts obtained by the method described in the first aspect of the present invention, can reduce the usage of coupled structural parts, shorten the number of fatigue load tests of the coupled structural parts, and significantly improve the efficiency of fatigue load testing of the coupled structural parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 A schematic diagram of the present invention for collecting strain of a test piece using a DIC method; Figure 2 A schematic diagram of the calculation of Poisson's ratio provided by the present invention; Figure 3 A schematic diagram of the standard test piece in Example 1 provided by the present invention; Figure 4 Schematic diagram of the speckle capture method and strain distribution in Example 1 provided by the present invention. DETAILED DESCRIPTION

[0012] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0013] A first aspect of the present invention provides a method for quantifying the load on a single layer of material during the movement of a coupling structure, wherein the method comprises the following steps: (1) Determine the mechanical performance test items and prepare the coupling structure to be tested into standard test pieces corresponding to the mechanical performance test items; (2) forming a speckle pattern on the standard test piece to obtain a test piece; (3) Perform the mechanical property test on the test piece. During the elastic deformation stage of the material during the test, the axial strain ε of the single-layer material is obtained by using the DIC method. y ; (4) Calculate the axial load and / or lateral load of the single layer material according to Equations 1 to 4; ; Among them, ε y is the axial strain of the single-layer material,‰; ε x is the lateral strain of the single-layer material, ‰; ν is the Poisson's ratio of the single-layer material; A is the cross-sectional area of ​​the single-layer material, unit: mm 2 ; d is the width of the single layer material, unit is mm; h is the thickness of the single layer material, unit is mm; E is the elastic modulus of the single layer material, unit is MPa; F x is the lateral load of a single layer of material, in kN; F y It is the axial load of a single layer of material, in kN.

[0014] Among them, in the present invention, Poisson's ratio and elastic modulus can be obtained by consulting material manuals, professional material databases, or testing according to national standards. The method provided in the present invention for quantifying the stress on a single-layer material during the movement of a coupled structural component uses the DIC method to obtain the axial strain of the single-layer material, and combined with the elastic modulus and Poisson's ratio of the single-layer material, the axial and / or lateral load calculation of the single-layer material under overall loading conditions can be performed. Combined with the calculation results, the stress conditions of the single-layer material can be analyzed, and the stress concentration areas, strain distribution characteristics and possible failure modes of each single-layer material in the elastic deformation stage under axial tension, compression, shear, fatigue and other loading conditions can be qualitatively identified, providing a theoretical basis for optimizing material design, interlayer interface selection (such as adhesive selection, thickness matching), and improving the reliability and life of coupled structural glass.

[0015] In some embodiments of the present invention, the mechanical property test item is selected from one of fatigue test, tensile test, compression test and creep test.

[0016] Among them, in the present invention, when testing the mechanical properties of the material, it is necessary to first prepare the sample to be tested into a standard test piece according to the national standard. The preparation method of the standard test piece corresponding to different mechanical property tests is different. Taking fatigue testing as an example, the coupling structure to be tested can be prepared into a standard test piece with reference to GJB 2033-94, such as Figure 3 As shown. Among them, Figure 3 In the figure, d represents width and h represents thickness. The specific preparation method of the standard test piece can refer to the national standard, and the present invention will not elaborate on it one by one.

[0017] In some embodiments of the present invention, the coupling structure to be tested is not particularly limited; any coupling structure formed by stacking multiple layers of material can be used in the present invention. For example, the coupling structure can be a PMMA+TPU+PC coupling structure formed by sequentially combining PMMA (polymethyl methacrylate), TPU (polyurethane adhesive), and PC (polycarbonate).

[0018] In some embodiments of the present invention, speckle paper is affixed to the front and side surfaces of a coupling structure standard test piece to form a speckle pattern, thereby obtaining a test piece to be tested; alternatively, matte paint is sprayed on the front and side surfaces of the coupling structure standard test piece to produce speckles, thereby forming a speckle pattern, thereby obtaining a test piece to be tested.

[0019] In the present invention, the front side of the coupling structure standard test piece is the surface of the coupling structure standard test piece, and the side side of the coupling structure standard test piece is the cross section of the coupling structure standard test piece where the multilayer structure can be observed (e.g. Figure 4 ).

[0020] In some embodiments of the present invention, the matte paint includes matte white paint or matte black paint.

[0021] In this invention, matte white paint and matte black paint are not particularly limited; they can be selected based on common knowledge. Matte white paint can be paired with black speckle, and matte black paint can be paired with white speckle. This creates a high-contrast speckle pattern on the coupling structure standard test piece, providing capture sites for the DIC method. High contrast in this context refers to a sharp grayscale contrast and a speckle size and distribution that meets the camera's resolution.

[0022] In some embodiments of the present invention, the mechanical property test is performed on a mechanical testing device, such as a universal material testing machine.

[0023] In the present invention, the mechanical testing equipment is a materials testing machine that integrates tensile, bending, compression, shear, and fatigue testing functions. The mechanical testing equipment includes a loading device with displacement control and load measurement output. The test piece is clamped to the mechanical testing equipment by a clamping block or by fixing the upper and lower clamping surfaces. An axial load is applied to the test piece to test the mechanical properties of the material.

[0024] In some embodiments of the present invention, during the test, the universal material testing machine applies a load to the test piece, wherein the load is selected from at least one of axial tension, tension-shear, compression, and fatigue.

[0025] In some embodiments of the present invention, the mechanical property test item is a fatigue test, the cyclic load of the universal material testing machine is 30-60 MPa, the frequency is 0.5-5 Hz, and the universal material testing machine applies a force of 10-25 kN to the test piece.

[0026] In some embodiments of the present invention, DIC (Digital Image Correlation, DIC) is a digital image correlation technology. During the test process, a high-speed camera is used to capture areas with high-contrast points, and images of the material surface deformation are collected at a fixed frequency. The deformation of the speckle pattern at each frequency is compared based on the digital image correlation technology. The strain distribution cloud map and the stress-strain curve of the working section position are drawn to obtain the axial strain ε of each layer of material. y The schematic diagram of using DIC method to collect the strain of the test piece is as follows: Figure 1 shown.

[0027] Among them, in the present invention, the method of combining speckle pattern and DIC can avoid the influence of traditional strain gauge bonding method on the corrosion of organic glass or polycarbonate surface, and at the same time can accurately capture the mechanical behavior of the material's elastic deformation process. It can accurately measure the change of strain amount of each layer of material during the loading process, which helps to further improve the accuracy of load calculation results.

[0028] In some embodiments of the present invention, the fixed frequency of the high-speed camera is 50-100 Hz, preferably 40-60 Hz, for example, 50 Hz. In the present invention, the term "high-speed camera" has a meaning commonly known in the art. Limiting the fixed frequency of the high-speed camera to the above range can ensure clear, undistorted images during the capture process.

[0029] In some embodiments of the present invention,

[0030] Wherein, in formula 1, ν is the Poisson's ratio of the single-layer material, which refers to the ratio of the transverse normal strain to the axial normal strain when the material is subjected to unidirectional tension or compression, as shown in Figure 2 shown.

[0031] In some embodiments of the present invention,

[0032] In Equation 2, ν is the Poisson's ratio of the single-layer material, ε y is the axial type variable of the single layer material,‰; ε x is the lateral variable of the single-layer material, ‰; d is the width of the single-layer material, in mm; h is the thickness of the single-layer material, in mm.

[0033] In the present invention, Equation 2 is the formula for calculating the cross-sectional area of ​​a single layer of material. During the elastic deformation phase of actual testing, the specimen will deform during axial tension or compression, resulting in a change in cross-sectional area. The present invention incorporates Poisson's ratio into the calculation of cross-sectional area to correct for this and improve the accuracy of load calculation results.

[0034] In some embodiments of the present invention,

[0035] In Formula 3, F y It represents the axial load of a single layer of material in kN; E is the elastic modulus of a single layer of material in MPa, ε y is the axial strain of the single layer material, ‰; A is the cross-sectional area of ​​the single layer material, in mm 2 .

[0036] In some embodiments of the present invention,

[0037] In Formula 4, F x It represents the lateral load of a single layer of material in kN; E is the elastic modulus of a single layer of material in MPa, ε x is the transverse strain of the single layer material, ‰; A is the cross-sectional area of ​​the single layer material, in mm 2 .

[0038] A second aspect of the present invention provides an application of the method described in the first aspect of the present invention in the refined design of coupling structural parts.

[0039] Among them, in the present invention, the quantification method provided in the present invention can quantitatively analyze the load conditions of single-layer materials of coupled structural parts, especially the axial mechanical behavior analysis of single-layer materials in multi-layer coupled structural parts, which has high practical value and guiding significance.

[0040] In some embodiments of the present invention, the application includes the initial load setting value of the axial load calculation coupled structural component condition fatigue limit test calculated by the method according to the first aspect of the present invention; wherein the initial load setting value F0=F 总 -F 设 +F 理 , the unit is kN; among them, F 总 is the sum of the axial loads on the single-layer material calculated using the method of the present invention, F 设 The method of the present invention is used to calculate the axial force applied by the universal material testing machine when a single layer of material is axially loaded; F 理 The theoretical setting value is calculated by multiplying the tensile strength of the single layer material with the largest tensile strength in the coupled structure by 60% and multiplying it by the cross-sectional area (rectangular, undeformed area).

[0041] In this way, the usage of coupling structural parts can be reduced, the number of fatigue load tests of coupling structural parts can be shortened, the efficiency of fatigue load tests of coupling structural parts can be significantly improved, and thus it is helpful to carry out refined design of coupling structural parts.

[0042] The present invention will be described in detail below in conjunction with specific embodiments of the present invention, but it should be understood that the protection scope of the present invention is not limited by the embodiments.

[0043] Example 1 The fatigue performance of a coupled structural component was tested. The coupled component, an aircraft canopy, features a three-layer PMMA-TPU-PC coupling structure. The PMMA is 12mm thick, the PC is 4mm thick, and the TPU is 4mm thick, all 20mm wide. According to GJB 9438-2018, the elastic modulus of PMMA is 3400MPa, the elastic modulus of PC is 2300MPa, and the elastic modulus of polyurethane is 500MPa. The Poisson's ratio of PMMA is 0.34, the Poisson's ratio of PC is 0.41, and the Poisson's ratio of TPU is 0.48.

[0044] (1) According to GJB 2033-94, the coupling structure is prepared into a coupling structure standard test piece; (2) Spray white matte paint on the front and side of the coupling structure standard test piece and make black speckles to obtain the test piece; (3) Clamp the specimen to be tested on the universal material testing machine, set the load size of the specimen to be tested to 46 MPa, and then use the universal material testing machine to apply a load to the specimen to be tested at a frequency of 0.5 Hz, and apply an axial force of 18.4 kN to the specimen to be tested; During the test, a high-speed camera is used to capture areas with high-contrast points, and images of material surface deformation are collected at a fixed frequency of 50 Hz. The feature points of the test piece are captured in the following way: Figure 3 As shown, based on the digital image correlation technology, the deformation of the speckle pattern at each frequency is compared, the strain distribution cloud map and the stress-strain curve of the working section are drawn, and the axial strain ε of PMMA is obtained. （PMMA）y is 22.652‰, and the axial strain ε of PC （PC）y is 24.845‰, and the axial strain ε of polyurethane （TPU）y It is 23.17‰.

[0045] Therefore, the transverse strain ε of each single layer material is calculated using Equation 1 and Equation 2: x And the cross-sectional area A:

[0046] Therefore, the axial load of each single layer material is calculated using formula 3:

[0047] Conditional fatigue limit testing of coupled structural components According to the aviation materials handbook, the tensile strength of PMMA with the grade YB-9 is 65 MPa. During the fatigue load test, PMMA is the main load-bearing structure, and the selected cross-sectional area is 20 mm × 20 mm. After calculation, the initial load setting value is 15.6 kN, which is increased in increments of 5%. Eight coupling structural members are required to approach the load-bearing value corresponding to the conditional fatigue limit of the coupling structural members.

[0048] When the initial load setting value of the axial load calculated in Example 1 is used, the initial load setting value F0=F 总 -F 设 +F 理 =18.19kN+4.47kN+0.91kN-18.4kN+15.6kN= 20.77kN. By increasing the load by 5%, three coupled structural members are required to test the load value corresponding to the conditional fatigue limit of the coupled structural members.

[0049] Obviously, the method of the present invention can reduce the amount of coupling structural parts used, shorten the number of fatigue load tests on the coupling structural parts, and significantly improve the efficiency of fatigue testing of the coupling structural parts.

[0050] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for quantifying the load on a single layer of material during the movement of a coupled structural component, characterized in that: The method comprises the following steps: (1) Determine the mechanical performance test items and prepare the coupling structure to be tested into standard test pieces corresponding to the mechanical performance test items; (2) forming a speckle pattern on the standard test piece to obtain a test piece; (3) Perform the mechanical property test on the test piece. During the elastic deformation stage of the material during the test, the axial strain ε of the single-layer material is obtained by using the DIC method. y ; (4) Calculate the axial load and / or lateral load of the single layer material according to Equations 1 to 4; ； Among them, ε y is the axial strain of the single-layer material,‰; ε x is the lateral strain of the single-layer material, ‰; ν is the Poisson's ratio of the single-layer material; A is the cross-sectional area of ​​the single-layer material, unit: mm 2 ; d is the width of the single layer material, unit is mm; h is the thickness of the single layer material, unit is mm; E is the elastic modulus of the single layer material, unit is MPa; F x is the lateral load of a single layer of material, in kN; F y It is the axial load of a single layer of material, in kN.

2. The method according to claim 1, wherein The mechanical property test item is selected from one of fatigue test, tensile test, compression test and creep test.

3. The method according to claim 2, wherein The mechanical property test item is a fatigue test, and the coupling structure to be tested is prepared into a standard fatigue test piece with reference to GJB2033-94.

4. The method according to claim 1, wherein Speckle paper is pasted on the front and side of the coupling structure standard test piece to form a speckle pattern, thereby obtaining a test piece to be tested.

5. The method according to claim 1, wherein Matt paint is sprayed on the front and side surfaces of a coupling structure standard test piece and speckles are produced to form a speckle pattern, thereby obtaining a test piece to be tested.

6. The method according to claim 5, wherein: The matte paint is selected from matte white paint or matte black paint.

7. The method according to claim 1, wherein The mechanical property test is carried out on a universal material testing machine.

8. The method according to claim 7, wherein: The mechanical property test item is a fatigue test. The cyclic load of the universal material testing machine is 30-60 MPa, the frequency is 0.5-5 Hz, and the universal material testing machine applies a force of 10-25 kN to the test piece.

9. The method according to claim 1, wherein During the test, a high-speed camera was used to capture areas with high-contrast points, and images of the material surface deformation were collected at a fixed frequency. The deformation of the speckle pattern at each frequency was compared based on digital image correlation technology, and the strain distribution cloud map and stress-strain curve of the working section were drawn to obtain the axial strain ε of each layer of material. y .

10. Application of the method according to any one of claims 1 to 9 in the refined design of coupling structural parts.

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