Hyperelastic material strain-related Poisson's ratio measurement method and electronic equipment

Abstract

The invention provides a hyperelastic material strain-related Poisson's ratio measurement method and electronic equipment, and belongs to the field of mechanical property testing of hyperelastic materials. The Poisson's ratio measurement method comprises the following steps: acquiring engineering transverse strain and engineering longitudinal strain in a deformation process of a sample to be measured; converting the engineering transverse strain and the engineering longitudinal strain into transverse true strain and longitudinal true strain; performing function relation fitting based on the transverse true strain and the longitudinal true strain to obtain a fitting function; and obtaining a Poisson's ratio measurement result based on the fitting function. According to the method, errors caused by the large deformation characteristic of the hyperelastic material are reduced, and when the Poisson's ratio of the hyperelastic material is calculated, the real change trend of the Poisson's ratio of the material in the large deformation state can be accurately reflected.

Description

Technical Field

[0001] The present invention belongs to the field of mechanical property testing of superelastic materials, and particularly relates to a method for measuring the strain-dependent Poisson's ratio of superelastic materials and an electronic device. Background Art

[0002] Poisson's ratio is an important parameter characterizing the deformation behavior and acoustic properties of materials, and is usually obtained by measuring the ratio of the transverse deformation to the longitudinal deformation in the linear elastic region of small strains under uniaxial tension or compression conditions of the material. For linear elastic materials, Poisson's ratio is usually a constant value and does not exceed 0.5. However, superelastic materials (such as silicone, biological soft tissues, biomimetic materials, etc.) exhibit strain-dependent Poisson's ratio under large deformation conditions, that is, Poisson's ratio changes with strain and may even exceed 0.5 at specific strains, reflecting their complex deformation mechanisms.

[0003] The existing methods for characterizing Poisson's ratio mainly include the following several types:

[0004] Uniaxial tension experiment: The Poisson's ratio is determined by measuring the ratio of the transverse strain to the longitudinal strain of the material under uniaxial tension conditions. This method is applicable to linear and isotropic materials, but its applicability to viscoelastic materials is limited because their stress-strain curves change with the loading process.

[0005] Creep and relaxation experiments: The deformation (creep) of the material under constant stress and the stress change (relaxation) under constant strain are measured through creep experiments and relaxation experiments respectively. These experiments can provide Poisson's ratio information of the material at different time scales. The creep Poisson's ratio and the relaxation Poisson's ratio are usually not equal, reflecting the complex behavior of viscoelastic materials.

[0006] Digital Image Correlation (DIC) method: The DIC technology is used to measure the transverse and longitudinal strains of the material during the loading process, thereby calculating Poisson's ratio. This method is applicable to measurements under dynamic and static conditions and can avoid the dependence on the loading path in traditional methods.

[0007] The problems of the existing technologies are mainly the following three points:

[0008] Engineering strain is generally used instead of true strain when calculating Poisson's ratio. Engineering strain is calculated based on the initial length of the specimen and cannot accurately reflect the true deformation behavior of the material in the large deformation state;

[0009] During the large deformation process of superelastic materials, both the transverse and longitudinal deformations change non-linearly. Therefore, the calculation of Poisson's ratio needs to consider the instantaneous strain change, and directly using engineering strain for calculation will result in large errors;

[0010] Existing methods are difficult to accurately describe the change in Poisson's ratio of hyperelastic materials in the high-strain region. Using engineering strain calculations may result in non-physical errors, causing the calculation results to deviate from the actual situation.

[0011] In summary, a method for measuring the strain-related Poisson's ratio of hyperelastic materials that can overcome the above defects is urgently needed. Summary of the Invention

[0012] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art, and provide a method for measuring the strain-related Poisson's ratio of hyperelastic materials and an electronic device, effectively solving the problem that the existing Poisson's ratio measurement method produces errors due to large material deformation, and being unable to accurately reflect the true change trend of Poisson's ratio of materials in the large deformation state when calculating the Poisson's ratio of hyperelastic materials.

[0013] The present invention is achieved through the following technical solutions:

[0014] In the first aspect of the present invention, a method for measuring the strain-related Poisson's ratio of hyperelastic materials is provided. The Poisson's ratio measurement method includes:

[0015] Obtain the engineering transverse strain and engineering longitudinal strain during the deformation process of the sample to be measured;

[0016] Convert the engineering transverse strain and the engineering longitudinal strain into transverse true strain and longitudinal true strain;

[0017] Based on the transverse true strain and the longitudinal true strain, perform function relationship fitting to obtain a fitting function;

[0018] Based on the fitting function, obtain the Poisson's ratio measurement result.

[0019] A further improvement of the present invention lies in:

[0020] The method for performing function relationship fitting based on the transverse true strain and the longitudinal true strain includes:

[0021] Using the longitudinal true strain as the independent variable and the transverse true strain as the dependent variable, perform polynomial fitting to obtain a first fitting function.

[0022] A further improvement of the present invention lies in:

[0023] The method for obtaining the Poisson's ratio measurement result based on the fitting function includes:

[0024] By taking the derivative of the first fitting function, obtain the Poisson's ratio of the sample to be measured under instantaneous strain.

[0025] A further improvement of the present invention lies in:

[0026] When performing polynomial fitting, the value range of the order N of the polynomial is: N≥5, and N is a positive integer.

[0027] A further improvement of the present invention lies in:

[0028] Based on the transverse true strain and the longitudinal true strain, the method for fitting the functional relationship includes:

[0029] Along the gradient direction of the longitudinal true strain, strain data within the window are sequentially extracted through a sliding window;

[0030] For the strain data extracted each time, the linear relationship between the transverse true strain and the longitudinal true strain is fitted to obtain a second fitting function.

[0031] A further improvement of the present invention lies in:

[0032] Based on the fitting function, the method for obtaining the Poisson's ratio measurement result includes:

[0033] By taking the derivative of the second fitting function, the Poisson's ratio of the sample to be measured within the sliding window is obtained;

[0034] The Poisson's ratios within each sliding window are used as the Poisson's ratio measurement result of the sample to be measured.

[0035] A further improvement of the present invention lies in:

[0036] The size of the sliding window is determined according to a preset window gradient threshold.

[0037] A further improvement of the present invention lies in:

[0038] The fitting function includes multiple first fitting functions obtained by polynomial fitting of different orders and a second fitting function obtained through a sliding window; then, based on the fitting function, the method for obtaining the Poisson's ratio measurement result includes:

[0039] By taking the derivatives of multiple first fitting functions respectively, multiple initial Poisson's ratio measurement results are obtained, and it is determined whether oscillations occur at the boundaries of the longitudinal true strain for the initial Poisson's ratio measurement results;

[0040] If oscillations occur, the Poisson's ratio within the longitudinal true strain interval where oscillations occur is calculated based on the second fitting function, and the Poisson's ratio within the longitudinal true strain interval where no oscillations occur is calculated based on the first fitting function obtained by polynomial fitting of a preset order.

[0041] A further improvement of the present invention lies in:

[0042] The fitting function includes a plurality of first fitting functions obtained by polynomial fitting of different orders and a second fitting function obtained by a sliding window; then the method for obtaining the Poisson's ratio measurement result based on the fitting function includes:

[0043] Deriving a plurality of initial Poisson's ratio measurement results by respectively differentiating the plurality of first fitting functions;

[0044] Calculating the Poisson's ratio at the boundaries of the entire longitudinal true strain interval based on the second fitting function;

[0045] Based on the Poisson's ratio at the boundary, obtaining the final Poisson's ratio measurement result from the plurality of initial Poisson's ratio measurement results.

[0046] In a second aspect of the present invention, there is provided an electronic device, which includes a memory and a processor. A computer program is stored on the memory and run by the processor. When the computer program is run by the processor, the device equipped with the processor executes the method for measuring the Poisson's ratio related to the strain of the hyperelastic material according to any one of the above first aspects.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows: The method of the present invention has significant improvements in measurement accuracy, stability, and scope of application, reduces the errors caused by the large deformation characteristics of the hyperelastic material, and can accurately reflect the true change trend of the Poisson's ratio of the material in the large deformation state when calculating the Poisson's ratio of the hyperelastic material. Description of the Drawings

[0048] By describing the embodiments of the present invention in more detail in conjunction with the drawings, the above-mentioned and other objects, features, and advantages of the present invention will become more obvious. The drawings are used to provide a further understanding of the embodiments of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention.

[0049] Figure 1 It is a schematic flowchart of the method for measuring the Poisson's ratio related to the strain of the hyperelastic material according to some embodiments of the present invention;

[0050] Figure 2 It is a comparison diagram of the Poisson's ratio of an incompressible material calculated based on engineering strain and true strain during the tensile process;

[0051] Figure 3a It is an example diagram of the DIC measurement process in an embodiment of the present invention;

[0052] Figure 3b It is an example diagram of the measurement results of the transverse engineering strain and the longitudinal engineering strain obtained by DIC measurement in an embodiment of the present invention;

[0053] Figure 4 The Figure 3b locally enlarged view of the data after converting the engineering strain shown in

[0054] Figure 5a into true strain;

[0055] Figure 5b The Figure 5a locally enlarged view of the part indicated by the arrow in

[0056] Figure 6 ;

[0057] Figure 7 The comparison diagram of the 5th-order polynomial fitting curve with the transverse true strain and the longitudinal true strain data in an embodiment of the present invention;

[0058] Figure 8 The example diagram of the boundary oscillation phenomenon of the polynomial fitting derivative method;

[0059] Figure 9 The example diagram of the Poisson's ratio curve calculated by using the adaptive sliding window differential method in another embodiment of the present invention;

[0060] Figure 10 The example diagram of the computer program application interface in an embodiment of the present invention;

[0061] Figure 11 The structural schematic diagram of the electronic device in some embodiments of the present invention. Detailed implementation manners

[0062] In order to make the objectives, technical solutions and advantages of the present invention more apparent, the exemplary embodiments according to the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments of the present invention. It should be understood that the present invention is not limited by the exemplary embodiments described herein. Based on the embodiments of the present invention described herein, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention.

[0063] In view of the problem that the existing Poisson's ratio measurement methods are usually based on engineering strain calculations, and their results may be inaccurate due to the large deformation characteristics of materials, and when calculating the Poisson's ratio of hyperelastic materials, the true change trend of the Poisson's ratio of materials under large deformation conditions cannot be accurately reflected, the present invention proposes a method for measuring the strain-related Poisson's ratio of hyperelastic materials, which is applicable to studying the variation characteristics of the Poisson's ratio of hyperelastic materials under different strain states and can be applied to the fields of mechanics and acoustics simulation of polymer materials, flexible structures, and biomimetic materials. The present invention will be further described in detail below with reference to the accompanying drawings.

[0064] To facilitate the understanding of the present invention, first, a method for measuring the strain-related Poisson's ratio of hyperelastic materials disclosed in the embodiments of the present invention will be introduced in detail. The execution subject of the method for measuring the strain-related Poisson's ratio of hyperelastic materials provided in the embodiments of the present invention is generally a computer device with certain computing capabilities. Such a computer device includes, for example: a terminal device, a server, or other processing devices. The terminal device may be a user equipment (UE), a mobile device, a user terminal, a terminal, etc. In some possible implementation manners, the method for measuring the strain-related Poisson's ratio of hyperelastic materials may be implemented by a processor calling computer-readable instructions stored in a memory.

[0065] The following refers to Figure 1 to describe the method for measuring the strain-related Poisson's ratio of hyperelastic materials in some embodiments of the present invention.

[0066] As Figure 1 shown, the method for measuring the strain-related Poisson's ratio of hyperelastic materials in the present invention includes at least the following steps S110 to S140.

[0067] Step S110, obtain the engineering transverse strain and the engineering longitudinal strain during the deformation process of the sample to be measured.

[0068] Specifically, the engineering transverse strain and the engineering longitudinal strain can be obtained through a DIC device. The DIC device obtains the strain field information by photographing and analyzing the image changes on the surface of the material during the tensile or compressive process, and records the strain field of each point on the surface of the sample in real time, so as to obtain the transverse engineering strain and the longitudinal engineering strain of the material during the tensile or compressive process. In the tensile or compressive experiment, the DIC device is used to track the surface of the hyperelastic material sample to obtain the engineering transverse strain ε trans,eng and the engineering longitudinal strain ε tens,eng during the deformation process of the sample.

[0069] Step S120, convert the engineering transverse strain and the engineering longitudinal strain into transverse true strain and longitudinal true strain.

[0070] Specifically, the engineering lateral strain and the engineering longitudinal strain are converted into the lateral true strain and the longitudinal true strain through the following formula:

[0071] ε true =ln(1 + ε eng )

[0072] where ε true is the true strain and ε eng is the engineering strain.

[0073] For example, substituting the engineering lateral strain ε trans,eng into the above formula, the lateral true strain ε trans,true can be obtained; substituting the engineering longitudinal strain ε tens,eng into the above formula, the longitudinal true strain ε tens,true can be obtained.

[0074] In the traditional method, the Poisson's ratio is usually calculated based on the engineering strain, that is: However, the engineering strain does not consider the cumulative effect of local deformation of the material, which will cause a large error under large deformation of the material. Taking the tensile process of an ideal incompressible (constant volume) material as an example, its theoretical Poisson's ratio should be 0.5 and does not change with strain. Given the known tensile engineering strain in the longitudinal direction, the lateral engineering strain of the material can be calculated based on the principle of constant volume. The Poisson's ratios of the material calculated based on the engineering strain and the true strain are as Figure 2 shown, where the horizontal axis is the tensile strain calculated as a percentage, and the vertical axis is the Poisson's ratio. It can be seen from this that as the strain increases, the Poisson's ratio calculated based on the engineering strain obviously deviates from the theoretical value of 0.5. Therefore, the present invention can significantly improve the calculation accuracy by converting the engineering strain into the true strain, enabling the calculation of the Poisson's ratio to accurately reflect the true behavior of the material under large deformation.

[0075] Step S130: Based on the lateral true strain and the longitudinal true strain, perform a function relationship fitting to obtain a fitting function.

[0076] When performing the function relationship fitting, the function relationship fitting can be performed within the entire data domain, or the true strain data can be segmented for fitting.

[0077] For example, taking ε tens,true as the independent variable and ε trans,true as the dependent variable, perform a polynomial fitting within the entire data domain to obtain the first fitting function:

[0078] ε trans,true =f(ε tens,true )

[0079] Take the derivative of the first fitting function to obtain the Poisson's ratio ν(ε tens,true ) at the instantaneous strain:

[0080]

[0081] By fitting the relationship curve between the transverse true strain and the longitudinal true strain and taking the derivative of the fitted curve to calculate the Poisson's ratio, it is possible to smooth the transverse true strain and longitudinal true strain data and reduce the influence of experimental noise.

[0082] For another example, when fitting the true strain data in segments, the strain data within the window can be sequentially extracted along the gradient direction of the longitudinal true strain through a sliding window; for the strain data extracted each time, the linear relationship between the transverse true strain and the longitudinal true strain is fitted to obtain a second fitting function.

[0083] Here, the size of the sliding window can be a fixed value or a non-fixed value.

[0084] Step S140, based on the fitting function, obtain the measurement result of Poisson's ratio.

[0085] The method for measuring Poisson's ratio based on true strain proposed by the present invention has the following advantages compared with the traditional calculation method based on engineering strain:

[0086] The traditional method calculates Poisson's ratio using the engineering transverse strain and engineering longitudinal strain measured under small strains (below 5%), which cannot accurately reflect the true deformation behavior of hyperelastic materials during large deformation, resulting in distorted calculation of Poisson's ratio. The present invention calculates the instantaneous Poisson's ratio based on true strain, which can more realistically describe the change of Poisson's ratio of materials at each strain stage. Especially when Poisson's ratio is greater than 0.5, it can more accurately describe the trend of material volume change;

[0087] The traditional method is difficult to accurately measure Poisson's ratio under high-speed tensile conditions, while the method of the present invention can be applied to different tensile rates, especially maintaining good calculation stability in high strain rate experiments (such as above 500 mm / min).

[0088] In summary, the method of the present invention has significantly improved in measurement accuracy, stability and application range compared with the traditional method, reducing the error caused by the large deformation characteristics of hyperelastic materials. When calculating the Poisson's ratio of hyperelastic materials, it can accurately reflect the true change trend of Poisson's ratio under large deformation conditions, providing a more accurate calculation method of instantaneous true Poisson's ratio for material testing, numerical simulation and engineering applications.

[0089] In some embodiments of the present invention, the size of the sliding window is determined according to a preset window gradient threshold.

[0090] Specifically, the user can preset the window gradient threshold to determine the detection sensitivity of the strain gradient, so that the system can dynamically adjust the window size according to the local strain gradient. A small window is used in the high-gradient area (mutation area) to retain details, and a large window is used in the low-gradient area (gentle area) to suppress noise.

[0091] Next, two specific embodiments of the present invention are given. The execution subject of both embodiments is the Poisson's ratio measurement system, which has the following functions:

[0092] Data import: Import the engineering strain data in the transverse and longitudinal directions from the DIC device;

[0093] Data preprocessing: Convert the engineering strain into true strain;

[0094] Poisson's ratio calculation: Calculate the Poisson's ratio by the "polynomial fitting and differentiation method" or the "adaptive sliding window differentiation method", and adjust the fitting order or window size during the calculation process;

[0095] Result visualization: Plot the curve of the change of Poisson's ratio with strain and provide the function of numerical export.

[0096] In the following two embodiments, only the calculation process of Poisson's ratio is described in detail. The implementation of data import and data preprocessing can refer to the above relevant descriptions, and the method of result visualization can adopt the existing methods and will not be elaborated.

[0097] In the following two embodiments, when using the DIC device to test a certain hyperelastic material sample, the DIC measurement uses the tensile mode, the tensile rate is 50 mm / min, and the specimen is a 110 mm standard dumbbell-shaped spline. The transverse engineering strain and longitudinal engineering strain during the tensile process are obtained, as Figure 3a and Figure 3b shown.

[0098] After the engineering transverse strain and engineering longitudinal strain are converted, the obtained transverse true strain and longitudinal true strain, Figure 4 shows the local transverse true strain and longitudinal true strain data, where the horizontal axis is the longitudinal true strain calculated as a percentage, the vertical axis is the transverse true strain calculated as a percentage, and the blue circular markers are data points.

[0099] Embodiment 1. Calculate the Poisson's ratio by the polynomial fitting and differentiation method.

[0100] Taking the transverse true strain ε trans,true of the hyperelastic material sample as the independent variable and the longitudinal true strain ε tens,true as the dependent variable, perform polynomial fittings of different orders to obtain the first fitting function: ε trans,true = f(ε tons,true ).

[0101] Taking the fifth-order polynomial fitting as an example, the obtained fitting function is:

[0102] f(x) = p1 * x 5 + p2 * x 4 + p3 * x 3 + p4 * x 2 + p5 * x + p6 * x 0

[0103] where the independent variable x is the longitudinal true strain.

[0104] The comparison between the fitting curve and the data points is as Figure 5a and Figure 5b shown. In the figure, the horizontal axis is the longitudinal true strain calculated as a percentage, and the vertical axis is the transverse true strain calculated as a percentage. Figure 5b is Figure 5a a partial enlarged view of the part indicated by the arrow in Figure 5b where the red circles are the true strain data points, and the green line is the fitting curve. The coefficient of determination R 2 = 1. It can be seen from the figure that the method of this embodiment can smooth the transverse true strain and longitudinal true strain data and reduce the influence of experimental noise.

[0105] The formula parameters of the fifth-order polynomial fitting are as follows (strain is calculated as a percentage %):

[0106] p1 = -0.019135, p2 = 0.007650, p3 = 0.157360, p4 = -0.066974, p5 = -9.301669,

[0107] p6 = -17.147426.

[0108] The root mean square error RMSE = 0.0185, indicating that the fitting effect is very good.

[0109] Taking the derivative of the above fifth-order polynomial fitting function, the fitting formula of the Poisson's ratio under the fifth-order polynomial fitting is obtained. The Poisson's ratio is g(x):

[0110] g(x) = q1 * x 4 + q2 * x 3 + q3 * x 2 + q4 * x + q5 * x 0

[0111] where q1 = 0.095676, q2 = -0.030598, q3 = -0.472081, q4 = 0.133947, q5 = 9.301669.

[0112] Calculating the Poisson's ratio under the 3rd - 8th order polynomial fitting according to this method, as Figure 6As shown, where the horizontal axis is the longitudinal true strain calculated as a percentage and the vertical axis is the Poisson's ratio. The coefficient of determination R during fitting 2 = 1.000. From Figure 6 it can be seen that the Poisson's ratio curve tends to be stable after fitting with a fifth-order polynomial. Therefore, the value range of the order N of the polynomial is N≥5, and N is a positive integer. Preferably, in order to improve the calculation efficiency, the Poisson's ratio calculated under the fitting of a sixth-order polynomial can be taken.

[0113] Figure 7 Fig. shows the comparison chart of the Poisson's ratio calculated based on the true strain and the Poisson's ratio calculated based on the engineering strain in this embodiment, where the horizontal axis is the longitudinal true strain calculated as a percentage and the vertical axis is the Poisson's ratio. The blue circular markers are the data points of the Poisson's ratio calculated based on the true strain, and the orange triangular markers are the data points of the Poisson's ratio calculated based on the engineering strain. As Figure 7 shown, the Poisson's ratio calculated in this embodiment is more in line with the physical phenomenon of the approximate incompressibility of hyperelastic materials.

[0114] Traditional methods are difficult to handle materials with significant non-linear changes in Poisson's ratio, and their Poisson's ratio may change complexly with strain. The polynomial fitting and derivation method proposed in this embodiment can fit the relationship between the transverse true strain and the longitudinal true strain, and derive the fitting curve to obtain the instantaneous Poisson's ratio that changes with strain, which can flexibly adapt to the evolution trend of the Poisson's ratio of different materials; moreover, the polynomial fitting and derivation method has strong noise filtering ability and can provide a smooth Poisson's ratio change trend when there is a certain random fluctuation in the measurement data, especially suitable for data with smooth curves.

[0115] Embodiment 2. Calculating the Poisson's ratio by the adaptive sliding window differentiation method

[0116] Please refer to Figure 8 , where the horizontal axis is the longitudinal true strain calculated as a percentage and the vertical axis is the Poisson's ratio. Figure 8 In the Poisson's ratio calculation result obtained by the polynomial fitting and derivation method shown (the coefficient of determination R during fitting 2 = 1.000), since high-order polynomial fitting is prone to numerical oscillations at the curve boundary (the part within the red rectangular frame in the figure), which may affect the accuracy of Poisson's ratio calculation. In order to overcome the defect of the polynomial fitting method at the boundary, this embodiment proposes an adaptive sliding window differentiation method to calculate the Poisson's ratio in the way of local linear fitting.

[0117] The specific steps are as follows:

[0118] Step 1: Set the sliding window size \(W\) and the adaptive window gradient threshold (user-adjustable, and the user can choose whether to enable the adaptive window function. If it is turned off, it is a fixed window). Divide the data window in the longitudinal true strain direction, and each window contains \(W\) data points. Specifically, the sliding window size \(W\) can be set to 100. Divide the data window in the longitudinal true strain direction, and each window contains 100 data points. Enable the adaptive window function, and the adaptive window gradient threshold is set to 0.1.

[0119] Step 2: In each window, use the least squares method to fit the linear relationship between \(\varepsilon\) trans,true and \(\varepsilon\) tens,true :

[0120] \(\varepsilon\) trans,true \(\approx a\varepsilon\) tens,true \(+ b\)

[0121] where \(a\) and \(b\) are the coefficients obtained by fitting respectively.

[0122] Step 3: Calculate the Poisson's ratio in this window: \(\nu=-a\).

[0123] Step 4: Slide the window to the next data point and repeat the above calculation until all data points are processed.

[0124] This method can avoid the boundary oscillation error caused by high-order polynomial fitting, and the effect is as Figure 9 shown, where the horizontal axis is the longitudinal true strain and the vertical axis is the Poisson's ratio. Since the adaptive window gradient threshold can be set manually, the user can adjust the window size according to the data characteristics, so as to balance noise suppression and boundary stability.

[0125] The adaptive sliding window differential method proposed in this embodiment can not only flexibly adapt to the Poisson's ratio evolution trend of different materials and improve the calculation stability; but also calculate the instantaneous Poisson's ratio of the local area through the sliding window and dynamically adjust the window size according to the data characteristics, which can reduce the oscillation error of the high-order fitting method at the boundary and improve the stability of the boundary data points.

[0126] It should be noted that in order to avoid the boundary oscillation phenomenon and improve the calculation accuracy, the Poisson's ratio can be calculated by the adaptive sliding window differential method and the polynomial fitting derivative method respectively, and the final Poisson's ratio measurement result is determined according to the Poisson's ratio calculated by the adaptive sliding window differential method and the Poisson's ratio calculated by the polynomial fitting derivative method.

[0127] In a specific example, when calculating the Poisson's ratio by the adaptive sliding window differential method and the polynomial fitting derivative method respectively, the following method can be adopted.

[0128] First, the Poisson's ratio at multiple orders is obtained using the polynomial fitting derivative method, and it is determined whether there is an oscillation phenomenon at the boundaries of the longitudinal true strain (near 0 and the maximum value). The specific determination method can be to judge whether the difference between the maximum Poisson's ratio and the minimum Poisson's ratio at the boundary is greater than a preset threshold;

[0129] If the oscillation exceeds the threshold, the adaptive sliding window differential method will be used to calculate the Poisson's ratio within the longitudinal true strain interval of the oscillation.

[0130] In the final Poisson's ratio measurement result, the Poisson's ratio within the longitudinal true strain interval where oscillation occurs is the Poisson's ratio calculated by the adaptive sliding window differential method, and the Poisson's ratio within other longitudinal true strain intervals where no oscillation occurs is the Poisson's ratio calculated by the polynomial fitting derivative method. When calculating using the polynomial fitting derivative method, a 6th-order polynomial can be used.

[0131] In a specific example, when calculating the Poisson's ratio by the adaptive sliding window differential method and the polynomial fitting derivative method respectively, the following method can also be adopted:

[0132] First, the Poisson's ratio at multiple orders is obtained using the polynomial fitting derivative method, and then the Poisson's ratio at the boundary is calculated by the adaptive sliding window differential method (which better restores the test data), and the Poisson's ratio calculated by the polynomial fitting derivative method that is closest to it is selected as the Poisson's ratio measurement result for the entire longitudinal true strain interval.

[0133] By comprehensively adopting multiple calculation methods, users can flexibly select a suitable calculation method according to the characteristics of specific experimental data to achieve a balance between noise suppression and boundary stability and improve the reliability of Poisson's ratio calculation. This method is applicable to the mechanical tests of a wide range of hyperelastic materials and can provide more accurate Poisson's ratio data for material characterization, finite element modeling, engineering applications, etc.

[0134] In summary, the present invention provides a flexible and accurate instantaneous Poisson's ratio measurement method, which calculates the instantaneous Poisson's ratio of a material with strain based on true strain, so as to be able to more accurately and stably characterize the evolution law of the Poisson's ratio of hyperelastic materials under large deformation (strain) conditions, providing an efficient and reliable calculation tool for the research, testing and application of related materials, and meeting the Poisson's ratio measurement requirements of hyperelastic materials under different loading conditions.

[0135] The embodiment of the present application also provides an electronic device, which includes a memory and a processor. A computer program is stored on the memory and run by the processor. When the computer program is run by the processor, the device equipped with the processor executes the Poisson's ratio measurement method related to the strain of hyperelastic materials described in any one of the above embodiments. Figure 10 An example diagram of an application interface of the computer program in the electronic device is shown.

[0136] Next, with reference to Figure 11 FIG. [to be filled] to describe an exemplary electronic device 10 for implementing the method for measuring the Poisson's ratio related to the strain of the superelastic material according to the embodiments of the present invention.

[0137] As Figure 11 shown, the electronic device 10 includes a processor 11, a memory 12, and a communication interface 13. Among them, the processor 11, the memory 12, and the communication interface 13 can be interconnected and communicate through a communication bus 14 and / or other forms of connection mechanisms (not shown).

[0138] It should be noted that Figure 11 the components and structures of the electronic device 10 shown are only exemplary and not restrictive. According to needs, the electronic device may also have other components and structures.

[0139] Optionally, the communication interface 13 may further include a transmitter and / or a receiver.

[0140] The processor 11 may be a microcontroller unit (MCU), a central processing unit (CPU), a digital signal processor (DSP), a single-chip microcomputer, and an embedded device, or other forms of processing units with data processing capabilities and / or instruction execution capabilities.

[0141] The memory 12 may be various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, a random access memory (RAM), a cache, a synchronous dynamic random access memory (SDRAM), etc. The non-volatile memory may include, for example, a read-only memory (ROM), a hard disk, a flash memory, etc. One or more computer program instructions may also be stored on the computer-readable storage media, and the memory 12 may run the program instructions to implement the method for measuring the Poisson's ratio related to the strain of the superelastic material in the embodiments of the present invention described above.

[0142] The embodiments of the present application further provide a storage medium on which a computer program is stored. The computer program runs on a computer, and when the computer program runs, it causes the computer to execute the method for measuring the Poisson's ratio related to the strain of the superelastic material described in any of the above embodiments.

[0143] Finally, it should be noted that the above technical solution is only one implementation manner of the present invention. For those skilled in the art, based on the disclosed application methods and principles of the present invention, it is very easy to make various types of improvements or deformations, not limited to the methods described in the above specific implementation manners of the present invention. Therefore, the manner described above is only preferred and does not have a restrictive meaning.

Claims

1. A method for measuring the strain-dependent Poisson's ratio of a hyperelastic material, characterized in that: The Poisson's ratio measurement method includes: Obtaining the engineering transverse strain and the engineering longitudinal strain during the deformation process of the sample to be measured; Converting the engineering transverse strain and the engineering longitudinal strain into the transverse true strain and the longitudinal true strain; Based on the transverse true strain and the longitudinal true strain, performing function relationship fitting to obtain a fitting function; Based on the fitting function, obtaining the Poisson's ratio measurement result.

2. The method for measuring the strain-related Poisson's ratio of the superelastic material according to claim 1, wherein: The method for performing function relationship fitting based on the transverse true strain and the longitudinal true strain includes: Taking the longitudinal true strain as the independent variable and the transverse true strain as the dependent variable, performing polynomial fitting to obtain a first fitting function.

3. The method for measuring the strain-dependent Poisson's ratio of the superelastic material according to claim 2, characterized in that: The method for obtaining the Poisson's ratio measurement result based on the fitting function includes: By taking the derivative of the first fitting function, obtaining the Poisson's ratio under the instantaneous strain of the sample to be measured.

4. The method for measuring the strain-related Poisson's ratio of the superelastic material according to claim 2, characterized in that: When performing polynomial fitting, the value range of the order N of the polynomial is: N≥5, and N is a positive integer.

5. The method for measuring the strain-related Poisson's ratio of the superelastic material according to claim 1, characterized in that: The method for performing function relationship fitting based on the transverse true strain and the longitudinal true strain includes: Along the gradient direction of the longitudinal true strain, sequentially extracting the strain data within the window through a sliding window; For the strain data extracted each time, fitting the linear relationship between the transverse true strain and the longitudinal true strain to obtain a second fitting function.

6. The method for measuring the strain-related Poisson's ratio of the superelastic material according to claim 5, characterized in that: The method for obtaining the Poisson's ratio measurement result based on the fitting function includes: By taking the derivative of the second fitting function, obtaining the Poisson's ratio of the sample to be measured within the sliding window; Taking the Poisson's ratios within each sliding window as the Poisson's ratio measurement result of the sample to be measured.

7. The method for measuring the strain-related Poisson's ratio of the superelastic material according to claim 5, wherein: The size of the sliding window is determined according to a preset window gradient threshold.

8. The method for measuring the strain-related Poisson's ratio of the superelastic material according to claim 1, wherein: The fitting function includes multiple first fitting functions obtained by polynomial fitting of different orders and a second fitting function obtained through a sliding window; then the method for obtaining the Poisson's ratio measurement result based on the fitting function includes: By taking the derivatives of multiple first fitting functions respectively, obtaining multiple initial Poisson's ratio measurement results, and judging whether the initial Poisson's ratio measurement results oscillate at the boundary of the longitudinal true strain; If oscillation occurs, calculating the Poisson's ratio within the longitudinal true strain interval where oscillation occurs based on the second fitting function, and calculating the Poisson's ratio within the longitudinal true strain interval where no oscillation occurs based on the first fitting function obtained by polynomial fitting of a preset order.

9. The method for measuring the Poisson's ratio related to the strain of the superelastic material according to claim 1, wherein: The fitting function includes multiple first fitting functions obtained by polynomial fitting of different orders and a second fitting function obtained through a sliding window; then the method for obtaining the Poisson's ratio measurement result based on the fitting function includes: By taking the derivatives of multiple first fitting functions respectively, obtaining multiple initial Poisson's ratio measurement results; Calculating the Poisson's ratio at the boundary of the entire longitudinal true strain interval based on the second fitting function; Based on the Poisson's ratio at the boundary, obtaining the final Poisson's ratio measurement result from multiple initial Poisson's ratio measurement results.

10. An electronic device, characterized in that, The electronic device includes a memory and a processor, and a computer program run by the processor is stored on the memory. When the computer program is run by the processor, the device equipped with the processor executes the Poisson's ratio measurement method related to the strain of the hyperelastic material as described in any one of claims 1-9.

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