Material elastic property non-damage mechanical parameter testing method and device

Abstract

The invention relates to a non-destructive testing method and device for elastic parameters of a material. The device uses two beam samples and a rectangular plate sample. Under the condition that the lengths, the widths, the thicknesses and the masses of beam samples and plate samples are known, the elastic parameters (Ex, Ey, vxy and Gxy) or (E, v and G) of a test material are calculated through a quasi-inverse method only by testing the inherent frequencies of the two beam samples in a bending mode and the inherent frequencies of the plate samples in a distortion mode, a saddle mode and a breathing mode. According to the invention, the ASTM-E1876-22 test standard is met, and the low cost of the energy pulse excitation material mechanical parameter test equipment is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of material mechanics, and in particular to a method and device for testing non-damaging mechanical parameters of elastic properties of solid materials. Background Art

[0002] Solid materials can be divided into isotropic, orthotropic, and anisotropic materials based on their mechanical properties. Isotropic materials, such as homogeneous steel, aluminum, polymers, and glass, exhibit identical mechanical properties in all directions. Orthotropic materials, such as bamboo, unidirectional fiber laminates, and metals with highly directional lattices or microstructures, exhibit similar mechanical properties at all points along the same axis, but exhibit significant differences in mechanical properties along the orthogonal axis. Fiber-woven composites are the most widely used type of orthotropic material.

[0003] Assuming that the material test plate forms an XY-plane, the X-axis and the Y-axis are perpendicular to each other, the elastic properties of the isotropic material are independent of the test axis and can be characterized by two independent elastic constants: Young's modulus E and shear modulus G; the elastic properties of the orthotropic material are closely related to the test axis, and its elastic properties in the XY-plane are represented by the elastic modulus E. x , E y , in-plane shear modulus G xy and Poisson's ratio v xy Four independent elastic constants characterize the x and E y They represent the elastic modulus along the X-axis and along the Y-axis, respectively. During testing, different elastic parameters will be obtained for the XY-plane under different orientations, but equivalent transformations can be performed based on the angle between the XY planes.

[0004] Whether it's anisotropic or isotropic materials, their elastic performance parameters are essential for product design, quality control, vibration analysis, load-bearing capacity analysis, and lifespan estimation. The ASTM-E1876-22 test standard regulates the application of pulse excitation testing to material mechanical parameters, but it is more suitable for isotropic materials. Testing methods, such as tensile testing instruments, have significant drawbacks, including a single testing environment, long test cycles, difficulty in testing shear parameters, and significant material limitations.

[0005] To overcome these difficulties, a method for calculating the elastic constants of a material sample using its vibration information has been proposed. Numerous researchers have explored this approach, and their research results have been published in journals. A typical feature of this method is to excite the test sample to free vibration, measure its vibration frequency and corresponding vibration mode, and then calculate the elastic parameters of the material sample using the quasi-inverse method. It is important to emphasize that there is a one-to-one correspondence between the natural frequency and the vibration mode. In elasticity, modal analysis, which calculates the natural frequency and vibration mode of a sample using the material's elastic constants, sample geometry, and sample mass, is a well-established mathematical physics method. However, the inverse operation—the quasi-inverse method—of calculating the material parameters given known material geometry, mass, and vibration frequency is extremely difficult. Once the material sample is determined, its geometry and mass are fixed. In the quasi-inverse method, the material's elastic constants are continuously modified, and the corresponding vibration frequency is calculated using modal analysis methods until a set of mechanical parameters is obtained such that the frequencies obtained from the modal analysis are consistent with those obtained from the actual test. In this case, the elastic parameters used in the calculation model can serve as an approximation of the material's actual mechanical parameters.

[0006] All the testing procedures described in the literature and other patents in this field suffer from serious problems with vibration mode control and the sensitivity of material parameters to vibration frequency. The test panels used in these studies are not optimized in terms of their size ratios, resulting in random vibration modes generated by tapping. However, accurately identifying the vibration modes of a material sample generally requires expensive testing instruments such as laser interferometers that are difficult to integrate with an environmental chamber. This makes the practical implementation of pulse excitation testing methods difficult. Furthermore, in existing research, the sample's higher-order vibration modes and their natural frequencies are used in the quasi-inverse method. However, in practice, the mathematical model used in the quasi-inverse method suffers from significant errors in calculating the natural frequencies of the sample's higher-order vibration modes, which in turn leads to significant uncertainty in the calculated results. Furthermore, the quasi-inverse method requires relatively accurate initial values ​​of the material's elastic parameters, significantly impacting the accuracy of the final results. Test panels with inappropriate size ratios fail to reflect all elastic constants, and arbitrarily selected test panels cannot provide valid data for the quasi-inverse method, ultimately resulting in invalid test results. These factors contribute to the fundamental reasons why this method, despite 20 years of development, has yet to be implemented. Summary of the Invention

[0007] The purpose of the present invention is to overcome the difficulties brought about by the randomness of the vibration mode of the test plate during the tapping test and the inability of the vibration information to reflect all the elastic constants to the quasi-inverse method calculation, and to provide an optimization method for the non-damage mechanical parameter test plate of the elastic properties of solid materials. At the same time, the method combines the beam sample and the optimization of the size, mass and natural frequency of the test plate to test the mechanical parameters of the material.

[0008] In a first aspect, an embodiment of the present invention provides a method for optimizing a test plate for non-destructive testing of elastic properties of solid materials, comprising:

[0009] Step (1) determining the orthogonal symmetry axes X and Y of the test plate according to the material symmetry of the material test plate;

[0010] Step (2) cutting the test plate along the X-axis direction to obtain beam sample No. 1; measuring the length L of beam sample No. 1 x The natural frequency f of the beam sample No. 1 is obtained by a vibration frequency testing device. x ;

[0011] Step (3) cutting the remaining test plate along the Y-axis direction to obtain beam sample No. 2; measuring the length L of the beam sample No. 2 y The natural frequency f of the beam sample No. 2 is obtained by a vibration frequency testing device. y ;

[0012] Step (4) is based on the length L of the beam sample No. 1 x , natural frequency f x and the length L of the beam sample No. 2 y , natural frequency f y , calculate the optimal aspect ratio a:b of the test plate in the X-axis and Y-axis directions required for elastic parameter measurement.

[0013] Furthermore, the optimized ratio a:b of the lengths of the optimized test plate along the X-axis and the Y-axis is calculated in step (4) by the following formula:

[0014]

[0015] Where, a is the length of the final optimized test board along the X-axis, and b is the length of the final optimized test board along the Y-axis; L x is the length of beam sample No. 1, f x is the natural frequency of beam sample No. 1; L y is the length of beam sample No. 2, f y is the natural frequency of beam sample No. 2.

[0016] Furthermore, the natural frequency of the beam sample is obtained by a vibration frequency testing device, including:

[0017] 1) Hang the beam sample individually at a point 19%-25% of the total length of the sample from the first and last ends;

[0018] 2) Install vibration sensors on the suspended beam samples;

[0019] 3) exciting the beam sample to generate free vibration in a manner including but not limited to mechanical knocking, acoustic excitation, contact-type forced vibration, etc.;

[0020] 4) Obtaining the vibration frequency of the beam sample directly or indirectly through the vibration sensor.

[0021] Furthermore, the method further comprises:

[0022] Step (5) cutting the test board along the X-axis and Y-axis directions according to the ratio a:b described in step (4) to obtain an optimized test board;

[0023] Step (6) According to the pseudo-inverse method of the elastic constant of the test material, two or three natural frequencies of the optimized test plate are tested according to the experimental conditions; the three natural frequencies are: the natural frequency f under the torsional mode of the optimized test plate T , optimize the natural frequency f of the test board under breathing mode B And the natural frequency f of the optimized test plate under the saddle mode S ; The two natural frequencies are the above f T , f B With f S Any combination of two of .

[0024] a) the optimized test board is rectangular, and the midpoints of the four adjacent sides of the optimized test board are used as support points to horizontally support the optimized test board;

[0025] b) placing a contact vibration sensor at any corner (maximum amplitude point) of the optimized test plate, or using it as a laser vibration measurement point;

[0026] c) exciting the optimized test plate at any corner of the optimized test plate where no sensor is located by means including but not limited to mechanical knocking, acoustic wave excitation, contact-type forced excitation, etc., so as to generate free vibration;

[0027] d) Testing the natural frequency f of the optimized test plate under the torsional mode T ;

[0028] e) maintaining the positions of the support and vibration sensor or laser measurement point unchanged, and exciting the optimized test plate at the geometric center of the optimized test plate by means including but not limited to mechanical knocking, acoustic excitation, contact-type forced excitation, etc., so that it generates free vibration;

[0029] f) Testing the natural frequency f of the optimized test board under the breathing mode B ;

[0030] g) using the four vertices of the optimized test board as support points to horizontally support the optimized test board;

[0031] h) placing a vibration sensor at the midpoint of any side of the optimized test plate (the point of maximum amplitude), or using it as a laser vibration measurement point;

[0032] i) exciting the optimized test board at the midpoint of any side of the optimized test board where no vibration sensor is located by means including but not limited to mechanical knocking, acoustic wave excitation, contact-type forced excitation, etc., so as to generate free vibration;

[0033] j) Testing the natural frequency f of the optimized test plate under the saddle-type mode S .

[0034] Furthermore, the method further comprises:

[0035] Step (7) uses the quasi-inverse method to calculate the initial value E of the elastic parameter of the optimized test plate x , E y , G xy and v xy .

[0036] In a second aspect, a non-destructive mechanical parameter testing device for elastic properties of a material comprises:

[0037] a base, a sample suspension mechanism or a sample horizontal support mechanism, a vibration excitation device, a vibration sensor, an explicit or implicit signal modulation unit, and a material parameter calculation unit;

[0038] The sample suspension mechanism includes: a suspension frame and a suspension medium; the suspension frame is mounted on the base, or mounted on other supporting structures, and the suspension medium is connected to the material sample through an extension mechanism of the suspension frame, or other suspension mechanisms; or, the sample horizontal support mechanism is mounted on the base, and the material sample is connected to the sample horizontal support mechanism;

[0039] The excitation device is used to generate a pulse excitation source for the material sample to make it vibrate freely;

[0040] The vibration sensor is attached, adsorbed or mounted on the material sample to detect the vibration of the material sample and convert it into an analog signal or a digital signal;

[0041] The signal modulation unit is connected to the vibration sensor in an explicit or implicit manner;

[0042] The computing and processing unit is connected to the signal modulation unit by contact, wired, wireless or other signal exchange methods;

[0043] The signal modulation unit is used to amplify and filter the vibration signal and send it to the material parameter calculation unit in the form of an analog signal or a digital signal;

[0044] The calculation processing unit is used to calculate the length l1 of the beam sample No. 1, the natural frequency f x ; The length l2 and natural frequency f of beam sample No. 2 y Calculate the aspect ratio of the optimized test plate along the X-axis and Y-axis directions; according to the length l1, width w1, thickness h1, mass m1, natural frequency f of beam sample No. 1 x , the length l2, width w2, thickness h2, mass m2, and natural frequency f of beam sample No. 2 y , and the length l3, width w3, thickness h3, mass m3 and natural frequency (f T ,f B ),(f T ,f S ),(f S ,f B ) or (f T ,f S ,f B ) The material elastic parameters (E x ,E y ,v xy ,G xy ) or (E,v,G).

[0045] Furthermore, the suspension medium includes but is not limited to fishing line, nylon line, cotton line, metal line or other material lines; the support mechanism includes but is not limited to cylindrical, conical, and pyramidal support structures made of rigid or flexible materials.

[0046] Furthermore, the vibration sensor includes but is not limited to an accelerometer, a high-precision microphone, and a laser vibration sensor.

[0047] The advantages of the present invention are that the non-damaging mechanical parameter testing method for elastic properties of solid materials proposed by the present invention is:

[0048] 1. By optimizing the aspect ratio of the material test plate along the X-axis and Y-axis, the sensitivity of the material parameters to the vibration frequency is maximized, and the accuracy of the material parameter calculation is maximized.

[0049] 2. When the optimized test board is excited, it can clearly generate distortion, breathing mode and saddle-type vibration mode, and these three modes can clearly correspond to the natural frequencies obtained in the test, completely eliminating the uncertainty of the vibration mode of the ordinary test board.

[0050] 3. It can accurately test the mechanical parameters of isotropic materials and orthotropic materials in a non-contact and non-destructive manner, solving the problem of material mechanical parameter testing.

[0051] 4. No need for modal analysis equipment such as laser interferometers, and can be combined with environmental chambers to enable the widespread application of pulse excitation test methods.

[0052] Therefore, the invention proposes a method for preparing an optimized test plate that can maximize the sensitivity of material parameters to vibration frequency, and proposes technical equipment to implement the method; at the same time, based on the optimized test plate, the invention also proposes a test method based on a beam sample and an optimized test plate vibration test to obtain the mechanical parameters of the material sample, and proposes technical equipment to implement the test method, realizing the low-cost implementation of pulse excitation material mechanical parameter testing equipment, and greatly expanding the application scenarios of pulse excitation material mechanical parameter testing equipment.

[0053] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings.

[0054] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The accompanying drawings are used to provide a further understanding 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 of the present invention. In the accompanying drawings:

[0056] Figure 1 Schematic diagram of the original test plate, beam sample No. 1, beam sample No. 2 and optimized test plate provided in the present invention.

[0057] Figure 2 This is a frequency diagram of the test beam sample of the invention.

[0058] Figure 3 Schematic diagram of the natural frequency of the distortion mode and the natural frequency of the breathing mode of the test board for testing and optimizing the invention.

[0059] Figure 4 Schematic diagram of the saddle-type modal natural frequency of the test board optimized for testing the invention.

[0060] Figure 5 Schematic diagram of the frequency of a horizontally placed beam sample tested for the invention.

[0061] Figure 6 Schematic diagram of the natural frequency of the twisting mode and the natural frequency of the breathing mode of a horizontally placed plate sample tested for the invention.

[0062] Figure 7 Schematic diagram of the saddle-type modal natural frequency of a horizontally placed plate sample tested for the invention.

[0063] Figure 8 Schematic diagram of the breathing mode natural frequency of a horizontally placed plate sample tested for the invention.

[0064] In the figure, 101 is the first beam sample, 102 is the second beam sample, 103 is the optimized test board, 201 is the suspension frame, 202 is the base, 203 is the suspension medium, 204 is the vibration sensor, 205 is the signal modulation unit, 206 is the calculation processing unit, 207 is the first data cable, 208 is the second data cable, and 209 is the sample horizontal support mechanism. DETAILED DESCRIPTION

[0065] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0066] Reference Figures 1 to 8 As shown, the test samples, beam samples and original test plates involved in the embodiments of the present invention are usually from the same plate; beam sample No. 1 is a sample obtained by cutting the initial test plate along the X-axis; beam sample No. 2 is a sample obtained by cutting the initial test plate along the Y-axis; the optimized test plate refers to the remaining test plate or a plate with the same material thickness as the original test plate, which is cut according to the optimized ratio.

[0067] The present invention provides a method for preparing an optimized test plate for non-destructive testing of elastic properties of solid materials, comprising:

[0068] Step (1) determining the orthogonal symmetry axes X and Y of the test plate according to the material symmetry of the material test plate;

[0069] Step (2) cutting the test plate along the X-axis direction to obtain beam sample No. 1; measuring the length L of beam sample No. 1 x The natural frequency f of the beam sample No. 1 is obtained by a vibration frequency testing device. x ;

[0070] Step (3) cutting the remaining test plate along the Y-axis direction to obtain beam sample No. 2; measuring the length L of the beam sample No. 2 y The natural frequency f of the beam sample No. 2 is obtained by a vibration frequency testing device. y ;

[0071] Step (4) is based on the length L of the beam sample No. 1 x , natural frequency f x and the length L of the beam sample No. 2y , natural frequency f y , calculate the optimal aspect ratio a:b of the test plate in the X-axis and Y-axis directions required for elastic parameter measurement.

[0072] Among them, in step (2) and step (3), the natural frequency of the beam sample No. 2 is obtained by the vibration frequency testing device, which can be referred to Figure 2 shown.

[0073] In this embodiment, in order to make the optimized test plate vibrate according to the predetermined vibration mode and its vibration information can reflect all the elastic constants of the test plate, the invention uses the length and natural frequency of beam sample No. 1 and beam sample No. 2 cut from the original test plate to determine the length ratio of the optimized plate along the X-axis and Y-axis. The length and natural frequency of beam sample No. 1 are denoted as L x and f x , the length and natural frequency of beam sample No. 2 are recorded as L y and f y The proportional relationship between the length a of the optimized test board along the X-axis and the length b of the optimized test board along the Y-axis is determined by the following formula:

[0074]

[0075] Where a is the length of the original test board along the X-axis, b is the length of the original test board along the Y-axis; L x is the length of beam sample No. 1, f x is the natural frequency of the first beam sample; L y is the length of beam sample No. 2, F y is the natural frequency of beam sample No. 2.

[0076] In order to calculate the initial value of the elastic constant suitable for the quasi-inverse method, the invention uses the three natural frequencies f of the optimized test plate in the torsional mode, saddle mode and breathing mode. T , f B With f S , it is also possible to use a combination of only two of the frequencies and calculate the elastic parameter E for the quasi-inverse method by empirical formulas or by solving algebraic equations based on virtual field theory. x , E y , G xy With v xy The initial value of . x , f y , L x , and L y As mentioned before, are the natural frequency and length of the beam specimen, respectively.

[0077] The non-destructive testing method of the elastic properties of materials of the present invention:

[0078] 1. By optimizing the aspect ratio of the material test plate along the X-axis and Y-axis, the sensitivity of the material parameters to the vibration frequency is maximized, and the accuracy of the material parameter calculation is maximized.

[0079] 2. When the optimized test board is excited, it can clearly generate distortion, breathing mode and saddle-type vibration mode, and these three modes can clearly correspond to the natural frequencies obtained from the test, completely eliminating the uncertainty of the vibration mode of the ordinary test board.

[0080] 3. It can accurately test the mechanical parameters of isotropic materials and orthotropic materials in a non-contact and non-destructive manner, solving the problem of material mechanical parameter testing.

[0081] 4. No modal analysis equipment such as laser interferometer is required, and it can be combined with an environmental chamber to enable the wide application of the pulse excitation test method. The method provided by the present invention is described below through multiple embodiments:

[0082] Example 1: Optimizing the fabrication of a test board

[0083] Content: Specific operations for determining the aspect ratio of unidirectional carbon fiber reinforced resin-based test plates.

[0084] This embodiment details the specific operation of the invention in determining the optimized size of a unidirectional carbon fiber reinforced resin-based test plate. The test plate is provided by the manufacturer, and the following parameters are provided by the manufacturer: density ρ = 1600 kg / m 3 , thickness t = 0.003m, the test plate fiber extension direction is X axis, and the direction perpendicular to the fiber is Y axis. The four elastic constants are: E x =110GPa, E y =15GPa,v xy =0.20 and G xy =9.01GPa.

[0085] Determine the aspect ratio of the test board:

[0086] 1. The original test plate is a rectangular structure with uniform thickness.

[0087] 2. According to the symmetry of the plate structure, determine its in-plane orthogonal symmetry axes X and Y.

[0088] 3. Cut along the X-axis to obtain the first beam sample 101, and cut along the Y-axis to obtain the second beam sample 102. The lengths of beam samples 101 and 102 can be arbitrarily selected, but the ratio of the length to width of the beam samples must be no less than 5 and no greater than 50. A ratio of 20 is recommended.

[0089] 4. Measure the length L of the first beam sample 101 and the second beam sample 102 x and L yIn this example, the length L of the first beam sample 101 is x = 0.2m, width is 0.02m; length L of the second beam sample 102 y =0.18m, width is 0.02m.

[0090] 5. Measure the natural frequency f of the first beam sample 101 x and the natural frequency f of the first beam sample 102 y , which includes the following sub-steps:

[0091] 5.1 Connect the suspension medium at 1 / 4 of the length of each end point of the first beam sample 101, and press Figure 2 Hang horizontally as shown.

[0092] 5.2 Place a vibration sensor at the geometric center of the first beam sample 101. If it is an accelerometer, adhere it to the geometric center of the beam. If it is a high-precision microphone, place the microphone receiver as close to the geometric center of the first beam sample 101 as possible. If it is a laser vibrometer, focus the laser beam at the geometric center of 101.

[0093] 5.3 The signal modulation box is activated by a programmable device, so that the data acquisition system including the signal modulation box and the data processing module developed by the invention is in a standby state and can process the information from the vibration sensor at any time.

[0094] 5.4 At either end of the beam sample, an excitation device excites the beam sample to cause it to vibrate. The vibration frequency of beam sample No. 1 101 is obtained through the coordinated work of the signal modulation box and the data processing module.

[0095] 5.5 Repeat steps 5.1 to 5.4 to obtain the natural frequency of beam sample No. 2 102.

[0096] In this example, the natural frequency f of the first beam sample 101 is measured x =639.3 Hz, the natural frequency f of the second beam sample 102 y =291.6Hz.

[0097] By the formula:

[0098]

[0099] Calculate the optimized test board aspect ratio. In this example:

[0100]

[0101] Example 2

[0102] Content: Test the natural frequency of the optimized test board cut from the material test board in [Example 1]:

[0103] 1. According to the size ratio determined in [Example 1], cut out the optimized test board 103 from the original test board. In this example, the dimensions of the optimized board 103 are a = 0.3m, b = 0.182m.

[0104] 2. Press the optimized test board Figure 3 As shown, the midpoints of the adjacent sides are connected to the suspension medium for suspension. Of course, the midpoints of the four adjacent sides of the optimized test board can also be used as support points to horizontally support the optimized test board;

[0105] 3. Place a vibration sensor at the bottom corner of the optimized test board. If it's an accelerometer, attach it to the bottom corner of the optimized test board. If it's a high-precision microphone, position the microphone receiver as close to the bottom corner as possible, facing the optimized test board. If it's a laser vibrometer, focus the laser beam at the bottom corner of the optimized test board. The vibration sensor can be placed at any corner of the optimized test board; this embodiment does not limit this.

[0106] 4. The signal modulation box is activated by a programmable device, so that the data acquisition system including the signal modulation box and the data processing module developed by the invention is in a standby state and can process the information from the vibration sensor at any time.

[0107] 5. The test board is excited by the excitation device at any corner of the optimized test board (not the corner where the sensor is placed) to generate free vibration. The natural frequency f of the optimized test board 103 in the torsional mode is obtained through the coordinated work of the signal modulation box and the data processing module. T .

[0108] 6. The test board is excited by the excitation device at the geometric center of the optimized test board to generate free vibration. The natural frequency f of the optimized test board 103 in the breathing mode is obtained through the coordinated work of the signal modulation box and the data processing module. B .

[0109] 7. Press the optimized test board Figure 4 As shown, connect the hanging media at adjacent top corners so that the top edges are horizontal.

[0110] 8. Place the vibration sensor at the midpoint of the bottom edge of the optimized test board.

[0111] 9. The signal modulation box is activated by a programmable device, so that the data acquisition system including the signal modulation box and the data processing module developed by the invention is in a standby state and can process the information from the vibration sensor at any time.

[0112] 10. The test board is excited by the excitation device at the midpoint of any side of the optimized test board (the side not where the vibration sensor is placed) to generate free vibration. The natural frequency f of the optimized test board 103 in the saddle mode is obtained through the coordinated work of the signal modulation box and the data processing module.S .

[0113] In this example, the natural frequency measured is f T =137.9Hz,f S =277.7Hz,f B =292.3Hz.

[0114] [Example 3]

[0115] Content: Determine the initial values ​​of the elastic parameters of the optimized test plate obtained by cutting the material test plate in [Example 1].

[0116] The density ρ of the optimized test plate is calculated based on its length, width, thickness, and mass. In this example, the density ρ and thickness h are provided by the sample manufacturer.

[0117] According to the parameter L measured in Example 1 x , L y , f x , f y , optimize the length, width, thickness, density of the test plate and the natural frequency f measured in [Example 2] T ,f s ,f B Combining the empirical formula with the algebraic equation, the elastic parameter E is obtained x ,E y ,v xy ,G xy Initial value E x =150GPa,E y =13GPa,v xy =0.25,G 12 =9.5GPa.

[0118] [Example 4]

[0119] Content: Test the elastic parameters of the material in [Example 1] and compare with other methods.

[0120] In this example, a detailed comparison is made between the quasi-inverse method proposed by this invention, which combines the natural frequency of the beam sample with the natural frequency of the optimized test plate, and the quasi-inverse method using random test plates in other literature. In other quasi-inverse method tests, in order to construct a sufficient number of equations, the high-order vibration modes of the random test plate and their corresponding natural frequencies are used. In the random test plate case cited in this example, a 0.3m×0.3m square test plate cut from the test plate used in [Example 1] and its five natural frequencies are used. The frequency values ​​and modal shape indices are shown in Table 1:

[0121] Measured natural frequency (Hz) Mode shape index 1 83.6 (1,1) 2 106.0 (0,2) 3 204.0 (1,2) 4 281.7 (2,3) 5 320.0 (2,0)

[0122] Table 1: Natural frequencies and modal shape indices of square test panels

[0123] Based on the estimated elastic constants, the measured frequencies and modal shape indices of the square test plate were used to calculate the material elastic constants using the pseudo-inverse method. The same estimated elastic constants were used in the proposed pseudo-inverse method, which combines a beam specimen with an optimized test plate. Table 2 shows the comparative results:

[0124]

[0125] Table 2: Comparison of test results between the square plate pseudo-inverse method and the pseudo-inverse method proposed in this invention

[0126] The test results of the square plate quasi-inverse method for Poisson's ratio are very poor, with an error of up to 65%. This is because the vibration information of the square test plate cannot reflect the Poisson's ratio. In addition, in the mathematical model used by the quasi-inverse method, all parameters interact with each other, so the incorrect estimation of the Poisson's ratio also affects the estimation accuracy of other parameters. On the contrary, the vibration information of the optimized test plate can reflect all the parameters of the material sample, so the quasi-inverse method gives a result that is completely consistent with the manufacturer's test. In addition, in the quasi-inverse method test proposed in this invention, since the vibration mode of the optimized test plate is known, the operational step of determining the vibration mode shape index is eliminated, which saves a lot of test time and eliminates expensive modal analysis instruments, while enabling the test equipment to be used in a wider range of application scenarios.

[0127] In the second aspect, based on the same inventive concept, the embodiment of the present invention further provides a non-destructive testing device for elastic properties of solid materials, referring to Figure 2-4 As shown:

[0128] The device includes: a base 202, a suspension mechanism, an excitation device (not shown in the figure), a vibration sensor 204, a signal modulation unit 205 and a calculation processing unit 206;

[0129] The suspension mechanism includes a suspension frame 201 and a suspension medium 203; the suspension frame 201 is mounted on a base 202, and the suspension medium 203 is connected to the material sample through an extension mechanism of the suspension frame 201;

[0130] The excitation device is used to generate a pulse excitation source for the material sample to make it vibrate freely;

[0131] The vibration sensor 204 is mounted on the material sample and is used to detect the vibration of the material sample and convert it into an analog signal;

[0132] The signal modulation unit 205 is connected to the vibration sensor 204;

[0133] The calculation processing unit 206 is connected to the signal modulation unit 205;

[0134] The signal modulation unit 205 is used to amplify and filter the analog signal of the vibration sensor, and convert it into a digital signal and send it to the calculation processing unit 206;

[0135] The calculation processing unit 206 is used to calculate the optimized ratio of the material sample, test the natural frequency of the optimized test board after the material sample is cut, and calculate the initial value of the elastic parameter of the optimized test board.

[0136] In this embodiment, the signal modulation unit is a signal modulation box; the computational processing unit is a programmable device, such as a computer or laptop, installed with the program developed by this invention. The excitation device generates a pulse excitation source for the test sample, causing it to vibrate freely; the vibration sensor detects the vibration of the material test plate and converts it into an analog signal; the signal modulation unit amplifies and filters the analog signal from the vibration sensor, converts it into a digital signal, and transmits it to the programmable device; the programmable device contains a computer program for calculating, among other things, the elastic constants of the material.

[0137] The suspension frame 201 is installed on the base 202, providing sufficient space to suspend the material sample; the suspension medium 203 is connected to the material sample through the extension mechanism of the suspension frame 201, so that it is suspended in the air to create conditions for free vibration; the excitation device provides pulse excitation to the suspended material sample (the excitation is a single pulse excitation, which causes the sample to gain energy through mechanical knocking. After that, the stress wave will continue to reflect in the sample and eventually form a steady-state standing wave. Its frequency is called the natural frequency, and its waveform is called the mode. The formation of the standing wave mainly depends on the mutual interference of the stress waves and has little to do with the position of the energy input point), causing it to produce free vibration; the vibration sensor 204 tests the displacement or force of the material sample during the vibration process and converts it into a voltage analog signal, and sends the voltage signal to the signal modulation box via the first data cable 207; the signal modulation box amplifies and filters the received analog signal, converts it into a digital signal, and sends the digital signal to the programmable device connected to it via the second data cable 208. The programmable device processes the received digital signal to obtain the natural frequency of the test sample. Based on the obtained natural frequency, the program developed by the invention calculates the optimal size ratio of the material sample test plate.

[0138] The above-mentioned material elastic property non-destructive test plate optimization device has no specific shape and size requirements for the base 202 and the suspension frame 201, and can be made of local materials according to the sample size and actual conditions;

[0139] The material and size of the suspension medium 203 should be adjusted according to the weight and size of the material sample. The basic principle is that it has sufficient strength to provide sufficient support for the suspended sample and its own influence on the free vibration of the material can be ignored. The suspension medium is generally made of fishing line, nylon line, cotton line, etc.

[0140] Vibration sensor 204 can be an accelerometer, a high-precision microphone, or a laser vibrometer. If the vibration sensor is an accelerometer, the mass of the accelerometer should be less than 5% of the sample mass. If the vibration sensor is a high-precision microphone, the measurement environment must be quiet. If the vibration sensor is a laser vibrometer, the test platform must be vibration-damped.

[0141] The signal modulation box must have signal amplification, filtering and analog-to-digital conversion functions; the programmable device must have sufficient hardware resources and environmental configuration to run the program developed by the invention.

[0142] In this embodiment, in order to overcome the difficulties in using the quasi-inverse method caused by the randomness of the vibration mode of the test plate during the tapping test and the inability of the vibration information to reflect all the elastic constants, the present invention provides a device for optimizing the size of the test plate by using the beam sample vibration test. By testing the vibration frequency of the beam sample, the size ratio of the optimized test plate is calculated. The three lowest natural frequencies f of the optimized test plate are T <f S <f B These correspond to the twisting mode, breathing mode, and saddle mode, respectively. Using these three natural frequencies, or any combination of two of them, the initial values ​​of elastic parameters suitable for the quasi-inverse method can be calculated using empirical formulas combined with algebraic equations. The material parameters can then be further derived using the quasi-inverse method.

[0143] The present invention uses a simple testing device and optimization method to effectively solve the technical barriers of the pulse excitation test method at the application level, and solves the problem of rapid and accurate measurement of elastic mechanical parameters of solid materials.

[0144] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention and are intended to be encompassed by the claims of the present invention.

Claims

1. A method for optimizing a test plate for non-destructive testing of elastic properties of a material, characterized in that: include: Step (1) determining the orthogonal symmetry axes X and Y of the test plate according to the material symmetry of the material test plate; Step (2) cutting the original test plate along the X-axis direction to obtain beam sample No. 1; measuring the length L of the beam sample No. 1 x The natural frequency f of the beam sample No. 1 is obtained by a vibration frequency testing device. x ; Step (3) cutting the remaining test plate along the Y-axis direction to obtain beam sample No. 2; measuring the length L of the beam sample No. 2 y The natural frequency f of the beam sample No. 2 is obtained by a vibration frequency testing device. y ; Step (4) is based on the length L of the beam sample No. 1 x , natural frequency f x and the length L of the beam sample No. 2 y , natural frequency f y , calculate the optimal aspect ratio a:b of the test plate in the X-axis and Y-axis directions required for elastic parameter measurement.

2. The method according to claim 1, wherein In step (4), the optimized ratio a:b of the lengths of the final test plate along the X-axis and the Y-axis is calculated using the following formula: Where, a is the length ratio of the final optimized test board along the X-axis direction, and b is the length ratio of the final optimized test board along the Y-axis direction; L x is the length of beam sample No. 1, f x is the natural frequency of beam sample No. 1; L y is the length of beam sample No. 2, f y is the natural frequency of beam sample No.

2.

3. The method according to claim 1, wherein The natural frequency of the beam sample is obtained by a vibration frequency test device, including: 1) Hang the beam sample individually at a point 19%-25% of the total length of the sample from the first and last ends; 2) Install vibration sensors on the suspended beam samples; 3) exciting the beam sample to generate free vibration; 4) Obtaining the vibration frequency of the beam sample directly or indirectly through the vibration sensor.

4. The method according to claim 1, wherein The method further comprises: Step (5) cutting the test board along the X-axis and Y-axis directions according to the ratio a:b described in step (4) to obtain an optimized test board; Step (6) According to the pseudo-inverse method of the elastic constant of the test material, two or three natural frequencies of the optimized test plate are tested according to the experimental conditions; the three natural frequencies are: the natural frequency f under the torsional mode of the optimized test plate T , optimize the natural frequency f of the test board under breathing mode B And the natural frequency f of the optimized test plate under the saddle mode S ; The two natural frequencies are the above f T , f B With f S Any combination of two of .

5. The method according to claim 4, wherein In the step (6), according to the requirements of the pseudo-inverse method of the elastic constant of the test material, two or three natural frequencies of the optimized test plate are tested, including: a) suspending the optimized test board using the midpoint of the adjacent side or the vibration fixed point of the optimized test board as a suspension point; b) placing a contact vibration sensor at any corner or point of maximum amplitude on the optimized test plate, or using it as a laser vibration measurement point; c) exciting the optimized test plate at any corner of the optimized test plate where no sensor is located, so as to generate free vibration; d) Testing the natural frequency f of the optimized test plate under the torsional mode T ; e) maintaining the suspension and vibration sensor settings unchanged, exciting the optimized test plate at the geometric center of the optimized test plate to generate free vibration; f) Testing the natural frequency f of the optimized test board under the breathing mode B ; g) suspending the optimized test board using two adjacent corners of the optimized test board, i.e., the vibration fixed points, as suspension points; h) placing a vibration sensor at the midpoint or the point of maximum amplitude on any side of the optimized test plate, or using it as a laser vibration measurement point; i) exciting the optimized test board at any midpoint of a side of the optimized test board not provided with a vibration sensor or at a point of maximum amplitude to cause the optimized test board to generate free vibration; j) Testing the natural frequency f of the optimized test plate under the saddle-type mode S .

6. The method according to claim 4, wherein In the step (6), according to the requirements of the pseudo-inverse method of the elastic constant of the test material, two or three natural frequencies of the optimized test plate are tested, including: a) the optimized test board is rectangular, and the midpoints of the four adjacent sides of the optimized test board are used as support points to horizontally support the optimized test board; b) placing a contact vibration sensor at any corner or point of maximum amplitude on the optimized test plate, or using it as a laser vibration measurement point; c) exciting the optimized test plate at any corner of the optimized test plate where no sensor is located, so as to generate free vibration; d) Testing the natural frequency f of the optimized test plate under the torsional mode T ; e) maintaining the positions of the support and the vibration sensor or the laser measurement point unchanged, and exciting the optimized test plate at the geometric center of the optimized test plate to generate free vibration; f) Testing the natural frequency f of the optimized test board under the breathing mode B ; g) using the four vertices of the optimized test board as support points to horizontally support the optimized test board; h) placing a vibration sensor at the midpoint of any side of the optimized test plate or at the point of maximum amplitude, or using it as a laser vibration measurement point; i) exciting the optimized test plate at the midpoint of any side of the optimized test plate where no vibration sensor is located, so as to generate free vibration; j) Testing the natural frequency f of the optimized test plate under the saddle-type mode S .

7. The method according to claim 5 or 6, wherein: The method further comprises: Step (7) uses the quasi-inverse method to calculate the initial value E of the elastic parameter of the optimized test plate x , E y , G xy and v xy .

8. A non-destructive mechanical parameter testing device for material elastic properties, characterized in that: include: A base (202), a sample suspension mechanism or a sample horizontal support mechanism, a vibration excitation device, a vibration sensor (204), an explicit or implicit signal modulation unit (205), and a material parameter calculation unit (206); The sample hanging mechanism comprises: a hanging frame (201) and a hanging medium (203); the hanging frame (201) is mounted on the base (202), and the hanging medium (203) is connected to the material sample via an extension mechanism of the hanging frame (201); or the sample horizontal supporting mechanism is mounted on the base (202), and the material sample is connected to the sample horizontal supporting mechanism; The excitation device is used to generate a pulse excitation source for the material sample to make it vibrate freely; The vibration sensor (204) is mounted on the material sample and is used to detect the vibration of the material sample and convert it into an analog signal; The signal modulation unit (205) is connected to the vibration sensor (204) in an explicit or implicit manner; The computing and processing unit (206) is connected to the signal modulation unit (205) by contact, wired, wireless or other signal communication methods; The signal modulation unit (205) is used to amplify and filter the vibration signal and send it to the material parameter calculation unit (206) in the form of an analog signal or a digital signal; The calculation processing unit (206) is used to calculate the length l1 and the natural frequency f of the beam sample No. 1 according to the x ; The length l2 and natural frequency f of beam sample No. 2 y Calculate the aspect ratio of the optimized test plate along the X-axis and Y-axis directions; according to the length l1, width w1, thickness h1, mass m1, natural frequency f of beam sample No. 1 x , the length l2, width w2, thickness h2, mass m2, and natural frequency f of beam sample No. 2 y , and the length l3, width w3, thickness h3, mass m3 and natural frequency (f T ,f B ),(f T ,f S ),(f S ,f B ) or (f T ,f S ,f B ) The material elastic parameters (E x ,E y ,v xy ,G xy ) or (E,v,G).

9. The device according to claim 1, wherein The suspension medium (203) includes fishing line, nylon line, cotton line, metal line or other material lines.

10. The device according to claim 1, wherein The vibration sensor (204) includes an accelerometer, a high-precision microphone, and a laser vibration sensor.

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