Device and method for measuring elastic modulus of flexible material based on beat-wave longitudinal wave coupling

Abstract

The application discloses a kind of based on beat-longitudinal wave coupling's flexible material elastic modulus measuring device and method, belong to flexible material measurement technical field, the device includes signal generation module, signal acquisition and processing module and measurement auxiliary module;The signal generation module is used to synchronously output two-way frequency close sine wave signal excitation flexible material string vibration, and the string vibration after tuning is converted into front and rear displacement mechanical vibration;The signal acquisition and processing module is used to analyze the displacement information of sine wave signal and mechanical vibration, obtains analysis result, and obtains the elastic modulus of flexible material according to analysis result, the length and mass density of flexible material;The measurement auxiliary module is used to measure the length and mass density of flexible material.The application solves the technical problems that flexible material elastic modulus measurement result sensor precision requirement is high, measurement cannot be visualized.

Description

Technical Field

[0001] This invention belongs to the field of flexible material measurement technology, and particularly relates to a device and method for measuring the elastic modulus of flexible materials based on beat-longitudinal wave coupling. Background Technology

[0002] Elastic modulus, as a core parameter of material mechanical properties, directly determines its deformation response and durability under stress. For flexible materials, due to their low stiffness and high elasticity, they have irreplaceable application value in fields such as medical stents, flexible electronics, and smart fabrics. When predicting the performance of products made from flexible materials, it is usually necessary to measure the elastic modulus of the flexible material. For example, Nylon-66 (polyhexamethylene adipamide) is a polymer material widely used in automotive airbags and outdoor equipment; the dynamic measurement results of its elastic modulus will directly affect the accuracy of predicting the product's impact resistance performance.

[0003] The technology lags far behind the needs of industrial development, and it faces two main dilemmas: Currently, the measurement of the elastic modulus of flexible materials mainly relies on the static tensile method (GB / T 1040 Plastics Tensile Standard), which obtains the stress-strain curve through uniaxial quasi-static loading and then calculates the elastic modulus. Although this method is simple to operate, it has fundamental drawbacks: flexible materials exhibit significant viscoelastic behavior under dynamic loads, and their modulus can change by more than 20% with frequency; static measurement results cannot reflect the material properties under actual working conditions, leading to redundancy in product design or the risk of failure.

[0004] Traditional dynamic methods attempt to infer the elastic modulus from the propagation velocity of transverse waves. However, flexible materials have extremely low shear stiffness, and the energy decay rate of transverse waves increases exponentially during propagation. Taking nylon fibers as an example, when the frequency exceeds 100 Hz, the transverse wave decays to 5% of its initial amplitude in less than 10 cm of propagation distance. This forces the detection to rely on highly sensitive laser interferometers or piezoelectric sensors, which are expensive, typically exceeding 100,000 yuan per unit, resulting in excessively high costs for measuring the elastic modulus of flexible materials.

[0005] Furthermore, in current university physics experiments, the measurement of elastic modulus has long been plagued by a dilemma: on the one hand, fundamental experiments (such as Young's modulus measurement) still employ the century-old optical lever method, which is only applicable to rigid materials such as metal wires and completely ignores dynamic effects; on the other hand, some university students can only input sample parameters and read the final modulus value, without being able to intervene in the physical processes of wave excitation, propagation, and reception. This design leads to the following problems in teaching experiments: The parameters for measuring the elastic modulus are not adjustable, making it impossible for students to explore the effects of string density and tension on wave velocity, or to verify the frequency dependence of the elastic modulus, thus making the string vibration equation extremely abstract in teaching.

[0006] During the measurement of elastic modulus, the attenuation and scattering of transverse waves in flexible media cannot be directly observed. Only a rough method of "visually estimating the position of wave nodes" can be used, which introduces human error.

[0007] While scientific research has attempted to overcome these limitations and various measurement methods have emerged, such as laser Doppler vibration measurement to infer modulus from surface vibrations through non-contact measurement, this method requires high reflectivity treatment of the sample surface and is sensitive to the micro-bending of flexible materials, with an error exceeding 15%. Atomic force microscopy (AFM) nanoindentation can measure micro-region modulus, but the results depend on tip model correction and cannot reflect the macroscopic properties of the material.

[0008] These methods are either too costly to be widely adopted or too complex to be applied in teaching, forcing the academic community to re-examine the potential for innovation in basic physics principles. Therefore, how to achieve a balance between the accuracy of the measurement results of the elastic modulus of flexible materials and the precision requirements of the sensors, and how to visualize the measurement of the elastic modulus of flexible materials, has become an urgent technical problem to be solved. Summary of the Invention

[0009] To address the aforementioned shortcomings in the existing technology, this invention provides a device and method for measuring the elastic modulus of flexible materials based on beat-longitudinal wave coupling, which solves the technical problems of high sensor accuracy requirements and the inability to visualize the elastic modulus measurement phenomenon of flexible materials.

[0010] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: A device for measuring the elastic modulus of flexible materials based on beat-longitudinal wave coupling includes a signal generation module, a signal acquisition and processing module, and a measurement auxiliary module. The signal generation module is used to synchronously output two sinusoidal signals with similar frequencies to excite the vibration of the flexible material string, and to convert the tuned string vibration into mechanical vibration with forward and backward displacement. The signal acquisition and processing module is used to analyze the displacement information of sinusoidal signals and mechanical vibrations, obtain the analysis results, and obtain the elastic modulus of the flexible material based on the analysis results, the length and mass density of the flexible material. The measurement auxiliary module is used to measure the length and mass density of flexible materials.

[0011] The beneficial effects of this invention are as follows: It adopts a modular and detachable design, allowing for independent adjustment of parameters such as string length and beat frequency during measurement. This facilitates real-time observation of the entire process of longitudinal wave interference generating the envelope signal via LabVIEW, providing an intuitive understanding of the physical relationship between wave modulation and elastic modulus. It also solves the "black box" problem of teaching experimental instruments, making it easier to observe experimental phenomena during teaching experiments. Furthermore, it can be upgraded to achieve automated measurement, adapting to teaching experiments and industrial quality inspection scenarios. This meets the needs of industries such as textiles, packaging, and biomaterials for rapid testing of the mechanical properties of flexible materials, and promotes the standardization of mechanical characterization methods for flexible materials.

[0012] Furthermore, the signal generation module includes a signal generator, several speaker plates, and a vibrating plate; The signal generator is used to synchronously output two sinusoidal signals with similar frequencies; Each of the aforementioned horn plates is used to convert a sinusoidal wave signal into a longitudinal wave signal to excite the flexible material to generate string vibration; The vibrating plate is used to convert the tuned string vibration into mechanical vibration with forward and backward displacement. The frequency difference between the two sinusoidal signals is 0.1Hz to 1Hz.

[0013] The beneficial effects of the above-mentioned further scheme are: setting the frequency difference between the two transmitters to 0.1Hz~1Hz makes the experimental phenomena during the measurement process, namely wave packet propagation and beat phenomenon, most obvious, which facilitates the observation and acquisition of measurement data.

[0014] Furthermore, at least two horn plates are provided, which serve as excitation sources and are respectively connected to two channels of the signal generator; at least one vibrating plate is provided, which serves as the end of the converter connected to the flexible material; the angle of the normal direction of each horn plate is between 90° and 150°.

[0015] The beneficial effects of the above-mentioned further scheme are: ensuring that the positions of the two transmitters are relatively fixed, which facilitates the installation of the equipment during measurement, while minimizing the mutual influence between the two sets of signals when the two transmitters emit signals, thus ensuring the accuracy of the experimental results.

[0016] Furthermore, the signal acquisition and processing module includes a data acquisition card, graphical programming software, a laser rangefinder, and sensor analysis software; The data acquisition card is used to acquire sine wave signals; The graphical programming software is used to perform image processing based on each sine wave signal to obtain the phase difference; The laser rangefinder is used to capture displacement information of the mechanical vibration of the vibrating plate in real time. The sensor analysis software is used to analyze displacement information and phase difference, obtain analysis results, and obtain the elastic modulus of the flexible material based on the analysis results, the length and mass density of the flexible material.

[0017] The beneficial effects of the above-mentioned further solutions are as follows: by capturing vibration displacement in real time through sensors, the sensor analysis software automatically extracts key parameters such as envelope time, and the graphical programming software synchronously displays the signal waveform, the measurement process is visualized and the data is processed automatically, reducing manual errors and ensuring the accuracy of the detection process data.

[0018] This invention provides a method for measuring the elastic modulus of flexible materials, comprising the following steps: S1. Use the measurement auxiliary module to collect the physical parameter information of the flexible material test piece, and detect the vibration displacement data of the flexible material test piece with different chord lengths under the beat sine wave signal; S2. Based on the physical parameter information and vibration displacement data collected in step S1, calculate the phase difference between the two ends of flexible material test pieces with different chord lengths, and integrate the phase differences of flexible material test pieces with different chord lengths to form a dependent variable dataset. S3. Perform linear fitting on the data in the dependent variable dataset to obtain the chord length-phase difference fitting slope; S4. Calculate the elastic modulus of the flexible material specimen based on the chord length-phase difference fitting slope and the physical parameter information of the flexible material specimen.

[0019] The beneficial effects of this invention are as follows: This solution overcomes the limitations of the traditional static tensile method when detecting the elastic modulus of flexible materials. It accurately reflects the viscoelastic behavior of flexible materials under dynamic loads, and the measurement results are more consistent with actual working conditions. The relative error can be controlled below 1.5%, and the measurement results are all within the range of the true value 2σ. Furthermore, utilizing the characteristic that the attenuation coefficient of longitudinal waves in flexible materials is only 1 / 8 that of transverse waves, and combining the beat principle, high-frequency vibrations are converted into low-frequency envelope signals. General-purpose equipment such as laser rangefinders are used to replace high-cost dedicated sensors, reducing the cost of a single measurement to the thousand-yuan level, significantly lowering the cost of measuring the elastic modulus of flexible materials.

[0020] Further, in step S1, the vibration displacement data of the flexible material test piece with different chord lengths under the beat sinusoidal wave signal are detected, specifically including: A1. Connect the two ends of the flexible material test piece to the signal generator and the vibrating plate respectively. The signal generator emits a beat sine wave signal to the flexible material test piece, and the flexible material test piece drives the vibrating plate to vibrate. A2. Collect vibration displacement data during the vibration process of the vibrating plate using a laser rangefinder; A3. Determine whether the number of tests has reached the preset value. If yes, exit the test; otherwise, adjust the chord length of the flexible material test piece and return to step A1.

[0021] The beneficial effects of the above-mentioned further solution are as follows: by detecting the vibration displacement data at different length positions of the flexible material, the result deviation caused by detection error can be reduced when analyzing and calculating the elastic modulus of the flexible material using beat longitudinal wave signals, thus ensuring the accuracy of the elastic modulus calculation results.

[0022] Furthermore, in step S2, the calculation of the phase difference includes the following steps: B1. Based on the vibration displacement data of the current chord length of the flexible material test piece, record the signal waveform using sensor processing software; B2. Obtain the wave packet start point based on the signal waveform. To the node intercept point time interval ; B3. According to time interval Calculate the phase information of the receiver end at the current chord length of the flexible material specimen:

[0023] In the formula, For the transmitting phase, Pi This is the theoretical value of the wave packet period. To analyze the actual period of the beat waveform, The frequency difference of the beat longitudinal wave signal; B4. Calculate the phase information of the current chord length output terminal of the flexible material specimen:

[0024] In the formula, For the output phase, The instantaneous phase of the first channel of the signal generator (6), The instantaneous phase of the second channel of the signal generator (6), The instantaneous voltage of the first channel of the signal generator (6) The peak voltage of the first channel of the signal generator (6) The instantaneous voltage of the second channel of the signal generator (6), The peak voltage of the second channel of the signal generator (6); B5. Calculate the phase difference of the current chord length of the flexible material specimen based on the phase information from the receiving end and the output end:

[0025] In the formula, The phase difference between the output and receiving ends of the flexible material test specimen.

[0026] The beneficial effect of the above-mentioned further scheme is that it transforms the problem of analyzing the phase measurement of wavelet packets with small time and spatial periods into the measurement of the phase of beat wave packets with larger wavelengths or larger time or spatial periods.

[0027] Further, in step S3, the formula for calculating the chord length-phase difference fitting slope is:

[0028] In the formula, The slope of the chord length-phase difference fitting is... Pi For the frequency difference of the beat longitudinal wave signal, The group velocity is the velocity of a wave propagating in a string.

[0029] The beneficial effect of the above-mentioned further scheme is that it transforms the difficult-to-observe P-wave number into a measurable physical quantity, performs least squares linear regression to fit a straight line, and reduces the unobservability.

[0030] Further, in step S4, the formula for calculating the elastic modulus of the flexible material specimen is:

[0031] In the formula, The elastic modulus of the flexible material specimen. Pi For the frequency difference of the beat longitudinal wave signal, The slope of the chord length-phase difference fitting is... For the diameter of the flexible material test piece, For the quality of flexible material test specimens, The length of the flexible material test specimen.

[0032] The beneficial effect of the above-mentioned further scheme is that it indirectly obtains the expression for the elastic modulus, which is difficult to measure, through physical quantities such as slope and frequency difference. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the flexible material elastic modulus measurement device based on beat-longitudinal wave coupling in an embodiment of the present invention. Figure 2 This is a flowchart of the method for measuring the elastic modulus of flexible materials in an embodiment of the present invention; Figure 3 This is a schematic diagram of the linear fitting result of phase difference and chord length in an embodiment of the present invention.

[0034] The components include: 1. Laser rangefinder; 2. Vibrating plate; 3. Flexible material; 4. Horn plate; 5. Data acquisition card; 6. Signal generator. Detailed Implementation

[0035] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0036] Example 1 This invention also aims to provide a device for measuring the elastic modulus of flexible materials based on beat-longitudinal wave coupling, as shown in the attached figure. Figure 1 As shown, it includes a signal generation module, a signal acquisition and processing module, and a measurement auxiliary module; The signal generation module is used to synchronously output two sinusoidal signals with similar frequencies to excite the vibration of the flexible material 3 string, and to convert the tuned string vibration into mechanical vibration with front and rear displacement. The signal acquisition and processing module is used to analyze the displacement information of the sinusoidal signal and mechanical vibration, obtain the analysis results, and obtain the elastic modulus of the flexible material 3 based on the analysis results, the length and mass density of the flexible material 3. The measurement auxiliary module is used to measure the length and mass density of the flexible material 3.

[0037] The measurement auxiliary module includes an electronic balance and a measuring tape. The minimum range of the electronic balance is 0.1g, and the minimum range of the measuring tape is 1mm. It is used to accurately measure the mass and length of the flexible material 3.

[0038] The flexible material 3 is a soft material with low elastic modulus, such as nylon string with a diameter of 0.1-1mm.

[0039] The signal generation module includes a signal generator 6, several speaker plates 4, and vibrating plates 2; The signal generator 6 is used to synchronously output two sinusoidal signals with similar frequencies; Each of the aforementioned horn plates 4 is used to convert a sinusoidal wave signal into a longitudinal wave signal to excite the flexible material 3 to generate string vibration; The vibrating plate 2 is used to convert the tuned string vibration into mechanical vibration with forward and backward displacement. The frequency difference between the two sinusoidal signals is 0.1Hz to 1Hz.

[0040] When the frequency difference between the two sinusoidal signals output by the signal generator 6 is 0.5 Hz, the theoretical value of the beat period is 2 s. The phase of the receiving end is calculated by measuring the envelope time (the selected frequency difference of 0.5 Hz is based on the experimental phenomenon that the beat phenomenon is most obvious during wave packet propagation, and the frequency difference can be adjusted between 0.1 Hz and 1 Hz. During the experiment, it was observed that the beat wave packet was most obvious when the frequency difference was 0.5 Hz).

[0041] In this embodiment, the signal generation module includes a signal generator 6, a horn plate 4, and a vibrating plate 2. The signal generator 6 is used to synchronously output two sinusoidal signals with similar frequencies. The horn plate 4 converts the sinusoidal signal into a longitudinal wave signal to excite the flexible material 3 to generate forced vibration. The vibrating plate 2 converts the tuned string vibration into a mechanical vibration signal with front and rear displacement. At least two horn plates 4 are provided, which are respectively connected to the two channels of the signal generator 6 as excitation sources; at least one vibrating plate 2 is provided, which is connected to the end of the flexible material 3 as a converter; the angle between the normal of each horn plate 4 and the surface is 90°-150°.

[0042] In the signal generation and excitation module, the frequency difference between the two sinusoidal signals is adjustable. The frequency modulation characteristics are generated through the beat phenomenon, forming an easily detectable low-frequency envelope signal, which significantly reduces the requirements for sensor accuracy.

[0043] The signal acquisition and processing module includes a data acquisition card 5, graphical programming software, a laser rangefinder 1, and sensor analysis software; The data acquisition card 5 is used to acquire sine wave signals; The graphical programming software is used to perform image processing based on each sine wave signal to obtain the phase difference; The laser rangefinder 1 is used to capture the displacement information of the mechanical vibration of the vibrating plate 2 in real time. The sensor analysis software is used to analyze displacement information and phase difference to obtain analysis results, and based on the analysis results, the length and mass density of the flexible material 3, the elastic modulus of the flexible material 3 is obtained.

[0044] The laser rangefinder 1 has a measurement accuracy of no less than 0.0001 mm and is used to capture the vibration displacement of the flexible material 3 in real time and transmit it to the sensor analysis software. The sensor analysis software can process the vibration displacement data collected by the laser rangefinder 1 and extract key parameters such as envelope time and phase difference. In the signal acquisition and processing module, the laser rangefinder 1 captures the vibration displacement of the string in real time, the sensor analysis software sensortool automatically extracts key parameters such as envelope time, and LabVIEW synchronously displays the signal waveform, realizing visualization of the measurement process and automated data processing.

[0045] In this embodiment, the signal acquisition and processing module includes a data acquisition card 5, LabVIEW, a laser rangefinder 1, and sensor analysis software. The signal output from the signal generator 6 is input into the LabVIEW software through the data acquisition card 5. The phase difference is obtained by using LabVIEW image processing. The laser rangefinder 1 captures the vibration displacement of the vibrating plate 2 in real time. The sensor analysis software processes the data acquired by the laser rangefinder 1 and extracts key parameters such as envelope time. The measurement auxiliary module is used to accurately measure the length and mass density of the flexible material 3.

[0046] Compared with existing technologies, this solution breaks through the limitations of the traditional static tensile method when testing the elastic modulus of flexible material 3. It can accurately reflect the viscoelastic behavior of flexible material 3 under dynamic load, and the measurement results are more consistent with the actual working conditions. The relative error can be controlled below 1.5%, and the measurement results are all within the range of the true value 2σ.

[0047] Furthermore, by utilizing the characteristic that the attenuation coefficient of longitudinal waves in flexible material 3 is only 1 / 8 that of transverse waves, and combining the beat principle, high-frequency vibrations are converted into low-frequency envelope signals. General-purpose equipment such as laser rangefinders 1 are used to replace high-cost dedicated sensors, reducing the cost of a single measurement to the thousand-yuan level, and significantly reducing the cost of measuring the elastic modulus of flexible material 3.

[0048] Adopting a modular and detachable design, it allows for independent adjustment of parameters such as string length and beat frequency. The entire process of generating envelope signals through longitudinal wave interference can be observed in real time via LabVIEW, providing an intuitive understanding of the physical relationship between wave modulation and elastic modulus. This solves the problem of "black box" teaching experimental instruments and facilitates the observation of experimental phenomena during teaching experiments.

[0049] The laser rangefinder captures vibration displacement in real time, and the sensor analysis software automatically extracts key parameters such as envelope time. LabVIEW synchronously displays the signal waveform, realizing visualization of the measurement process and automated data processing, reducing manual errors and ensuring the accuracy of the detection data.

[0050] It can be upgraded to achieve automated measurement, adapt to teaching experiments and industrial quality inspection scenarios, meet the needs of industries such as textiles, packaging, and biomaterials for rapid testing of the mechanical properties of flexible materials, and promote the standardization process of mechanical characterization methods for flexible materials.

[0051] In this embodiment, the preparation work for using the device is as follows: (1) Connect the two channels of the signal generator 6 to the two horn plates 4 respectively. In this embodiment, the two horn plates 4 are the first horn plate A and the second horn plate B, to ensure the stability and accuracy of signal transmission. Fix the string on a precision optical platform. One end is coupled to the two horn plates 4 through a permanent magnet lead, and the other end is connected to the vibrating plate 2 through a permanent magnet, to ensure that the string maintains stable tension during vibration. The first output port CH1 of the signal generator 6 is connected to the first horn plate A as the first excitation source. The second output port CH2 of the signal generator 6 is connected to the second horn plate B as the second excitation source. (Fix the two horn plates 4 on the same fixing device, making the angle between the normals of the two horn plates 4 as large as possible, about 120 degrees (experiments have verified that the angle can be adjusted between 90° and 150° with little impact on the experimental work). This design can minimize the mutual interference between the two horn plates 4 on the same fixing device. This design is based on specific experience accumulated through multiple experiments. The relative angle of the two horn plates 4 is prone to mutual interference. If two fixing devices are used to fix the horn plates 4 separately and then placed side by side and pressed together, the two horn plates 4 will also interfere with each other.) (2) Install a sensor (laser rangefinder 1) module at the receiving end and connect it to the data acquisition system to ensure that the vibration displacement signal of the vibrating plate 2 can be acquired and recorded in real time. (3) Use LabVIEW software on the computer to monitor the two input signals simultaneously to ensure the stability and consistency of the signals during the experiment; (4) Use sensorTool software to monitor the signal collected by the end vibrating plate 2, and provide detailed signal characteristic parameters and analysis results (all are the use of conventional functions, and the data analysis is processed on Origin using some advanced analysis functions). (5) Accurately measure the length and mass of the flexible material 3, and calculate its density; (6) Signal excitation and acquisition: The signal generator 6 is started to output two sinusoidal signals, which are converted into longitudinal waves by the horn plate 4 to excite the vibration of the flexible material 3. At the same time, the signal image is recorded by LabVIEW and sensortool, and the vibration displacement data is captured by the laser rangefinder 1. (7) Data processing: The phase difference is obtained by using LabVIEW image processing, and parameters such as envelope time are extracted by sensor analysis software; (8) Calculation of elastic modulus: The elastic modulus is derived by combining the length, mass density and processed parameters of flexible material 3.

[0052] Example 2 like Figure 2 As shown, in one embodiment of the present invention, a method for measuring the elastic modulus of a flexible material includes the following steps: S1. The physical parameter information of the flexible material test specimen is collected using the measurement auxiliary module, and the vibration displacement data of the flexible material test specimen with different chord lengths under the beat sine wave signal are detected. The physical parameter information of the flexible material test specimen includes the length, mass, diameter and density information of the flexible material test specimen. The specific method for collecting the physical parameter information of the flexible material test specimen is existing technology and will not be described in detail here.

[0053] When detecting the vibration displacement data of flexible material test specimens at different chord lengths and positions under beat longitudinal wave signals, one end of the flexible material test specimen is connected to the signal generator 6, and the other end is connected to the vibrating plate 2. During detection, the signal transmitter sends two sets of beat longitudinal wave signals to the flexible material test specimen, which are transmitted through the flexible material test specimen to the vibrating plate 2, causing the vibrating plate 2 to vibrate. The vibration of the vibrating plate 2 is detected by the sensor, and the vibration data of the vibrating plate 2 is analyzed by the detection software. The specific steps include: A1. Connect the two ends of the flexible material test piece to the signal generator 6 and the vibrating plate 2 respectively. The signal generator 6 transmits a beat sine wave signal to the flexible material test piece, and the flexible material test piece drives the vibrating plate 2 to vibrate. The initial frequency, amplitude and other parameters of the signal generator 6 are set, and the set parameters of the signal generator 6 are used to drive the vibrating plate 2 to vibrate through the flexible material test piece; wherein the flexible material test piece is a flexible linear material; A2. Collect vibration displacement data of the vibrating plate 2 during the vibration process using laser rangefinder 1; A3. Determine whether the number of tests has reached the preset value. If yes, exit the test; otherwise, adjust the chord length of the flexible material test piece and return to step A1.

[0054] Specifically, when adjusting the measurement chord length of the flexible material test specimen, select 5-6 equidistant measurement points according to the length of the flexible material test specimen, and detect the vibration displacement data of different flexible material test specimen chord lengths under beat longitudinal wave signals.

[0055] S2. Based on the physical parameter information and vibration displacement data collected in step S1, calculate the phase difference between the two ends of flexible material test specimens with different chord lengths, and integrate the phase differences of flexible material test specimens with different chord lengths to form a dependent variable dataset; wherein the calculation of the phase difference includes the following steps: B1. Based on the vibration displacement data of the current chord length of the flexible material test piece, record the signal waveform using sensor processing software; B2. Obtain the wave packet start point based on the signal waveform. To the node intercept point time interval ; The sensor detects the starting point of the wave packet acquired during the vibration process of the vibrating plate 2. To the node intercept point time interval Simultaneously, the instantaneous voltage of the first channel of signal generator 6 is recorded synchronously using the LabVIEW laboratory virtual instrument integration environment. Signal generator 6 second channel instantaneous voltage and the peak voltage of the first channel of signal generator 6 Peak voltage of the second channel of signal generator 6 The sensor can be a laser rangefinder. When recording the signal waveform during the vibration process, it can be analyzed and recorded by the SensorTool sensor analysis software connected to the sensor. The specific content of collecting and analyzing the vibration signal of the vibrating plate 2 through the micro laser rangefinder 1 and the sensor tool software is existing technology and will not be described in detail here. B3. According to time interval Calculate the phase information of the receiver end at the current chord length of the flexible material specimen:

[0056] In the formula, For the transmitting phase, Pi This is the theoretical value of the wave packet period. To analyze the actual period of the beat waveform, The frequency difference of the beat longitudinal wave signal; B4. Calculate the phase information of the current chord length output terminal of the flexible material specimen:

[0057] In the formula, For the output phase, The instantaneous phase of the first channel of the signal generator (6), The instantaneous phase of the second channel of the signal generator (6), The instantaneous voltage of the first channel of the signal generator (6) The peak voltage of the first channel of the signal generator (6) The instantaneous voltage of the second channel of the signal generator (6), The peak voltage of the second channel of the signal generator (6); (Note: arcsin) x The required interval for function values ​​needs to be determined manually. For example, the angle in the second quadrant can exist in experiments, while the phase value corresponding to (p / 2, p) is arcsin. x (Not equivalent to its principal value); B5. Calculate the phase difference of the current chord length of the flexible material specimen based on the phase information from the receiving end and the output end:

[0058] In the formula, This represents the phase difference between the output and receiving ends of the flexible material test specimen. In this embodiment, the detection parameters and phase calculation data for each chord length of the flexible material test specimen are shown in Table 1. Table 1 Experimental Data of Flexible Material Specimens

[0059] S3. Perform linear fitting on the data in the dependent variable dataset to obtain the chord length-phase difference fitting slope; specifically, this includes the following steps: C1. Linearly fit the phase difference between the output and receiving ends of the flexible material specimen to the chord length parameter of the flexible material specimen. Origin software can be used for linear fitting of the phase difference and chord length parameter. The specific details of the linear fitting are existing techniques and will not be elaborated here. The linear fitting results of the phase difference and chord length are shown in the attached figure. Figure 3 As shown; C2. Calculate the chord length-phase difference fitting slope based on the linear fitting results:

[0060] In the formula, The slope of the chord length-phase difference fitting is... Pi For the frequency difference of the beat longitudinal wave signal, The group velocity of a wave propagating in a string; S4. Based on the chord length-phase difference fitting slope and the physical parameter information of the flexible material specimen, calculate the elastic modulus of the flexible material specimen. The specific formula for calculating the elastic modulus of the flexible material specimen is as follows:

[0061] In the formula, The elastic modulus of the flexible material specimen. Pi For the frequency difference of the beat longitudinal wave signal, The slope of the chord length-phase difference fitting is... For the diameter of the flexible material test piece, For the quality of flexible material test specimens, The length of the flexible material test specimen.

Claims

1. A device for measuring the elastic modulus of flexible materials based on beat-longitudinal wave coupling, characterized in that, It includes a signal generation module, a signal acquisition and processing module, and a measurement auxiliary module; The signal generation module is used to synchronously output two sinusoidal signals with similar frequencies to excite the string vibration of the flexible material (3) and convert the tuned string vibration into mechanical vibration with front and rear displacement. The signal acquisition and processing module is used to analyze the displacement information of sinusoidal signals and mechanical vibrations, obtain the analysis results, and obtain the elastic modulus of the flexible material (3) based on the analysis results, the length and mass density of the flexible material (3); Specifically, the following steps are included: The phase difference between the output end and the receiving end of the flexible material (3) is linearly fitted with the chord length parameter of the flexible material (3); Calculate the chord length-phase difference fitting slope based on the linear fitting results: In the formula, The slope of the chord length-phase difference fitting is... Pi For the frequency difference of the beat longitudinal wave signal, The group velocity of a wave propagating in a string; Based on the chord length-phase difference fitting slope and the physical parameter information of the flexible material (3), the elastic modulus of the flexible material (3) is calculated: In the formula, The elastic modulus of the flexible material (3) is Pi For the frequency difference of the beat longitudinal wave signal, The slope of the chord length-phase difference fitting is... For the diameter of flexible material (3), For the quality of flexible materials (3), The length of the flexible material (3); The measurement auxiliary module is used to measure the length and mass density of the flexible material (3).

2. The flexible material elastic modulus measurement device based on beat-longitudinal wave coupling according to claim 1, characterized in that, The signal generation module includes a signal generator (6), several horn plates (4) and a vibrating plate (2); The signal generator (6) is used to synchronously output two sinusoidal signals with similar frequencies; Each of the aforementioned horn plates (4) is used to convert a sinusoidal wave signal into a longitudinal wave signal to excite the flexible material (3) to generate string vibration; The vibrating plate (2) is used to convert the tuned string vibration into mechanical vibration with forward and backward displacement; The frequency difference between the two sinusoidal signals is 0.1Hz to 1Hz.

3. The flexible material elastic modulus measurement device based on beat-longitudinal wave coupling according to claim 2, characterized in that, At least two horn plates (4) are provided, which are connected to the two channels of the signal generator (6) as excitation sources respectively; at least one vibrating plate (2) is provided, which is connected to the end of the flexible material (3) as a converter; the angle of the normal of each horn plate (4) is between 90° and 150°.

4. The flexible material elastic modulus measurement device based on beat-longitudinal wave coupling according to claim 1, characterized in that, The signal acquisition and processing module includes a data acquisition card (5), graphical programming software, a laser rangefinder (1), and sensor analysis software; The data acquisition card (5) is used to acquire sine wave signals; The graphical programming software is used to perform image processing based on each sine wave signal to obtain the phase difference; The laser rangefinder (1) is used to capture displacement information of the mechanical vibration of the vibrating plate (2) in real time; The sensor analysis software is used to analyze displacement information and phase difference, obtain analysis results, and obtain the elastic modulus of the flexible material (3) based on the analysis results, the length and mass density of the flexible material (3).

5. A method for measuring the elastic modulus of flexible materials using a device for measuring the elastic modulus of flexible materials based on beat-longitudinal wave coupling, characterized in that, Includes the following steps: S1. Use the measurement auxiliary module to collect the physical parameter information of the flexible material test piece, and detect the vibration displacement data of the flexible material test piece with different chord lengths under the beat sine wave signal; S2. Based on the physical parameter information and vibration displacement data collected in step S1, calculate the phase difference between the two ends of flexible material test pieces with different chord lengths, and integrate the phase differences of flexible material test pieces with different chord lengths to form a dependent variable dataset. S3. Perform linear fitting on the data in the dependent variable dataset to obtain the chord length-phase difference fitting slope; S4. Based on the chord length-phase difference fitting slope and the physical parameter information of the flexible material specimen, calculate the elastic modulus of the flexible material specimen. This includes the following steps: C1. Linearly fit the phase difference between the output and receiving ends of the flexible material test specimen to the chord length parameter of the flexible material test specimen. C2. Calculate the chord length-phase difference fitting slope based on the linear fitting results: In the formula, The slope of the chord length-phase difference fitting is... Pi For the frequency difference of the beat longitudinal wave signal, The group velocity of a wave propagating in a string; S4. Based on the chord length-phase difference fitting slope and the physical parameter information of the flexible material specimen, calculate the elastic modulus of the flexible material specimen: In the formula, The elastic modulus of the flexible material specimen. Pi For the frequency difference of the beat longitudinal wave signal, The slope of the chord length-phase difference fitting is... For the diameter of the flexible material test piece, For the quality of flexible material test specimens, The length of the flexible material test specimen.

6. The method for measuring the elastic modulus of flexible materials according to claim 5, characterized in that, In step S1, the vibration displacement data of the flexible material test piece with different chord lengths under beat sinusoidal wave signals are detected, specifically including: A1. Connect the two ends of the flexible material test piece to the signal generator (6) and the vibrating plate (2) respectively. The signal generator (6) sends a beat sine wave signal to the flexible material test piece and drives the vibrating plate (2) to vibrate through the flexible material test piece. A2. Collect vibration displacement data of the vibrating plate (2) during the vibration process using a laser rangefinder (1); A3. Determine whether the number of tests has reached the preset value. If yes, exit the test; otherwise, adjust the chord length of the flexible material test piece and return to step A1.

7. The method for measuring the elastic modulus of flexible materials according to claim 5, characterized in that, In step S2, the calculation of the phase difference includes the following steps: B1. Based on the vibration displacement data of the current chord length of the flexible material test piece, record the signal waveform using sensor processing software; B2. Obtain the wave packet start point based on the signal waveform. To the node intercept point time interval ; B3. According to time interval Calculate the phase information of the receiver end at the current chord length of the flexible material specimen: In the formula, For the transmitting phase, Pi This is the theoretical value of the wave packet period. To analyze the actual period of the beat waveform, The frequency difference of the beat longitudinal wave signal; B4. Calculate the phase information of the current chord length output terminal of the flexible material specimen: In the formula, For the output phase, The instantaneous phase of the first channel of the signal generator (6), The instantaneous phase of the second channel of the signal generator (6), The instantaneous voltage of the first channel of the signal generator (6) The peak voltage of the first channel of the signal generator (6) The instantaneous voltage of the second channel of the signal generator (6), The peak voltage of the second channel of the signal generator (6); B5. Calculate the phase difference of the current chord length of the flexible material specimen based on the phase information from the receiving end and the output end: In the formula, The phase difference between the output and receiving ends of the flexible material test specimen.

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