Stress wave simulation loading system based on signal acquisition and processing and experimental method thereof

Abstract

The invention provides a stress wave simulation loading system based on signal acquisition and processing and an experimental method thereof, and belongs to the technical field of stress wave simulation loading systems and experiments. In order to overcome the technical problems of poor accuracy and insufficient repeatability of a traditional stress wave simulation loading experiment, the invention provides a stress wave simulation loading system based on signal acquisition and processing and an experiment method thereof, and the technical scheme is that a signal output end of a microseismic signal acquisition module is connected with a signal processing and control module through a wire; the signal output end of the signal processing and control module is connected with the digital signal processor module through a wire. The signal output end of the digital signal processor module is connected with the signal amplification module through a wire. The signal output end of the signal amplification module is connected with the pulse current generator module through a wire. The device is applied to a stress wave simulation loading experiment.

Description

Technical Field

[0001] The invention provides a stress wave simulation loading system based on signal acquisition processing and an experimental method thereof, belonging to the technical field of stress wave simulation loading systems and experiments. Background Art

[0002] Engineering mechanics is a discipline that studies the most common and basic laws of mechanical motion in nature and various engineering projects. It aims to guide people to scientifically understand nature and engage in engineering and technical work. In engineering mechanics research, in order to simulate the mechanical state of real rock formations, it is usually necessary to conduct similar material simulation experiments in the laboratory. In similar material simulation experimental research, static loads can often only be set to simulate ground stress. For dynamic load simulation, impact hammers and other devices are mostly used to impact the model. Although these devices can generate certain dynamic loads, they are insufficient in accuracy compared to actual complex stress waves. Collecting actual stress waves and simulating the model's response to them is a more accurate and rigorous simulation method. Traditional experimental methods have problems such as poor accuracy and insufficient repeatability. To this end, it is necessary to improve the structure and experimental methods of the current stress wave simulation loading experimental system. Summary of the invention

[0003] In order to overcome the technical problems of poor accuracy and insufficient repeatability in traditional stress wave simulation loading experiments, the present invention provides a stress wave simulation loading system based on signal acquisition processing and an experimental method thereof.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a stress wave simulation loading system based on signal acquisition and processing, including a microseismic signal acquisition module for collecting ground vibration signals and converting analog signals into digital signals, and also including a signal processing and control module for denoising, filtering and preprocessing the collected digital signals, wherein the signal output end of the microseismic signal acquisition module is connected to the signal processing and control module through a wire; The signal output end of the signal processing and control module is connected to the digital signal processor module through a wire, and the digital signal processor module is used to generate and modulate the stress wave signal and perform data processing and analysis; The signal output end of the digital signal processor module is connected to the signal amplification module through a wire, and the signal amplification module is used to amplify the low voltage analog signal sent by the digital signal processor module to the required voltage and current levels; The signal output end of the signal amplification module is connected to the pulse current generator module through a wire, and the pulse current generator module is used to convert the amplified signal into a pulse current through a switch circuit; The signal output end of the pulse current generator module is connected to the stress wave generator module through a wire. The stress wave generator module is used to convert the electrical signal in the pulse current generator into mechanical vibration. The stress wave generator module is arranged in the simulation test bench.

[0005] The microseismic signal acquisition module is specifically an IHMS integrated vibration monitoring system; A bandpass filter is provided in the microseismic signal acquisition module for filtering out invalid frequency band noise and retaining the target vibration signal.

[0006] The signal amplification module is specifically a signal amplifier of model OPA2134. A compensation capacitor is arranged in the feedback loop of the signal amplifier, and an RC low-pass filter is arranged at the output end of the signal amplifier.

[0007] The digital signal processor module is specifically a digital signal processor with model number PXIE-8861 NI.

[0008] The pulse current generator module is specifically a pulse current generator of model EPG-300M.

[0009] It also includes a power management module for supplying power to the entire stress wave simulation loading system. The power management module is specifically a DC-DC isolated power supply with uninterrupted power supply.

[0010] The method for conducting an experiment based on a stress wave simulation loading system for signal acquisition and processing includes the following experimental steps: Step 1: The microseismic signal acquisition module uses the IHMS integrated vibration monitoring system to collect ground vibration signals, uses a detector to capture the signal, and converts the collected analog signal into a digital signal through a digital-to-analog converter; Step 2: transmitting the digital signal to the signal processing and control module for preprocessing, and sending the preprocessed signal to the digital signal processor module, wherein the digital signal processor module generates a stress wave signal according to preset stress wave parameters, and performs modulation and data processing operations on the generated stress wave signal; Step 3: Connect the signal amplifier module to the pulse current generator module, and the signal amplifier module enhances the low voltage analog signal sent from the digital signal processor module, processes the signal through the compensation capacitor and the RC low-pass filter, and sends the processed and optimized signal to the pulse current generator module to convert it into a high-amplitude pulse current; Step 4: The stress wave generator module receives the pulse current from the pulse current generator module and converts the pulse current into mechanical vibration energy through the hammer head. The stress wave generated by the mechanical vibration propagates in the medium to simulate and load the required stress environment. Step 5: Real-time monitoring of the propagation of stress waves in the medium and the response of the medium under the action of stress waves. By monitoring the deviation between real-time data and preset parameters, the parameters of stress waves are continuously optimized and adjusted to conduct repeated experiments. Step 6: The digital signal processor module extracts characteristic parameters of the stress wave propagating in the medium and evaluates the propagation characteristics of the stress wave and the properties of the medium.

[0011] The specific method for the digital signal processor module in step 2 to perform modulation and data processing operations on the generated stress wave signal is: The digital signal processor module generates a stress wave signal according to the preset frequency, amplitude and waveform parameters of the stress wave; Performing signal modulation and data processing operations on the generated stress wave signal, wherein the signal modulation operation includes: frequency modulation, amplitude modulation, phase modulation, and the data processing operation includes: filtering, smoothing, and enhancing the signal; Perform feature extraction on the modulated and processed signal to extract the signal's peak value, frequency, and amplitude parameters; Finally, data analysis is performed based on the extracted characteristic parameters to evaluate the propagation characteristics of stress waves and medium properties.

[0012] The specific method of processing the signal through the compensation capacitor and the RC low-pass filter in the signal amplification module in step 3 is: Based on the received low-voltage analog signal, the compensation capacitor in the signal amplification module and the components in the circuit form a resonant circuit to compensate for the signal phase distortion; the RC low-pass filter filters out high-frequency noise and interference in the signal, and the cutoff frequency of the filter is controlled by adjusting the resistance and capacitance.

[0013] The specific method for evaluating the propagation characteristics of stress waves and medium properties in step 6 is: When the stress wave encounters the medium interface, reflection and transmission will occur. The calculation formula for the reflection and transmission coefficients is: ; Where R represents the reflection coefficient, Z 1 and Z 2 Respectively represent the wave impedance of the two media and calculate the transmission coefficient. The calculation formula is: ; Where B represents the transmission coefficient; After the stress wave characteristics are initially calculated and screened, the signal is transformed and processed. The calculation formula for the transformation processing is: ; Where x(t) is the original stress wave signal, x i + (t) and xi - (t) are the new signals formed by adding positive and negative auxiliary waves, V i (t) is the auxiliary wave, β 0 is the amplitude of the auxiliary wave, E 1 is the operator; The signal is calculated several times and we get: ; In the formula, M(x i + (t)) and M(x i - (t)) is the signal x i + (t) and x i - (t) is the envelope value of the IMF component, R(t) is the mean value of the overall envelope, IMF(t) is the IMF component of this stage; I is the number of calculations; Repeat the above calculation several times and perform HT transformation on the components. The calculation formula is: ; In the formula, For IMF k (t) is the HT transformation result, τ is the integral variable, t is the time variable; The analytical signal is formed and the expression is: ; The parameters of the stress wave components are obtained as follows: ; ; ; Where a(t) represents the instantaneous amplitude of the stress wave, θ(t) represents the instantaneous phase of the stress wave, ω(t) represents the instantaneous frequency of the stress wave, c(t) represents the stress wave signal after EMD decomposition, and H(c(t)) represents the stress wave signal after HT transformation; After the stress wave signal is decomposed by EMD and HT transformed, the instantaneous amplitude, instantaneous phase and instantaneous frequency of the stress wave are calculated; The damped natural frequency and damping ratio of the stress wave component are further calculated using the following formula: ; ; In the formula, ω d is the damped natural frequency, ω is the damped natural original frequency, ζ is the analysis error, f d is the damping ratio; The instantaneous amplitude of the stress wave, the instantaneous phase of the stress wave, the instantaneous frequency of the stress wave, the damped natural frequency, and the damping ratio obtained by the above calculations are taken as evaluation conclusions.

[0014] The beneficial effects of the present invention compared with the prior art are as follows: the stress wave simulation and loading system proposed in the present invention can accurately collect and filter ground vibration signals and retain target vibration signals through the high-sensitivity detector and bandpass filter of the microseismic signal acquisition module, thereby improving the accuracy and precision of signal acquisition; the set digital signal processor module can generate and modulate stress wave signals, perform fine data processing and analysis, and further improve the accuracy of stress wave simulation; the set power management module adopts an uninterruptible power supply system and a DC-DC isolated power supply to ensure the continuous operation of the system during power failures and enhance the reliability and stability of the system; the system can automatically complete the simulation and loading process of stress waves, reduce the tediousness and errors of manual operations, improve the accuracy of experiments, and provide a more accurate and rigorous simulation method for research in the field of rock mechanics, which is helpful to reveal the mechanical properties of rocks and the propagation laws of stress waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be further described below in conjunction with the accompanying drawings: Figure 1 It is a structural schematic diagram of the stress wave simulation loading system of the present invention; Figure 2 Schematic diagram of the circuit structure of the signal amplification module of the present invention; Figure 3 Schematic diagram of the circuit structure of the signal pulse current generator module of the present invention; Figure 4 Schematic diagram of the circuit structure of the DC-DC power supply module of the present invention; Figure 5 This is an experimental effect diagram of a stress wave simulation loading system combined with similar materials in an embodiment of the present invention; In the figure: 1 is a digital signal processor module, 2 is a signal amplification module, 3 is a pulse current generator module, 4 is a stress wave generator module, and 5 is a similar material simulation test bench. DETAILED DESCRIPTION

[0016] like Figures 1 to 5As shown, the stress wave simulation loading system provided by the present invention mainly includes: a microseismic signal acquisition module, a signal processing and control module, a power management module, a digital signal processor module 1, a signal amplification module 2, a pulse current generator module 3 and a stress wave generator module 4; wherein, the microseismic signal acquisition module is used to collect ground vibration signals and convert analog signals into digital signals; the high-sensitivity detector and bandpass filter are set, which can accurately collect and filter ground vibration signals, retain target vibration signals, thereby improving the accuracy and precision of signal acquisition, and can automatically complete the simulation and loading process of stress waves, reducing the tediousness and errors of manual operations, improving experimental efficiency, and helping to reveal the mechanical properties of rocks and the propagation laws of stress waves; the system provided by the present invention can accurately collect ground vibration signals, pre-process, generate and modulate stress wave signals, generate mechanical vibrations through amplification and conversion to form target stress waves, and can be used in similar material simulation test benches at the same time, and the power management module ensures that the system is stable and reliable.

[0017] The microseismic signal acquisition module provided by the present invention ensures that the system can accurately and reliably acquire ground vibration signals by adopting a high-sensitivity detector, a bandwidth, a high-precision synchronization mechanism, and a high-resolution digital-to-analog converter, providing a solid foundation for subsequent signal processing and analysis; the microseismic signal acquisition module is specifically an IHMS integrated vibration monitoring system, and its basic parameters are: the detector sensitivity is 18v·m / s, the bandwidth is 1-1500Hz, and the synchronization time error of each measuring point is less than 10 -6 s, the resolution of the digital-to-analog converter is 24 bits, and the sampling rate is 38.4 kSPS; the microseismic signal acquisition module stores the collected stress wave signals for subsequent laboratory settings.

[0018] In the laboratory, the stress wave signal collected by the microseismic signal acquisition module is generated and modulated by the digital signal processor module 1, and data processing and analysis are performed. The method of data processing and analysis is as follows: The digital signal processor module 1 is responsible for receiving the preprocessed signal in the stress wave simulation system, generating the stress wave signal according to the preset parameters, and performing frequency, amplitude and phase modulation, filtering, smoothing and enhancement. After that, the module extracts the signal characteristic parameters, including peak value, frequency and amplitude, and performs data analysis to evaluate the stress wave propagation characteristics and medium properties.

[0019] The specific method for evaluating stress waves is: When the stress wave encounters the medium interface, reflection and transmission will occur. The coefficient calculation formula of reflection and transmission is: ; Where R represents the reflection coefficient, Z 1 and Z 2Respectively represent the wave impedance of the two media and calculate the transmission coefficient. The calculation formula is: ; Where B represents the transmission coefficient; After the stress wave characteristics are initially calculated and screened, the signal is transformed and processed by the processing module. The processing method is as follows: ; x(t) is the original stress wave signal, x i + (t) and x i - (t) are the new signals formed by adding positive and negative auxiliary waves, V i (t) is the auxiliary wave, β 0 is the amplitude of the auxiliary wave, E 1 is the operator; After calculating the signal several times, we can get: ; In the formula, M(x i + (t)) and M(x i - (t)) is the signal x i + (t) and x i - (t) is the envelope value of the IMF component, R(t) is the mean value of the overall envelope, IMF(t) is the IMF component of this stage, I is the number of calculations in the above calculations, and the greater the number of calculations, the smaller the error; Repeat the above calculation several times and perform HT transformation on the components: ; In the formula, For IMF k (t) is the HT transformation result, τ is the integral variable, t is the time variable, representing a certain time point in the decomposition calculation process; Then the analytical signal can be constructed: ; Then the parameters of the stress wave component can be obtained as: ; ; ; Where a(t) represents the instantaneous amplitude of the stress wave, θ(t) represents the instantaneous phase of the stress wave, ω(t) represents the instantaneous frequency of the stress wave, c(t) represents the stress wave signal after EMD decomposition, and H(c(t)) represents the stress wave signal after HT transformation.

[0020] After the stress wave signal is decomposed by EMD and HT transformed, the instantaneous amplitude, instantaneous phase and instantaneous frequency of the stress wave are calculated.

[0021] In order to improve the recognition accuracy, the damped natural frequency and damping ratio of the stress wave component can be further calculated: ; ; In the formula, ω d is the damped natural frequency, ω is the damped natural original frequency, ζ is the analysis error, f d is the damping ratio.

[0022] The stress wave signal processed by the digital signal processor module 1 is analyzed and processed and then decomposed into a number of relatively regular stress wave signals according to the frequency, so that the stress wave generation module 4 can restore the stress wave to a higher degree.

[0023] The digital signal processor module 1 is connected to the signal amplification module 2, and processes the evaluated stress wave signal in the signal amplification module to make it reach the voltage of the stress wave generation module.

[0024] The frequency response capability of the signal amplification module 2 has an upper limit of 8MHz, which ensures that the module can maintain the integrity and accuracy of the signal when processing high-frequency signals. In order to meet the needs of high-performance signal amplification and reduce distortion and interference during the amplification process, the amplifier's phase delay and gain reduction problems in the high-frequency band are effectively improved, thereby ensuring that the signal can maintain stable phase and amplitude characteristics during the amplification process, thereby ensuring the purity and stability of the output signal.

[0025] The signal amplification module 2 is connected to the pulse current generator 3, and the signal optimized by the signal amplification module 2 is output to the pulse current generator 3 and converted into a high-amplitude pulse current.

[0026] The pulse current generator 3 is connected to the stress wave generator module 4, and the stress wave generator module 4 is connected to the hammer head and arranged on the similar material simulation test bench 5 to simulate the earthquake source. After the stress wave generator module 4 converts the high-amplitude pulse current into mechanical vibration and generates the required stress wave, the real characteristics of the collected stress wave are reproduced in proportion, and can be effectively propagated in the simulated material to complete the experimental results.

[0027] The use process of the present invention is as follows: the microseismic signal acquisition module collects vibration signals and converts them into digital signals; the signal processing and control module pre-processes the digital signals, uses the characteristic parameters of the digital signal processor module to evaluate the stress wave propagation characteristics and medium properties, generates stress wave signals according to preset parameters, and performs modulation and data processing; the signal amplification module enhances the signal and converts it into a high-amplitude pulse current after optimization; the stress wave generator module converts the pulse current into mechanical vibration through a hammer head, reproduces the real characteristics of the collected stress wave in proportion, and can effectively propagate in the simulated material.

[0028] In summary, the advantages of the present invention are: the stress wave simulation and loading system can improve the simulation accuracy, which is achieved through a high-sensitivity detector, a bandpass filter and a digital signal processor 1; enhance system reliability, adopt an uninterruptible power supply and a reasonable electrical connection design; optimize stress wave loading, and improve signal quality and stress wave parameters through a signal amplifier 2 and a stress wave generator module 4; improve experimental efficiency and repeatability, realize automated operation and stabilize experimental results; promote the development of rock mechanics research, provide accurate simulation methods, and assist engineering design and construction.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A stress wave simulation loading system based on signal acquisition and processing, characterized by: It includes a microseismic signal acquisition module for collecting ground vibration signals and converting analog signals into digital signals, and also includes a signal processing and control module for denoising, filtering and preprocessing the collected digital signals. The signal output end of the microseismic signal acquisition module is connected to the signal processing and control module through a wire; The signal output end of the signal processing and control module is connected to a digital signal processor module (1) via a wire, and the digital signal processor module (1) is used to generate and modulate stress wave signals and perform data processing and analysis; The signal output end of the digital signal processor module (1) is connected to the signal amplification module (2) via a wire, and the signal amplification module (2) is used to amplify the low-voltage analog signal sent by the digital signal processor module (1) to a required voltage and current level; The signal output end of the signal amplification module (2) is connected to a pulse current generator module (3) via a wire, and the pulse current generator module (3) is used to convert the amplified signal into a pulse current via a switch circuit; The signal output end of the pulse current generator module (3) is connected to the stress wave generator module (4) via a wire; the stress wave generator module (4) is used to convert the electrical signal in the pulse current generator into mechanical vibration; and the stress wave generator module (4) is arranged in a simulation test bench.

2. The stress wave simulation loading system based on signal acquisition and processing according to claim 1 is characterized in that: The microseismic signal acquisition module is specifically an IHMS integrated vibration monitoring system; A bandpass filter is provided in the microseismic signal acquisition module for filtering out invalid frequency band noise and retaining the target vibration signal.

3. The stress wave simulation loading system based on signal acquisition and processing according to claim 1 is characterized in that: The signal amplification module (2) is specifically a signal amplifier of model OPA2134, a compensation capacitor is provided in the feedback loop of the signal amplifier, and an RC low-pass filter is provided at the output end of the signal amplifier.

4. The stress wave simulation loading system based on signal acquisition and processing according to claim 1 is characterized in that: The digital signal processor module (1) is specifically a digital signal processor of model PXIE-8861 NI.

5. The stress wave simulation loading system based on signal acquisition and processing according to claim 1 is characterized in that: The pulse current generator module (3) is specifically a pulse current generator of model EPG-300M.

6. The stress wave simulation loading system based on signal acquisition and processing according to claim 1 is characterized in that: It also includes a power management module for supplying power to the entire stress wave simulation loading system. The power management module is specifically a DC-DC isolated power supply with uninterrupted power supply.

7. The method for conducting experiments using a stress wave simulation loading system based on signal acquisition and processing according to claim 1, characterized in that: The experimental steps include the following: Step 1: The microseismic signal acquisition module uses the IHMS integrated vibration monitoring system to collect ground vibration signals, uses a detector to capture the signal, and converts the collected analog signal into a digital signal through a digital-to-analog converter; Step 2: transmitting the digital signal to the signal processing and control module for preprocessing, and sending the preprocessed signal to the digital signal processor module (1), wherein the digital signal processor module (1) generates a stress wave signal according to preset stress wave parameters, and performs modulation and data processing operations on the generated stress wave signal; Step 3: Connect the signal amplification module (2) to the pulse current generator module (3), so that the signal amplification module (2) can enhance the low voltage analog signal sent from the digital signal processor module (1), process the signal through the compensation capacitor and the RC low-pass filter, and send the processed optimized signal to the pulse current generator module (3) to convert it into a high amplitude pulse current; Step 4: The stress wave generator module (4) receives the pulse current from the pulse current generator module (3), and converts the pulse current into mechanical vibration energy through the hammer head. The stress wave generated by the mechanical vibration propagates in the medium and is used to simulate and load the required stress environment; Step 5: Real-time monitoring of the propagation of stress waves in the medium and the response of the medium under the action of stress waves. By monitoring the deviation between real-time data and preset parameters, the parameters of stress waves are continuously optimized and adjusted to conduct repeated experiments. Step 6: The digital signal processor module (1) extracts characteristic parameters of the stress wave propagating in the medium and evaluates the propagation characteristics of the stress wave and the properties of the medium.

8. The method for conducting experiments using a stress wave simulation loading system based on signal acquisition and processing according to claim 7, characterized in that: The specific method of the digital signal processor module (1) in step 2 for performing modulation and data processing operations on the generated stress wave signal is: The digital signal processor module (1) generates a stress wave signal according to the preset frequency, amplitude and waveform parameters of the stress wave; Performing signal modulation and data processing operations on the generated stress wave signal, wherein the signal modulation operation includes: frequency modulation, amplitude modulation, phase modulation, and the data processing operation includes: filtering, smoothing, and enhancing the signal; Perform feature extraction on the modulated and processed signal to extract the signal's peak value, frequency, and amplitude parameters; Finally, data analysis is performed based on the extracted characteristic parameters to evaluate the propagation characteristics of stress waves and medium properties.

9. The method for conducting experiments using a stress wave simulation loading system based on signal acquisition and processing according to claim 7, characterized in that: The specific method of processing the signal through the compensation capacitor and the RC low-pass filter in the signal amplification module (2) in step 3 is: Based on the received low-voltage analog signal, the compensation capacitor in the signal amplification module (2) and the components in the circuit form a resonant circuit to compensate for the signal phase distortion; the high-frequency noise and interference in the signal are filtered out by the RC low-pass filter, and the cut-off frequency of the filter is controlled by adjusting the resistance and capacitance.

10. The method for conducting experiments using a stress wave simulation loading system based on signal acquisition and processing according to claim 7, characterized in that: The specific method for evaluating the propagation characteristics of stress waves and medium properties in step 6 is: When the stress wave encounters the medium interface, reflection and transmission will occur. The calculation formula for the reflection and transmission coefficients is: ； In the formula, R represents the reflection coefficient, Z1 and Z2 represent the wave impedance of the two media respectively, and the transmission coefficient is calculated as follows: ； Where B represents the transmission coefficient; After the stress wave characteristics are initially calculated and screened, the signal is transformed and processed. The calculation formula for the transformation processing is: ； Where x(t) is the original stress wave signal, x i + (t) and x i - (t) are the new signals formed by adding positive and negative auxiliary waves, V i (t) is the auxiliary wave, β0 is the amplitude of the auxiliary wave, and E1 is the operator; After the signal is calculated several times, we get: ； In the formula, M(x i + (t)) and M(x i - (t)) is the signal x i + (t) and x i - (t) is the envelope value of the IMF component, R(t) is the mean value of the overall envelope, IMF(t) is the IMF component of this stage; I is the number of calculations; Repeat the above calculation several times and perform HT transformation on the components. The calculation formula is: ； In the formula, For IMF k (t) is the HT transformation result, τ is the integral variable, t is the time variable; The analytical signal is formed and the expression is: ； The parameters of the stress wave components are obtained as follows: ； ； ； Where a(t) represents the instantaneous amplitude of the stress wave, θ(t) represents the instantaneous phase of the stress wave, ω(t) represents the instantaneous frequency of the stress wave, c(t) represents the stress wave signal after EMD decomposition, and H(c(t)) represents the stress wave signal after HT transformation; After the stress wave signal is decomposed by EMD and HT transformed, the instantaneous amplitude, instantaneous phase and instantaneous frequency of the stress wave are calculated; The damped natural frequency and damping ratio of the stress wave component are further calculated using the following formula: ； ； In the formula, ω d is the damped natural frequency, ω is the damped natural original frequency, ζ is the analysis error, f d is the damping ratio; The instantaneous amplitude of the stress wave, the instantaneous phase of the stress wave, the instantaneous frequency of the stress wave, the damped natural frequency, and the damping ratio obtained by the above calculations are taken as evaluation conclusions.

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