Stress wave segment-based damage analysis method

Abstract

The present application relates to a kind of damage analysis methods based on stress wave segmentation, by the segmentation of stress wave, the stress wave obtained by one impact can analyze the damage situation inside sample or structure, avoid the damage test of additional after structure is impacted, improve the timeliness of damage identification;Solve the problem that traditional damage test needs to use other equipment to detect the damage of sample, in this process, the sample will be disturbed to different degrees, leading to the error of experiment;The present application can test and analyze the method of rock, concrete and other solid materials dynamic impact damage evolution and its amplitude and frequency spectrum and other attenuation law influence under in-situ pressure state.Made up for the defects of the existing technical method of rock, concrete and other solid materials dynamics test based on hopkinson bar in the aspect of material dynamic damage test under in-situ pressure state.

Description

Technical Field

[0001] This invention relates to the field of dynamic damage analysis technology for internal structures, and in particular to a damage analysis method based on stress wave segmentation. Background Technology

[0002] With the vigorous development of my country's economic construction, infrastructure construction under complex geological conditions is also increasing. Rock, as a brittle composite material, is susceptible to internal damage under external forces, leading to instability and failure, ultimately reducing structural load-bearing capacity and potentially causing significant engineering problems. Therefore, detecting the failure mechanism of loaded rock is particularly important. During construction, external factors such as stress unloading and blasting excavation inevitably damage the rock. This damage fundamentally alters the rock's internal material structure, mechanical behavior, and engineering response, resulting in a decrease in rock strength. Understanding the dynamic damage evolution of solid materials such as rock and concrete will help in the qualitative and quantitative analysis of the impact of dynamic damage evolution on the propagation and attenuation of ultrasonic and stress waves.

[0003] Existing techniques for studying dynamic damage involve disassembling the specimen after dynamic and static loading with a Hopkinson bar, and then using other equipment (such as CT scanners or ultrasonic instruments) to perform damage detection. These methods separate the dynamic and static loading with damage detection. Firstly, the process of performing damage detection after the dynamic impact may introduce secondary impacts and disturbances to the target, increasing the error in the measured results. Secondly, in practical applications, performing damage detection after the structure has been impacted significantly reduces the timeliness of monitoring. Currently, it is not possible to study the dynamic damage of materials such as rock and concrete and its impact on ultrasonic wave propagation and attenuation under in-situ pressure conditions. Summary of the Invention

[0004] To address the above problems, this invention provides a damage analysis method based on stress wave segmentation, which avoids the need for additional damage testing after the structure is subjected to impact, and improves the timeliness of damage identification.

[0005] The technical solution adopted in this invention is: a damage analysis method based on stress wave segmentation, characterized by the following steps:

[0006] S1. The incident rod is struck at a set impact velocity, generating an incident stress wave; the incident stress wave propagates along the incident rod to the sample interface, generating reflected and transmitted waves;

[0007] S2. The stress-strain curve of a stress wave is divided into three stages in the time domain: the elastic stage, the plastic stage, and the failure stage. Corresponding to the stress-strain curve, the incident wave is defined in the time domain as T in chronological order.入射1 S 入射1 T 入射2 The three stages correspond to the transmitted waves obtained after these three waves pass through the sample, which are defined in chronological order as T. 透射1 S 透射1 T 透射2 Three stages, where T represents elastic wave and S represents plastic wave;

[0008] S3. Compare and analyze the three stages corresponding to the incident wave and the transmitted wave. Since the wave velocity of the elastic wave remains constant when passing through the same medium, T 入射1 To T 透射1 The wave speed remains unchanged; S 入射1 Passing through the sample will cause damage to the sample, leading to the appearance of cracks, which in turn will affect the elastic wave T after passing through the sample. 入射2 To T 透射2 The wave velocity decreases, and wavelet analysis can obtain wavebands of different frequencies, allowing for a comparison of the incident and transmitted T values. 入射2 and T 透射2 By analyzing the amplitude of each band, it can be seen which frequency band's wave energy was absorbed, resulting in a decrease in amplitude, thus revealing the composition of the cracks in the sample.

[0009] As a preferred option, the specific steps of S3 are as follows:

[0010] Through T 入射2 To T 透射2 The degree of wave velocity attenuation is used to preliminarily determine whether the internal structure of the sample has been damaged and the extent of the damage. Wave velocity attenuation rate is defined as...

[0011]

[0012] In the formula: V is the stress wave velocity of the undamaged sample, i.e., T 入射1 The wave velocity is V', which is the stress wave velocity after the specimen is damaged by the second plastic wave S, i.e., T. 透射2 wave speed;

[0013]

[0014]

[0015] In the formula: S is the distance from the incident measuring point to the transmission measuring point; Δt1 is the time it takes for the first segment of the stress wave to propagate from the incident measuring point to the transmission measuring point, i.e., from T 入射1 To T 透射1 The time; Δt2 is the time it takes for the third stress wave to propagate from the incident measuring point to the transmitted measuring point, that is, from T... 入射2 To T 透射2 Time;

[0016] Damage to the structure is determined when the wave velocity attenuation rate η reaches a set threshold, and the incident and transmitted waves T are then considered to be damaged. 入射2 and T 透射2 These two waves are processed by wavelet transform to analyze the amplitude differences of each corresponding frequency band, and then the internal crack situation of the sample is analyzed.

[0017] Preferably, the wave velocity attenuation rate η is greater than or equal to 5%, which indicates that the structure has been damaged.

[0018] As a preferred method, the wavelet toolbox in MATLAB is used to analyze the incident and transmitted T values. 入射2 and T 透射2 These two waves are then subjected to wavelet transform.

[0019] As a preferred method, a Hopkinson bar device is used to perform damage analysis on the sample. The gas pressure chamber is adjusted to control the bullet to impact the incident bar at a set impact velocity to generate an incident stress wave. When the incident stress wave propagates along the incident bar to the sample interface, it generates reflected waves and transmitted waves. The signals are measured by strain gauges on the incident bar and the transmission bar, amplified by a Wheatstone bridge, and recorded and stored by an eight-channel digital oscilloscope.

[0020] Preferably, the Hopkinson rod device includes an incident rod, a transmission rod, and a sample.

[0021] Preferably, the incident rod and the transmission rod are made of 50mm diameter steel rods with an elastic modulus of 210GPa, the material is 48CrMoA, and the wave velocity is 5.270km / s; the length of the incident rod is 3.0m, and the length of the transmission rod is 1.8m.

[0022] Preferably, the sample is granite.

[0023] Preferably, the first end of the incident rod is provided with a copper sheet as a shaper.

[0024] Preferably, the surfaces of the sample that come into contact with the incident rod and the transmission rod are coated with petroleum jelly.

[0025] The beneficial effects achieved by this invention are:

[0026] 1. By creatively proposing a segmentation method for stress waves, the damage inside the sample or structure can be analyzed from the stress wave obtained by a single impact, avoiding the need for additional damage testing after the structure is impacted, and improving the timeliness of damage identification.

[0027] 2. It solves the problem that traditional damage testing requires the use of other equipment to detect damage to the sample, which can cause varying degrees of disturbance to the sample and lead to experimental errors.

[0028] 3. This invention provides a method for testing and analyzing the dynamic impact damage evolution of solid materials such as rock and concrete, as well as the influence of attenuation laws on amplitude and spectrum, under in-situ pressure holding conditions. This overcomes the shortcomings of existing Hopkinson bar-based dynamic testing techniques for solid materials such as rock and concrete in in-situ pressure holding conditions for dynamic damage testing. Attached Figure Description

[0029] Figure 1 This is a flowchart of the present invention;

[0030] Figure 2 This is a schematic diagram of the Hopkinson bar mechanism;

[0031] Figure 3 This is a schematic diagram of the segmented stress-strain curve;

[0032] Figure 4 A schematic diagram showing the segmentation of a stress wave (incident wave, transmitted wave);

[0033] Figure 5 For the incident wave T 入射2 Duan Xiaobo's analysis;

[0034] Figure 6 For transmitted wave T 透射2 Duan Xiaobo's analysis;

[0035] Figure 7 For the incident wave T 入射2 Segment wavelet analysis of detail coefficient spectrum;

[0036] Figure 8 For transmitted wave T 透射2 Segment wavelet analysis of detail coefficient spectrum;

[0037] Figure 9 Comparison of amplitude values ​​in different frequency bands for wavelet analysis of incident and transmitted waves;

[0038] The components are: 1. Bullet; 2. Incident rod; 3. Transmission rod; 4. Strain gauge; 5. Sample; 6. Absorption device. Detailed Implementation

[0039] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments:

[0041] like Figure 1-9As shown, the present invention provides a damage analysis method based on stress wave segmentation, characterized by comprising the following steps:

[0042] S1. The incident rod is impacted at a certain impact speed, generating an incident stress wave; the incident stress wave propagates along the incident rod to the sample interface, generating reflected and transmitted waves.

[0043] S2. The stress-strain curve of a stress wave is divided into three stages in the time domain: the elastic stage, the plastic stage, and the failure stage. Corresponding to the stress-strain curve, the incident wave is defined in the time domain as T in chronological order. 入射1 S 入射1 T 入射2 The three stages correspond to the transmitted waves obtained after these three waves pass through the sample, which are defined in chronological order as T. 透射1 S 透射1 T 透射2 Three stages, where T represents elastic wave and S represents plastic wave;

[0044] S3. Compare and analyze the three stages corresponding to the incident wave and the transmitted wave. Since the wave velocity of the elastic wave remains constant when passing through the same medium, T 入射1 To T 透射1 The wave speed remains unchanged; S 入射1 Passing through the sample will cause damage to the sample, leading to the appearance of cracks, which in turn will affect the elastic wave T after passing through the sample. 入射2 To T 透射2 The wave velocity decreases, and wavelet analysis can obtain wavebands of different frequencies, allowing for a comparison of the incident and transmitted T values. 入射2 and T 透射2 By analyzing the amplitude of each band, it can be seen which frequency band's wave energy was absorbed, resulting in a decrease in amplitude, thus revealing the composition of the cracks in the sample.

[0045] The specific steps for S3 are as follows:

[0046] Through T 入射2 To T 透射2 The degree of wave velocity attenuation is used to preliminarily determine whether the internal structure of the sample has been damaged and the extent of the damage. Wave velocity attenuation rate is defined as...

[0047]

[0048] In the formula: V is the stress wave velocity of the undamaged sample, i.e., T 入射1 The wave velocity is V', which is the stress wave velocity after the specimen is damaged by the second plastic wave S, i.e., T. 透射2 wave speed;

[0049]

[0050]

[0051] In the formula: S is the distance from the incident measuring point to the transmission measuring point; Δt1 is the time it takes for the first segment of the stress wave to propagate from the incident measuring point to the transmission measuring point, i.e., from T 入射1 To T 透射1 The time; Δt2 is the time it takes for the third stress wave to propagate from the incident measuring point to the transmitted measuring point, that is, from T... 入射2 To T 透射2 Time;

[0052] When the wave velocity attenuation rate η is greater than or equal to 5%, damage to the structure is determined. The wavelet toolbox in MATLAB is used to analyze the incident and transmitted T waves. 入射2 and T 透射2 These two waves were subjected to wavelet transform processing to analyze the amplitude differences in corresponding frequency bands, thereby revealing the internal crack conditions of the sample. Figure 9 The amplitude comparison chart for each frequency band clearly shows the T of the transmitted wave. 透射2 The amplitude of each frequency band compared to the incident wave T 入射2 The amplitude of the corresponding frequency bands is significantly reduced, and the reduction in amplitude can be used to analyze the fracture situation within the rock sample.

[0053] Example 1:

[0054] 1. Dynamic mechanical property testing of granite using a Hopkinson bar apparatus: The test system consists of a dynamic loading device, incident rods 2 and transmission rods 3 in three directions, a wave-absorbing device 6 (to prevent energy rebound), and a data acquisition system. The incident rods 2 and transmission rods 3 are made of 50mm diameter steel rods with an elastic modulus of 210GPa. The material of the pressure rods (incident rods and transmission rods) is 48CrMoA. The lengths of the incident rods 2 and transmission rods 3 are 3.0m and 1.8m, respectively. The wave velocity of the steel rods (incident rods and transmission rods) is 5.270km / s.

[0055] The incident stress wave is generated by controlling the bullet 1 to impact the incident rod 2 at a certain impact velocity according to the gas pressure chamber. When the incident stress wave propagates along the incident rod to the sample interface, it generates a reflected tensile wave (reflected wave) and a transmitted compression wave (transmitted wave). The signal recording system consists of a strain amplifier and a digital oscilloscope. The signal is measured by the strain gauges 4 on the incident rod 2 and the transmission rod 3. After being amplified by the Wheatstone bridge (strain amplifier), it is recorded and stored by the eight-channel digital oscilloscope.

[0056] During the experiment, a 1.5 mm thick copper sheet was selected as the shaper to eliminate high-frequency wave components and reduce wave dispersion. Vaseline was applied to the contact surfaces of sample 5 (granite sample) and the SHPB rods (incident and transmission rods) to reduce end friction effects.

[0057] 2. Test air pressures: 0.15 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa. The results are shown in the table below.

[0058]

[0059] Finally, it should be noted that the above embodiments are merely representative examples of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention should be considered within the protection scope of the present invention.

Claims

1. A damage analysis method based on stress wave segmentation, characterized in that: Includes the following steps: S1. The incident rod is struck at a set impact speed to generate an incident stress wave; The incident stress wave propagates along the incident rod to the sample interface, generating reflected and transmitted waves. S2. The stress-strain curve of a stress wave is divided into three stages in the time domain: the elastic stage, the plastic stage, and the failure stage. Corresponding to the stress-strain curve, the incident wave is defined in the time domain as T in chronological order. 入射1 S 入射1 T 入射2 The three stages correspond to the transmitted waves obtained after these three waves pass through the sample, which are defined in chronological order as T. 透射1 S 透射1 T 透射2 Three stages, where T represents elastic wave and S represents plastic wave; S3. Compare and analyze the three stages corresponding to the incident wave and the transmitted wave. Since the wave velocity of the elastic wave remains constant when passing through the same medium, T 入射1 To T 透射1 The wave speed remains unchanged; S 入射1 Passing through the sample will cause damage to the sample, leading to the appearance of cracks, which in turn will affect the elastic wave T after passing through the sample. 入射2 To T 透射2 The wave velocity decreases, and wavelet analysis can obtain wavebands of different frequencies, allowing for a comparison of the incident and transmitted T values. 入射2 and T 透射2 By analyzing the amplitude of each band, it can be seen which frequency band's wave energy was absorbed, resulting in a decrease in amplitude, thus revealing the composition of the cracks in the sample. The specific steps are as follows: Through T 入射2 To T 透射2 The degree of wave velocity attenuation is used to preliminarily determine whether the internal structure of the sample has been damaged and the extent of the damage. Wave velocity attenuation rate is defined as... In the formula: V is the stress wave velocity of the undamaged sample, i.e., T 入射1 The wave velocity is V', which is the stress wave velocity after the specimen is damaged by the second plastic wave S, i.e., T. 透射2 wave speed; In the formula: S is the distance from the incident measuring point to the transmission measuring point; The time it takes for the first stress wave to propagate from the incident measuring point to the transmitted measuring point, i.e., from T... 入射1 To T 透射1 Time; The time it takes for the third stress wave to propagate from the incident measurement point to the transmitted measurement point, i.e., from T... 入射2 To T 透射2 Time; Attenuation rate of wave velocity Once a set threshold is reached, the structure is deemed to have suffered damage, affecting the incident and transmitted T. 入射2 and T 透射2 These two waves are processed by wavelet transform to analyze the amplitude differences of each corresponding frequency band, thereby analyzing the internal crack situation of the sample.

2. The damage analysis method based on stress wave segmentation according to claim 1, characterized in that: Wave velocity attenuation rate If the damage is greater than or equal to 5%, the structure is considered to have suffered damage.

3. The damage analysis method based on stress wave segmentation according to claim 1, characterized in that: Using the wavelet toolbox in MATLAB to analyze the T values ​​of incident and transmitted light. 入射2 and T 透射2 These two waves are then subjected to wavelet transform.

4. The damage analysis method based on stress wave segmentation according to claim 1, characterized in that: Damage analysis of the sample is performed using a Hopkinson bar device. The gas pressure chamber is adjusted to control the bullet to impact the incident bar at a set impact velocity, thereby generating an incident stress wave. When the incident stress wave propagates along the incident bar to the sample interface, it generates reflected and transmitted waves. The signals are measured by strain gauges on the incident and transmitted bars, amplified by a Wheatstone bridge, and recorded and stored by an eight-channel digital oscilloscope.

5. The damage analysis method based on stress wave segmentation according to claim 4, characterized in that: The Hopkinson bar device includes an incident bar, a transmission bar, and a sample.

6. The damage analysis method based on stress wave segmentation according to claim 5, characterized in that: The incident rod and the transmission rod are made of 50 mm diameter steel rods with an elastic modulus of 210 GPa, the material is 48CrMoA, and the wave velocity is 5.270 km / s; the length of the incident rod is 3.0 m, and the length of the transmission rod is 1.8 m.

7. The damage analysis method based on stress wave segmentation according to claim 5, characterized in that: The sample was granite.

8. The damage analysis method based on stress wave segmentation according to claim 5, characterized in that: The first end of the incident rod is provided with a copper sheet, which serves as a shaper.

9. The damage analysis method based on stress wave segmentation according to claim 5, characterized in that: The surfaces of the sample that come into contact with the incident rod and the transmission rod are coated with petroleum jelly.

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