A method for locating cracks in underwater concrete components based on interface waves

Abstract

The present invention discloses a method for locating cracks in underwater concrete components based on interface waves, which is used to locate the crack positions on underwater concrete components, including the following steps: Step 1: constructing a distance d between the crack position and the incident position. c The calculation formula is: Based on the principle of locating and detecting surface cracks of underwater concrete components by incident S-wave and reflected S-R wave, the distance d between the crack position on the underwater concrete component and the incident position is constructed. c Calculation formula; Step 2, get the spacing d c The various constituent parameters in the calculation formula; Step 3, calculate the distance d between the crack position and the incident position c Thus, the present invention realizes non-destructive detection of surface crack location of underwater concrete components, free from the limitations of low visibility, turbid water, and structure surfaces covered by aquatic plants and suspended sediments.

Description

Technical Field

[0001] The invention relates to a nondestructive testing method for underwater concrete components, and in particular to an interface wave-based crack locating method for underwater concrete components. Background Art

[0002] Existing crack detection methods for underwater concrete components are mainly based on sonar scanning and visual inspection. However, these methods are fundamentally limited by low visibility, turbid water, and structural surfaces covered by aquatic plants and suspended sediments. Summary of the Invention

[0003] The technical purpose of this invention is to provide a method for locating cracks in underwater concrete components based on interface waves, which can provide technical support for the integrity assessment of underwater concrete structures such as dams, bridge piers, and water pipelines.

[0004] In order to achieve the above technical objectives, the present invention will adopt the following technical solutions:

[0005] A method for locating cracks in underwater concrete components based on interface waves, for locating crack positions on underwater concrete components, comprises the following steps:

[0006] Step 1: Construct the distance d between the crack position and the incident position c The calculation formula

[0007] Based on the principle of locating and detecting surface cracks of underwater concrete components by incident S waves and reflected SR waves, the distance d between the crack position on the underwater concrete component and the incident position is constructed. c The calculation formula is:

[0008] SR waves are R waves transformed from S waves reflected when they propagate from the incident position of underwater concrete components to the crack position;

[0009] Spacing d c The calculation formula is as follows:

[0010]

[0011] Where: c S represents the velocity of the S wave, c R represents the velocity of SR wave;

[0012] t1 represents the initial moment when the S wave hits the underwater concrete component;

[0013] t2 represents the time when the SR wave reaches the receiving position;

[0014] d r It represents the distance between the incident position and the receiving position on the underwater concrete component;

[0015] Step 2: Get the spacing d c The constituent parameters in the calculation formula

[0016] The specific method for obtaining the initial time t1 when the S wave hits the underwater concrete component is:

[0017] Inputting an ultrasonic pulse signal into the underwater concrete component through an incident position on the underwater concrete component; determining an initial time t1 at which the S wave enters the underwater concrete component by analyzing a waveform of the ultrasonic pulse signal, the initial time t1 being the time corresponding to the maximum peak in the waveform of the ultrasonic pulse signal;

[0018] The specific method of obtaining the time t2 when the SR wave arrives at the receiving position is:

[0019] After collecting the received wave at the receiving position of the underwater concrete component, the SR wave is identified based on the different times corresponding to the outstanding peaks in the waveform of the received wave, and the peak time of the SR wave is obtained. The time t2 when the SR wave reaches the receiving position is the peak time of the SR wave.

[0020] Step 3: Calculate the distance d between the crack position and the incident position c

[0021] According to the spacing d obtained in step 2 c The spacing d can be calculated by using the various parameters in the calculation formula c , thereby realizing the crack location detection of underwater concrete components.

[0022] As a further improvement of the above invention, in step 2, the ultrasonic pulse signal is cr Direction from water to concrete member, critical angle θ cr Calculated by the following formula:

[0023]

[0024] Where: c w represents the speed of wave propagation in water, c R Indicates the speed at which R waves propagate in concrete components.

[0025] As a further improvement of the above invention, the excitation frequency f of the ultrasonic pulse signal is:

[0026] f=0.5sin(2πf c t)[1-cos(πf c t)]

[0027] Where: f c represents the center frequency, and t represents the time series.

[0028] As a further improvement of the above invention, the wave velocity c of the S wave S 、SR wave velocity c R satisfy:

[0029] c S =1500±Δc S

[0030] c R =2200±Δc R

[0031] Where: Δc S , Δc R They are all constants, determined by the changes in parameters of different concrete materials, and their values ​​do not exceed 200.

[0032] As a further improvement of the above invention, the wave velocity c of the S wave S 、SR wave velocity c R The velocity c of the interface wave of underwater concrete components is determined by solving the characteristic value of the interface wave velocity c of underwater concrete components; the interface wave velocity c of underwater concrete components satisfies the following formula:

[0033]

[0034] Where: c L represents the velocity of longitudinal waves in solids, c T represents the velocity of shear waves in solids, c w Indicates the speed of waves in water, usually 1500m / s, H indicates the distance between the water surface and the upper surface of the component, f c represents the center frequency, ρ (w) Indicates the density of water;

[0035] There are two characteristic values ​​of the interface wave velocity c of underwater concrete components solved by formula (2), and the smaller one is the wave velocity c of the S wave. S , the other larger value is the SR wave velocity c R .

[0036] As a further improvement of the above invention, there are three outstanding peaks in the waveform diagram of the received wave, which correspond to the first to third outstanding peaks in chronological order; among them: the first outstanding peak is identified as the R wave that directly reaches the receiving position from the incident position, the second outstanding peak is identified as the S wave that directly reaches the receiving position from the incident position, and the third outstanding peak is identified as the SR wave that reaches the receiving position after being reflected from the incident position through the crack.

[0037] As a further improvement of the above invention, the wavelength of the ultrasonic pulse signal is greater than twice the maximum particle size of the bone particles in the underwater concrete component.

[0038] Based on the above technical objectives, the present invention has the following advantages over the prior art:

[0039] The present invention is based on the research results of numerical simulation of the generation, propagation and scattering of underwater concrete interface waves (see Appendix Figure 2 ), and finally the incidence of S wave and reflection of SR wave are selected to locate the surface cracks of underwater concrete components, thereby constructing the spacing d c (the distance between the crack position and the incident position on the underwater concrete component) is calculated using the calculation formula. Then, for surface crack location detection on any underwater concrete component, the initial time t1 when the S wave hits the underwater concrete component and the time t2 when the SR wave reaches the receiving position are obtained by the incidence of the S wave and the reflection of the SR wave, and the spacing d can be calculated. c , thereby achieving crack location detection of underwater concrete components. It can be seen that the present invention achieves non-destructive detection of surface crack location of underwater concrete components, free from the limitations of low visibility, turbid water, and structural surfaces covered by aquatic plants and suspended sediments. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a flow chart of the method for locating cracks in underwater concrete components based on interface waves according to the present invention.

[0041] Figure 2 It is a simulated wave field diagram that simulates the generation, propagation and scattering of interface waves when locating cracks in underwater concrete components; Figure 2 Middle: (a) is the wave field diagram of the ultrasonic pulse at t = 120 μs; (b) is the wave field diagram of the ultrasonic pulse at t = 170 μs; (c) is the wave field diagram of the ultrasonic pulse at t = 300 μs;

[0042] Figure 3 This is a simulation waveform diagram of crack location detection of underwater concrete components under different excitation frequencies; Figure 3 Middle: (a) The figure shows the simulation waveform at the excitation frequency f = 25kHz (the solid line is the simulation waveform with random aggregate added, and the dotted line is the simulation waveform without random aggregate added); (b) The figure shows the simulation waveform at the excitation frequency f = 50kHz (the solid line is the simulation waveform with random aggregate added, and the dotted line is the simulation waveform without random aggregate added); (c) The figure shows the simulation waveform at the excitation frequency f = 100kHz (the solid line is the simulation waveform with random aggregate added, and the dotted line is the simulation waveform without random aggregate added); (d) The figure shows the simulation waveform at the excitation frequency f = 200kHz (the solid line is the simulation waveform with random aggregate added, and the dotted line is the simulation waveform without random aggregate added);

[0043] Figure 4is a waveform diagram (obtained by simulation) of the incident ultrasonic pulse of the underwater concrete component crack location method based on interface waves according to the present invention;

[0044] Figure 5 is a waveform diagram (obtained by simulation) of the received wave (the distance between the receiving position and the incident position is 200 mm) of the underwater concrete component crack location method based on interface waves according to the present invention;

[0045] Figure 6 This is a waveform diagram of received waves (obtained from experiments) of a specific embodiment of the method for locating cracks in underwater concrete components based on interface waves according to the present invention. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way serves as any limitation on the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection of the present invention. Unless otherwise specified, the relative arrangement of components and steps, expressions and numerical values ​​described in these embodiments do not limit the scope of the present invention. Technologies, methods and equipment known to ordinary technicians in the relevant fields may not be discussed in detail, but where appropriate, the technologies, methods and equipment should be considered part of the specification. In all examples shown and discussed here, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of the exemplary embodiments may have different values.

[0047] like Figure 1 As shown, the method for locating cracks in underwater concrete components based on interface waves of the present invention is used to locate crack positions on underwater concrete components, and includes the following steps:

[0048] Step 1: Construct the distance d between the crack position and the incident position c The calculation formula

[0049] Step 1.1: Based on the results of numerical simulation of the generation, propagation, and scattering of interface waves, it is determined that the incidence of S waves and the reflection of SR waves are used to locate and detect surface cracks in underwater concrete components.

[0050] Attachment Figure 2The results of numerical simulation of the generation, propagation and scattering of interface waves of underwater concrete components are specifically shown. As can be seen from the figure: the ultrasonic pulse emitted by the transmitter to the underwater concrete component can be observed as R wave (R is the abbreviation of Rayleigh) and S wave (S is the abbreviation of Scholte) at the interface between water and concrete components. The wavefronts of R wave and S wave are constrained at the interface, so R wave and S wave can propagate over a long distance with low attenuation. Figure 2 As shown in (a) in the figure, the speeds of R-wave and S-wave propagation toward the crack are 2226.73m / s and 1498.56m / s respectively. The speed of R-wave is greater than that of S-wave. At the same time, longitudinal waves (L-waves) and transverse waves (T-waves) cannot be observed in concrete components, which means that L-waves and T-waves are masked by R-waves and S-waves. Figure 2 As shown in (b), when the R wave reaches the crack, the transmitted R wave is visible, but the reflected R wave is not obvious. Since crack imaging is based on reflected waves, the reflection of the R wave can be ignored in the crack location process. Figure 2 As shown in (c) of the figure, the S-wave reaches the crack. The reflected S-wave is simultaneously converted into an R-wave and an S-wave, represented by the SR-wave and SS-wave, respectively. Specifically, the SR-wave is the R-wave converted by the S-wave as it travels from its incident position on the underwater concrete component to the crack. Because the SR-wave is stronger than the SS-wave, crack location should utilize both the incident S-wave and the reflected SR-wave.

[0051] Step 1.2: Based on the principle of S-wave incidence and SR-wave reflection, the surface cracks of underwater concrete components are detected and the distance d between the crack position and the incident position is constructed. c Calculation formula for spacing d c The derivation process is:

[0052] The time Δt for the ultrasonic pulse emitted by the incident machine to propagate from the incident position on the underwater concrete component to the crack position is:

[0053]

[0054] Where: c S represents the velocity of the S wave, c Rrepresents the wave velocity of the SR wave; t1 represents the initial moment when the S wave enters the underwater concrete component (when the ultrasonic pulse enters the underwater concrete component at the incident position of the underwater concrete component, the S wave and R wave can be observed at the interface between the water and the concrete component of the underwater concrete component. Therefore, the initial moment when the S wave enters the underwater concrete component is the initial moment when the ultrasonic pulse passes through the incident position of the underwater concrete component and enters the underwater concrete component); t2 represents the moment when the SR wave reaches the receiving position of the underwater concrete component; d r Represents the distance between the incident position and the receiving position on the underwater concrete component.

[0055] According to the above expression of time Δt, the distance d between the crack position on the underwater concrete component and the incident position can be derived: c The calculation formula of spacing d c The calculation formula is as follows:

[0056]

[0057] Step 2: Get the spacing d c The constituent parameters in the calculation formula

[0058] Based on the above-mentioned formula (1), for the crack location of underwater concrete components, if the specific values ​​of each component parameter are known, the spacing d can be directly calculated. c The specific value of , that is, the distance between the crack position on the underwater concrete component and the incident position is obtained, thereby completing the positioning of the crack on the underwater concrete component.

[0059] Since the incident position (the position connected to the incident machine) and the receiving position (the position connected to the receiver) of the underwater concrete component can be marked according to the actual situation, the distance d r The specific value of can be obtained by simple measurement. The wave velocity of S wave c S 、SR wave velocity c R It can be obtained by the following formula:

[0060] c S =1500+Δc S

[0061] c R =2200+Δc R

[0062] Where: Δc S , Δc R They are all constants, and their values ​​do not exceed 100. Δc S , Δc R It is caused by the changes in parameters of different concrete materials.

[0063] In addition, the S-wave velocity c S 、SR wave velocity c R The velocity c of the interface wave of underwater concrete components is determined by solving the characteristic value of the interface wave velocity c of underwater concrete components; the interface wave velocity c of underwater concrete components satisfies the following formula:

[0064]

[0065] Where: c L represents the velocity of longitudinal waves in solids, c T represents the velocity of shear waves in solids, c w Indicates the speed of waves in water, usually 1500m / s, H indicates the distance between the water surface and the upper surface of the component, f c represents the center frequency, ρ (w) Indicates the density of water.

[0066] There are two characteristic values ​​of the interface wave velocity c of underwater concrete components solved by formula (2), and the smaller one is the wave velocity c of the S wave. S , the other larger value is the SR wave velocity c R .

[0067] In formula (2), it is assumed that the water depth H is set to 0.2m and the center frequency f c Set to 50kHz. Longitudinal wave c L The wave velocity is 4138.80m / s, and the shear wave c T The wave velocity is 2534.48m / s. The two eigenvalues ​​2308.90m / s and 1480.29m / s can be calculated. From this, we can conclude that the wave velocity c of the S wave is S is 1480.29 m / s; the wave speed of SR wave c R It is 2308.90m / s.

[0068] The specific method for obtaining the initial time t1 when the S wave impinges on the underwater concrete component is:

[0069] An ultrasonic pulse signal is input into the underwater concrete component through an incident position on the underwater concrete component; the initial time t1 when the S wave enters the underwater concrete component is determined by analyzing the waveform of the ultrasonic pulse signal. The initial time t1 is the time corresponding to the maximum peak in the waveform of the ultrasonic pulse signal.

[0070] According to Snell's law, the incident angle along the critical angle direction amplifies the generation of interface waves. Therefore, in the present invention, the ultrasonic pulse signal along the critical angle θ cr Direction from water to concrete member, critical angle θ cr Calculated by the following formula:

[0071]

[0072] Where: c w Indicates the speed of S wave propagation in water, which is 1500m / s; c R The speed of R-wave propagation in concrete components is 2250 m / s, so the critical angle is calculated to be 39.9°.

[0073] The specific method of obtaining the time t2 when the S wave reaches the crack position is:

[0074] After collecting the received waves at the receiving position of the underwater concrete component, the SR wave is identified based on the different times corresponding to the outstanding peaks in the waveform diagram of the received wave, and then the peak time of the SR wave is obtained; the time t2 when the S wave reaches the crack position is the peak time of the SR wave.

[0075] Figure 5 In the received signal, there are three prominent peaks. Based on the speed of the R wave and the S wave, combined with the distance between the incident and the receiver, the arrival time of the R wave and the S wave can be calculated, so that the first and second prominent peaks can be identified as R waves and S waves. The third prominent peak is the SR wave.

[0076] The present invention selects Figure 4 The ultrasonic pulse with the waveform shown is expressed as:

[0077] f=0.5sin(2πf c t)[1-cos(πf c t)]

[0078] Where: f c is the center frequency.

[0079] Typically, the wavelength of guided waves changes with the excitation frequency. When the wavelength is significantly larger than the aggregate size, stable diffraction occurs and the concrete is considered uniform. Otherwise, the concrete is considered non-uniform. Therefore, the excitation frequency is a key parameter for damage detection in concrete structures.

[0080] The present invention studies the effect of excitation frequency through a series of simulations. Random aggregate with a particle size of 5-20 mm is added to the finite element model. The excitation frequency is set to 25, 50, 100, and 200 kHz, corresponding to 4, 2, 1, and 0.5 times the wavelength of the aggregate particle size, respectively. The waveforms under 25, 50, 100, and 200 kHz excitation are as follows: Figure 3 When the excitation wavelength is 4 and 2 times the aggregate particle size, R-waves and S-waves can be clearly observed, and the wave velocities are consistent with the theoretical values, proving that the concrete can be considered homogeneous at this time. However, when the excitation wavelength is 1 and 0.5 times the aggregate particle size, R-waves cannot be clearly observed, proving that the concrete cannot be considered homogeneous at this time.

[0081] Step 3: Calculate the distance d between the crack position and the incident position c

[0082] According to the distance d obtained in step 2 r , S-wave velocity c S 、SR wave velocity c R , the initial time t1 when the S wave hits the underwater concrete component, the time t2 when the SR wave reaches the receiving position, and the distance d constructed c The calculation formula can be used to calculate the spacing d c , thereby realizing the crack location detection of underwater concrete components.

[0083] Example

[0084] In order to verify the effectiveness of the crack detection method, a finite element model was established. The exciter (transmitter) is located at 0.4m, the receiver (receiver) is located at 0.6m, and the crack is located at 0.7m. The distance between the crack and the exciter is 300mm. The detection signal is as follows Figure 6 shown.

[0085] Through the above detection method, it was found that the crack was detected at a distance of 296 mm from the transmitter (actually 300 mm). This shows that the detected position is close to the actual position, and the relative error is only 1.3%.

Claims

1. A method for locating cracks in underwater concrete components based on interface waves, which is used to locate crack positions on underwater concrete components, characterized in that: The steps include: Step 1: Construct the distance d between the crack position and the incident position c The calculation formula Based on the principle of locating and detecting surface cracks of underwater concrete components by incident S waves and reflected SR waves, the distance d between the crack position on the underwater concrete component and the incident position is constructed. c The calculation formula is: SR waves are R waves transformed from S waves reflected when they propagate from the incident position of underwater concrete components to the crack position; Spacing d c The calculation formula is as follows: Where: c S represents the velocity of the S wave, c R represents the velocity of SR wave; t1 represents the initial moment when the S wave hits the underwater concrete component; t2 represents the time when the SR wave reaches the receiving position; d r It represents the distance between the incident position and the receiving position on the underwater concrete component; Step 2: Get the spacing d c The various components in the calculation formula The specific method for obtaining the initial time t1 when the S wave hits the underwater concrete component is: Inputting an ultrasonic pulse signal into the underwater concrete component through an incident position on the underwater concrete component; determining an initial time t1 at which the S wave enters the underwater concrete component by analyzing a waveform of the ultrasonic pulse signal, the initial time t1 being the time corresponding to the maximum peak in the waveform of the ultrasonic pulse signal; The specific method of obtaining the time t2 when the SR wave arrives at the receiving position is: After collecting the received wave at the receiving position of the underwater concrete component, the SR wave is identified based on the different times corresponding to the outstanding peaks in the waveform of the received wave, and the peak time of the SR wave is obtained. The time t2 when the SR wave reaches the receiving position is the peak time of the SR wave. Step 3: Calculate the distance d between the crack position and the incident position c According to the spacing d obtained in step 2 c The spacing d can be calculated by using the various parameters in the calculation formula c , thereby realizing the crack location detection of underwater concrete components.

2. The method for locating cracks in underwater concrete components based on interface waves according to claim 1, characterized in that: In step 2, the ultrasonic pulse signal is transmitted along the critical angle θ cr Direction from water to concrete member, critical angle θ cr Calculated by the following formula: Where: c w represents the speed of wave propagation in water, c R Indicates the speed at which R waves propagate in concrete components.

3. The method for locating cracks in underwater concrete components based on interface waves according to claim 1, characterized in that: The excitation frequency f of the ultrasonic pulse signal is: f=0.5sin(2πf c t)[1-cos(πf c t)] Where: f c represents the center frequency, and t represents the time series.

4. The method for locating cracks in underwater concrete components based on interface waves according to claim 1, characterized in that: The speed of S waves c S 、SR wave velocity c R satisfy: c R =2200±Δc R Where: Δc S , Δc R They are all constants, determined by the changes in parameters of different concrete materials, and their values ​​do not exceed 200.

5. The method for locating cracks in underwater concrete components based on interface waves according to claim 1, characterized in that: The speed of S waves c S 、SR wave velocity c R The velocity c of the interface wave of underwater concrete components is determined by solving the characteristic value of the interface wave velocity c of underwater concrete components; the interface wave velocity c of underwater concrete components satisfies the following formula: Where: c L represents the velocity of longitudinal waves in solids, c T represents the velocity of shear waves in solids, c w Indicates the speed of waves in water, usually 1500m / s, H indicates the distance between the water surface and the upper surface of the component, f c represents the center frequency, ρ (w) The density of water is represented by the equation (2). There are two characteristic values ​​of the interface wave velocity c of underwater concrete components, and the smaller one is the wave velocity c of the S wave. S , the other larger value is the SR wave velocity c R .

6. The method for locating cracks in underwater concrete components based on interface waves according to claim 1, characterized in that: There are three outstanding peaks in the waveform of the received wave, which correspond to the first to third outstanding peaks in chronological order; among them: the first outstanding peak is identified as the R wave that directly reaches the receiving position from the incident position, the second outstanding peak is identified as the S wave that directly reaches the receiving position from the incident position, and the third outstanding peak is identified as the SR wave that reaches the receiving position after being reflected from the crack from the incident position.

7. The method for locating cracks in underwater concrete components based on interface waves according to claim 1, characterized in that: The wavelength of the ultrasonic pulse signal is greater than twice the maximum particle size of bone particles in the underwater concrete component.

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