CN101285679A - Method and device for measuring crack depth - Google Patents

Abstract

The invention relates to a crack depth measuring method and device. The method includes: a. measuring the sound velocity v in the measured solid medium; b. placing the transmitting and receiving transducers on two sides symmetrical to the crack, the distance between the transmitting and receiving transducers being l ₁ , and reading the sound wave propagation At time t ₁ , calculate the fracture depth h ₁ by the following formula: (see formula); c, set the distance between the transmitting and receiving transducers as l ₂ , and l ₂ is 0.1h ₁ ≤ _{l 2} ≤ 10h ₁ or 30mm ≤ l ₂ ≤500mm; read the acoustic time value t ₂ , and calculate the crack depth value h ₂ ; the average value of d ^h1 and h ₂  is the crack depth. This method can obtain high-precision measurement results with a small number of measurement points. The present invention also provides a crack depth tester comprising: the main control system is connected to the transmitting transducer through a high-voltage transmitting module, and the high-voltage transmitting module enables the transmitting transducer to generate an acoustic signal; the receiving transducer passes the received signal through the signal The receiving conditioning module performs processing, and then the analog-to-digital conversion module converts it into a digital signal and transmits it to the main control system; the main control system processes the received digital signal and directly calculates the crack depth.

Description

Method and device for measuring crack depth

technical field

The invention relates to the technical field of acoustic wave detection, in particular to a method and device for measuring the depth of cracks in solid media by means of an acoustic wave diffraction method.

Background technique

Acoustic diffraction is often used in production and life to measure the depth of cracks on solid surfaces, especially for the detection of crack depths in concrete that widely exist in construction projects. Cracks are the most common defect in concrete engineering. The damage of reinforced concrete and masonry structures in construction engineering is often related to the development of cracks. The existence of cracks will reduce the bearing capacity of engineering structures and affect the impermeability of structures. , leading to the infiltration of moisture and harmful substances, inducing corrosion of steel bars, thus affecting safety.

At present, the detection of the depth of non-penetrating cracks in concrete mainly uses the acoustic wave diffraction method, as shown in Figure 1. There are two specific testing methods:

The first is the "diffraction sound time calculation method". This method is adopted by the British Standard BS-4408 and the China Engineering Construction Standardization Association standard "Technical Regulations for Detection of Concrete Defects by Ultrasonic Method" (CECS 21:2000, hereinafter referred to as "Defect Detection Regulations"). The specific measurement steps are:

1. On the concrete surface without cracks, when measuring the distance between the transmitting transducer and the receiving transducer and propagating sound at multiple points, use the linear regression method to obtain the regression coefficient of the linear relationship between sound time and distance measurement, that is, the sound velocity v of the concrete

2. Place the transmitting and receiving transducers on both sides of the symmetry of the crack, _and read the sound time values when the distance between the two transducers is 100mm, 150mm, 200mm, 250mm, ... t _i , as shown in Fig. 2, the formula for calculating the crack depth is:

${\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\sqrt{{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; v</span>}}{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}$ ${\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}$

In the formula: h _i - crack depth calculated at the i-th point (mm)

l _i - the distance between the two transducers at point i (mm)

t _i - sound wave propagation time at point i (μs)

m _h - the average value of crack depth at measuring points at different intervals

n-number of measuring points

3. Determine the fracture depth: compare the interval value l _i corresponding to each interval measurement point with the average fracture depth m _h , if the interval l _i is less than m _h or greater than 3m _h , this group of data should be eliminated, and the remaining h _i should be taken The average value is taken as the crack depth.

The second is the "first wave phase inversion method". This method has also been adopted by the "Defect Measurement Regulations". The specific test steps and crack depth calculation formula of this method are the same as the "diffraction acoustic time calculation method", but the selection method for the crack depth values at different spacings is different. The specific measurement steps are: observe the change of the phase of the first wave during the test of the measuring points at different intervals. When the first wave anti-phase is found at a certain spacing measuring point, the average value of the fracture depth measurements at this spacing measuring point and two adjacent spacing measuring points is used as the fracture depth value. As shown in Figure 3a, T1, R1 and T2, R2 are two adjacent transmitting and receiving measuring points respectively. In the waveform diagram of T1-R1, the phase of the first wave is upward, see Figure 3b. In the waveform diagram of T2-R2, the phase of the first wave becomes downward, as shown in Figure 3c, then T2-R2 is the measuring point where the phase of the first wave appears reversed.

In addition, using the diffraction method to detect the crack depth calculation formula requires certain physical conditions to be met, that is, the diffracted sound wave should travel around the end of the crack in a straight line, and the sound ray will not deviate due to defects in the steel bars or concrete adjacent to the crack, and the propagation should also be guaranteed. Consistency of sound velocity over the range of the path.

A Chinese utility model patent related to the present invention: "Concrete Crack Tester" (patent number: ZL200420016797.6, hereinafter referred to as the comparative patent), which uses multiple transmitting and receiving transducers to transmit and receive multiple acoustic signals in sequence, The depth of the measured crack is directly calculated and measured by using the phase change of the measuring point. It adopts a method similar to the "first wave phase inversion method" in the "Deficiency Measurement Regulations", that is, find the position of the measuring point where the first wave is reversed in multiple acoustic signals, and use the two measuring points before and after the measuring point Twice the average spacing of the crack depth.

The testing methods recommended in the "Deficiency Test Procedure" and methods similar to the "Deficiency Test Procedure" have the following problems and defects:

(1) In the diffraction-acoustic time calculation method, due to changes in physical conditions and the influence of various test errors, there are differences in the calculated values of fracture depths at different intervals of measurement points, and the selection of wrong data is a difficult problem to judge and deal with . The calculation method of diffraction sound time used in the "Deficiency Measurement Regulations" selects data based on the ratio l _i /m _h of the distance between measuring points l _i and the average fracture depth m _h , and the specified ratio l _i /m _h should be 1 to 3. Data outside this range is discarded. Therefore, when the fracture depth is shallow, the range of test intervals that can be used is very small, and it is difficult to arrange measuring points.

For example, when the average slit depth m _h =20mm, the distance l _i between transducers is only allowed to be 20mm-60mm; the average slit depth m _h =30mm, the distance l _i is only allowed to be 30mm-90mm. In addition, before the fracture depth is unknown, if the spacing 100mm, 150mm, 200mm, 250mm, ... recommended in the "Rules for Gap Measurement" is used for testing, most or even all of the test data may be due to the spacing l _i and the average fracture depth m If the ratio of _h is greater than 3, it will be rejected; on the other hand, when the fracture depth is relatively deep, the test should be carried out _according to the spacing recommended in the "Rules for Defect Measurement", and many test data will be due to the ratio of the spacing l _i to the average fracture depth If it is less than 1, it will be eliminated. For example, when the average seam depth m _h =300mm, the spacing l _i is allowed to be 300mm-900mm, and the spacing data below 300mm will be eliminated.

The problem brought about by the above situation is: the elimination of too much test data will inevitably mean too many invalid tests.

(2) When the fracture depth is deep, the distance between the transducers required by the "Rules for Gap Measurement" is large, so that the signal bypassing the fracture and propagating to the receiving transducer is already very weak, or even loses waves, resulting in difficulty in reading the sound time or Unable to interpret, resulting in large errors. For example, when the crack depth h _i =300mm, the transducer spacing l _i should be 300mm-900mm, and the propagation distance of the diffracted wave bypassing the end of the crack in the actual concrete will reach 670-1080mm.

(3) In the method for determining the fracture depth suggested by the "Rules for Gap Measurement", there is no requirement for the number and discreteness of the fracture depth data retained for averaging, so two situations may occur: the first is that only There is only one data left, and the second is that the data used for averaging is too discrete. In both cases, data with gross errors cannot be found and eliminated. Obviously, the method of averaging the data containing gross errors or the data with too large dispersion cannot reduce the test error.

(4) The phase inversion method of the first wave requires observing the change of the phase of the first wave during the test. Since it is unpredictable when the measuring point of the first wave inversion will appear during the test, it will inevitably make the on-site test work difficult. It is very cumbersome and requires higher testing experience for testers. In addition, a large number of experiments have shown that when the first wave just appears out of phase, the amplitude of the first wave will be significantly reduced, which will directly affect the test accuracy of the acoustic time. If you do not observe carefully, you may even lose the wave. The test accuracy drops significantly. Figure 4a, Figure 4b, and Figure 4c are the sampling waveforms before and after the first wave inversion. The above experiments use a fixed amplification system, so the waveform amplitudes in the three figures can reflect the magnitude of the signal amplitude. In Figure 4a, the first wave is upward, which is the waveform before phase inversion, and the amplitude of the first wave reaches above the full scale (that is, the peak value of the first wave exceeds the screen); Very small; in Figure 4c, the first wave is downward, which is the waveform after phase inversion, and the amplitude of the first wave gradually increases.

(5) At present, the acoustic wave diffraction method is used to detect the fracture depth according to the "Defect Measurement Regulations". The on-site test work is cumbersome, and it is necessary to draw the position of the measuring point and measure the distance. Generally, at least 4 to 5 measuring points are arranged to obtain multiple fracture depths. value h _i to obtain the average fracture depth m _h , and then according to the ratio l _i /m _k should be 1 to 3, the data obtained at different intervals l _i are screened and eliminated. During the test, it is necessary to interpret the recorded sound, observe the waveform change, and screen the data, etc., and the test instrument used is a general-purpose ultrasonic instrument, which is expensive. The test personnel also need to have basic knowledge of ultrasonic waves, test instrument usage methods, and data processing. method training.

Contents of the invention

Because the existing methods for detecting the depth of cracks in solid media have defects such as large errors, long time consumption, high technical requirements, and complicated data elimination steps, it is necessary to find a new method that is simpler and more accurate.

From the literature "Electromagnetic and Accoustic scattering by simple shapes" (from "Electromagnetic and Accoustic scattering by simple shapes" Edited by J.J.BowmanT.B.A.Senior P.L.E.Uslenghi, Radiation laboratory, The University of Michigan, USA, Authors J.S.Asvestas D.l.Sengupta T.B.A.Bowman Senior etc.), the approximate formula of the diffraction field for the diffraction (diffraction) generated by the acoustic wave wedge can be obtained:

In the formula (see Figure 5):

$v=\frac{2\mathrm{\&pi;}-2\mathrm{\&Omega;}}{\mathrm{\&pi;}},$ 2Ω is the top angle of the wedge

-衍射角

- Diffraction angle

k=2π/λ λ is the wavelength

ρ, ρ ₀ are the distances from the transmitting and receiving points to the top of the wedge,

R ₁ = ρ ₀ + ρ = 2ρ ₀ is the propagation distance between the transmitting and receiving points

Applying this approximate formula to the diffraction method to detect the depth of concrete cracks, and further considering the attenuation of the sound wave, the directivity of the transducer and the complex frequency characteristics of the pulse wave, the mathematical approximate expression of the sound wave diffraction field suitable for crack testing is derived:

In the formula, Q is the directivity factor

A is the attenuation factor

Σ is the summation of the single-frequency diffracted waves that make up the complex-frequency wave

The modulus (absV ^d ) of it is the amplitude of the diffraction field

与间距l_i和缝深h_i的比值l_i/h_i是直接相关的，

显然，l_i/h_i越小，衍射角

越小。例如l_i/h_i为0.5时，衍射角为14°；l_i/h_i为1.5时，衍射角为37°；l_i/h_i为2.5时，衍射角为51°。According to the requirements of the physical conditions of the crack depth calculation formula, when determining the appropriate transducer spacing, that is, the appropriate diffraction angle, it is obvious that the smaller the range of the diffraction field, the better, that is, the smaller the diffraction angle, the better. Because the smaller diffraction angle involves a smaller sound field range, it is easier to avoid sound ray deviation caused by adjacent steel bars or other defects, and it is also easier to ensure the consistency of sound velocity. But can the amplitude of the small-angle diffracted wave guarantee the test accuracy? Therefore, the crux of the problem comes down to the need to analyze the most suitable diffraction angle from the expression of the diffraction sound field, so that it can not only ensure sufficient amplitude, but also obtain a diffraction angle as small as possible. Diffraction angle

It is directly related to the ratio l _i /h _i of spacing l _i and fracture depth h _i ,

Obviously, the smaller l _i /h _i is, the diffraction angle

smaller. For example, when l _i /h _i is 0.5, the diffraction angle is 14°; when l _i /h _i is 1.5, the diffraction angle is 37°; when l _i /h _i is 2.5, the diffraction angle is 51°.

的关系图的一个例子(缝深为10cm，主频为50kHz的复频波)，图中横轴为衍射角，纵轴为对应的衍射场幅度。其他缝深的幅度A与衍射角

的关系图与此类似，只是裂缝越深，图中幅度峰值所对应的衍射角越小，纵轴幅度的数量级越小。Figure 6 shows the amplitude A and diffraction angle of the crack detection acoustic diffraction field

An example of the relationship diagram of (slot depth is 10cm, complex frequency wave with main frequency 50kHz), the horizontal axis in the figure is the diffraction angle, and the vertical axis is the corresponding diffraction field amplitude. Amplitude A and diffraction angle of other fracture depths

The relationship diagram of is similar to this, except that the deeper the crack, the smaller the diffraction angle corresponding to the amplitude peak in the figure, and the smaller the magnitude of the vertical axis.

According to the relationship diagram of sound field amplitude and diffraction angle and crack test results, the following qualitative conclusions can be drawn:

(1) Diffraction waves can be generated within a small diffraction angle. Experiments show that when the diffraction angle is 10° (ratio l _i /h _i of spacing l _i to fracture depth h _i = 0.35), a relatively ideal amplitude can still be obtained. For example, in the waveform shown in Figure 7, the slot depth is 316mm, the transducer spacing is 111mm, the corresponding l _i /h _i =0.35, the diffraction angle is 10°, and the amplitude of the first wave is sufficient to meet the interpretation requirements of acoustic time.

(2) For shallow fractures, the propagation path is short and the attenuation is small, so a strong amplitude can be obtained in a wide range of diffraction angles, that is, the ratio of the spacing l _i to the fracture depth h _i for testing is l _i /h The range of _i is relatively large, which can reach more than 5 (for example, the depth of fracture is 23mm, the measurement interval is 120mm, l _i /h _i is 5.2, and the waveform amplitude is ideal); for deep fractures, the propagation sound path increases, and the amplitude decreases obviously, l _i The larger the / _hi , the larger the sound path and the smaller the amplitude, so the test must be carried out within the diffraction angle range corresponding to the larger amplitude, otherwise the amplitude of the received signal cannot be guaranteed, which will affect the test accuracy of the sound wave travel time, so the deeper the crack , the smaller the ratio range of l _i /h _i available for testing.

(3) The deeper the crack is, the more the energy distribution represented by the amplitude curve of the relationship between the sound field amplitude and the diffraction angle shifts to the direction of the smaller diffraction angle, indicating that for deeper cracks, it is more suitable to test with a small diffraction angle.

In the case of the support of the mathematical theory of the above-mentioned acoustic diffraction field, the inventor has discovered a new method for measuring the depth of cracks in solid media through a large number of experiments and researches. The method includes the following steps:

Step a: measuring the sound velocity v in the measured solid medium;

Step b: first measuring point measurement,

Place the transmitting and receiving transducers on both sides of the symmetry of the crack, the distance between the transmitting and receiving transducers is l ₁ , read the acoustic time value t ₁ , and calculate the crack depth by the following formula:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="h"\; filenames="A20081011464800221.png"\; state="\{\{state\}\}">h</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="l"\; filenames="A20081011464800221.png"\; state="\{\{state\}\}">l</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\sqrt{{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="t"\; filenames="A20081011464800221.png"\; state="\{\{state\}\}">t</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; v</span>}}{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>$

Where: _h1 is the fracture depth calculated at the first measuring point, _l1 is the distance between the transducers at the first measuring point, and _t1 is the sound wave propagation time at the first measuring point;

Step c: second measuring point measurement,

Set the distance between the transmitting and receiving transducers as l ₂ , and the range of l ₂ is: 0.1h ₁ ≤ l ₂ ≤ 10h ₁ or 30mm ≤ _{l 2} ≤ 500mm; other conditions are the same as those measured at the first measuring point, read Acoustic time value t ₂ ; use the following formula to calculate the crack depth h ₂ at the second measuring point;

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="h"\; filenames="A20081011464800281.png"\; state="\{\{state\}\}">h</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="l"\; filenames="A20081011464800281.png"\; state="\{\{state\}\}">l</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\sqrt{{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="t"\; filenames="A20081011464800281.png"\; state="\{\{state\}\}">t</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; v</span>}}{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}$

Where: _h2 is the crack depth value calculated at the second measuring point, _l2 is the distance between the two transducers at the second measuring point, and _t2 is the sound wave propagation time at the second measuring point;

Step d: Calculate the average of _h1 and _h2 $\stackrel{\&OverBar;}{h}=\frac{1}{2}({\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="A20081011464800221.png"\; state="\{\{state\}\}">h</figure-callout>}}_1+h_2),$ h is the crack depth.

Compared with other measurement methods in the prior art, the above method can greatly reduce the measurement steps, without arranging multiple measurement points, calculating the average value m _h of multiple fracture depth values h _i , and then according to The range of the ratio l _i /m _k is used to filter and eliminate the data; there is no need to observe the phase reversal of the first wave as in the phase reversal method of the first wave. The method of the present invention only needs to take the interval value l ₁ within a certain range, calculate the fracture depth h ₁ , then take the interval value l ₂ within the range related to h ₁ , and then calculate the fracture depth h ₂ , then h ₁ and h The average value of ₂ is the fracture depth, which avoids the steps of data screening and elimination, and does not need to observe the first wave inversion. Since the method uses few measuring points to obtain high-precision measuring results and has a large value range of measuring points, the measuring speed is obviously accelerated, the cost is reduced, and it is more conducive to the implementation of measurement on the construction site.

Further, in the above step d, the discrete Δ=|h ₁ -h ₂ | can also be continuously calculated. If the discrete value is smaller than a certain limit value Δ _x , h is the fracture depth; otherwise, add another measuring point, Until the discrete value between the depth value of this measuring point and the depth value of any other measuring point before is less than the limit value _Δx , the average value of the depth values of the two measuring points to which this discrete value belongs is taken as the fracture depth.

Further, in the step mentioned in the preceding paragraph, the limit value _Δx of the discrete value is 5mm-150mm or 30%×h.

Further, in the step mentioned in the preceding paragraph, the limit value _Δx of the discrete value is:

When h<30mm, _Δx is 9mm; when h=30mm, _Δx is 9mm or 30%×h; when 30mm<h<300mm, _Δx is 30%×h; when h=300mm , Δ _x is taken as 90mm or 30%×h; when h>300mm, _Δx is taken as 90mm.

Further, in step b, the range of l ₁ is 30mm≤l _1≤500mm .

Further, in the step mentioned in the preceding paragraph, the range of l ₁ is 50mm≤l _1≤250mm .

Further, in the step mentioned in the preceding paragraph, the range of l ₁ is 80mm≤l _1≤150mm .

Further, in the step mentioned in the preceding paragraph, the l ₁ may be 80mm or 100mm or 110mm or 120mm or 130mm.

Further, in step a, the method for measuring the sound velocity v in the measured solid medium is to fix the transmitting transducer and the receiving transducer at a certain distance l in the seamless zone, measure the time t of propagating sound, and calculate Concrete sound velocity v = l/t.

Further, in the step mentioned in the preceding paragraph, the distance l is: 50mm-300mm.

Further, in the step mentioned in the preceding paragraph, the distance l is 200 mm.

Further, in step c,

When h ₁ ≤ 50mm, l ₂ is 0.6 to 8 times of h ₁ , or 30mm ≤ _{l 2} ≤ 200mm;

When h ₁ >50 mm, l ₂ is 0.1 to 5 times of h ₁ , or 50 mm≤l ₂ ≤400 mm.

Further, in the step mentioned in the preceding paragraph, when h ₁ ≤ 50 mm, l ₂ =50 mm; when h ₁ >50 mm, l ₂ =150 mm.

On the basis of the test method of the present invention, the present invention also proposes a crack depth tester, including a main control system, a transmitting transducer, a receiving transducer, and a power module; Connected with the transmitting transducer, the high-voltage transmitting module causes the transmitting transducer to generate an acoustic signal by applying high-voltage pulses; the receiving transducer amplifies and filters the received acoustic signal through the signal receiving and conditioning module, and then the The analog-to-digital conversion module converts digital signals to the main control system; the main control system processes the received digital signals and directly calculates the crack depth; the main control system interacts with users through the man-machine interface module.

The crack depth tester with the above structure can be measured by the method of the present invention, and the measurement result can be directly obtained, that is, the crack depth value can be directly obtained through the instrument on site. It is not necessary to use a general-purpose ultrasonic instrument for measurement as stipulated in the "Deficiency Measurement Regulations", and it is necessary to manually interpret and record the test parameters on site (that is, it is necessary to manually observe the phase changes of the measurement points on the spot and find the measurement points with the first wave reversed phase) location), and there is no need for later manual calculation or call analysis software for data processing. Compared with the general ultrasonic instrument, the crack depth tester in the present invention has a simpler structure and significantly lower equipment cost. Compared with the comparative patent, the fracture depth tester with the above structure has a simpler structure, can only use a pair of transmitting and receiving transducers, and can directly obtain the fracture depth value, the equipment cost is significantly reduced, and the operation is easier. Using the crack depth tester of the present invention, testers can quickly master and use the device without knowing the basic knowledge of ultrasonic waves, and without being trained in complicated test instrument usage methods and data processing methods.

Further, the calculation formula of the crack depth adopted by the main control system is as follows:

$\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="l"\; filenames="A20081011464800281.png"\; state="\{\{state\}\}">l</figure-callout></span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\sqrt{{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; v</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>$

Among them: h is the crack depth value, l is the distance between two transducers, t is the sound wave propagation time, v is the sound velocity in the measured solid medium.

Further, the high-voltage excitation circuit in the high-voltage transmitting module is a single-shot high-voltage excitation circuit, and the single-shot high-voltage excitation circuit enables the transmitting transducer to generate a single-shot pulse sound wave signal.

Further, the signal receiving and conditioning module adopts a fixed gain amplifier.

Further, the signal receiving and conditioning module adopts a high-gain amplifier with an amplification factor higher than 600 times.

Further, the signal receiving and conditioning module adopts a high-gain amplifier with an amplification factor of 1000 times.

Further, the main control system is composed of a main control CPU module and a logic control module; the main control CPU module is electrically connected with the logic control module, the human-machine interface module, and the power management module respectively, and is used to realize the connection between each functional module. scheduling; the main control CPU module is electrically connected to the high-voltage transmitting module through the logic control module; the analog-to-digital conversion module is electrically connected to the main control CPU module through the logic control module.

Further, the main control system performs data transmission between the data communication module and the external device.

Further, the crack depth tester also includes at least one transducer bracket, and at least one pair of transmitting transducers and receiving transducers are respectively fixed on both sides of the bracket, and can be moved along the sides of the transducer bracket respectively. Slide rail moves.

Further, a scale mark is provided on the transducer bracket along the direction of the slide rail.

Further, a central mark is provided on the transducer bracket.

Further, the scale marks on the transducer bracket are composed of pairs of marking lines, and each pair of scale marking lines is symmetrically distributed on both sides of the central mark.

Further, there are four pairs of scale marking lines, the distances between each pair of scale markings are 50mm, 100mm, 150mm, and 200mm respectively, and marking values are marked at corresponding positions.

Further, the transducer bracket is provided with a positioning device, and the positioning device can fix the transducer on the slide rail.

Further, the transducer bracket is provided with a positioning device, and the positioning device can fix the transducer at the scale mark.

Further, the center mark is a plexiglass plate marked with cross marks, and a small hole is arranged in the center of the cross marks.

Description of drawings

Fig. 1 is a schematic diagram of fracture depth testing using sound waves.

Fig. 2 is a schematic diagram of fracture depth measurement using the diffraction acoustic time calculation method.

Fig. 3a is a schematic diagram of the first-wave phase inversion method for fracture depth testing.

Figure 3b shows the waveform of T1-R1.

Figure 3c is the T2-R2 waveform.

Figure 4a is the waveform before the first wave inversion.

Figure 4b is the first waveform when the phase reversal begins.

Figure 4c is the waveform after the first wave inversion.

Figure 5 is a schematic diagram of the acoustic diffraction field.

Figure 6 shows the amplitude A and diffraction angle of the acoustic diffraction field during crack detection relationship diagram.

Figure 7 is a waveform diagram when the diffraction angle is 10°.

Fig. 8 is a flow chart of measuring the depth of a fracture using the method of the present invention.

Fig. 9 is a schematic diagram of the principle of the crack tester of the present invention

Fig. 10 is a schematic structural view of the crack tester of the present invention.

Fig. 11a is a schematic diagram of a single high voltage excitation circuit of the present invention.

Figure 11b is a single pulse signal waveform.

Fig. 12 is a schematic diagram of a fixed large gain amplifier circuit of the present invention.

Fig. 13 is a flowchart of the operation of the crack depth tester of the present invention.

Fig. 14a is a schematic diagram of the transducer bracket of the present invention.

Fig. 14b is a schematic diagram of the transducer bracket of the present invention.

Detailed ways

In order for those skilled in the art to further understand the features and technical contents of the present invention, please refer to the following detailed description and accompanying drawings of the present invention. The accompanying drawings are provided for reference and illustration only, and are not intended to limit the present invention.

Embodiments of the present invention will be described below in conjunction with the accompanying drawings.

Fig. 8 is an embodiment of the measuring method of the present invention. Place the transmitting transducer and the receiving transducer on the surface of the measured solid, the distance l between the two transducers is fixed at 200mm, measure the sound propagation time t, and calculate the sound velocity v=l/t in the measured solid medium, and then Follow the steps shown in Figure 8.

Step 101: Place the transmitting transducer and the receiving transducer symmetrically on both sides of the crack, the distance l ₁ between the two transducers is 100 mm, and measure. According to the distance l ₁ , read the acoustic time value t ₁ , The fracture depth h ₁ is obtained by the following formula:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="h"\; filenames="A20081011464800221.png"\; state="\{\{state\}\}">h</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="l"\; filenames="A20081011464800221.png"\; state="\{\{state\}\}">l</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\sqrt{{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="t"\; filenames="A20081011464800221.png"\; state="\{\{state\}\}">t</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; v</span>}}{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}$

If h ₁ ≤50mm, turn to step 201, and if h ₁ >50mm, turn to step 202;

Step 201: Select another test point, the distance between the two transducers is l ₂ =50 mm, and measure, and obtain the crack depth h ₂ and the average value of h ₁ and h ₂ respectively according to the following formula:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="h"\; filenames="A20081011464800281.png"\; state="\{\{state\}\}">h</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="l"\; filenames="A20081011464800281.png"\; state="\{\{state\}\}">l</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\sqrt{{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="t"\; filenames="A20081011464800281.png"\; state="\{\{state\}\}">t</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; v</span>}}{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}$ $\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="h"\; filenames="A20081011464800221.png"\; state="\{\{state\}\}">h</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>$

Then turn to step 301;

Step 202: Select another test point, the distance between the two transducers is l ₂ =150mm, conduct a test, obtain the crack depth h ₂ and the average value h of h ₁ and h ₂ respectively according to the formula in step 201, and then turn to step 302 ;

Step 301: Calculate the dispersion Δ=|h ₁ −h ₂ | of the crack depth values at two test points, and check whether the dispersion is smaller than the limit value Δ _x . When h<30mm, _Δx is 9mm; when h=30mm, _Δx is 9mm or 30%×h; when 30mm<h<300mm, _Δx is 30%×h; when h=300mm , Δ _x is taken as 90mm or 30%×h; when h>300mm, _Δx is taken as 90mm. If it is less than the limit value, the calculated h is the crack depth; otherwise, go to step 401 .

Step 302: According to the formula and value range in step 301, calculate the discrete value Δ of the crack depth values at the two test points and check whether the obtained discrete value is less than the limit value Δ _x , if less than the average value h is the crack depth, otherwise turn to Step 402;

Step 401: Select another test point, the distance between the two transducers is l ₃ , which is 0.6 to 8 times of h ₁ , or 30mm≤l ₂ ≤200mm, and conduct the test, and obtain the crack depth h ₃ and any Average h of two fracture depth values:

${\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\sqrt{{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; v</span>}}{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>$ $\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span>$

Wherein, h _i , h _j are the crack depths of the i-th and j-th test points respectively, and i≠j, and then turn to step 501;

Step 402: Select another test point with a distance of l ₃ , which is 0.1 to 5 times that of h ₁ , or 50mm≤l ₂ ≤400mm, and conduct the test. According to the two formulas in step 401, obtain the crack depth h ₃ and any The average value h of the two crack depth values, then turn to step 502;

Step 501: Calculating discrete Δ=|h _i −h _j | of crack depth values at any two test points, where hi _and h _j are the crack depths of the i-th and j-th test points respectively, and i≠j. According to the limit value _Δx in step 301, check whether each dispersion obtained is less than the limit value _Δx , if it is less than the limit value, the two fracture depth values whose dispersion is less than the limit value, take the average value to be the crack depth. Otherwise, repeat step 401 until the obtained discrete value is less than the limit value, and take the average value of the two crack depth values whose dispersion is smaller than the limit value as the crack depth;

Step 502: According to the discrete calculation formula in step 501, obtain the discrete value Δ of the crack depth value at any two test points, and check whether the obtained discrete value is less than the limited value Δ _x according to the limited value Δ _x in step 301, if it is smaller, the discrete value is smaller than the limited value The average value of the two crack depth values is the crack depth; otherwise, repeat step 402 until the discrete value obtained is less than the limit value, and the average value of the two crack depth values that are less than the limit value is the crack depth.

When implementing the method of the present invention, the above-mentioned steps can also be adjusted and changed. The difference from the embodiment described in FIG. value _Δx , no longer repeat step 401 (or 402), but re-select a new measuring point, and then repeat the above steps 101 to 502, until the discrete value obtained is less than the limit value, take the discrete value less than the limit The average value of the two crack depth values is the crack depth.

When implementing the method of the present invention, the above-mentioned steps can also be adjusted and changed. The difference with the embodiment described in FIG. According to the formula in step 501, the discrete values of any two measured values are calculated and compared, the two fracture depth values with the smallest discrete values obtained are selected, and the average value thereof is taken as the fracture depth.

When implementing the method of the present invention, the above-mentioned steps can also be adjusted and changed. The difference from the embodiment described in FIG. Depths h ₁ , h ₂ , h ₃ . . . are averaged and used as the depth of the crack.

When implementing the method of the present invention, the above-mentioned steps can also be adjusted and changed. The difference from the embodiment described in FIG. The average value is taken as the depth of the crack.

When implementing the method of the present invention to test the sound velocity of concrete, the distance between test points can be 50 mm to 300 mm. When testing the crack depth, in step 101, the distance _l1 of the test points can be selected within the range of _{30mm≤l1≤500mm} , and the commonly used selection range is _{50mm≤l1≤250mm} or _{80mm≤l1≤150mm} ; in step 201, The distance l ₂ of the test points can be selected from 0.6 to 8 times of h ₁ , or 30mm≤l ₂ ≤200mm. In step 202, the distance l ₂ of the test points can be selected from 0.1 to 5 times of h ₁ , or 50 mm≤l ₂ ≤400 mm. The limit value _Δx of the discrete value may be 5mm˜150mm, or 30%×h.

Fig. 9 is a schematic diagram of the principle of the crack tester of the present invention. The test system consists of a crack depth tester host 1 , a transmitting transducer 2 and a receiving transducer 3 . The main control system 1 applies high-voltage pulses to the transmitting transducer 2 through the high-voltage excitation circuit of the high-voltage transmitting module to generate a single-pulse acoustic signal, which enters the concrete, diffracts through the end of the crack, and is received by the receiving transducer 3. After the signal is amplified and filtered by the fixed gain amplification system of the signal receiving and conditioning module of the tester, it is converted into a digital signal by the analog-to-digital (A/D) conversion module. The main unit of the tester also includes a synchronous control element to synchronize the output of the high-voltage excitation circuit with the received signal of the A/D conversion module. The main control system collects and interprets the received digital signals, obtains the sound wave travel time t, and calculates and displays the crack depth according to the preset concrete sound velocity value v and the transducer spacing l determined by the transducer bracket:

$\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="l"\; filenames="A20081011464800281.png"\; state="\{\{state\}\}">l</figure-callout></span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\sqrt{{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; v</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}$

The transmitting transducer 2 and the receiving transducer 3 may use 50 kHz planar transducers. Because the sound wave signal used is a single pulse signal, and the adjustable gain amplification system is changed to a fixed gain amplification system, the synchronous control components and gain amplification components in the tester are greatly reduced, the operation steps are simplified, and the technical difficulty is reduced. Reduced instrument cost.

Fig. 10 is a schematic structural view of the crack tester of the present invention. The host is composed of a main control CPU module, a logic control module, a high-voltage transmitting module, a signal receiving and conditioning module, an analog-to-digital (A/D) conversion module, a man-machine interface module, a data communication module and a power management module.

The main control CPU module is the core module of the test system. It is embedded with intelligent analysis software to realize the scheduling between various functional modules. It is programmed by C language and assembly language. It mainly includes crack testing, data viewing, data clearing and data transmission. Program modules. The crack test program module analyzes and processes the collected signals, obtains the sound velocity and crack depth representing the measured crack, and stores them. The data viewing program module realizes the playback of the stored test data and browses them in pages. The data clearing program module realizes the emptying of the data storage space, and provides enough storage space for the test data. The function of the data transmission program realizes the function of uploading the data of the test system to the computer to realize long-term data backup.

The logic control module is an important carrier to realize the scheduling function of the main control CPU module. Through the logic control module, the main control CPU module loads the high-voltage excitation signal to the transmitting transducer, and at the same time transmits the A/D converted digital signal of the received signal to the CPU for further analysis and processing. In this test system, the logic control module is realized by CPLD (programmable logic device).

The high-voltage transmitting module mainly realizes the conversion from low voltage to high voltage, and generates high-voltage excitation for the transmitting transducer. The signal receiving and conditioning module mainly implements processing such as amplification and filtering of the signal from the receiving transducer. The analog-to-digital (A/D) conversion module mainly realizes the conversion from analog signal to digital signal. Human-machine interface modules mainly refer to functional modules such as LCD (liquid crystal display) and keyboards that interact directly with users. The data communication module is a hardware carrier that realizes the transmission of data stored in the test system to the PC. The main control system performs data transmission between the data communication module and the external device. In a specific embodiment, there can be two kinds of communication: USB and RS232 Way. The power management module is composed of power supply, DC-DC power conversion and other parts. Realize the conversion and distribution from the original power supply to the voltage required by each functional module of the host. The original power supply can be a lithium-ion rechargeable battery, a Ni-MH rechargeable battery or an ordinary dry battery.

Fig. 11a is a schematic diagram of a single high voltage excitation circuit of the present invention. In this embodiment, the single-time high-voltage excitation circuit is composed of a DC blocking capacitor C2 with a capacitance of 0.47μF, a switching transistor Q1 BU806, and an energy storage capacitor C1 with a capacitance of 0.47μF. Voltage to high voltage (above 500V) conversion, a single excitation pulse passes through the DC blocking capacitor C2 to the base B of the switching transistor Q1, and the high voltage is controlled from the collector C of the switching transistor Q1 to the emitter E, so that the energy storage capacitor C1 Discharge generates a single high-voltage excitation pulse signal to the transmitting transducer, and its waveform is shown in Figure 11b. Fig. 12 is a schematic diagram of a fixed large gain amplifier circuit of the present invention. The fixed large-gain amplifying circuit is composed of amplifier OP37, proportional resistors R21 and R22, filter circuit resistors R23 and C20. The sound wave signal generated by the transmitting transducer is filtered by the receiving transducer through a filter circuit composed of a resistor R23 with a resistance value of 1kΩ and a capacitor C20 with a capacitance value of 0.022μF to filter out unnecessary signals, and then through the amplifier OP37, the resistance value is The 1kΩ proportional resistor R21 and the 1MΩ proportional resistor R22 amplify the input signal by one thousand times, so that the weak signal can be collected and identified by the analog/digital converter.

Fig. 13 is a flowchart of the operation of the crack depth tester of the present invention. After turning on the tester, define and initialize the variables, clear the display screen, and then enter the sound velocity test. After the test is completed, enter the crack test mode. If you choose No, you will return to the sound velocity test mode. If you choose Yes, you will perform the first test. After the first test, go to the next test. If you select No, you will return to the first test. If you select Yes, you will perform the second test. After completion, check whether the test results are satisfactory. If the discrete value is less than the limit value, select Yes , otherwise select No, return to the second test mode, change the distance between test points, and repeat the measurement until the discrete value of the measured value is less than the limit value, and then export the test result.

Fig. 14 is an embodiment of the transducer bracket of the present invention. The transducer bracket is composed of a transducer 1, a transducer cover 2, a sound insulation material 3, a transducer cover 4, a spring 5, a slide rail 6, a positioning device 7, a test board 8 and a scale mark 9.

The left side of Figure 14a is a cross-sectional view of the transducer bracket. The transducer bracket is made of non-metallic materials, which can effectively reduce the weight. Even when tested in winter, it will not feel cold and still has a good hand feeling. The two transducers 1 are placed in the two transducer sleeves 2, and the ring-shaped sound insulation material 3 is used to cooperate with the inner wall of the transducer sleeve 2 and the transducer 1, which effectively prevents the transducer 1 from contacting the transducer. The acoustic short circuit of the energy device set 2. The inner wall of the top of the transducer cover 2 and the top of the transducer 1 are matched by a spring 5, the transducer cover 4 bears against the bottom of the transducer 1, and is fixed to the transducer cover 2 by means of threads, etc., so that the transducer The transducer 1 and the test surface can still ensure good coupling even when the surface is uneven. The two transducer sleeves 2 are respectively fixed on the two ends of the bracket, and can move along the slide rails 6 on the transducer bracket respectively. It can ensure good coupling between the transducer and the test surface, and can directly, quickly and accurately test cracks. The figure on the right is the back view of the transducer bracket. The positioning device 7 is provided on the slide rail 6, and various methods such as setting the positioning device 7 on the transducer sleeve 2 or the bracket can also be adopted.

Figure 14b is a top view of the transducer bracket. Four pairs of scale marks 9 such as 50mm, 100mm, 150mm, and 200mm are symmetrically printed on both sides of the bracket, and a positioning device 7 is provided at the position of the corresponding scale mark 9. When the transducer When the cover 2 moves to the corresponding scale mark, the transducer cover 2 can be automatically fixed by the positioning device 7, so that the distance between the transmitting and receiving transducers is accurate. A plexiglass test plate 8 marked with a cross mark is installed at the center of the bottom of the bracket, and the center is a hole to ensure that the bracket can be accurately placed on a certain position of the crack to be tested during the test, which can effectively avoid The errors caused by manual ranging and scribing and inaccurate position placement when hand-held transducers greatly improve the efficiency of measurement and the accuracy of measurement values. The bracket can be made into different lengths according to needs, such as 100mm-600mm. In the specific implementation, if the seam depth is below 50mm, a bracket with four pairs of scale marks of 50mm, 100mm, 150mm, and 200mm symmetrically printed on both sides can be used. The total length of the bracket is about 250mm to 300mm, which is easy to operate and carry. .

When using the transducer bracket, first select the distance of the first test point, and place the two transducer sleeves 2 on the corresponding position on the slide rail scale mark 9 symmetrically with the center hole of the test board 8 as the center. Prepare the crack to be tested, press the bracket slide rail to the test surface, make the transducer and the test surface well coupled, and carry out the first measurement. When performing the second or third measurement, keep the bracket slide rail still, and change the positions of the two transducer sleeves 2 symmetrically, thereby changing the distance between the second, third or multiple measurement points for measurement.

The following table is the test result of applying the crack depth tester of this patent on the concrete crack model of known crack depth, wherein each group of test data of each crack model is an embodiment of the inventive method:

It can be seen from the test results in the above table that the measurement error of the method of the present invention is relatively small, and the relative error is only between -5% and 9%.

The method, the crack depth tester and the transducer bracket of the invention can also be used for crack detection of various non-metallic solid materials, not limited to the detection of cracks of concrete materials.

Claims (29)

1. A crack depth measurement method, comprising the following steps: Step a: measuring the sound velocity v in the measured solid medium; Step b: first measuring point measurement, Place the transmitting and receiving transducers on both sides of the symmetry of the crack, the distance between the transmitting and receiving transducers is l ₁ , read the acoustic time value t ₁ , and calculate the crack depth by the following formula: ${\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\sqrt{{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; v</span>}}{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>$ Where: _h1 is the fracture depth calculated at the first measuring point, _l1 is the distance between the two transducers at the first measuring point, and _t1 is the sound wave propagation time at the first measuring point; Step c: second measuring point measurement, Set the distance between the transmitting and receiving transducers as l ₂ , the range of l ₂ is: 0.1h ₁ ≤ l ₂ ≤ 10h ₁ or 30mm ≤ l ₂ ≤ 500mm; read the sound time value t ₂ and calculate it by the following formula Crack depth value h ₂ : ${\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\sqrt{{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; t</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; v</span>}}{{\mathrm{<span\; class="notranslate">\; l</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>$ Where: _h2 is the crack depth value calculated at the second measuring point, _l2 is the distance between the two transducers at the second measuring point, and _t2 is the sound wave propagation time at the second measuring point; Step d: Calculate the average of _h1 and _h2 $\stackrel{\&OverBar;}{h}=\frac{1}{2}(h_1+h_2),$ h is the crack depth. 2. A method as claimed in claim 1, characterized in that: In the step d, continue to calculate discrete Δ=|h ₁ -h ₂ |, if the discrete value is less than a certain limit value Δ _x , then h is the fracture depth; otherwise, Add another measuring point and repeat step b until the discrete value of the depth value of this measuring point and any other measuring point before is less than the limit value Δ _x , then the average of the depth values of the two measuring points to which the discrete value belongs value as the crack depth. 3. A method according to claim 2, characterized in that: the limit value _Δx of the discrete value is 5mm-150mm, or 30%×h. 4. A kind of method as claimed in claim 2, is characterized in that: the limit value Δ _x of described discrete value is: When h<30mm, _Δx is 9mm; when h=30mm, _Δx is 9mm or 30%×h; when 30mm<h<300mm, _Δx is 30%×h; when h=300mm , Δ _x is taken as 90mm or 30%×h; when h>300mm, _Δx is taken as 90mm. 5. A method according to claim 1, characterized in that: the range of l ₁ is 30mm≤l _1≤500mm . 6. A method according to claim 5, characterized in that: the range of l ₁ is 50mm≤l _1≤250mm . 7. A method according to claim 6, characterized in that: the range of l ₁ is 80mm≤l _1≤150mm . 8. A method as claimed in claim 7, characterized in that: said l ₁ is 80mm or 100mm or 110mm or 120mm or 130mm. 9. A kind of method as claimed in claim 1, it is characterized in that: the method for measuring the sound velocity v in the measured solid medium in step a is to fix the transmitting transducer and the receiving transducer in the seamless zone At a certain distance l, measure the propagating sound time t, and calculate the concrete sound velocity v=l/t. 10. A method as claimed in claim 9, characterized in that: said spacing l is: 50mm-300mm. 11. A method as claimed in claim 10, characterized in that: said distance l is 200mm. 12. A method as claimed in claim 1, characterized in that: When h ₁ ≤ 50mm, l ₂ is 0.6 to 8 times of h ₁ , or 30mm ≤ _{l 2} ≤ 200mm; When h ₁ >50 mm, l ₂ is 0.1 to 5 times of h ₁ , or 50 mm≤l ₂ ≤400 mm. 13. A method according to claim 12, characterized in that: when h ₁ ≤ 50 mm, l ₂ =50 mm; when h ₁ >50 mm, l ₂ =150 mm. 14. A crack depth tester, comprising a main control system, a transmitting transducer, a receiving transducer, and a power module, characterized in that: The main control system is connected to the transmitting transducer through a high-voltage transmitting module, and the high-voltage transmitting module causes the transmitting transducer to generate an acoustic signal by applying a high-voltage pulse; The receiving transducer amplifies and filters the received acoustic signal through the signal receiving and conditioning module, and then converts it into a digital signal by the analog-to-digital conversion module and transmits it to the main control system; The main control system processes the received digital signal and directly calculates the crack depth; The main control system interacts with the user through the man-machine interface module. 15. A kind of crack depth tester as claimed in claim 14, is characterized in that: the calculation formula of the crack depth that described main control system adopts is as follows: $\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; l</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>\sqrt{{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; v</span>}}{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; ,</span>$ Among them: h is the crack depth value, l is the distance between two transducers, t is the sound wave propagation time, v is the sound velocity in the measured solid medium. 16. A crack depth tester as claimed in claim 14, characterized in that: the high-voltage excitation circuit in the high-voltage emission module is a single-shot high-voltage excitation circuit, and the single-shot high-voltage excitation circuit makes the emission transduction The transducer produces a single-pulse sound wave signal. 17. A crack depth tester as claimed in claim 14, characterized in that: said signal receiving and conditioning module adopts a fixed gain amplifier. 18. A crack depth tester as claimed in claim 17, characterized in that: said signal receiving and conditioning module adopts a high-gain amplifier with a magnification higher than 600 times. 19. A crack depth tester as claimed in claim 18, characterized in that: said signal receiving and conditioning module adopts a high-gain amplifier with an amplification factor of 1000 times. 20. A kind of crack depth tester as claimed in claim 14, is characterized in that: described main control system is made up of main control CPU module, logic control module; Main control CPU module is connected with logic control module, man-machine interface respectively Modules and power management modules are electrically connected to realize scheduling among functional modules; the main control CPU module is electrically connected to the high-voltage transmission module through the logic control module; the analog-to-digital conversion module is electrically connected to the main control CPU module through the logic control module connect. 21. A crack depth tester according to claim 14, characterized in that: the main control system performs data transmission between the data communication module and the external device. 22. A kind of crack depth tester as claimed in claim 14, it is characterized in that: also comprise at least one transducer support, at least one pair of transmitting transducer and receiving transducer are respectively fixed on support both sides, and respectively Can move along the slide rail on the transducer bracket. 23. A crack depth tester according to claim 22, characterized in that: scale marks are provided on the transducer bracket along the direction of the slide rail. 24. A crack depth tester as claimed in claim 22, characterized in that: a center mark is set on the transducer bracket. 25. A crack depth tester as claimed in claim 23, characterized in that: the scale marks on the transducer bracket are composed of pairs of marking lines, and each pair of scale marking lines is symmetrically distributed in the center mark sides. 26. A kind of crack depth tester as claimed in claim 25, characterized in that: there are four pairs of said scale marks, and the distances between each pair of scale marks are respectively 50mm, 100mm, 150mm, 200mm, and in corresponding The location is marked with an identity value. 27. A crack depth tester according to claim 22, characterized in that: the transducer bracket is provided with a positioning device, and the positioning device can fix the transducer on the slide rail. 28. A crack depth tester according to claim 22, characterized in that: the transducer bracket is provided with a positioning device, and the positioning device can fix the transducer at the scale mark. 29. A crack depth tester as claimed in claim 24, characterized in that: the center mark is a plexiglass plate marked with cross marks, and a small hole is arranged in the center of the cross marks.

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