Method and apparatus for detecting cavities in an outer wall heat insulation layer based on laser Doppler vibration measurement

Abstract

SOLUTION: To provide an external wall thermal insulation layer hollowing detection method and device based on laser Doppler vibration measurement, the method including the steps of simulating and dividing equal-interval measurement grids on a surface of a thermal insulation layer coated on a building wall on the basis of a corresponding size, dividing a back surface of the thermal insulation layer into non-sticking areas with different area sizes on the basis of the respective divided measurement grids to simulate different hollowing components of the thermal insulation layer, and performing matrix dotting measurement on the different hollowing components using a laser Doppler non-destructive vibration meter, detecting vibration characteristics of the different hollowing components, and detecting and determining positions and sizes of hollows of the different hollowing components.EFFECT: A laser Doppler vibration measurement system is light in weight and convenient to carry, has advantages such as high measurement accuracy, high spatial resolution, fast dynamic response, and non-contact measurement, and is suitable for vibration measurement in a complex environment.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to the fields of dynamics, damage mechanics, and laser detection technology, and particularly to a method and device for detecting cavities in an outer wall insulation layer based on laser Doppler vibration measurement.

Background Art

[0002] With the progress of urbanization, in current existing buildings, most rooms use the external wall insulation method. However, the external wall insulation layer of the building is affected by factors such as the climate environment, construction conditions, and material quality in different regions, resulting in different degrees of problems such as cavities, cracks, water ingress, and shedding in the insulation layer. The structure of the building cannot reach the insulation effect at the design time. In severe cases, it will cause large-area shedding of the insulation material, leading to casualties and economic losses. Therefore, the regular health monitoring of the insulation material has attracted great attention in the environmental protection industry.

[0003] According to the above analysis, the problems and defects existing in the prior art are as follows: the manual detection error in the prior art is large, the efficiency is low, and high-altitude work is dangerous. In addition, the infrared thermal imaging measurement of the prior art is easily affected by the detection environment and climate, and it is difficult to accurately identify the cavities in the insulation material.

Summary of the Invention

Means for Solving the Problems

[0004] In order to solve the problems existing in the related technologies, the disclosed embodiments of the present invention provide a method and device for detecting cavities in an outer wall insulation layer based on laser Doppler vibration measurement. Specifically, it relates to a non-destructive detection technology for cavities in an outer wall insulation layer based on a laser Doppler vibration measurement system.

[0005] The technical solution is as follows: The method for detecting cavities in an outer wall insulation layer based on laser Doppler vibration measurement includes the following steps: Step 1 of dividing by simulating equally spaced measurement grids on the surface of the insulation layer coated on the wall of the building based on the corresponding size; Based on each divided measurement grid, step 2 of dividing the back surface of the heat insulation layer into non-adhesive areas with different area sizes and simulating different cavity components of the heat insulation layer; Step 3 of performing matrix-type point measurement on different cavity components using a laser Doppler non-destructive vibrometer to detect the vibration characteristics of different cavity components; Step 4 of collecting data on a computer through a collection system, sorting and analyzing the detection data, and determining the positioning of the cavities and the size of the cavities in different cavity components.

[0006] In step 1, dividing by simulating equally spaced measurement grids includes dividing the measurement grids by taking Δx and Δy as needed.

[0007] In step 2, different cavity components include components without abnormalities and components with multiple cavities formed.

[0008] In step 3, when performing matrix-type point measurement on different cavity components using a laser Doppler non-destructive vibrometer, furthermore, Rotate the optical shutter of the laser Doppler non-destructive vibrometer to align the helium-neon laser beam with the detection sample, adjust the focus ring based on the signal intensity indicator bar to focus, select the speed range and low-pass filter range, generate a high-frequency carrier signal in the photodetector, irradiate the detection target, and at the same time collect the reflected light, and demodulate the frequency shift signal based on the laser Doppler effect to obtain the vibration velocity quantity of the detection target.

[0009] In step 3, performing matrix-type point measurement on different cavity components further includes Changing the size of the cavities in different cavity components, hitting matrix-type points, measuring each grid in different divided measurement grids, and collecting the vibration time history waveform.

[0010] In one embodiment, collecting the vibration time history waveform is to perform a fast Fourier transform on the vibration time history waveform to obtain the corresponding vibration spectrum waveform. Specifically, Any external excitation force F(t) is an external excitation force with an infinite period T, the interval Δω = 2π / T between adjacent frequencies is an infinitesimal quantity, the frequency approaches a continuous type distribution on the interval (-∞, ∞), and when Δω → 0, the discrete variable ω n is converted into the frequency variable ω of the continuous transformation, and the expression of the spectrum function is represented as follows,

[0011]

Number

[0012] In the formula, F(t) is the external excitation force, Φ(ω) is the continuous spectrum function of the external excitation force F(t), ω is the angular frequency variable, t is the time variable, i is the imaginary unit in the complex function, and e iωt is the exponential function with the Napier number e as the base, Making the period T at the upper and lower limits infinite, the Fourier transform formula of the external excitation force F(t) is represented as follows,

[0013]

Number

[0014] In the formula, Φ(ω) is the continuous spectrum function of the external excitation force F(t), Embed the Fourier transform formula into the VibSoft software, perform data analysis and processing by the VibSoft software, control the fundamental vibration frequency of different cavity components to 50 Hz, and record the first, second, and third frequencies of different cavity components.

[0015] In one embodiment, performing data analysis processing by VibSoft software includes analyzing the influence of the size of the cavity on the vibration frequency of the entire EPS board through the measured primary, secondary, and tertiary frequencies of components without anomalies and components with multiple cavities, and further analyzing the position of the cavity and the size of the cavity area in the heat insulation layer.

[0016] In one embodiment, each unit grid of the component without anomalies is A0(i,j), where i is the horizontal axis and j is the vertical axis. The unit grids of the heat insulation layer in different working modes are set as A1(i, j), A2(i, j), and A3(i, j) respectively. Subtract the unit grid A n (i,j) of the heat insulation layer in the working mode from the component A0(i, j) without anomalies, which is represented by the following formula,

[0017]

Equation

[0018] Determine the position of the cavity by analyzing the difference between the component without anomalies and the primary vibration frequency of each measurement unit grid at different cavity sizes.

[0019] Another object of the present invention is to provide a cavity detection device for an outer wall heat insulation layer using a laser Doppler vibrometer that executes a cavity detection method for the outer wall heat insulation layer based on laser Doppler vibration measurement. The device includes A laser Doppler non-destructive vibrometer for performing matrix-type point measurement on different cavity components, comparing and analyzing the natural vibration characteristics of different cavity components, and detecting and determining the position and size of the cavity in different cavity components.

[0020] The laser Doppler non-destructive vibrometer is attached to an assembly platform. The laser Doppler non-destructive vibrometer is connected to a Vib20 data acquisition device and an AC adapter respectively via digital audio cables, and a lithium battery power supply is further connected to the AC adapter.

[0021] Combining all the above technical solutions, the advantages and positive effects of the present invention are as follows: The method for detecting cavities in the outer wall thermal insulation layer based on laser Doppler vibration measurement provided by the present invention selects one side of a building wall, pastes three pieces of the same bead method polystyrene foam on the wall using cement mortar, approximately assumes the cavities in the thermal insulation layer as non-adhesive areas with different areas, simulates the working modes of different cavities in the outer wall thermal insulation layer, uses a laser Doppler non-destructive vibrometer to set up matrix-type measurement points to obtain the vibration characteristics of the detection target, analyzes the modal data at the detection position, analyzes the rule of the influence on the structural modal data by eliminating the cavities, and further realizes the detection and quantitative evaluation of the elimination of cavities in the wall thermal insulation layer material through the change rule of the detection target modal data. For actual construction, it can provide a non-destructive detection technology for thermal insulation layer materials that is convenient for detection, actually effective, and highly feasible.

[0022] Compared with the prior art, the laser Doppler vibration measurement system has the advantages of being light in weight, convenient for carrying, high in measurement accuracy, high in spatial resolution, fast in dynamic response, and non-contact measurement, etc., and is suitable for vibration measurement in complex environments. An indoor similar material insulation layer shedding model test was carried out, data analysis and processing were performed by VibSoft software, the vibration time history waveform of the collected sample was Fourier-transformed to obtain the vibration spectrum waveform of the sample, and it was clarified that the sample was in a low-frequency vibration state by the spectrum waveform. The vibration fundamental frequency values of each group of samples were all controlled within 50 Hz, and their primary, secondary, and tertiary frequencies were recorded. The natural vibration characteristics of components without abnormalities (excluding cavities) and components containing cavities were compared and analyzed, and further, the positioning of the insulation layer cavity and the quantitative analysis of the cavity size were initially detected and judged. It was found that compared with components without abnormalities, the vibration frequency of samples containing cavities showed a downward trend, and the cavity area and its vibration frequency were inversely proportional. As shown in Figure 8, according to the analysis results of this experiment, rapid and effective detection and evaluation of the quality of the outer wall external insulation layer can be carried out, which has great social significance.

[0023] As positive effects of the present invention, it is also manifested in the following several important points, Laser Doppler vibration measurement is a remote vibration measurement method that can obtain optimal displacement and velocity resolutions. It is easy to measure the natural vibration frequency of an object and has the advantages of non-contact type, high-precision detection, high spatial resolution, fast operation response, and simple and convenient detection program, etc. It can greatly reduce manpower, material resources, and time. The damage identification technology based on vibration is easy to measure and collect vibration signals, so the detection device can be easily carried, and moreover, the detection process does not need to interrupt the normal operation of the structure, or a specific excitation device is required, so it has high application value. Laser Doppler vibration measurement is currently applied in aspects such as damage measurement of beam structures, composite materials, oil pipelines, etc., cable tension tests of cable-stayed bridges, soil classification, earthquake disaster prediction, slope protection, the mechanical field, and safety monitoring of unstable rock debris and safety and stability evaluation of landslides. However, non-destructive detection by applying the laser Doppler vibration measurement method to the insulation layer structure has not been reported yet. Currently, the traditional detection methods for building exterior wall insulation layers commonly used at home and abroad include the extraction method, manual knocking method, and infrared thermal imaging measurement method. When using the extraction method for detection, the integrity of the structure is destroyed, causing certain damage to the structure. It is a micro-damage detection method. Moreover, the detection efficiency of this method is low, and detection is difficult. The manual knocking method relies too much on the subjective judgment of the detector. It is necessary to contact mechanical equipment during detection. The detection program is complex. Moreover, the detection results are incomplete and there are omissions, and the risk is high. The infrared thermal imaging measurement method can realize the health detection of large-area general survey insulation materials. However, this detection method is easily affected by the detection environment and climate, and it is difficult to accurately identify the damage of the insulation material. Therefore, there are great limitations in actual applications. The above traditional health detection methods for insulation layer materials can only detect surface damage or easily detectable damage to a certain extent, and it is difficult to detect the cavity damage on the back surface of the insulation layer material. Based on damage mechanics and vibration mechanics, a construction structure can be regarded as a mechanical system composed of physical parameters such as rigidity, mass, and attenuation. When damage occurs to the structure, the structural rigidity characteristics will change accordingly. Laser Doppler vibration measurement can measure the damage state on the back surface of the insulation layer based on the change in the natural frequency, and can initially realize the positioning of the cavity in the insulation layer material and the quantitative analysis and evaluation of the cavity size.

Brief Description of the Drawings

[0024] Here, the drawings are incorporated into the specification and constitute a part of the specification, showing embodiments that conform to the present disclosure and used to explain the principles of the present disclosure together with the specification.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Modes for Carrying Out the Invention

[0025] To more clearly and understandably present the above objects, features, and advantages of the present invention, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the following description, many specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0026] The method for detecting cavities in the outer wall insulation layer based on laser Doppler vibration measurement according to an embodiment of the present invention includes the following steps: Step 1: Divide the surface of the insulation layer coated on the wall of the building into equally spaced measurement grids based on the corresponding size, simulating the division. Step 2: Based on each divided measurement grid, divide the back surface of the insulation layer into non-adhesive regions with different area sizes, imitating different cavity components of the insulation layer. Step 3: Use a laser Doppler non-destructive vibrometer 1 to perform matrix-type point measurement on different cavity components to detect the vibration characteristics of different cavity components. Step 4: Collect data on a computer through a collection system, organize and analyze the detection data, and determine the position and size of the cavities among different cavity components.

[0027] (Example 1) As shown in FIG. 1, the method for detecting cavities in the outer wall insulation layer based on laser Doppler vibration measurement provided by an embodiment of the present invention includes the following steps: S101: Select one side of the building wall and polish it to make it flat. S102: Apply cement mortar to the surface of the insulation layer to simulate the actual working mode, divide the grid, and name them Experimental Object One, Experimental Object Two, and Experimental Object Three respectively. S103: Provide non-adhesive regions with different areas on the back surface of each insulation layer, imitate the working modes of different cavities in the outer wall insulation layer, and paste and fix them on the wall surface with cement mortar. Assemble the laser Doppler non-destructive vibrometer 1, turn on the power supply, align the experimental object, adjust the focus ring to focus, adjust the corresponding input parameters, and S104 for hitting matrix-type points, Collect data on a computer through the collection system, organize and analyze its vibration characteristics, S105.

[0028] In Example S101 of the present invention, the building wall selects the wall of the building, and the heat insulation layer in S102 selects bead method polystyrene foam (EPS, Electronic Power Steering) as the analysis object, which is a new type and lightweight roof heat insulation material.

[0029] The parameters of the bead method polystyrene foam are two types of heat insulation layer materials with specifications of an area of 600mm×600mm and a thickness of 50mm, and an area of 1200mm×600mm and a thickness of 50mm.

[0030] In Example S104 of the present invention, non-contact non-destructive detection is performed by the laser Doppler non-destructive vibrometer 1, an indoor similar material heat insulation layer detachment model test is performed, a comparative analysis of its natural vibration characteristics by components without abnormalities (without cavities) and components with cavities, and furthermore, the positioning of the cavities in the heat insulation layer material and the quantitative analysis of the cavity size can be initially detected and determined.

[0031] The laser Doppler non-destructive vibrometer 1 has the advantages of being light in weight, convenient to carry, high in measurement accuracy, high in spatial resolution, fast in dynamic response, and non-contact measurement, and is suitable for vibration measurement in complex environments.

[0032] In Example S104 of the present invention, the cavities in the heat insulation layer are approximately assumed to be non-adhesive areas of different areas, the working modes of different cavities in the outer wall heat insulation layer are simulated, and matrix-type measurement points are hit using the laser Doppler non-destructive vibrometer 1 to analyze the detection data, so as to determine the effectiveness of the laser Doppler vibration measurement technology for eliminating cavities in the heat insulation layer.

[0033] As an example, the cavities in the heat insulation layer are approximately assumed to be non-adhesive regions with different areas, simulating the working modes of different cavities in the outer wall heat insulation layer, and by using the laser Doppler non-destructive vibrometer 1 to strike matrix-type measurement points and analyze their vibration characteristics, the effectiveness of the laser Doppler vibration measurement technology in eliminating the cavities in the heat insulation layer is determined.

[0034] (Example 2) As shown in FIGS. 2 and 9, the cavity detection device for the outer wall heat insulation layer based on laser Doppler vibration measurement provided by the embodiment of the present invention performs matrix-type point measurement on different cavity components, compares and analyzes the natural vibration characteristics of different cavity components, and includes a laser Doppler non-destructive vibrometer 1 for detecting and determining the position and size of the cavities in different cavity components. The laser Doppler non-destructive vibrometer 1 is attached to the assembly platform 4, and a tripod 8 is attached to the lower end of the assembly platform 4. The laser Doppler non-destructive vibrometer 1 is respectively connected to a Vib20 data acquisition device 2 and an AC adapter 6 via digital audio cables 3, and a lithium battery power supply 5 is further connected to the AC adapter 6.

[0035] (Example 3) As another embodiment of the present invention, the flow of the cavity detection method for the outer wall heat insulation layer based on laser Doppler vibration measurement provided by the embodiment of the present invention is shown in FIG. 3.

[0036] Currently, there are many difficulties in the detection work of building exterior wall insulation layers. One is that detection is difficult. There are many construction projects across the country, with a large amount of construction work. In particular, some high-rise buildings are difficult to detect, with high risks, and it is very difficult to carry out early detection and early repair. Therefore, the detection method disclosed in the present invention can perform non-contact remote detection using a laser, is suitable for large-area detection, has a high degree of detection freedom, high measurement accuracy, high spatial resolution, fast dynamic response, no harm to personnel and the environment, is suitable for vibration measurement in a complex environment, has a short detection time, low cost, low labor consumption, and can perform regular detection. Second, current measurement methods, such as radar measurement, infrared thermal imaging measurement, etc., are also easily affected by factors such as the environment and climate, cannot perform real-time measurement, and the measurement conditions are limited. The measurement method disclosed in the present invention can be measured at any time, has little environmental impact, can timely troubleshoot and maintain the detachment of the building exterior wall insulation layer, eliminate the quality risks of exterior wall detachment, and protect the safety of life and property.

[0037] Preparation of experimental samples, This experiment uses bead method polystyrene foam (EPS, Electronic Power Steering) as the experimental object, which is a new type of lightweight roof insulation material. The parameters of the detection component selected in this detection experiment are insulation layer materials with a specification of 600 mm × 600 mm in area and 50 mm in thickness. As shown in Figure 4, 15 mm thick cement mortar was applied to one side of the EPS and allowed to solidify naturally at room temperature. Experimental method, Step 1: Select one side of the building wall, polish it to make it flat, and fix the EPS board to the wall surface with cement mortar; Step 2: Divide the measurement grid by taking Δx and Δy as needed. In this experiment, Δx = 6 cm and Δy = 6 cm were taken, that is, the experimental component was divided into 100 grids; When unpacking the equipment for inspection and detecting samples, first complete the connection device of the laser Doppler vibration measurement system, turn on the switch of the PDV-100 power supply, rotate the optical shutter of the laser Doppler non-destructive vibrometer 1, align the helium-neon laser beam with the detection sample, adjust the focus ring based on the signal intensity indicator bar to focus, select the speed range and low-pass filter range, and the PDV-100 laser Doppler non-destructive vibrometer 1 can obtain the vibration characteristics of the structure by the heterodyne interference method. With the assistance of the Bragg cell, a high-frequency carrier signal is generated in the photodetector. The helium-neon laser emitted from the PDV-100 optical head irradiates the detection target and at the same time collects the reflected light, and demodulates the frequency shift signal based on the laser Doppler effect to obtain the vibration velocity quantity of the detection target in step 3, and Subsequently, as shown in FIG. 5, sequentially change the size of the cavity. In this experiment, four modes are set up and divided into components without abnormalities, cavity areas of 120*120 mm, 240*240 mm, and 360*360 mm. Perform matrix-type point measurement, measure for 40 seconds for each grid, and collect its vibration time history waveform in step 4, and The time domain of the vibration signal only reflects that the amplitude of the signal changes with time. The vibration time history waveform is subjected to a fast Fourier transformation (FFT) to obtain the corresponding vibration spectrum waveform, as shown in FIG. 6. Any external excitation force F(t) is an external excitation force with an infinite period T, and the interval Δω = 2π / T between adjacent frequencies is an infinitesimal quantity. The frequency approaches a continuous-type distribution on the interval (-∞, ∞). When Δω → 0, the discrete variable ω n is converted into the frequency variable ω of the continuous transformation, and the formula of the spectrum function is expressed as follows,

[0038]

Number

[0039] In the formula, F(t) is the external excitation force, Φ(ω) is the continuous spectrum function of the external excitation force F(t), ω is the frequency variable, t is the time variable, i is the imaginary unit in the complex function, and e iωt is the exponential function with the Napier number as the base, Making the period T at the upper and lower limits infinite, the Fourier transform formula of the external excitation force F(t) is expressed as follows,

[0040]

Equation

[0041] In the formula, Φ(ω) is the continuous spectrum function of the external excitation force F(t). To simplify the analysis of the measurement results, data analysis and processing are performed using VibSoft software. It is found from the spectrum waveform that the sample is in a low-frequency vibration state, and the vibration fundamental frequency values of each group of samples are all controlled within 50 Hz. Step 5 is to record its primary, secondary, and tertiary frequencies, As shown in Figure 7, by the primary, secondary, and tertiary frequencies measured for the component without abnormality and cavity areas of 120*120 mm, 240*240 mm, and 360*360 mm, first, the influence of the cavity size on the vibration frequency of the entire EPS board is analyzed, and further, the damage degree of its insulation layer is roughly analyzed. Among them, the cavity-containing samples have a tendency for their vibration frequency to decrease, and the cavity area is inversely proportional to its vibration frequency. Step 6, Through the difference between the primary vibration frequency of each measurement unit grid in the component without abnormality and different cavity size modes, the position of the cavity is further analyzed and determined. As shown in Figure 8, excluding factors such as human errors, it can well reflect the position of the cavity, and the detection result is almost the same as the set position of the cavity, thus proving the effectiveness of this detection method.

[0042] In the above embodiments, each embodiment description focuses on its own aspects. There is no part that is detailed or described in a certain embodiment, and the descriptions of other embodiments can be referred to.

[0043] The content such as the information interaction and execution process between the above-mentioned devices / units is based on the same concept, specific functions and resulting technical effects as those of the embodiments of the method of the present invention. Therefore, specifically, reference can be made to the part of the embodiments related to the method, and details will not be elaborated herein.

[0044] For the convenience and brevity of description, those skilled in the art can only take the classification of each of the above-mentioned functional units and modules as an example for explanation. In actual applications, the distribution of the above-mentioned functions can be divided into different functional units and modules as required, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the above-mentioned functions. Each functional unit and module in the embodiment may be integrated into one processing unit, or each unit may physically exist alone, or two or more units may be integrated into one unit. The above integrated unit may be realized in the form of hardware or in the form of a software functional unit. Also, the specific names of each functional unit and module are only for the purpose of being easily distinguishable from each other, and are not used to limit the protection scope of the present invention. The specific operation process of the units and modules in the above system can refer to the corresponding process in the embodiment of the above method.

[0045] Based on the technical aspects described in the above embodiments of the present invention, the following application examples can be further proposed.

[0046] The present invention further provides a computer, which includes at least one processor, a memory, and a computer program stored in the memory and executable on the at least one processor. When the processor executes the computer program, it can implement the steps in the embodiments of any of the above methods.

[0047] Embodiments of the present invention further provide a computer-readable storage medium, which stores a computer program that can implement the steps in the embodiments of the above-mentioned various methods when executed by a processor.

[0048] Embodiments of the present invention further provide an information data processing terminal, which is used to provide a user input interface for implementing the steps in the embodiments of the above-mentioned various methods when running on an electronic device, and the information data processing terminal is not limited to a mobile phone, a computer, and a switch.

[0049] Embodiments of the present invention further provide a server, which is used to provide a user input interface for implementing the steps in the embodiments of the above-mentioned various methods when running on an electronic device.

[0050] Embodiments of the present invention further provide a computer program product, which can implement the steps in the embodiments of the above-mentioned various methods when the computer program product runs on an electronic device and causes the electronic device to execute.

[0051] The integrated unit is implemented as a software functional unit and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on such understanding, this application can complete the related hardware through a computer program to realize all or part of the flow of the method in the above embodiments. The computer program can be stored in a computer-readable storage medium and, when executed by a processor, can realize the steps in the embodiments of each of the above methods. Here, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file, or some intermediate forms. The computer-readable storage medium includes at least any entity or device, recording medium, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, electrical signal, and software distribution medium that can carry the computer program code to a photographing device / terminal device. For example, a USB disk, a removable hard disk, a magnetic disk, an optical disk, etc.

[0052] In the above embodiments, each embodiment description focuses on its own aspects. There may be no detailed or described parts in one embodiment, and reference can be made to the descriptions of other embodiments.

[0053] To further prove the positive effects of the above embodiments, the experimental results based on the above technical solutions of the present invention are as follows: Based on the constant micro-vibration technology, the present invention performs non-contact and non-destructive detection through a laser Doppler vibration measurement system, conducts an indoor similar material insulation layer detachment model test, compares and analyzes the inherent vibration characteristics of components without abnormalities (excluding cavities) and components containing cavities, and further preliminarily detects and determines the positioning of the insulation layer cavity and the quantitative analysis of the cavity size. The results of this experiment can quickly and effectively inspect and evaluate the quality of the exterior insulation layer of building exterior walls, and have great social significance.

[0054] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art within the disclosed technical scope of the present invention and within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Description of Reference Numerals

[0055] 1. Laser Doppler non-destructive vibrometer; 2. Vib20 data acquisition device; 3. Digital audio cable; 4. Assembly platform; 5. Lithium battery power supply; 6. AC adapter; 7. Tripod.

Claims

1. Step 1, dividing the surface of the insulation layer applied to the wall of the building into a pattern of equally spaced measurement grids according to the corresponding sizes; Step 2: based on each divided measurement grid, divide the back surface of the insulation layer into a plurality of different area sizes of unadhesive regions, and simulate the cavity state of the actual insulation layer, where the unadhesive regions refer to areas where cement mortar is not applied; Step 3: performing a matrix-type point measurement on the experimental component using a laser Doppler non-destructive vibrometer (1) to detect vibration characteristics of the experimental component, the matrix-type point measurement being measured point by point based on the divided grid using the laser Doppler non-destructive vibrometer (1); Step 4: collecting data on a computer through a collection system, organizing and analyzing the detected data, and determining the location of the cavity and the size of the cavity in the experimental component; Including, In the step 3, performing a matrix-type point measurement on the experimental component further includes: Varying the size of the cavity of the experimental component, placing matrix-type points, measuring each grid in the different divided measurement grids, and collecting vibration time history waveforms; The vibration time history waveform is collected by performing a fast Fourier transform on the vibration time history waveform to obtain the corresponding vibration spectrum waveform; Any external excitation force F(t) is an external excitation force with a period T of infinity, and the interval between adjacent frequencies Δω=2π / T is infinitesimal. The frequency approaches a continuous distribution in the interval (-∞, ∞). When Δω→0, the discrete variable ω n is transformed into a continuous frequency variable ω, and the formula of the spectral function is given by: [006] In the formula, F(t) is the external excitation force, Φ(ω) is a continuous spectral function of the external excitation force F(t), ω is an angular frequency variable, t is a time variable, i is an imaginary unit in a complex function, and e iωt is an exponential function with Napier's constant e as the base; If the period T at the upper and lower limits is set to infinity, the Fourier transform of the external excitation force F(t) is expressed as follows: [0070] In the formula, Φ(ω) is a continuous spectral function of the external excitation force F(t) The Fourier transform formula is embedded in the VibSoft software, and data analysis processing is performed by the VibSoft software. The vibration fundamental frequency of the experimental component is controlled to 50 Hz, and the first, second and third frequencies of the experimental component are recorded. The data analysis process using VibSoft software includes analyzing the effect of the size of the cavities on the overall vibration frequency of the insulation layer through the measured primary, secondary and tertiary frequencies of normal components and components with multiple cavities, and further analyzing the location of the cavities in the insulation layer and the size of the cavity area. A method for detecting cavities in an exterior wall insulation layer based on laser Doppler vibration measurement, comprising:

2. The method for detecting cavities in an exterior wall insulation layer based on laser Doppler vibration measurement as described in claim 1, characterized in that in step 1, dividing the measurement grid to imitate an equally spaced measurement grid includes dividing the measurement grid by taking Δx and Δy.

3. The method for detecting cavities in an exterior wall insulation layer based on laser Doppler vibration measurement according to claim 1, characterized in that in step 2, the experimental components include components without abnormalities and components with multiple cavities.

4. In step 3, when performing matrix-type point measurements on the experimental component using the laser Doppler non-destructive vibrometer (1), further comprising: The method for detecting cavities in an exterior wall insulation layer based on laser Doppler vibration measurement as described in claim 1, further comprising: rotating the optical shield of the laser Doppler non-destructive vibrometer (1) to align the He-Ne laser beam with the detection sample; adjusting the focus ring to focus based on the signal intensity indicator bar; selecting the velocity range and low-pass filter range; generating a high-frequency carrier signal in the photoelectric detector; irradiating the detection object; and collecting the reflected light while demodulating the frequency shift signal based on the laser Doppler effect to obtain the vibration velocity quantity of the detection object.

5. Each unit grid of the anomaly-free component is A ０ (i, j), where i is the horizontal axis, j is the vertical axis, and the unit grid of the insulation layer in different working modes is A １ (i, j), A ２ (i, j), A ３ (i, j) and the component A is normal. ０ (i, j) is the unit grid A of the insulation layer in the working mode ｎ (i,j) is subtracted, and the result is expressed by the following formula: [0080] A method for detecting cavities in an exterior wall insulation layer based on laser Doppler vibration measurement, as described in claim 1, characterized in that the location of the cavity is determined by analyzing the difference between the primary vibration frequency of each measurement unit grid for normal components and different cavity sizes.

6. A cavity detection device for an exterior wall insulation layer using a laser Doppler vibrometer that executes the cavity detection method for an exterior wall insulation layer based on laser Doppler vibration measurement according to any one of claims 1 to 5, the device comprising: A cavity detection device for an exterior wall insulation layer using a laser Doppler vibrometer, characterized in that it includes a laser Doppler non-destructive vibrometer (1) for performing matrix point measurements on an experimental component, comparing and analyzing the natural vibration characteristics of the experimental component, and detecting and determining the positioning and size of cavities in the experimental component.

7. The laser Doppler non-destructive vibrometer (1) is mounted on an assembly platform, and a Vib20 data collection device (2) and an AC adapter (6) are respectively connected to the laser Doppler non-destructive vibrometer (1) via a digital audio cable (3), and a lithium battery power source is further connected to the AC adapter (6), and the Vib20 data collection device (2) is for converting the signal detected by the Doppler into a signal that can be recognized by a computer. The cavity detection device for an exterior wall insulation layer using a laser Doppler vibrometer as described in claim 6.

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