Strain detection device, method and system

Abstract

The invention provides a strain detection device, method and system, the device comprises a base body and a fiber bragg grating, the base body comprises a first base body, a second base body and a stretching part, and the first base body and the second base body are used for being pasted on different positions of a to-be-detected object; the stretching part is connected between the first base body and the second base body, and an elastic hole is further formed in the stretching part; one side face of the base body is provided with an assembling groove extending along the first base body, the stretching part and the second base body. The assembling groove is communicated with the elastic hole and extends in the direction perpendicular to the elastic hole. The grating light is installed in the assembling groove and can generate following deformation along with the to-be-measured object. In the application, the elastic hole enables the stretching part to feel the deformation of the to-be-measured object more easily, that is, under the condition that the to-be-measured object is deformed, the deformation of the stretching part is easy to occur. As the fiber bragg grating is embedded or attached to the stretching part, the deformation of the stretching part can be directly transmitted to the fiber bragg grating so as to improve the detection accuracy and sensitivity.

Description

Technical Field

[0001] This application belongs to the field of optical sensing technology, and in particular relates to a strain detection device, method and system. Background Technology

[0002] Real-time health monitoring of large and complex engineering structures, timely identification of cumulative damage and assessment of their performance and lifespan, and establishment of corresponding safety early warning mechanisms to provide early warnings of potential disasters are not only of great scientific significance for improving the safety and reliability of structures, but also have considerable economic value for reducing the operating and maintenance costs of structures.

[0003] In some deformation monitoring applications, fiber Bragg grating (FBG) sensors can be used to detect the deformation of an object. However, existing strain sensors do not meet the accuracy requirements for detecting minute deformations.

[0004] It should be noted that the above content is not necessarily prior art, nor is it intended to limit the scope of patent protection of this application. Summary of the Invention

[0005] This application provides a strain detection device, method, and system to solve or alleviate one or more technical problems in the prior art.

[0006] The first aspect of this application provides a strain detection device, comprising: The matrix, comprising: The first and second substrates are used to adhere to different positions on the object to be tested; A tensioning part is connected between the first substrate and the second substrate, and the tensioning part is also provided with an elastic hole; The substrate has an assembly groove on one side, which extends along the first substrate, the stretching portion, and the second substrate. The assembly groove communicates with the elastic hole and extends in a direction perpendicular to the elastic hole. Fiber grating, installed in the assembly slot; Wherein, the light fiber The fiber optic grating can follow the deformation of the object under test; when the fiber optic grating undergoes the following deformation and receives an optical signal, the fiber optic grating that has undergone the following deformation reflects back optical signals of different wavelengths according to the deformation.

[0007] Optionally, at least one segment of the fiber grating extends out of the mounting slot, and the extended portion is used to connect other strain testing devices in series.

[0008] Optionally, the stretching portion includes a first side and a second side located on different sides of the assembly groove; The first side of the stretching part is provided with a first elastic groove, which extends toward the assembly groove side; The second side of the stretching part is provided with a second elastic groove, which extends toward the assembly groove.

[0009] Optionally, the length direction of the assembly groove is a first direction, and the width direction of the assembly groove is a second direction; The length of the elastic hole along the first direction is no greater than 0.8 cm; The length of the elastic hole along the second direction is no greater than 3.6 cm; The size of the elastic orifice is used to adjust the detection sensitivity.

[0010] Optionally, the elastic hole includes a first elastic hole and a second elastic hole, and the first elastic hole and the second elastic hole are arranged side by side along the length direction of the assembly groove.

[0011] Optionally, a first adhesive groove is formed on the first substrate, and the projection of the first adhesive groove on the first substrate at least partially overlaps with the projection of the assembly groove on the first substrate.

[0012] A second aspect of this application provides a strain detection method for detecting strain values ​​using the strain detection device described in any one of the preceding claims, the method comprising: The strain detection device is attached to the surface of the object to be tested, and the strain detection device detects the physical change in the deformation of the object to be tested. Convert the physical change into a wavelength change. The strain signal is obtained by adjusting the wavelength change. The strain value is calculated based on the strain signal.

[0013] Optionally, the method further includes: Based on the current ambient temperature and temperature compensation coefficient, temperature compensation calculations are performed on the strain value to obtain the compensated strain value.

[0014] Optionally, different ambient temperatures correspond to different temperature compensation coefficients; The temperature compensation coefficient is obtained in advance through the following operation: The strain detection device is attached to the test material with a preset expansion coefficient and placed in a temperature cycling test chamber. The temperature inside the temperature cycling test chamber is adjusted to the initial preset temperature, and the output value of the strain detection device at the initial preset temperature is recorded as the initial wavelength. The temperature inside the temperature cycling test chamber is adjusted to a first preset temperature, and the output value of the strain detection device at the first preset temperature is recorded as a first preset wavelength. The temperature compensation coefficient is calculated based on the initial preset temperature, the first preset temperature, the initial wavelength, and the first preset wavelength.

[0015] A third aspect of this application provides a strain detection system, the system comprising: The strain detection device described in any of the above is used to detect the physical change in the deformation of the object under test; A strain conversion device for converting the physical change into a wavelength change; A wavelength adjustment device is used to adjust the wavelength change to obtain a strain signal; A strain output device is used to calculate the strain value based on the strain signal.

[0016] Optionally, the system further includes: A temperature compensation device is used to perform temperature compensation calculations on the strain value based on the ambient temperature and a temperature compensation coefficient to obtain the compensated strain value.

[0017] The embodiments of this application employing the above-described technical solution may have the following advantages: The elastic aperture makes the tensile section more susceptible to sensing the deformation of the test object; that is, when the test object deforms, the tensile section deforms more readily. Since the fiber grating is embedded or attached to the tensile section, the deformation of the tensile section is directly transmitted to the fiber grating. Therefore, the elastic aperture in the tensile section allows the fiber grating to more easily follow the deformation of the test object, thus significantly altering the wavelength of the light signal reflected back by the fiber grating, thereby improving detection accuracy and sensitivity. The detection sensitivity of the fiber grating can be adjusted by pre-adjusting the size of the elastic aperture according to the required detection accuracy. For example, increasing the size of the elastic aperture makes it easier for the tensile section to follow the deformation of the test object, or decreasing the size of the elastic aperture reduces the sensitivity of the tensile section to the following deformation. Reducing the sensitivity to following deformation weakens the transmission of the deformation generated by the test object to the fiber grating, ensuring that the strain borne by the fiber grating does not exceed its ultimate tensile strain, thus increasing the strain testing range.

[0018] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of this application will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0019] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0020] Figure 1 A schematic diagram of the strain detection device provided in the embodiments of this application; Figure 2 This is a schematic diagram of the structure of the first housing of the strain detection device provided in the embodiments of this application; Figure 3 This is a schematic diagram of the structure of the second housing of the strain detection device provided in the embodiments of this application; Figure 4 This is another structural schematic diagram of the strain detection device provided in the embodiments of this application; Figure 5 A flowchart illustrating a strain detection method according to an embodiment of this application is shown schematically. Figure 6 This illustration shows a flowchart of obtaining the temperature compensation coefficient according to an embodiment of the present application; Figure 7 A schematic diagram of the strain detection system according to an embodiment of this application is shown.

[0021] Explanation of reference numerals in the attached figures: First substrate 11; Second substrate 12; Tensioning part 13; Assembly groove 15; First adhesive groove 111; Second adhesive groove 122; First elastic hole 131; Second elastic hole 132; Elastic groove 135; First cover plate 21; Second cover plate 22; Third cover plate 23; Fourth cover plate 24; Mounting hole 105; Protrusion 205; Strain detection system 30; Strain detection device 31; Strain conversion device 32; Wavelength adjustment device 33; Strain output device 34; Temperature compensation device 35. Detailed Implementation

[0022] The embodiments of this application are described in detail below, examples of which are illustrated in the accompanying drawings. In the drawings, for clarity, the dimensions of layers, regions, elements, and their relative dimensions may be exaggerated. The same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0023] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, components, areas, layers, and / or portions, these elements, components, areas, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or portion from another element, component, area, layer, or portion. Therefore, without departing from the teachings of this application, the first element, component, area, layer, or portion discussed below may be referred to as a second element, component, area, layer, or portion. And the discussion of a second element, component, area, layer, or portion does not imply that the first element, component, area, layer, or portion necessarily exists in this application.

[0024] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0025] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0026] In this application, when numerical intervals (i.e., numerical ranges) are involved, unless otherwise specified, the distribution of selectable numerical values ​​within the numerical interval is considered continuous, and includes the two endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every numerical value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that numerical interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, etc.

[0027] This application provides a strain detection device, method, and system. Based on these, the detection accuracy of the strain detection device is improved. Details are provided below.

[0028] Exemplary embodiments according to this application will now be described in more detail with reference to the accompanying drawings. It should be understood that these exemplary embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein.

[0029] Please see Figures 1-4 This application provides a strain detection device, which includes a substrate and a fiber Bragg grating. The following is a detailed description: The substrate includes a first substrate 11, a second substrate 12, and a stretching portion 13. The first substrate 11 and the second substrate 12 are used to adhere to different positions on the object to be tested, and the stretching portion 13 connects the first substrate 11 and the second substrate 12. The stretching portion 13 is also provided with elastic holes. Specifically, the material of the substrate may include carbon fiber.

[0030] Since the first substrate 11 and the second substrate 12 are directly attached to the object to be tested, the first substrate 11 and the second substrate 12 will move with the deformation of the object to be tested. For example, when the object to be tested is stretched, the distance between the first substrate 11 and the second substrate 12 will increase, so that the stretching part 13 will also be stretched. That is, the stretching part 13 is used to reflect the deformation (strain) of the object to be tested.

[0031] An assembly groove 15 is provided on one side of the substrate. The assembly groove 15 extends along the first substrate 11, the stretching part 13, and the second substrate 12. The assembly groove 15 communicates with the elastic hole and extends in a direction perpendicular to the elastic hole.

[0032] A fiber optic grating (not shown in the figure) is installed in the assembly slot 15. The grating light can follow the object under test and generate a following deformation. When the fiber optic grating generates a following deformation and receives an optical signal, the fiber optic grating that generates the following deformation reflects back optical signals of different wavelengths according to the deformation.

[0033] A fiber grating is an optical device in which a periodic refractive index variation is etched into an optical fiber. This periodic variation causes light of a specific wavelength to be reflected within the fiber, creating a characteristic peak in the reflection spectrum. When light passes through a fiber grating, the grating selectively reflects light of a specific wavelength. This specific reflected wavelength is called the Bragg wavelength, and it is determined by the grating's period and the fiber's refractive index. When the fiber is subjected to external strain, the periodic variation of the grating changes, causing a shift in the Bragg wavelength. Changes in strain lead to changes in the fiber's length and refractive index, thus affecting the Bragg wavelength. By monitoring changes in the Bragg wavelength, the strain experienced by the fiber can be precisely measured.

[0034] In this embodiment, the elastic hole makes the tension portion 13 more susceptible to sensing the deformation of the object under test; that is, when the object under test deforms, the tension portion 13 is more likely to deform as well. Since the fiber grating is embedded or attached to the tension portion 13, the deformation of the tension portion 13 is directly transmitted to the fiber grating. Therefore, the elastic hole on the tension portion 13 makes it easier for the fiber grating to follow the deformation of the object under test, thereby more significantly changing the wavelength of the light signal reflected back by the fiber grating, thus improving detection accuracy and sensitivity.

[0035] Furthermore, the elastic aperture can cause stress concentration, meaning the stress around the aperture is more pronounced. This stress concentration around the aperture allows the area surrounding it to undergo greater deformation under external forces. By using the elastic aperture in conjunction with a fiber optic grating, the stress concentration area can be controlled, making the strain of the fiber optic grating more pronounced within the region corresponding to the elastic aperture.

[0036] In this embodiment, the detection sensitivity of the fiber Bragg grating can be adjusted by pre-adjusting the size of the elastic hole according to the required detection accuracy. For example, increasing the size of the elastic hole makes it easier for the tension part 13 to follow the deformation of the object under test, or decreasing the size of the elastic hole reduces the sensitivity of the tension part 13 to the following deformation of the object under test. Reducing the sensitivity to following deformation weakens the deformation generated by the object under test before it is transmitted to the fiber Bragg grating, ensuring that the strain borne by the fiber Bragg grating does not exceed its ultimate tensile strain, thus increasing the strain testing range.

[0037] In an optional embodiment, the length direction of the assembly groove 15 is a first direction, and the width direction of the assembly groove 15 is a second direction; the shape of the elastic hole can be a rectangle with chamfered edges.

[0038] Wherein, the length of the elastic hole along the first direction is no greater than 0.8 cm, and the length of the elastic hole along the second direction is no greater than 3.6 cm; When adjusting the size of the elastic orifice, it can be enlarged or reduced proportionally to adjust the detection sensitivity accordingly. For example, the length of the elastic orifice along the first direction can be 0.4 cm, and the length along the second direction can be 1.8 cm. When it is necessary to increase the detection sensitivity, the size of the elastic orifice can be increased proportionally, for example, the length along the first direction can be changed to 0.6 cm, and the length along the second direction can be changed to 2.4 cm.

[0039] In an alternative embodiment, at least a section of the fiber grating extends out of the mounting slot 15, and the extended portion is used to connect other strain testing devices in series.

[0040] This means that a single fiber Bragg grating can be used to connect multiple strain monitoring devices, reducing both installation and maintenance costs. It also provides excellent monitoring results in large-scale or long-distance strain monitoring projects.

[0041] Furthermore, if more strain testing points are needed, additional strain testing devices can be added to the existing optical fibers without rewiring or adding extra fibers. Multiple strain testing devices can also cross-check the accuracy of their measurements.

[0042] In some embodiments, a Teflon protective film can be wrapped around the fiber grating extending from the substrate to protect the fiber grating from high temperatures.

[0043] In an optional embodiment, the stretching portion 13 includes a first side and a second side located on different sides of the mounting groove 15. The first side of the stretching portion 13 is provided with a first elastic groove 135 extending toward one side of the mounting groove 15. The second side of the stretching portion 13 is provided with a second elastic groove 135 extending toward one side of the mounting groove 15.

[0044] By providing elastic grooves 135 on both sides of the tension section 13, the elasticity of the tension section 13 can be significantly increased, making it easier to follow the deformation of the object under test.

[0045] The presence of the elastic groove 135 allows the tensile portion 13 to generate a more significant strain near the elastic groove 135 when subjected to deformation, thus enabling more accurate transmission of the strain of the object under test to the fiber optic grating. The two elastic grooves 135 located on opposite sides of the tensile portion 13 also allow for a more uniform distribution of deformation on the tensile portion 13, thereby improving the accuracy and consistency of strain transmission.

[0046] Specifically, in one embodiment, the elastic hole includes a first elastic hole 131 and a second elastic hole 132, and the first elastic hole 131 and the second elastic hole 132 are arranged side by side along the length direction of the assembly groove 15.

[0047] The parallel arrangement of the first elastic hole 131 and the second elastic hole 132 allows the tensioning part 13 to have multiple levels of elasticity. In some embodiments, the different elastic holes can be designed with different shapes and sizes, thereby giving the tensioning part 13 different elastic properties. This allows the tensioning part 13 to exhibit a more flexible response capability when facing external forces of different intensities and frequencies.

[0048] In some applications, the object under test may experience strains ranging from small to large. Multiple parallel-arranged elastic orifices enable the sensor to adapt to these changes, ensuring reliable measurement results regardless of whether the strain is slight or significant.

[0049] In other embodiments, the number of resilient holes may also be different, such as one, three, four, five, etc.

[0050] In some embodiments, a first adhesive groove 111 is provided on the first substrate 11, and the projection of the first adhesive groove 111 on the first substrate 11 at least partially overlaps with the projection of the assembly groove 15 on the first substrate 11.

[0051] The dispensing groove can be used to fill adhesives (such as epoxy resin) to fix the fiber grating in the assembly groove 15 of the first substrate 11. After the adhesive is injected into the dispensing groove and cured, the fiber grating will be firmly fixed to the first substrate 11, preventing it from loosening or shifting due to external force or vibration during use.

[0052] In this embodiment, a second adhesive groove 122 is provided on the second substrate 12. The projection of the second adhesive groove 122 on the second substrate 12 at least partially overlaps with the projection of the assembly groove 15 on the second substrate 12. The second adhesive groove 122 is used to fill adhesive in it to fix another part of the fiber optic grating in the assembly groove 15 of the second substrate 12.

[0053] Please see Figures 2-4 In this embodiment, the strain detection device further includes a housing, which comprises a first housing and a second housing. The first housing includes a first cover plate 21 and a second cover plate 22, which are respectively disposed on both sides of the first base 11. The second housing includes a third cover plate 23 and a fourth cover plate 24, which are respectively disposed on both sides of the second base 12.

[0054] The first and second housings cover the corresponding substrates, effectively protecting the internal components of the strain detection device (such as fiber optic gratings and the substrate) from external physical damage, chemical corrosion, and environmental influences. Especially in harsh environments (such as high humidity, high temperature, corrosive gases, or particulate matter), the housings provide a safe working environment for the internal components, extending the device's service life.

[0055] Furthermore, the housing provides additional structural support for the strain measurement device, increasing the overall rigidity and strength of the device. Especially when the device needs to withstand large mechanical stresses or vibrations, the housing can enhance the overall stability of the device and avoid measurement errors caused by structural deformation.

[0056] Specifically, the first base 11 has mounting holes 105, and the first cover plate 21 and the second cover plate 22 have protrusions 205 corresponding to the mounting holes 105, so that the first cover plate 21 and the second cover plate 22 are covered on both sides of the first base 11 by means of the protrusions 205 being engaged in the mounting holes 105. The second base 12, the third cover plate 23 and the fourth cover plate 24 can be provided with the same structure, so that the third cover plate 23 and the fourth cover plate 24 are covered on both sides of the second base 12 in the same way.

[0057] This application also provides a strain detection method for detecting the strain value of an object under test using the strain detection device described in the above embodiments. Please refer to [link to relevant documentation]. Figure 5 The method includes: Step S100: The strain detection device is attached to the surface of the object to be tested, and the strain detection device detects the physical change in the deformation of the object to be tested.

[0058] The purpose of this step is to fix the strain detection device to the surface of the object under test so that it can deform along with the object. The detection device uses sensitive elements such as fiber optic gratings to capture the deformation of the object under test and converts this mechanical deformation into a physical change, such as a change in length, angle, or tension. Attaching the strain detection device to the surface of the object under test also allows for real-time monitoring of the object's deformation, enabling the timely transmission of strain data to the host computer and thus real-time monitoring of the object's strain status.

[0059] When the object under test is subjected to force and deforms, the strain detection device attached to its surface will also undergo corresponding deformation. The strain detection device obtains a physical change directly related to the amount of deformation by detecting the elongation or shortening of the optical fiber caused by the deformation.

[0060] Step S102: Convert the physical change into a wavelength change.

[0061] When a fiber Bragg grating deforms, the period of its internal grating changes, resulting in a change in the wavelength of the reflected light. Physical changes (such as strain or temperature) are converted into wavelength changes through the optical effects of the fiber Bragg grating, and this wavelength change is proportional to the original physical change.

[0062] Step S104: Adjust the wavelength change to obtain a strain signal.

[0063] The wavelength change is processed using specific equipment (such as a demodulator) to eliminate or correct for noise, nonlinear errors, or environmental influences that may exist in the system. The mediated signal is more accurate and directly corresponds to the strain magnitude, thus serving as reliable data for strain measurement.

[0064] Step S106: Calculate the strain value based on the strain signal.

[0065] After undergoing a series of algorithmic processing steps, the strain signal can be ultimately processed to obtain a specific strain value. For example, by comparing the strain signal with known calibration data or models and combining it with the calibration curve of the fiber optic grating, the signal can be converted into a quantitative strain value (which can be expressed in microstrain units). This strain value can be used to assess the actual degree of deformation of the object under test under external force.

[0066] Specifically, this application uses a device to demodulate the reflected light signal to obtain the strain signal, thereby calculating the strain value (i.e., the deformation value). The strain output principle is explained in detail below: The physical properties of fiber Bragg gratings are the basis for their use as sensor devices. Research on fiber Bragg gratings must understand their physical properties and corresponding sensing principles. As an optical filter device, the center wavelength of the reflected light is sensitive to external temperature and strain. The following section will specifically analyze the relevant physical properties of fiber Bragg gratings and their sensing models.

[0067] The unique optical properties of fiber Bragg gratings allow them to be used as narrowband filters, where broadband light propagating through them undergoes partial reflection under certain conditions. This is because the refractive index of the fiber core in the fiber grating varies periodically along the axis, and frequencies that match the phase of the incident light produce coherent reflection, exhibiting optical filtering characteristics. The reflected and transmitted light passing through the grating satisfy the following formula:

[0068] In the above formula This represents the grating period of a fiber Bragg grating. β 1 and β2 represents the phase of the two transmission modes. When light passes through a fiber optic grating, mode coupling occurs between the forward and backward transmission core modes, causing the forward transmission core mode to change to the backward transmission core mode. At this time, the phase satisfies the following condition:

[0069] The grating obtained in this case has a smaller grating period. This type of fiber optic grating is the most common fiber Bragg grating, and the fiber optic grating demodulation device in this application is also based on this type of fiber Bragg grating. Its most basic principle for use as a sensor can be summarized as follows: when a broadband beam of light passes through a fiber Bragg grating, the portion of the light whose wavelength matches the grating's Bragg wavelength will be reflected. The change in this wavelength can directly reflect the change in the external physical quantity being monitored. The Bragg wavelength... It can be expressed by the following formula:

[0070] In the above formula, n eff This indicates the effective refractive index of the fiber core of the fiber grating.

[0071] When a fiber grating is subjected to external influences and undergoes strain, its core refractive index period... Effective refractive index n under the influence of elasto-optic effect eff Simultaneously, a change occurs, namely, a change in the center wavelength of the light reflected from the fiber grating. Ignoring the effect of temperature on the center wavelength of the fiber grating and considering only the influence of strain (i.e., the deformation of the object under test), the formula for the center wavelength is as follows:

[0072] In the formula The change in wavelength due to a single strain is expressed as [expression here], and the change in refractive index due to the elasto-optic effect is expressed as [expression here]. , The amount of expansion and contraction caused by stress is expressed as The change in wavelength is then:

[0073] in, This indicates the amount of change in the wavelength of the fiber Bragg grating. This represents the original wavelength without external influence. Indicates the elastic coefficient. This indicates axial strain.

[0074] Finally, compensation can be made based on the influence of ambient temperature on wavelength to eliminate the impact of temperature changes on the measurement results.

[0075] In an optional embodiment, when demodulating the wavelength change, the reflection spectrum of the fiber optic grating can be acquired first. And normalize the spectral data:

[0076] It is the maximum value of the spectral intensity, the normalized spectral intensity. The value can be between 0 and 1.

[0077] Collect reflectance spectrum It is the process of acquiring raw optical signals, which carry information about the deformation of the object under test. By analyzing the entire reflection spectrum, richer optical information can be obtained, including the drift of the center wavelength and changes in the spectral shape. This information can be used for more in-depth strain analysis and the detection of environmental changes.

[0078] The main purpose of normalization is to standardize spectral data, making spectral data under different measurement conditions comparable. Normalized spectra eliminate non-strain-dependent signal variations caused by factors such as fluctuations in light source intensity and changes in detector sensitivity. Through normalization, spectral morphological characteristics (such as peak position and full width at half maximum) can be preserved while eliminating overall intensity variations caused by external factors, resulting in more stable and consistent data.

[0079] Furthermore, moving average filtering or Gaussian filtering can be applied to remove noise:

[0080] As illustrated by example, moving average filtering can effectively smooth data curves and reduce the impact of high-frequency noise by averaging the signal.

[0081] Moving average filtering replaces the value of a signal point with the average of the values ​​of several points near that point. For Filtered value It can be represented as:

[0082] Where M is the window radius, representing the number of points selected to the left and right of a given point when calculating the average value. N is the window size, representing the total number of points used to calculate the average value (including the current point), calculated as N = 2M + 1.

[0083] A larger window will produce a smoother signal, but may reduce the signal resolution. Moving average filtering reduces the amplitude of random noise by combining the noisy signal with the average of its neighboring points, thus making the signal smoother.

[0084] For example, Gaussian filtering performs convolution operations on signals based on a Gaussian distribution function. For Filtered value By using Gaussian kernel value It is calculated using convolution:

[0085] The expression for the Gaussian kernel G(k) can be:

[0086] in, The standard deviation determines the width of the Gaussian kernel. A larger standard deviation results in a wider kernel. This produces a stronger smoothing effect, thus significantly improving the reliability of strain signals and the accuracy of measurements.

[0087] Furthermore, Gaussian fitting is used to determine the peak location, and the Gaussian function is:

[0088] Where A is the peak height. It is the peak position. That is the standard deviation.

[0089] The peak position was obtained through fitting. As demodulation wavelength .

[0090] Wavelength tracking is performed using a Kalman filter. The Kalman filter update formula is as follows:

[0091] Then, based on the calibration curve Convert wavelength to strain:

[0092] Finally, the demodulation result is output, and the strain signal is obtained.

[0093] Furthermore, in this embodiment, the strain detection method may further include: Step S108: Based on the current ambient temperature and temperature compensation coefficient, perform temperature compensation calculation on the strain value to obtain the compensated strain value.

[0094] This step is used to eliminate the impact of ambient temperature changes on the measurement accuracy of fiber Bragg grating sensors. Since temperature fluctuations can cause changes in the refractive index and grating constant of the fiber Bragg grating, thus affecting the measurement results, these effects can be corrected through temperature compensation calculations.

[0095] Specifically, please refer to Figure 6Different ambient temperatures correspond to different temperature compensation coefficients. Therefore, the relationship curve between temperature change and wavelength change can be measured and plotted in advance to facilitate compensation calculations for the measurement results.

[0096] The temperature compensation coefficient is obtained in advance through the following operations: Step S200: Attach the strain detection device to the test material with a preset expansion coefficient and place it in a temperature cycling test chamber.

[0097] Step S202: Adjust the temperature inside the temperature cycling test chamber to the initial preset temperature, and record the output value of the strain detection device at the initial preset temperature as the initial wavelength.

[0098] The initial preset temperature can be 25℃. Maintain this temperature for 3 hours, record the temperature value inside the experimental chamber and the wavelength value output by the sensor. This wavelength value is taken as "0", which is the initial wavelength at the initial strain state.

[0099] Step S204: Adjust the temperature inside the temperature cycling test chamber to a first preset temperature, and record the output value of the strain detection device at the first preset temperature as a first preset wavelength.

[0100] This step can be divided into multiple measurements to improve data accuracy. For example, the temperature inside the temperature cycling chamber can be sequentially adjusted to -20℃, 0℃, 20℃, 40℃, and 60℃. Each temperature point is maintained for 3 hours, and the specific temperature value and output wavelength value at each test point are recorded.

[0101] Step S206: Calculate the temperature compensation coefficient based on the initial preset temperature, the first preset temperature, the initial wavelength, and the first preset wavelength.

[0102] Specifically, in step S204, if multiple measurements are taken, the temperature compensation coefficient can be obtained based on the initial temperature, the initial wavelength, the temperatures measured at multiple test temperature points, and the corresponding wavelengths.

[0103] The compensated strain value can be obtained using the following formula:

[0104] in, The initial wavelength of the strain grating (in nm) is given. The actual center wavelength of the strain grating (in nm) Where λ is the measured wavelength of the temperature-compensated grating (in nm), B is the temperature compensation coefficient, and K is the strain coefficient. In some examples, K can be 0.9 pm / με.

[0105] Please see Figure 7 This application embodiment also provides a strain detection system 30, which includes: The strain detection device 31 in the above embodiment is used to detect the physical change in the deformation of the object to be tested.

[0106] The strain conversion device 32 is used to convert the physical change into a wavelength change.

[0107] Specifically, the wavelength information can be extracted by receiving the spectral signal returned by the fiber Bragg grating using a spectral analyzer. Alternatively, it can be used by a fiber Bragg grating reader to read and analyze the reflected wavelength of the fiber Bragg grating.

[0108] Wavelength adjustment device 33 is used to adjust the wavelength change to obtain a strain signal.

[0109] The strain output device 34 is used to calculate the strain value based on the strain signal.

[0110] Furthermore, the strain detection system may also include a temperature compensation device 35, which is used to perform temperature compensation calculation on the strain value based on the ambient temperature and the temperature compensation coefficient, so as to obtain the compensated strain value.

[0111] Strain testing systems can be applied to various measurement scenarios. For example, they can be used for structural health monitoring, such as monitoring the structural health of bridges by detecting deformation and strain under load to prevent potential structural failures. Alternatively, they can be used for strain monitoring of high-rise buildings and large structures to ensure structural safety and stability.

[0112] It can also be applied in the energy sector, for example, to monitor the strain of wind turbine blades and towers in real time to optimize operation and maintenance.

[0113] It can also be applied in the aerospace field, such as monitoring the strain of key parts of aircraft wings and fuselage to ensure the structural integrity of the aircraft during flight.

[0114] The strain detection system also possesses the advantages of the strain detection device 31 in any of the above embodiments, and will not be repeated here.

[0115] It should be noted that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. The directional terms "inner" and "outer" refer to the inside or outside relative to the outline of the component itself. For example, if a device in the drawings is inverted, a device described as "above" or "on top of" other devices or structures will subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0116] It should also be noted that the terms "one embodiment," "another embodiment," and "embodiment" used in this application refer to specific features, structures, or characteristics described in connection with that embodiment, which are included in at least one embodiment described in the general description of this application. The appearance of the same expression in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure, or characteristic is described in connection with any embodiment, the intention is to suggest that implementing such a feature, structure, or characteristic in conjunction with other embodiments also falls within the scope of this application.

[0117] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0118] It should also be noted that the above are merely preferred embodiments of this application and do not limit the scope of patent protection of this application. Any equivalent structural or procedural changes made using the content of this application’s specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of this application.

Claims

1. A strain detection device, characterized in that, include: The matrix comprises: The first and second substrates are used to adhere to different positions on the object to be tested; A tensioning part is connected between the first substrate and the second substrate, and the tensioning part is also provided with an elastic hole; The substrate has an assembly groove on one side, which extends along the first substrate, the stretching portion, and the second substrate. The assembly groove communicates with the elastic hole and extends in a direction perpendicular to the elastic hole. A fiber optic grating is installed in the assembly slot; The grating light can follow the object under test and generate a following deformation; when the fiber grating generates a following deformation and receives an optical signal, the fiber grating that generates the following deformation reflects back optical signals of different wavelengths according to the deformation.

2. The strain detection device according to claim 1, characterized in that, At least one section of the fiber grating extends out of the mounting slot, and the extended portion is used to connect other strain testing devices in series.

3. The strain detection device according to claim 1, characterized in that, The stretching portion includes a first side and a second side located on different sides of the assembly groove; The first side of the stretching part is provided with a first elastic groove, which extends toward the assembly groove side; The second side of the stretching part is provided with a second elastic groove, which extends toward the assembly groove.

4. The strain detection device according to claim 1, characterized in that, The length direction of the assembly groove is the first direction, and the width direction of the assembly groove is the second direction; The length of the elastic hole along the first direction is no greater than 0.8 cm; The length of the elastic hole along the second direction is no greater than 3.6 cm; The size of the elastic orifice is used to adjust the detection sensitivity.

5. The strain detection device according to claim 1, characterized in that, The elastic hole includes a first elastic hole and a second elastic hole, which are arranged side by side along the length of the assembly groove.

6. The strain detection device according to claim 1, characterized in that, The first substrate has a first adhesive groove, and the projection of the first adhesive groove on the first substrate at least partially overlaps with the projection of the assembly groove on the first substrate.

7. A strain detection method, characterized in that, The method for detecting strain values ​​using the strain detection apparatus according to any one of claims 1 to 6 includes: The strain detection device is attached to the surface of the object to be tested, and the strain detection device detects the physical change in the deformation of the object to be tested. Convert the physical change into a wavelength change. The strain signal is obtained by adjusting the wavelength change. The strain value is calculated based on the strain signal.

8. The method according to claim 7, characterized in that, The method further includes: Based on the current ambient temperature and temperature compensation coefficient, temperature compensation calculations are performed on the strain value to obtain the compensated strain value.

9. The method according to claim 8, characterized in that, Different ambient temperatures correspond to different temperature compensation coefficients; The temperature compensation coefficient is obtained in advance through the following operation: The strain detection device is attached to the test material with a preset expansion coefficient and placed in a temperature cycling test chamber. The temperature inside the temperature cycling test chamber is adjusted to the initial preset temperature, and the output value of the strain detection device at the initial preset temperature is recorded as the initial wavelength. The temperature inside the temperature cycling test chamber is adjusted to a first preset temperature, and the output value of the strain detection device at the first preset temperature is recorded as a first preset wavelength. The temperature compensation coefficient is calculated based on the initial preset temperature, the first preset temperature, the initial wavelength, and the first preset wavelength.

10. A strain detection system, characterized in that, The system includes: The strain detection device according to any one of claims 1 to 6 is used to detect the physical change in the deformation of the object under test; A strain conversion device for converting the physical change into a wavelength change; A wavelength adjustment device is used to adjust the wavelength change to obtain a strain signal; A strain output device is used to calculate the strain value based on the strain signal.

11. The strain detection system according to claim 10, characterized in that, The system also includes: A temperature compensation device is used to perform temperature compensation calculations on the strain value based on the ambient temperature and a temperature compensation coefficient to obtain the compensated strain value.

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