Strain measurement system and method based on non-contact laser

Abstract

The embodiment of the invention provides a strain measurement system and method based on non-contact laser, and the system comprises a to-be-measured component, a vibration excitation device, a three-dimensional scanning laser vibration measurer, and a processing device. A to-be-measured component is kept in a sinusoidal vibration state under a fixed frequency, and a three-dimensional scanning laser vibration measurer is used for carrying out non-contact point-by-point scanning measurement on a plurality of measurement points arranged on the surface of the to-be-measured component to obtain displacement components of the measurement points in a preset displacement direction, and respectively calculating the in-plane strain and the shear strain of each measurement point by using a processing device based on the displacement component of each measurement point in the preset displacement direction obtained by measurement. According to the strain measurement system and method, the limitation of a traditional contact type strain measurement technology is overcome, high-precision strain measurement can be achieved, and the strain measurement system and method are particularly suitable for non-contact type detection and analysis of complex structural parts and materials.

Description

Technical Field

[0001] The present disclosure relates to the field of measurement technology, and in particular to a strain measurement system and method based on non-contact laser. Background Art

[0002] With the increasing demand for structural health monitoring in industrial manufacturing, aerospace, civil engineering and other fields, accurate strain measurement plays a vital role in material mechanics analysis, structural design and failure prediction.

[0003] Traditional strain measurement methods mainly rely on contact sensors such as resistance strain gauges and fiber Bragg gratings. Although these strain measurement methods can achieve strain measurement to a certain extent, they have some limitations in practical applications, such as complex installation, easy damage to sensors, and measurement accuracy that is easily affected by environmental factors. In addition, contact measurement methods are difficult to apply in complex structures and extreme environments, limiting their scope of use.

[0004] In response to the above problems, non-contact measurement technology came into being. As an advanced non-contact measurement device, the 3D scanning laser vibrometer can obtain the vibration information of the measured object without contacting it through the scanning of the laser beam, and further derive physical quantities such as displacement, velocity and acceleration. However, when using laser vibrometers for strain measurement, the accurate calculation of in-plane strain and shear strain still faces technical challenges. These challenges include how to accurately extract strain information from the displacement data obtained by the laser vibrometer, and how to ensure the stability and accuracy of strain measurement at high vibration frequencies. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the related art, the purpose of the present disclosure is to provide a strain measurement system and method based on non-contact laser to solve the various problems existing in the related art.

[0006] The first aspect of the present disclosure provides a strain measurement system based on non-contact laser, comprising:

[0007] The component to be tested is arranged at the testing position; a plurality of measuring points are arranged on the surface of the component to be tested;

[0008] A vibration excitation device, used to perform fixed-frequency vibration excitation on the component to be tested based on the natural frequency of the component to be tested, so that the component to be tested maintains a sinusoidal vibration state at a fixed frequency;

[0009] A three-dimensional scanning laser vibrometer, comprising three scanning laser heads, for performing non-contact point-by-point scanning measurement on a plurality of measuring points arranged on the surface of the component to be measured, and obtaining a displacement component of each measuring point in a preset displacement direction during sinusoidal vibration; and

[0010] The processing device is connected to the vibration excitation device and the three-dimensional scanning laser vibrometer, and is used to calculate the in-plane strain and shear strain of each measuring point based on the displacement components of each measuring point in a preset displacement direction obtained by measurement.

[0011] In some examples of the first aspect, the component to be tested is a metal test plate, one end of the test plate is fixed, the test plate has a test surface, and the multiple measurement points are evenly distributed on the test surface.

[0012] In some examples of the first aspect, the vibration excitation device is further used to perform frequency sweep excitation on the component to be tested to identify the natural frequency of the component to be tested.

[0013] In certain examples of the first aspect, the vibration excitation device includes: a vibration excitation source and a signal generator, the signal generator is used to generate a driving signal of a predetermined frequency, the vibration excitation source is connected to the signal generator and is arranged on the component to be tested, and is used to output vibration excitation to the component to be tested under the control of the driving signal of the predetermined frequency output by the signal generator.

[0014] In some examples of the first aspect, the vibration excitation device further includes a power amplifier located between the vibration excitation source and the signal generator.

[0015] In certain examples of the first aspect, the processing device includes: a demodulation unit connected to the vibration excitation device and the three-dimensional scanning laser vibrometer, and used to demodulate the excitation information received from the vibration excitation device and the displacement components of each measurement point obtained by the three-dimensional scanning laser vibrometer in a preset displacement direction; a data acquisition unit connected to the demodulation unit; and a data processing unit connected to the data acquisition unit, and used to calculate the in-plane strain and shear strain of each measurement point based on the displacement components of each measurement point in the preset displacement direction received by the data acquisition unit.

[0016] In certain examples of the first aspect, the processing device calculates the in-plane strain and shear strain of each measuring point based on the displacement components of each measuring point in a preset displacement direction, including: calculating the displacement gradient of each measuring point in the preset displacement direction based on the displacement components of each measuring point in the preset displacement direction; calculating the in-plane strain and shear strain of each measuring point based on the displacement gradient of each measuring point in the preset displacement direction.

[0017] In some examples of the first aspect, the processing device further includes: performing strain field fitting based on the calculated in-plane strain and shear strain of each measuring point to obtain a three-dimensional strain field distribution on the surface of the component to be measured.

[0018] A second aspect of the present disclosure provides a strain measurement method based on non-contact laser, comprising the following steps:

[0019] Based on the natural frequency of the component to be tested, a fixed-frequency vibration excitation is performed on the component to be tested at the detection position, so that the component to be tested maintains a sinusoidal vibration state at a fixed frequency;

[0020] A three-dimensional scanning laser vibrometer is used to perform non-contact point-by-point scanning measurement on a plurality of measuring points arranged on the surface of the component to be measured, so as to obtain a displacement component of each measuring point in a preset displacement direction during a sinusoidal vibration process; wherein the three-dimensional scanning laser vibrometer includes three scanning laser heads; and

[0021] Based on the displacement components of each measuring point in the preset displacement direction obtained by measurement, the in-plane strain and shear strain of each measuring point are calculated respectively.

[0022] In some examples of the second aspect, the non-contact laser-based strain measurement method further includes the following step: performing a swept frequency excitation on the component to be measured to identify the natural frequency of the component to be measured.

[0023] In certain examples of the second aspect, the swept frequency excitation of the component to be measured to identify the natural frequency of the component to be measured includes the following steps: starting the swept frequency excitation from a preset minimum vibration frequency, adjusting the amplitude according to the measurement time interval and the vibration frequency, gradually increasing the vibration frequency, monitoring the vibration response of the component to be measured, and identifying the natural frequency of the component to be measured.

[0024] In certain examples of the second aspect, the in-plane strain and shear strain of each measuring point are calculated based on the displacement components of each measuring point in a preset displacement direction, including the following steps: calculating the displacement gradient of each measuring point in the preset displacement direction based on the displacement components of each measuring point in the preset displacement direction; calculating the in-plane strain and shear strain of each measuring point based on the calculated displacement gradient of each measuring point in the preset displacement direction.

[0025] In certain examples of the second aspect, the non-contact laser-based strain measurement method further includes the following steps: performing strain field fitting based on the calculated in-plane strain and shear strain of each measuring point to obtain a three-dimensional strain field distribution on the surface of the component to be measured.

[0026] As described above, the non-contact laser-based strain measurement system and method provided in the embodiments of the present disclosure include a component to be measured, a vibration excitation device, a three-dimensional scanning laser vibrometer, and a processing device. The vibration excitation device is used to perform fixed-frequency vibration excitation on the component to be measured, so that the component to be measured maintains a sinusoidal vibration state at a fixed frequency. The three-dimensional scanning laser vibrometer is used to perform non-contact point-by-point scanning measurement of multiple measurement points arranged on the surface of the component to be measured to obtain the displacement component of each measurement point in the preset displacement direction during the sinusoidal vibration process. The processing device is used to calculate the in-plane strain and shear strain of each measurement point based on the displacement components of each measurement point in the preset displacement direction obtained by the measurement. The non-contact laser-based strain measurement system and method provided in the embodiments of the present disclosure not only overcome the limitations of traditional contact strain measurement technology, but also can achieve high-precision strain measurement, which is particularly suitable for non-contact detection and analysis of complex structural parts and materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Shown is a schematic structural diagram of a strain measurement system based on non-contact laser in one embodiment of the present disclosure.

[0028] Figure 2 Display as Figure 1 The component to be tested is implemented as a structural schematic diagram of a test plate.

[0029] Figure 3 Display as Figure 1 Schematic diagram of the structure of the 3D scanning laser vibrometer.

[0030] Figure 4 Shown is a schematic flow chart of a strain measurement method based on non-contact laser in one embodiment of the present disclosure.

[0031] Figure 5 It is a schematic flow chart of a strain measurement method based on non-contact laser in another embodiment of the present disclosure. DETAILED DESCRIPTION

[0032] The following is an explanation of the embodiments of the present disclosure by specific examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the information disclosed in the present disclosure. The present disclosure can also be implemented or applied to circuits through other different specific embodiments, and the details in the present disclosure can also be modified or changed in various ways according to different viewpoints and application circuits without departing from the spirit of the present disclosure. It should be noted that the embodiments and features in the embodiments in the present disclosure can be combined with each other without conflict.

[0033] The following is a detailed description of the embodiments of the present disclosure with reference to the accompanying drawings so that those skilled in the art can easily implement the present disclosure. The present disclosure can be embodied in many different forms and is not limited to the embodiments described herein.

[0034] In the representations of the present disclosure, the reference terms "one embodiment", "certain embodiments", "examples", "specific examples", or "some examples" and the like mean that the specific features, structures, materials or characteristics represented in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. Moreover, the specific features, structures, materials or characteristics represented may be combined in any one or a group of embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples represented in the present disclosure and features of different embodiments or examples, unless they are mutually contradictory.

[0035] In addition, the terms "first" and "second" are only suitable for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the representation of the present disclosure, the meaning of "a group" is two or more, unless otherwise clearly and specifically defined.

[0036] In order to clearly describe the present disclosure, components not related to the description are omitted, and the same reference numerals are given to the same or similar components throughout the specification.

[0037] Throughout the specification, when a device is said to be "connected" to another device, this includes not only the case of "direct connection" but also the case of "indirect connection" by placing other elements therebetween. In addition, when a device is said to "include" a certain component, unless otherwise stated, it does not exclude other components, but means that other components may be included.

[0038] Although the terms first, second, etc. are used to represent various elements in this article in some examples, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, the first interface and the second interface, etc. are represented. Moreover, as used in this article, the singular forms "one", "one" and "the" are intended to also include plural forms, unless there is an opposite indication in the context. It should be further understood that the terms "comprising" and "including" indicate that there are the described features, steps, operations, elements, circuits, projects, kinds, and / or groups, but do not exclude the existence, occurrence or addition of one or a group of other features, steps, operations, elements, circuits, projects, kinds, and / or groups. The terms "or" and "and / or" used herein are interpreted as inclusive, or mean any one or any combination. Therefore, "A, B or C" or "A, B and / or C" means "any of the following: A; B; C; A and B; A and C; B and C; A, B and C". Only when the combination of elements, functions, steps or operations is inherently mutually exclusive in some way, will there be an exception to this definition.

[0039] The technical terms used herein are only applicable to specific embodiments and are not intended to limit the present disclosure. The singular form used herein also includes the plural form unless the sentence clearly indicates the contrary meaning. The meaning of "including" used in the specification is to specify specific characteristics, regions, integers, steps, operations, elements and / or components, and does not exclude the existence or addition of other characteristics, regions, integers, steps, operations, elements and / or components.

[0040] Although not defined differently, all terms, including technical and scientific terms used herein, have the same meaning as those generally understood by those skilled in the art to which the present disclosure belongs. Terms defined in commonly used dictionaries are additionally interpreted as having meanings consistent with relevant technical literature and the message of the present disclosure, and shall not be overly interpreted as ideal or very formal meanings unless defined.

[0041] Traditional strain measurement technology is mostly implemented using contact sensors, but it has limitations such as complex installation, easy damage to sensors, measurement accuracy is easily affected by environmental factors, and limited application scenarios. General non-contact measurement technology, taking the three-dimensional scanning laser vibrometer as an example, still has problems such as how to accurately extract strain information from the displacement data obtained by the laser vibrometer and how to ensure the stability and accuracy of strain measurement under high vibration frequencies.

[0042] In view of this, a non-contact laser-based strain measurement system and method are provided in an embodiment of the present disclosure to solve the problems in the related art.

[0043] On the one hand, the present disclosure provides a strain measurement system based on non-contact laser, including: a component to be measured, a vibration excitation device, a three-dimensional scanning laser vibrometer, and a processing device, wherein the vibration excitation device is used to perform fixed-frequency vibration excitation on the component to be measured so that the component to be measured maintains a sinusoidal vibration state at its natural frequency, the three-dimensional scanning laser vibrometer is used to perform non-contact point-by-point scanning measurement on multiple measurement points arranged on the surface of the component to be measured to obtain the displacement component of each measurement point in a preset displacement direction, and the processing device is used to calculate the in-plane strain and shear strain of each measurement point based on the displacement components of each measurement point in the preset displacement direction obtained by measurement. In this way, not only the limitations of traditional contact strain measurement technology are overcome, but also high-precision strain measurement can be achieved, which is particularly suitable for non-contact detection and analysis of complex structural parts and materials.

[0044] See also Figure 1 , which is a schematic diagram of the structure of a strain measurement system based on non-contact laser in one embodiment of the present disclosure.

[0045] like Figure 1 As shown, the non-contact laser-based strain measurement system includes: a component to be measured, a vibration excitation device, a three-dimensional scanning laser vibrometer, and a processing device.

[0046] The component to be tested is arranged at a testing position. A plurality of measuring points are arranged on the surface of the component to be tested.

[0047] In such Figure 1 In the embodiment shown, the component to be tested may be, for example, a metal test plate 10, one end of which is fixed, and the test plate 10 has a test surface 100, on which a plurality of measuring points are arranged. Figure 2 As shown, the length direction of the test plate 10 can be defined as the X-axis, the width direction of the test plate 10 can be defined as the Y-axis, and the thickness direction of the test plate 10 can be defined as the Z-axis. A plurality of measuring points 101 are evenly arranged on the test surface 100 of the test plate 10 to form a measuring point matrix, in which M*N measuring points are included, that is, a measuring point matrix of m rows and n columns, wherein the row direction corresponds to the X-axis and the column direction corresponds to the Y-axis. Taking the metal test plate 10 as an example, in some examples, the measuring point 101 is a label attached to the test surface 100. In some examples, the measuring point 101 is a concave or convex burnt or laser printed on the test surface 100. Exemplarily, the measuring point 101 is a dot.

[0048] The vibration excitation device is used to generate vibration excitation that can act on the component to be tested.

[0049] In such Figure 1In the illustrated embodiment, the vibration excitation device may include at least: a vibration excitation source 111 and a signal generator 113 .

[0050] The signal generator 113 is used to generate a driving signal of a predetermined frequency. Exemplarily, the driving signal may be a sinusoidal signal.

[0051] The vibration excitation source 111 is connected to the signal generator 113 and is used to output vibration excitation under the control of a driving signal of a predetermined frequency output by the signal generator 111 .

[0052] In order to enable the vibration excitation output by the vibration excitation source 111 to effectively act on the component to be tested, the vibration excitation source 111 is disposed on the component to be tested to achieve mutual contact. Figure 1 As shown, the component to be tested is a metal test plate 10, and the vibration excitation source 111 can be arranged in contact at one side or one corner of the test plate 10, so that the vibration excitation source 111 is controlled by the driving signal of the predetermined frequency output by the signal generator 113 to output vibration excitation to the test plate 10, so that the test plate 10 vibrates at a predetermined frequency based on the vibration excitation. Exemplarily, the vibration excitation source 111 can be, for example, a piezoelectric ceramic.

[0053] The vibration excitation device can generate vibration excitation acting on the component to be tested so that the component responds to the vibration excitation and vibrates at a predetermined frequency of the vibration excitation.

[0054] In some embodiments, the vibration excitation device can be used to perform frequency sweep excitation on the component to be tested to identify the natural frequency of the component to be tested.

[0055] The vibration excitation device is used to perform frequency sweep excitation on the component to be tested to identify the natural frequency of the component to be tested. This can be specifically achieved in the following manner: starting frequency sweep excitation from a preset minimum vibration frequency, adjusting the amplitude according to the measurement time interval and the vibration frequency, gradually increasing the vibration frequency, monitoring the vibration response of the component to be tested, and identifying the natural frequency of the component to be tested.

[0056] In some embodiments, the vibration excitation device further comprises a vibration sensor disposed on the component to be tested. Figure 1In the embodiment shown, the component to be tested is a metal test plate 10, and the vibration excitation source 111 in the vibration excitation device can be arranged in contact at one side or one corner of the test plate 10, and the vibration excitation source 111 outputs vibration excitation to the test plate 10, so that the test plate 10 maintains a sinusoidal vibration state at a vibration frequency corresponding to the vibration excitation, and the vibration sensor (not shown in the figure) in the vibration excitation device can be arranged in contact at another side or another corner of the test plate 10, and is used to measure the vibration response caused by the test plate 10 under the vibration excitation. Exemplarily, the vibration sensor can be, for example, an acceleration sensor.

[0057] Generally, when the frequency of the applied vibration excitation is closer and closer to the natural frequency (i.e., the resonant frequency) of the component to be measured, the amplitude value of the vibration response will continue to increase. When the frequency of the vibration excitation is equal to the natural frequency of the component to be measured, the amplitude value of the vibration response will reach the maximum. In this way, the vibration sensor can identify the natural frequency of the component to be measured by measuring the change in the amplitude value of the vibration response during the sweep frequency excitation process. Exemplarily, the vibration excitation source 111 in the vibration excitation device starts to output vibration excitation to the component to be measured at a certain vibration frequency, and the component to be measured vibrates under the vibration excitation. The vibration response can be, for example, sinusoidal vibration. The amplitude of the vibration response of the component to be measured is measured in real time by the vibration sensor in the vibration excitation device. The vibration excitation source 111 can gradually increase the vibration excitation according to a certain vibration frequency adjustment amplitude until it reaches the preset highest vibration frequency. At the same time, the vibration sensor measures the amplitude value of the vibration response of the component to be measured corresponding to each vibration excitation, and the vibration frequency of the vibration excitation corresponding to the maximum amplitude value of the vibration response is determined as the natural frequency of the component to be measured.

[0058] The following is a detailed description of the process of using a vibration excitation device to perform frequency sweep excitation on the component to be measured.

[0059] First, perform frequency sweep parameter settings, wherein these frequency sweep parameters may include but are not limited to the minimum vibration frequency, measurement time interval, and vibration frequency adjustment amplitude, etc., and the various frequency sweep parameters may be set accordingly according to the material properties and structural design of the component to be measured. For example, taking the component to be measured as an aluminum alloy flat plate as an example, when setting the frequency sweep parameters, the minimum vibration frequency is preset to 10 Hz, the maximum vibration frequency is preset to 10 kHz, the measurement time interval (i.e., the measurement time each time maintained at a vibration frequency) is set to be greater than or equal to 10 vibration cycles, and the vibration frequency adjustment amplitude is set to 5 Hz or 10 Hz.

[0060] Next, perform frequency sweep excitation, starting from the preset minimum vibration frequency, adjust the amplitude according to the measurement time interval and the vibration frequency, gradually increase the vibration frequency, monitor the vibration response of the component to be measured and measure the amplitude value corresponding to the vibration response. Still taking the aluminum alloy plate as the component to be tested as an example, the vibration excitation is output to the aluminum alloy plate from the preset minimum vibration frequency of 10 Hz, the vibration response of the aluminum alloy plate is monitored within a measurement time interval of 10 vibration cycles, and the amplitude value corresponding to the vibration response at the vibration frequency of 10 Hz is measured; the vibration frequency is increased according to the vibration frequency adjustment amplitude (for example, 5 Hz or 10 Hz), the vibration excitation is output to the aluminum alloy plate, the vibration response of the aluminum alloy plate is monitored within a measurement time interval of 10 vibration cycles, and the amplitude value corresponding to the vibration response at the increased vibration frequency is measured; the above steps are repeated, the vibration frequency is gradually increased according to the vibration frequency adjustment amplitude until it is adjusted to the highest vibration frequency, wherein the vibration response of the aluminum alloy plate is monitored within the measurement time interval of each vibration frequency, and the amplitude value corresponding to the vibration response at the adjusted vibration frequency is measured; finally, the natural frequency of the aluminum alloy plate is determined according to the amplitude values ​​corresponding to the vibration response at each vibration frequency obtained by measurement.

[0061] After the vibration excitation device is used to identify and determine the natural frequency of the component to be tested, the vibration excitation device can perform fixed-frequency vibration excitation on the component to be tested based on the natural frequency of the component to be tested, so that the component to be tested maintains a sinusoidal vibration state at a fixed frequency. Specifically, the signal generator 113 of the vibration excitation device generates a driving signal of the natural frequency to the vibration excitation source 111, and the vibration excitation source 111 is controlled by the driving signal of the natural frequency output by the signal generator 113 to output a fixed-frequency vibration excitation corresponding to the natural frequency to the component to be tested (for example, the test plate 10), so that the component to be tested (for example, the test plate 10) maintains a sinusoidal vibration at the natural frequency based on the fixed-frequency vibration excitation.

[0062] In some embodiments, the vibration excitation device further comprises a power amplifier. Figure 1 In the illustrated embodiment, the vibration excitation device further includes a power amplifier 112, which is located between the signal generator 113 and the vibration excitation source 111, that is, the output end of the signal generator is connected to the input end of the power amplifier, and the output end of the power amplifier is connected to the input end of the vibration excitation source 111. The signal generator 113 is used to amplify the power of the drive signal output from the signal generator 113.

[0063] The power amplifier can be used to gain the driving signal output by the signal generator 113 to a suitable energy level, which can effectively enhance the output power of the signal generator 113, ensure that the vibration excitation source 111 can operate stably, ensure that the vibration amplitude of the vibration excitation output by the vibration excitation source 111 is stable, and ensure that the component to be tested (such as the test plate 10) maintains a linear sinusoidal vibration state, thereby ensuring the reliability and consistency of strain measurement.

[0064] The three-dimensional scanning laser vibrometer is used to perform non-contact scanning measurement on a plurality of measuring points arranged on the surface of the component to be measured.

[0065] In some embodiments, the three-dimensional scanning laser vibrometer includes three scanning laser heads. Figure 1 As shown, the three-dimensional scanning laser vibrometer includes three scanning laser heads 131, and the three scanning laser heads 131 are all arranged on a laser head mounting bracket and facing the component to be measured (such as the test plate 10). Exemplarily, the laser head mounting bracket can be, for example, a mounting panel or a mounting plate, and the mounting panel or the mounting plate can correspond to the geometric center of the component to be measured. The three scanning laser heads are evenly arranged on the mounting panel or the mounting plate at an angle of 120°. The three scanning laser heads are all facing the component to be measured, and the three scanning focal points of the three scanning laser heads converge at one point. Exemplarily, as Figure 3 As shown, the laser head mounting bracket 130 may include a base and a mounting column disposed on the base, and three scanning laser heads 131 are disposed on the mounting column of the laser head mounting bracket 130. The three scanning laser heads 131 are all directed toward the component to be measured, and the three scanning focal points of the three scanning laser heads converge at one point. In practical applications, the orientation angles of the three scanning laser heads 131 can be adjusted according to measurement requirements.

[0066] The three scanning laser heads are all facing the test piece. Take the test piece as a test plate 10 as an example: if the test plate 10 is placed horizontally and its test surface with multiple measuring points is facing upward, the three-dimensional scanning laser vibrometer is located directly above the test plate 10, and the three scanning laser heads of the three-dimensional scanning laser vibrometer are facing downward and facing the test surface of the test plate 10. If the test plate 10 is placed horizontally and its test surface with multiple measuring points is facing downward, the three-dimensional scanning laser vibrometer is located directly below the test plate 10, and the three scanning laser heads of the three-dimensional scanning laser vibrometer are facing upward and facing the test surface of the test plate 10. If the test plate 10 is placed vertically and its test surface with multiple measuring points is facing right, the three-dimensional scanning laser vibrometer is located directly to the right of the test plate 10, and the three scanning laser heads of the three-dimensional scanning laser vibrometer are facing left and facing the test surface of the test plate 10. If the test plate 10 is placed vertically and its test surface with multiple measurement points is facing left, the three-dimensional scanning laser vibrometer is located to the left of the test plate 10, and the three scanning laser heads of the three-dimensional scanning laser vibrometer are facing right and toward the test surface of the test plate 10.

[0067] In addition, in some embodiments, the laser head mounting bracket in the three-dimensional scanning laser vibrometer may be of a mobile design, and the laser head mounting bracket may be equipped with a moving mechanism, and the laser head mounting bracket may be driven to move along a preset path by using the moving mechanism. Exemplarily, the moving mechanism may be a linear moving mechanism, which can be used to drive the laser head mounting bracket to move along a straight line. Exemplarily, the moving mechanism may be a two-dimensional moving mechanism, which can be used to drive the laser head mounting bracket to move within a preset plane. Exemplarily, the moving mechanism may be a three-dimensional moving mechanism, which can be used to drive the laser head mounting bracket to move within a preset space. Exemplarily, the movement may be a steering moving mechanism, which can be used to drive the laser head mounting bracket to turn.

[0068] By using the three scanning laser heads in the three-dimensional scanning laser vibrometer, the three scanning laser heads can simultaneously perform non-contact point-by-point scanning measurement on multiple measurement points arranged on the surface of the component to be measured, and obtain the displacement component of each measurement point in the preset displacement direction during the sinusoidal vibration process. For each measurement point, the three scanning laser heads scan and measure the measurement point to obtain the displacement component of the measurement point in the preset displacement direction during the sinusoidal vibration process. In some embodiments, the displacement component of the measurement point in the preset displacement direction during the sinusoidal vibration process may include the displacement component of the measurement point in each displacement direction on the preset coordinate axis. Exemplarily, the displacement component of the measurement point in the preset displacement direction during the sinusoidal vibration process may include the displacement component of the measurement point in the X-axis direction, the displacement component in the Y-axis direction, and the displacement component in the Z-axis direction in the preset coordinate axis.

[0069] The three scanning laser heads in the three-dimensional scanning laser vibrometer perform non-contact point-by-point scanning measurement on the multiple measurement points arranged on the surface of the component to be measured, and can traverse and scan each measurement point in the component to be measured in a preset scanning order to complete the measurement. Taking the component to be measured as a rectangular test panel as an example, multiple measurement points can be evenly arranged on the test surface of the test panel to form a measurement point matrix, and the measurement point matrix includes M*N measurement points. In this way, the three scanning laser heads in the three-dimensional scanning laser vibrometer can perform point-by-point scanning measurement on the multiple measurement points arranged on the surface of the component to be measured starting from the initial measurement point of the measurement point matrix in accordance with the preset scanning order. For example, serpentine scanning is performed starting from the upper left corner measurement point of the measurement point matrix, that is, the first row of measurement points is scanned from left to right, the second row of measurement points is scanned from right to left, the third row of measurement points is scanned from left to right, the fourth row of measurement points is scanned from right to left, and so on. But it is not limited thereto. For example, each row is scanned from left to right or from right to left.

[0070] In the disclosed embodiment, a three-dimensional scanning laser vibrometer is used for non-contact displacement measurement, which avoids the problems of complex installation of contact sensors and measurement accuracy being affected by the environment, and significantly improves the accuracy of strain measurement.

[0071] The processing device is connected to the vibration excitation device and the three-dimensional scanning laser vibrometer, and is used to calculate the in-plane strain and shear strain of each measuring point based on the displacement components of each measuring point in a preset displacement direction obtained by measurement.

[0072] In such Figure 1 In the illustrated embodiment, the vibration excitation device further includes a demodulation unit 151 , a data acquisition unit 153 , and a data processing unit 155 .

[0073] The demodulation unit 151 is connected to the signal generator 113 in the vibration excitation device and the three scanning laser heads 131 in the three-dimensional scanning laser vibrometer, and is used to demodulate the excitation information received from the vibration excitation device and the displacement components of each measurement point in a preset displacement direction obtained by the three scanning laser heads 131 in the three-dimensional scanning laser vibrometer.

[0074] The data acquisition unit 153 is connected to the demodulation unit 151, and is used to receive various types of information demodulated by the demodulation unit 151, for example, the excitation information of the signal generator 113 in the vibration excitation device and the displacement components of each measurement point in a preset displacement direction obtained by the three scanning laser heads 131 in the three-dimensional scanning laser vibrometer.

[0075] The data processing unit 155 is connected to the data acquisition unit 153 , and is used to calculate the in-plane strain and the shear strain of each measuring point based on the displacement components of each measuring point in a preset displacement direction received by the data acquisition unit 153 .

[0076] In some embodiments, the processing device calculates the in-plane strain and shear strain of each measuring point based on the displacement components of each measuring point in a preset displacement direction, including: calculating the displacement gradient of each measuring point in the preset displacement direction based on the displacement components of each measuring point in the preset displacement direction; calculating the in-plane strain and shear strain of each measuring point based on the displacement gradient of each measuring point in the preset displacement direction.

[0077] Exemplarily, the processing device first collects the displacement components of each measuring point in the preset displacement direction during the sinusoidal vibration process by performing non-contact point-by-point scanning measurement on multiple measuring points arranged on the surface of the component to be measured using the three scanning laser heads in the three-dimensional scanning laser vibrometer, for example, for a certain measuring point, the displacement u (x, y, z) in the X-axis direction, the displacement v (x, y, z) in the Y-axis direction, and the displacement w (x, y, z) in the Z-axis direction. Then, the processing device calculates the displacement gradients of each measuring point in the three displacement directions based on the displacement components of each measuring point in the preset displacement direction. For example, for a certain measuring point, the displacement gradient in the X-axis direction is: δ u / δ x , δ u / δ y , δ u / δ z ; Displacement gradient in Y-axis direction: δ v / δ x , δ v / δ y , δ v / δz ; Displacement gradient in Z-axis direction: δ w / δ x , δ w / δ y , δ w / δ z Next, the processing device calculates the in-plane strain and shear strain of each measuring point based on the calculated displacement gradient of each measuring point in the preset displacement direction. For example, for a certain measuring point, the in-plane strain in the X-axis direction is: ε x =δ u / δ x , in-plane strain in the Y-axis direction: ε y =δ v / δ y , in-plane strain in the Z-axis direction: ε z =δ w / δ z , XY plane shear strain: γ xy =δ u / δ y +δ v / δ x , YZ plane shear strain: γ yz =δ v / δ z +δ w / δ y , ZX plane shear strain: γ zx =δ w / δ x +δ u / δ z .

[0078] In some embodiments, the processing device further comprises: performing strain field fitting based on the calculated in-plane strain and shear strain of each measuring point to obtain the three-dimensional strain field distribution of the surface of the component to be measured. Exemplarily, as mentioned above, for a certain measuring point, based on the calculated in-plane strain and shear strain of each measuring point, strain field fitting is performed, and a continuous strain field is formed by interpolating and fitting the strain data of each measuring point, thereby obtaining the final three-dimensional strain field diagram.

[0079] exist Figure 1 In the illustrated embodiment, based on the displacement components of each measuring point in a preset displacement direction, respectively calculating the in-plane strain and shear strain of each measuring point, and performing strain field fitting based on the calculated in-plane strain and shear strain of each measuring point can be achieved by the data processing unit 155.

[0080] In some embodiments, the data processing unit may include a processor and a memory, and a computer program may be stored in the memory. The processor implements each calculation step by running the computer program in the memory. Exemplarily, the processor shown may be implemented by a central processing unit (CPU), a microprocessing unit (MCU), a system on chip (SoC), or a field programmable gate array (FPGA). The memory may include a volatile memory for temporary storage of data when running a program, such as a random access memory (RAM). The memory 203 may also include a non-volatile memory for data storage, such as a read-only memory (ROM), a flash memory, a hard disk drive (HDD) or a solid-state disk (SSD).

[0081] The non-contact laser-based strain measurement system provided in the embodiment of the present disclosure includes a component to be measured, a vibration excitation device, a three-dimensional scanning laser vibrometer, and a processing device. The vibration excitation device is used to perform fixed-frequency vibration excitation on the component to be measured, so that the component to be measured maintains a sinusoidal vibration state at its natural frequency. The three-dimensional scanning laser vibrometer is used to perform non-contact point-by-point scanning measurement of multiple measurement points arranged on the surface of the component to be measured to obtain the displacement component of each measurement point in a preset displacement direction during the sinusoidal vibration process. The processing device is used to calculate the in-plane strain and shear strain of each measurement point based on the displacement components of each measurement point in the preset displacement direction obtained by measurement. The non-contact laser-based strain measurement system provided in the embodiment of the present disclosure not only overcomes the limitations of traditional contact strain measurement technology, but also can achieve high-precision strain measurement, which is particularly suitable for non-contact detection and analysis of complex structural parts and materials. The non-contact laser-based strain measurement system provided in the embodiments of the present disclosure has the advantages of simple structure and easy operation, and can be applied to strain measurement in various complex environments, especially in applications requiring high-precision, non-contact measurement, such as aerospace, civil engineering, materials science, and high-performance composite materials, and has broad application prospects.

[0082] Another aspect of the present disclosure provides a strain measurement method based on non-contact laser.

[0083] See also Figure 4, which is a flow chart of a strain measurement method based on non-contact laser in one embodiment of the present disclosure.

[0084] like Figure 4 As shown, the strain measurement method based on non-contact laser includes the following steps:

[0085] Step S401 : Based on the natural frequency of the component to be tested, a fixed-frequency vibration excitation is performed on the component to be tested located at the detection position, so that the component to be tested maintains a sinusoidal vibration state at a fixed frequency.

[0086] In step S401, a fixed-frequency vibration excitation is performed on the component to be tested located at the detection position based on the natural frequency of the component to be tested. Exemplarily, a fixed-frequency vibration excitation corresponding to the natural frequency of the component to be tested is generated and output to the component to be tested, and the component to be tested maintains a sinusoidal vibration state at the fixed frequency (i.e., the natural frequency) based on the received fixed-frequency vibration excitation.

[0087] In certain embodiments, the non-contact laser-based strain measurement method further includes the step of identifying the natural frequency of the component to be measured.

[0088] See also Figure 5 , which is a flow chart of a strain measurement method based on non-contact laser in another embodiment of the present disclosure.

[0089] like Figure 5 As shown, in step S400, a swept frequency excitation is performed on the component to be tested to identify the natural frequency of the component to be tested.

[0090] The natural frequency of the component to be measured is identified by performing a swept frequency excitation on the component to be measured. This can be specifically achieved in the following manner: starting the swept frequency excitation from a preset minimum vibration frequency, adjusting the amplitude according to the measurement time interval and the vibration frequency, gradually increasing the vibration frequency, monitoring the vibration response of the component to be measured, and identifying the natural frequency of the component to be measured.

[0091] Generally, when the frequency of the applied vibration excitation is closer and closer to the natural frequency (i.e., the resonant frequency) of the component to be measured, the amplitude value of the vibration response will continue to increase. When the frequency of the vibration excitation is equal to the natural frequency of the component to be measured, the amplitude value of the vibration response will reach a maximum. In this way, the natural frequency of the component to be measured can be identified by measuring the change in the amplitude value of the vibration response during the sweep frequency excitation process. Exemplarily, the vibration excitation is output to the component to be measured at a certain vibration frequency, and the component to be measured generates a vibration response under the vibration excitation. The vibration response can be, for example, a sinusoidal vibration. The amplitude of the vibration response of the component to be measured is measured in real time. The vibration excitation can be gradually increased according to a certain vibration frequency adjustment amplitude until it reaches a preset maximum vibration frequency. At the same time, the amplitude value of the vibration response of the component to be measured corresponding to each vibration excitation is measured, and the vibration frequency of the vibration excitation corresponding to the maximum amplitude value of the vibration response is determined as the natural frequency of the component to be measured.

[0092] Step S403, using a three-dimensional scanning laser vibrometer to perform non-contact point-by-point scanning measurement on multiple measuring points arranged on the surface of the component to be measured, to obtain the displacement component of each measuring point in a preset displacement direction during the sinusoidal vibration process; wherein the three-dimensional scanning laser vibrometer includes three scanning laser heads.

[0093] The three-dimensional scanning laser vibrometer is used to perform non-contact scanning measurement on a plurality of measuring points arranged on the surface of the component to be measured.

[0094] In some embodiments, the three-dimensional scanning laser vibrometer includes three scanning laser heads, each of which is directed toward a respective measuring point of the component to be measured, and three scanning focal points of the three scanning laser heads converge at one point.

[0095] By using the three scanning laser heads in the three-dimensional scanning laser vibrometer, the three scanning laser heads can simultaneously perform non-contact point-by-point scanning measurement on multiple measurement points arranged on the surface of the component to be measured, and obtain the displacement component of each measurement point in the preset displacement direction during the sinusoidal vibration process. For each measurement point, the three scanning laser heads scan and measure the measurement point to obtain the displacement component of the measurement point in the preset displacement direction during the sinusoidal vibration process. In some embodiments, the displacement component of the measurement point in the preset displacement direction during the sinusoidal vibration process may include the displacement component of the measurement point in each displacement direction on the preset coordinate axis. Exemplarily, the displacement component of the measurement point in the preset displacement direction during the sinusoidal vibration process may include the displacement component of the measurement point in the X-axis direction, the displacement component in the Y-axis direction, and the displacement component in the Z-axis direction in the preset coordinate axis.

[0096] The three scanning laser heads in the three-dimensional scanning laser vibrometer perform non-contact point-by-point scanning measurement on the multiple measurement points arranged on the surface of the component to be measured, and can traverse and scan each measurement point in the component to be measured in a preset scanning order to complete the measurement. Taking the component to be measured as a rectangular test panel as an example, multiple measurement points can be evenly arranged on the test surface of the test panel to form a measurement point matrix, and the measurement point matrix includes M*N measurement points. In this way, the three scanning laser heads in the three-dimensional scanning laser vibrometer can perform point-by-point scanning measurement on the multiple measurement points arranged on the surface of the component to be measured starting from the initial measurement point of the measurement point matrix in accordance with the preset scanning order. For example, serpentine scanning is performed starting from the upper left corner measurement point of the measurement point matrix, that is, the first row of measurement points is scanned from left to right, the second row of measurement points is scanned from right to left, the third row of measurement points is scanned from left to right, the fourth row of measurement points is scanned from right to left, and so on. But it is not limited thereto. For example, each row is scanned from left to right or from right to left.

[0097] Step S405 , based on the displacement components of each measuring point in the preset displacement direction obtained by measurement, the in-plane strain and the shear strain of each measuring point are calculated respectively.

[0098] In some embodiments, the in-plane strain and shear strain of each measuring point are calculated based on the displacement components of each measuring point in a preset displacement direction, including: calculating the displacement gradient of each measuring point in the preset displacement direction based on the displacement components of each measuring point in the preset displacement direction; calculating the in-plane strain and shear strain of each measuring point based on the displacement gradient of each measuring point in the preset displacement direction.

[0099] Exemplarily, firstly, the displacement components of each measuring point in the preset displacement direction during the sinusoidal vibration process are obtained by performing non-contact point-by-point scanning measurement on multiple measuring points arranged on the surface of the component to be measured using three scanning laser heads in the three-dimensional scanning laser vibrometer, for example, for a certain measuring point, the displacement u (x, y, z) in the X-axis direction, the displacement v (x, y, z) in the Y-axis direction, and the displacement w (x, y, z) in the Z-axis direction. Then, the processing device calculates the displacement gradients of each measuring point in the three displacement directions based on the displacement components of each measuring point in the preset displacement direction. For example, for a certain measuring point, the displacement gradient in the X-axis direction is: δ u / δ x , δ u / δ y , δ u / δ z ; Displacement gradient in Y-axis direction: δ v / δ x , δv / δ y , δ v / δ z ; Displacement gradient in Z-axis direction: δ w / δ x , δ w / δ y , δ w / δ z Next, the processing device calculates the in-plane strain and shear strain of each measuring point based on the calculated displacement gradient of each measuring point in the preset displacement direction. For example, for a certain measuring point, the in-plane strain in the X-axis direction is: ε x =δ u / δ x , in-plane strain in the Y-axis direction: ε y =δ v / δ y , in-plane strain in the Z-axis direction: ε z =δ w / δ z , XY plane shear strain: γ xy =δ u / δ y +δ v / δ x , YZ plane shear strain: γ yz =δ v / δ z +δ w / δ y , ZX plane shear strain: γ zx =δ w / δ x +δ u / δ z .

[0100] In some embodiments, in step S405, it also includes: based on the calculated in-plane strain and shear strain of each measuring point, strain field fitting is performed to obtain the three-dimensional strain field distribution of the surface of the component to be measured. Exemplarily, as mentioned above, for a certain measuring point, based on the calculated in-plane strain and shear strain of each measuring point, strain field fitting is performed, and a continuous strain field is formed by interpolating and fitting the strain data of each measuring point, thereby obtaining the final three-dimensional strain field diagram. In this way, the collected displacement data is analyzed and processed in real time, and the strain distribution diagram and other key analysis data are quickly generated, which significantly improves the measurement efficiency and the practicality of the data, and provides strong support for engineering applications and research.

[0101] The non-contact laser-based strain measurement method provided in the embodiment of the present disclosure performs fixed-frequency vibration excitation on the component to be measured at the detection position so that the component to be measured maintains a sinusoidal vibration state at a fixed frequency, and uses a three-dimensional scanning laser vibrometer to perform non-contact point-by-point scanning measurement on multiple measurement points arranged on the surface of the component to be measured to obtain the displacement component of each measurement point in the preset displacement direction during the sinusoidal vibration process, and then calculates the in-plane strain and shear strain of each measurement point respectively. The non-contact laser-based strain measurement system provided in the embodiment of the present disclosure not only overcomes the limitations of traditional contact strain measurement technology, but also can achieve high-precision strain measurement, which is particularly suitable for non-contact detection and analysis of complex structural parts and materials.

[0102] The following describes in detail the non-contact laser-based strain measurement system and method thereof provided according to the embodiments of the present disclosure, with examples in certain applications.

[0103] Example 1: In advance, an aluminum alloy plate with a length of 300 mm, a width of 200 mm, and a thickness of 10 mm is selected. The test surface of the aluminum alloy plate is evenly arranged with 20×21 measurement points, a total of 420 points. One side of the aluminum alloy plate is fixed, and the other side is freely suspended. The piezoelectric ceramic serving as a vibration excitation source is fixed at the edge of the aluminum alloy plate, and the piezoelectric ceramic is connected to a power amplifier and a signal generator. A three-dimensional scanning laser vibrometer is set directly above the aluminum alloy plate, and the three scanning laser heads in the three-dimensional scanning laser vibrometer are installed on a bracket. The processing device includes a demodulation unit, a data acquisition unit, and a data processing unit connected in sequence, and the signal generator and the three-dimensional scanning laser vibrometer are connected to the input end of the demodulation unit.

[0104] Next, the vibration excitation device was started, and sweep frequency excitation was started, and the frequency was gradually increased from 10 Hz. The amplitude was adjusted at a vibration frequency of 5 Hz or 10 Hz, and gradually increased to 10 kHz. The vibration response of the aluminum alloy plate was monitored, and its first-order natural frequency was determined to be 500 Hz.

[0105] Next, after determining the first-order natural frequency of the aluminum alloy plate, the vibration excitation device is switched to a 500 Hz fixed-frequency vibration excitation mode, so that the aluminum alloy plate maintains a sinusoidal vibration state at the natural frequency.

[0106] Next, a three-dimensional scanning laser vibrometer is started, and three scanning laser heads in the three-dimensional scanning laser vibrometer perform non-contact point-by-point scanning measurement along 20×21 measurement points, a total of 420 measurement points, arranged on the test surface of the aluminum alloy plate, to obtain the displacement component of each measurement point in a preset displacement direction during the sinusoidal vibration process, including the displacement u (x, y, z) in the X-axis direction, the displacement v (x, y, z) in the Y-axis direction, and the displacement w (x, y, z) in the Z-axis direction, and transmit the displacement component of each measurement point to a data acquisition unit.

[0107] Next, the data processing unit calculates the displacement gradients of each measuring point in the three displacement directions according to the displacement components of each measuring point in the three displacement directions collected by the data collection unit, which are respectively:

[0108] X-axis displacement gradient: δ u / δ x , δ u / δ y , δ u / δ z ;

[0109] Displacement gradient in the Y-axis direction: δ v / δ x , δ v / δ y , δ v / δ z ;

[0110] Displacement gradient in the Z-axis direction: δ w / δ x , δ w / δ y , δ w / δ z .

[0111] Next, according to the calculated displacement gradients of each measuring point in the three displacement directions, the in-plane strain and shear strain of each measuring point are calculated respectively, which are:

[0112] In-plane strain in the X-axis direction: ε x =δ u / δ x ;

[0113] In-plane strain in the Y-axis direction: ε y =δ v / δ y ;

[0114] In-plane strain in the Z-axis direction: ε z =δ w / δ z ;

[0115] XY plane shear strain: γ xy =δ u / δ y +δ v / δ x ;

[0116] YZ plane shear strain: γ yz =δ v / δ z +δ w / δ y ;

[0117] ZX plane shear strain: γ zx =δ w / δ x +δ u / δ z .

[0118] Finally, strain field fitting is performed based on the calculated in-plane strain and shear strain of each measuring point. The strain data of the measuring points are interpolated and fitted to form a continuous strain field and then the final three-dimensional strain field diagram is obtained.

[0119] Example 2, in advance, an aluminum alloy plate with a length of 300mm, a width of 200mm, and a thickness of 10mm is selected. The test surface of the aluminum alloy plate is evenly arranged with 20×21, a total of 420 measurement points. One side of the aluminum alloy plate is fixed, and the other side is freely suspended. The piezoelectric ceramic serving as a vibration excitation source is fixed at the edge of the aluminum alloy plate, and the piezoelectric ceramic is connected to a power amplifier and a signal generator. A three-dimensional scanning laser vibrometer is set directly above the aluminum alloy plate, and the three scanning laser heads in the three-dimensional scanning laser vibrometer are installed on a bracket. The processing device includes a demodulation unit, a data acquisition unit, and a data processing unit connected in sequence, and the signal generator and the three-dimensional scanning laser vibrometer are connected to the input end of the demodulation unit.

[0120] Next, the vibration excitation device was started and sweep frequency excitation was started, the frequency was gradually increased from 10 Hz, the vibration frequency was adjusted from 5 Hz to 10 Hz, and gradually increased to 10 kHz. The vibration response of the aluminum alloy plate was monitored and its second-order natural frequency was determined to be 800 Hz.

[0121] Next, after determining the second-order natural frequency of the aluminum alloy plate, the vibration excitation device is switched to an 800 Hz fixed-frequency vibration excitation mode, so that the aluminum alloy plate maintains a sinusoidal vibration state at the natural frequency.

[0122] Next, a three-dimensional scanning laser vibrometer is started, and three scanning laser heads in the three-dimensional scanning laser vibrometer perform non-contact point-by-point scanning measurement along 20×21 measurement points, a total of 420 measurement points, arranged on the test surface of the aluminum alloy plate, to obtain the displacement component of each measurement point in a preset displacement direction during the sinusoidal vibration process, including the displacement u (x, y, z) in the X-axis direction, the displacement v (x, y, z) in the Y-axis direction, and the displacement w (x, y, z) in the Z-axis direction, and transmit the displacement component of each measurement point to a data acquisition unit.

[0123] Next, the data processing unit calculates the displacement gradients of each measuring point in the three displacement directions according to the displacement components of each measuring point in the three displacement directions collected by the data collection unit, which are respectively:

[0124] X-axis displacement gradient: δ u / δ x , δ u / δ y , δ u / δ z ;

[0125] Displacement gradient in the Y-axis direction: δ v / δ x , δ v / δ y , δ v / δ z ;

[0126] Displacement gradient in the Z-axis direction: δ w / δ x , δ w / δ y , δ w / δ z .

[0127] Next, according to the calculated displacement gradients of each measuring point in the three displacement directions, the in-plane strain and shear strain of each measuring point are calculated respectively, which are:

[0128] In-plane strain in the X-axis direction: ε x =δ u / δ x ;

[0129] In-plane strain in the Y-axis direction: ε y =δ v / δ y ;

[0130] In-plane strain in the Z-axis direction: ε z =δ w / δ z ;

[0131] XY plane shear strain: γ xy =δ u / δ y +δ v / δ x ;

[0132] YZ plane shear strain: γ yz =δ v / δ z +δ w / δ y ;

[0133] ZX plane shear strain: γ zx =δ w / δ x +δ u / δ z .

[0134] Finally, strain field fitting is performed based on the calculated in-plane strain and shear strain of each measuring point. The strain data of the measuring points are interpolated and fitted to form a continuous strain field and then the final three-dimensional strain field diagram is obtained.

[0135] The non-contact laser-based strain measurement system and method provided in the embodiment of the present disclosure include a component to be measured, a vibration excitation device, a three-dimensional scanning laser vibrometer, and a processing device. The vibration excitation device is used to perform fixed-frequency vibration excitation on the component to be measured, so that the component to be measured maintains a sinusoidal vibration state at a fixed frequency. The three-dimensional scanning laser vibrometer is used to perform non-contact point-by-point scanning measurement on multiple measurement points arranged on the surface of the component to be measured to obtain the displacement component of each measurement point in the preset displacement direction during the sinusoidal vibration process. The processing device is used to calculate the in-plane strain and shear strain of each measurement point based on the displacement component of each measurement point in the preset displacement direction obtained by the measurement. In the embodiment of the present disclosure, by combining the precisely controlled vibration excitation device with the high-precision three-dimensional scanning laser vibrometer, stable sinusoidal vibration can be provided in a multi-frequency range, ensuring high precision and high resolution of strain measurement. In addition, in the embodiment of the present disclosure, not only the in-plane strain of the component to be measured can be measured, but also the shear strain of the component to be measured can be measured. Through the multi-dimensional data processing system, a complete three-dimensional strain field distribution can be generated, providing comprehensive data support for structural health monitoring and material mechanical property analysis.

[0136] The above embodiments are merely illustrative of the principles and effects of the present disclosure, and are not intended to limit the present disclosure. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present disclosure. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed in the present disclosure shall still be covered by the protection scope of the present disclosure.

Claims

1. A strain measurement system based on non-contact laser, characterized in that: include: The component to be tested is arranged at the testing position; a plurality of measuring points are arranged on the surface of the component to be tested; A vibration excitation device, used to perform fixed-frequency vibration excitation on the component to be tested based on the natural frequency of the component to be tested, so that the component to be tested maintains a sinusoidal vibration state at a fixed frequency; A three-dimensional scanning laser vibrometer, comprising three scanning laser heads, for performing non-contact point-by-point scanning measurement on a plurality of measuring points arranged on the surface of the component to be measured, and obtaining a displacement component of each measuring point in a preset displacement direction during sinusoidal vibration; as well as The processing device is connected to the vibration excitation device and the three-dimensional scanning laser vibrometer, and is used to calculate the in-plane strain and shear strain of each measuring point based on the displacement components of each measuring point in a preset displacement direction obtained by measurement.

2. The non-contact laser-based strain measurement system according to claim 1, characterized in that: The component to be tested is a metal test plate, one end of which is fixedly arranged. The test plate has a test surface, and the plurality of measuring points are evenly arranged on the test surface.

3. The non-contact laser-based strain measurement system according to claim 1, characterized in that: The vibration excitation device includes: a vibration excitation source and a signal generator, the signal generator is used to generate a driving signal of a predetermined frequency, the vibration excitation source is connected to the signal generator and is arranged on the component to be tested, and is used to output vibration excitation to the component to be tested under the control of the driving signal of the predetermined frequency output by the signal generator.

4. The non-contact laser-based strain measurement system according to claim 3, characterized in that: The vibration excitation device also includes a vibration sensor arranged on the component to be tested. The vibration excitation source in the vibration excitation device is used to perform frequency sweep excitation on the component to be tested. The vibration sensor is used to monitor the vibration response of the component to be tested and identify the natural frequency of the component to be tested.

5. The non-contact laser based strain measurement system according to claim 3 or 4, characterized in that: The vibration excitation device also includes a power amplifier located between the vibration excitation source and the signal generator.

6. The non-contact laser based strain measurement system according to claim 1, characterized in that: The processing device comprises: a demodulation unit connected to the vibration excitation device and the three-dimensional scanning laser vibrometer, and used to demodulate the excitation information received from the vibration excitation device and the displacement components of each measurement point obtained by the three-dimensional scanning laser vibrometer in a preset displacement direction; a data acquisition unit connected to the demodulation unit; and The data processing unit is connected to the data acquisition unit and is used to calculate the in-plane strain and shear strain of each measuring point based on the displacement components of each measuring point in a preset displacement direction received by the data acquisition unit.

7. The non-contact laser based strain measurement system according to claim 1, characterized in that: The processing device calculates the in-plane strain and shear strain of each measuring point based on the displacement components of each measuring point in a preset displacement direction, including: Calculating the displacement gradient of each measuring point in the preset displacement direction based on the displacement components of each measuring point in the preset displacement direction obtained by measurement; and Based on the calculated displacement gradient of each measuring point in the preset displacement direction, the in-plane strain and shear strain of each measuring point are calculated.

8. The non-contact laser based strain measurement system according to claim 7, characterized in that: The processing device further comprises: performing strain field fitting based on the calculated in-plane strain and shear strain of each measuring point to obtain the three-dimensional strain field distribution on the surface of the component to be measured.

9. A strain measurement method based on non-contact laser, characterized in that: The steps include: Based on the natural frequency of the component to be tested, a fixed-frequency vibration excitation is performed on the component to be tested at the detection position, so that the component to be tested maintains a sinusoidal vibration state at a fixed frequency; A three-dimensional scanning laser vibrometer is used to perform non-contact point-by-point scanning measurement on a plurality of measuring points arranged on the surface of the component to be measured, so as to obtain a displacement component of each measuring point in a preset displacement direction during a sinusoidal vibration process; wherein the three-dimensional scanning laser vibrometer includes three scanning laser heads; and Based on the displacement components of each measuring point in the preset displacement direction obtained by measurement, the in-plane strain and shear strain of each measuring point are calculated respectively.

10. The non-contact laser based strain measurement method according to claim 9, characterized in that: The method further comprises the following steps: performing frequency sweeping excitation on the component to be tested to identify the natural frequency of the component to be tested.

11. The non-contact laser based strain measurement method according to claim 10, characterized in that: The step of performing frequency sweeping excitation on the component to be tested to identify the natural frequency of the component to be tested comprises the following steps: The sweep frequency excitation is started from the preset minimum vibration frequency, the amplitude is adjusted according to the measurement time interval and the vibration frequency, the vibration frequency is gradually increased, the vibration response of the component to be measured is monitored, and the natural frequency of the component to be measured is identified.

12. The non-contact laser based strain measurement method according to claim 9, characterized in that: The step of calculating the in-plane strain and shear strain of each measuring point based on the displacement components of each measuring point in the preset displacement direction comprises the following steps: Calculating the displacement gradient of each measuring point in the preset displacement direction based on the displacement components of each measuring point in the preset displacement direction obtained by measurement; and Based on the calculated displacement gradient of each measuring point in the preset displacement direction, the in-plane strain and shear strain of each measuring point are calculated.

13. The non-contact laser based strain measurement method according to claim 12, characterized in that: The following steps are also included: Based on the calculated in-plane strain and shear strain of each measuring point, strain field fitting is performed to obtain the three-dimensional strain field distribution on the surface of the component to be measured.

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