Metering calibration device of high-accuracy 3D speckle measurement system

Abstract

The utility model provides a metering calibration device of a high-accuracy 3D speckle measurement system. The metering calibration device comprises a standard strain piece, a loading mechanism, a standard strain gauge, a strain demodulator, a data processing system, an industrial personal computer and a calibrated 3D speckle measurement system, a central positioning hole is formed in the bottom of the standard strain piece, and a cuboid columnar part with a speckle pattern sprayed on the outer surface is arranged in the middle of the standard strain piece; a load applied by the loading mechanism acts on the top end of the standard strain piece, and the top end of the standard strain piece is also provided with a component for uniformly distributing the load; the standard strain gauge is attached to the central position of the outer surface of the cuboid columnar part; the standard strain gauge is connected with the strain demodulator, the calibrated 3D speckle measurement system and the strain demodulator are both connected with the data processing system, and the data processing system is connected with the industrial personal computer. According to the utility model, standard three-dimensional static and dynamic strain tests in a full range can be provided, and wide-range calibration can be efficiently and accurately carried out on the calibrated 3D speckle measurement system.

Description

Technical Field

[0001] The utility model relates to the technical field of 3D speckle measurement system calibration, in particular to a metrological calibration device for a high-accuracy 3D speckle measurement system. Background Art

[0002] Full-field strain measurement is an essential measurement method in R&D, production, and testing across a wide range of industries, including automotive, aviation, biomedical, new energy, and new materials. With technological advancements, traditional measurement methods using strain gauges and contact sensors are gradually being replaced by non-contact, cross-scale, and digital measurement methods. Among these, 3D digital speckle pattern measurement (3D-Digital Image Correlation) is currently the most technologically advanced and highly accurate non-contact measurement method. Its unique feature is that, without contacting the test piece, a measurement camera identifies speckle patterns on the surface of the test piece, enabling rapid and comprehensive acquisition of spatial displacement and strain data. Compared to traditional contact measurement, this measurement system offers more accurate results, higher efficiency, and enhanced immunity to electromagnetic interference. As a measurement tool, a 3D digital speckle pattern measurement system must possess accurate metrological traceability; otherwise, measurement accuracy cannot be guaranteed. Currently, two calibration methods and devices are commonly used. The first method involves calibration with reference to a standard strain gauge. This method has several drawbacks, including inaccurate calculations of the strains of equal-strength beams, unstable loading control, and an inability to generate full-field three-dimensional standard strains. The second method involves using standard specimens, such as steps, grids, and triaxial standard plates, to first determine the three coordinates and then use them as a standard for calibration. However, this calibration method is limited by the shape, size, and accuracy of the standard, making it impossible to perform continuous calibration across the entire measurement range and achieving cross-scale and cross-parameter coverage of system parameters. Currently, there is a lack of effective metrological calibration devices to ensure the accuracy of 3D speckle measurement systems. Utility Model Content

[0003] The technical problem to be solved by the present invention is to provide a metrological calibration device for a high-accuracy 3D speckle measurement system, which can accurately calibrate the 3D digital speckle measurement system over a wide range.

[0004] The utility model is achieved in this way:

[0005] The utility model provides a metrological calibration device for a high-accuracy 3D speckle measurement system, comprising a standard strain gauge, a loading mechanism, a standard strain gauge, a strain demodulator, a data processing system, an industrial computer, and a calibrated 3D speckle measurement system;

[0006] The standard strain gauge has a central positioning hole at its bottom and a rectangular columnar portion in its middle, with a speckle pattern sprayed on its outer surface. The load applied by the loading mechanism acts on the top of the standard strain gauge, which also has a component for evenly distributing the load. The calibrated 3D speckle measurement system is used to identify changes in the speckle pattern before and after the load is applied.

[0007] The standard strain gauge is attached to the center of the outer surface of the rectangular columnar portion and is used to monitor whether the load applied by the loading mechanism is unbalanced. The standard strain gauge is T-shaped.

[0008] The standard strain gauge is connected to the strain demodulator, the calibrated 3D speckle measurement system and the strain demodulator are both connected to the data processing system, and the data processing system is connected to the industrial computer.

[0009] Furthermore, the loading mechanism is a force standard machine, a ball head is provided on the top of the standard strain member, the ball head is connected to a ball bowl, and the load of the force standard machine is applied to the ball bowl.

[0010] Furthermore, a vibration table is included, the standard strain gauge is placed on top of the vibration table, the loading mechanism is a standard mass block, the standard mass block is rigidly connected to the top of the standard strain gauge and is coaxial with the standard strain gauge, and an acceleration sensor is arranged above the standard mass block;

[0011] The acceleration sensor is connected to the data processing system.

[0012] Furthermore, a fixing screw hole is provided at the center of the top of the standard strain member, and a stud is provided at the center of the bottom of the standard mass block, and the stud is spirally connected to the fixing screw hole.

[0013] Furthermore, the acceleration sensor is magnetically attracted to the top of the standard mass block.

[0014] Furthermore, the cross-sections of the upper and lower ends of the standard strain gauge are circular, and the cross-section of the rectangular columnar portion is square.

[0015] The advantages of the present invention are:

[0016] 1. The ball head at the top of the standard strain gauge cooperates with the ball bowl, or the standard mass block and the standard strain gauge are rigidly connected coaxially, ensuring that the load can act evenly and coaxially on the standard strain gauge, avoiding strain distortion caused by uneven load distribution. The central positioning hole at the bottom improves the positioning accuracy of the standard strain gauge installation.

[0017] 2. The loading mechanism can flexibly apply different loads according to needs. The standard strain gauge can generate stable and repeatable strain within a wide load range, breaking through the narrow calibration range problem caused by the shape and size limitations of traditional standards. It can meet the full-range calibration requirements of the 3D digital speckle measurement system in different measurement scenarios, truly realizing wide-range and continuous calibration coverage.

[0018] 3. The standard strain gauge with a T-shaped structure can monitor whether the load is biased in real time, ensuring the uniformity and stability of the strain distribution during loading, and reducing the calibration error caused by load offset from the source.

[0019] 4. Through the flexible configuration of two loading mechanisms, this device can not only achieve precise calibration under static loads with the help of a force standard machine, but also simulate dynamic load environments through the combination of a vibration table and a standard mass block, meeting the calibration requirements of the 3D speckle measurement system in dynamic measurement scenarios and expanding the scope of application of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Figure 1 This is a schematic structural diagram of a metrology calibration device for a high-accuracy 3D speckle measurement system in the present invention during static calibration.

[0022] Figure 2 This is a schematic diagram of the explosion structure of the standard strain gauge connected to the ball bowl in the present invention.

[0023] Figure 3 This is a schematic diagram of the standard strain gauge structure in this utility model. Figure 1 .

[0024] Figure 4 This is a structural diagram of a metrology calibration device of a high-accuracy 3D speckle measurement system in the present invention during dynamic calibration.

[0025] Figure 5 This is a schematic diagram of the explosion structure in which the vibration table, standard strain gauge and standard mass block are connected in the present invention.

[0026] Figure 6 This is a schematic diagram of the standard strain gauge structure in this utility model. Figure 2 .

[0027] Description of the numbers in the figure:

[0028] 1. Standard strain gauge; 11. Center positioning hole; 12. Rectangular column; 13. Measurement area; 14. Ball head; 15. Ball bowl; 16. Fixing screw hole; 2. Standard strain gauge; 3. Strain demodulator; 4. Data processing system; 5. Industrial computer; 6. Calibrated 3D speckle measurement system; 7. Force standard machine; 8. Vibration table; 9. Standard mass block; 91. Stud; 10. Accelerometer. DETAILED DESCRIPTION

[0029] See also Figures 1 to 6 The utility model provides a metrological calibration device for a high-accuracy 3D speckle measurement system, comprising a standard strain gauge 1, a loading mechanism, a standard strain gauge 2, a strain demodulator 3, a data processing system 4, an industrial computer 5, and a calibrated 3D speckle measurement system 6;

[0030] The standard strain gauge 1 is made of a metal material (such as 45 steel or 40Cr). A center positioning hole 11 is provided at the bottom of the standard strain gauge 1. A rectangular columnar portion 12 is provided in the middle of the standard strain gauge 1. A speckle pattern (not shown) is sprayed on the outer surface of the rectangular columnar portion 12. The center area of ​​the surface of the rectangular columnar portion 12 serves as the measurement area 13 of the calibrated 3D speckle measurement system 6.

[0031] The load applied by the loading mechanism acts on the top of the standard strain gauge 1, which also has a component that evenly distributes the load. During static calibration, the component that evenly distributes the load consists of a ball head 14 and a ball bowl 15; by applying the load to the ball bowl 15 and ball head 14, the load applied to the standard strain gauge 1 is more evenly distributed. During dynamic calibration, the component that evenly distributes the load is a stud 91 located at the bottom center of the standard mass block 9. By providing stud 91, the center of the standard mass block 9 coincides with the axis of the standard strain gauge 1, thereby evenly distributing the weight of the standard mass block 9 at the top of the standard strain gauge 1.

[0032] The calibrated 3D speckle measurement system 6 is used to identify changes in speckle patterns before and after load application; specifically, the calibrated 3D speckle measurement system 6 measures the strain at the center positions of two adjacent rectangular surfaces.

[0033] The standard strain gauge 2 is attached to the center of the outer surface of the rectangular columnar portion 12 and is used to monitor whether the load applied by the loading mechanism is unbalanced. The standard strain gauge 2 is T-shaped; the standard strain gauge 2 is divided into two parts, extending in the horizontal and vertical directions respectively, and is used to monitor the displacement and stress of the standard strain piece 1 under the load state, and to determine whether the load is unbalanced, resulting in uneven strain distribution and distortion of the standard sample.

[0034] The standard strain gauge 2 is connected with a strain demodulator 3, the calibrated 3D speckle measurement system 6 and the strain demodulator 3 are connected with a data processing system 4, and the data processing system 4 is connected with an industrial computer 5. The industrial computer 5 is also connected with the calibrated 3D speckle measurement system 6, and is used for controlling start and stop of testing of the calibrated 3D speckle measurement system 6.

[0035] In the utility model, the data processing system 4 is used for making conditioning and analysis processing to signals of the strain demodulator 3, the calibrated 3D speckle measurement system 6, the force standard machine 7 and the acceleration sensor 10, and the processed signals are fed back to the industrial computer 5.

[0036] Specifically, in static calibration, the loading mechanism is the force standard machine 7, the force standard machine 7 is loaded or unloaded gradually to provide standard load. The standard load is applied to the top end of the standard strain piece 1. The top end of the standard strain piece 1 is provided with a ball head 14, the ball head 14 is located at the central position of the top end of the standard strain piece 1, the top end of the ball head 14 is a spherical surface, the ball head 14 is connected with a ball bowl 15, and the load of the force standard machine 7 is applied to the ball bowl 15. By applying the load to the ball bowl 15 and the ball head 14, the load applied to the standard strain piece 1 is more uniformly distributed. The industrial computer 5 is also connected with the force standard machine 7, and is used for controlling the loading and unloading actions of the force standard machine 7.

[0037] Specifically, in dynamic calibration, a vibration table 8 is further included, the standard strain piece 1 is arranged on the top of the vibration table 8, the loading mechanism is a standard mass block 9, the standard mass block 9 is rigidly connected to the top end of the standard strain piece 1 and coaxial with the standard strain piece 1, and an acceleration sensor 10 is arranged above the standard mass block 9.

[0038] The acceleration sensor 10 is connected with the data processing system 4. The industrial computer 5 is also connected with the vibration table 8, and is used for controlling vibration of the vibration table 8.

[0039] The standard mass block 9 and the vibration table 8 can provide a series of standard dynamic loads of sine type with different frequencies, different amplitudes and different phases, and further generate a series of standard three-dimensional dynamic strains with different frequencies, different amplitudes and different phases on the standard strain piece 1.

[0040] Specifically, a fixing screw hole 16 is arranged at the central position of the top end of the standard strain piece 1, a stud 91 is arranged at the central position of the bottom of the standard mass block 9, and the stud 91 is screw-connected in the fixing screw hole 16. By arranging the stud 91, the center of the standard mass block 9 is coincided with the axis of the standard strain piece 1, so that the weight of the standard mass block 9 is uniformly distributed on the top end of the standard strain piece 1.

[0041] Specifically, the acceleration sensor 10 is magnetically attracted to the top end of the standard mass block 9.

[0042] Specifically, the cross-sections of the upper and lower ends of the standard strain gauge 1 are circular, and the cross-section of the rectangular columnar portion 12 is square, with a side length of b.

[0043] A specific application of the present invention is:

[0044] (1) Static calibration

[0045] like Figure 1 As shown, after the outer side of the rectangular columnar portion 12 is sprayed with a speckle pattern, the standard strain gauge 1 is placed in a force standard machine 7 to apply a load. The force standard machine 7 provides a series of tensile and compressive bidirectional static loading standard loads, thereby generating a series of standard static strains on the standard strain gauge 1.

[0046] The standard static strain of the standard strain gauge 1 is: ; ; ;

[0047] Where, is the axial normal strain along the direction of force F; and when F is a tensile force, is positive, F is pressure, is negative;

[0048] and is the lateral normal strain of contraction or expansion perpendicular to the direction of force F;

[0049] F is the standard force value applied by the force standard machine 7;

[0050] E is the elastic modulus of the material of the standard strain gauge 1;

[0051] ν is the Poisson's ratio of the material of the standard strain gauge 1;

[0052] The cross section of the rectangular parallelepiped columnar portion 12 is a square, and the side length thereof is b.

[0053] After the force standard machine 7 is loaded, the strain demodulator 3 transmits the monitoring results and the standard force value applied by the force standard machine 7 to the industrial computer 5 after processing by the data processing system 4. Furthermore, the calibrated 3D speckle measurement system 6 captures the changes in the speckle pattern in the measurement area 13 of the standard strain gauge 1, calculates the strain data in this area by identifying the speckle displacement, and feeds the measured data back to the data processing system 4. After signal conditioning and analysis, the data processing system 4 transmits the data to the industrial computer 5.

[0054] The industrial computer 5 compares and calculates the measurement data of the calibrated 3D speckle measurement system 6 with the standard strain of the measurement area 13 of the standard strain member 1 , and finally completes the error correction of the calibrated 3D speckle measurement system 6 .

[0055] A series of standard loads are provided by the force standard machine 7 to calibrate the 3D digital speckle measurement system 6 in a wide range. The load is applied uniformly and coaxially on the standard strain gauge 1 through the bottom center positioning hole 11 of the standard strain gauge 1, the ball head at the top end of the standard strain gauge 1, and the standard strain gauge 2, avoiding strain distortion caused by uneven load distribution and improving the accuracy of calibration.

[0056] (2) Dynamic calibration

[0057] As shown in Figure 4 , the standard strain gauge 1 is placed on the vibration table 8 after the outer side of the cuboid columnar part 12 is sprayed with a speckle pattern, and the vibration table 8 provides a sinusoidal excitation. The standard mass block 9 is rigidly connected above the standard strain gauge 1, and the standard mass block 9 can be monitored by the standard strain gauge 2. The acceleration sensor 10 is magnetically attracted above the standard mass block 9, and under the sinusoidal excitation provided by the vibration table 8, the standard strain gauge 1 generates a standard three-dimensional dynamic strain.

[0058] The standard three-dimensional dynamic strain is: ; ; ;

[0059] In the formula,

[0060] a is the acceleration, which is measured by the acceleration sensor 10;

[0061] The strain at the measurement area 13 in the middle of the standard strain gauge 1 measured by the calibrated 3D digital speckle measurement system, therefore, the value of m is only calculated for the total mass above the center line of the standard strain gauge 1, i.e. m is the total mass of the acceleration sensor 10, the standard mass block 9 and the upper half of the standard strain gauge 1, which can be measured by a balance.

[0062] The strain at the measurement area 13 of the standard strain gauge 1 is measured by the calibrated 3D digital speckle measurement system 6, and the measurement data is fed back to the data processing system 4. After signal conditioning and analysis by the data processing system 4, it is transmitted to the industrial computer 5.

[0063] The industrial computer 5 compares and calculates the measurement data of the calibrated 3D digital speckle measurement system 6 with the standard strain of the measurement area 13 of the standard strain gauge 1, and finally completes the error correction of the calibrated 3D digital speckle measurement system 6.

[0064] The advantages of this utility model are that it can provide a series of standard loads for bidirectional static loading in tension and compression, thereby generating a series of standard static strains on the standard strain gauge 1. Simultaneously, the standard mass block 9 and vibration table 8 can provide a series of sinusoidal standard dynamic loads of varying frequencies, amplitudes, and phases, thereby generating a series of standard strains of varying frequencies, amplitudes, and phases on the standard strain gauge 1. During testing, the calibrated 3D speckle pattern measurement system 6 can simulate its actual operating conditions and perform multi-point calibration of the static and dynamic series of standard strains on the standard strain gauge 1 at varying distances from the standard strain gauge 1, thereby generating a large amount of test data. By comparing the strain values ​​of the calibrated 3D digital speckle pattern measurement system with those of the standard, static and dynamic calibration of the calibrated 3D speckle pattern measurement system 6 is achieved across its full range.

[0065] Although the specific implementation methods of the present invention are described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A metrological calibration device for a high-accuracy 3D speckle measurement system, characterized by: It includes standard strain gauges, loading mechanism, standard strain gauges, strain demodulator, data processing system, industrial computer and calibrated 3D speckle measurement system; The standard strain gauge has a central positioning hole at its bottom and a rectangular columnar portion in its middle, with a speckle pattern sprayed on its outer surface. The load applied by the loading mechanism acts on the top of the standard strain gauge, which also has a component for evenly distributing the load. The calibrated 3D speckle measurement system is used to identify changes in the speckle pattern before and after the load is applied. The standard strain gauge is attached to the center of the outer surface of the rectangular columnar portion and is used to monitor whether the load applied by the loading mechanism is unbalanced. The standard strain gauge is T-shaped. The standard strain gauge is connected to the strain demodulator, the calibrated 3D speckle measurement system and the strain demodulator are both connected to the data processing system, and the data processing system is connected to the industrial computer.

2. The metrological calibration device for a high-accuracy 3D speckle measurement system according to claim 1, wherein: The loading mechanism is a force standard machine. A ball head is provided on the top of the standard strain member. The ball head is connected to a ball bowl. The load of the force standard machine is applied to the ball bowl.

3. The metrological calibration device for a high-accuracy 3D speckle measurement system according to claim 1, wherein: The device further comprises a vibration table, wherein the standard strain gauge is placed on top of the vibration table, the loading mechanism is a standard mass block, the standard mass block is rigidly connected to the top of the standard strain gauge and is coaxial with the standard strain gauge, and an acceleration sensor is arranged above the standard mass block; The acceleration sensor is connected to the data processing system.

4. The metrology calibration device for a high-accuracy 3D speckle measurement system according to claim 3, wherein: A fixing screw hole is provided at the center of the top of the standard strain member, and a stud is provided at the center of the bottom of the standard mass block. The stud is spirally connected in the fixing screw hole.

5. The metrological calibration device for a high-accuracy 3D speckle measurement system according to claim 3, wherein: The acceleration sensor is magnetically attracted to the top of the standard mass block.

6. The metrological calibration device for a high-accuracy 3D speckle measurement system according to claim 1, wherein: The cross sections of the upper and lower ends of the standard strain gauge are circular, and the cross section of the rectangular columnar portion is square.

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