A method for establishing a dynamic tensile constitutive model based on 3D-DIC

Abstract

The application discloses a kind of dynamic tensile constitutive model establishment method based on 3D-DIC, belong to material constitutive model field.This method includes: establishing 3D-DIC vibration test system and quasi-static monotonic tensile, compression test system;Obtain damage variable D based on Weibull distribution through quasi-static test;Through 3D-DIC vibration test test, the displacement response, speed response, acceleration response and strain response of test piece are acquired;Vibration response is substituted into Euler-Bernoulli bending vibration equation to calculate dynamic modulus inversely;According to speed response, surface strain rate is calculated;Strain rate statistical parameter C is deduced in combination with damage variable D and dynamic modulus;Finally, nonlinear dynamic constitutive model containing strain rate effect is established.The application adopts 3D-DIC non-contact full-field measurement technology, and quasi-static and dynamic characteristics of material are considered, and the nonlinear mechanical behavior of material under high frequency and high strain rate can be accurately characterized, and is suitable for dynamic constitutive modeling of advanced materials in aerospace.

Description

Technical Field

[0001] This invention relates to the technical field of material constitutive models, and specifically to a method for establishing a dynamic tensile constitutive model based on 3D-DIC. Background Technology

[0002] Aerospace equipment is a core pillar of national scientific and technological strength and defense security. Its service environment is characterized by extreme complexity, strong dynamic load characteristics, and high reliability requirements. Extreme high-temperature, high-frequency vibrations of hot-end components of aero-engines, large deflection dynamic deformation of wings under aerodynamic loads, and complex impact and alternating loads during spacecraft orbital operation all place stringent demands on the dynamic mechanical performance and vibration response control of equipment structures. Dynamic constitutive relations, as the core characterizing the stress-strain response of materials under dynamic loads, directly determine the reliability of vibration response prediction based on their modeling accuracy, thus affecting equipment design optimization, life assessment, and safety assurance. Therefore, it is a core research direction in the field of aerospace structural dynamics.

[0003] Currently, aerospace equipment is undergoing iterative upgrades towards lightweight, high mobility, and long service life. A large number of advanced high-temperature alloys, carbon / carbon composites, and ceramic matrix composites are being widely used. The mechanical behavior of these materials exhibits significant nonlinearity, rate dependence, and environmental sensitivity. Their deformation mechanisms and damage evolution under dynamic loads are far more complex than those of traditional materials, making traditional nonlinear dynamic constitutive models insufficient for high-precision characterization. Furthermore, aerospace structures are often complex thin-walled and curved structures, prone to full-field nonlinear deformation and multimodal coupled vibrations under dynamic loads. During service, they are often exposed to extreme environments such as high temperatures and high-speed airflow, further increasing the difficulty of dynamic constitutive modeling and vibration response prediction.

[0004] Traditional methods for establishing nonlinear dynamic constitutive models have significant limitations, making it difficult to accurately construct the nonlinear dynamic constitutive models required for aerospace equipment. Conventional modeling methods often rely on contact measurement techniques (such as high-temperature extensometers and strain gauges) combined with finite element simulation, resulting in quasi-static constitutive models that can only characterize the mechanical behavior of materials under static or low strain rate loads. These models are not suitable for the high-frequency, high-strain-rate dynamic service conditions of aerospace equipment. Furthermore, current mainstream dynamic constitutive modeling methods often employ the split Hopkinson bar (SHPB) technique, which is mainly applicable to the dynamic compression performance testing of materials. This technique is not suitable for accurately obtaining dynamic mechanical parameters under tensile conditions and cannot effectively characterize the dynamic response law of materials under vibration loads. It is significantly out of sync with the actual mechanical state of aerospace structures during vibration service. Furthermore, contact measurement can only acquire mechanical data from discrete measurement points, failing to capture the dynamic strain distribution across the entire structure. It is also prone to accuracy degradation and component damage under extreme conditions such as ultra-high temperatures and large deformations, making it difficult to meet the measurement needs of hot-end components of aero-engines and complex structures of spacecraft. At the same time, traditional modeling methods are mostly based on empirical formulas or simplified assumptions, which further leads to significant deviations between the established nonlinear dynamic constitutive models and the actual dynamic mechanical behavior of materials. This makes it impossible to accurately describe the nonlinear response characteristics of materials under high-frequency, high-strain-rate loads, and thus difficult to support the design and development of highly reliable aerospace equipment.

[0005] Three-dimensional digital image correlation (3D-DIC) is a non-contact, full-field optical measurement technology with advantages such as simple optical path, strong universality, outstanding anti-interference ability, and wide measurement range. It can realize accurate full-field displacement and strain measurement from millimeter-level to tens of meters-level structures, and from micro-strain to large deformation. It does not require contact with the measured component and can effectively adapt to the dynamic measurement needs of complex structures and extreme service environments of aerospace equipment, making up for the shortcomings of traditional contact measurement technology.

[0006] In summary, the current aerospace field faces several key challenges in establishing nonlinear dynamic constitutive models, including significant limitations in measurement methods, insufficient accuracy in dynamic constitutive modeling, a disconnect between modeling methods and actual service conditions, and an incomplete "measurement-modeling" technology system. Existing technologies struggle to meet the engineering requirements of advanced aerospace equipment for precise characterization of material dynamic mechanical properties, becoming a critical technological bottleneck restricting the improvement of aerospace equipment performance, extension of service life, and operational safety. The 3D-DIC-based nonlinear dynamic constitutive model establishment method leverages the advantages of full-field non-contact measurement in 3D-DIC technology to acquire accurate full-field dynamic strain data of the structure and integrate it into the dynamic constitutive modeling process. This effectively solves the problems of disconnection between nonlinear dynamic constitutive models and actual dynamic conditions, and insufficient modeling accuracy in traditional methods. It significantly improves the characterization accuracy of nonlinear dynamic constitutive models, filling the gap in the aerospace field for integrated "full-field dynamic measurement-high-precision constitutive modeling" technology. This has significant engineering application value and academic research significance for promoting structural design optimization and service safety assurance of aerospace equipment. Summary of the Invention

[0007] This invention provides a method for establishing a dynamic tensile constitutive model based on 3D-DIC, which can establish a nonlinear dynamic constitutive model of materials through 3D-DIC vibration tests and quasi-static monotonic tensile and compression tests.

[0008] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for establishing a nonlinear dynamic constitutive model based on 3D-DIC, characterized by the following steps:

[0010] Step 1: Establish a 3D-DIC vibration testing system to collect the full-field displacement, strain, and acceleration response of the test specimen during the vibration process;

[0011] Step 2: Establish a quasi-static monotonic tensile and compression testing system to obtain the stress-strain relationship of the specimen under quasi-static load;

[0012] Step 3: Conduct the test using the quasi-static monotonic tensile and compression testing system, and calculate the damage variable D of the test specimen based on the Weibull distribution according to the stress-strain curve obtained from the test.

[0013] Step 4: Use the 3D-DIC vibration testing system to conduct vibration tests on the test piece and obtain the vibration response on the surface of the test piece;

[0014] Step 5: Substitute the vibration response obtained in Step 4 into the Euler-Bernoulli bending vibration equation and invert the calculation to obtain the dynamic modulus of the test specimen at the corresponding vibration moment.

[0015] Step 6: Based on the velocity response obtained in Step 4, calculate the surface strain rate of the test specimen at the corresponding vibration moment;

[0016] Step 7: Substitute the damage variable D obtained in Step 3, the dynamic modulus obtained in Step 5, and the surface strain rate obtained in Step 6 into the expression of the nonlinear dynamic constitutive model that includes the strain rate effect, and calculate the strain rate statistical parameter C by reverse calculation.

[0017] Step 8: Substitute the damage variable D obtained in Step 3 and the strain rate statistical parameter C obtained in Step 7 into the nonlinear dynamic constitutive model expression to establish a complete nonlinear dynamic constitutive model of the material.

[0018] To optimize the above technical solution, the specific measures also include:

[0019] The 3D-DIC vibration testing system described in step 1 consists of two 3D high-speed cameras, a 3D-DIC analysis unit, a horizontal vibration table, a light source, a pressure block, and a fixture. The 3D-DIC system is composed of two high-speed cameras with a lens angle of 30°, which are kept horizontal to the shooting surface. The fixture and pressure block are fixed to the horizontal vibration table with bolts, and the fixture is then pressed tightly by the pressure block to ensure a firm grip. Marking light spots are pasted on the surface of the fixture to isolate the displacement generated when the horizontal vibration table is excited. The horizontal vibration table applies acceleration excitation to the test piece. The 3D high-speed camera equipment calibrates the surface of the test piece and measures it using a frame rate 10 times the fundamental frequency of the test piece to obtain a high-speed image of the test piece under frequency sweep. The 3D-DIC analysis unit is connected to the 3D high-speed camera signal to process the high-speed image and obtain the displacement response, velocity response, acceleration response, natural frequency, and strain of the test piece surface.

[0020] The quasi-static monotonic tensile and compression testing system described in step 2 uses an electro-hydraulic servo fatigue testing machine. The electro-hydraulic servo fatigue testing machine uses a high-temperature metal alloy clamp to hold the test piece, uses an extensometer to record the strain change of the test piece, and uses the force actuator and displacement sensor built into the fatigue testing machine to record the force load and displacement of the test piece, and retains the load-displacement curve.

[0021] Step 3 uses the Weibull distribution to calculate the damage variable D of the test specimen. During vibration, the strain is divided into tensile and compressive strains; therefore, the damage variable is also divided into tensile and compressive strains. The damage variable D conforms to the Weibull distribution, as shown in the formula:

[0022]

[0023] In the above formula, The elastic modulus when undamaged. Let a be the yield strength, and b be statistical parameters. Substitute the monotonic tensile and compressive stress-strain curves into the expression for the damage variable D, and solve for the statistical parameters a and b of the tensile damage variable and the compressive damage variable, respectively.

[0024] The specific method of step 4 is as follows: Vibration excitation is applied to the test piece through a horizontal vibration table, and a sweep frequency test is performed on the test piece under acceleration excitation; a 3D high-speed camera acquires high-speed images of the test piece under sweep frequency excitation; the images are processed by a 3D-DIC analysis unit to obtain the displacement time-domain response of the test piece near the root of the fixed end, and the amplitude-frequency curve of the test piece is obtained by FFT transformation to analyze its natural frequency and natural frequency change; at the same time, the strain distribution of the test piece is output, and the maximum strain of the test piece occurs at the root of the fixed end; a 3D-DIC simulated extensometer is used to set a gauge length near the root of the test piece, and the average strain, average displacement and average acceleration in this area are calculated.

[0025] The specific method for step 5 is as follows:

[0026] Consider the test specimen as an Euler-Bernoulli fixed beam, with its axis denoted as the x-axis. The mechanical quantity at the x-axis is denoted as: cross-sectional area. elastic modulus mass density Moment of inertia of the cross section about the neutral axis The time is The bending dynamics equation for an Euler-Bernoulli beam is:

[0027]

[0028] In the above formula, the longitudinal displacement perpendicular to the plate is: External forces that vary with time are distributed along a unit length of the beam. and external torque Considering the test specimen is approximately equal to a beam with a uniform cross-section, substitute the acceleration response... Simplifying the above formula, we get:

[0029]

[0030] The modulus at each moment is considered to be linear, and together they constitute the stress-strain relationship of the material.

[0031] The specific method for step 6 is as follows:

[0032] In the 3D-DIC software settings, the strain within the gauge length measured by the simulated extensometer is the sum of local tensile strain and local compressive strain, hence the following formula:

[0033]

[0034] In the formula, The surface strain rate of the test specimen at the current moment. The change in the distance between the test specimen and the marker at each time point. The relative velocity of the punctuation mark. This is the gauge length. Strain within the gauge length at the current moment.

[0035] The specific method for step 7 is as follows:

[0036] elastic modulus The following relationship exists:

[0037]

[0038] Substituting the strain rate expression formula into the equation, we derive:

[0039]

[0040] In the formula, For standard strain rate, As the damage variable, the relative velocity of the calibrated points under tension on the measurement surface was taken at different frequencies during the frequency sweep test. and the elastic modulus at the corresponding time point calculated in step 5. The statistical parameter C was calculated.

[0041] In step 8, the expression for the nonlinear dynamic constitutive model of the material is:

[0042]

[0043] In the formula, For stress, This is the elastic modulus of the material when it is undamaged.

[0044] The present invention has the following beneficial effects:

[0045] 1. This invention employs 3D-DIC non-contact full-field optical measurement technology, avoiding the accuracy degradation and component damage problems of traditional contact measurements under extreme conditions, and is suitable for extreme service environments in aerospace. It can achieve the acquisition of mechanical parameters such as displacement and strain across the entire domain, capture the nonlinear deformation characteristics of materials across the entire field, and combine high-precision calibration with quasi-static testing, resulting in significantly lower errors than traditional empirical fitting methods.

[0046] 2. This invention innovatively adopts a quasi-static tensile testing + 3D-DIC vibration testing mode, taking into account both the quasi-static and dynamic characteristics of materials and considering the dual damage mechanism of tension and compression. The model parameters are all derived from measured data without any simplification assumptions, and incorporate the strain rate effect, which can accurately characterize the mechanical behavior of materials under high frequency and high strain rate, solving the problems of traditional models being out of touch with actual working conditions and insufficient fitting accuracy.

[0047] 3. The testing system of this invention consists of conventional equipment, with a simple optical path and convenient installation. The standardized fixture design is adaptable to various flat test pieces, eliminating the need for complex specialized equipment and reducing testing costs and operational difficulty. The 3D-DIC software automatically processes data, with a standardized modeling process and strong repeatability. It is compatible with various new materials in the aerospace field and can effectively characterize their nonlinearity, rate correlation, and other properties, demonstrating a versatility far superior to traditional modeling methods. Attached Figure Description

[0048] Figure 1 This is a flowchart illustrating the method for establishing a nonlinear dynamic constitutive model based on 3D-DIC according to the present invention.

[0049] Figure 2 This is a graph showing the change of damage variable D as a function of yield strength for the 2D-SiC / SiC composite material in an embodiment of the present invention.

[0050] Figure 3 This is a stress-strain curve of the 2D-SiC / SiC composite material in an embodiment of the present invention. Detailed Implementation

[0051] This implementation example Figure 1 As shown, the 2D-SiC / SiC continuous fiber reinforced ceramic matrix composite material prepared by chemical vapor infiltration (CVI) is used as an example for illustration.

[0052] The material is prepared by two-dimensional plain weave SiC preform, BN interface layer deposition, and SiC matrix deposition by interlacing the warp and weft yarns along the 0° and 90° directions respectively.

[0053] I. Establishing a testing system

[0054] Step 1: Establish a 3D-DIC vibration testing system.

[0055] The 3D-DIC vibration testing system consists of two 3D high-speed cameras, a 3D-DIC analysis unit, a horizontal vibration table, a light source, a pressure block, and fixtures.

[0056] Two high-speed cameras are symmetrically arranged with a lens angle of 30°. The distance between the two cameras is 15cm, and the lens planes of the two cameras are kept horizontal to the shooting surface of the test piece. The working distance is 50cm.

[0057] The fixture and pressure block are fixedly installed on the horizontal vibration table surface by bolts. The test piece is pressed onto the fixture by the pressure block to achieve clamping and fixation.

[0058] Marking dots are pasted on the surface of the fixture to peel off the displacement generated when the horizontal vibration table is excited.

[0059] The light source uses high-power LED lamps to provide uniform illumination to the test area, ensuring image clarity and contrast.

[0060] The sampling frame rate of the 3D high-speed camera is set to 5000fps, and the system calibration reprojection error is less than 0.03 pixels to ensure the accuracy of 3D coordinate reconstruction.

[0061] Step 2: Establish a quasi-static monotonic tensile and compression test system.

[0062] Quasi-static tests were conducted using an electro-hydraulic servo fatigue testing machine. This equipment can provide a maximum load of 100kN, a maximum displacement stroke of 50mm, and a load accuracy of 0.5%.

[0063] The test specimen was clamped using a high-temperature metal alloy fixture, and the strain changes of the test specimen were recorded using an extensometer.

[0064] Using the force actuator and displacement sensor built into the fatigue testing machine, the force load and displacement of the test piece are recorded, and the load-displacement curve is retained.

[0065] II. Obtaining Damage Variables through Quasi-Static Testing

[0066] Step 3: Obtain the damage variable D through quasi-static monotonic tensile and compression tests.

[0067] Quasi-static monotonic tensile and compression tests were conducted on 2D-SiC / SiC composite specimens.

[0068] Based on the stress-strain curves obtained from the experiment, the damage variable D is calculated using the Weibull distribution.

[0069] During vibration, strain is divided into tensile strain and compressive strain, and the damage variable is also divided into tensile and compressive strain.

[0070] The damage variable D follows a Weibull distribution, expressed as:

[0071]

[0072] In the above formula, The elastic modulus when undamaged. Let a be the yield strength, and b be statistical parameters. Substitute the monotonic tensile and compressive stress-strain curves into the expression for the damage variable D, and solve for the statistical parameters a and b of the tensile damage variable and the compressive damage variable, respectively.

[0073] Since the measurement method of the 3D-DIC simulated extensometer can be regarded as measuring the surface strain of the material, the essence of bending deformation is that the material in different regions of the cross section is subjected to uniaxial tension or uniaxial compression respectively. Therefore, the surface deformation under quasi-static conditions can be simplified to tension and compression based on the uniaxial tension and compression stress-strain relationship.

[0074] Substitute the monotonic stretching data. The Pa value is 195.58 GPa. Given a stress of 197.2 MPa, we can calculate that a is approximately 0.152 and b is approximately 0.326. Substituting the strain after yield strength into the formula, the relationship between damage variable and stress-strain is as follows: Figure 2 and Figure 3 As shown.

[0075] Similarly, statistical parameters under compression can be obtained through quasi-static compression tests.

[0076] III. Obtaining Dynamic Response through Vibration Testing

[0077] Step 4: Obtain the vibration response of the material surface through 3D-DIC vibration testing.

[0078] The test specimen is subjected to vibration excitation by a horizontal vibration table, and a sweep frequency test under acceleration excitation is performed on the plate test specimen.

[0079] Set the sampling frequency of the 3D high-speed camera to 10 times the fundamental frequency of the test piece, and set the sweep speed of the vibration table.

[0080] The image is processed by the 3D-DIC analysis unit to obtain the displacement time-domain response of the test piece at a preset distance from the fixed end, and its amplitude-frequency curve is obtained by FFT transformation to analyze its natural frequency and natural frequency change.

[0081] The 3D-DIC output shows the strain distribution of the test specimen, with the maximum strain occurring at the root of the fixed end.

[0082] Using a 3D-DIC simulation extensometer, a gauge length is set near the root of the specimen to calculate the average strain, average displacement, and average acceleration in that region.

[0083] IV. Inversion Calculation of Dynamic Modulus

[0084] Step 5: Substitute the obtained vibration response into Bernoulli's bending vibration equation to obtain the modulus at the corresponding time.

[0085] Consider the plate component as an Euler-Bernoulli fixed beam, with its axis denoted as the x-axis. The mechanical quantity at the x-axis is denoted as: cross-sectional area. elastic modulus mass density Moment of inertia of the cross section about the neutral axis The time is The bending dynamics equation for an Euler-Bernoulli beam is:

[0086]

[0087] In the above formula, the longitudinal displacement perpendicular to the plate is: External forces that vary with time are distributed along a unit length of the beam. and external torque Considering the test specimen is approximately equal to a beam with a uniform cross-section, substitute the acceleration response... Simplifying the above formula, we get:

[0088]

[0089] Based on the aforementioned longitudinal displacement and acceleration responses, as well as the known material density, moment of inertia, external force response, and cross-sectional area, the dynamic elastic modulus of the 2D-SiC / SiC composite material at each moment can be obtained. .

[0090] The modulus at each moment is considered to be linear, and together they constitute the stress-strain relationship of the material.

[0091] V. Calculation of surface strain rate

[0092] Step 6: Calculate the surface strain rate at that moment using the velocity response.

[0093] Similar to traditional extensometers, in the 3D-DIC software settings, the strain within the gauge length measured by the simulated extensometer is local tensile strain and local compressive strain.

[0094] Therefore, the formula is as follows:

[0095]

[0096] In the formula, The surface strain rate of the test specimen at the current moment. The change in the distance between the test specimen and the marker at each time point. The relative velocity is the punctuation mark.

[0097] VI. Inversely deduce the statistical parameter C and establish a constitutive model

[0098] Step 7: Calculate the statistical parameter C by back-calculating the modulus at this moment.

[0099] The nonlinear dynamic constitutive model of materials can be written as:

[0100]

[0101] In the formula, For stress, This is the elastic modulus of the material when it is undamaged. For standard strain rate, For damage variables.

[0102] elastic modulus In the calculation, the tension and compression zone is already in the moment of inertia of the section. Since it is already reflected, it does not need to be reflected separately. The following relationship exists:

[0103]

[0104] Substituting the strain rate expression formula into the equation, we derive:

[0105]

[0106] The relative velocities of the caliber points under tension were measured at 180Hz, 190Hz, 200Hz, and 210Hz respectively during the frequency sweep test. (Take the maximum strain value) and calculate the elastic modulus at that moment. Substituting the values ​​into the formula above, the statistical parameter C is approximately 0.27.

[0107] Step 8: Obtain the nonlinear dynamic constitutive model of the material.

[0108] Substitute the damage variable D (including tensile and compressive damage variables) obtained in step 3 and the strain rate statistical parameter C obtained in step 7 into the nonlinear dynamic constitutive model expression to establish a complete nonlinear dynamic constitutive model of the material:

[0109]

[0110] All parameters have been determined through the steps described above. This completes the establishment of the nonlinear dynamic constitutive model based on 3D-DIC.

[0111] This model can accurately characterize the nonlinear mechanical behavior of 2D-SiC / SiC composite materials under high-frequency, high-strain-rate dynamic loads.

[0112] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention.

[0113] For those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for establishing a nonlinear dynamic constitutive model based on 3D-DIC, characterized in that, Includes the following steps: Step 1: Establish a 3D-DIC vibration testing system to collect the full-field displacement, strain, and acceleration response of the test specimen during the vibration process; Step 2: Establish a quasi-static monotonic tensile and compression testing system to obtain the stress-strain relationship of the specimen under quasi-static load; Step 3: Conduct the test using the quasi-static monotonic tensile and compression testing system, and calculate the damage variable D of the test specimen based on the Weibull distribution according to the stress-strain curve obtained from the test. Step 4: Use the 3D-DIC vibration testing system to conduct vibration tests on the test piece and obtain the vibration response on the surface of the test piece; Step 5: Substitute the vibration response obtained in Step 4 into the Euler-Bernoulli bending vibration equation and invert the calculation to obtain the dynamic modulus of the test specimen at the corresponding vibration moment. Step 6: Based on the velocity response obtained in Step 4, calculate the surface strain rate of the test specimen at the corresponding vibration moment; Step 7: Substitute the damage variable D obtained in Step 3, the dynamic modulus obtained in Step 5, and the surface strain rate obtained in Step 6 into the expression of the nonlinear dynamic constitutive model that includes the strain rate effect, and calculate the strain rate statistical parameter C by reverse calculation. Step 8: Substitute the damage variable D obtained in Step 3 and the strain rate statistical parameter C obtained in Step 7 into the nonlinear dynamic constitutive model expression to establish a complete nonlinear dynamic constitutive model of the material.

2. The method for establishing a nonlinear dynamic constitutive model based on 3D-DIC according to claim 1, characterized in that, The 3D-DIC vibration testing system described in step 1 consists of two 3D high-speed cameras, a 3D-DIC analysis unit, a horizontal vibration table, a light source, a pressure block, and a fixture. The 3D-DIC system is composed of two high-speed cameras with a lens angle of 30°, which are kept horizontal to the shooting surface. The fixture and pressure block are fixed to the horizontal vibration table with bolts, and the fixture is then pressed tightly by the pressure block to ensure a firm grip. Marking light spots are pasted on the surface of the fixture to isolate the displacement generated when the horizontal vibration table is excited. The horizontal vibration table applies acceleration excitation to the test piece. The 3D high-speed camera equipment calibrates the surface of the test piece and measures it using a frame rate 10 times the fundamental frequency of the test piece to obtain a high-speed image of the test piece under frequency sweep. The 3D-DIC analysis unit is connected to the 3D high-speed camera signal to process the high-speed image and obtain the displacement response, velocity response, acceleration response, natural frequency, and strain of the test piece surface.

3. The method for establishing a nonlinear dynamic constitutive model based on 3D-DIC according to claim 1, characterized in that, The quasi-static monotonic tensile and compression testing system described in step 2 uses an electro-hydraulic servo fatigue testing machine. The electro-hydraulic servo fatigue testing machine uses a high-temperature metal alloy clamp to hold the test piece, uses an extensometer to record the strain change of the test piece, and uses the force actuator and displacement sensor built into the fatigue testing machine to record the force load and displacement of the test piece, and retains the load-displacement curve.

4. The method for establishing a nonlinear dynamic constitutive model based on 3D-DIC according to claim 1, characterized in that, Step 3 uses the Weibull distribution to calculate the damage variable D of the test specimen. During vibration, the strain is divided into tensile and compressive strains; therefore, the damage variable is also divided into tensile and compressive strains. The damage variable D conforms to the Weibull distribution, as shown in the formula: In the above formula, The elastic modulus when undamaged. Let a be the yield strength, and b be statistical parameters. Substitute the monotonic tensile and compressive stress-strain curves into the expression for the damage variable D, and solve for the statistical parameters a and b of the tensile damage variable and the compressive damage variable, respectively.

5. The method for establishing a nonlinear dynamic constitutive model based on 3D-DIC according to claim 1, characterized in that, The specific method of step 4 is as follows: Vibration excitation is applied to the test piece through a horizontal vibration table, and a sweep frequency test is performed on the test piece under acceleration excitation; a 3D high-speed camera acquires high-speed images of the test piece under sweep frequency excitation; the images are processed by a 3D-DIC analysis unit to obtain the displacement time-domain response of the test piece near the root of the fixed end, and the amplitude-frequency curve of the test piece is obtained by FFT transformation to analyze its natural frequency and natural frequency change; at the same time, the strain distribution of the test piece is output, and the maximum strain of the test piece occurs at the root of the fixed end; a 3D-DIC simulated extensometer is used to set a gauge length near the root of the test piece, and the average strain, average displacement and average acceleration in this area are calculated.

6. The method for establishing a nonlinear dynamic constitutive model based on 3D-DIC according to claim 1, characterized in that, The specific method for step 5 is as follows: Consider the test specimen as an Euler-Bernoulli fixed beam, with its axis denoted as the x-axis. The mechanical quantity at the x-axis is denoted as: cross-sectional area. elastic modulus mass density Moment of inertia of the cross section about the neutral axis The time is The bending dynamics equation for an Euler-Bernoulli beam is: In the above formula, the longitudinal displacement perpendicular to the plate is: External forces that vary with time are distributed along a unit length of the beam. and external torque Considering that the plate is approximately equal to a beam with a uniform cross-section, substitute the acceleration response. Simplifying the above formula, we get: The modulus at each moment is considered to be linear, and together they constitute the stress-strain relationship of the material.

7. The method for establishing a nonlinear dynamic constitutive model based on 3D-DIC according to claim 1, characterized in that, The specific method for step 6 is as follows: In the 3D-DIC software settings, the strain within the gauge length measured by the simulated extensometer is the sum of local tensile strain and local compressive strain, hence the following formula: In the formula, The surface strain rate of the test specimen at the current moment. The change in the distance between the test specimen and the marker at each time point. The relative velocity of the punctuation mark. This is the gauge length. Strain within the gauge length at the current moment.

8. The method for establishing a nonlinear dynamic constitutive model based on 3D-DIC according to claim 1, characterized in that, The specific method for step 7 is as follows: elastic modulus The following relationship exists: Substituting the strain rate expression formula into the equation, we derive: In the formula, For standard strain rate, As the damage variable, the relative velocity of the calibrated points under tension on the measurement surface was taken at different frequencies during the frequency sweep test. and the elastic modulus at the corresponding time point calculated in step 5. The statistical parameter C was calculated.

9. The method for establishing a nonlinear dynamic constitutive model based on 3D-DIC according to claim 8, characterized in that, In step 8, the expression for the nonlinear dynamic constitutive model of the material is: In the formula, For stress, This is the elastic modulus of the material when it is undamaged.

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