High temperature in-situ visualizing loading device and method based on digital image correlation

Abstract

This invention relates to the field of high-temperature material mechanical analysis technology, and in particular to a high-temperature in-situ visual loading device and method based on digital image correlation, comprising a furnace unit, a photography unit, and a fixture unit; the furnace unit has a viewing window, and the photography unit is used to acquire images; the fixture unit includes a fixture body, a displacement input component, and a compliant loading component; in this invention, by simultaneously covering the sample and the compliant loading component with the field of view of the photography unit, the traditionally invisible load state is transformed into the visible deformation of the compliant component, realizing in-situ optical characterization of the loading process, eliminating the need to install force sensors in the high-temperature region, avoiding high-temperature drift and equipment costs; secondly, the predictable elastic deformation of the compliant loading component can absorb additional displacements caused by high-temperature thermal expansion, transmission clearance, and assembly errors, making the loading on the sample more stable and reducing the risk of impact and overload.

Description

Technical Field

[0001] This invention relates to the field of high-temperature material mechanical analysis technology, and in particular to a high-temperature in-situ visualization loading device and method based on digital image correlation. Background Technology

[0002] High-temperature materials, such as refractories, ceramics, and their composites, often face thermo-mechanical-chemical coupling effects when in service in fields such as metallurgy and aerospace. Accurately obtaining their high-temperature mechanical behavior is crucial for material design and life assessment. Digital image correlation (DIC) technology, as a non-contact, full-field deformation measurement method, has been gradually introduced into the field of high-temperature testing.

[0003] However, existing high-temperature loading devices and DIC observation systems are mostly designed independently: the loading mechanism is responsible for applying loads or displacements, while the DIC system only records the deformation of the sample surface. This separate structure leads to the following problems: First, traditional solutions rely on high-temperature force sensors to obtain the load, but these sensors are prone to drift and have poor stability under strong thermal radiation and prolonged high temperatures, and are also costly; Second, thermal expansion, transmission clearance, and assembly errors in the loading path are difficult to quantify under high-temperature conditions, and there are complex deviations between the external input displacement and the actual displacement acting on the sample, resulting in a technical dilemma where displacement is controllable but the load is unknown; Third, there is a lack of visualization methods for the load transmission path and the stress state of the sample during loading, which limits the reliability of the experimental data.

[0004] Therefore, there is an urgent need for a device and method that can integrate high-temperature loading with DIC visual measurement to achieve stable adjustment of the loading state and in-situ visual characterization without relying on force sensors. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned shortcomings in the prior art by proposing a high-temperature in-situ visualization loading device and method based on digital image correlation.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention proposes a high-temperature in-situ visualization loading device based on digital image correlation: comprising a furnace body unit, a photography unit, and a fixture unit; The furnace unit has a viewing window, and the camera unit is used to acquire images; The clamping unit includes a clamping body, a displacement input component, and a compliant loading component; The compliant loading member is used to contact one side of the specimen; The field of view of the photographic unit covers at least the observation surface of the specimen and the reference area characterizing the deformation of the compliant loading member simultaneously, so as to obtain the deformation information of the specimen and the deformation information of the compliant loading member using digital image correlation methods, and characterize or invert the loading state of the specimen based on the pre-established correspondence.

[0007] Furthermore, the furnace body unit also includes a thermocouple; The photography unit includes a main light source, a filter, at least one industrial CCD camera, a tripod, and a signal output system.

[0008] Furthermore, the fixture body includes: The load-bearing components and guide support components are arranged opposite to each other, as well as the loading platform connecting the two; The compliant loading member is fixed to the end face of the guide support member. The bearing member, the guide support member, and the loading platform are integrally formed to constitute the U-shaped clamp body, wherein the bearing member and the loading platform are slidably connected.

[0009] Furthermore, the displacement input component includes a guide tube fixed to the furnace wall of the furnace body unit and a screw threadedly connected to the guide tube; One end of the screw, extending into the furnace body unit, abuts against the load-bearing component.

[0010] Furthermore, the compliant loading member includes at least a compliant structural region, which is one or more of a necked thin-walled region, a slotted compliant beam region, a laminated compliant region, a corrugated compliant region, or any combination thereof.

[0011] Furthermore, the compliant loading member is disposed within the visible area of ​​the imaging unit, and the reference area is formed on the surface of the compliant loading member. The reference area has a surface texture, speckle pattern, laser microtexture, or high-temperature resistant contrast mark that can be used for digital image correlation recognition.

[0012] A second aspect of the present invention proposes a high-temperature in-situ visualization loading method based on digital image correlation, using the aforementioned apparatus, comprising the following steps: S1, Construct surface features that can be identified by digital image correlation on the specimen observation surface and the reference area of ​​the compliant loading member; S2, Establish the correspondence between the characteristic deformation of the compliant loading member and the loading state of the specimen; S3, load the sample into the fixture unit, so that the compliant loading member contacts one side of the sample, and adjust the field of view of the imaging unit so that it covers at least the sample observation surface and the reference area at the same time. S4, The displacement is input along the loading direction through the displacement input component to apply a load to the specimen; S5, synchronously acquire images and calculate specimen deformation information and conformal loading component deformation information based on digital image correlation methods; S6. Based on the aforementioned correspondence, the load, contact stress state, or loading degree of the specimen is characterized or inverted.

[0013] Furthermore, the correspondence mentioned in step S2 is at least one of the following functional relationships: F = f(δ c ); F = f(ε c ); F = f(δ c , ε c ); in, δ represents the load or equivalent loading state experienced by the specimen. c ε represents the characteristic displacement of a compliant loading member. c This represents the characteristic strain parameters of a component that complies with loading.

[0014] Furthermore, when the compliant loading member is within the linear elastic deformation range, the correspondence simplifies to a linear relationship: F=k δ c

[0015] Where k is the stiffness coefficient determined through experimental calibration or finite element analysis.

[0016] Furthermore, in step S5, a single or dual camera is used for synchronous measurement, and image registration is achieved through time synchronization or trigger synchronization; the characterization or inversion in step S6 includes real-time output of the load value of the sample, plotting load-time curves or load-displacement curves. The method is used for in-situ stress stability characterization under lateral compression, lateral pre-tightening, limiting loading or thermo-chemical-mechanical coupling conditions, and online correction of loading deviations caused by high-temperature thermal expansion, transmission clearance or assembly errors is achieved through the deformation information of the compliant loading component.

[0017] The high-temperature in-situ visualization loading device and method based on digital image correlation proposed in this invention have the following advantages: In this invention, by simultaneously covering the sample and the compliant loading member with the field of view of the imaging unit, the traditionally invisible load state is transformed into the visible deformation of the compliant member, thus realizing in-situ optical characterization of the loading process. This eliminates the need to install force sensors in the high-temperature region, avoiding high-temperature drift and equipment costs.

[0018] Secondly, the predictable elastic deformation of the loading components can absorb additional displacements caused by high-temperature thermal expansion, transmission clearances, and assembly errors, making the loading on the sample more stable and reducing the risk of impact and overload. The overall device is highly compatible with the high-temperature furnace body with a viewing window, and can be used for various working conditions such as lateral compression, lateral pre-tightening, limit loading, and thermo-chemical-mechanical coupling. It is particularly suitable for the study of high-temperature in-situ mechanical behavior of refractory materials, ceramic materials, and their composite materials. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the fixture unit structure according to Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the compliant loading component structure according to Embodiment 1 of the present invention; Figure 4 This is a flowchart of Embodiment 2 of the present invention.

[0020] In the figure: 1. Furnace body unit; 10. Viewing window; 11. Thermocouple; 2. Photography unit; 21. Main light source; 22. Filter; 23. Industrial CCD camera; 24. Tripod; 25. Signal output system; 3. Fixture unit; 31. Fixture body; 311. Loading component; 312. Guide support component; 313. Loading platform; 32. Displacement input component; 321. Guide tube; 322. Screw; 33. Compliant loading component; 331. Compliant beam; 332. Hinge structure; 333. Groove; 34. Sample. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0022] Example 1

[0023] Reference Figures 1-3 The high-temperature in-situ visualization loading device based on digital image correlation includes a furnace body unit 1, a photography unit 2, and a clamping unit 3. The furnace body unit 1 has a viewing window 10. Preferably, in this embodiment, the viewing window 10 can be hinged to the front end of the furnace body unit 1. The furnace body unit 1 includes a furnace body, heating elements and furnace door, etc. The specific structure and principle are conventional methods for those skilled in the art and will not be described in detail here. The photography unit 2 is used to acquire images. The clamping unit 3 includes a clamping body 31, a displacement input component 32, and a compliant loading component 33; The compliant loading member 33 is used to contact one side of the specimen 34; The field of view of the imaging unit 2 covers at least the observation surface of the specimen 34 and the reference area characterizing the deformation of the compliant loading member 33 simultaneously, so as to obtain the deformation information of the specimen and the deformation information of the compliant loading member 33 using digital image correlation methods, and characterize or invert the loading state of the specimen 34 based on the pre-established correspondence.

[0024] In summary, this embodiment transforms the traditionally invisible load state into the visible deformation of the compliant component by simultaneously covering the field of view of the imaging unit 2 with the sample 34 and the compliant loading member 33. This achieves in-situ optical characterization of the loading process, eliminating the need to install force sensors in the high-temperature region and avoiding high-temperature drift and equipment costs.

[0025] Secondly, the predictable elastic deformation of the compliant loading member 33 can absorb additional displacement caused by high-temperature thermal expansion, transmission clearance and assembly error, making the loading on the sample more stable and reducing the risk of impact and overload. The overall device is highly compatible with the high-temperature furnace body with a viewing window, and can be used for various working conditions such as lateral compression, lateral pre-tightening, limit loading and thermo-chemical-mechanical coupling. It is particularly suitable for the study of high-temperature in-situ mechanical behavior of refractory materials, ceramic materials and their composite materials.

[0026] In some embodiments, the furnace unit 1 of the present invention further includes a thermocouple 11, which extends through the furnace wall into the furnace cavity. Its temperature-sensing end is near the sample 34 or the compliant loading member 33, for real-time monitoring of temperature changes during the test. Preferably, the thermocouple 11 can be a type S or type B platinum-rhodium thermocouple to match high-temperature testing requirements. Its output signal is connected to a temperature controller to realize the detection and control of the heating equipment. The photography unit 2 includes a main light source 21, a filter 22, at least one industrial CCD camera 23, a tripod 24, and a signal output system 25.

[0027] Specifically, in this embodiment, the main light source 21 is a high-brightness LED cold light source, which is respectively set on the left and right sides of the industrial CCD camera 23 and fixed on the tripod 24 together with the industrial CCD camera 23. By adjusting the height and angle of the tripod 24, the beam of the main light source 21 is made to uniformly illuminate the surface of the sample 34 and the conformal loading component 33 through the viewing window 10, avoiding the decrease in speckle contrast due to uneven illumination. The filter 22 is installed at the front end of the lens of the industrial CCD camera 23, and its center wavelength matches the emission wavelength of the main light source 21. At the same time, it effectively blocks the red light emitted by the thermal radiation generated by the sample and the components in the furnace at high temperature, thereby significantly improving the signal-to-noise ratio of the acquired image. The pixel resolution of the industrial CCD camera 23 can be selected according to the field of view and measurement accuracy requirements. For example, a CMOS camera with 5 million pixels or higher resolution can be selected and equipped with a telecentric lens or a long working distance microscope lens to reduce perspective distortion. The signal output system 25 connects to the industrial CCD camera 23 via a high-speed data transmission line, such as a GigE or USB 3.0 interface, to transmit the real-time acquired image sequence to a computer, where it is saved and processed by the accompanying DIC software. Preferably, two industrial CCD cameras 23 are used to form a binocular stereo vision system to achieve the measurement of three-dimensional displacement and strain. In cases where only in-plane deformation needs to be measured, a single camera can also be used.

[0028] Furthermore, the fixture body 31 described in this embodiment includes: The load-bearing member 311 and the guide support member 312 are arranged opposite to each other, and the loading platform 313 connects the two. The compliant loading member 33 is fixed to the end face of the guide support member 312. The bearing member 311, the guide support member 312, and the loading platform 313 are integrally formed to constitute the main body of the U-shaped clamp. The bearing member 311 and the loading platform 313 are slidably connected. Specifically, the upper surface or inner side of the loading platform 313 is provided with a groove or guide rail along the loading direction, and the bottom of the bearing member 311 is provided with a slider or boss that matches the groove. The bearing member 311 can slide freely on the loading platform 313 along the loading direction, while being constrained in other directions perpendicular to the loading direction.

[0029] This embodiment significantly improves the overall rigidity and high-temperature stability of the fixture by integrally molding the bearing member 311, guide support member 312, and loading platform 313 into a U-shaped fixture body. The sliding connection between the bearing member 311 and the loading platform 313 ensures the linearity and stability of the loading process. The layout of the compliant loading member 33 fixed to the end face of the guide support member 312 ensures that the compliant loading member 33 remains stationary during loading, providing reaction force only through its elastic deformation, which facilitates stable and clear imaging of the reference area by the imaging unit 2. The above structures together ensure a clear force transmission path, reliable deformation measurement, and accurate inversion of the loading state during high-temperature loading.

[0030] In an optional embodiment, the displacement input component 32 in this embodiment includes a guide tube 321 fixed to the furnace wall of the furnace body unit 1 and a screw 322 threadedly connected to the guide tube 321; Preferably, in this embodiment, the guide tube 321 can be made of high-temperature resistant alloy or stainless steel, and its outer wall is connected to the furnace wall by welding or flange sealing to ensure the airtightness of the furnace cavity. The inner wall of the guide tube 321 is machined with internal threads, and its inner hole axis is substantially coincident with the moving direction of the bearing member 311 and the central axis of the loading member 33 to ensure the alignment of the loading direction. Preferably, a heat insulation layer or heat insulation sleeve can be provided at the end of the guide tube 321 that extends into the furnace cavity to reduce the conduction of high temperature inside the furnace to the outside, and to avoid scalding the operator or damaging the drive mechanism. One end of the screw 322 extending into the furnace body unit 1 abuts against the bearing member 311; that is, the external thread of the screw 322 and the internal thread of the guide tube 321 cooperate with each other, and one end of the screw 322 extends to the outside of the furnace body unit 1 for the operator or electric drive mechanism, such as a stepper motor, servo motor or micro testing machine to rotate. Of course, the rotation is a sleeved and circumferentially locked connection to ensure the linear movement of the screw 322; the other end of the screw 322 passes through the guide tube 321 and extends into the furnace cavity of the furnace body unit 1.

[0031] When the operator rotates the screw 322, the screw 322 moves axially under the drive of the threaded pair, pushing the bearing member 311 to slide on the loading platform 313 toward the guide support member 312, thereby pushing the sample 34 to press against the compliant loading member 33.

[0032] It should be noted that, since the threaded connection between the screw 322 and the guide tube 321 has a self-locking characteristic, it can maintain the displacement input unchanged after the rotation stops, thereby maintaining the load on the sample 34. At the same time, by recording the rotation angle or number of turns of the screw 322, the input displacement can be roughly estimated. However, the core of this invention is to use the deformation information of the compliant loading member 33 to invert the actual load, rather than relying on the displacement input for open-loop control. Therefore, even if there is thread clearance or thermal expansion, it will not affect the accuracy of the final load inversion.

[0033] In some embodiments, the compliant loading member 33 of the present invention includes at least a compliant structural region, which is one or more of a necked thin-walled region, a slotted compliant beam region, a laminated compliant region, a corrugated compliant region, or any combination thereof.

[0034] Specifically, the main body of the compliant loading member 33 is made of high-strength, high-temperature resistant material, such as zirconia ceramic, alumina ceramic, or high-temperature alloy. It is columnar or block-shaped, with one end fixed to the end face of the guide support member 312 and the other end free to contact the specimen 34. To obtain predictable elastic deformation characteristics, a compliant structural zone is intentionally provided in a localized area of ​​the compliant loading member 33, allowing this zone to preferentially undergo elastic deformation under stress, with a definite functional relationship between the deformation and the applied pressure.

[0035] Reference Figure 3 The compliant loading member 33 adopts a slotted compliant beam structure. Specifically, the compliant loading member 33 is provided with a compliant beam 331, a hinge structure 332, and a groove 333. The compliant beam 331 is the main beam structure of the compliant loading member 33, extending along the loading direction; the hinge structure 332 is located at the root or middle of the compliant beam 331, forming a flexible hinge through local slotting, serving as the hinge center for bending deformation; the groove 333 is further formed on the side or surface of the compliant beam 331 to guide deformation concentration or adjust local stiffness. When the specimen 34 compresses the compliant loading member 33, the compliant beam 331 undergoes elastic bending around the hinge structure 332, stress concentration occurs at the groove 333, and auxiliary deformation occurs. The synergistic effect of these three elements causes the compliant loading member 33 to exhibit a predictable elastic response. By tracking the bending displacement of the compliant beam 331, the rotation of the hinge structure 332, or the opening of the groove 333 using digital image correlation methods, the load on the specimen 34 can be inferred.

[0036] It should be noted that, in this embodiment, the compliant loading member 33 is disposed within the visible area of ​​the imaging unit 2, and the reference area is formed on the surface of the compliant loading member 33. The reference area has surface texture, speckle pattern, laser micro-texture or high-temperature resistant contrast mark that can be used for digital image correlation recognition.

[0037] Preferably, the side of the loading member 33 facing the camera is flat or has obvious geometric features to facilitate subsequent image recognition and feature matching.

[0038] The reference region is formed on the surface of the compliant loading member 33. The reference region is one or more specific local areas on the surface of the compliant loading member 33, and the deformation of this region, such as displacement, strain, curvature change, etc., is used as characteristic parameters of the load applied to the inversion specimen 34. For example, the reference region can be the area between two preset marker points on the compliant loading member 33, or it can be the part of the compliant loading member 33 where the deformation is most significant; such as the edge of the groove in the slotted compliant beam region, the middle of the necked thin-walled region, the crest or trough of the corrugated compliant region, or... Figure 2 The sides of the flexible beam 21, the vicinity of the hinge point of the hinge structure 22, and the edge of the groove 23, etc.

[0039] The reference region has surface textures, speckle patterns, laser microtextures, or high-temperature contrast markers that can be used for digital image correlation recognition. Specifically, since digital image correlation methods rely on tracking the grayscale features of image sub-regions to calculate displacement and strain, the surface of the reference region must possess sufficient grayscale variation or feature contrast. In this embodiment, the following surface feature construction methods are provided as options: In this invention, the inherent surface micromorphology of the material of the conforming loading member 33, such as the natural granular texture of sintered ceramics and the tool marks left by machining, is used as identification features. This method requires no additional processing, but it requires the original surface to have sufficient randomness and contrast.

[0040] Secondly, randomly distributed speckle patterns are formed on the surface of the reference area using methods such as high-temperature resistant ceramic coating spraying, contrasting color particle spraying, or high-temperature ink dotting. The size and density of the speckle should be matched with the spatial resolution of the camera and the required measurement accuracy. The speckle pattern, with its good randomness and high contrast, is the most commonly used and reliable characteristic form in DIC measurement.

[0041] Micrometer-scale dot matrix, grid, or random textures are fabricated on the surface of a reference area using laser marking or laser etching equipment. The surface roughness and reflectivity of the laser-treated area are altered, resulting in stable optical features with excellent high-temperature resistance, making it less prone to degradation at high temperatures.

[0042] High-contrast regular or irregular markings are prepared on the surface of the reference area, such as crosshairs, grids, or rings drawn with high-temperature resistant paint, or prefabricated high-temperature resistant ceramic patches are attached to the surface of the reference area. These markings exhibit clear grayscale differences, facilitating feature recognition and tracking by the DIC algorithm.

[0043] The methods for constructing the above surface features can be selected or combined according to actual working conditions. Regardless of the method used, it should be ensured that the surface features do not peel off, discolor, or significantly degrade within the test temperature range to guarantee the continuity and accuracy of DIC measurements.

[0044] In summary, this embodiment arranges the compliant loading member 33 within the visible area of ​​the imaging unit 2 and constructs surface features in its reference area that can be recognized by digital image correlation, enabling the DIC system to accurately capture the minute deformation information of the compliant loading member 33. The introduction of features such as surface texture, speckle patterns, laser microtextures, or high-temperature contrast markings significantly improves the success rate of image sub-region matching and the accuracy of displacement calculation, providing a reliable data foundation for subsequent inversion of the load on the specimen based on correspondence. Furthermore, the aforementioned surface feature construction method is low-cost, easy to operate, and has good compatibility with existing high-temperature DIC technology.

[0045] Example 2

[0046] Reference Figure 4 This embodiment also proposes a high-temperature in-situ visualization loading method based on digital image correlation, using the above-mentioned device, specifically including the following steps: S1, construct surface features that can be identified by digital image correlation on the specimen observation surface and the reference area of ​​the compliant loading member 33; S2, Establish the correspondence between the characteristic deformation of the compliant loading member 33 and the loading state of the specimen; S3, load the sample 34 into the fixture unit 3, so that the compliant loading member 33 contacts one side of the sample 34, and adjust the field of view of the imaging unit 2 so that it covers at least the sample observation surface and the reference area at the same time. S4, a displacement is input along the loading direction through the displacement input component 32 to apply a load to the sample; S5, synchronously acquire images and calculate the deformation information of specimen 34 and the deformation information of compliant loading member 33 based on digital image correlation method; S6. Based on the aforementioned correspondence, the load, contact stress state, or loading degree of the specimen is characterized or inverted.

[0047] As a specific example, the operation process is as follows: First, surface features suitable for digital image correlation recognition are constructed on the observation surface of the sample 34 and the reference area of ​​the compliant loading member 33, respectively. For example, random speckle patterns are formed using high-temperature resistant ceramic coating spraying or laser etching processes, and an initial reference image is acquired using an industrial CCD camera 23 before loading. Next, the characteristic deformation of the compliant loading member 33 (such as the displacement difference δ between two points in the reference area) is established through theoretical calculations or experimental calibration. cThe relationship between the load on the specimen and the load F is such that, for example, the linear relationship F = k·δ c The specimen 34 is then loaded into the clamping unit 3, with the compliant loading member 33 contacting one side of the specimen 34. Simultaneously, the tripod 24 and camera parameters of the imaging unit 2 are adjusted to ensure that the field of view simultaneously covers both the observation surface of the specimen 34 and the reference area of ​​the compliant loading member 33. Subsequently, by rotating the screw 322 of the displacement input member 32, the bearing member 311 is driven to push the specimen 34 towards the compliant loading member 33, thereby applying a controlled compressive load to the specimen. During loading, the industrial CCD camera 23 synchronously acquires image sequences through the viewing window 10, and the signal output system 25 transmits the images to a computer. Using digital image correlation methods, the deformation information (displacement field, strain field) of the specimen 34 surface and the characteristic deformation amount (such as δ) of the reference area of ​​the compliant loading member 33 are simultaneously calculated. c Finally, based on the pre-established correspondence F=k·δ c The measured δ c The actual load on specimen 34 can be calculated in real time by substituting the data into the formula, and stress-strain curves or loading state characterization can be plotted by combining the specimen deformation information. This method realizes in-situ visualization of the loading state without force sensors under high temperature conditions by converting the visual deformation of the compliant loading member 33 into load information, while effectively compensating for the influence of thermal expansion and transmission clearance on loading stability.

[0048] Specifically, in this embodiment, the correspondence described in step S2 is at least one of the following functional relationships: F = f(δ c ); F = f(ε c ); F = f(δ c , ε c ); in, δ represents the load or equivalent loading state experienced by specimen 15. c ε represents the characteristic displacement of a compliant loading member. c This represents the characteristic strain parameters of a component that complies with loading.

[0049] Secondly, when the compliant loading member 14 is within the linear elastic deformation range, the correspondence simplifies to a linear relationship: F=k δ c

[0050] Where k is the stiffness coefficient determined through experimental calibration or finite element analysis.

[0051] It should be noted that in this embodiment, step S5 uses a single camera or dual cameras for synchronous measurement, and image registration is achieved through time synchronization or trigger synchronization. Specifically, when the field of view and resolution of a single industrial CCD camera 23 can simultaneously cover the observation surface of the specimen 34 and the reference area of ​​the compliant loading member 33, a single-camera imaging scheme is adopted, and the camera is controlled by an external trigger signal to acquire images at a fixed frequency; when a single camera cannot simultaneously meet the requirements of field of view and resolution, two or more industrial CCD cameras 23 are used to independently image the specimen 34 and the compliant loading member 33 respectively, and the exposure time of all cameras is strictly consistent through a hardware synchronization signal. The acquired images are registered through timestamps or synchronization frames to ensure a one-to-one correspondence between the specimen deformation information and the compliant loading member deformation information in time during DIC calculation.

[0052] The characterization or inversion in step S6 includes real-time output of the load value of the sample and plotting load-time curves or load-displacement curves. This method is used for in-situ stress stability characterization under lateral compression, lateral preload, limiting loading, or thermo-chemical-mechanical coupling conditions. It also uses the deformation information of the compliant loading component to correct online loading deviations caused by high-temperature thermal expansion, transmission clearance, or assembly errors. For example, in high-temperature compressive strength testing of refractory materials, this device can achieve lateral compression loading; in creep-oxidation coupling tests of ceramic matrix composites, a preload can be applied through the displacement input component and a constant displacement can be maintained for a long time, using the deformation information of the compliant loading component 33 to invert load decay in real time. Simultaneously, the deformation information of the compliant loading component 33 is used to correct online loading deviations caused by high-temperature thermal expansion, transmission clearance, or assembly errors. Specifically, during the heating process, the furnace fixture, sample, and compliant loading component 33 itself all undergo thermal expansion. If the load is estimated solely based on the rotational displacement of the external screw 322, significant errors will occur; however, this method directly measures the elastic deformation δ of the compliant loading component 33. c This deformation directly corresponds to the actual transmitted elastic force; therefore, regardless of changes in furnace expansion or gaps, as long as δ c The load F, which is accurately measured and inverted, is the actual load borne by the sample 34, thus realizing automatic online correction of the loading deviation.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-temperature in-situ visualization loading device based on digital image correlation, characterized in that: It includes a furnace body unit (1), a photography unit (2), and a fixture unit (3); The furnace body unit (1) has a viewing window (10), and the photography unit (2) is used to acquire images; The clamp unit (3) includes a clamp body (31), a displacement input component (32), and a compliant loading component (33); The compliant loading member (33) is used to contact one side of the specimen (34); The field of view of the photographic unit (2) covers at least the observation surface of the specimen (34) and the reference area characterizing the deformation of the compliant loading member (33) simultaneously, so as to obtain the deformation information of the specimen and the deformation information of the compliant loading member (33) using digital image correlation methods, and characterize or invert the loading state of the specimen (34) based on the pre-established correspondence.

2. The high-temperature in-situ visualization loading device based on digital image correlation according to claim 1, characterized in that: The furnace body unit (1) also includes a thermocouple (11); The photography unit (2) includes a main light source (21), a filter (22), at least one industrial CCD camera (23), a tripod (24), and a signal output system (25).

3. The high-temperature in-situ visualization loading device based on digital image correlation according to claim 1, characterized in that: The fixture body (31) includes: The load-bearing member (311) and the guide support member (312) are arranged opposite to each other, and the loading platform (313) connects the two. The compliant loading member (33) is fixed to the end face of the guide support member (312). The bearing member (311), the guide support member (312) and the loading platform (313) are integrally formed to form the main body of the U-shaped clamp, wherein the bearing member (311) and the loading platform (313) are slidably connected.

4. The high-temperature in-situ visualization loading device based on digital image correlation according to claim 3, characterized in that: The displacement input component (32) includes a guide tube (321) fixed to the furnace wall of the furnace body unit (1) and a screw (322) threadedly connected to the guide tube (321). The screw (322) extends into the furnace body unit (1) and abuts against the bearing member (311) at one end.

5. The high-temperature in-situ visualization loading device based on digital image correlation according to claim 1, characterized in that: The compliant loading member (33) includes at least a compliant structural region, which is one or more of a necked thin-walled region, a slotted compliant beam region, a laminated compliant region, a corrugated compliant region, or any combination thereof.

6. The high-temperature in-situ visualization loading device based on digital image correlation according to claim 5, characterized in that: The compliant loading member (33) is disposed within the visible area of ​​the imaging unit (2), and the reference area is formed on the surface of the compliant loading member (33). The reference area has a surface texture, speckle pattern, laser microtexture or high-temperature contrast mark that can be used for digital image correlation recognition.

7. A high-temperature in-situ visualization loading method based on digital image correlation, using the apparatus as described in any one of claims 1-6, characterized in that, Includes the following steps: S1, construct surface features that can be identified by digital image correlation on the specimen observation surface and the reference area of ​​the compliant loading member (33); S2, establish the correspondence between the characteristic deformation of the compliant loading member (33) and the loading state of the specimen; S3, load the sample (34) into the fixture unit (3), make the compliant loading member (33) contact one side of the sample (34), and adjust the field of view of the imaging unit (2) so that it covers at least the sample observation surface and the reference area at the same time. S4, a load is applied to the specimen by inputting displacement along the loading direction through the displacement input component (32); S5, synchronously acquire images and calculate the deformation information of the specimen (34) and the deformation information of the compliant loading member (33) based on the digital image correlation method; S6. Based on the aforementioned correspondence, the load, contact stress state, or loading degree of the specimen is characterized or inverted.

8. The method according to claim 7, characterized in that, The correspondence mentioned in step S2 is at least one of the following functional relations: F = f(δ c ) ; F = f(e c ); F = f(δ c , eh c ); in, δ represents the load or equivalent loading state of the specimen (15). c ε represents the characteristic displacement of a compliant loading member. c This represents the characteristic strain parameters of a component that complies with loading.

9. The method according to claim 7, characterized in that: When the compliant loading member (14) is within the linear elastic deformation range, the correspondence simplifies to a linear relationship: F=k d c Where k is the stiffness coefficient determined through experimental calibration or finite element analysis.

10. The method according to claim 7, characterized in that: In step S5, a single or dual camera is used for synchronous measurement, and image registration is achieved through time synchronization or trigger synchronization. The characterization or inversion in step S6 includes real-time output of the load value of the sample and plotting the load-time curve or load-displacement curve. The method is used for in-situ stress stability characterization under lateral compression, lateral pre-tightening, limit loading or thermo-chemical-mechanical coupling conditions, and the loading deviation caused by high temperature thermal expansion, transmission clearance or assembly error is corrected online through the deformation information of the compliant loading component.

Images