A method for measuring thermal deformation of a sample under a temperature impact environment of a double-compartment temperature control box based on a two-camera DIC

Abstract

The application discloses a kind of based on double-camera DIC's double-compartment temperature control box temperature impact environment under sample thermal deformation measurement method, this method is set up camera A and camera B respectively in the high-temperature working chamber and the low-temperature working chamber observation window of double-compartment temperature control box, and the limit signal generated by moving basket in place is used as trigger signal, so that camera A and camera B are switched with sample in upper and lower temperature interval and alternate relay collection image;Image collected by two cameras is sequentially calculated by DIC, respectively obtains the total displacement field of the sample to be tested and the rigid displacement of sample holder reference surface, and the rigid displacement is deducted from the total displacement field, and the real thermal deformation displacement field and thermal strain field of sample are obtained.The application can solve the problem of discontinuous field of view of single camera in double-compartment temperature control box and the interference problem of rigid body displacement of moving basket, and realize non-contact full-field thermal deformation measurement in the whole process of cold and hot impact.

Description

Technical Field

[0001] This invention relates to the field of optical non-contact deformation measurement and environmental reliability testing technology. Specifically, it relates to a method for measuring the thermal deformation of samples under temperature shock conditions in a dual-chamber temperature control chamber based on a dual-camera DIC. Background Technology

[0002] High and low temperature thermal shock testing is an important testing method for evaluating the reliability of materials, components, and structures under severe temperature alternation environments. It is widely used in aerospace, electronics, automotive parts, composite materials, adhesive structures, and encapsulated devices. This type of testing is typically conducted using a two-compartment thermal shock test chamber, which generally includes a high-temperature chamber arranged vertically or adjacently to a low-temperature chamber. The test sample is mounted on a moving basket or transfer mechanism, rapidly switching between the high-temperature and low-temperature chambers to simulate the sudden temperature rises, drops, and repeated thermal shock environments that may be encountered during actual service. During this process, the sample undergoes thermal expansion and contraction, local warping, interface deformation, and strain concentration due to material mismatch. Therefore, accurately obtaining the displacement field, strain field, and local thermal deformation characteristics of the sample throughout the entire thermal shock cycle is crucial for evaluating the thermal stability of materials, structural reliability, and failure mechanisms.

[0003] Among existing methods for measuring thermal deformation, contact measurement is the most common, such as strain gauges, displacement sensors, and extensometers. While these methods can obtain strain or displacement data at specific locations, they typically only reflect the deformation at local points or a limited number of measuring points, making it difficult to obtain full-field deformation information of the sample surface. Furthermore, in rapidly alternating high and low temperature environments, contact sensors and their adhesive layers are susceptible to temperature shocks, leading to problems such as adhesive softening, cracking, detachment, or signal drift, thus affecting measurement stability and accuracy. For samples that are small in size, have complex surface morphology, and exhibit concentrated local deformation, contact measurement may also alter the original stress state or thermal boundary conditions of the sample, making it difficult to meet the requirements for non-contact, high-precision, and full-field measurement.

[0004] Digital image correlation (DIC) technology is a non-contact optical measurement method based on digital image processing and speckle matching. It involves creating random speckles on the surface of the object under test, acquiring images before and after deformation, and using image correlation matching algorithms to track the positional changes of speckle sub-regions, thereby calculating the displacement and strain fields of the object's surface. Compared to traditional contact measurement methods, DIC technology offers advantages such as non-contact operation, full-field measurement, minimal load on the sample, and suitability for complex deformation analysis. Therefore, it has been applied in scenarios such as materials mechanical property testing, structural deformation measurement, and thermal deformation analysis.

[0005] However, directly applying conventional DIC measurements in a two-compartment thermal shock test chamber presents significant challenges. The high-temperature and low-temperature chambers of a two-compartment thermal shock test chamber are typically isolated from each other by partitions, chamber structure, and independent observation windows, resulting in spatial separation between the two temperature zones. Conventional DIC systems usually rely on a single camera optical path and a fixed field of view. When the test sample moves from the high-temperature chamber to the low-temperature chamber with the moving basket, or vice versa, a single camera struggles to simultaneously cover the observation windows of both temperature zones. This can easily lead to loss of the target field of view during sample movement across temperature zones, resulting in image acquisition interruption and ultimately preventing the acquisition of continuous deformation data throughout the complete thermal shock cycle.

[0006] Furthermore, when the moving basket switches between the high-temperature chamber and the low-temperature chamber, it causes the test sample and the sample holder to move as a whole. This overall movement appears as a large rigid body displacement in the image, while the thermal deformation of the test sample due to temperature changes is usually superimposed on this rigid body displacement. If the conventional DIC algorithm is directly used to match and calculate the sample image, the overall displacement caused by the movement across temperature zones will be included in the sample deformation results. This may lead to the calculated displacement and strain fields containing significant mechanical displacement interference, and even related matching failures when the displacement is too large, the field of view is switched, or the speckle matching is discontinuous. Therefore, conventional DIC measurement methods cannot accurately distinguish between the rigid body displacement of the sample caused by the movement of the basket and the actual thermal deformation of the sample due to thermal shock.

[0007] Furthermore, the thermal shock test environment itself places high demands on image acquisition. The specimen needs to switch rapidly between high and low temperatures, and issues such as temperature differences, reflections, fogging, uneven lighting, or localized image quality degradation may occur inside and outside the observation window. Ordinary speckle coatings may also experience cracking, peeling, increased reflection, or reduced contrast during intense thermal cycling, thus affecting the DIC algorithm's identification and matching of speckle sub-regions. Therefore, simply setting up an ordinary DIC camera outside the test chamber for shooting is insufficient to guarantee image continuity, speckle stability, and computational reliability throughout the entire thermal shock cycle.

[0008] In summary, existing technologies for measuring the thermal deformation of specimens in a two-chamber thermal shock test chamber have at least the following shortcomings: First, contact measurement methods can only obtain local data and lack reliability in rapidly alternating high and low temperature environments; second, conventional single-camera DIC systems cannot simultaneously cover two isolated observation fields in the high-temperature chamber and the low-temperature chamber, and are prone to data acquisition interruptions due to specimen movement across temperature zones; third, the rigid body displacement caused by the moving basket switching across temperature zones will be superimposed on the specimen thermal deformation measurement results, leading to increased errors or even matching failures in conventional DIC calculation results; fourth, the alternating hot and cold environment places high demands on speckle stability, lighting conditions, and image quality, and ordinary speckle and ordinary acquisition methods are difficult to meet the requirements of continuous, stable, and accurate measurement.

[0009] Therefore, it is necessary to provide a method for measuring the thermal deformation of samples under temperature shock conditions in a dual-chamber temperature control chamber based on dual-camera DIC to solve the above problems. Summary of the Invention

[0010] The purpose of this invention is to solve the technical problems mentioned in the background art and to provide a method for measuring the thermal deformation of samples under temperature shock environment in a dual-compartment temperature control chamber based on dual-camera DIC.

[0011] The above-mentioned objective of the present invention is achieved as follows:

[0012] A method for measuring the thermal deformation of samples under temperature shock conditions in a dual-compartment temperature control chamber based on a dual-camera DIC system includes the following steps:

[0013] Camera A is set outside the observation window of the high-temperature chamber of the double-compartment temperature control chamber, and camera B is set outside the observation window of the low-temperature chamber, so that camera A and camera B form independent acquisition fields of view for the corresponding high-temperature chamber and low-temperature chamber, respectively.

[0014] Speckle patterns that can be identified by digital image correlation calculation are simultaneously prepared on the surface of the test sample and on the reference surface of the sample holder supporting the test sample;

[0015] The test sample is fixed to the sample holder, and the test sample and sample holder are moved between the high-temperature chamber and the low-temperature chamber by the moving basket.

[0016] The system acquires the arrival signal generated when the mobile suspended platform arrives at and is positioned in the high-temperature or low-temperature chamber. Based on the arrival signal, it triggers the camera corresponding to the current temperature zone to acquire images, thereby forming an image sequence alternately acquired by camera A and camera B.

[0017] Digital image correlation calculations were performed on the image sequence according to the acquisition time sequence to obtain the total displacement field of the test sample and the rigid body displacement of the sample holder reference plane, respectively.

[0018] Using the rigid body displacement of the reference plane of the specimen holder as a reference for the rigid body displacement introduced by the cross-temperature zone movement, the rigid body displacement is subtracted from the total displacement field of the test specimen to obtain the thermal deformation displacement field and / or thermal strain field of the test specimen during the temperature shock process.

[0019] Furthermore, the dual-compartment temperature control chamber includes a high-temperature chamber and a low-temperature chamber arranged vertically. The movable basket moves along the path between the high-temperature chamber and the low-temperature chamber, causing the test sample and the sample holder to switch between temperature zones. Camera A acquires images through the observation window of the high-temperature chamber, and camera B acquires images through the observation window of the low-temperature chamber.

[0020] Furthermore, the positioning signal is a mechanical limit electrical signal generated by a limit switch when the moving basket reaches the high-temperature chamber or the low-temperature chamber and is pressed and positioned. The mechanical limit electrical signal is converted into a trigger signal for controlling the exposure acquisition of camera A or camera B by a synchronous triggering device.

[0021] Furthermore, when the moving basket reaches the high-temperature chamber and triggers the upper limit switch, the synchronous triggering device triggers camera A to acquire images of the test sample and sample holder inside the high-temperature chamber; when the moving basket reaches the low-temperature chamber and triggers the lower limit switch, the synchronous triggering device triggers camera B to acquire images of the test sample and sample holder inside the low-temperature chamber, thus forming an alternating relay acquisition sequence of high and low temperature images.

[0022] Furthermore, in preparing the speckle pattern, a paint that is resistant to high and low temperatures and has no reflective properties is used to form a base color coating on the surface of the test sample and the reference surface of the sample holder. Randomly distributed speckle spots of varying sizes and not connected to each other are formed on the base color coating, so that the test sample and the sample holder maintain speckle characteristics that can be identified by DIC during the process of alternating hot and cold temperatures.

[0023] Furthermore, before conducting the temperature shock test, the calibration plate is fixed on the sample holder, and the characteristic pattern surface of the calibration plate is on the same physical plane as the speckle test surface of the test sample. The moving basket is controlled to stop at the high temperature chamber and the low temperature chamber respectively, and the calibration plate images under the corresponding temperature zone are acquired by camera A and camera B respectively to obtain the calibration parameters of the corresponding field of view of camera A and camera B.

[0024] Furthermore, the test sample is clamped onto the sample holder by means of rigid fixation at one end and free deformation at the other end, so that the rigid fixed end of the test sample moves synchronously across the temperature zone with the sample holder, and the measuring end of the test sample can undergo thermal deformation under temperature shock.

[0025] Furthermore, cameras A and B are respectively equipped with optical lenses and light sources. The light source is preferably a weather-resistant cold light source. Before acquisition, the illumination intensity and illumination angle of the light source are adjusted so that the speckle images of the test sample surface and the reference surface of the sample holder meet the relevant matching requirements of digital image correlation calculation.

[0026] Furthermore, the digital image correlation calculation includes: using speckle sub-regions in the image as matching objects, performing correlation matching between the reference state image and the target state image, calculating the two-dimensional displacement fields of the test sample and the specimen holder at different times, and calculating the full-field strain field based on the two-dimensional displacement fields.

[0027] Furthermore, after obtaining the thermal deformation displacement field and / or thermal strain field of the test sample, deformation cloud map and data curve of the test sample during thermal shock cycling are generated and output.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. This invention achieves relay image acquisition from two independent fields of view in a dual-compartment temperature control chamber by placing camera A outside the observation window of the high-temperature chamber and camera B outside the observation window of the low-temperature chamber. The limit signal generated when the moving basket reaches its position triggers the camera corresponding to the current temperature zone to acquire images. Compared with conventional single-camera DIC measurement methods, this invention overcomes the problem of discontinuous fields of view caused by the physical partition and independent observation windows separating the upper and lower temperature zones of the dual-compartment temperature control chamber. It also avoids target loss and image acquisition interruption when the test sample moves across temperature zones, thereby obtaining an image sequence covering the complete thermal shock cycle process.

[0030] 2. This invention simultaneously prepares speckle patterns on the surface of the test sample and the reference surface of the sample holder. During the DIC calculation, the total displacement field of the test sample and the displacement field of the reference surface of the sample holder are obtained separately. Then, the displacement of the reference surface of the sample holder is used as a reference for the rigid body displacement introduced by the moving basket across temperature zones, and this rigid body displacement is subtracted from the total displacement field of the test sample. Therefore, this invention can distinguish between the mechanical displacement of the test sample caused by the overall movement of the basket and the actual thermal deformation of the test sample itself due to thermal shock, reducing the interference of cross-basin movement on the DIC calculation results and improving the measurement accuracy of the thermal deformation displacement field and thermal strain field.

[0031] 3. This invention employs a speckle pattern preparation method that is resistant to high and low temperatures and lacks reflection. Combined with adjustments to the camera's optical lens, light source intensity, and illumination angle, the speckle pattern on the test sample surface and the reference surface of the sample holder maintains good recognizability and imaging quality even under alternating hot and cold environments. This method eliminates the need to attach strain gauges, extensometers, or other contact sensors to the sample surface, reducing problems such as sensor detachment, adhesion failure, limited local measurement points, and impact on the sample's thermal boundary conditions. It enables non-contact, full-field, and continuous thermal deformation measurement of the test sample under temperature shock conditions, and can output deformation contour maps and data curves, providing a basis for analyzing the sample's thermal deformation patterns and local deformation characteristics. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the testing system of the present invention;

[0033] Figure 2 This is a schematic diagram of the testing process of the present invention;

[0034] Figure 3 This is a schematic diagram of the two-dimensional digital image correlation technology in this invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the following description is provided in conjunction with embodiments and appendices. Figure 1-3 The present invention will be further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0036] Example 1: As Figure 1 As shown, this embodiment uses a two-compartment thermal shock test chamber as the temperature shock environment generating device. The two-compartment thermal shock test chamber includes a high-temperature chamber and a low-temperature chamber arranged vertically. The high-temperature chamber is used to create a heating environment, and the low-temperature chamber is used to create a cooling environment. The high-temperature chamber has an upper observation window, and the low-temperature chamber has a lower observation window. A movable basket is installed inside the two-compartment thermal shock test chamber and can move up and down between the high-temperature chamber and the low-temperature chamber along a track under the drive of a traction transmission device.

[0037] The test sample is mounted on a sample holder, which is fixed inside a movable basket. In addition to holding the test sample, the sample holder also has a rigid reference surface for DIC recognition. The test sample can be mounted on the sample holder with one end rigidly fixed and the other end freely deformable, allowing the fixed end of the test sample to move synchronously across the temperature range with the sample holder and the movable basket, while simultaneously allowing the measuring end of the test sample to undergo thermal deformation under thermal shock.

[0038] Camera A is positioned outside the upper observation window of the high-temperature chamber, and camera B is positioned outside the lower observation window of the low-temperature chamber. Camera A is used to acquire images of the test sample when it is located in the high-temperature chamber, and camera B is used to acquire images of the test sample when it is located in the low-temperature chamber. Cameras A and B are equipped with optical lenses and light sources, preferably weather-resistant cold light sources. Cameras A and B, the synchronization triggering device, and the DIC acquisition equipment are all connected to the measurement and control and DIC analysis workstation. By adjusting the camera position, lens focal length, aperture, and the illumination intensity and angle of the light source, the speckle on the surface of the test sample and the reference surface of the sample holder can be clearly imaged outside the observation window of the corresponding temperature zone.

[0039] Before the experiment, the surface of the test sample and the reference surface of the sample holder are cleaned to remove oil, dust, and moisture. Then, speckle patterns are simultaneously prepared on both the test sample surface and the reference surface of the sample holder. Specifically, a high- and low-temperature resistant, non-reflective coating can be used to first form a background coating, and then randomly distributed, non-contiguous speckle patterns of varying sizes are formed on this background coating. By simultaneously preparing speckle patterns on both the test sample and the reference surface of the sample holder, subsequent DIC analysis can simultaneously identify the displacement changes of both the test sample and the overall displacement changes of the sample holder.

[0040] Before the formal test, cameras A and B need to be calibrated separately. A high-precision calibration plate is fixed to the sample holder, ensuring that the feature pattern surface of the calibration plate is on the same physical plane as the speckle test surface of the test sample. The moving basket is raised and fully lowered into the high-temperature chamber. A synchronous triggering device is used to control camera A to acquire images of the calibration plate under the field of view of the high-temperature chamber, obtaining the calibration parameters for the corresponding field of view of camera A. Then, the moving basket is lowered and fully lowered into the low-temperature chamber. A synchronous triggering device is used to control camera B to acquire images of the calibration plate under the field of view of the low-temperature chamber, obtaining the calibration parameters for the corresponding field of view of camera B.

[0041] During temperature shock testing, the temperature conditions of the high-temperature chamber and the low-temperature chamber are first set, and the vertical switching of the moving basket is initiated. When the moving basket reaches and is firmly positioned in the high-temperature chamber, the upper limit switch generates a positioning signal. Based on this signal, the synchronous triggering device triggers camera A to acquire images of the test sample and sample holder inside the high-temperature chamber. When the moving basket reaches and is firmly positioned in the low-temperature chamber, the lower limit switch generates a positioning signal. Based on this signal, the synchronous triggering device triggers camera B to acquire images of the test sample and sample holder inside the low-temperature chamber. Thus, cameras A and B alternately and relay data acquisition in two physically isolated temperature zones.

[0042] like Figure 2As shown, the testing process in this embodiment includes the following steps: designing and preparing a sample holder; fixing the sample and fabricating high and low temperature speckle patterns; calibrating the DIC measurement system; conducting temperature shock experiments and acquiring images; and calculating the deformation field results for all acquired image data. Since camera A and camera B correspond to the high-temperature chamber and the low-temperature chamber respectively, the problem of a single camera losing its field of view when the test sample moves across temperature zones can be avoided. Because the camera trigger signal originates from the positioning signal of the moving basket, the image acquisition time corresponds to the positioning state of the moving basket, reducing the impact of the basket's movement on image acquisition.

[0043] After data acquisition, the images obtained by cameras A and B are imported into the DIC analysis software in chronological order of acquisition. The DIC analysis software identifies and calculates the speckle region on the surface of the test sample and the speckle region on the reference surface of the sample holder, respectively, to obtain the total displacement field of the test sample and the displacement field of the reference surface of the sample holder. Since the displacement of the reference surface of the sample holder mainly reflects the rigid body displacement introduced during the movement of the mobile basket across the temperature zone, the displacement of the reference surface of the sample holder is used as a rigid body displacement reference. By subtracting this rigid body displacement from the total displacement field of the test sample, the true thermal deformation displacement field and thermal strain field of the test sample during the thermal shock process can be obtained, and deformation contour maps and data curves can be further generated.

[0044] Example 2: This example, based on the system structure, speckle preparation, dual-temperature zone calibration, and relay acquisition process of Example 1, further illustrates the DIC calculation process, such as... Figure 3 As shown, two-dimensional digital image correlation technology tracks the positional changes of speckle sub-regions on the surface of the test sample by comparing a reference state image before deformation and a target state image after deformation, thereby calculating the full-field displacement and strain of the test sample surface. When performing matching, the algorithm does not compare each pixel independently, but rather selects a point centered on the test point. A square region of a certain size is used as a reference image sub-region. Then, a target image sub-region in the target state image is searched for that most similar to the grayscale distribution of the reference image sub-region. Assume the coordinates of the center point of the sub-region in the reference image are... After deformation, the point moves to the target image. For any point within the sub-region Its coordinates after deformation It can be expressed by a first-order form function as:

[0045] ;

[0046] ;

[0047] in, and They represent the center points respectively. Displacement in the horizontal and vertical directions, and These represent the distances of pixels within a sub-region relative to the center point. , , , The displacement gradient is related to strain. To measure the similarity between the reference and target image subregions, the zero-mean normalized cross-correlation standard ZNCC is used, with the following formula:

[0048] ;

[0049] in, For reference, the grayscale values ​​of pixels in a sub-region of the image. This refers to the grayscale value of the corresponding pixel in the target image sub-region. The average gray value of a sub-region of the reference image. This represents the average gray value of a sub-region of the target image. The DIC analysis software searches for... To achieve the optimal target image sub-region position, determine the corresponding position of the reference image sub-region in the target image, thereby obtaining the displacement of the corresponding measurement point.

[0050] In this embodiment, camera A acquires images from the high-temperature working chamber, and camera B acquires images from the low-temperature working chamber. Since cameras A and B are located outside two independent observation windows, the images acquired by both need to be uniformly sorted according to the actual acquisition time to form an image sequence covering the thermal shock cycle process. When the DIC analysis software calculates this image sequence, it selects the speckle region on the surface of the test sample and the speckle region on the reference surface of the sample holder as the analysis objects, and uses the aforementioned first-order form and position function and ZNCC correlation criterion to complete the speckle sub-region matching to obtain the displacement fields of the test sample and the reference surface of the sample holder at different times.

[0051] When the moving basket switches between the high-temperature chamber and the low-temperature chamber, it causes the test sample and the sample holder to move as a whole. This overall movement is represented as rigid body displacement in the image. If the total displacement of the test sample is directly used as the thermal deformation result, the rigid body displacement introduced by the switching of the moving basket across temperature zones will be included, leading to errors in the thermal deformation measurement results. In this embodiment, speckle patterns are prepared simultaneously on the reference surface of the sample holder, and the displacement of the reference surface of the sample holder is calculated simultaneously. The displacement of the reference surface of the sample holder is used as a reference for the rigid body displacement introduced by the movement across temperature zones. This rigid body displacement is then subtracted from the total displacement field of the test sample, thereby obtaining the thermal deformation displacement field and thermal strain field of the test sample itself.

[0052] Combination Figure 1As shown, the dual-camera relay acquisition system in this embodiment includes a two-chamber thermal shock test chamber, a movable basket, an upper limit switch, a lower limit switch, an upper observation window, a lower observation window, camera A, camera B, an optical lens, a light source, a synchronous triggering device, and a measurement and control and DIC analysis workstation. Combined with... Figure 2 As shown, the experimental procedure in this embodiment includes specimen holder design and preparation, specimen fixation and high-temperature speckle fabrication, DIC measurement system calibration, temperature shock experiment and image acquisition, and deformation field result calculation. Combined with... Figure 3 In this embodiment, the displacement information is obtained by using the speckle sub-region correlation matching method, and the displacement of the sample holder reference surface is used to deduct the rigid body displacement interference caused by the movement across the temperature zone.

[0053] Through the above-described embodiments of the present invention, the present invention can achieve continuous image acquisition of the test sample during thermal shock cycling when the high-temperature chamber and the low-temperature chamber are physically isolated and a single camera cannot cover the two temperature zones at the same time; at the same time, by synchronous speckle and rigid body displacement subtraction of the sample holder reference plane, the influence of the switching of the moving basket across temperature zones on the thermal deformation results can be reduced, thereby obtaining the full-field thermal deformation measurement results of the test sample under temperature shock environment.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for measuring the thermal deformation of samples under temperature shock conditions in a dual-compartment temperature-controlled chamber based on a dual-camera DIC, characterized in that, Includes the following steps: Camera A is set outside the observation window of the high-temperature chamber of the double-compartment temperature control chamber, and camera B is set outside the observation window of the low-temperature chamber, so that camera A and camera B form independent acquisition fields of view for the corresponding high-temperature chamber and low-temperature chamber, respectively. Speckle patterns that can be identified by digital image correlation calculation are simultaneously prepared on the surface of the test sample and on the reference surface of the sample holder supporting the test sample; The test sample is fixed to the sample holder, and the test sample and sample holder are moved between the high-temperature chamber and the low-temperature chamber by the moving basket. The system acquires the arrival signal generated when the mobile suspended platform arrives at and is positioned in the high-temperature or low-temperature chamber. Based on the arrival signal, it triggers the camera corresponding to the current temperature zone to acquire images, thereby forming an image sequence alternately acquired by camera A and camera B. Digital image correlation calculations were performed on the image sequence according to the acquisition time sequence to obtain the total displacement field of the test sample and the rigid body displacement of the sample holder reference plane, respectively. Using the rigid body displacement of the reference plane of the specimen holder as a reference for the rigid body displacement introduced by the cross-temperature zone movement, the rigid body displacement is subtracted from the total displacement field of the test specimen to obtain the thermal deformation displacement field and / or thermal strain field of the test specimen during the temperature shock process.

2. The method for measuring the thermal deformation of samples under temperature shock conditions in a dual-chamber temperature control chamber based on dual-camera DIC as described in claim 1, characterized in that, The dual-compartment temperature control chamber includes a high-temperature chamber and a low-temperature chamber arranged vertically. The movable basket moves along the path between the high-temperature chamber and the low-temperature chamber, causing the test sample and the sample holder to switch between temperature zones. Camera A acquires images through the observation window of the high-temperature chamber, and camera B acquires images through the observation window of the low-temperature chamber.

3. The method for measuring the thermal deformation of samples under temperature shock in a dual-chamber temperature control chamber based on dual-camera DIC according to claim 1, characterized in that, The arrival signal is a mechanical limit electrical signal generated by a limit switch when the mobile basket arrives at the high-temperature chamber or the low-temperature chamber and is pressed and positioned. The mechanical limit electrical signal is converted into a trigger signal for controlling the exposure acquisition of camera A or camera B by a synchronous triggering device.

4. The method for measuring the thermal deformation of samples under temperature shock conditions in a dual-chamber temperature control chamber based on dual-camera DIC as described in claim 3, characterized in that, When the moving basket reaches the high-temperature chamber and triggers the upper limit switch, the synchronous triggering device triggers camera A to acquire images of the test sample and sample holder inside the high-temperature chamber; when the moving basket reaches the low-temperature chamber and triggers the lower limit switch, the synchronous triggering device triggers camera B to acquire images of the test sample and sample holder inside the low-temperature chamber, thus forming an alternating relay acquisition sequence of high and low temperature images.

5. The method for measuring the thermal deformation of samples under temperature shock conditions in a dual-chamber temperature control chamber based on dual-camera DIC according to claim 1, characterized in that, In preparing the speckle pattern, a paint that is resistant to high and low temperatures and has no reflective properties is used to form a base coat on the surface of the test sample and the reference surface of the sample holder. Randomly distributed speckles of varying sizes and that are not connected to each other are formed on the base coat, so that the test sample and the sample holder maintain speckle characteristics that can be identified by DIC during the alternating hot and cold process.

6. The method for measuring the thermal deformation of samples under temperature shock conditions in a dual-chamber temperature control chamber based on dual-camera DIC as described in claim 1, characterized in that, Before conducting the temperature shock test, the calibration plate is fixed on the sample holder, and the characteristic pattern surface of the calibration plate is on the same physical plane as the speckle test surface of the test sample. The moving basket is controlled to stop at the high temperature chamber and the low temperature chamber respectively, and the calibration plate images under the corresponding temperature zone are acquired by camera A and camera B respectively to obtain the calibration parameters of the corresponding field of view of camera A and camera B.

7. The method for measuring the thermal deformation of samples under temperature shock conditions in a dual-compartment temperature control chamber based on dual-camera DIC according to claim 1, characterized in that, The test sample is clamped on the sample holder by means of rigid fixation at one end and free deformation at the other end, so that the rigid fixed end of the test sample moves synchronously across the temperature zone with the sample holder, and the measuring end of the test sample can undergo thermal deformation under temperature shock.

8. The method for measuring the thermal deformation of samples under temperature shock conditions in a dual-compartment temperature control chamber based on dual-camera DIC according to claim 1, characterized in that, Camera A and camera B are respectively equipped with optical lenses and light sources. The light source is preferably a weather-resistant cold light source. Before acquisition, the illumination intensity and illumination angle of the light source are adjusted so that the speckle images of the test sample surface and the reference surface of the sample holder meet the relevant matching requirements of digital image correlation calculation.

9. The method for measuring the thermal deformation of samples under temperature shock in a dual-chamber temperature control chamber based on dual-camera DIC according to claim 1, characterized in that, The digital image correlation calculation includes: using speckle sub-regions in the image as matching objects, performing correlation matching between the reference state image and the target state image, calculating the two-dimensional displacement fields of the test sample and the specimen holder at different times, and calculating the full-field strain field based on the two-dimensional displacement fields.

10. The method for measuring the thermal deformation of samples under temperature shock conditions in a dual-chamber temperature control chamber based on dual-camera DIC according to claim 1, characterized in that, After obtaining the thermal deformation displacement field and / or thermal strain field of the test sample, the deformation cloud map and data curve of the test sample during the thermal shock cycle are generated and output.

Images