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Abstract
Monochromatic light-illuminated active-imaging stereo-digital image correlation (stereo-DIC) has been extensively used for measuring the surface deformation of materials and structures at elevated temperatures. Despite the improvements in the image acquisition techniques or devices, it is still challenging to measure the 3D deformation of materials and structures in the presence of strong, time-varying ambient light and thermal radiation. In this study, we present what we believe to be a novel dual-filtering single-camera stereo-DIC technique for full-field 3D high-temperature deformation measurement, even in the case of extremely intense ambient light and thermal radiation. In contrast to conventional active-imaging stereo-DIC that only suppresses the thermal radiations in the spectral domain, the proposed technique utilized a dual-filtering strategy (i.e., narrow bandpass optical filtering and ultrashort exposing) to suppress the strong ambient light and thermal radiation in both time and spectral domains. Besides, a four-mirror adapter is adopted to realize 3D shape and deformation measurement using a compact single time-gated camera. Experimental verifications, including assessments with laboratory experiments and validations on real thermal deformation tests under transient aerodynamic heating and direct ohmic heating, convincingly demonstrated that the proposed single-camera dual-filtering stereo-DIC method can achieve accurate 3D shape, motion and deformation measurement, even with strong light and thermal radiation from the quartz lamps and the heated sample.
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1. Introduction
High-temperature deformation measurement is crucial for the thermo-mechanical tests of materials and structures operating at elevated temperature in various fields, including but not limited to aerospace, aero-engine, nuclear and wielding industries [1–5]. It not only enables the researchers and engineers to accurately assess the mechanical performance or properties (e.g., Young's modulus and strength) of the materials and structures at elevated temperatures, but also can help to validate and improve the computational models. For example, hypersonic vehicles often experience strong aerodynamic heating due to the intense friction between the air and the surface of the hypersonic vehicle [6,7]. To ensure the integrity and reliability of the thermal protection system, extensive ground thermo-mechanical tests are necessary, with precise deformation measurement serving as an indispensable component of these tests. In short, accurate high-temperature deformation measurement plays a vital role in comprehending the mechanical behavior and response of materials and structures under extreme thermal conditions.
Among the various techniques employed in the experimental mechanics community for deformation measurement, digital image correlation (DIC) has emerged as the most widely adopted tool for quantitatively and non-intrusively assessing surface strains at elevated temperatures. This non-contacting, non-interferometric technique offers the advantage of providing full-field information on material behavior and deformation characteristics under diverse thermo-mechanical loading conditions [6]. The initial application of DIC-based high-temperature deformation measurement was reported by Turner and Russell in 1990 [7]. They utilized two-dimensional digital image correlation (2D-DIC) with a single CCD video camera to determine thermal strains and coefficients of thermal expansion (CTEs) for metal samples up to a temperature of 600°C. However, the 2D-DIC method, relying on a single fixed camera, is constrained to in-plane deformation measurement of nominal planar objects [8–10]. To ensure accurate measurements in broader applications, the stereo-digital image correlation (stereo-DIC), also known as 3D-DIC, has been proposed as an extension of the 2D-DIC approach. By utilizing two synchronized cameras, stereo-DIC mitigates the effects of out-of-plane displacement and enables precise measurement of 3D deformation on both planar and curved surfaces. As a result, stereo-DIC has gained prominence as a practical solution for high-temperature deformation measurement of various materials and structures [11–14].
Being an image-based optical technique, the feasibility and accuracy of stereo-DIC measurements heavily rely on the quality of recorded images. Initially, almost all homemade or commercial stereo-DIC systems use white or natural light to illuminate the surface of test objects, ensuring that the image intensities are dominated by the actively illuminated or natural light. However, when conducting thermo-mechanical tests at elevated temperatures, obtaining high-quality digital images becomes challenging due to the intensified thermal radiation emitted by the heated sample and the surrounding heating elements [15–17]. These thermal radiation can soon exceed or even overwhelm the illuminating white or natural light, resulting in heavily saturated image pairs that will corrupt DIC measurements. To address this issue, active-imaging stereo-DIC techniques [18–22] have been developed and accepted as a standard practice for high-temperature DIC measurement. These techniques utilize bandpass filters and monochromatic light illumination, with the core idea being the suppression of undesired light rays through spectral domain filtering. By employing other optical filters such as neutral density and linear polarizing filters, the applicable temperature range of high-temperature DIC methods has been extended to 2000°C or even 3000°C [22]. However, the bandpass filtering in spectral domain may fail when dealing with tests conducted under strong, time-varying light and thermal radiation, particularly in deformation measurements involving transient aerodynamic heating and arc-heating. Although the automatic camera exposure time control strategy [23,24] can adjust the camera's exposure time, it is limited by the minimum exposure time of conventional cameras (e.g., 1 ms) and cannot adequately adapt to rapidly changing thermal radiation. Recently, we proposed a time-gated active imaging 2D-DIC technique [25,26] based on a dual-filtering strategy in both the time and spectral domains for high-temperature deformation measurement. However, this approach is only applicable to in-plane deformation measurements of planar objects and encounters challenges such as high cost and difficulties in synchronizing two gated single-photon cameras with nanosecond-level exposure times when extending the method to stereo-DIC measurement.
In this work, we proposed a single-camera dual-filtering stereo-DIC method based on a four-mirror adapter and the dual-filtering strategy for full-field 3D deformation measurement in the presence of strong light and thermal radiation. This approach first adopts a gated CMOS camera with an ultrashort exposure time for imaging and a synchronized pulsed laser for illumination. With the aid of the bandpass filtering in spectral domain and the time-gated imaging technique in time domain, the enormous thermal radiation from the heated sample and the heating source can be suppressed to a negligible level compared with the active illumination. Meanwhile, a four-mirror adapter is placed before the imaging camera to split the incoming scene into two sub-images, simulating a stereovision system using two virtual cameras. The utilization of a pseudo stereovision system provide an affordable substitute for capturing two views using a single camera, greatly reducing the system cost and avoiding the strict synchronization of two cameras. Experimental evaluations, including assessments with laboratory experiments and validations on real thermal deformation tests under transient aerodynamic heating and direct ohmic heating, demonstrate that the proposed single-camera dual-filtering stereo-DIC method can achieve accurate 3D shape, motion and deformation measurement, even with strong light and thermal radiation from the quartz lamps and the heated sample.
2. Method
2.1 System configuration
The schematic diagram of the single-camera dual-filtering stereo-DIC system is illustrated in Fig. 1. This system is composed of a gated CMOS camera, an optical bandpass filter, a high-power pulsed laser, a timing control unit, and an optical attachment comprising two planar mirrors and a right-angle prism. To mitigate the influence of ambient light from heating elements and strong thermal radiation from the heated sample, a dual-filtering strategy is employed by integrating an optical bandpass filter and a gated CMOS camera with an ultrashort exposure time. By combining spectral bandpass filtering and time-gated imaging techniques, the significant thermal radiation from the heated sample and the heating source can be effectively suppressed, making it negligible compared to the active illumination. Moreover, to avoid the high cost of using two gated cameras and the complexities associated with synchronizing them, a single-camera stereovision approach is adopted for 3D deformation measurement [12,27]. As shown in Fig. 1, the right-angle prism is securely positioned in the middle of the optical attachment, while two exterior mirrors are firmly mounted on the outside support, set at pre-estimated angles and sizes based on our previous design strategy [28]. This optical attachment facilitates the projection of two views of the test object surface via different optical reflection paths onto two halves of the gated CMOS sensor. The utilization of this optical attachment yields several advantages, including reduced setup costs, avoidance of strict camera synchronization requirements, and possession of similar intrinsic calibration parameters across different views.
2.2 Suppression of the strong light and thermal radiation by a dual-filtering strategy
The essence of the dual-filtering strategy involves a twofold approach: 1) bandpass filtering in the spectral domain and 2) time-gated imaging in the temporal domain. Initially, the utilization of a narrow-band optical bandpass filter facilitates the implementation of bandpass filtering to eliminate thermal radiation. The optical filter effectively minimizes the detected radiation energy captured by the camera sensor. Consequently, employing an illuminating light source with a corresponding bandpass wavelength results in the captured image's predominant dependence on the illumination light. This approach signifies a notable reduction in the impact of ambient light and intense thermal radiation on the imaging process. Nevertheless, spectral-domain bandpass filtering might prove inadequate when confronting experiments conducted under conditions of potent, fluctuating light and thermal radiation. The dominance of robust light and thermal radiation over the grayscale image's composition could potentially match or surpass that of the active illumination. In response to this challenge, the system incorporates the time-gated imaging technique to further diminish the influence of intense light and thermal radiation in conjunction with the bandpass filtering approach.
Figure 2 shows the principle of the time-gated imaging technique, which is based on time of flight (TOF) with precise time delay control and ultrafast gated camera. As shown in Fig. 2(a), the laser module generates an ultra-short high-power laser pulse with a certain wavelength (e.g., 860 nm). The ultra-short laser pulse reflects off the object and returns to the gated camera that has an electronic circuit for shutter (gate) control, as shown in Fig. 2(b). The electronic circuit, which controls the shutter of the gated camera, opens the shutter synchronizing with the front part of the width of the laser pulse that is reflected back from the object and closes the shutter synchronizing with the trailing art of the width of the laser pulse. As a result, the camera obtains observation images of objects only within the range of the gate on/off pulse width time slot, as shown in Fig. 2(d). It is noteworthy that the pulse width can often be configured at nanosecond or even picosecond scales. In contrast, the exposure time of conventional industrial cameras is confined to merely a few milliseconds, marking a difference spanning several orders of magnitude. Meanwhile, to ensure an ample quantity of active illumination during the constrained gate on/off time, the system employs a high-power laser pulse as its light source. As such, the ambient light and the thermal radiation entering the camera can be further reduced to a negligible level compared with the active pulsed laser, separating most of the strong ambient light and thermal radiation from the target signal light, as shown in Fig. 2(d). Note that, a cost-effective stroboscopic stereo-DIC method [29] was proposed to achieve transient image acquisition for a rotating blade, which records the image by one exposure or multiexposure of the rapidly rotating blade using a powerful flashlight with a pulse period of 100 ns and a normal CCD camera with a exposure time of 3 ms. Different from the stroboscopic approach, the proposed method allows for a reduction in exposure time to the nanosecond scale, effectively mitigating thermal radiation emitted by high-temperature objects.
2.3 3D deformation measurement by using single-camera stereo-DIC with a four-mirror adapter
As described above, the established system is capable of capturing clear images comprising two sub-images with the aid of the dual-filtering strategy and the four-mirror adapter, even in the presence of strong light and thermal radiation. To measure the 3D shape and deformation of the object surface, a series of images of a planar calibration target with regularly spaced circular dots are taken through translation and/or rotation, serving to establish the world coordinate system. Then, surface images of the test object in different configurations, each containing two views of the object surface, are captured. These recorded images, comprising both calibration and object images, are then separated into left and right sub-images. These sub-images represent virtual image pairs captured by a pseudo stereo-DIC system, as shown in Fig. 3.
Using the left and right calibration images, the intrinsic and extrinsic parameters of the pseudo stereo-DIC system are determined through regular stereo-calibration. The left and right object images, i.e., virtual image pairs, are then used to calculate the disparity data, which signifies the differences in image coordinates between the two projection points, necessary for 3D shape reconstruction. To precisely measure the 3D shape and deformation on the object surface, the regular stereo-DIC technique endeavors to recover the 3D coordinates of a point on the object surface concerning a world coordinate system. By matching the left and right object images of the initial state, the desired disparity data of the initial state is obtained. Based on these disparity data and the previously determined calibration parameters, the 3D shapes of the region of interest (ROI) at the initial state are reconstructed using the triangulation principle. Likewise, the profile of the ROI after deformation can also be reconstructed. By computing the difference between the 3D coordinates of the deformed state and the initial state, 3D full-field displacement fields of different deformed states are determined. Finally, the full-field strain maps of the deformed state are calculated by differentiating the displacement fields using a point-wise least square strain estimation approach.
3. Experiments
To validate the effectiveness and precision of the established single-camera dual-filtering stereo-DIC system, a series of experiments were conducted. These experiments encompassed the acquisition of images from a working tungsten bulb, as well as measurements of shape on a cylindrical surface, in-plane and out-of-plane displacement measurements of a planar plate in translation. Figure 4 provides an illustration of the single-camera dual-filtering stereo-DIC system that was employed for the translation tests. As depicted in Fig. 4, the single-camera dual-filtering stereo-DIC system comprises several key components, including a gated camera (12-bit, GCMOS, Intelligent Scientific Systems, China), an imaging lens (Xenoplan 1.4/23 mm compact, Schneider Optics, Inc., Germany), a four-mirror adapter, a bandpass filter (with a center wavelength of 860 nm and a full-width at half-maximum (FWHM) value of 10 nm), a high-powered pulsed laser for illumination (860 nm, peak power: 600 W, pulse width: 150 ns), and a beam expander. During the test, the gate width of the gated camera was set as 150 ns. Note that the established system operates in an internal trigger model, i.e., the camera open or close the gate according to the frequency and gate width generated by the camera's built-in sequencer. A comprehensive summary of the specific test configurations is provided below:
- 1) To verify the effectiveness of the established system in the presence of strong light and thermal radiation, a simple test of image collection of a lighting tungsten bulb was first performed. During the test, the established imaging system was first placed before the bulb, which was illuminated by the pulsed laser. Then, several images were captured by approximatively adjusting the power of the light from 0W to 40W. In order to ensure precise opening and closing of the gate upon the arrival of the pulse at the camera, it is imperative to establish an appropriate delay time for the pulse output channel. This delay time is linked to the inherent delays associated with the laser and gate, as well as the TOF of the pulse laser. The determination of this delay time involves executing a “sequence recording” operation within the established system. To elaborate, the laser initiates a continuous generation of pulses, subsequently prompting the camera to open the gate after a specified time delay ranging from the Start Position to the End Position, with a small time interval (e.g., one or several nanoseconds). The gate is then closed with the same gate width. The cumulative grey intensities of these images are computed, and the delay time corresponding to the maximum total grey intensity is identified as the optimal delay time. Additionally, the TOF can be ascertained by considering the optimal delay time, along with the inherent delays of the laser and gate.
- 2) For the 3D shape measurement experiment, a glass bottle with a cylindrical surface was selected as the test specimen. Preparatory to the experiment, the glass bottle was initially coated with white spray paint to create a white background. Subsequently, random speckle patterns were applied to this background using a black marker pen. The test object was positioned at a suitable distance in front of the established system. A single image of the bottle surface, along with a set of calibration images, was acquired during the test.
- 3) In the 3D displacement measurement, we conducted tests involving both in-plane (X direction) and out-of-plane (Z direction) rigid-body translations of a flat plate measuring 100mm × 100mm × 5 mm. To facilitate these translations, a 2-axis translation stage with a positioning accuracy of 10µm was employed. The test plate was positioned before the single-camera dual-filtering stereo-DIC system. During the translation tests, the flat plate was securely affixed to the 2-axis translation stage. The plate underwent successive translations first along the X direction and then along the Z direction, covering a range of −5 mm to 5 mm in increments of 1 mm between each consecutive position. For each translation, whether in-plane or out-of-plane, an image was captured.
4. Results
4.1 Image acquisition of a lighting tungsten bulb
Figure 5 shows the recorded images of a lighting tungsten bulb by using a normal camera and the established system. Usually, the high-resistance tungsten filament heats up after switching on the light, and when it reaches a high temperature, it produces light. As shown in Fig. 5(b-f), when the power gradually increases, the tungsten filament initially appears dim red, with a power of approximately 8W. When the power reaches 40W, it emits white light resembling natural light. At this moment, the temperature of the tungsten filament may approach or even exceed 2000°C. By contrast, the tungsten filament can be clearly observed by the established system as most of the thermal radiation is greatly eliminated, confirming the effectiveness of the established system in the presence of strong light and thermal radiation.
Fig. 4. An illustration of the dual-filtering single-camera stereo-DIC system for the translation tests.
Fig. 5. Recorded images of a lighting tungsten bulb with different power by using (a-f) a normal camera and (g-i) the established dual-filtering single-camera stereo-DIC system.
4.2 3D shape reconstruction of a cylinder surface
Figure 6(a) displays an image acquired through the implemented system. A rectangular ROI was initially designated in the left sub-image of the bottle surface, employing a grid step of 4 pixels. Subsequently, regularly spaced calculation points within the ROI were tracked in the corresponding right sub-images to determine their disparity data with a subset size of 41 × 41 pixels. The 3D coordinates of these points of interest were then retrieved by using the calibrated extrinsic and intrinsic parameters along with the disparateness data. The reconstructed surface shape of the bottle conforms closely to the actual surface profile. Through the application of the least square fit method to the 3D coordinates of the cylinder surface, the cylinder's diameter was computed as 76.94 mm. A comparison with the physically measured size (76.00 mm) using a Vernier caliper yielded relative errors estimated at 1.23%, affirming the precision of the single-camera stereo-DIC system devised for shape measurement.
Fig. 6. (a) An image recorded by the established system with a defined ROI, (b) the reconstructed 3D shape of the bottle surface within ROI, (c) the shape profiles at different sections.
4.3 3D displacements measurements of a translated plate
By processing the images recorded during the in-plane and out-of-plane translation tests, full-field 3D displacements within the specified ROI were retrieved for each image. Subsequently, the measured displacements at regularly spaced calculation points were averaged and compared with the applied displacements. Figs. 7(a) and (b) depict the measured 3D displacements plotted against the applied displacements for in-plane and out-of-plane translation tests, respectively. As evident from these figures, the measured X-directional (U-displacement) for in-plane translation tests and Z-directional (W-displacement) for out-of-plane translation tests exhibit a noteworthy conformity with the prescribed values. In contrast, the other two directional displacements are approximate zero, given the absence of external displacement in these specific directions.
Fig. 7. The measured 3D displacements as a function of the applied (a) in-plane translations and (b) out-of-plane translations.
5. Applications to high-temperature deformation measurement tests
5.1 Thermal expansion measurement of a stainless-steel plate subjected to transient aerodynamic heating
To validate the efficacy and precision of the established system, the single-camera dual-filtering stereo-DIC system was employed to measure the thermal deformation of a stainless-steel plate (material type: No.1Cr18Ni9Ti, physical dimensions: 100 mm × 100 mm × 2 mm) subjected to infrared heating. The CTE for the material are well-documented in material handbooks [30]. To ensure the reliability and accuracy of measurements, high-temperature speckles were applied to the specimen surface through air plasma spraying (APS) and a flexible speckle template [31]. Subsequently, the prepared test sample was positioned vertically on the heating platform, approximately 200 mm in front of the quartz lamps of the infrared heating device, as depicted in Fig. 8. To detect the temperature on the sample surface subjected to aerodynamic heating, two thermocouples were welded onto the center and edge of sample surface. The infrared heating device can heat the specimen rapidly from room temperature to a high temperature under the closed-loop control from the thermocouple. Due to the thermocouple's direct measurement of the specimen temperature as opposed to ambient air temperature, the application of thermal loading achieves heightened accuracy and stability. Prior to heating, the specimen surface was evenly illuminated with an invisible pulsed laser, and meticulous adjustments were made to the imaging system to produce a clear image with sufficient contrast. The gate width of the gated camera was also set as 150 ns. Throughout the experiment, the test samples underwent incremental heating from the initial room temperature to 100 °C and further elevated to 1100 °C in increments of 100 °C, with an image captured at each temperature step. Figure 8(b, c) illustrate the images captured at the temperatures of 600°C and 1100°C. Note that, due to the overwhelming light from the lateral quartz lamps, a clear image contrast reduction can be observed from the image recorded at 1100°C.
Fig. 8. (a) Experimental arrangement for the thermal deformation measurement of a stainless-steel plate subjected to transient aerodynamic heating, and (b, c) the recorded surface images at the temperatures of 600°C and 1100°C.
By processing the captured images using the regular stereo-DIC algorithm, the full-field surface displacements and strains were obtained. The thermal strains in the x- and y-directions were determined by computing the average values. Subsequently, the average strains of stainless-steel materials at varying temperatures were computed and presented in Fig. 9. The linear fit of strains in the plot was utilized to derive the CTE in both directions. The CTE values for the stainless-steel materials were estimated to be 18.96 × 10−6 and 18.4 × 10−6 by linearly fitting the thermal strain-temperature curves respectively, with a reference value of 18.7 × 10−6 at the temperature ranging from 0∼649°C. The measured CTEs of stainless steel closely correspond to the reference values, affirming the accuracy of the established system for thermal strain measurement. Notably, the insert figures (radial displacement fields) visually demonstrate evenly spaced contour lines resembling concentric circles, indicating a homogeneous expansion. These outcomes align well with the expectations of practical thermal expansion.
Fig. 9. Thermal strains of the stainless-steel plate measured by the established single-camera dual-filtering stereo-DIC system. The insert figures show the radial displacements (units: mm) at different temperatures.
5.2 Tensile strain measurement of a carbon–carbon composite material sample at elevated temperature
To further verify the accuracy and effectiveness of the proposed single-camera dual-filtering stereo-DIC system for high-temperature strain measurement, a tensile test of carbon–carbon composite material sample was performed. Figure 10(a) depicts the carbon–carbon composite material sample, with the entire length measured at 130 mm, and the specific tensile section gauged at approximately 40 mm. The specimen's diameter was determined to be 8 mm. The configuration for the experimental setup employed in high-temperature tensile strain measurement, utilizing the established system, is illustrated in Fig. 10. As depicted in Fig. 10, exclusively the central observation window was employed for imaging the test sample through the established single-camera system. The middle observation window was big enough to capture sub-images from both the left and right optical paths. Simultaneously, the pulsed laser illuminated the test sample from the right observation window. Thermal and mechanical loading during the high-temperature tensile test was realized through a high-temperature universal testing machine equipped with sealed chambers. The sealed chamber serves the purpose of creating a vacuum environment, thereby eliminating potential image distortion caused by heat haze between the specimen and the heating source. Preceding the test, high-temperature speckle pattern was prepared by blending white aluminum oxide powder with a liquid composition of a commercial high-temperature inorganic adhesive (silicate adhesives). This concoction produced a white liquid easily applicable to the specimen's surface, forming artificial random speckle patterns conducive to DIC matching. Next, the speckled sample was inserted into custom grips for further testing. During the test, the carbon–carbon composite material sample was first heated by the direct joule heating (electric circuit) from the room temperature to 1600°C to assess the effectiveness of the established system in the presence of strong thermal radiation. We recorded the surface images of the test sample at the temperature of interest. Note that the sample temperature was measured by a non-contact pyrometer at the back surface of the sample. Then, the temperature was set to 1300°C, and a preload of about 100 N was applied to improve the contact between the sample and the fixtures, avoiding small rotations of the sample during the tensile test. The sample was then loaded in displacement control mode at a constant cross-head speed of 1 mm/min from 500N to 4500N at a load step of 500N. For each step, one image was recorded.
Fig. 10. Experimental set-up for the high-temperature tensile strain measurement using the established system.
Figure 11 shows the images of the sample surface recorded by a normal camera at different temperatures and the left sub-images of the test sample captured by the established system. Clearly, with the increase of the sample temperature, strong thermal radiation is emitted from the test sample, thus covering the speckle pattern on the sample surface. With the aid of the dual-filtering strategy, the thermal radiation can be greatly suppressed, as shown in Fig. 11(f-j). To eliminate the strain errors due to the out-of-plane motions during loading, we calculated the 3D coordinates of two points of interest, as shown in Fig. 12(a). Then the tensile strain can be determined by monitoring the length change of these two space points. Figure 12(b) shows the measured tensile strains of the test sample as a function of the applied load at 1300°C. The Young’s modulus of the carbon–carbon composite material sample was then evaluated as 30.95 Gpa by the linear fit of tensile strain-load curve.
Fig. 11. (a-e) Images of the sample surface recorded by a normal camera at different temperatures, (f-j) the left sub-images of the test sample captured by the established system.
Fig. 12. (a) A full image captured by the established system, (b) tensile strains of the test sample as a function of the applied load at 1300°C.
6. Conclusion
This study establishes a single-camera dual-filtering stereo-DIC method for full-field 3D shape, motion, and deformation measurement, particularly in challenging conditions characterized by intense light and thermal radiation. To mitigate the adverse effects of strong light and thermal radiation, we implement a dual-filtering strategy, integrating narrow bandpass optical filtering in the spectral domain and ultrashort exposing in the time domain. Additionally, a four-mirror adapter is incorporated into the time-gated imaging system to facilitate single-camera 3D shape and deformation measurements. The efficacy of the proposed method in mitigating the strong light and radiation, along with the accuracy of the 3D measurements, was rigorously validated through experiments including image acquisition of a tungsten bulb under varying lighting conditions, 3D shape reconstruction of a cylindrical surface, and 3D displacement measurements of a translated plate.
Furthermore, the efficacy and precision of the established system in real high-temperature tests were verified by the thermal expansion measurement of a stainless-steel plate subjected to transient aerodynamic heating and the tensile strain measurement of a carbon–carbon composite material sample at 1300°C. The outcomes of these experiments conclusively establish the viability of the single-camera dual-filtering stereo-DIC as a promising technique for 3D shape and deformation measurements in the presence of extremely strong ambient light and thermal radiation. We contend that this established system holds potential for wider application in high-temperature deformation measurements, especially if coupled with a pulsed laser of shorter wavelength.
Funding
National Natural Science Foundation of China (11925202, 12102022); National Science and Technology Major Project (J2019-V-0006-0099); National Key Laboratory of Strength and Structural Integrity Research Project (LSSIZZYJ202301); Beijing Municipal Natural Science Foundation (3222006).
Disclosures
The authors declare no conflicts of interest.
Data availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
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