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Measuring the temperature and deformation synchronously at elevated temperatures is technically challenging and has become a major concern in the evaluation of mechanical properties. In this study, a simple, easy-to-implement, yet effective monochromatic pyrometry is established for non-contact and full-field temperature measurements, which can significantly reduce the error caused by the camera’s channel crosstalk that commonly occurs in the existing improved two-color method. In addition, high-temperature digital image correlation, combined with band-pass filtering and monochromatic illumination, is applied for deformation measurement. Subsequently, an experimental system was set up to validate the accuracy of the proposed method, which consists of a CCD camera for image capturing, a blue bandpass filter for radiation suppression, blue light irradiation for light compensation, and an infrared pyrometer for temperature recording. The results of the thermal heating experiment on the C/SiC sample proved that the selection of camera channel R in monochromatic pyrometry can reduce the error by channel crosstalk, and the proposed method is applicable for synchronous measurement of temperature and deformation.

In aerospace and related fields, simulation tests in the high-temperature wind tunnel have been playing an important role in evaluating and optimizing the thermal performance of key materials/structures of the aircraft. Based on the characteristics of the test environment, the development of machine vision system for the high-temperature wind tunnel can obtain the wide ranging and comprehensive process information of the tests, which is of great significance to the development of high-temperature ground simulation tests. Thus, this paper reviews the theoretical principles, key technologies and equipment design of the machine vision system for high-temperature wind tunnel. Meanwhile, several application examples are also introduced along with the relevant research results of our research group in this field. Finally, the development direction and application prospects of the machine vision system for the high-temperature wind tunnel are also forecasted with the future-oriented needs of the simulation tests.

Synchronous measurement of temperature and deformation at elevated temperatures is highly critical, yet challenging in evaluating mechanical properties of thermal protection systems. An ultraviolet (UV) imaging system is proposed to obtain noncontact, in situ, synchronous, and full-field temperature and deformation. The established system consists of a monochromatic UV illumination with a bandpass filter for radiation suppressing, a UV CCD camera for image capturing, and an infrared pyrometer for temperature recording. Additionally, an improved monochromatic radiation pyrometry method is proposed, while a deformation measuring method using the UV digital image correlation (UV-DIC) and natural textures-generated speckle is introduced. Furthermore, through camera calibration at room temperature and real-time exposure time adjusted at elevated temperatures, the influence of reflection on radiation pyrometry and unfiltered radiation on DIC analysis is eliminated. Synchronous temperature and deformation fields of C/SiC subjected to flame heating are experimentally measured with a temperature range of 500°C–1500°C, and results demonstrate the efficacy and potential of the proposed system and method. Finally, the importance of exposure time on balancing the light intensity of radiation and reflection is also discussed.

Optical method has been playing an important role in measuring temperature and deformation at elevated temperatures. Here we propose a simple and effective iterative algorithm to realize accurate and simultaneous measurement of the full-field temperature and deformation of specimens subjected to flame heating at temperatures up to 1000 °C. The algorithm separates the optical images of specimen surface into radiant and reflected parts. The radiant part is used to calculate the full-field temperature by an improved two-color method, and the reflected part is used to obtain the deformation of the specimen surface based on high-temperature digital image correlation method. Experimental validation shows that the proposed method can effectively eliminate the mutual interference between the radiation and reflected light, displaying great potential for synchronous measurement of temperature and deformation with sufficient accuracy by using one camera.

Synchronous measurement of temperature and deformation at elevated temperatures based on the noncontact optical method can be achieved through the allocation of channels R, G, and B for a color camera. Channels R and G are used for the radiation-based temperature measurement, while channel B is adopted for the deformation measurement. However, the existence of color crosstalk, which is mainly caused by the color camera's spectral response and the use of the narrow-band filtering technique, has a significant influence on the accuracy of temperature and deformation calculations. In this work, the color crosstalk effect in high-temperature optical imaging is analyzed, and a crosstalk correction algorithm based on grayscale calibration is performed on the different color channels (channels R, G, and B) of the color image. By solving the calibration equations, three corrected color channels are generated for a high-precision temperature and deformation calculation. A flame heating experiment of a C/SiC material up to 1100 °C is carried out to validate the applicability accuracy of the proposed method. The results show that the proposed method can effectively eliminate the color crosstalk between different channels and provide a non-contact, full-field, and synchronous measurement of temperature and deformation with higher accuracy than the existing methods.

Synchronous measurement of full-field temperature and deformation at elevated temperature using non-contact optical methods attracts increasing attention in evaluating the high temperature properties of materials. The current optical methods all face one major challenge, which is the strong light reflection on the surface of the specimen. Such strong light reflection could greatly impair the measurement accuracy of the temperature field measured based on the radiation light information. Here, we develop an effective and simple testing system to overcome this difficulty. The measurement system consists of an image and temperature acquisition device, and a light source with the feature of high-frequency flashing and periodic flicking. High-frequency flashing of the light source is driven by a motor and controlled by a field programmable gate array controller. Our system can realize the synchronous control of light flashing, image capturing, and temperature acquisition. Images with light on are used to calculate the deformation field based on the digital image correlation method, and those with light off (without reflection) are used for the calculation of temperature. Based on the continuous change of temperature over time, the temperature field at the moment when light is on can be obtained by interpolating the temperature fields before and after the moment through the fitted curve. Experimental validation on the thermal heating of C/C fiber composites shows a satisfactory result for temperature and deformation measurement.

Synchronous measurement of temperature and the deformation field can be achieved through reasonable assignment of R, G, and B channels of a CCD camera in a high-temperature environment. The R and G channels are used for colorimetric temperature measurement, and the B channel is adopted for deformation measurement. However, the external blue compensation light source may cause crosstalk of the R and G channels, leading to inaccurate measurement. To eliminate such an interference phenomenon, we first use the function relationship between the illumination of the object surface and the exposure time to calibrate the camera parameters at room temperature, thus removing the initial gray level of the R and G channels in the high-temperature image. This contributes to improving the low-temperature measurement accuracy for the temperature field, with a calculation error of

Synchronous measurement of the temperature and deformation fields of large-scale flat specimens is challenging in engineering experiments, especially for high-temperature environment where the non-contact optical method is attempted. To overcome this difficulty of large-scale flat specimens tested at high temperature in the open arc wind tunnel environment, measurement principles and experiments of large-scale flat specimens based on a multi-camera system are proposed using digital image stitching as well as the improved two-color method for temperature measurement. First, the digital image mosaic method is used to process and evaluate the mosaic effect of multi-camera images, the optimal mosaic parameters are selected, and the calculation results are given. Second, a set of images for large-scale flat specimens are deduced based on an improved two-color method of temperature measurement and digital image mosaic algorithms. A stitching algorithm for full-field temperature measurement and calculation results are given. Finally, full-field displacement of the stitched images is calculated by the digital image correlation method. Synchronous measurement of temperature and deformation established in this paper provides guidance for measurement of large-scale flat specimens with high spatial resolution in engineering tests.

In this work, we develop an optoelectronic system for in situ observation and measurement in hypervelocity flows. The system has the advantages of strong radiation resistance and self-adaptive exposure time of the cameras. Thermal ablation test using flat plate thermal protection system material was carried out in an arc jet. Real-time ablation images were captured and analyzed to understand the thermal ablation mechanism. Through the modified algorithms of particle image velocity (PIV) and image feature detection, the surface recession rate and the velocity distribution of the melted droplets flowing on the sample surface were obtained. The experimental results demonstrate vast potential for using this in situ measuring technique in various engineering applications. Finally, the formation and merging of the melted droplets was analyzed based on energy theory, and the numerical simulation results showed good agreement with the actual experimental results.

sensor node localization is a basic and key problem in sensor network work and management, and the self-localization of the sensor node is the basis for sensor network applications. This paper classifies and compares with several localization algorithms currently used, presents a node localization algorithm based on mobile anchor node, to reduce the communications and computing cost of the wireless sensor network self-localization.

Compared with the conventional solid rocket motor which works in atmosphere, the underwater solid rocket motor has different performance characteristics, because the buoyancy of water cannot be neglected, while in the atmosphere only gravity is present. In order to get a deep understanding of the mechanism of thrust oscillation characteristics and of the jet structure of underwater solid rocket motor, a 3-D numerical simulation using the volume of fluid (VOF) model is given in this paper to investigate the horizontal jet structure and the oscillating flow field induced by the gravity and buoyance. The principle of momentum is carried out to analyze the oscillating flow field in the initial working period. Result of analysis indicates that the behavior of rising gas bubbles is remarkably influenced by gravity and buoyancy. Compared to the conventional solid rocket motor in the atmosphere environment, the phenomenon shows that the rising gas bubbles are more obvious in the water. It is concluded that thrust-gravity and buoyancy coupling can generate bigger roll moment in the vertical direction than the conventional solid rocket motor. Numerical calculations in conjunction with experiment in the references proves that the model contains gravity, buoyancy and the VOF model can be used to describe the jet structure and thrust oscillation of underwater solid rocket motor; gravity and buoyancy cannot be ignored in the research of underwater solid rocket motor performance characteristics.