Abstract:This paper introduces the principles of contact ultrasonic guided wave temperature measurement technology, ultrasonic internal temperature gradient temperature measurement technology, and cross?beam ultrasonic temperature measurement technology. It describes the research status of ultrasonic temperature measurement technology, and the application cases and test results of ultrasonic temperature measurement technology in engine combustion chamber temperature measurement. This review analyzes the technical characteristics and potential problems of various ultrasonic temperature measurement techniques. It is pointed out that the study of high temperature oxidation resistant waveguide materials is the top priority in the development of ultrasonic guided wave temperature measurement technology. It is proposed that the temperature measurement range can be extended and the temperature measurement accuracy can be improved by developing new materials, new processes and new equipment, and constantly iterating the feature signal recognition algorithm model. This provides reference for further development of acoustic temperature measurement technology.

Abstract:To address the under?sampling issue in blade tip?timing signals and overcome probe limitations, a novel method for extracting blade natural frequencies using single?sensor measurement data is proposed. By constructing multiple virtual signals to frequency?shift the measured signal, the frequency components of dynamically varying signals are extracted, and the natural frequency information of the blades is retrieved in conjunction with prior knowledge. Simulation and experimental results validated the effectiveness and accuracy of this method in natural frequency extraction, and also demonstrated the potential for processing small?sample data. This approach uses only a single blade tip?timing probe, overcoming the restrictions in probe placement. With the minimum number of probes, it resolves the frequency aliasing caused by under?sampling, offering the promising technical support for online monitoring of rotor blades in aero?engines.

Abstract:In order to solve the problem of sensor layout optimization in the process of structural digital twin system construction, structural health monitoring system construction and some structural key information acquisition, a resistance strain sensor layout optimization method based on artificial fish swarm algorithm（AFSA）was studied. The advantages and disadvantages of genetic algorithm（GA）, particle swarm optimization（PSO） and AFSA, which are widely used in intelligent bionic optimization algorithm, were analyzed, and the AFSA was preliminarily determined as the core algorithm of resistance strain sensor layout optimization method; Based on the finite element analysis of the wing truss structure with holes, the stress concentration part was determined as the key part; According to the basic principle of AFSA, the regional coordinate system of resistance strain sensor layout was constructed to transform the problem of sensor layout into the swimming rules of artificial fish swarm and to optimize the layout position of resistance strain sensors; Finally, the optimization results of GA, PSO and AFSA were evaluated by using sensor coverage and optimization time as indicators to further verify the effectiveness of this method. The layout optimization method of resistance strain sensors based on AFSA realizes the rapid optimization of the layout position of resistance strain sensors, and can modify the swimming rules of fish swarm and the number of sensors at any time according to the specific working conditions. It has strong practicality, and can provide solutions and technical references for the sensor layout problems in the construction of digital twins, structural health monitoring and other systems.

Abstract:In order to solve the problems of long cycle, high cost and inability to calibrate thermocouple time constants online in conventional calibration methods, an in?situ online calibration method of thermocouple time constants based on loop current step response (LCSR) was introduced, and the basic principles and calibration methods of the LCSR time constant calibration were emphatically discussed. A comparative study on the calibration of time constants using the hot air tunnel method and the LCSR method was performed in a laboratory environment. The experimental results show that the calibration period of the LCSR method is much lower than that of the hot air tunnel method, and the time constant calibration results are basically the same. Finally, the test application prospect of in?situ online calibration in the real environment of temperature distortion is discussed.

Abstract:In order to solve the problems of deformation failure and low sensitivity of flexible thin?film thermocouples, a thermoelectric sensing model was established and thermal?electrical?force multi?field coupling simulations of flexible thin?film thermocouples were performed. Based on the results, the structural dimensions of the sensor were optimized, and a process method for optimizing the sensitivity by heat treatment was proposed, so as to prepare a thermoelectric Indium Tin Oxide?Platinum (ITO?Pt) thin?film temperature sensor based on polyimide substrate with high reliability and high sensitivity. The calibration test experiment proves that the sensor sensitivity reaches 40.10 μV / ℃, which can effectively meet the temperature testing requirements of human wearable devices and lithium battery health monitoring.

Abstract:In order to solve the complex problem of finely sensing the static pressure distribution and dynamic pressure changes on the wall during high?speed flight of aircraft, a capacitive flexible pressure sensor based on PDMS dielectric material was developed by finely matching the material concentration of PDMS?CNTs and bonding the electrode layer and dielectric layer of the sensor. The difficulty of interface friction and energy loss mismatch between electrode layer and dielectric layer was overcome. The static pressure distribution and dynamic pressure change of the sensor were verified by static/dynamic performance verification experiments. The results show that the developed sensor can detect the static pressure of 0.1 ~ 104.9 kPa, can realize the dynamic pressure detection under the vibration frequency of 10 ~ 2 000 Hz, and has good static/dynamic pressure sensing ability. The flexible pressure sensor can be applied to the complex curved structure of aircraft, and has a good application prospect in optimizing the aerodynamic shape of aircraft.

Abstract:In view of the current status and existing problems of the surface acoustic wave (SAW) torque measurement technology in theoretical analysis, algorithm design and experimental test, the torque measurement technology based on the SAW resonator (SAWR) is studied. According to the feature that the torque on the shaft is transmitted to the SAWR by the strain, the theory model of the strain loading in the Lagrange coordinates is established. The torque coefficient of frequency is defined as an important indicator for cuts optimization, and four SAWRs are designed and produced according to the principle of frequency division multiple access (FDMA). On the basis of the echo characteristics of the SAWR, the measurement methods of the SAWR resonance frequency and their characteristics are summarized. The wireless measurement system for static and dynamic torque are built respectively. The static system utilizes the method of frequency sweep for the signal strength measurement, which combines big step for rough sweep with small step for fine sweep for the purpose of enhancing real?time performance and improving the frequency measurement accuracy. The dynamic system employs the carrier frequency measurement method, and solves the problems of insufficient spectrum resolution and low torque measurement accuracy by the cubic spline interpolation in the frequency domain. The results show that the maximum measurement error of the static system does not exceed 1 N·m when the wireless distance exceeds 20 cm and the torque range is from -80 to 80 N·m; The maximum measurement error of the dynamic system does not exceed 3 N·m when the wireless distance exceeds 20 cm, the torque range is between 0 and 80 N·m, and the rotational speed does not surpass 600 r / min. The results validate the effectiveness of the torque measurement system based on the SAWRs, which provided a new approach for high?precision torque measurement.