Abstract:By investigating the advanced technology of surface pressure distribution test and calibration in the world, the current status of testing and calibration of steady and dynamic pressure distribution tests in wind tunnel is introduced. The representative techniques such as pressure scanning valve and pressure sensitive paint (PSP) in distributed pressure test are selected to illustrate, and the key elements of calibration test including calibration theory, test process and traceability are discussed. By comparing the current situation of calibration technology for wind tunnel pressure measurement at home and abroad, the problems and solutions of calibration for pressure test in China are analyzed, and the development direction of wind tunnel pressure distribution measurement and calibration technology in China in the future is put forward.

Abstract:Aiming at the evaluation and calibration of the total distortion of the partial period sinusoidal signal waveform, a technical solution is proposed, which includes directly using the partial period sinusoidal curve fitting method for parameter estimation and residual estimation, then correcting the distortion according to the measurement system range and effective bit, and finally giving the evaluation result of the total distortion of the partial period sinusoidal waveform. At the same time, the measurement and evaluation of harmonic distortion in the partial period waves are discussed, and the conclusion that the harmonic analysis error of the partial period waveform is large and the evaluation result of the harmonic distortion is much larger than the total distortion is obtained. The harmonic analysis of partial period sinusoidal waveform is not yet practical. Based on a set of ultra-low frequency vibration experimental data, the evaluation results of the total distortion of the partial-period and multi-period sinusoidal waveforms are compared, which verifies the effectiveness and feasibility of the method in this paper.

Abstract:Aiming at the problem of real-time deformation monitoring during the assembly process of aircraft elevators in the aerospace field, a method of component deformation reconstruction based on strain monitoring was studied. The relationship between component surface strain and displacement deformation is theoretically analyzed, and the deformation reconstruction equation is established. The minimum strain error optimization function is used to obtain more accurate end strain, which improves the reconstruction accuracy of the reconstruction equation. The experiment uses the plate-shaped part that simulates the elevator wall plate as the tested component, and through finite element analysis, the feasibility of deformation reconstruction technology is verified. The research results show that under different operating conditions, the overall reconstruction error of the component is less than 5.6%, and the reconstruction error of more than 90% of the reconstruction points is less than 4%. The deformation reconstruction method based on strain monitoring has a good application prospect in real-time deformation monitoring of aviation components.

Abstract:The amplitude of ultrasonic wave is attenuated in propagation, and the attenuation is related to the distance of propagation and the center frequency of ultrasonic transducer. In order to study the frequency effect of high-frequency ultrasonic attenuation, this paper analyzes the amplitude and spectral variation of pulsed ultrasonic wave reflection in water by pulse echo method, and studies the relationships between the amplitude attenuation and the propagation distance of ultrasonic wave in water as well as its ultrasonic frequency. The reflected echoes at different distances are collected, and the echoes are subjected to Fourier transform to analyze the distance effect and frequency effect of ultrasonic propagation attenuation. It is found that the propagation attenuation of ultrasonic waves in water is exponential with distance, and the attenuation coefficients of ultrasonic waves of different frequencies are different. The higher the frequency, the greater the attenuation. The frequency effect of attenuation can effectively explain that the center frequency of the echo pulse signal is much lower than the nominal center frequency of the transducer in high-frequency pulse ultrasonic detection by reflection method.

Abstract:According to the actual demand of railway pantograph and catenary safety monitoring, this paper puts forward the strain test with fiber Bragg grating sensor for real-time detection of changes in carbon slide strain. The contact force is measured by deriving the change of contact force from the strain. The scheme of monitoring pantograph and catenary contact state is introduced, and the feasibility of the scheme is verified from theoretical model and practical test, which provides a feasible solution for pantograph and catenary state monitoring.

Abstract:Due to its excellent mechanical, electrical and optical sensing properties, graphene is expected to become a functional sensitive material for the next generation of wearable electronic devices. Although graphene-based optical fiber Fabry-Perot (F-P) acoustic sensor has the advantages of high sensitivity, miniaturization and anti-electromagnetic interference, it will be affected by temperature drift. The influence of temperature on the sensor mainly changes the F-P cavity length, thereby causing the working point drift and then the change in the optical sensitivity of the sensor. Also, the prestress of graphene film is adjusted. In this paper, an optical fiber F-P acoustic sensor using graphene diaphragm was fabricated and then acoustic test demonstrated the change of mechanical properties of suspended graphene diaphragm, thus achieving the increase of the mechanical sensitivity from 1.80 nm/Pa to 2.44 nm/Pa at 1 kHz.

Abstract:Aiming at the weak output signal of photovoltaic detector in the laser flash thermal diffusivity measurement device, a weak signal amplification and conditioning circuit is designed. The input protection ring technology is used to enhance the anti-interference ability, and the electronic components are selected to improve the measurement accuracy. The Kelvin switch technology is used to realize the automatic switching function to eliminate the interference of the on-resistance. The experimental results show that the circuit has good repeatability, small fluctuation and long-term stability, which provides an important technical guarantee for the application of laser flash thermal diffusivity measurement device.

Abstract:In order to solve the problem of inaccurate detection and recognition of steel tape image caused by uneven illumination, rust spots, stains and other factors, a method of steel scribed line extraction based on Gabor transform is proposed. Through Gabor transformation, the line structure of characteristic direction and specific frequency is filtered and presented. Based on these line structures, the position of the line to be tested in the image is calculated, and then the double edges of the line are fitted by RANSAC algorithm, so as to accurately obtain the center position of the line. Experiments show that the algorithm can recognize the damaged and rusty scribed lines robustly when the quality of scribed lines is poor, and improve the detection accuracy and the robustness of the whole measurement system effectively, which has technical reference value.

Abstract:This paper analyzes the system interface and control logic of a civil aircraft high lift system, and models the system by using state machine modeling tools. At the same time, the original model is modified and optimized. From the consistency of simulation verification and system test results, it can be seen that the modeling method is correct and scientific, which makes the system state flow simple and clear, and improves the efficiency of test and calibration. It provides clear state flow and test calibration process reference for the follow-up system development, especially the implementation of embedded airborne software. It lays a foundation for the research of state machine system.

Abstract:The traditional measurement method of compensated micro manometer adopts manual measurement and human eye reading mode to achieve data acquisition. The uncertainty introduced by human eye reading error accounts for a large proportion in the overall uncertainty of the device. In this paper, a full-automatic compensation type micro manometer is developed. A high-definition camera is used to replace the human eye reading, and the software is used to make logical analysis of the collected pictures. At the same time, the functions of real-time liquid phase temperature measurement, field gravity acceleration measurement and atmospheric pressure measurement, which are not available in the traditional compensation type micro manometer, are added to effectively reduce the interference of each influence on the measurement results. The sliding table motor is used to control the displacement to further improve the measurement accuracy. The experimental results show that the automatic compensation type micro manometer developed in this paper has good accuracy and reliability, and has important technical promotion value.

Abstract:On the basis of LabVIEW machine vision function, using the image processing function of IMAQ Vision/Vision Assistant and the serial communication theory of virtual instrument, a set of automatic calibration device for pressure gauges which integrates image acquisition, machine vision analog reading, decision-making judgment and I/O control is designed. The test results show that the device can realize automatic reading of the pressure value displayed by the pressure gauge using a CCD camera with an error less than one tenth of the dial indexing value, which meets the measurement requirements of pressure gauge. The device achieves full automatic verification functions including fast and reliable verification of pressure gauge, automatic report generation and verification data management.

Abstract:The paper introduces the design ideas of multi-component force and torque calibration device which could actualize continuous load of each component separately or six-component synchronously. Aiming at the characteristics of wide range, large space and high accuracy of the device, the technical difficulties involved in the device development has been explained. Some technical problems about six-component loading together , such as the design principle of six-component load，the mechanical structure design of device mainframe and the design of hydraulic pressure dynamical system have also been analyzed. Finally, the technical capability and test validation of the calibration device has been described.

Abstract:The accuracy of dynamic force applied on specimen by fatigue test equipment is not the same as that of static force, and this perplexes testers and calibrators for a long time. By establishing physical vibration models of fatigue testing equipment, it is concluded that the error of cyclic force is mainly caused by the inertia force of the vibration mass between machine sensor and sample, which are not at the same position. Correction models of inertia force influence on cyclic force amplitude are deduced. After the inertia force influence is corrected, the display force of a fatigue test equipment is consistent with the actual force on the sample at last. The cyclic force calibration system with inertia force correction is established using the acceleration method and the stiffness/displacement method. By way of comparison test and data analysis, both the difference between two correction methods (acceleration method, stiffness/displacement method) and the difference between two calibration methods (sensor method, calibration bar method) are less than 1%. The validity of the inertial force correction model is verified.

Abstract:A dynamic force is the product of mass and acceleration. This paper describes the status of sinusoidal force measuring standard device and the development of sinusoidal force traceability. It is the development direction of the sinusoidal force measurement to measure the acceleration by laser interferometer and trace directly to the mass, length and time according to the definition of dynamic force. In order to reduce the uncertainty of the sinusoidal force measurement, it is very important to accurately measure the acceleration distribution of the loading mass, the coupling between loading mass and force sensor, and the equivalent mass of force sensor end. Based on the elastic dynamics theory, the three-dimensional structure of the mass is simplified into a one-dimensional structure by using the circular plate elastic dynamic model to study the radial distribution of the acceleration. The dynamic model of the bar structure is further simplified into a point to study the axial distribution of the acceleration, and the accuracy of the measurement results of the sinusoidal force is improved.

Abstract:The scene of dynamic force measurement is more and more extensive, and the requirement for measurement accuracy is higher and higher. In order to solve the problem that there is no pulse type dynamic force standard device based on absolute acceleration measurement in China, a pulse force excitation device covering the range of 1~200 kN is established. The experimental results show that the device has good lateral motion ratio and unevenness of table amplitude, and has important technical promotion value. It provides strong support for promoting the application of dynamic force sensor in engineering practice and the development of dynamic force measurement technology.

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