西安近代化学研究所

This study investigates an optical fiber Mach-Zehnder interferometric measurement system for measuring the micro-displacement of a target object. The Mach-Zehnder interferometer structure is used to build a heterodyne laser interferometric optical path. In addition, an acousto-optic frequency shifter is used to modulate the frequency of the reference light, and a photodetector is used to interfere with the measurement light containing the displacement information of the object. To solve the problem of frequency drift of the acousto-optic modulator, the radio-frequency (RF) signal of the modulator is taken as the reference signal. Next, a frequency drift is introduced into the measured and reference signals to give them the same frequency shift error. During phase demodulation of the two signals, the frequency shift errors cancel each other out. The signal demodulation uses a correlation phase identification algorithm that can determine the leadlag relationship of the signals, and the displacement and direction information of the object is obtained. Experimental results show that in the displacement range of +/- 25 mu m, the maximum and minimum relative errors of displacement are 0. 78 degrees 0 and 0. 145 degrees 0, respectively, the fitting coefficient for the linear fit R2 is 0. 9999, and the displacement consistency error is less than 0. 033 mu m. The experiments show that the measurement system has good measurement accuracy and stability.

Objective Shock wave is a kind of compression wave in which the wavefront propagates in the form of a synoptic surface in an elastic medium.Its typical feature is the discontinuous abrupt changes of state parameters of the medium on the abrupt surface,such as pressure,density,and temperature.As the study of shock waves progresses,it has been found that shock wave technology has great civilian value,so the measurement of shock wave signals has become increasingly important.The formation and propagation of shock waves are accompanied by overpressure and rapid changes in pressure.The response speed and reliability of the corresponding pressure sensors have more demanding requirements.Traditional electrical shock wave pressure sensors are susceptible to electromagnetic interference,temperature range tolerance,rise time,and other issues,which limit the application of such sensors.Fiber-optic Fabry-Perot(F-P)pressure sensors,as an important branch of fiber-optic sensors,provide new possibilities for dynamic pressure measurement of shock waves due to their advantages of fast response speed,high sensitivity,small size,and high resistance to electromagnetic interference.To achieve the dynamic pressure measurement of shock waves,a thin-film fiber-optic F-P pressure sensor with a fiber-tip coating is studied. Methods The basic structure of the thin-film fiber-optic F-P sensor studied in this paper mainly consists of two gold films with different thicknesses,a layer of parylene film serving as the F-P cavity,and a single-mode optical fiber for optical field coupling.When the shock wave pressure was applied to the end surface of the sensor,the parylene film was subjected to pressure,and deformation was produced,causing a change in the F-P cavity length.This change in length then affected the interference of reflected light produced by the two gold films on the front and back surfaces of the F-P cavity.Before the sensor was fabricated,the optical and mechanical aspects of the sensor were simulated using finite element simulation software,and the performance of the sensor under different parameters was calculated by combining theoretical formulas.In addition,the parameters of the sensor were determined.After the sensor was fabricated,the static and dynamic pressure measurement system was designed and constructed,and the experimental results were analyzed. Results and Discussions In the pressure range of 0-60 MPa,a static pressure measurement experiment is conducted on a thin-film fiber-optic F-P pressure sensor using a bench-top oil pressure pump.The reflected spectrum signal of the sensor is obtained and processed to calculate the cavity length of the F-P cavities of different pressure sensors.From the reflectance spectrum curves(Fig.12)of the wavelength and corresponding light intensity under different pressures,it can be seen that with increasing pressure,the overall reflectance spectrum of the sensor drifts to the left.Based on the wave valley values at different pressures,the length information of the sensor cavity corresponding to the pressure is calculated(Fig.13),yielding wavelength sensitivity and cavity length sensitivity of the sensor of 0.0809 nm/MPa and 0.3200 nm/MPa,respectively,which are consistent with the simulation results.In the dynamic pressure measurement experiments,the sensor successfully captures the shock wave signal with a peak pressure of 7.47 MPa and a rise time of 75 ns(Fig.15). Conclusions For measuring shock wave signals,we propose a thin-film fiber-optic F-P pressure sensor.The effective structure of the sensor is a three-layer structure consisting of gold film,polymer film,and gold film.By utilizing the change of the peak position of the sensor's reflected spectral wave,the sensor causes a change of spectral intensity,so as to realize the measurement of the signal pressure.In the pressure measurement range of 0-60 MPa,the wavelength sensitivity is 0.0809 nm/MPa,and the cavity length sensitivity is 0.3200 nm/MPa.Within the range of dynamic pressure measurement,the sensor can measure the dynamic signals with a pressure rise time of 75 ns and a pressure rise amplitude of 7.41 MPa.The experimental results show that the sensor has a large range of pressure measurement ability and high sensitivity,and it has a small size,light weight,and anti-electromagnetic interference.Therefore,the sensor has greater application prospects in the field of shock wave pressure measurement.

Aluminum powder is the most used metal fuel in explosives industry.The nano aluminum powder has a much higher specific surface area,reaction reactivity and completeness compared with the micron aluminum pow-der.Therefore,the application of nano aluminum powder in explosives will undoubtedly improve the explosive power and the ammunition damage efficiency.This article has systematically reviewed the effects of nano aluminum powder on the detonation performance,safety performance,process performance and other explosive properties.As for the det-onation performance,the nano aluminum powder can improve almost all detonation parameters of the mixed explo-sive,including the detonation velocity and heat,the peak value of shock wave overpressure of air explosion,the total energy of underwater explosion,the peak value of explosion pressure and the rise rate of explosion pressure of the fu-el-air explosives,the metal acceleration ability,arson ability,work ability,and brisance,et al.However,some incor-rect conclusions are often drawn by some researchers due to the low effective aluminum contents of the nano alumi-num powder.In terms of safety performance,the introduction of nano aluminum powder increases the impact sensitivi-ty,friction sensitivity,shock wave sensitivity and thermal sensitivity of mixed explosives,which significantly reduces the ignition energy of explosives and promotes the thermal decomposition of common explosives(such as TNT,RDX,HMX,CL-20,NG,etc.).Therefore,the introduction of nano explosives has a negative influence on the safety per-formance of mixed explosives.In terms of process performance,the nano aluminum powder increases the viscosity of the cast explosive system.However,it reduces the density of the explosive column in the pressed explosive system.Therefore,the introduction of nano-aluminum explosive deteriorates the process performance of the mixed explosive.It is pointed out that it is easy to oxidize in various stages from preparation to storage due to the large specific surface area and high reaction activity of nano aluminum powder,which results in a sharp decrease in the effective aluminum content of nano aluminum powder.This is an important reason why some researchers get wrong conclusions.There-fore,it is necessary to study the preparation methods and storage conditions to make full use of nano aluminum pow-der in explosives.