共查询到18条相似文献,搜索用时 62 毫秒
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声发射传感器的校准是声发射定量检测技术的前提,互易法和表面脉冲法是目前通常采用的两种校准方法,为探讨其一致性,从互易常数入手,比较表面波互易常数和表面脉冲法中的等效互易常数。通过加载力的等效处理、利用激光测振仪测量质点振速,获得法向速度和所加力脉冲的时域和频域分量,计算得到等效互易常数。同时,建立互易法和表面脉冲法校准系统,对实验结果进行对比分析。互易常数与等效互易常数的计算结果和基于校准系统的实验结果表明,互易法和表面脉冲法之间具有较好的一致性,电信号激励声发射换能器所引起的径向谐振产生的影响,对于互易校准而言可以忽略。 相似文献
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介绍了声表面波(SAW)气体传感器的工作原理及器件制作,提出了1种表面波SO2传感器,它采用三乙醇胺(TEA)覆盖薄膜,分辨率可达70×10-9。还讨论了SAW气体传感器的稳定性、可靠性、灵敏度及选择性等问题,并给出了有关的实验结果。 相似文献
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介绍了一种遥测声表面波压力传感器的原理与设计,其核心敏感部件是由声表面波谐振器组成的振荡器,文中给出了主要的测试结果。 相似文献
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The paper describes the evaluation of thin amorphous magnetic film by using of surface acoustic waves on piezo electric substrate. The obtained experimental data show strong dependence of material parameters on the annealing temperature. The mixed ferromagnetic/SAW devices for electronic applications will be also discussed. 相似文献
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The sensitivity distribution of surface acoustic wave (SAW) resonator sensors is investigated by theoretical and experimental means. It is shown that the sensitivity to mass loading varies strongly across the surface due to the confinement of acoustic energy toward the center of the device. A model is developed for this phenomenon based on the extraction of coupling of modes parameters from a rigorous boundary element method analysis based on a periodic Green's function. As SAW sensors for many applications include a layer covering the electrodes, a new technique is introduced to account for the mechanical interactions with buried electrodes. Using this technique, the sensitivity calculations are found to be in good agreement with measurements. It is also shown that while changes in other parameters influence sensitivity, it is velocity change that most strongly determines overall frequency change 相似文献
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M. A. M. Cavaco M. E. Benedet L. R. Neto 《International Journal of Thermophysics》2011,32(11-12):2343-2350
In several applications in the field of metrology, the direct connection of the sensor element with the respective signal-processing unit of the measurement system is not trivial. It can be mentioned, as an example, the measurement of hot points in electric power substations because of the high electrical potential. To solve that problem, two alternatives were studied, one using active surface acoustic wave (SAW) sensors and other using passive SAW tags. For the passive sensor, a SAW radio-frequency identification (RFID) temperature detector was used. That technology is widely applied for typical transport identification (grain transportation, road traffic control), but its application in the field of metrology is innovative. The variation in temperature makes an alteration in the characteristics of the piezoelectric material of the SAW matrix, changing mostly the resonance frequency. Using SAW?CRFID, the problem of measuring temperature basically is directed to the identification of the frequency of resonance of the SAW. The use of active SAW sensors has been demonstrated to be much more satisfactory for the solution of such a problem because of the limitation in the range of the passive sensors. 相似文献
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Y. Aoki Y. Wada Y. Sekimoto W. Yamaguchi A. Ogino M. Saitoh R. Nomura Y. Okuda 《Journal of Low Temperature Physics》2004,134(3-4):945-958
A surface acoustic wave (SAW) sensor can be used to determine the acoustic properties of liquid He. We applied this sensor for liquid 3He and liquid 4He. Two kinds of SAW were used in this experiment, Rayleigh-SAW and shear horizontal SAW. The damping of Rayleigh-SAW was measured in liquid 4He. The results agreed well with the reported values of the acoustic impedance, and the superfluid transition was clearly seen. The damping and the phase shift of shear horizontal SAW were measured in the normal liquid 3He. Temperature dependence of the damping and the phase shift was analyzed by the viscoelastic model, and the results were compared with the transverse acoustic impedance in the normal 3He. 相似文献
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This paper describes a calibration method for acoustic emission and ultrasonic sensors that is effective from 1 kHz to 1 MHz. The method combines generalized ray theory and finite element analysis to model wave propagation at higher and lower frequencies, respectively. A ball impact is used as a calibration source, a thick aluminum plate is used as the test block, and hot glue is used as the couplant. We demonstrate this method on five commercial piezoelectric sensors: Physical Acoustics (PAC) R15a, PAC WSa, Panametrics V101, Panametrics V103, and Valpey-Fisher Pinducer. Our calibration results show that reflections and other wave phases can be more clearly identified with the less-resonant Panametrics sensors. The PAC sensors have the greatest sensitivity and are able to detect surface normal displacements at least down to 1 pm amplitude in the 100s of kHz frequency band. Aperture effect is minimized by the small size of the Pinducer. Our method focuses on the amplitude response of the sensors (phase is ignored) and extends the calibration to a frequency band that is lower than typical analyses. Low frequency information is useful for determining the seismic moment of a seismic source (analogous to the magnitude of an earthquake) and can increase the amount of information acquired in a single recording. 相似文献
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Monitoring of Impacted Aramid-Reinforced Composites by Embedded PVDF Acoustic Emission Sensors 总被引:1,自引:0,他引:1
Abstract: An embedded piezoelectric [poly(vinylidene fluoride) (PVDF)] thin film sensors system for acoustic emission (AE) was realized to investigate the possibility of monitoring, in real time, the post-impact damage in aramid woven fabric-reinforced epoxy. The same sensors have been used in a previous work on similar specimens tested in flexure but not previously impacted, with the aim of verifying the suitability of these sensors to be embedded and their ability to detect AE signals under loading. This work is a continuation of the previous one aiming at evaluating the ability of these embedded PVDF sensors to point out the presence of impact damage, issue widely studied in literature. Aramid fibre/epoxy composite specimens with embedded PVDFs, previously impacted at different energies, namely 5, 10 and 15 J, were tested using three-point bending tests. It appeared from mechanical tests that the flexural strength decreased passing from non-impacted specimens to those impacted with the highest energy and that the embedment of PVDFs in the laminates did not markedly affect the structural integrity of the impacted composites. The degree of impact damage, represented by the decrease in mechanical properties, has been correlated with the AE activity by means of a parametric analysis of the AE signals detected during post-impact mechanical tests. 相似文献
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基于声表面波传感技术的微液滴检测方法 总被引:1,自引:0,他引:1
为了提高声表面波(SAW)技术用于微液滴体积测量的精度,提出了一种差分面积拟合法.根据声表面波信号的特点分析了差分面积拟合法的合理性,在自行研制的声表面波液滴体积检测系统上对该方法的应用进行了验证.采用两种黏性不同的微液滴,分别为5~9μL的微水滴和微油滴进行了测量.对测得的信号分别采用曲线峰值法和差分面积拟合法与微液滴大小进行回归.实验结果表明,采用差分面积拟合法进行回归得到的模型的相关系数相比采用峰值法提高了4%以上,同时对两种微液滴的预测均方根误差(RMSEP)减小了37%以上,从而证明了该方法的有效性. 相似文献
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Measurement Techniques - The deformation method of determining the metrological characteristics of variable-force measuring instruments is proposed and examined. The method consists in the... 相似文献