Surface-plasmon-coupled optical force sensors based on metal–insulator–metal metamaterials with movable air gap

We proposed surface-plasmon-coupled optical force sensors based on metal–insulator–metal (MIM) metamaterials with a movable air gap as an insulator layer. The MIM metamaterial was composed of an air gap sandwiched by a metal nanodot array and a metal diaphragm, the resonant wavelength of which was red-shifted when the air gap was narrowed by applying a normal force. We designed and fabricated a prototype of the proposed sensor and confirmed that the MIM metamaterial could be used as a force sensor with larger sensitivity than a force sensor based on Fabry-Pérot interferometer (FPI).

Electrostatic Analyses for a System Constituted by an Insulating Disk Whose One Plane Surface is Charged and Which is Backed by a Concentric Earthed Metal Disk Smaller Than the Insulating Disk Itself and an Earthed Sphere Approaching the Charged Surface of the Insulating Disk, and Its Application to the Case of a Typical Oxygen Regulator

There is a proposition that the possible occurrence of electrostatic discharges inside an oxygen regulator between charged insulating components, such as diaphragms, and earthed metal components, such as the valve stem, could be a potential candidate responsible for oxygen regulator fires. In this paper, the electric field which might be produced at the tip of the valve stem due to charge produced on the diaphragm of a typical oxygen regulator by deposition of charged dust particles or by their impact on the diaphragm or both has been evaluated. The diaphragm, in many cases, is backed partially by a concentric earthed metal disk. The diaphragm has been modelled as an insulating disk. The tip of the valve stem has been modelled as an earthed sphere which is very small compared to the insulating disk and the backing earthed metal disk. An analytical expression for the electric field produced at the point of the sphere nearest to the charged surface of the insulator has been derived. Our expression takes into account not only the effect of the charge on the insulating disk, but also that due to the presence of the backing earthed metal disk. Results for the magnitude of this electric field have been computed for the case of a sample oxygen regulator. An expression for the critical charge density on the surface of the insulating disk has been derived, and its value has been obtained for the case of our sample oxygen regulator. The electric field inside the non-metal diaphragm has also been evaluated. It appears from our analyses that there is a possibility that an electrostatic discharge might occur inside an oxygen regulator, and with an enriched-oxygen atmosphere being present there, such a discharge could also lead to a fire incident.

Investigation on metal diaphragm of pulse separation device in dual-pulse solid rocket motor

The theories of circular plates with large deflection and fracture mechanics were employed to investigate the calculating formula of stress intensity factor on prefab gap. The relationship of the opening pressure with physical dimensions of hard pulse separation device (PSD) was analyzed to achieve the feasible configuration of metal diaphragm, which could play a very important role in dual-pulse solid rocket motor. Moreover, six specific single-term tests of the metal diaphragm were conducted to validate the computing precision of designing formula. In addition, three kinds of scale experiments, e.g. the bearing test, opening test, and associated test were performed to explore the working characters of hard pulse separation device. The results indicate that the error between the experimental results and designing results is 4.4%, and the method can be applied to design the physical dimensions of metal diaphragm. The performances of bearing ability, sealability, opening and melt of PSD have been demonstrated. The results show that this kind of PSD can satisfy the requirements of dual-pulse solid rocket motor very well.

Study of Three-Component FBG Vibration Sensor for Simultaneous Measurement of Vibration, Temperature, and Verticality

To achieve simultaneous measurement of measurand vibration, temperature, and verticality, a three-component fiber Brag grating (TVFBG) vibration sensor is proposed in this paper. Polymer and metal diaphragm sensitization methods are utilized to improve this sensor measurement sensitivity. Project matrix theory is adopted to analyze this sensor. Theoretically,9×9nonsingular measuring coefficient matrix of this TVFBG sensor made up by three3×3measurand coefficient matrixes is established. In order to effectively extract measurand, Hilbert-Huang transform (HHT) is accepted to process this sensor’s center wavelength signals. Calibration experiments are carried out to verify the performance of this TVFBG sensor. Experiment data confirm that this sensor has excellent frequency response and show good linearity at temperature and verticality measurement. Wrist rotation angle measurement experiment is also implemented to further identify this sensor practical value. Through analyzing by HHT, experiment results show that the angle measurement sensitivities of three fiber Brag gratings which are included in this sensor are separately 25.2 pm/°, 38.2 pm/°, and 38.3 pm/°.