Dynamic Deflection Measurements Research Articles

Based on Inclinometer to Measure Dynamic Deflection of High-Speed Railway Bridge

The dynamic deflection measurement is an important component to the bridge loading test of high-speed railway bridge. Using inclinometers to test the Dynamic deflection is a good method for High-Speed Railway bridge deflection detection. In this paper, we develop a new inclinometer and a new theory to fast calculate deflection. It has been use to detect the dynamic deflection of Baishui River bridge on FuZhou-WenZhou High-Speed Railway when high speed train runs across at kinds of speed. Results indicate: comparing with the measurement results of photoelectric deflection detection system, all dynamic deflection measurement results of inclinometers are very accuracy. Their deflection curves are also similar. All results also show: Using our inclinometers to test High-Speed Railway bridge dynamic deflection can get precise results and can satisfy the dynamic deflection measurement request of high-speed railway bridge. Comparing with other methods of dynamic deflection measurement, this method is very easy to operate., do not need stop the traffic, and not affected by weather, and not need a static reference point, can measure the dynamic deflection of any beam bridge.

A New System for Dynamic Deflection Measurement of Highway Bridge

The bridge deflection measurement is an important component to the bridge examination and a important target to the security appraises. Using Slope sensor to test the Dynamic deflection is a good way for highway bridge deflection detection. In this paper, we develop a new slope sensor and new theory to fast calculate deflection from slope angle. It has been use to detect the dynamic deflections of songhuajiang bridge on Harbin-Changchuen highway when car cross at kinds of speed. The test result indicates: comparing with the measurement results of photoelectric deflection detection system, the dynamic deflection measurement results of slope sensors are much closed. Their deflection curves are also similar. The result also shows: Using our slope sensors to test highway bridge dynamic deflection can get precise results and can satisfy the highway bridge deflection testing request. It is also very easy to use. You can finish the testing easily and do not stop the traffic.

Evaluation of Damage of Real RC deck slab using Impact vibration examination and Dynamic deflection measurement

Evaluation of Damage of Real RC deck slab using Impact vibration examination and Dynamic deflection measurement

High-Reflectivity Broadband Photonic Crystal Mirror MEMS Scanner With Low Dependence on Incident Angle and Polarization

In this paper, we introduce a single-axis resonant comb drive highly reflective broadband photonic crystal (PC) mirror microelectromechanical systems (MEMS) scanner with low dependence of reflectivity on incident angle and polarization. Two-dimensional PC mirrors have several advantages over metal coatings and dielectric stacks (1-D PCs) as mirrors. They can tolerate much higher processing temperatures and higher incident powers, as well as operate in more corrosive environments than metals. Compared to multilayer dielectric stacks, 2-D PC mirrors are compact and allow for simpler process integration, making them highly compatible with CMOS and MEMS processing. Our PC mirrors show broadband high reflectivity of > 90% in the wavelength range from 1345 to 1490 nm (> 95% for 1380 to 1450 nm) and very low angular and polarization dependence over this same range. The single-axis MEMS scanners are fabricated on silicon-on-insulator wafers with the PC mirrors fabricated in polysilicon films on oxide. Although the scanner presented in this paper is single axis, the low angular and polarization dependence properties of the 2-D-PC mirror also make it useful for dual-axis scanners. The scanners are actuated by in-chip plane electrostatic combdrives on resonance. Dynamic deflection measurements show that the scanners can achieve 20deg total scan angle with an input square wave of 40 V and up to 120deg total scan angle with 190 V at a resonance frequency of 2.03 kHz. Although the achievable scan ranges are very large, the useful scan angles will be limited by the angular and polarization dependence properties of the PC reflector and its application. For the 2-D PC scanner presented in this paper, applications that can tolerate 10% decrease in reflectivity will have a scan range of 20deg.

Optical low-coherence reflectometry for deflection measurement with a fiber Bragg grating cantilever sensor

Optical low-coherence reflectometry (OLCR) for deflection measurement with a fiber Bragg grating (FBG) cantilever sensor is proposed and experimentally demonstrated to reveal the internal structure of the sensing fiber in correlation with its optical properties, which is the first report on a spatial-resolved technique to realize dynamic deflection measurement. The change in the fiber length during a convex or concave deflection of the cantilever sensor detected by OLCR achieves simultaneous determination of the magnitude and direction of the deflection by the use of a standard single-mode telecommunication fiber inscribed with single grating. The FBG plays a key role in selecting pre-strain set point and compensating the environmental temperature fluctuations. The experimental results are in good agreement with the theoretical analysis.

A Large-Area High-Reflectivity Broadband Monolithic Single-Crystal-Silicon Photonic Crystal Mirror MEMS Scanner With Low Dependence on Incident Angle and Polarization

In this paper, we introduce a single-axis resonant combdrive microelectromechanical systems (MEMS) scanner with a large-area highly reflective broadband monolithic single-crystal-silicon (SCS) photonic crystal (PC) mirror. PC mirrors can be made from a single monolithic piece of silicon through alternate steps of etching and oxidation. This process allows the fabrication of a stress-free PC reflector in SCS with better optical flatness than deposited films such as polysilicon slabs on low-index oxide. PC mirrors can be made in IR transparent dielectric material and can achieve high reflectivity over a broad wavelength range. PC reflectors have several advantages over other mirror technologies. They can tolerate much higher processing temperatures and higher incident optical powers as well as operate in more corrosive environments than metals. Compared to multilayer dielectric stacks, PC mirrors allow for simpler process integration, thus making them highly compatible with CMOS and MEMS processing. In this paper, we fabricate a PC mirror MEMS scanner in SCS without any deposited films. Our PC mirrors show broadband high reflectivity in the wavelength range from 1550 to 1600 nm, and very low angular and polarization dependence over this same range. The single-axis MEMS scanners are fabricated on silicon-on-insulator (SOI) wafers with the PC mirrors also fabricated in the SOI device layer. The scanners are actuated by electrostatic comb drives on resonance. Dynamic deflection measurements show that the scanners achieve 22deg total scan angle with an input square wave of 67 V and have a resonance frequency of 2.13 kHz.

Electrostatically deflectable polysilicon micromirrors — dynamic behaviour and comparison with the results from FEM modelling with ANSYS

This paper describes the behaviour of electrostatically deflectable polysilicon torsional micromirrors. The electrostatic behaviouris computed by coupling of mechanical and electrostatic calculations using the FEM program ANSYS. Dynamic deflection measurements on a realized micromirror confirm the results of the simulation. In addition, the dynamic damping behaviour of a polysilicon torsional micromirror is investigated. The pressure dependence of the operation of micromirrors is measured and a comparison with the theory of gas damping is presented.

Static and dynamic hydroelastic instabilities in MTR-type fuel elements Part I. introduction and experimental investigation

Hydroelastic instabilities that occur in MTR-type flat-plate fuel elements have been studied both experimentally and theoretically. The present Part I of the paper reports on the experimental part of the investigation, in which three mock-up plate assemblies were tested from the hydroelastic stability viewpoint. A flow loop was built in which the three assemblies could be subjected to water flow rates, the maximum of which corresponded to 3.5 times the Miller's velocity of the assembly. The plates were instrumented with strain gauges, by means of which both static and dynamic deflection measurements could be made. In addition, it was possible to measure the static pressure profiles in three adjacent coolant channels. The experiments indicated that MTR-type fuel elements are subject to several hydroelastic instabilities. These instabilities were identified as: static divergence at the leading edge, static deformation in the plate array, a low-amplitude vibration in the form of traveling waves, and a high-amplitude vibration or flutter. A support comb across the leading edge of the plate assembly was found to remove the leading-edge static divergence and the flutter instabilities. A time-dependent theoretical analysis of the observed phenomena is to be reported in part II.