Dynamic Strain Characteristics Research Articles

Phi-OTDR Based On-Line Monitoring of Overhead Power Transmission Line

The overhead power transmission line, as an important component of equipment for long-distance power transmission, is threatened by icing and galloping, which will lead to equipment troubles and cause huge economic loss. Thus, there is a great need for on-line monitoring for transmission lines. Because the photoelectric composite cable, such as optical fiber composite overhead ground wire (OPGW) is widely used, it is possible to introduce distributed optical fiber sensors (DOFS) into transmission line status monitoring. Common schemes based on DOFS usually offer low sensing density and are hard to realize global awareness, while phase sensitive optical time domain reflectometry (Φ-OTDR), as a DOFS that has the characteristic of distributed sensing, is hoping to address the limitation. In this paper, by establishing mathematical models, proposing analytical method, and building demonstration devices to analyze the dynamic strain characteristics of overhead power transmission line, an Φ-OTDR based on-line monitoring scheme of transmission line status is presented and experimentally proved for the first time. The estimation error of sag is less than 5.8% on centimeter scale, and the estimation error of ice thickness is no more than 10.84% on sub-millimeter scale, which gives an accurate description of transmission line status and provides strong support for early warning of transmission line failures.

A dynamic strain-based quench-detection method in an LTS sextupole magnet during excitation and quench

The dynamic strain characteristics and responses of a low-temperature superconducting (LTS) magnet during excitation and a quench are investigated in the present work. For the strain measurements, strain gauges in the form of a half-bridge circuit comprising cryogenic strain gauges and their dummy resistances are embedded directly within the superconducting magnet structure. A wireless high-speed data acquisition system with a resolution of 1 ms is also used to obtain the strain history of the LTS magnet during operation. The dynamic strain induced by thermal or mechanical disturbances is detected promptly and compared with the transport current and temperature signals recorded during a quench. This indicates that the dynamic strain measured in the LTS magnet can capture a quench feature in a timely manner. For a better understanding of the dynamic strain histories in the magnet, the dynamic strain signals are subjected to spectral analysis during the excitation and pre- and post-quench processes. It is shown originally that several spectral peaks on strain measured are always observed at the onset of a quench. Thus, the dynamic strain characteristics and responses provide a evaluation means of superconducting magnet.

A Strain-Based Method to Estimate Slip Angle and Tire Working Conditions for Intelligent Tires Using Fuzzy Logic.

Tires equipped with sensors, the so-called “intelligent tires”, can provide vital information for control systems, drivers and external users. In this research, tire dynamic strain characteristics in cornering conditions are collected and analysed in relation to the variation of tire working conditions, such as inflation pressure, rolling speed, vertical load and slip angle. An experimental tire strain-based prototype and an indoor tire test rig are used to demonstrate the suitability of strain sensors to establish relations between strain data and lateral force. The results of experiments show that strain values drop sharply when lateral force is decreasing, which can be used to predict tire slip conditions. As a first approach to estimate some tire working conditions, such as the slip angle and vertical load, a fuzzy logic method has been developed. The simulation and test results confirm the feasibility of strain sensors and the proposed computational model to solve the non-linearity characteristics of the tires’ parameters and turn tires into a source of useful information.

Dynamic strain measurements of marine propellers under non-uniform inflow

An experimental investigation was conducted to determine the dynamic strain characteristics of marine propellers under non-uniform inflow. Two 7-bladed highly skewed model propellers of identical geometries, but different elastic characteristics were tested at various rotational speeds and free stream velocities in the water tunnel. Two kinds of wire mesh wake screens located 400mm upstream of the propeller plane were used to generate four-cycle and six-cycle inflows. A laser doppler velocimetry (LDV) system located 100mm downstream of the wake screen plane was used to measure the axial velocity distributions produced by the wake screens. Strain gauges were bonded onto the propeller blades in different positions. A customized underwater data acquisition system which can record data off-line was used to record the dynamic strain. The results show that the frequency properties of the blade dynamic strain are determined by the harmonics of the inflow and that the stiffness of the propeller has an essential effect on the dynamic strain amplitudes.

Experimental Investigation of Tire Dynamic Strain Characteristics for Developing Strain-Based Intelligent Tire System

Experimental Investigation of Tire Dynamic Strain Characteristics for Developing Strain-Based Intelligent Tire System

Self-Enclosed All-Fiber In-Line Etalon Strain Sensor Micromachined by 157-nm Laser Pulses

An in-line all-fiber etalon, formed by a self-enclosed Fabry-Perot cavity inside an optical fiber fabricated by using 157-nm laser micromachining, is first demonstrated in this paper. This etalon has almost perfect sensor characteristics, such as excellent interferometric fringe contrast of up to ~30 dB, low thermal cross-sensitivity, great potential to realize mass-production with good reproducibility, low cost, super capability to operate in harsh environments, etc. The static, quasi-static, and dynamic strain characteristics of the etalon sensor are investigated, which prove that such an etalon could meet versatile applications for strain measurement.

0214 ブタ大腿骨の動的ひずみ特性(J19-2 生体計測・制御・シミュレーション,J19 ヒューマンダイナミクス)

In this paper, dynamic strain characteristics under impact load application to lower extremety is investigated to study a pedestrian knee jnjured by traffic accident and load transmission mechanism from cortical to trabecular bone. The hog lower extremity is used and subjected to side impact load. The experimental results show that siginificant difference in load transmission characteristics between lateral and medeial is observed, and that the similar tendency to that by Murase is presented.

Nonlinearities and piezoelectric fields in AlN∕GaN wurtzite heterostructures

A one-dimensional model for examining the combined influence of lattice mismatch, spontaneous polarization, piezoelectricity, strain, and nonlinear permittivity effects is described. Nonlinear permittivity effects in two-layer AlN∕GaN structures used in, e.g., heterojunction field effect transistors are shown to have a significant influence (approximately 20%) in the absence of interface charge screening due to strong electric fields in the thin-film AlN layer. Considerable reductions occur, however, in the electric field when interface charge screening is effectively reducing the importance of nonlinear permittivity effects. Determination of dynamic strain characteristics is performed for the case of a strong dc electric field in the AlN layer (due to short-circuit dc voltage conditions over the full structure) superimposed by a small ac voltage and it is shown that resonance frequencies exist being weakly affected by permittivity nonlinearities. As a corollary, it is found that a nonlinear permittivity analysis indicates that the material sound speed becomes electric field dependent due to piezoelectric coupling.

Inhomogeneous dynamic strain characteristics of ferroelectric relaxors

Abstract We utilize a high resolution fiber optic (FO) interferometer to measure the dynamic small strain effects in relaxor ferroelectrics. The dynamic strain response of both a PZT and PMN based relaxor ferroelectric is characterized as a function of the applied electric field containing both ac and dc components. Using this technique we have found that relaxor ferroelectrics ferroelectrics exhibit a residual strain signal which cannot be understood by the scalar strain-polarization relationship (e = QP2). The effects of large residual strain signal on the performance of high resolution low frequency fiber optic voltage sensors are discussed.