scholarly journals Distributed Fibre Optic Sensor-Based Continuous Strain Measurement along Semicircular Paths Using Strain Transformation Approach

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 782
Author(s):  
Prashanth Nagulapally ◽  
Md Shamsuddoha ◽  
Ginu Rajan ◽  
Luke Djukic ◽  
Gangadhara B. Prusty
Keyword(s):  
Optical Fibre ◽  
Steel Specimen ◽  
Strain Component ◽  
Fibre Optic ◽  
Transformation Equation ◽  
Element Analysis ◽  
Vertical Strain ◽  
Strain Transformation ◽  
Strain Components ◽  
Curved Paths

Distributed fibre optic sensors (DFOS) are popular for structural health monitoring applications in large engineering infrastructure because of their ability to provide spatial strain measurements continuously along their lengths. Curved paths, particularly semicircular paths, are quite common for optical fibre placement in large structures in addition to straight paths. Optical fibre sensors embedded in a curved path configuration typically measure a component of strain, which often cannot be validated using traditional approaches. Thus, for most applications, strain measured along curved paths is ignored as there is no proper validation tool to ensure the accuracy of the measured strains. To overcome this, an analytical strain transformation equation has been developed and is presented here. This equation transforms the horizontal and vertical strain components obtained along a curved semicircular path into a strain component, which acts tangentially as it travels along the curved fibre path. This approach is validated numerically and experimentally for a DFOS installed on a steel specimen with straight and curved paths. Under tensile and flexural loading scenarios, the horizontal and vertical strain components were obtained numerically using finite element analysis and experimentally using strain rosettes and then, substituted into the proposed strain transformation equation for deriving the transformed strain values. Subsequently, the derived strain values obtained from the proposed transformation equation were validated by comparing them with the experimentally measured DFOS strains in the curved region. Additionally, this study has also shown that a localised damage to the DFOS coating will not impact the functionality of the sensor at the remaining locations along its length. In summary, this paper presents a valid strain transformation equation, which can be used for transforming the numerical simulation results into the DFOS measurements along a semicircular path. This would allow for a larger scope of spatial strains measurements, which would otherwise be ignored in practice.

scholarly journals Optimisation of Coating Properties for Fibre Optic Smart Structures using Finite Element Analysis

1994 ◽  
Vol 3 (5) ◽  
pp. 096369359400300
Author(s):  
M. Hadjiprocopiou ◽  
G.T. Reed ◽  
L. Hollaway ◽  
A.M. Thorne
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Optical Fibre ◽  
Smart Material ◽  
Material System ◽  
Careful Selection ◽  
Coating Properties ◽  
Stress Concentrations ◽  
Element Analysis ◽  
Selection Of

Finite Element analysis is used to determine and to minimise the stress concentrations which arise in a “Smart” material system due to the embedded optical fibre sensors. The FE results show that with careful selection of the coating stiffness and thickness the stress concentrations caused by the fibre inclusion in the host material can be reduced.

Mechanical Approach for Predicting Fretting Fatigue Strength

2010 ◽  
Vol 452-453 ◽  
pp. 797-800
Author(s):  
M. Jayaprakash ◽  
Yoshiharu Mutoh ◽  
K. Asai ◽  
Kunihiro Ichikawa ◽  
Shigeo Sakurai
Keyword(s):  
Fatigue Strength ◽  
Compressive Stress ◽  
Tangential Stress ◽  
Steel Specimen ◽  
Fretting Fatigue ◽  
Fatigue Tests ◽  
Stress Range ◽  
Element Analysis ◽  
Mechanical Approach ◽  
Good Agreement

Stress distribution at the contact edge is known to have a dominant influence on fretting fatigue strength. Stresses acting on the contact surface are tangential stress and compressive stress. In the present study, fretting fatigue strengths of 12 Cr steel specimen under two different mean stresses have been predicted based on the generalized tangential stress range - compressive stress range diagram. The generalized tangential stress range - compressive stress range diagram was obtained by carrying out fretting fatigue tests and finite element analysis using various steel specimens with various geometries of contact pad from the previous studies. The predicted fretting fatigue strengths were in good agreement with the experimental results.

scholarly journals Implications of information theory in optical fibre communications

2016 ◽  
Vol 374 (2062) ◽  
pp. 20140438 ◽  
Author(s):  
Erik Agrell ◽  
Alex Alvarado ◽  
Frank R. Kschischang
Keyword(s):  
Information Theory ◽  
Optical Fibre ◽  
Optical Fibres ◽  
Limited Capacity ◽  
Fibre Optic ◽  
Precious Resource ◽  
Basic Concepts

Recent decades have witnessed steady improvements in our ability to harness the information-carrying capability of optical fibres. Will this process continue, or will progress eventually stall? Information theory predicts that all channels have a limited capacity depending on the available transmission resources, and thus it is inevitable that the pace of improvements will slow. However, information theory also provides insights into how transmission resources should, in principle, best be exploited, and thus may serve as a guide for where to look for better ways to squeeze more out of a precious resource. This tutorial paper reviews the basic concepts of information theory and their application in fibre-optic communications.

Experimental and Numerical Studies on Microscale Bending of Stainless Steel With Pulsed Laser

1999 ◽  
Vol 66 (3) ◽  
pp. 772-779 ◽  
Author(s):  
G. Chen ◽  
X. Xu ◽  
C. C. Poon ◽  
A. C. Tam
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
Material Properties ◽  
Steel Specimen ◽  
Laser Forming ◽  
Element Analysis ◽  
Bending Angle ◽  
Thermal Residual Stresses ◽  
Property Data ◽  
External Forces

Laser forming or laser bending is a newly developed, flexible technique which modifies the curvature of sheet metal by thermal residual stresses instead of external forces. The process is influenced by many parameters such as laser parameters, material properties, and target dimensions. In this work, a pulsed Nd:YLF laser was used as the energy source. The laser beam was focused into a line shape irradiating on the stainless steel specimen to induce bending. The bending angle was measured at various processing conditions. A finite element analysis was performed with the use of a two-dimensional plane strain model to calculate the thermoelastoplastic deformation process. Experimental measurements and computational results were in good agreement. Numerical sensitivity studies were performed to evaluate the effects of the unavailable material property data at high temperature. It was found that both optical reflectivity and thermal expansion coefficient influenced the bending angle significantly, while other extrapolated material properties at high temperature yielded acceptable results.

The Spectrum of a Bent Fiber Fabry-Perot Interferometer under Small Variations of the Refractive Index of the Environment

2013 ◽  
Vol 677 ◽  
pp. 363-367
Author(s):  
Yuri N. Kulchin ◽  
Oleg B. Vitrik ◽  
Stanislav O. Gurbatov
Keyword(s):  
Refractive Index ◽  
Optical Fibre ◽  
Ambient Medium ◽  
Fibre Optic ◽  
Core Mode ◽  
Wide Range ◽  
Fabry Perot ◽  
Resonance Coupling ◽  
Refractive Index Sensors

The phase of light propagating through a bent optical fibre is shown to depend on the refractive index of the medium surrounding the fibre cladding when there is resonance coupling between the guided core mode and cladding modes. This shifts the spectral maxima in the bent fibre-optic Fabry–Perot interferometer. The highest phase and spectral sensitivities achieved with this interferometer configuration are 0,71 and 0,077, respectively, and enable changes in the refractive index of the ambient medium down to 5∙10–6 to be detected. This makes the proposed approach potentially attractive for producing highly stable, precision refractive index sensors capable of solving a wide range of liquid refractometry problems.

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