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Indexed by:期刊论文

Date of Publication:2013-12-01

Journal:JOURNAL OF ENGINEERING MECHANICS

Included Journals:SCIE、Scopus

Volume:139

Issue:12

Page Number:1797-1807

ISSN No.:0733-9399

Key Words:Distributed fiber optic sensor; BOTDR; Crack detection; Strain transfer; Elasto-plastic analysis; Experimental test

Abstract:Development of a model for the analysis of strain transfer mechanism in Brillouin-based sensors with strain singularities is provided in this study. The main objective of the research pertained to the development of a method for accurate detection of cracks and their locations in sensing with Brillouin-based fiber optic distributed sensors. The work involved formulation of a shear lag-based model considering the elastic as well as elastoplastic stages of the fiber optic coating strains. Feasibility of the proposed approach is evaluated through an experimental program. The experimental program involved use of a Brillouin optical time domain reflectometer (BOTDR) for distributed measurement of strain and detection of simulated cracks in a 15-m-long beam. The results indicate that the discontinuities in the strain distribution based on the theoretical analysis provide the means to accurately pinpoint the location of simulated cracks. On the other hand, the distortion effect of the BOTDR system due to averaging of the strains over the spatial resolution of the system masked the influence of strain discontinuities. In contrast to the strains acquired through the averaging process in BOTDR, the theoretical computations pertain to the actual distribution of strain along the length of the beam. Optomechanical relationships were also used to simulate the effect of spatial resolution on the theoretical results. The apparent strains obtained in this way were compared with the BOTDR measured values. Because of the measurement noise, the apparent strains based on the theoretical computations provided better information about the location of the cracks. (C) 2013 American Society of Civil Engineers.