Strain is a parameter which reflect the material and mechanical properties of structures [1, 2]. On the basis of structure strain distribution, we are able to obtain the strength reserve information of main components, thus determine the position of local stress concentration and the actual stress state [3, 4].
The aim of a lot of scientists research is to understand the factors which improve the performance characteristics of different devices. We need to know the deformations of the device components. The strain gauge measurements are effective, but obsolete . It is a method where the number of faults outweighs the advantages. Is there another way to measure deformation? Simpler, cheaper and above all faster? Bragg's research on fiber-optic cables for over a dozen years have given hope.
In 1989, Morey discovered that the optical fiber grating sensor has the advantages of high corrosion resistance, accuracy, and antielectromagnetic interference [5,6]. Its features of being able to transfer and sense at the same time and the strong multiplexing functions plus its convenience in forming sensor networks make it overwhelm the limitations of traditional electric detection technologies. The FBG sensors have gradually become the alternatives of traditional electric sensors [7,8].
In 2004, Zhao et al. [9] designed two schemes of FBG strain rosettes: the rectangular and triangular strain rosettes. They pasted these two forms of strain rosettes on the surface of equal strength beam with an angle and studied the performance of plane strain measurement of FBG rosettes. The experimental results show good agreement with simulation. In 2006, Tan et al. [10] revealed the influence of transverse effects on FBG strain measurement through equal strength beam tests. In 2011, Ramos et al. [11] adopted the embedded FBG strain sensors to design a composite strain rosette. With the comparative analysis between numerical method and experiments under the tensile, bending and other alternating loadings, they got the stress response of the composite strain rosette. In 2012, based on the important role of FBG sensor playing in the concrete bridge strain measurement, as well as the fatigue load of concrete and the steel strain characteristics. Tang et al. [12] carried on the related experimental study to discuss the effects of fatigue loading on concrete and steel strain characteristics.
In this paper I will focus on measuring distortion using FBG sensors. The numerical results and the corresponding experimental data reveals that the FBG strain sensors are stable to be used in the rope health monitoring.
References:
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[9] X.F. Zhao, S.Z. Tian, et al., Experimental analysis of state-of-strain with fiber Bragg grating rosettes, J. Optoelectron. Laser 15 (1) (2004) 65–68
[10] M.F. Tan, S.P. Zhu, The Sensor Characteristics and Test Technology of Fiber Bragg Grating, Wuhan University of Technology Press, Wuhan, China, 2006
[11] C.A. Ramos, R.D. Oliveira, et al., Design and experimental evaluation of a composite strain rosette using fiber Bragg grating source, Microw. Opt. Technol. Lett. 53 (8) (2011) 1853–1857
[12] X.X. Tang, X.Z. Tang, et al., Application of fiber Bragg grating in strain measurement of concrete bridge, Adv. Mater. Res. 368 (2012) 2286–2290.