scholarly journals ANALYTICAL MODELS FOR ESTIMATION OF THE MAXIMUM STRAIN OF BEAM STRUCTURES BASED ON OPTICAL FIBER BRAGG GRATING SENSORS

2015 ◽  
Vol 22 (1) ◽  
pp. 86-91 ◽  
Author(s):  
Se Woon CHOI ◽  
Jihoon LEE ◽  
Byung Kwan OH ◽  
Hyo Seon PARK
Keyword(s):  
Maximum Stress ◽  
Strain Sensor ◽  
Elastic Beam ◽  
Analytical Models ◽  
Structural Safety ◽  
Maximum Strain ◽  
Beam Structures ◽  
Linear Elastic ◽  
Measured Strain ◽  
Fbg Sensors

The structural safety of a beam structure is assessed by a comparison between the maximum stress measured during monitoring and the allowable stress of the beam. However, the strain directly measured from a fiber Bragg grat- ing (FBG) strain sensor may not be identical with the actual maximum strain induced in the structural member. Unless a FBG strain sensor is installed exactly on where maximum strain occurs, the reliability of the evaluated safety based on the measured strain depends on the number and location of sensors. Therefore, in this paper, analytical models are presented for estimation of the maximum values of strains in a linear elastic beam using the local strains measured from FBG sensors. The model is tested in an experiment by comparing estimated maximum strain from FBG sensors and directly measured strain from electrical gages. For the assessment of safety of typical beam structures in buildings and infrastructures, analytical models for various loading and boundary conditions are provided.

scholarly journals Verification of the Propagation Range of Respiratory Strain Using Signal Waveform Measured by FBG Sensors

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7076
Author(s):  
Shouhei Koyama ◽  
Atsushi Fujimoto ◽  
Yuma Yasuda ◽  
Yuuki Satou
Keyword(s):  
Fiber Type ◽  
Strain Sensor ◽  
Signal Amplitude ◽  
Living Body ◽  
Fbg Sensor ◽  
Measured Strain ◽  
Signal Period ◽  
Fbg Sensors ◽  
Bragg Grating Sensor ◽  
Strain Signal

The FBG (Fiber Bragg grating) sensor is an optical fiber type strain sensor. When a person breathes, strain occurs in the lungs and diaphragm. This was verified using an FBG sensor to which part of the living body this respiratory strain propagates. When measured in the abdomen, the signal waveforms were significantly different between breathing and apnea. The respiratory cycle measured by the temperature sensor attached to the mask and the strain cycle measured by the FBG sensor almost matched. Respiratory strain was measured in the abdomen, chest, and shoulder, and the signal amplitude decreased with distance from the abdomen. In addition, the respiratory rate could be calculated from the measured strain signal. On the other hand, respiratory strain did not propagate to the elbows and wrists, which were off the trunk, and the respiratory time, based on the signal period, could not be calculated at these parts. Therefore, it was shown that respiratory strain propagated in the trunk from the abdomen to the shoulder, but not in the peripheral parts of the elbow and wrist.

scholarly journals On controllability of a linear elastic beam with memory under longitudinal load

2014 ◽  
Vol 3 (2) ◽  
pp. 231-245 ◽  
Author(s):  
Sergei A. Avdonin ◽  
◽  
Boris P. Belinskiy ◽  
Keyword(s):  
Elastic Beam ◽  
Linear Elastic ◽  
Longitudinal Load ◽  
With Memory

The Damage Tolerance of a Sandwich Panel Containing a Cracked Honeycomb Core

2009 ◽  
Vol 76 (6) ◽  
Author(s):  
I. Quintana Alonso ◽  
N. A. Fleck
Keyword(s):  
Finite Element ◽  
Sandwich Panel ◽  
Finite Element Simulations ◽  
Analytical Models ◽  
Tensile Fracture ◽  
Linear Elastic ◽  
Statistical Variation ◽  
Wall Strength ◽  
Elastic Fracture ◽  
Weibull Theory

The tensile fracture strength of a sandwich panel, with a center-cracked core made from an elastic-brittle diamond-celled honeycomb, is explored by analytical models and finite element simulations. The crack is on the midplane of the core and loading is normal to the faces of the sandwich panel. Both the analytical models and finite element simulations indicate that linear elastic fracture mechanics applies when a K-field exists on a scale larger than the cell size. However, there is a regime of geometries for which no K-field exists; in this regime, the stress concentration at the crack tip is negligible and the net strength of the cracked specimen is comparable to the unnotched strength. A fracture map is developed for the sandwich panel with axes given by the sandwich geometry. The effect of a statistical variation in the cell-wall strength is explored using Weibull theory, and the consequences of a stochastic strength upon the fracture map are outlined.

scholarly journals Measurement of Mechanical and Thermal Strains by Optical FBG Sensors Embedded in CFRP Rod

2019 ◽  
Vol 2019 ◽  
pp. 1-6
Author(s):  
Keunhee Cho ◽  
Sung Tae Kim ◽  
Young-Hwan Park ◽  
Jeong-Rae Cho
Keyword(s):  
Mechanical Properties ◽  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Strain Sensor ◽  
Thermal And Mechanical Properties ◽  
Fbg Sensor ◽  
Thermal Test ◽  
Fbg Sensors ◽  
Thermooptic Coefficient

The present study intends to provide the photoelastic coefficient and thermal expansion coefficient needed to use an FBG-embedded CFRP rod (smart rod) as strain sensor. Due to the monolithic combination of the FBG sensor with a CFRP rod, the smart rod is likely to exhibit thermal and mechanical properties differing from those of the bare FBG sensor. A tensile test showed that the photoelastic coefficient of the smart rod is 0.204, which is about 7.3% lower than the 0.22 value of the bare optical FBG. Moreover, the thermal expansion coefficient of the smart rod obtained through a thermal test appeared to be negative with a low value of −0.190×10−6/°C. Consequently, the temperature dependence of the smart rod is mainly expressed by means of the thermooptic coefficient. Compared to the bare FBG sensor, the smart rod is easier to handle and can measure compressive strains, which make it a convenient sensor for various concrete structures.

scholarly journals Comparison of Ortho-planar Spring design optimization based on Linear Elastic and Hyper Elastic Materials

2018 ◽  
Vol 166 ◽  
pp. 01004
Author(s):  
Ruetai Graipaspong ◽  
Teeranoot Chanthasopeephan
Keyword(s):  
Topology Optimization ◽  
Elastic Material ◽  
Maximum Stress ◽  
Nonlinear Material ◽  
Small Displacement ◽  
Linear Elastic Material ◽  
Output Displacement ◽  
Linear Elastic ◽  
Hyper Elastic ◽  
Matlab Programming

In this paper, compliant Ortho-planar spring was designed based on a three-dimensional topology optimization method. The computation was developed using MATLAB programming. The objective of this work was to apply dual method to design an Ortho-planar spring while the design should have minimum mass and at the same time satisfy a set of constrained displacement. Throughout this paper, we analyzed a method for designing an Ortho-planar spring using linear elastic material and hyperelastic material. The results showed that under small displacement conditions, the output displacement, maximum stress magnitude, and the maximum stress of linear elastic assumption and hyper-elastic material were relatively close to each other. However, the mass fraction and the layout as the result of the optimization process was different. As for larger displacement, the maximum stress of linear elastic material appeared 2.59 times higher than the maximum stress of the hyper-elastic material model. The topology optimization output based on linear material was invalid because the topology of the computed Ortho-planar spring was not appeared as a one-piece layout while the design based on nonlinear material looked promising.

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