Investigation on low-temperature characteristics of FBG sensors and the technology to enhance sensitivity
The mode of FBG's temperature-sensing is analyzed to and the low temperature performance of FBG is experimental study. Three package technologies can be used for enhancing the sensitivity of FBG under low temperature; the technologies include capillary steel tube package, metallized package and organic polymer package. The results show that the temperature sensitivity of bare FBG under low temperature is 0.00998 nm /°C, the temperature sensitivity of FBG with capillary steel tube package, metallized package and organic polymer package are 0.0213 nm /°C, 0.0283 nm /°C and 0.1376 nm /°C separately, which are 2.02, 3.30, 10.23 times compared with the bare fiber. The temperature sensitivity of FBG sensor under low temperature could be increased effectively by using package technology.
A Fiber Bragg Grating—Bimetal Temperature Sensor for Solar Panel Inverters
This paper reports the design, characterization and implementation of a Fiber Bragg Grating (FBG)-based temperature sensor for an Insulted-Gate Bipolar Transistor (IGBT) in a solar panel inverter. The FBG is bonded to the higher Coefficient of Thermal Expansion (CTE) side of a bimetallic strip to increase its sensitivity. Characterization results show a linear relationship between increasing temperature and the wavelength shift. It is found that the sensitivity of the sensor can be categorized into three characterization temperature regions between 26 °C and 90 °C. The region from 41 °C to 90 °C shows the highest sensitivity, with a value of 14 pm/°C. A new empirical model that considers both temperature and strain effects has been developed for the sensor. Finally, the FBG-bimetal temperature sensor is placed in a solar panel inverter and results confirm that it can be used for real-time monitoring of the IGBT temperature.
Evaluation of buckling load and dynamic performance of steel shear wall retrofitted with strips made of shape memory alloy
One of the most imperfections of the steel shear wall is out of plane displacements that cause severe damage in both structural and non-structural elements. In this paper, the effects of shape-memory alloys on steel shear walls are investigated. First, a numerical analysis using the finite element method in ABAQUS software has been carried out according to an experimental test. The results of the numerical analysis have been verified with experimental results. Next, shape-memory alloy fibers have been added vertically and horizontally to various parts of the steel shear wall. The results show that retrofitting with the shape-memory alloy reduces the out-of-plane displacement of the steel shear wall under both cyclic and seismic loadings. Besides, the buckling load in the steel shear wall increases when it is retrofitted with the shape-memory alloy. Also, the total out-of-plane movement (accumulated absolute displacements) of the steel shear wall and non-structural damage are controlled by the characteristic of a shape-memory alloy material called “super-elastic”.