Search for: All records

This paper presents an experimental investigation related to the effect of Freezing-Thawing (F-T) cycles on the volumetric behavior of soils, with particular focus on the impact of the range of freezing temperatures on soils response impact. A reconstituted specimen made up from a commercial silt was subjected to F-T cycles in an 1D cell manufactured in a 3D-printer. The soil specimen was fully saturated, and the test was conducted under open system conditions inside an environmental chamber. Volume changes were recorded using a Linear Variable Differential Transformer (LVDT) during cyclic F-T. The test results show that the impact of the range of the freezing temperature is only relevant in the higher range of freezing temperatures (i.e. near the freezing point), and it tends to reduce significantly as the minimum temperature reduces. The study also shows that stress-history of the soil has a significant influence on the volumetric behavior soils subjected to F-T cycles 

We demonstrate the fabrication of fiber-optic Fabry–Perot interferometer (FPI) temperature sensors by bonding a small silicon diaphragm to the tip of an optical fiber using low melting point glass powders heated by a 980 nm laser on an aerogel substrate. The heating laser is delivered to the silicon FPI using an optical fiber, while the silicon temperature is being monitored using a 1550 nm white-light system, providing localized heating with precise temperature control. The use of an aerogel substrate greatly improves the heating efficiency by reducing the thermal loss of the bonding parts to the ambient environment. A desirable temperature for bonding can be achieved with relatively small heating laser power. The bonding process is carried out in an open space at room temperature for convenient optical alignment. The precise temperature control ensures minimum perturbation to the optical alignment and no induced thermal damage to the optical parts during the bonding process. For demonstration, we fabricated a low-finesse and high-finesse silicon FPI sensor and characterized their measurement resolution and temperature capability. The results show that the fabrication method has a good potential for high-precision fabrication of fiber-optic sensors.