Liquid modified photonic crystal fiber for simultaneous temperature and strain measurement

A liquid modified photonic crystal fiber(PCF)integrated with an embedded directional coupler and multi-mode interferometer is fabricated by infiltrating three adjacent air holes of the innermost layer with standard 1.48 refractive index liquids.The refractive index of the filled liquid is higher than that of background silica,which can not only support the transmitting rod modes but also the"liquid modified core"modes propagating between the PCF core and the liquid rods.Hence,the light propagating in the liquid modified core can be efficiently coupled into the satellite waveguides under the phase-matching conditions,resulting in a dramatic decrease of the resonant wavelength intensity.Furthermore,there is a multi-mode interference produced by modified core modes and rod modes.Such a compact(~0.91 cm)device integrated with an embedded coupler and interferometer is demonstrated for high-sensitivity simultaneous temperature(~14.72 nm∕℃)and strain(~13.01 pm∕με)measurement.

Dispersion Effects of High-Order-Mode Fiber on Temperature and Axial Strain Discrimination

A new approach utilizing effects of dispersion in the high-order-mode fibers （HOMFs） to effectively discriminate changes in environmental temperature and axial strain is proposed and experimentally demonstrated. Experimental characterization of a HOMF-based fiber modal interferometer with a sandwich fiber structure exhibits excellent agreements with numerical simulation results. A Fourier transform method of interferometry in the spatial frequency domain is adopted to distinguish mode coupling between different core-guided modes. Distinct phase sensitivities of multiple dispersion peaks are extracted by employing a novel phase demodulation scheme to realize dual-parameter sensing.

Analysis of bulging for high speed continuous casting

In order to research the temperature distribution and mechanical deformation of slab bulging during high speed continuous casting, mathematical models have been developed to analyze the thermal and mechanical behavior of the slab. The thermal history of the slab has been predicted by a two-dimensional transient finite element heat transfer model, whose results serve as the input to the stress model. The stress model has been formulated for a two-dimensional longitudinal plane. In this case,the maximum tensile strain during the bulging process is located at the solidification fi＇ont just past the top of the upstream roll,which may contribute to crack formation. The maximum tensile stresses are located at the cold surface in the middle of the two back-up rolls ,just at the point of the maximum bulging. Stresses near the solidification fi＇ont are small because of the high temperatures which produce lower elastic modulus values. Finally,the effect of the casting speed on the bulging deformation is discussed.

Understanding formation mechanism of ZnO diatomic chain and multi-shell structure using physical mechanics:Molecular dynamics and first-principle simulations

In this paper,the possibility of the monatomic chain (MC) formation for ZnO material was studied by molecular dynamics (MD) simulation.The process of MC formation and the effects of temperature,strain rate and size were studied extensively.The tensile process can be divided to be five stages and the ZnO diatomic chain (DC) can be found.The MD results show that most atoms in MC came from the original surface of ZnO nanowires (NWs).Temperature and strain rate are two important factors affecting the process,and both high temperature and low strain rate in a certain range would be beneficial to the formation of DC.Moreover,the effects of strain rate and temperature could attribute to the Arrhenius model and the energy release mechanism.Furthermore,multi-shell structure was found for the samples under tensile strain and the layer-layer distance was about 3.Our studies based on density functional theory showed that the most stable structure of ZnO DC was confirmed to be linear,and the I-V curve was also got using ATK.

Multi-Pass Simulation of Heavy Plate Rolling Including Intermediate Forced Cooling

Thermomechanical Controlled Processing (TMCP) including accelerated cooling after the final hot rolling pass is a well-established technology,widely applied in HSLA steel plate production.However,there are still certain limitations,especially for thicker plate.The rolling schedule includes a long holding period (HP) after the roughing stage to allow the temperature to fall sufficiently for optimised TMCP during finishing.Intermediate Forced Cooling (IFC) applied during the HP can increase productivity by decreasing the required hold time,can restrict austenite grain growth,and can also improve the subsequent strain penetration in thick plate with further metallurgical benefits.Multi-pass plane strain compression (PSC) tests have been performed on the thermomechanical compression (TMC) machine at Sheffield University including different severities of IFC.Clearly it is impossible to simulate all aspects of the temperature and strain gradients present in thick plates in laboratory specimens,and most of the tests were conducted at temperatures and strains calculated by Finite Element modelling as relevant to specific positions through the plate thickness.However,some aspects of the gradients were addressed with tests using cold platens.The results have indeed shown that IFC can shorten the HP and reduce austenite grain growth and its variation across thick plate.