Fiber optic sensing process control system based on data mining algorithm

A compact fiber Bragg grating (FBG) accelerometer is proposed and investigated in this paper. The sensor is designed to consist of an L-shaped beam structure, an inertial mass and an FBG. The vibration displacement of the mass can be effectively converted into the axial strain of the FBG to realize acceleration measurement through this structure. The natural frequency and sensitivity of the sensor are theoretically analyzed, which largely determine the performance of the sensor. Then, the sensing characteristics of the sensor are tested and verified by some experiments. The research results show that the amplitude-frequency response of the sensor is flat in the frequency range of 50~200 Hz, and the measured natural frequency of the sensor is about 275 Hz. The wavelength of FBG has a good linear response to external acceleration, the average sensitivity is about 54 pm/g, and the linearity is greater than 99.8%. The temperature experimental results show that the sensor has a relatively stable response to ambient temperature, the average temperature sensitivity is low at about 11.5 pm/oC in the range of 27 oC~80 oC, and the heating curve and the cooling curve are in good agreement. The sensor proposed in this paper owns the merits of small size, light weight, compact structure, convenient installation and low cost, and can be applied to medium-low frequency acceleration measurement.

Design and optimization of a Micro-structured fiber temperature sensor based on surface plasmon resonance

An in-fiber Mach-Zehnder interferometer is proposed for the discrimination of strain and temperature. The sensor is based on two cascaded standard single mode fibers using three peanut tapers fabricated by simple splicing. The cascaded structure excites more frequency components, which induce four sets of interference dips in the transmission spectrum. One set of the spectrum dips have different sensitivities to temperature and strain from those of the other three. The sensor can discriminate strain and temperature by monitoring the wavelength shifts of two spectrum dips. Repeated experiments are taken both for strain and temperature increasing and decreasing scenarios. Experimental results show that Dip 1 has an average strain sensitivity of −0.911 pm/µε and an average temperature sensitivity of 49.98 pm/°C. The strain sensitivity for Dip 2 is negligible and its average temperature sensitivity is 60.52 pm/°C The strain and temperature resolutions are ±3.82 µε and ±0.33 °C.

Temperature and stress fields during Laser Cladding determine, respectively, the microstructure and residual stress induced deformation and crack formation. As laser cladding processes find application in manufacturing, understanding of the temperature and stress fields become crucial for development of the relationship between process parameters and service behavior.A two-dimensional model of laser cladding is developed, using the finite element software package ABAQUS. It enables an investigation of the temperature field that develops at the center plane of the material. This temperature field provides the input for a thermal stress analysis, for which generalized plane strain was assumed. The goal of the present paper is to perform a quantitative evaluation of the residual stresses that develop at the two-layered material, as a function of process parameters such as scanning speed, laser power and powder feed rate. Results of the model are presented, as applied to cladding of C95600 on AA333.Temperature and stress fields during Laser Cladding determine, respectively, the microstructure and residual stress induced deformation and crack formation. As laser cladding processes find application in manufacturing, understanding of the temperature and stress fields become crucial for development of the relationship between process parameters and service behavior.A two-dimensional model of laser cladding is developed, using the finite element software package ABAQUS. It enables an investigation of the temperature field that develops at the center plane of the material. This temperature field provides the input for a thermal stress analysis, for which generalized plane strain was assumed. The goal of the present paper is to perform a quantitative evaluation of the residual stresses that develop at the two-layered material, as a function of process parameters such as scanning speed, laser power and powder feed rate. Results of the model are presented, as applied to cladding of C95600 on AA333.

Dual parameter detection without cross-sensitivity is a commonly important need but challenging, as most fiber detection components have a single sensitive mechanism. In this article, an optical fiber probe based on a three-beam Fabry-Perot interferometer (FPI) for temperature and refractive index (RI) measurement was proposed and experimentally realized. Theoretically, such structure has three reflective surfaces, forming three FPIs, and can obtain a hybrid sensing mechanism: wavelength-sensitive to temperature and intensity-sensitive to RI. Experimentally, the chemical etching method was used to form a concave in the fiber tip. Fused together with another section of un-etched fiber, an air bubble can be formed inside the fiber. Then, a cleavage near the bubble can shape the three-beam FPI. Using the fast Fourier Transform, the first-order spatial frequency is corresponding to the air-FPI, and the ratio of the second-order spatial frequency to first-order spatial frequency can describe how many smaller interference periods have been created within one original period due to the cleavage. The test temperature range is 30-40°C with a step of 2°C. The band pass filtering method was used to analyze different frequency components. Experimental results validate that the silica-FP was dominate for temperature sensing, and the average temperature sensitivity was 8.97 pm/°C with repeated linearity over 0.95. The test RI range was 1.3333-1.3908, and average RI sensitivity was 10.05 dB/RIU with repeated linearity over 0.92. Therefore, the proposed structure is a compact and efficient sensing component with hybrid sensitive mechanism that can achieve a temperature-RI dual-parameter measurement.

This paper presents an experiment and analysis on the factors affecting nonlinear evolution of Bragg wavelength with change in temperature in typical bare and embedded fiber Bragg grating-based (FBG) temperature sensors. The purpose of the study was to find the constants in the function required to evaluate temperature from Bragg wavelength shift. The temperature sensitivity of bare FBGs was found to increase with temperature elevation, and is different for FBGs written in different fiber types. The average temperature sensitivity increased by about 20% when the bare FBG temperature was elevated from 25°C to 525°C. The average temperature sensitivity of the embedded FBG sensor, investigated in the temperature range of 30°C-90°C, was a factor of 2-3 times larger than for bare FBG, depending on its fastened length with the substrate. Analytically, it is shown that the nonuniform behavior of temperature sensitivity in bare FBGs is the result of both the thermal expansion effect of the fiber and the temperature derivatives of the effective refractive index. The strain transfer and temperature coefficients of thermal expansion of the substrate affect the nonuniform behavior of temperature sensitivity in embedded FBG sensors.

The Qinghai–Tibet Plateau (QTP) is the highest altitude plateau in the world, characterized by strong solar radiation and large diurnal temperature differences and so on, which brings a great negative impact on the temperature and thermal stress field of asphalt pavement. The purpose of this study is to analyze the temperature field and thermal stress status of asphalt pavement in the QTP to provide a reference for pavement design and maintenance in high-altitude areas. The finite element method was applied to establish the temperature field model to study the distribution and variation of pavement temperature. On this basis, the influence of cooling amplitude on pavement thermal stress was studied during cold waves. In addition to this, the key internal factors affecting the thermal stress of pavement, such as surface thickness, surface temperature shrinkage coefficient, surface modulus, and base modulus, were analyzed by an orthogonal test. It was found that temperature and solar radiation have a significant effect on the pavement temperature field. When the cold wave came, the cooling rate had a considerable impact on the thermal stress of the pavement, that is, every 5 °C increase in cooling rate would increase the thermal stress by more than 50%. The temperature shrinkage coefficient and surface modulus of the surface layer material had the greatest influence on the pavement thermal stress. The thermal stress could be reduced by more than 0.4 Mpa for every 5 × 10−6/°C reduction in the surface temperature shrinkage coefficient or every 1000 Mpa reduction in the surface modulus. This study can provide a reference for improving the temperature field and thermal stress field of asphalt pavement in the plateau area.

With the increasing integration of electronic products, the heat flux density is increasing. Research on the heat dissipation of the PCB attracts more attention. Temperature field of the electronic products always changes a lot, usually leading to a transient stress field in the PCB. Due to the transient temperature field and transient stress field, the PCB’s modal changed. In this paper, the temperature field and the stress field are obtained to explain the reason of the change. The influence on PCB’s modal caused by the temperature field and the stress field are analyzed, on the basis of PCB’s thermal modal analysis, which provide a reference for the PCB design and modal analysis in the future.

Based on Von Mises yield criterion and elasto-plastic constitutive equations, an axisymmetric finite element model of a Gaussian laser beam irradiating a metal substrate was established. In the model of finite element, the finite difference hybrid algorithm is used to solve the problem of transient temperature field and stress field. Taking nonlinear thermal and mechanical properties into account, transient distributions of temperature field and stress fields generated by the pulse train of long-pulse laser in a piece of aluminium alloy plate were computed by the model. Moreover,distributions as well as histories of temperature and stress fields were obtained. Finite element analysis software COMSOL is used to simulate the Temperature and thermal stress fields during the pulse train of long-pulse laser irradiating 7A04 aluminium alloy plate. By the analysis of the results, it is found that Mises equivalent stress on the target surface distribute within the scope of the center of a certain radius. However, the stress is becoming smaller where far away from the center. Futhermore, the Mises equivalent stress almost does not effect on stress damage while the Mises equivalent stress is far less than the yield strength of aluminum alloy targets. Because of the good thermal conductivity of 7A04 aluminum alloy, thermal diffusion is extremely quick after laser irradiate. As a result, for the multi-pulsed laser, 7A04 aluminum alloy will not produce obvious temperature accumulation when the laser frequency is less than or equal to 10 Hz. The result of this paper provides theoretical foundation not only for research of theories of 7A04 aluminium alloy and its numerical simulation under laser radiation but also for long-pulse laser technology and widening its application scope.

The heat damage of wheel tread and rail surface is one of the problems that need to be solved urgently. In this paper, finite element method was used to analyze the problem of three-dimensional wheel-rail thermal contact coupling. The contact patch's size of the cone and the wear type locomotive wheel tread was researched. The thermal-contact coupling was analyzed for wheel-rail temperature and stress field under locked wheel sliding in certain speeds considering the interaction of temperature field and the stress field, the wheel-rail contact problem and the changes of the relevant material parameters with temperature. The results show that the area of contact patch with wear type tread is bigger and its shape is near circular, while the shape of contact patch with cone type tread is slender oval. The material properties, which change with the temperature, has a great impact on the temperature field and stress field. This cannot be ignored. The temperature field has a great impact on the stress field. The trend of temperature's increase and stress' increase is the same. Relative to the cone type tread, the heat damage of wheel and rail is smaller than wear type tread.

Effect of forged substrate geometry on temperature and stress field in additive manufacturing

Ladle is an important apparatus in metallurgical industry and takes charge of transferring molten steel from a converter to procedure of continuous casting or ingot casting. It not only improves production efficiency, product quality and production flexibility massively, but also decreases energy and material consumption. The ladle lifetime influences economic benefit of iron and steel enter- prises directly. Distribution of its temperature field and stress field has a vital effect on the lifetime. Thermal expansion stress is one of important reasons for damage as ladles operate under the condition of high temperature and overload. Under high temperature, thermal expansion is generated in the ladle lining and shell. Thermal expansion stress is introduced when lining and shell deformation arising from thermal expansion is subjected to mutual constraint from the counterpart due to various thermal expansion coefficient. The finite element software is used to establish the ladle model and influence of working lining material thermal conductivity; thermal expansion coefficient, Young's modulus and its thickness on the ladle temperature and stress field are studied. The calculation result indicated the equivalent stress in the ladle enlarged as the thermal conductivity, thermal expansion coefficient, Young's modulus of working-lining material increased and the thickness decreased. Research in this paper plays a referring role in comprehending distribution of temper- ature field and stress field of the ladle and selecting appropriately physical parameters of lining. The actual operation result indicates that the research increases the ladle lifetime effectively and shows its wide popularization value.

Comsol 2D Simulation of Heavy Oil and Bitumen Recovery by SAGD

In the paper the results of evaluation of the temperature and stress fields during four cycles of the heat treatment process of the windmill shaft has been presented. The temperature field has been calculated from the solution to the heat conduction equation over the whole heat treatment cycles of the windmill shaft. To calculate the stress field an incremental method has been used. The relations between stresses and strains have been described by Prandtl-Reuss equation for the elastic-plastic body. In order to determine the changes in the temperature and stress fields during heat treatment of the windmill shaft self-developed software utilizing the Finite Element Method has been used. This software can also be used to calculate temperature changes and stress field in ingots and other axially symmetric products. In the mathematical model of heating and cooling of the shaft maximum values of the strains have been determined, which allowed to avoid the crack formation. The critical values of strains have been determined by using modified Rice and Tracy criterion.

Transient temperature and stress fields on bonding small glass pieces to solder glass by laser welding: Numerical modelling and experimental validation