一种光纤EFPI高温传感器

In this paper, we proposed an optical fiber extrinsic FabryPerot interferometer (EFPI) sensor for distance detection of ultrasound signal. This optical fiber EFPI sensor was fabricated with a novel and simple technics. In the experiments, both traditional piezoelectric transducer (PZT) and high voltage electrode discharge were used as the ultrasound signal source. The experimental results indicate that strong ultrasound signals can be detected by the fiber EFPI senor in both cases and the maximum detection distance in the air is more than 180 cm.

An optical fiber sensor network for ultrasonic measurement based on wavelength division multiplexing (WDM) and time division multiplexing (TDM) technology is presented. Each of the sensor probes is an optical fiber extrinsic Fabry-Perot interferometer (EFPI) which is composed of the fiber's end face and the aluminum thin diaphragm. The sensors are arranged in different wavelength domains formed by a wavelength division multiplexer. Each wavelength division multiplexer, with a group of the sensors, is connected to one of the output ports of optical switch to realize TDM. The signal of each sensor is exported sequentially from a tunable narrowband optical filter (TNOF) that queries every sensor though scanning mode. The principle of the phenomenon of phase induced signal fade in interferometric fiber-optic sensors is also analyzed. Nicely, the detection method above implements the operation of anti-phase induced signal fade detection. The system is interrogated by broadband light source. The scanning range of TNOF is full of the bandwidth of the light source. The result of experiment in water show that the sensor sensitivity reaches −162dB(0dB=1rad/μPa), the frequency response range is from 10KHz to 5 MHz. The number of multiplexing sensors based on WDM and TDM reaches to 64.

Optical fiber Bragg grating (FBG) sensors have significant potential for use as embedded devices to monitor the structural integrity of engineering materials. The main drawback of the FBG strain sensor is its cross-sensitivity to temperature. This paper reports a simple scheme for multiplexing a FBG and an extrinsic Fabry-Perot interferometric (EFPI) sensor to enable the decoupling of strain from temperature. The EFPI sensor was constructed using a precision bore quartz capillary tube which housed two cleaved optical fibers. The gap between the fiber end- faces served as the Fabry-Perot cavity. Since the coefficients of thermal expansion between the optical fiber and the capillary tube were similar, the EFPI sensor has a very low sensitivity towards temperature. Therefore, when both sensors are placed close together, the EFPI sensor can act as the strain sensor, and temperature can be determined from the FBG wavelength shift after taking out the strain effect. The signal processing for the EFPI sensor was based on a channelled spectrum method using a CCD spectrometer. The same CCD spectrometer was also used to determine the wavelength shift of the FBG. The cross-talk between the EFPI and FBG sensors was evaluated. The feasibility of conducting simultaneous strain and temperature measurements was demonstrated.

A highly sensitive fiber-optic extrinsic Fabry-Perot interferometer (EFPI) is designed and demonstrated experimentally. The EFPI is composed of two sections of single mode fiber (SMF), a segment of silica capillary tube (SCT), an air cavity, and cured polymer which is filled in the SCT. The sensing part of structure of proposed EFPI is the air cavity, and the cured polymer has a modulating effect on the air cavity. Due to the high thermal expansion coefficient (TEC) of the polymer, the sensor exhibits a high sensitivity to temperature. Experimental results show that the temperature sensitivity of the proposed sensor reaches −2.88 nm/°C with a perfect linearity of 99.88%. Therefore, the proposed sensor with high-sensitivity, ease of fabrication and low cost is favorable to be used in high-accuracy temperature measurement.

Influence of temperature on concrete beams strengthened in flexure with CFRP

Thermal stress is a significant contributor to a component’s failure during manufacturing processes. In the electronic industry, for example, it is very common that components experience an extensive number of nonuniform, local heating cycles throughout its life time. In order to promote reliability, components are put through burn-in which creates a very nonuniform temperature distribution. In order to reduce cost, reworkability is considered to be a necessary option for the manufacturing processes to achieve high yield; these rework processes usually require localized heating. In addition, due to certain functionality requirements, materials with different coefficients of thermal expansion are cast together. The thermal mismatch caused by nonuniform temperature and/or different coefficients of thermal expansion will create thermal stress which could result in the cracking of the components. The fracture often initiates on the interface between the different materials or at the free edge of the surface. To make the problems mathematically tractable, the problems here are simplified as linear thermo-elastic and axisymmetric. It is concluded that the displacement distribution is one order higher than the temperature distribution if the temperature is a polynominal function of the radial distance from the center of a disk. The solutions also show the effect of the edge boundary conditions on the stress level; namely a certain degree of constrained edge support will reduce the tensile stress around the edge of the plate. This will reduce the failure rate of the plate, particularly for a brittle material. Finally, a numerical finite element solution for a square plate with a localized heating source is given to demonstrate the applications of the analytical solutions to fixture design during the process development.

Since the introduction of the first power module by Semikron in 1975, many innovations have been made to improve the thermal, electrical, and mechanical performance of power modules. These innovations in packaging technology focus on the enhancement of the heat dissipation and thermal cycling capability of the modules. Thermal cycles, caused by varying load and environmental operating conditions, induce high mechanical stress in the interconnection layers of the power module due to the different coefficients of thermal expansion (CTE), leading to fatigue and growth of microcracks in the bonding materials. As a result, the lifetime of power modules can be severely limited in practical applications. Furthermore, to reduce the size and weight of converters, the semiconductors are being operated at higher junction temperatures. Higher temperatures are especially of great interest for use of wide-?bandgap materials, such as SiC and GaN, because these materials leverage their material characteristics, particularly at higher temperatures. To satisfy these tightened requirements, on the one hand, conventional power modules, i.e., direct bonded Cu (DBC)-based systems with bond wire contacts, have been further improved. On the other hand, alternative packaging techniques, e.g., chip embedding into printed circuit boards (PCBs) and power module packaging based on the selective laser melting (SLM) technique, have been developed, which might constitute an alternative to conventional power modules in certain applications.

As an important member of optical fiber sensor, fiber optic Extrinsic Fabry-Perot Interferometric (EFPI) sensor has prospects for a wide range of industrial applications due to its small size, compact configuration, good reliability and flexibility. In a white light based fiber optic EFPI sensor system, which has the advantages of large dynamic range and high resolution, spectral analysis equipment is the most important part which takes the major cost of the system. Therefore, multiplexing spectral analysis equipment to measure multiple sensors simultaneously is an effective and necessary way that can save the cost of the whole sensor system. In this paper, a scheme based on the frequency division multiplexing of EFPI optical fiber sensors is proposed. Two EFPI sensors with different gap lengths are parallely connected through the optical fiber coupler. The overlapped interference spectrum of the two EFPI sensors is measured by using an optical spectrum analyzer, which is separated into two individual interference spectrums with a Finite Impuse Response (FIR) band-pass filter. Their envelope components are extracted with Hilbert transform, and then the interference spectrums are normalized by the envelope components. The respective gap lengths of the two EFPI sensors are achieved with the cross correlation calculation. Using this frequency division spectral analysis method, a two-channel multiplexing EFPI sensor system is implemented in the laboratory. The deployment of this frequency division multiplexing technology can greatly reduce the cost of the whole system which has extensive potential applications for distributed fiber optic EFPI sensor system.

A solid oxide fuel cell (SOFC) is an electrochemical device that converts chemical energy of a fuel (hydrogen) directly into electrical energy. The chemical energy from hydrogen and an oxidant (oxygen) is converted without combustion to the electrical energy. The hydrogen fuel is supplied to the anode while oxygen enters through the cathode into the fuel cell. With the use of a catalyst the hydrogen atom separates into a proton and an electron and both of these take different routes through the system into the cathode.<br><br> SOFCs are an important strand of future hydrogen/ electrical energy provision. They offer high efficiency, compactness and little pollution. However, their necessary high operating temperatures place severe demands on the component materials. To maximise efficiency, SOFCs operate at temperatures as high as 1000&#176;C but since a metallic (e.g. nickel) anode and a ceramic (e.g. yttria-stabilised zirconia &minus; YSZ) electrolyte have different coefficients of thermal expansion (CTE) values, this means that at the operating temperatures, the anode may peel away from the solid electrolyte. To release this thermal strain, adding YSZ (CTE - 10 &#215;10^&minus;6 K^&minus;1)^&#91;1&#93; to the metal produces a similar CTE to that of the electrolyte.<br><br> A cost-effective way of combining the metallic and ceramic parts of the anodes is the principal driving force of this paper and involves electroless plating of YSZ with nickel. The two components &minus; both in powdered form &minus; are then processed by either cold pressing or screen printing - followed by vacuum sintering. Their performance &minus; in terms of electrical conductivity, micro-structural uniformity and density will be presented and discussed.

We have designed an intensity-demodulated sensing system based on Fabry-Perot interferometer and fiber Bragg grating (FBG) for pressure measurement. The structure of the sensor probe is presented. It is an optical fiber extrinsic Fabry-Perot interferometer(EFPI) composed of silica tube and optical fibers. The variable quantity of cavity length of the EFPI is equal to that of silica tube, which has direct proportion to external pressure. The sensing system is interrogated by broadband light. In order to compensate intensity fluctuation, we use an FBG as a narrow band filter to obtain the sensing signal and reference signal from white-light interference fringe returned from EFPI. The sensing signal is in the reflected beam from FBG, and the reference signal is contained in reflected beam and transmitted beam of FBG simultaneously. Then two output light signals are transformed into current signals by two photodiodes. Subsequently two current signals are processed at the same time. After the signals being treated with circuit, the inherent disadvantage of intensity-demodulated sensor is removed. It is also to say the sensing system has immunity from the drift of light source power and fluctuation in fiber attenuation by using only a FBG. Meanwhile, the system has advantages of fast response, simple circuitry, strong ability of intensity compensation and low cost. Experimental results show that the experimental data are consistent with theoretical analysis. The dynamic range of sensor is from 0 to 500KPa, and the resolution reaches to 0.5KPa. The sensing system can be used to measure pressure in inflammable and explosive circumstance such as oil height of super oil storage tanks.

In this paper we investigate the performance of a SCS-6/Ti-15-3 composite system, a carbon/SiC woven composite system, and an AS4/3501-6 composite system, subjected to long term mechanical fatigue, with an extrinsic Fabry-Perot interferometric (EFPI) fiber optic strain sensor. Both stiffness reduction and the degradation of thermal expansion coefficient (TEC) are monitored. The obtained results show that the EFPI sensor provides reliable data during long term fatigue loading up to 1 million cycles. The results suggest that the EFPI sensor is a viable means to monitor current and proposed characteristic damage metrics for various composite systems. We also monitor the TEC degradation during the thermal fatigue of celion G30-500/PMR-15 woven cross-ply composite system, and present a simple micromechanical model, that employs a shear lag approach, utilized to predict the effect of matrix cracking on the TEC of the composite. Results show that good agreement between experimental data and theoretical results is obtained, and that this parameter changed by as much as 80% over the fatigue life of the composite.

To develop an Sn-Zn-xAg lead free solder alloy with optimal thermo-physical properties, this study is conducted to experimentally investigate the effects of silver content (0–3.5%) on the coefficient of thermal expansion (CTE) and melting range of this series of alloys.The CTE of Sn-Zn-xAg solder alloys is measured by using a dilatometer with a heating rate of 5 °C/min from 40 °C to 120 °C. Melting range is measured by using a differential scanning calorimetry (DSC) with heating rates of 5 °C/min and 0.5 °C/min.The results of dilatometer measurement show that for all the designed solder alloys, the CTE is increased with increasing temperature. When the temperature reaches 90 °C, the increase becomes less obvious. Furthermore, CTE increases linearly with increasing silver content. As the silver contents are over 2%, the values of CIE are greater than the conventional Sn-37Pb alloy, which may generate substantial thermal stress due to the difference in CTE between solder alloy and substrate. From the results of DSC measurement, the starting pint of the melting range is not substantially affected by the increased silver contents in the silver range under consideration. However, when the silver content exceeds 2%, a second peak can be observed from the heating curve, which results in a substantial increase in the end point of the melting range. These results are attributed to the appearance of Zn-Ag compounds, which can be observed in the microstructures. Based on the above observations, silver content should not exceed a maximum of 2% in order to develop an Sn-Zn-xAg lead free solder with proper thermo-physical properties.

The manufacturing of heterostructures is interesting in fields such as photonics(1), solar energy production(2) and quantum technologies(3). This paper, dedicated to germanium on silicon heterostructure manufacturing and stress engineering, builds up on Ref. (4) findings.We are using the differences in terms of coefficients of thermal expansion (CTE) between germanium and silicon, to induce a tensile stress in a thin germanium layer transferred by the Smart CutTM [1] technique onto a silicon substrate. In this approach, a bulk germanium wafer is directly bonded on a bulk silicon wafer, using surface activated bonding (SAB)(5,6). Process integration advantages are the low defect density of bulk germanium and the tensile stress that can be tuned using the bonding temperature.The adherence of SAB was high during bonding at relatively high temperatures (~250°C). Without any further heat treatment, the adherence was found to be 3500mJ/m2 by the double cantilever beam method (under prescribed displacement control and in an anhydrous atmosphere). This remarkable adherence prevented the Ge/Si heterostructure from sliding, debonding and cracking (7). The CTE difference could thus generate a large amount of tensile stress during the heterostructure cooling and splitting steps.First of all, using finite elements simulation, a model was designed to predict the bow and the in-plane internal stress after bonding and cooling of the heterostructure. Thanks to it, we could also evaluate those two values after layer transfer (splitting step). This numerical approach was more accurate than the former analytic method (Timoshenko), which did not include the non-linearity of CTE with temperature and for large displacements. Figure 1 shows the bow and the in-plane stress expected for a bonding at 250°C of, respectively, a Si/Si homostructure (Figure1.a) and a strained Ge/Si heterostructure (Figure1.b), when cooled down to room temperature. The former is flat while the bow of the latter is large indeed.Then, based on indications collected from simulations, we performed the bonding of a Si/Si homostructure in an EVG®ComBond® at 250°C. The same bonding conditions were used for an implanted germanium on silicon heterostructure. As shown in Figure 2, both bond pairs exhibited a bow close to that from FE simulations.After that, a splitting step was carried out, resulting in a thin germanium film on a silicon wafer (200mm), as shown in Figure 3. The film was transferred almost to the whole surface. The bow after splitting was of 10µm, a value not so far from the simulated value of 28.6 µm.As far as tensile stress was concerned, we used X-Ray Diffraction to gain access to the lattice parameter deformation and thus the tensile stress, 0.05% and 72 MPa, respectively (Figure 4). In comparison, FE simulation gives us 107 MPa of tensile stress after splitting. The main advantage of our approach is the lack of misfit dislocations in the Ge film, at variance with Ge epitaxy on Si (with a threading dislocations density typically around 107 cm-2, then).The presentation will focus, first, on the simulation tool and the manufacturing process used to fabricate such stressed germanium films. Then, stress calculus will be detailed. Finally, TEM imaging of cross-sections, XRD and bow measurements will help us better understand the specificities of such thin Ge films transferred on Si bulk wafers. Higurashi E. Heterogeneous integration based on low-temperature bonding for advanced optoelectronic devices. Jpn J Appl Phys. 1 avr 2018;57(4S):04FA02.King RR, Law DC, Edmondson KM, Fetzer CM, Kinsey GS, Yoon H, et al. 40% efficient metamorphic GaInP∕GaInAs∕Ge multijunction solar cells. Appl Phys Lett. 30 avr 2007;90(18):183516.Scappucci G, Kloeffel C, Zwanenburg FA, Loss D, Myronov M, Zhang JJ, et al. The germanium quantum information route. Nat Rev Mater. oct 2021;6(10):926-43.Abadie K, Fournel F, Morales C, Vignoud L, Colona JP, Widiez J. Manufacturing of Optimized Ge Substrates Using a Covalent Bonding Process. ECS Meet Abstr. 23 nov 2020;MA2020-02(22):1623.Takagi H, Kikuchi K, Maeda R, Chung TR, Suga T. Surface activated bonding of silicon wafers at room temperature. Appl Phys Lett. 15 avr 1996;68(16):2222-4.Rebhan B, Vanpaemel J, Dragoi V. 200 mm Ge Wafer Production for Oxide-Free Si-Ge Direct Wafer Bonding. ECS Trans. 8 sept 2020;98(4):87-100.Chao YL, Tong QY, Gösele UM. Thermomechanical stress in silicon on quartz wafer bonding and Smart Cut® process. MRS Proc. 2001;681:I5.10. [1] Trademark from S.O.I.T.E.C. .S.A. Figure 1

Large-amplitude vibrations of rectangular plates subjected to harmonic excitation and thermal loads are investigated. The von Ka´rma´n nonlinear strain-displacement relationships are used to describe the geometric nonlinearity and the effect of thermal loads are included. Calculations are performed for a AISI 304 stainless-steel thin plate which has been tested experimentally. The plate is fixed to a AISI 410 stainless-steel frame which has a different coefficient of thermal expansion. Both calculations and experiments show a very large effect of temperature changes of the order of one degree Celsius on the nonlinear results.

Characteristics have been analyzed to understand the motion and the response of the microelectromechanical pressure transducers fabricated by the so-called LIGA process. The metal bridge for the overpressure protection of the diaphragm was built on the silicon substrate. The difference in thermal expansion coefficients between the metal and the silicon causes the crucial distortion of the differential transducers when temperature changes occur. A thermal expansion analysis has been made for temperature changes to provide the basis for credible designs. Thermal stresses, displacements and capacitance were calculated by the commercial finite-element code ANSYS. Interface shear stress between the substrate and the overpressure stop due to temperature changes increases with stop thickness, but eventually a small reduction in the peak occurs. The gap-bulging for the thin metal stop results from the bending at the interface.