表面粘贴式光纤光栅传感器的应变传递机理分析与实验研究

金属基底封装的光纤光栅应变传感器具有线性度高、重复性好、易标定等特点,在应用中由于光纤与基体不直接接触,测量的精度取决于粘结胶的特性.在分析FBG应变感知机理的基础上,基于力学仿真设计了金属基底结构,并建立了包含光纤光栅-壳体-粘胶层-基体的四层应变传递仿真模型,制作并利用悬臂梁进行了应变测试,取得了良好的实验结果且与仿真计算误差在0.5%以内.     

光纤Bragg光栅传感器化学镀镍研究

在光纤智能金属结构材料中,为了使光纤传感器与基体金属有很好的结合性,同时对传感器进行保护,需要对光纤传感器表面进行金属化.本文研究了一种在光纤栅表面化学镀镍的方法和化学镀配方,取得了较好的实验效果.     

镀镍过程对光纤Bragg光栅中心波长及传感特性的影响

光纤Bragg光栅(FBG)作为传感及信息传输器件,嵌入到金属中可获得光纤智能材料或结构。为了对FBG进行适当的增敏和保护封装,本文以化学镀加电镀的方法实现了FBG的有效封装,讨论了金属化过程中FBG中心波长漂移情况及金属化前后FBG反射谱变化情况,并对金属化后的FBG在外界温度为30~80 ℃进行了温度传感试验。结果表明：FBG在电镀镍过程中受到粒子沉积压应力作用,其中心波长减小,且减小速率先快后慢;镀镍层厚度为1.3 mm和1.0 mm的FBG的温度灵敏度分别为19.11 pm/℃和18.4 pm/℃。     

光纤光栅金属化封装及传感特性试验研究

提出了一种光纤布拉格光栅的金属化封装工艺,并通过水浴法试验和等臂梁试验对其应变与温度传感特性进行了研究.结果表明,用金属化封装技术可以使光纤光栅传感器的温度敏感特性达到裸栅的2～3倍,达到23.357 pm/℃,应变特性有良好的重复性,线性拟合度达到0.999 9.     

夹持式封装低温敏FBG应变传感器的设计

设计了一种两端夹持式封装的低温敏FBG应变传感器.利用金属内、外管产生的膨胀差值引起的光栅波长变化量,与热膨胀和热光效应引起的光栅波长变化量抵消,实现温度补偿,金属内、外管隔及隔温套管与夹持支座内部均采用粘结剂连接后实现对光纤光栅的封装.标定试验表明:该传感器的温度灵敏度为0.78 pm/ ℃,是裸光纤光栅温度灵敏度的7.2%,大大降低了对温度的灵敏性,应变灵敏度系数为1.377 pm/ ℃.     

柔性基体材料封装FBG传感器的应变传递误差分析

由于力学理论和有限元仿真应用于道路结构的分析受材料参数与边界条件等因素影响较大,要获得其准确、真实的受力状态,需借助原位监测技术。然而,日益得到推广应用的高性能光纤光栅敏感元件因其传统的封装方式,无法在模量上匹配相对离散的道路结构测试。为此,本文以沥青路面结构为研究对象,提出了一种以纯沥青为光纤光栅外包层、以小粒径沥青混合料为封装层的柔性基体材料光纤光栅封装技术,建立了其变形作用机理的力学模型,从理论角度分析其应变传递机理,给出了相应的误差修正公式,并通过模型试验方式检验该传感器的感知性能及误差修正公式的适用性。研究结果表明：该种柔性原材料封装光纤传感器可用于沥青混合料的监测,且借助应变传递误差修正公式能较好地消除部分因素的影响,间接地保证了沥青路面结构真实变形的高精度还原,为路面结构监测技术的发展起到了积极的推进作用。     

环氧树脂掺金属粉末嵌入式FBG封装技术研究

针对光纤光栅(FBG)与被测金属构件可靠连接问题,提出环氧树脂掺金属粉末嵌入式封装技术,阐明了该封装工艺,采用纯弯曲梁对裸光纤光栅和封装后的光纤光栅分别进行应变实验,结果表明,经环氧树脂掺金属粉末封装后的光纤光栅传感器应变灵敏度是裸光纤光栅的1.3倍,达到1.53pm/με,具有很好的重复性,该方法提高了嵌入光纤光栅后被测金属构件的机械强度.     

胶粘剂对表贴式聚酰亚胺光纤布拉格光栅应变传递的影响分析

光纤布拉格光栅传感器用于测量结构的应变时,需与被测基体相粘黏,使其与基体协调变形,故胶粘剂的选取对其测量结果有直接的影响。针对此问题,本文对表面粘贴式应变传递模型进行了改进,建立了更为合理的模型,并通过理论分析出了影响应变传递率的主要因素,得到了其传递率随胶体剪切模量的增大而增大的结论。通过控制变量法,用480胶、AB胶、401胶、环氧树脂、3311胶这五种不同胶粘剂,将聚酰亚胺光纤光栅粘贴于等强度梁表面进行对比实验,得到了相应的应变传递率,其结果与理论模型计算值相比误差在5%左右,为表面粘贴式光纤光栅测量应变的工程应用提供了重要的参考。     

关于图例错误的更正

重庆大学刘浩,陈伟民,章鹏等人撰写的"基于正交试验的光纤传感器金属化连接工艺优化"一文已在本     

绝压传感器中陶瓷/钛合金焊接技术研究

高温绝对压力传感器需要形成耐高温的真空密封腔。对实现真空封装过程中陶瓷/钛合金焊接技术进行了研究,焊接过程中由于存在焊接应力,容易发生陶瓷碎裂情况,通过设计焊接尺寸、选择金属化材料、设计降温过程、试验设计工艺参数,实现了较高要求的真空封装,并对焊接后的试验件进行了试验分析,结果表明:焊接强度和密封腔体的漏率满足实际产品应用要求。     

BCB contact printing for patterned adhesive full-wafer bonded 0-level packages

Adhesive wafer bonding with a patterned polymer layer is increasingly attracting attention as cheap and simple 0-level packaging technology for microstructures, because the patterned polymer both fulfills the bonding function and determines the volumes between the two wafers housing the devices to be packaged. To be able to pattern a polymer, it has to be cross-linked to a certain degree which makes the material rigid and less adhesive for the bonding afterward. In this paper, a simple method is presented which combines the advantages of a patterned adhesive layer with the advantages of a liquid polymer phase before the bonding. The pattern in the adhesive layer is "inked" with viscous polymer by pressing the substrate toward an auxiliary wafer with a thin liquid polymer layer. Then, the substrate with the inked pattern is finally bonded to the top wafer. Benzocyclobuene (BCB) was used both for the patterned structures and as the "ink". Tensile bond strength tests were carried out on patterned adhesive bonded samples fabricated with and without this contact printing method. The bonding yield is significantly improved with the contact printing method, the fabrication procedure is more robust and the test results show that the bond strength is at least 2 times higher. An investigation of the samples' failure mechanisms revealed that the bond strength even exceeds the adhesion forces of the BCB to the substrate. Furthermore, the BCB contact printing method was successfully applied for 0-level glass-lid packaging done by full-wafer bonding with a patterned adhesive layer. Here, the encapsulating lids are separated after the bonding by dicing the top wafer independently of the bottom wafer.     

Investigation of strain transmission of surface-bonded FBGs used as strain sensors

Bonding an FBG on a substrate as a sensor using an adhesive, the strain transferred from the substrate through the bonding layer to FBG is smaller than that on the substrate. The strain transmission loss becomes large when the substrate is thin and/or made by a low-modulus material, e.g. the polyimide film used in lithium battery and chip on film manufacturing industry. Moreover, the FBG and the bonding layer affect the original strain distribution on the thin and low-modulus substrate. As a result, the substrate strain sensed by the FBG is underestimated and thus required to be corrected. Based on elasticity, an analytical model is proposed to characterize the strain transmission of an FBG used as a strain sensor when it is surface-bonded on a structure using an adhesive. The proposed strain transmission formula takes the influences caused by the stiffness of substrate and FBG as well as the bonding layer characteristics, i.e. the length, thickness and shear lag parameter into consideration. Validated respectively by numerical simulations using finite element method and experiments, this formula provides a simple but accurate correction for the bonded FBG to reflect the true structural strain.     

Adhesive bonding by SU-8 transfer for assembling microfluidic devices

SU-8 is largely used to make microfluidic molds or components, but mainly for producing high-precision and thermally stable structures. We present a versatile method that employs SU-8 as glue to perform an adhesive bonding between micro-patterned structures. More in general, this technique enables an easy assembly of microfluidic devices, which can also be made by different materials, where selective bonding is required. The adhesive bonding is achieved by transferring a thin layer of SU-8 5 (thickness ≤15?μm) on a substrate by means of a polyimide foil. The method is described in detail and an example of its application is given. Finally, a shear test is carried out to prove sufficient adhesion strength for microfluidic applications.     

Numerical investigation for SPR-based optical fiber sensor

In the present work, a theoretical analysis of a surface plasmon resonance (SPR)-based optical fiber sensor is carried out. For the SPR-based optical fiber sensor with four-layer mode (fiber core/metal/sensing layer/sample), the effect of the thickness of metal layer and sensing layer on the spectrum of the transmitted power and wavelength has been studied. Based on the propagation wavevector till the first order expansion of the dispersion function, a detailed explanation for the relationships between the resonance wavelength with the thickness of the metal layer and sensing layer is presented.     

光纤智能夹层制作工艺及试验研究

根据智能结构中光纤自诊断系统模块化要求,制作出光纤智能夹层.这种智能夹层不仅具有在光纤接头部位未出现断裂及智能夹层中光纤传感器未出现损坏的特点,而且具有光纤传感器的高灵敏度特性,可以铺设于复合材料表面或埋入复合材料内部.在此基础上,对智能夹层试件分别进行了轴向拉伸和四点弯曲试验.试验表明:在一定应变范围内,单膜交错光纤中光强-应变之间具有良好的线性关系,可以在埋入复合材料之前进行标定.利用智能夹层中光纤传感网络或自诊断模块,可以实现对智能结构的在线监测.     

Adhesive bonding with SU-8 in a vacuum for capacitive pressure sensors

This paper describes a method for fabricating capacitive pressure sensors through the use of adhesive bonding with SU-8 in a vacuum. The influence of different parameters on the bonding of structured wafers was investigated. It was found that pre-bake time, pumping time, and the thickness of the crosslink layer are the most important factors for successful bonding. Bonding quality was evaluated by inspection through the transparent glass of the sensor and through the use of an SEM photograph, with 90% of the area successfully bonded and an ultimate yield of 70% of the sensors. The measured bonding strength was 17.15 MPa and 19.6 MPa for wafers bonded in 80 °C and 100 °C, respectively. The pressure–capacitance characteristic test results show that this bonding process is a viable micro electro mechanical systems (MEMS) fabrication technology for cavity sealing in a vacuum.     

胶粘剂对MEMS压力传感器点焊压力测量的影响

针对点焊过程压力监测的MEMS压力传感器的粘贴问题,采用不同种类的胶粘剂粘贴MEMS压力传感器,在自制的压力测试平台上模拟点焊电极压力对传感器进行了加压测试。测试结果表明:采用α—氰基丙烯酸酯系胶粘剂粘贴的MEMS压力传感器输出结果优于环氧树脂系胶粘剂和酚醛树脂系胶粘剂粘贴的传感器的输出结果。造成不同胶粘剂粘贴传感器性能差别的主要原因在于胶粘层的弹性模量和厚度。     

A hybrid capacitive pressure and temperature sensor fabricated by adhesive bonding technique for harsh environment of kraft pulp digesters

We have developed a compensated capacitive pressure and temperature sensor for kraft pulp digesters (pH 13.5, temperatures 25–175°C reaching a local maximum of 180°C and pressures up to 2 MPa). The gauge capacitive pressure sensor was fabricated by bonding silicon and Pyrex chips using a high temperature, low viscosity UV (ultraviolent) adhesive as the gap-controlling layer and heat curing adhesive as the bonding agent. A simple chip bonding technique, involving insertion of the adhesive into the gap between two chips was developed. A platinum thin-film wire was patterned on top of a silicon chip to form a resistance temperature detector (RTD) with a nominal resistance of 1,500 Ω. A silicon dioxide layer and a thin layer of Parylene were deposited to passivate the pressure sensor diaphragm and the sensors were embedded into epoxy for protection against the caustic environment in kraft digesters. The sensors were tested up to 2 MPa and 170°C in an environment chamber. The maximum thermal error of ±1% (absolute value of ±20 kPa) full scale output (FSO) and an average sensitivity of 0.554 fF/kPa were measured. Parylene-coated silicon chips were tested for a full kraft pulping cycle with no signs of corrosion.