光纤光栅传感器金属化保护及钎焊嵌入42CrMo钢

针对光纤光栅传感器保护方面及向金属中封装嵌入方面现存的问题,采用化学镀和电镀结合的方法对光纤光栅传感器进行镀镍金属化保护,随后用钎焊的方法将传感器嵌入42CrMo结构钢中,从而获得智能金属结构.结果表明,镀层与传感器结合界面无缺陷,镀镍金属化使光纤获得了良好的保护,为后续钎焊嵌入金属做好了准备;钎焊对传感器影响较小;对钎焊后获得的智能结构进行了温度监测,表明传感器的灵敏度提高1倍,温度与波长变化成线性关系.     

FBG超声波焊接封装及其弯曲传感特性

为获得金属层片封装的光纤布拉格光栅（FBG）片状传感头,预先对裸光栅表面化学镀加电镀镍,然后对金属化FBG进行超声波焊6061铝合金薄片封装.采用拉伸试验测试超声波焊接结合强度和金属化FBG的嵌入强度,文中还研究了FBG的光谱特性、温度传感特性和三点弯曲应变传感特性.结果表明,当焊接压力为5.4 MPa,焊接时间为45 ms,镀层厚度为45 μm时,焊接封装效果较好;超声波焊接封装后铝箔的平均撕裂强度可达58.96 N,金属化FBG嵌入铝箔的拉断力可达8.89 N;封装后的FBG仍保持了良好的波形,平均温度灵敏度系数为29.07 pm/℃,平均三点弯曲应变灵敏度系数为0.096 7 pm/με.     

工艺参数对氮化铝陶瓷表面激光金属化层电阻的影响

目的 提高氮化铝陶瓷表面激光金属化层的导电性能。方法 采用正交试验设计方案,使用30 W纳秒光纤激光打标机制备了氮化铝陶瓷表面激光金属化试样,测量了金属层的电阻。通过极差分析和方差分析方法分析了激光工艺参数及其交互作用对氮化铝陶瓷表面激光金属化层电阻值的影响规律。结果 在本研究激光工艺参数及其取值范围内,激光功率对氮化铝表面激光金属化层电阻的影响最为显著,增大激光功率有利于降低氮化铝表面激光金属化层的电阻值。采用优化工艺参数(激光功率30 W、频率30 kHz、扫描速度100mm/s)单次激光扫描制备激光金属化层的电阻为2.25?/mm。随着重复扫描次数的增加,功率不同的激光表面金属层的电阻值向相反方向转变：小功率激光表面金属层电阻值随扫描次数增加而迅速减小,大功率激光表面金属层电阻值随扫描次数增加而增大。经10次重复扫描后,激光功率3 W(相应的激光能量密度约为15.3 J/cm²)激光金属化层的电阻值低于功率分别为30 W和18.75 W激光金属化层的电阻值。结论 采用30 W激光单次扫描,或者采用3 W激光多次扫描,有利于提高氮化铝表面激光金属化层的导电性。     

6061铝合金光纤激光填丝焊工艺与性能研究

采用光纤激光填丝焊工艺对6061铝合金进行焊接,研究了激光功率、焊接速度和送丝速度对铝合金激光焊接接头质量和热输入对接头拉伸性能的影响。结果表明,6061铝合金激光填丝最佳焊接工艺为激光功率2 k W、焊接速度3 m/min、送丝速度1.5~3.0 m/min。激光焊接接头抗拉强度随热输入增加而降低,热输入由80 J/mm增加到146J/mm,抗拉强度由218 MPa降低到206 MPa。     

基于大功率光纤激光器的不锈钢焊接工艺的优化

为了研究不锈钢激光焊接力学性能并提高焊接效率,采用2 k W光纤激光器的数控焊接系统,探讨了不同速度下光纤激光器焊接304不锈钢的深宽比变化情况,并以3 mm厚的SUS 304不锈钢薄板为研究对象,探讨了不同工艺参数(焊接速度和离焦量)下3 mm厚的SUS304不锈钢的焊接质量。结果表明,光纤激光器功率2 k W,离焦量-1 mm,焊接速度1.2 m/min,焊接保护气体氩气、流量30 L/min,成为焊接3 mm厚的SUS304不锈钢的最佳工艺参数,焊接接头抗拉强度约为母材的93%。     

镀镍金属化42CrMo钢的微观组织与传感特性研究

采用化学镀镍和电镀镍相结合的方法,对光纤光栅传感器进行保护,然后用钎焊方式将传感器嵌入42Cr Mo钢基体中获得智能金属结构,对其微观组织和传感特性进行研究。结果表明,智能金属结构的灵敏度大大提高,比光纤光栅的灵敏度高1倍。     

机载传感器薄壁零件焊缝失效分析及改进

现代航空发动机控制系统对传感器的可靠性要求日益提高,焊接作为传感器生产制造过程中质量风险较高的一个环节,对传感器的可靠性有重大影响,而目前主要依赖焊接工艺参数控制来保证焊接质量。本文通过对某型航空发动机用温度传感器薄壁零件焊缝的失效分析,提出了将焊接方式由脉冲激光焊改为连续激光焊的设想,并采用优化的连续激光焊焊接工艺参数,获得了连续、稳定、无烧穿的良好焊缝。同时,通过可靠性强化试验对比验证了2种焊接方式下传感器的抗振性能,试验结果表明:相同焊接熔深下,连续激光焊的焊缝抗振性能明显优于脉冲激光焊的焊缝,能够有效提高传感器在高量级振动环境下的抗疲劳性能。     

Al2O3陶瓷Ti+Nb/Mo金属化对其与Kovar合金钎焊连接的组织和力学性能的影响

采用磁控溅射在Al₂O₃陶瓷表面沉积了Ti+Nb/Mo金属层,实现了氧化铝陶瓷的金属化,并通过电镀镍提高了金属化效果.采用AgCu28钎料,实现了金属化Al₂O₃陶瓷与Kovar合金的可靠连接.通过扫描电子显微镜和能谱观察了钎缝的微观组织.结果表明,钎料与母材发生了明显的界面反应.Cu元素扩散进入Kovar合金,同时Ni元素扩散进入钎料的富铜区,从而促进AgCu/Kovar连接界面的形成;金属化层在Al₂O₃/AgCu钎料界面处,起到了关键作用,其中铌可以抑制脆性化合物形成,缓解残余应力.金属化层镀镍后,钎缝中AgCu共晶区明显,且钎缝较宽,对提高镀镍试样的钎焊接头强度有一定作用.     

钎焊及其设备

预合金粉在金刚石工具烧结中的钎焊作用;陶瓷金属钎焊接头优化与残余应力数值模拟;光纤光栅传感器金属化保护及钎焊嵌入45CrMo钢;钛基非晶态钎料钎焊高强石墨与铜的界面特征;工艺参数对AZ31镁合金搅拌摩擦加工微观组织的影响;     

钎焊及其设备

预合金粉在金刚石工具烧结中的钎焊作用;陶瓷金属钎焊接头优化与残余应力数值模拟;光纤光栅传感器金属化保护及钎焊嵌入45CrMo钢;钛基非晶态钎料钎焊高强石墨与铜的界面特征;工艺参数对AZ31镁合金搅拌摩擦加工微观组织的影响;     

Fe–C-coated fibre Bragg grating sensor for steel corrosion monitoring

A steel corrosion sensor based on fibre Bragg gratings (FBGs) has been developed and tested in this paper. The steel corrosion sensor has been formed by electroplating a Fe–C film on a metallized FBG. The coated FBG sensors have been tested in cabinets in which the availability of chloride ions and oxygen are controlled. The microstructural changes have been investigated by optical microscopy and SEM imaging. The FBG spectra are collected by a spectrometer. The results show that the spectra change, the wavelength shift, and the occurrence of multiple peaks are related to the corrosion degree of the Fe–C film.     

Monitoring of corrosion in reinforced concrete structure using Bragg grating sensing

Corrosion in reinforced concrete structures is a major problem that seriously affects the service life of the structures. In order to detect rebar corrosion, a fiber optic corrosion sensor (FOCS) made of one fiber Bragg grating (FBG) sensor and twin steel rebar elements was designed and packaged up with concrete. Subsequently, a series of experiments were carried out to verify its feasibility. A constant current accelerated corrosion test was performed on five fiber optic corrosion sensors and the relationship between reflected wavelength change from the grating and the weight loss rate of rebar was obtained by the gravimetric weight loss method. The experiment shows that it is feasible to monitor the degree of corrosion of reinforced steel in reinforced concrete structures using FOCS.     

Fiber Bragg grating sensors for on-line welding diagnostics

On-line monitoring of an arc-welding process is performed in this paper by means of fiber Bragg grating transducers (FBGs) in two different configurations. FBGs were glued to the plate surfaces next to the weld joint, and a FBG transducer was designed to sense the perturbations in the air surrounding the welding plasma column. Sensitivity to both temperature and vibrations during the process was analyzed during several tungsten inert gas (TIG) welding tests, showing the feasibility of the proposed design to perform an on-line detection of different welding perturbations. To enhance the analysis, a setup based on plasma optical spectroscopy was also employed to allow a comparison among the response of both techniques to the appearance of these perturbations.     

The signal characteristics of reflected spectra of fiber Bragg grating sensors with strain gradients and grating lengths

Among the numerous types of fiber optic sensors, FBG sensors are currently the most actively studied sensors due to their good multiplexing capabilities. The demodulation method of FBG sensors is based on detecting the wavelength shift of their sensor peaks. Properties such as strain, temperature, etc. can be measured simply by detecting them. However, the signal stability of FBG sensors can be influenced by strain gradients induced by structural geometry or cracks on the surface when FBG sensors are embedded into or attached on the structure. In this study, the signal characteristics of reflected spectra of FBG sensors were verified under strain gradients and the correlation between the grating length of FBG sensors and strain gradients were investigated quantitatively. From the experimental results, the optimum working range of the FBG sensors, where FBG sensors could be used without split of the sensor peak, was shown when they were under strain gradients.     

Impact wave and damage detections using a strain-free fiber Bragg grating ultrasonic receiver

A strain-free mobile fiber Bragg grating (FBG) ultrasonic receiver is applied for the impact-related experiments of carbon fiber reinforced plastic laminates. The strain-free FBG sensor detects an impact-induced acousto-ultrasonic wave and its responses are compared with those of a piezoelectric sensor. Ultrasonic mode wavelength-related averaging effect in FBG ultrasonic sensors is also reported. The mobile FBG sensor can be useful for the acoustic characterization and the sensor placement optimization being required before construction of a built-in FBG network. Finally, the mobility of the strain-free FBG sensor head is extended to ultrasonic scanning application. Based on its high scanning spatial resolution, impact damage sizing is conducted more precisely.     

基于光纤Bragg光栅传感器的铝合金堆焊应力测试

大型结构件的焊接应力应变测试一直是研究的热点和难点.针对目前大型结构件焊接应力应变在线实时监测手段存在不耐高温和测试精度不高等问题,提出了一种基于光纤Bragg光栅(FBG)传感器的焊接应力应变在线实时监测方法.采用该方法构建了基于FBG传感器的焊接应力应变在线监测系统原理,并对LD10铝合金板材进行了TIG堆焊的温度...     

类岩石材料破裂声发射的光纤光栅传感监测技术

针对岩石破裂声发射检测中的常规检测仪器抗电磁干扰差、灵敏度低、可靠性差等不足,提出采用光纤光栅传感技术来实现声发射检测,分析了光纤光栅传感检测应变和声发射的机理,组建了相应的声发射检测模拟实验系统,给出了模拟实验的500kHz激励声信号和光纤光栅传感响应信号。利用软件RFPA进行了岩石破裂的数值模拟,选择水泥河砂作为主要原料的砂浆材料,制作了类岩石材料实验试件,并在单轴数控压力机上进行了岩石试件加载破裂声发射实验,用光纤光栅传感器来探测和记录声发射能量及声发射累计次数,证明该传感器能实现声发射检测。     

Non-destructive evaluation of smart materials by using extrinsic Fabry–Perot interferometric and fiber Bragg grating sensors

The real-time non-destructive evaluation (NDE) technologies of engineering structures are very important to assess the performance of in-service structures. It is very difficult to carry out the on-line structural integrity monitoring by using classical NDE methods. Fiber optic sensors in smart structures provide a unique opportunity to real-time monitor the structural health status by using embedded sensors. This paper examines the possibility of extrinsic Fabry–Perot interferometric (EFPI) and fiber Bragg grating (FBG) sensors for NDE of composite and aluminum structures. The experiments of 3-point bending measurement of composite laminates and aluminum plates with and without damages by using the EFPI and FBG sensors are performed, respectively. The experimental results show that the flexural strain of damaged structures is much higher when compared with relevant undamaged structures under same bending load by using both EFPI and FBG sensors. Furthermore, an excellent accordance was found between the results of the 3-point bending tests by using surface-mounted EFPI and FBG sensors