光机衍射方程在金属材料应变测量中的应用

目前,利用正交光栅作为应变传感器来测量金属材料的应变引起了人们的兴趣,本文将光栅衍射方程推广应用到金属材料应变测量中,借助ＬＣＣＤ等硬件测试系统及相应的数据采集与处理系统,帝时、准确测量了金属材料的应变。     

用粘贴表面光栅法计算和测试金属材料应变

目前,利用光栅作为应变传感器测量材料应变引起了研究人员的兴趣。本文分析了衍射光栅法的基本测量原理,建立了一套相应的实验测试装置。该装置由光源、测试台、CCD、计算机数据采集与处理等部分构成。利用该装置进行了不同载荷下单向拉伸平板中心圆孔附近应力应变分布的实验,结果令人满意。由于借助CCD和计算机进行数据采集与处理,可实现金属材料应变的近实时显示与测量。     

动态匹配光栅解调传感系统温度补偿研究

采用一对辅助匹配光纤光栅,结合基于MAX1968EUI芯片闭环自动控制,设计了一种半导体小型温度控制系统.通过控制传感光栅反射峰值变化,使匹配光栅温度变化与传感光栅周围环境温度变化相匹配,实现了动态匹配光栅解调方案的应变测量系统温度补偿,消除了光纤光栅传感器温度、应变交叉敏感效应对传感系统测量应变的影响.解调系统同时采用一支微测力传感器作为解调系统的输出,消除了传统动态匹配光栅解调系统中压电陶瓷磁滞效应对测量结果的影响.实验结果表明,温度变化对系统应变测量影响误差小于2％,传感系统的线性优于0.999 5.     

液氮温区下光纤布拉格光栅应变传感器测量性能的研究

基于光纤布拉格光栅传感器的原理,研究了在液氮浸泡情况下光纤布拉格光栅应变传感器的静态传输特性.实验过程中利用悬臂梁原理和美国Micron Optics公司生产的光栅波长可调谐激光扫描法解调系统,分别测量了液氮浸泡中的悬臂梁的正应变和负应变,确定了在液氮温度下悬臂梁应变与光纤光栅波长偏移量之间的关系.为测量高温超导磁体的应变提供了新的方法.     

埋入式光纤光栅应变测量系统的设计

埋入式光纤光栅应变传感器作为大型土木结构健康监测的智能元件具有很好的发展前景。讨论了埋入式光纤光栅应变传感器的传感机理，设计了埋入式光纤光栅应变测量系统。从力学角度阐述了光栅传感探头的结构和制作工艺。采用可调谐F-P滤波器对光栅信号进行解调，解决了应变与温度交叉敏感问题。系统对应变的测量范围为0～1500με。通过理论分析证实了系统方案的可行性。     

具有温度补偿功能的光纤光栅传感解调系统

从理论和实验上研究了三角形光纤布拉格光栅的温度特性,结果表明：三角形光纤布拉格光栅谐振波长的温度变化率与普通光纤光栅的相同,并且其光谱形状不随温度的变化而改变。利用三角形光纤光栅光谱的这一温度特性,设计了一种具有温度补偿功能的应变传感解调系统。该系统利用斜线光纤光栅将光纤光栅应变传感的波长编码信息转换为强度,并且用信号强度与参考光强度的比值作为应变的度量值。研究表明,应变与应变度量值成线性关系,同时系统具有温度补偿功能。在三种不同的温度条件下,对悬臂梁的应变测试结果显示：在实验测量范围内,温度变化1℃导致的应变测量误差小于6微应变。由于采用信号强度和参考光强度的比值作为应变的度量值,避免了宽带光源的平坦度及波动对测量结果的影响。     

啁啾光栅结合边缘线性滤波解调的 FBG应变测量系统

介绍一种采用啁啾光栅并结合边缘线性滤波解调的FBG应变测量系统。系统中探头以2个光纤布喇格光栅(FBG)的波长差作为传感信息测量等强度悬臂梁的应变，避免了测量过程中温度变化因素对测量结果的影响，并且提高了灵敏度和分辨率。采用啁啾光栅结合长周期光纤光栅边缘线性滤波技术的波长解调方案，理论上证明了该系统的可行性，系统测量范围为0～500με，在海上开采平台、高层建筑、大型基础构件、桥梁大坝等结构的健康监测中具有一定意义。     

用激光加工硅钢片降低铁损残余变形的云纹干涉法测量研究

应用双镀层高温高频光栅和云纹干涉法对激光加工硅钢片降低铁损的残余变形进行了测量研究。分别对采用ＣＯ２连续激光和ＹＡＧ脉冲激光不同参数处理后硅钢片表面的残余变形进行了测量，对双镀层Ｃｒ－Ｃｒ光栅的制作方法、云纹干涉法测量残余变形的原理进行了讨论。实验结果表明，硅钢片在激光加工后，试件表面产生负性残余应变是细化磁畴，降低铁损的直接原因     

测量光纤有效弹光系数的一种新方法

针对目前许多新型光纤有效弹光系数测量的需要,报导了用光纤布喇格光栅(FBG)传感器测量光纤有效弹光系数的新方法。用一个温度参考光栅、一个测量光栅和一已知膨胀系数的材料,结合光纤布喇格光栅的特有性质进行了测量。建立了实验系统,实验结果表明,系统可以有效地解决温度与应变对光栅存在交叉敏感的问题,成功地测出了光纤有效弹光系数,测量误差小于1.3%。     

透射光栅测量的解谱方法

对透射光栅谱仪配Ｘ射线ＣＣＤ的软Ｘ射线谱测量系统ＴＧ－ＸＣＣＤ进行了简要描述,提出了正交函数展开法用于透射光栅谱仪配Ｘ射线ＣＣＤ测量的谱回推。将正交展开法用于激光打击金盘靶的软Ｘ射线谱回推,并与迭代法的解谱结果进行了比较。结果基本一致,不对此测量系统进行了误差分析。     

Softening caused by profuse shear banding in a bulk metallic glass

By controlling the specimen aspect ratio and strain rate, compressive strains as high as 80% were obtained in an otherwise brittle metallic glass. Physical and mechanical properties were measured after deformation, and a systematic strain-induced softening was observed which contrasts sharply with the hardening typically observed in crystalline metals. If the deformed glass is treated as a composite of hard amorphous grains surrounded by soft shear-band boundaries, analogous to nanocrystalline materials that exhibit inverse Hall-Petch behavior, the correct functional form for the dependence of hardness on shear-band spacing is obtained. Deformation-induced softening leads naturally to shear localization and brittle fracture.     

金属玻璃的热塑性成型

金属玻璃在其过冷液相区内表现出随着温度升高黏度逐渐降低的特性,因此可以对其进行热塑性加工.该性质颠覆了传统金属的加工成型方式,使得其在远低于传统金属材料加工的温度和应力作用下可以按照人们的要求进行成型.因此,一些具有低玻璃转变温度的金属玻璃又被称作金属塑料.另外,由于金属玻璃是一种无序结构材料,不存在位错、晶界等晶体缺陷,且热膨胀系数小,在热塑性成型中具有优异的尺寸精度,因此被认为是理想的微成型材料,有广阔的应用前景.本文系统介绍了金属玻璃的热塑性成型性质及其应用,从热塑性成型的基本概念出发,阐述了金属玻璃热塑性成型能力的评估指标、热塑性成型技术、热塑性微成型及其理论、热塑性微成型的应用等,对认识金属玻璃的热塑性及扩展其应用有重要的意义.     

A Review of Research Trends in Microwave Processing of Metal-Based Materials and Opportunities in Microwave Metal Casting

Microwave processing of materials has emerged as a new method for processing of a variety of materials in the recent years. Microwaves have been used effectively with significant advantages, particularly in food processing and chemical synthesis. They are also found to be efficient for processing polymers, ceramics, polymeric composites, and ceramic composites. The physics of interaction of microwaves with characteristically different materials is not yet explored well; consequently, there are challenges in microwave processing of metal-based materials. Industrial processing of bulk metal is yet to be popular in spite of the fact that the feasibility of metal powder sintering was demonstrated a few decades ago. This article provides a summary of fundamental aspects of microwave processing of metal-based materials and their interaction with metallic materials. The processing challenges have been surveyed; developments in terms of techniques and tooling have been analyzed. Possible effects of microwave processing on metallic materials, in particular metal powders, bulk metals, bulk metal-metal powder systems, and sheet metals have been presented. Future research aspects of microwave processing of metallic materials with reference to metal casting have been identified.     

Wave polarization and left-handed materials in metallic magnetic composites

We theoretically investigate the existence of left-handed materials in metallic magnetic composites. We find that the composites behave as left-handed materials only when electromagnetic waves are right-hand circularly polarized under longitudinal magnetization or linearly polarized under transverse magnetization. The frequency range in which the metallic magnetic composites behave as left-handed materials depends on the wave polarization and characteristic parameters of the composites. Electric and magnetic dampings of the composites bring a reduction of the frequency band. Large damping may even destroy the existence of left-handed materials in metallic magnetic composites. PACS 73.50.Mx; 41.20.Jb; 42.25.Ja     

Highly energetic and flammable metallic glasses

Energetic materials are solids that release a large amount of energy in combustion. The evaluation depends on both combustion heat and ignition temperature. Conventional non-metallic materials have low ignition temperature but small combustion heat,whereas metals have large combustion heat but high ignition temperatures. We show that many metallic glasses, combining the merits of both metals and non-metals, have large combustion heat, approximately twice that of the non-metals, and low ignition temperature that is several hundreds of Kelvin lower than that of the metals. The ease in igniting metallic glass results from the low thermal conductivity of the materials and the storage of energy in their liquid-like atomic structure. Metallic glass ribbons outweigh metallic nanoparticles due to their high production efficiency, low cost and nontoxicity. The findings suggest that metallic glasses are alternative energetic materials.     

Model of bidirectional reflectance distribution function for metallic materials

Based on the three-component assumption that the reflection is divided into specular reflection,directional diffuse reflection,and ideal diffuse reflection,a bidirectional reflectance distribution function(BRDF) model of metallic materials is presented.Compared with the two-component assumption that the reflection is composed of specular reflection and diffuse reflection,the three-component assumption divides the diffuse reflection into directional diffuse and ideal diffuse reflection.This model effectively resolves the problem that constant diffuse reflection leads to considerable error for metallic materials.Simulation and measurement results validate that this three-component BRDF model can improve the modeling accuracy significantly and describe the reflection properties in the hemisphere space precisely for the metallic materials.     

基于X射线光子计数探测技术的材料K-edge特性识别实验研究

X射线光子计数探测器是多能谱CT成像技术的核心,其通过能量阈值可以选择记录不同能量的X射线光子,有助于分析不同材质的物理特性。利用搭建的基于光子计数探测器的多能谱CT系统,开展高纯度金属材料K-edge特性识别实验研究。通过设置探测器的不同能量阈值,在不同能量范围获取金属材料投影图像,利用投影图像灰度信息分析不同能量X射线的衰减特性,以识别金属材料K-edge特性。最终实验结果表明,基于光子计数探测器的X射线能谱CT系统,能够识别金属材料与特定能量X射线光子发生相互作用所表现出的K-edge特性。通过计算K-edge特征峰能量阈值与材料K-edge理论能量值之间的线性对应关系,对光子计数探测器的能量阈值进行了标定。     

不同厚度衬底上矩形孔金属结构的太赫兹透射特性数值分析

利用时域有限差分法对不同材料和厚度衬底上矩形孔金属结构太赫兹（THz）波的透射特性进行了数值分析。研究表明：矩形孔金属阵列对THz光谱具有频率选择特性,这为太赫兹滤波功能器件的开发提供了基础。在实际应用中,这种金属微结构常常需要制备在某种衬底上,而衬底材料及厚度无疑会对其太赫兹透射特性带来影响。研究了不同衬底材料和衬底厚度的矩形孔金属结构太赫兹透射性质,通过数值模拟研究发现,对于同一种衬底材料,随着衬底厚度的增加,矩形孔金属结构的透射峰峰位向低频移动。比较高阻硅和聚四氟乙烯两种衬底材料发现,高介电常数的硅衬底引起的透射峰移动更为明显。