温度和磁场对应变片的影响

电阻应变片的电阻不但随应变变化,而且随温度和磁场变化.为了修正温度和磁场的影响,在4.25K到300K的温度范围内,试验了镍铬合金电阻应变片WK-15-250BG-350的表观应变与温度的关系,并在不同磁场下试验了温度对应变片的影响.在低温下试验了应变片的表观应变与磁场的关系(即磁阻效应).分析了不同温度下,磁场对应变片的影响.试验结果将在TESPE装置的实际应变测量中进行误差修正.     

陶瓷压强传感器桥路的温度特性测试

陶瓷压强传感器的输出不仅与外加的压强有关,还与传感器本身的温度有关.温度使惠斯通电桥的桥臂电阻发生变化,由于桥臂电阻与陶瓷片烧结粘合在一起,当陶瓷片受压形变时产生电阻的应变,造成电桥输出电压的变化;当烧结粘合在一起的桥臂电阻和陶瓷片随本身的温度发生变化也会使电桥输出电压发生变化.本文对实验进行了定量地测量,得出了温度对电桥输出电压的影响,建立了修正的数学模型.     

国产金属箔式应变片在低温和强磁场下工作特性的研究

HT- 7U超导模型线圈实验中 ,研究了国产金属箔式应变片在低温和强磁场下的工作特性 ;测量了应变片从室温液氮温度液氦温度的输出示应变曲线 ,以及磁场强度从 0 T- 4T时应变片的输出示应变曲线。实验测得 ,对所选用的应变片 ,从室温降至液氮温度 (77.4K)的热输出为 - 3 6 4 7με,降至液氦温度 (4.2 K)的热输出为 - 3 999με,磁场从 0 T升至 4T的输出示应变为2 3 5με。     

CFETR CS模型线圈的电磁分析

在中国聚变工程试验堆(CFETR)的概念设计阶段,为了将来正确设计和顺利加工其中心螺线管(CS)线圈,设计了一个由Nb₃Sn内线圈和NbTi外线圈组成的模型线圈。采用线电流模型和后期数据处理的方法对其磁场做了精确计算,解决了线电流模型不能计算导线内部磁场的问题。在此基础上计算了线圈的电感和电磁应力等参数。     

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在中国聚变工程试验堆(CFETR)的概念设计阶段,为了将来正确设计和顺利加工其中心螺线管(CS)线圈,设计了一个由Nb3Sn内线圈和NbTi外线圈组成的模型线圈。采用线电流模型和后期数据处理的方法对其磁场做了精确计算,解决了线电流模型不能计算导线内部磁场的问题。在此基础上计算了线圈的电感和电磁应力等参数。     

CFETR中心螺管模型线圈电源主回路设计

针对CFETR中心螺管模型线圈低温通电实验要求,开展了模型线圈测试电源系统及主回路的初步研究。根据交流测试电流波形,设计了电源主回路的拓扑结构,满足线圈电压1k V、电流47.3k A的参数要求。针对电路结构中的几个关键部件,阐述了四象限变流器的设计及工作原理,计算了换流电阻的阻值大小,并基于绝热模型下线圈的热点温度分析,给出在热点温度T180K、绝缘电压V≤2.5k V条件下移能电阻的阻值选取范围。为后期模型线圈的实验运行和测试电源系统的工程设计提供依据。     

HT-7U超导模型线圈电阻应变测量

针对 HT- 7U超导模型线圈实验中应变测量的特点 ,介绍了低温强磁场特殊条件下电阻应变测量方法 ,从测量电路、应变片粘贴布置方案、应变计算公式、测量结果等方面进行了具体分析。     

CFETR CS模型线圈导体铠甲低温力学性能研究

CFETR CS模型线圈采用超临界氦迫流冷却,超临界氦在导体内部流动时吸收电缆上的热负荷,使得线圈能够保持在低温下安全运行。CFETR CS模型线圈的超导体采用CICC结构,其导体外部铠甲采用氩弧焊填丝焊接连接而成。在线圈运行过程中,导体遭受的巨大电磁载荷主要依靠不锈钢铠甲承受。采用数值模拟与实验研究相结合的方法,研究了导体铠甲在磁体运行过程中的受力情况,并通过常低温拉伸实验,获得了铠甲母材与焊缝4. 2 K力学性能测试。实验结果表明,导体铠甲母材与焊缝试样机械性能,均能满足CFETR CS模型线圈超导体设计要求。     

惠斯通电桥实验中桥臂电阻的确定

惠斯通电桥的灵敏度是影响其测量精度的关键因素。对电压法和电流法惠斯通电桥测电阻实验进行了理论探讨和实验验证,发现电桥灵敏度与桥臂电阻密切相关。提出最佳桥臂电阻的计算公式,为惠斯通电桥的精确测量提供便利。     

用惠斯通电析测定杨氏模量

用惠斯通电桥测量金属丝在不同应力下的电阻应变，研究应力、应变及电阻变化率的关系．     

Analysis on strain transfer of a pasted FBG strain sensor

Optical fiber is not in direct contact with the material host in practice, so the strain measured by the Fiber-optic Bragg Grating (FBG) sensor is not the true strain. The transfer mechanism between the measured strain and the true strain depends on mechanical properties of fiber, protective layer, substrate, adhesive layer, and the material host. This paper analyzes the transfer mechanism of strain in detail, and proposes the shear stress distribution of polynomial form, and establishes the transfer function of strain. This paper also analyzes the influence on length of FBG sensor, adhesive layer thickness and elastic modulus on strain transfer coefficient in detail. The theoretical guidance for the practical application of the FBG sensor is given through the strain transfer analysis.     

Irradiation effect on strain sensitivity coefficient of strain sensing fiber Bragg gratings

The effect of irradiation on the strain sensitivity coefficient of strain sensing fiber Bragg gratings(FBGs) has been investigated through experiments. FBGs were fabricated in single mode fibers with 3 mol% Ge-concentration in the core and with a H2-loading treatment. In experiments, the FBGs were subjected to γ-radiation exposures using a Co60 source at a dose-rate of 25 Gy/min up to a total dose of 10.5 kGy. The GeO defect in fiber absorbs photons to form a GeE’ defect; the interaction with H2 is a probable reason for the γ-radiation sensitivity of gratings written in hydrogen loaded fibres. The effect mechanism of radiation on the strain sensitivity coefficient is similar to that of radiation on the temperature sensitivity coefficient. Radiation affects the effective index neff, which results in the change of the thermo-optic coefficient and the strain-optic coefficient. Irradiation can change the strain sensitivity coefficient of FBGs by 1.48%–2.71%, as well as changing the Bragg wavelength shift(BWS) by 22 pm–25 pm under a total dose of 10.5 kGy. Our research demonstrates that the effect of irradiation on the strain sensitivity coefficient of FBG is small and that strain sensing FBGs can work well in the radiation environment.     

生长方向对量子点应变与应变弛豫的影响

由于材料弹性的各向异性与表面能的各向异性, 不同的生长方向或生长面, 量子点有不同的力学性能与行为. 本文基于各向异性弹性理论的有限元方法, 以金字塔型自组织InAs/GaAs半导体量子点为研究对象, 分别在7个常见的生长方向或生长面上, 对其应变能和应变弛豫能、自由能等进行了分析计算, 得到了这些能量随生长方向的变化规律. 结果表明(211)量子点应变弛豫能最大, 而(100)量子点应变弛豫能最小. 这些结果可为可控制备量子点提供理论参考. 关键词： 量子点 生长方向 平衡形态 应变弛豫     

Dependence of nonrecovering plastic strain on the degree of macro-nonuniformity of strain distribution

The authors have investigated the effect of nonuniformity of distribution of plastic torsional strain (H_k) due to the method of application of the load on the nonrecovery of macro-shear observed in tubular test pieces subjected to alternating torsion [1–2].It has been established that with increase in H_k there is a regular increase in the values of the nonrecovery characteristics, the maximum nonrecovery rate and the total nonrecovering strain (g1) corresponding to this period. An analogous increase is observed in the relative elongation due to torsion and the corresponding reduced axial tensile stress (_k). A nonrecovery mechanism is proposed for alternating torsion.     

Experimental study of the Raman strain rosette based on the carbon nanotube strain sensor

This work presents a new technique named Raman strain rosette for the micro‐strain measurement of both Raman active and Raman inactive materials. The technique is based on the theoretical model of the carbon nanotube (CNT) strain sensor that applies the resonance and polarization Raman properties of CNTs and calculates the synthetic contributions of uniformly dispersed CNTs to the entire Raman spectrum. In our work, the proposed technique is applied in different experiments on the Raman inactive materials, such as step‐by‐step uniaxial tensile and Raman mapping around a circular hole. The experimental results reached by the Raman strain rosette are consistent with the actual values as a whole. This study verifies that the Raman strain rosette is applicable to quantitative measurement of all the in‐plane components of the strain tensor (including both normal and shear strains) by three polarized Raman detections for each sampling spot on a microscale. The technique is further applicable to achieving the strain fields through Raman mapping. Copyright © 2010 John Wiley & Sons, Ltd.     

基于激光技术的压痕应变花及测试应变的原理

介绍了一种用于测试面内三个应变分量的应变测量技术,在试件表面预先压制三个压痕,通过激光照射压痕,经衍射后干涉,产生干涉图。通过分析变形前后干涉斑点的光强值的变化来对待测位置进行应变测量。实验表明该方法对待测试件表面损伤小,且压痕应变花尺寸小,是一种新的光学应变测试技术,不仅可以用来进行普通应变测量,尤其对解决小空间应变测试问题有其独特的优点。     

宽温度范围SAW应变传感器温度与应变解耦研究*

针对宽温度范围应变测量的温度干扰问题,提出并研究了基于双谐振器的声表面波应变传感器。理论上,结合微扰理论、有限元方法、有效介电常数法分析出双谐振器频率与应变、温度的关系公式,进而推导出应变与温度关于这两组谐振器频率变化的表达式。实验上,搭建宽温度范围的实验平台,在Y+34?切向的石英基片上制作该传感器芯片,测得传感器芯片在30?C～180?C下的频率响应,将测得的谐振器频率代入表达式计算得到温度与应变值,与实验中参考温度与应变的值基本吻合。     

应力对硅烯上锂吸附的影响

本文采用基于密度泛函理论的第一性原理平面波赝势方法研究了双轴应力作用下锂原子吸附硅烯的结构及其稳定性. 计算结果表明,在拉应力和一定的压应力作用下,锂吸附的硅烯体系基本保持原有的结构. 而当更大的压应力作用时,硅烯产生了向锂原子方向凸起的结构变化,所得到的体系的总能也有明显地下降. 本文通过对各种应力下的硅烯声子谱的计算,分析了在压应力作用下锂吸附的硅烯结构不稳定的原因. 关键词： 硅烯 应力 第一性原理 声子谱