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81.
为了监测绕组变压器的静态应力场和发生短路等故障时的动态应力变化,设计了一种用于电气设备状态监测的新式FBG传感器。该传感器由聚醚醚酮材料封装的FBG构成,通过内部圆锥形空腔结构实现将轴向应力集中于FBG敏感位置。通过仿真对不同压力强度下传感器结构的应力场部分及形变趋势进行了计算与分析,论证了设计的合理性。实验分别对静态载荷和动态冲击进行测试,结果显示,在静态压载测试中,当100 N相似文献
82.
Over a four year period, six phases of testing were performed to observe the influence of age at loading, applied stress level, mix composition and relative humidity on the tensile creep of concrete. From these investigations it was possible to develop a model which allowed the prediction of tensile creep based on a knowledge of the compressive strength of the concrete (determined at the age of loading), the applied stress level and the relative humidity. Subsequently, this model was validated using the results from three independent investigations. Compressive creep as well as tensile creep was also obtained. This allowed a comparison of compressive creep with tensile creep and illustrated that on the basis of equal stresses, tensile creep is on average between 2 and 3 times greater than compressive creep (the maximum ratio is in excess of 8). For this investigation, however, on the basis of stress/strength ratio the difference between tensile and compressive creep is less significant. Considering a simply supported flexural reinforced concrete element, the investigation suggests that it is unwise to consider actual compressive creep equal to actual tensile creep as is often the case in design practice. 相似文献
83.
It has been demonstrated by experiments that crack can grow under cyclic compressive loading. However, it is difficult to observe and describe accurately by mathematical methods. In addition, cracks may close under compressive loading, which also increases the complexity of the problem. The fatigue growth behavior for surface cracks under biaxial loadings was studied by fatigue tests of HTS-A steel. According to experimental evidences, it is concluded that the transverse compressive stress not only changes the fracture morphology but also affect crack propagation life. Considering the influence of the compressive stress, this paper proposed an equivalent SIF and crack growth model subjected to compressive and bending stresses on the basis of McEvily formula. Finally, comparisons are made between prediction results and experimental data. 相似文献
84.
This paper presents a resistance-based hydrogen gas sensor using polyaniline (emeraldine)/TiO2 nanocomposite (PT–NC) thin film. It is demonstrated that different gas sensing features can arise when various TiO2 phases (anatase and rutile) are applied. The different wt% of TiO2 phases were dispersed into an acidic solution of aniline monomers and PT–NCs were synthesized by an in-situ self-assembly chemical oxidative polymerization method of aniline. PT–NCs deposited on an epoxy glass substrate having Cu-interdigited electrodes for hydrogen gas sensing at air pressure and room temperature. Our results show that the better sensitivity of the sensor strongly depends on the sensor surface morphology and its components. Furthermore, hydrogen gas sensing mechanism of the sensor based contact areas between Pani chains and TiO2 grains was studied. 相似文献
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87.
采用化学氧化聚合法制备出了不同聚噻吩(PTh)掺杂量的PTh/WO3纳米复合材料进行制备,利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)对PTh/WO3纳米复合材料的晶体结构和形貌进行了表征;并研究了PTh/WO3纳米复合材料制备的气敏元件对H2S气体气敏性能。结果表明:PTh/WO3纳米复合材料对H2S气体具有较高的灵敏度,用PTh质量分数为50%的复合材料制成的气敏元件在工作温度为60℃时,对500×10-6的H2S灵敏度达到98,且具有较快的响应与恢复时间。 相似文献
88.
水泥抗压强度的测定过程有成型、养护、破型三个主要环节。各环节的试验条件不同,将直接影响抗压强度的测定结果。研究了水泥试件成型过程中流动度、试件尺寸、表面状态等试验条件对试件抗压强度测定结果的影响。结果表明:在一定范围内水灰比与抗压强度呈正相关关系,即水灰比越大,其流动度越好,抗压强度越高,当超过这个范围后,随着水灰比的增大,抗压强度逐渐减小;随着试件尺寸逐渐变大,抗压强度依次降低;试模涂油量多少不同,导致试件表面状态存在差异,涂油量过多或过少都会使抗压强度的测定结果偏低。 相似文献
89.
Sanjay Paul Rajeev Shrestha T. N. J. I. Edison Yong Rok Lee Sung Hong Kim 《Advanced Synthesis \u0026amp; Catalysis》2016,358(19):3050-3056
An efficient protocol for the direct sulfanylation of various 4‐hydroxycoumarins and 4‐hydroxyquinolinones in good yield with arylsulfonylhydrazides as sulfanylating agents was developed via copper(I) bromide⋅dimethyl sulfide‐catalyzed S–O, S–N bond cleavage and C–S cross‐coupling reactions. A highly selective fluorescence turning‐on sensing of cadmium(II) ions in water using the synthesized 3‐sulfanyl‐4‐hydroxycoumarin derivative was also investigated.
90.
钢筋在拉压循环荷载作用下,会产生受压屈曲现象,其应力-应变曲线呈现受压应力软化效应,传统的钢筋滞回本构模型无法对其进行描述。在Bouc-Wen模型基础上进行修正,引入屈服后刚度比调整公式,建立考虑屈曲影响的钢筋滞回本构模型,并结合Newton-Raphson迭代法给出模型详细计算流程,该模型能够同时描述刚度退化、强度退化以及受压应力软化效应等钢筋滞回特性。模型滞回特性由7个基本参数进行控制,根据所收集的钢筋单轴拉压循环试验数据,采用遗传算法对其进行参数识别。之后考虑钢筋长细比、屈服强度以及强屈比的影响,对参数识别结果进行拟合,给出各控制参数计算公式。最后通过与试验结果进行对比,验证了所提模型的有效性。 相似文献