共查询到18条相似文献,搜索用时 171 毫秒
1.
2.
3.
激光闪光法是测量材料热扩散率的一种瞬态测量方法,是测量速度最快的方法之一,也是目前最受欢迎的方法之一.通过对闪光法测量装置中激光器输出光斑的实时探测,发现大能量下光斑分布的均匀程度明显优于小能量下的分布情况.通过设计实验,验证了光斑的这种分布情况以及激光非均匀加热对热扩散率测量结果确有一定影响.为此,特设计一套光学装置... 相似文献
4.
5.
6.
7.
8.
空气耦合超声探头接收的信号微弱,并且容易受到电磁噪声的干扰,信噪比低,不利于后期的采集与处理。针对上述问题,设计了一种以仪表放大器AD8429芯片为核心的微弱信号调理电路。该调理电路分为三部分,第一部分为电压跟随器组成的输入级,第二部分为高精度、低噪声的三级级联放大电路,第三部分为无限增益多路反馈带通滤波电路,最后,将整个电路置入金属纤维屏蔽罩,以达到抑制外界高频电磁干扰的目的。实验结果表明,所设计电路检测下限可达200μV,实际增益最高为79.6 dB,相对误差控制在10%以下,利用此电路可以成功提取400 kHz的超声检测信号。 相似文献
9.
将光纤传感技术与传统的红外水分测定方法相结合,设计了一种光纤束传感器来实现发射光和接收光的传输.为将接收二极管上的微弱信号送到A/D转换器处理,采用锁定放大原理设计接收信号的调理电路.在不影响测量精度的情况下,能使红外水分测定系统变得更简单、更廉价. 相似文献
10.
11.
12.
Katsunori Inoue 《Materials at High Temperatures》2013,30(1):21-26
The theoretical equation for the laser flash method is derived where the penetration and transmission of the input energy into the test piece is taken into account. The thermal diffusivity of penetrative materials and its measurement errors are calculated instantly by fitting the experimental data to this equation by using the method of least squares with an on-line personal computer connected to the laser flash device. The usefulness of this method is shown by comparing it with the conventional method. 相似文献
13.
The National Metrology Institute of Japan (NMIJ) of AIST has been studying the laser flash method in order to establish an SI traceable thermal- diffusivity standard. Key technologies have been developed to reduce the uncertainty in laser flash measurements. In the present study, an uncertainty evaluation has been carried out on the laser flash measurement method in order to determine the thermal diffusivity value of IG-110, a grade of isotropic high-density graphite, as a candidate reference material. The thermal diffusivity measured by the laser flash method is derived from a specimen thickness and a heat diffusion time. And a laser flash measurement is carried out at a given temperature. The measurement system is composed of three sections corresponding to each measured quantity: length, time, and temperature. Therefore, we checked and calibrated our measurement system, and estimated the uncertainty of measurement results for the case of a grade of isotropic graphite.Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic. 相似文献
15.
激光脉冲法在应用于测量对实验探测波段红外线半透明的材料热扩散率时遇到了困难。文中提出了新的解决办法:即通过对理论探测曲线进行分析,并通过在实际探测曲线上的升温幅度和特征点计算得到了热扩散率,成功地解决了这一难题。在-73℃~290℃的范围内获得了对激光和红外线都是半透明的聚酰亚胺(PI)薄膜的热扩散率,并研究了室温下PI/SiO2复合材料的热扩散率随SiO2含量的变化规律。 相似文献
16.
New experimental data on the thermal diffusivity of gadolinium in the temperature interval from 287 to 1277 K obtained by the laser flash method with an error of 3–4% are presented. Results are compared with the available literature data. Reference tables on the heat transfer coefficients of gadolinium for scientific and practical use are developed. Critical indices for the thermal diffusivity of gadolinium above the Curie point are determined. The limitations of the laser flash method during measurement in the region of phase transformations are briefly discussed. 相似文献
17.
Evaluation of the radiative and conductive heat loss from a molten metal sample to the cell has been made in order to obtain accurate thermal diffusivities of molten metals at high temperature with a laser flash method. The results suggest that thermal diffusivity values of molten nickel can be determined in the temperature range from 1728 to 1928 K with an uncertainty of ±3% in comparison with case considering only the effect of radiative heat loss. The usefulness of a cell for a laser flash method has been confirmed by applying simulated results to evaluate the heat leakage in the thermal diffusivity measurement of molten metals. 相似文献
18.
材料发生相变时, 其结构和物理性能可能会发生剧烈的变化。采用激光闪射法测量热扩散系数时, 激光照射样品可能会伴随有光吸收/发射现象以及温度的显著升高, 导致其测量值偏离真实值。本工作以Cu2S为研究对象, 发现激光照射样品后, 光吸收/发射的影响很小可以忽略, 但样品温度的升高则会明显影响热扩散系数的测量。通过构建具有不同石墨层厚度的石墨/Cu2S双层结构, 利用石墨层减弱激光照射时Cu2S样品的温度增加幅度, 成功使热扩散系数出现显著降低的起始温度接近采用DSC测量材料发生相变的起始温度。本研究进一步建立了石墨/Cu2S双层结构样品的热流输运模型, 从石墨/Cu2S双层结构样品的实验测试热扩散系数中解析出了Cu2S在相变区间的本征热扩散系数。本工作对于理解和精确表征具有相变特征的离子导体热电材料、光敏、热敏材料的热扩散系数具有重要的意义。 相似文献