提高Nadcap认证用热电偶计量管理水平初探

主要介绍AMS 2750E标准对Nadcap认证用热电偶的要求,分析了企业对Nadcap认证用热电偶管理中存在的问题,并提出了解决方案,提高了管理水平。     

真空热处理炉在NADCAP认证过程中的要点与注意事项探析

NADCAP项目是对航空航天工业供应体系内特殊过程工艺生产的过程认证,是与国际知名航空企业进行合作的基础.本文基于北京航材院在NADCAP认证过程中顺利通过的实践经验,分享了对高温测量标准AMS2750E在认证中的要点解读,审核中易犯错误总结及原因分析,不符合项整改纠正措施实施流程等内容的个人见解和经验.     

高温拉伸试验进行NADCAP认证时应注意的技术要点

通过对NADCAP材料测试项目相关标准的解析,重点介绍了材料测试实验室在进行NADCAP材料测试项目高温拉伸试验认证时应注意的技术要点,以助于实验室顺利通过该试验项目的 NADCAP认证,提高实验室的管理水平和技术水平。     

AMS2750F标准的解读与温度传感器的开发

介绍了AMS2750F各章节相较于AMS2750E的主要修订内容,重点分析了第3章技术要求的修订,包括温度传感器、仪表、热处理炉、系统精度校验、温度均匀性测试等方面。此外,详细阐述了符合该标准的温度传感器的开发进展和应用情况,包括高精度热电偶丝和补偿导线的开发与选择、TUS传感器的寿命及强度研究、SAT配套装置的开发、真空炉用温度传感器的开发等。     

光电热电偶

介绍一种以黑体辐射理论为基础的HXW新型高温传感器,该传感器是由探测管和探测器两部分组成,兼有接触式和非接触式测温两类方法的长处。测量方法是用耐高温和耐侵蚀的材料制成人工黑体与被测对象接触,加热至被测温度,用光电探测器接收亮度信号,可用来测量各类高温炉和熔液内部的实际温度。     

热电偶的维修方法

本文介绍了热电偶常见故障产生的原因及排除方法。     

热电偶动态电阻的测量

有的热电偶(如铂铑-铂、镍铬-考铜等热电偶)测量温度时,其内阻随温度的变化有较大的变化,从而给温度测量带来一定的误差。因此,必须测量该热电偶的动态电阻,本文介绍两种测量方法——电桥测量法和万用表测量法。     

基于AMS2750标准对温度仪表校准要求和校准方法的探讨

AMS2750标准《高温测量》是热处理Nadcap特种工艺认证项目的重要内容.温度仪表作为高温测量过程中直接读取温度测试数据的设备,在AMS2750标准中有明确的校准和周期性控制要求.本文针对这些要求,对其中最常用的热电偶信号仪表在周期性校准中校准方法的选用及注意事项进行了研究,通过理论和试验验证了使用标准测试仪表内部...     

检定热电偶的体会

热电偶是中高温区温度测量的主要感温元件，应用极其广泛。由于它直接接触被测介质，容易变化损坏；另外，热电偶输出的毫伏级电压作为二次仪表的输入信号，很微小的变化都会在表头上产生较大的温度变化，引起测量及控制误差。所以，检定热电偶是一项精密的工作，现将我们...     

符合AMS 2750D标准的温度传感器的研制与应用

简述美国标准AMS 2750D中系统准确度测试传感器、炉温均匀性测试传感器、控制温度传感器及负载传感器的性能、用途、分类与选择,以及在线原位校准的优点。详细探讨符合美国标准要求的温度传感器的研制与应用。结果表明,作者研制的2750D用温度传感器,完全满足美国标准要求。     

Monte Carlo studies of multiwavelength pyrometry using linearized equations

Multiwavelength pyrometry has been advertised as giving significant improvement in precision by overdetermining the solution with extra wavelengths and using least squares methods. Hiernaut et al. [1] have described a six-wavelength pyrometer for measurements in the range 2000 to 5000 K. They use the Wien approximation and model the logarithm of the emissivity as a linear function of wavelength in order to produce linear equations. The present work examines the measurement errors associated with their technique.     

Radiance temperatures (in the wavelength range 519–906 nm) of tungsten at its melting point by a pulse-heating technique

Radiance temperatures (at six wavelengths in the range 519–906 nm) of tungsten at its melting point were measured by a pulse-heating technique. The method is based on rapid resistive self-heating of the specimen from room temperature to its melting point in less than 1 s; and on simultaneously measuring the specimen radiance temperatures every 0.5 ms with a high-speed six-wavelength pyrometer. Melting was manifested by a plateau in the radiance temperature versus time function for each wavelength. The melting-point radiance temperatures for a given specimen were determined by averaging the measured temperatures along the plateau at each wavelength. The melting-point radiance temperatures for tungsten were determined by averaging the results at each wavelength for 10 specimens (standard deviation in the range 0.5–1.1 K, depending on the wavelength) as follows: 3319 K at 519 nm, 3236 K at 615 nm, 3207 K at 652 nm, 3157 K at 707 nm, 3078 K at 808 nm, and 2995 K at 906 nm. Based on estimates of the random and systematic errors arising from pyrometry and specimen conditions, the total uncertainty in the reported values is about ±7 K at 653 nm and ± 8 K at the other wavelengths.Paper presented at the Third Workshop on Subsecond Thermophysics, September 17–18, 1992, Graz, Austria.     

Radiance temperatures (in the wavelength range 522–906 nm) of niobium at its melting point by a pulse-heating technique

Radiance temperatures (at six wavelengths in the range 522–906 nm) of niobium at its melting point were measured by a pulse-heating technique. The method is based on rapid resistive self-heating of the specimen from room temperature to its melting point in less than 1 s and on simultaneously measuring the specimen radiance temperatures every 0.5 ms with a high-speed multiwavelength pyrometer. Melting was manifested by a plateau in the radiance temperatureversus-time function for each wavelength. The melting-point radiance temperatures for a given specimen were determined by averaging the measured temperatures along the plateau at each wavelength (standard deviation of an individual temperature from the mean: 0.1–0.4 K). The melting-point radiance temperatures for niobium were determined, by averaging the results at each wavelength for 10 specimens (standard deviation: 0.3 K), as follows: 2497 K at 522 nm, 2445 K at 617 nm, 2422 K at 653 nm, 2393 K at 708 nm, 2337 K at 809 nm, and 2282 K at 906 nm. Based on estimates of the random and systematic errors arising from pyrometry and specimen conditions, the total error in the reported values is about 5 K at 653 nm and 6 K at the other wavelengths.Paper presented at the Second Workshop on Subsecond Thermophysics, September 20–21, 1990, Torino, Italy.     

Ellipsometry in the Study of Dynamic Material Properties

Measurements of the time-dependent absolute temperature of surfaces shocked using high explosives (HE) provide valuable constraints on the equations-of-state (EOS) of materials and on the state of ejecta from those surfaces. In support of these dynamic surface temperature measurements, techniques for measuring the dynamic surface emissivity of shocked metals in the near infrared (IR) are being developed. These consist of time-dependent laser ellipsometric measurements, using several approaches. A discussion of these ellipsometric techniques is included here. Ellipsometry permits an accurate determination of the dynamic emissivity at a given wavelength, and may also provide a signature of melt in shocked metals.     

Radiance temperatures (in the wavelength range 523–907 nm) of group IVB transition metals titanium,zirconium, and hafnium at their melting points by a pulse-heating technique

The melting-point radiance temperatures (at six wavelengths in the range 523–907 nm) of the Group IVB transition metals titanium, zirconium, and hafnium were measured by a pulse-heating technique. The method is based on rapid resistive self-heating of the specimen from room temperature to its melting point in less than 1 s and on simultaneously measuring the specimen radiance temperatures every 0.5 ms with a high-speed six-wavelength pyrometer. Melting was manifested by a plateau in the radiance temperature-versus-time function for each wavelength. The melting-point radiance temperatures for a given specimen were determined by averaging the measured temperatures along the plateau at each wavelength. The melting-point radiance temperatures for each metal were determined by averaging results for several specimens at each wavelength as follows: Based on estimates of the random and systematic errors arising from pyrometry and specimen conditions, the combined uncertainty (95% confidence level) in the reported values is about ±8K at each wavelength.     

Radiance Temperatures (in the Wavelength Range 521 to 1500 nm) of Rhenium and Iridium at Their Melting Points by a Pulse-Heating Technique

The melting-point radiance temperatures (at seven wavelengths in the range 521 to 1500 nm) of rhenium and iridium were measured by a pulse-heating technique. The method is based on rapid resistive self-heating of the specimen from room temperature to its melting point in less than 1 s and on simultaneously measuring the specimen radiance temperature every 0.5 ms with two high-speed pyrometers. Melting was manifested by a plateau in the radiance temperature-versus-time function for each wavelength. The melting-point radiance temperatures for a given specimen were determined by averaging the measured temperatures along the plateau at each wavelength. The melting-point radiance temperatures for each metal were determined by averaging results for several specimens at each wavelength. The results are as follows. Based on estimates of the random and systematic errors arising from pyrometry and specimen conditions, the expanded uncertainty (two standard-deviation level) in the reported values is ±8K.     

Radiance temperatures (in the wavelength range 525 to 906 nm) of vanadium at its melting point by a pulse-heating technique

The radiance temperatures (at six wavelengths in the range 525 to 906 nm) of vanadium at its melting point were measured by a pulse-heating technique. The method is based on rapid resistive self-heating of the specimen from room temperature to its melting point in less than 1 s and on simultaneously measuring the specimen radiance temperatures every 0.5 ms with a high-speed six-wavelength pyrometer. Melting was manifested by a plateau in the radiance temperature-vs-time function for each wavelength. The melting-point radiance temperatures for a given specimen were determined by averaging the measured temperatures along the plateau at each wavelength. The melting-point radiance temperatures for vanadium as determined by averaging the results at each wavelength for 16 specimens (standard deviation in the range 0.3 to 0.4 K. depending on the wavelength) are 2030 K at 525 nm, 1998 K at 622 nm, 1988 K at 652 nm, 1968 K at 714 nm, 1935 K at 809 nm, and 1900 K at 906 nm. Based on estimates of the random and systematic errors that arise from pyrometry and specimen conditions, the resultant uncertainty (2 SD level) in the reported values is about ±7 K at each wavelength.     

About the Proper Wavelength for Pyrometry on Shock Physics Experiments

Usually one wants to measure the thermal radiance emitted by a hot-surface at a wavelength as short as possible, since the uncertainty in the true temperature due to unknown emissivity decreases with decreasing wavelength. Unfortunately the radiance also decreases with decreasing wavelength, and hence the signal-to-noise ratio becomes worse with shorter wavelengths. Depending on what temperature range is to be covered, a reasonable compromise can be found for most applications. When pyrometry is applied to shock physics experiments, there is an additional factor that has to be taken into consideration. Due to the nature of shock physics experiments, one has to deal with background light caused by flashes from air lighting up, high-explosive light, and muzzle flash from a powder gun, etc. In addition, even if the experiment is designed appropriately, there is often a temperature non-uniformity as well as thermal radiation from transparent anvils that are used to increase the interface pressure. In most cases, there is no engineering approach to minimize these temperature non-uniformities. The sensitivity to these non-uniformities increases with decreasing wavelength for the very same reason that the sensitivity to uncertainties in emissivity is increasing. This paper describes the above problems, deals with the problem of temperature non-uniformity in detail, and presents arguments why single-wavelength pyrometry in shock physics experiments can be very deceiving even in well designed experiments.