Infrared technique for simultaneous determination of temperature and emissivity

Hervé, Philippe; Cedelle, J.; Negreanu, Ionut

doi:10.1016/j.infrared.2010.09.001

Cited by 40 publications

(31 citation statements)

References 5 publications

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“…Depending on the specific temperature and wavelength, the energy radiated by a metallic surface is highly sensitive to any change in the surface condition and therefore is directly proportional to the spectral emissivity of the object [5]. Without a stable emissivity value, it is extremely difficult to achieve accurate temperature measurement with a non-invasive technique such as a pyrometer [1,5,[17][18][19][20][21][22]. Pyrometry does offer non-invasive temperature monitoring and control [23], however the measurement reading is limited to a particular location on the specimen, a limitation shared with TCs [24].…”

Section: Introductionmentioning

confidence: 99%

Enhancing the Accuracy of Advanced High Temperature Mechanical Testing through Thermography

Jones

2018

Applied Sciences

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This paper describes the advantages and enhanced accuracy thermography provides to high temperature mechanical testing. This technique is not only used to monitor, but also to control test specimen temperatures where the infra-red technique enables accurate non-invasive control of rapid thermal cycling for non-metallic materials. Isothermal and dynamic waveforms are employed over a 200-800 • C temperature range to pre-oxidised and coated specimens to assess the capability of the technique. This application shows thermography to be accurate to within ±2 • C of thermocouples, a standardised measurement technique. This work demonstrates the superior visibility of test temperatures previously unobtainable by conventional thermocouples or even more modern pyrometers that thermography can deliver. As a result, the speed and accuracy of thermal profiling, thermal gradient measurements and cold/hot spot identification using the technique has increased significantly to the point where temperature can now be controlled by averaging over a specified area. The increased visibility of specimen temperatures has revealed additional unknown effects such as thermocouple shadowing, preferential crack tip heating within an induction coil, and, fundamental response time of individual measurement techniques which are investigated further.

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Section: Introductionmentioning

confidence: 99%

Enhancing the Accuracy of Advanced High Temperature Mechanical Testing through Thermography

Jones

2018

Applied Sciences

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“…As models TNL.Tabc and TNL.Tab do not use Wien's approximation, no bias appears on estimated temperature except for emissivity variation of order 2 for TNL.Tab, and Drude for the models TNL.Tabc and TNL.Tab. Note that the noise is additive to the flux, but not to the temperature according to (7). The noise will thus lead to a bias on estimated parameters with TNL.TXY, TNL.TX and Tm models.…”

Section: Numerical Validation Of Models For Temperature Measurement Imentioning

confidence: 99%

“…The measurement difficulties are numerous, such as taking into account the reflection on the sample, or spatial and temporal variations of the emissivity of the material, making it non-uniform over the sample surface, especially at high temperature where significant oxidation phenomena can occur. One solution is to make a measurement by the multi-spectral method [2][3][4][5][6][7][8][9], of which a state-of-theart has been made by [4,8]. Even if the idea is interesting, its implementation is tricky because of the difficulty to choose the adapted wavelengths λi.…”

Section: Introductionmentioning

confidence: 99%

“…The facility is presented in section 6, and the considered variations of emissivity used to validate the theoretical models for estimating temperature through an inverse technique based on an ordinary least squares method are shown in section 5. Two different cost functions ((8) and (10)) will be used to estimate this temperature by inverse method: the first uses fluxes ratio and the Wien approximation (7), and the second uses the fluxes (9) (Planck's law without any fluxes ratio).…”

Section: Introductionmentioning

confidence: 99%

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Analogous of Wien's law for the optimal wavelengths selection in bi-spectral method used for temperature measurement of surfaces exhibiting non-uniform emissivity, and general methodology for the multi-spectral method

Rodiet¹,

Rémy²,

Degiovanni³

2014

Proceedings of the 2014 International Conference on Quantitative InfraRed Thermography

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In this paper, a law similar to that of the Wien's law, but to determine the optimal wavelengths in a mono-spectral and a bi-spectral methods (without the Wien's approximation, i.e. for a Planck law) used for temperature measurement of surfaces exhibiting non-uniform emissivity, and a more general methodology (based on the ordinary least squares method) to obtain the optimal wavelengths selection in a multi-spectral method is presented. The goal consists of minimizing the standard deviation of the estimated temperature (optimal design experiment). For the multi-spectral method, two cases will be treated: optimal global, and optimal constrained (to the spectral range of the detector, for example) wavelengths selection are presented. The estimated temperature results obtained by different models taking into account a secondorder polynomial transfer function and including the emissivity variations and for different number of parameters and wavelengths are compared. Different selection criteria are presented. These points are treated from theoretical, numerical and experimental points of view.

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“…Furthermore, those alloys show a thermomechanical behaviour highly dependent on temperature as well as four characteristic temperatures: Ms (Martensite start) initial temperature to form martensite; Mf (Martensite finish) final temperature to form martensite; As (Austenite start) initial temperature to form austenite; Af (Austenite finish) final temperature to form austenite [5]. Notably, in both thermomechanical behaviour and many other applications measuring and quantifying the temperature of the shape memory elementis fundamental [6].…”

Section: Introductionmentioning

confidence: 99%

Emissivity Measurements on Shape Memory Alloys

Silva

Sá²,

Silva

et al. 2016

Proceedings of the 2016 International Conference on Quantitative InfraRed Thermography

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In many applications of Shape Memory Alloys, the most appropriate means and sometimes the only one to measure temperature is thermography, which relies on knowing the emissivity of the material. This paper aims to evaluate experimentally the behavior of the emissivity of a NiTi shape memory alloy as a function of temperature in order to investigate how the emissivity behaves during phase transformation and how it may impact the measured temperature. The emissivity of a Ni55Ti45 shape memory alloy was measured by means of active and passive infrared sensors in a spectral band of 8-14 µm in the temperature range from 25 to 100ºC under a vacuum of 3 x 10 -3 Pa. The results show that the emissivity of the Ni55Ti45 shape memory alloy varied approximately 9% between fully martensitic and fully austenitic states.

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Infrared technique for simultaneous determination of temperature and emissivity

Cited by 40 publications

References 5 publications

Enhancing the Accuracy of Advanced High Temperature Mechanical Testing through Thermography

Enhancing the Accuracy of Advanced High Temperature Mechanical Testing through Thermography

Analogous of Wien's law for the optimal wavelengths selection in bi-spectral method used for temperature measurement of surfaces exhibiting non-uniform emissivity, and general methodology for the multi-spectral method

Emissivity Measurements on Shape Memory Alloys

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