Temperature and Finite Pulse-Time Effects in the Flash Method for Measuring Thermal Diffusivity

Cape, J. A.; Lehman, G. W.

doi:10.1063/1.1729711

Cited by 491 publications

(181 citation statements)

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“…The thermal diffusivity and the specific heat capacity of a bare stainless steel substrate with a thickness of 0.51 mm were measured by the laser flash method from ambient temperature to 1000 °C. The measurements were corrected to take into account the radiation loss [27] and the finite shot pulse of the laser [28], and can respectively be fitted, in the temperature range, to the following equations: …”

Section: Thermal Properties Of Aisi 304mentioning

confidence: 99%

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Thermal and mechanical properties of crack-designed thick lanthanum zirconate coatings

Weber

Lein

Grande

et al. 2014

Journal of the European Ceramic Society

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Vertical cracks are beneficial in thermal barrier coatings due to enhanced thermomechanical compliance. Accordingly, an aqueous nitrate based precursor solution was atomized on stainless steel substrates by spray pyrolysis to deposit thick crack-designed lanthanum zirconate coatings. Coatings with designed crack patterns were deposited and characterized by electron microscopy, tribology, Vickers indentation, and thermal diffusivity. The crystallization of the coatings was investigated by in situ high temperature X-ray diffraction. The green coatings crystallized from 600 °C and the pyrochlore structure was formed after heat treatment at 1000 °C. Crystalline lanthanum zirconate multilayered coatings with small crack spacing and crack opening exhibited a higher density, a higher hardness, lower thermal diffusivities, and higher thermal conductivities compared to crystalline monolayered coatings of similar thickness with large crack spacing and crack opening. The thermal diffusivity of the coatings, ~28 mm 2 /s at room temperature, was similar to the values reported for yttria-stabilized zirconia plasma sprayed coatings.

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Section: Thermal Properties Of Aisi 304mentioning

confidence: 99%

“…The finite shot pulse of the laser was corrected first [28]. Two different models were then applied to fit the experimental data.…”

Section: Thermal Diffusivity Of the Coatingsmentioning

confidence: 99%

Thermal and mechanical properties of crack-designed thick lanthanum zirconate coatings

Weber

Lein

Grande

et al. 2014

Journal of the European Ceramic Society

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“…In such a circumstance, the effects of finite pulse-time have been studied by Larson et al, 5) Taylor et al 6) and Cape et al 7) Larson et al has applied the empirical exponential type pulse representing the output from xenon flash lamp on the theoretical analysis (Eq. (5)).…”

Section: Effect Of Finite Pulse-time (Shape Of Pulse)mentioning

confidence: 99%

Factors on the Measurement of Effective Thermal Diffusivity of Molten Slag Using Double Hot Thermocouple Technique.

Kashiwaya

Ishii

2002

ISIJ International

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The molten slags that are used not only in the continuous caster but also in every metal industry play an important role and affect the quality of products. The authors initially developed the double hot thermocouple technique (DHTT) for in situ observation of mold slag crystallization.In this study, the DHTT was further developed to allow the measurement of the overall thermal diffusivity of molten slag applying the principle of the laser flash method. The affecting factors (finite pulse time, shape of pulse and heat loss from sample surface) on the measurement of thermal diffusivity using the DHTT were discussed theoretically using both the analytical and the numerical methods. New relationship between the thermal diffusivity a and the time at half-maximum temperature t 0.5 was obtained as follows:a(ϫ10 4 m 2 /s)ϭ0.000707(t 0.5 /t p ) Ϫ1.8946 The thermal diffusivity obtained from the experimental half-maximum time t 0.5 /t p (t p is the time of peak on the heat pulse) was in good agreement with the one from literature.KEY WORDS: thermal diffusivity; thermal conductivity; slag melt; laser flash; hot thermocouple; DHTT.DHTT and the laser flash method. The laser flash method is an excellent method and can predict a relatively suitable value of thermal diffusivity using Parker's method 4) (Eq. (3)). However, it will need a special alignment for the measurement of liquid and/or transparent material. Furthermore, a direct observation during measurement is almost impossible. On the other hand, the DHTT can observe the molten sample in situ. As shown in the previous study, 1,2) the solidification of mold slag is complicate phenomena including the bubble formation/breaking and the crystallization. It would be very important to know the sample image during measurement. The thermal diffusivity obtained from DHTT, however, is not yet established and it is not reported what kinds of factors affected on the measurement until now.For the preliminary approach to the application of the DHTT to the measurement of thermal diffusivity, the affecting factors on the measurement were elucidated from both the theoretical and the experimental method. In the case of laser flash method, an instantaneous laser pulse was used as a heat source and the temperature increase at the rear surface was measured by an infrared pyrometer (IR detector). In the case of DHTT, the temperature of one side thermocouple (CH-1, in Fig. 1) increased in a pulse shape and the other side of thermocouple (CH-2) was used as a detector. The typical temperature profiles of both CH-1 and CH-2 are shown in Fig. 2. The time t 0.5 at the half-maximum temperature (1/2 DT max ) was defined as shown in Fig. 2 and used for the calculation of thermal diffusivity according to the laser flash method (the details will be shown in below). The large differences between the laser flash method and DHTT are as follows: (1) Heat source is the order of several seconds (millisecond order in laser flash method). (2) Shape of pulse is not square. This factor might be decisive in bo...

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“…Since its development, many corrections have been introduced to this relation to account for radiative heat losses, the laser pulse finite width, non-uniform heating of the sample, and other related experimental factors. [32][33][34][35][36][37][38][39][40] However, the remaining practical limitations to this approach are that the measurements are one-dimensional and require simultaneous access to both the front and back surface.…”

Section: Energy Balance Metricmentioning

confidence: 99%

Advanced Signal Processing for Thermal Flaw Detection

Valley¹,

Hansche²,

Paez³

et al. 2001

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Dynamic thermography is a promising technology for inspecting metallic and composite structures used in high-consequence industries. However, the reliability and inspection sensitivity of this technology has historically been limited by the need for extensive operator experience and the use of human judgment and visual acuity to detect flaws in the large volume of infrared image data collected. To overcome these limitations new automated data analysis algorithms and software is needed. The primary objectives of this research effort were to develop a data processing methodology that is tied to the underlying physics, which reduces or removes the data interpretation requirements, and which eliminates the need to look at significant numbers of data frames to determine if a flaw is present. Considering the strengths and weakness of previous research efforts, this research elected to couple both the temporal and spatial attributes of the surface temperature. Of the possible algorithms investigated, the best performing was a radiance weighted root mean square Laplacian metric that included a multiplicative surface effect correction factor and a novel spatio-temporal parametric model for data smoothing. This metric demonstrated the potential for detecting flaws smaller than 0.075" in inspection areas on the order of one square foot. Included in this report is the development of a thermal imaging model, a weighted least squares thermal data smoothing algorithm, simulation and experimental flaw detection results, and an overview of the ATAC (Automated Thermal Analysis Code) software that was developed to analyze thermal inspection data. 6 CONTENTS

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Temperature and Finite Pulse-Time Effects in the Flash Method for Measuring Thermal Diffusivity

Cited by 491 publications

References 1 publication

Thermal and mechanical properties of crack-designed thick lanthanum zirconate coatings

Thermal and mechanical properties of crack-designed thick lanthanum zirconate coatings

Factors on the Measurement of Effective Thermal Diffusivity of Molten Slag Using Double Hot Thermocouple Technique.

Advanced Signal Processing for Thermal Flaw Detection

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