scholarly journals Spectral Absorption Coefficient of Additive Manufacturing Materials

2021 ◽  
Vol 13 (4) ◽  
Author(s):  
Nicholas J. Wallace ◽  
Matthew R. Jones ◽  
Nathan B. Crane
Keyword(s):  
Additive Manufacturing ◽  
Absorption Coefficient ◽  
Radiative Heat ◽  
Manufacturing Processes ◽  
Spectral Absorption ◽  
Spectral Absorption Coefficient ◽  
Polyamide 12 ◽  
Active Thermography ◽  
Uncertainty Estimates ◽  
Properties Of Materials

Abstract Active thermography techniques are of interest for quality assurance of additive manufacturing processes. However, accurate measurements of thermophysical properties of materials are required to successfully implement active thermography. In particular, the spectral absorption coefficient of materials commonly used in additive manufacturing must be known to accurately predict the spatial distribution of thermal energy generated from absorption of power emitted by a laser or pulsed flash lamp. Accurate measurements of these optical properties are also needed to develop greater understanding of additive manufacturing processes that rely on radiative heat transfer to fuse powders. This paper presents spectral absorption coefficient measurements and uncertainty estimates of fully and partially dense ABS, PLA, and Polyamide 12 samples.

A Method of Measuring the Temperature Profile of a Thermal Barrier Coating Using Inverse Radiative Heat Transfer Methods

2011 ◽  
Author(s):  
Travis J. Moore ◽  
Matthew R. Jones
Keyword(s):  
Heat Transfer ◽  
Measurement Error ◽  
Absorption Coefficient ◽  
Temperature Profile ◽  
Radiative Heat ◽  
Thermal Barrier ◽  
Spectral Absorption ◽  
Spectral Absorption Coefficient ◽  
Barrier Coating ◽  
Spectral Emittance

Ceramic thermal barrier coatings (TBCs) are used in power generation and aerospace turbines to protect superalloy components from large and extended heat loads. These coatings allow for increased inlet temperatures, thereby increasing efficiency and reducing air cooling requirements. Knowledge of the temperature profile in a thermal barrier coating is critical for evaluating the TBC performance and monitoring its health, as well as for accurate simulation and modeling. Non-contact, non-destructive techniques for finding these temperature profiles are highly desirable. Current techniques are limited in that they cannot measure the entire temperature profile of the TBC along with its radiative properties. An inverse radiative heat transfer method capable of determining the temperature profile, as well as the spectral absorption coefficient and spectral emittance at various wavenumbers, of a TBC using non-contact techniques was developed. A model of the measurements of the intensity exiting the TBC, which account for the emission from the substrate as well as the emission and absorption of the TBC itself, was developed. The TBC was approximated as a one-dimensional, plane-parallel, non-scattering medium. Optimization methods were used to determine the desired parameters by minimizing the error between actual intensity measurements and those calculated from the model. This method was tested for a number of simulated measurements with and without measurement error. Even with 10% measurement error introduced, the base temperature of the TBC was determined with only 0.45% error while the error in the TBC surface temperature measurement was 3.36% and that in the spectral emittance of the bondcoat was 12%. The error in the spectral absorption coefficient was significant.

Multi-Dimensional Radiative Transfer in Nongray Gases—General Formulation and the Bulk Radiative Exchange Approximation

1978 ◽  
Vol 100 (3) ◽  
pp. 486-491 ◽  
Author(s):  
S. S. Tsai ◽  
S. H. Chan
Keyword(s):  
Heat Flux ◽  
Radiative Transfer ◽  
Absorption Coefficient ◽  
Radiative Heat ◽  
Spectral Absorption ◽  
Spectral Absorption Coefficient ◽  
Multidimensional Problems ◽  
All Optical ◽  
Exchange Approximation ◽  
Radiative Exchange

The present paper presents a general formulation of the radiative heat flux and its divergence for multi-dimensional radiative problems involving nongray absorbing-emitting gases. The expressions obtained are in terms of total band absorptance rather than the spectral absorption coefficient. Thus the frequency integration is eliminated, and the expressions are more compact. They avoid the necessity of detailed spectral absorption coefficient data for radiative transfer computations. Also presented is the bulk radiative exchange approximation together with its refinement. It is proposed to circumvent the mathematical complexity inherently imbedded in nongray multidimensional problems. The approximation, which is valid in the optically thin and thick limits, is found to be general and useful, not only because of its simplicity, but also because of its accuracy in all optical conditions.

Spectral Absorption Coefficient of Molten Aluminum Oxide from.0.385 to 0.780 mum

1995 ◽  
Vol 78 (3) ◽  
pp. 583-587 ◽  
Author(s):  
J. K. Richard Weber ◽  
Shankar Krishnan ◽  
Collin D. Anderson ◽  
Paul C. Nordine
Keyword(s):  
Absorption Coefficient ◽  
Aluminum Oxide ◽  
Molten Aluminum ◽  
Spectral Absorption ◽  
Spectral Absorption Coefficient

scholarly journals Simple methods for identification of radiative properties of highly-porous ceria ceramics in the range of semi-transparency

2017 ◽  
Vol 27 (5) ◽  
pp. 1108-1117 ◽  
Author(s):  
Leonid A. Dombrovsky ◽  
Wojciech Lipinski
Keyword(s):  
Absorption Coefficient ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Radiative Properties ◽  
Spectral Absorption ◽  
Spectral Absorption Coefficient ◽  
Content Type ◽  
Hemispherical Reflectance ◽  
Steady Oscillations ◽  
Highly Porous

Purpose The aim of this paper is to present advanced experimental–numerical methods for identification of spectral absorption and scattering properties of highly porous ceria ceramics in the range of semi-transparency at room and elevated temperatures. Design/methodology/approach At room temperature, a period of quasi-steady oscillations of the sample surface temperature generated in response to recurrent laser heating at fixed values of the maximum and minimum temperature of the irradiated surface is measured along with the normal-hemispherical reflectance. Radiative properties are then identified using a combined heat transfer model. At elevated temperatures, an analytical solution proposed in an earlier study for zirconia ceramics is used to retrieve spectral absorption coefficient of ceria ceramics from the measured normal emittance. Findings and Originality/value This method can be used to obtain small absorption coefficient of ceria ceramics at room temperature. The required measurements of both the normal-hemispherical reflectance and the period of quasi-steady oscillations of the irradiated surface temperature of the ceramics sample between fixed values of the maximum and minimum temperatures can be readily conducted using thermal laboratory equipment. Another method has been suggested for identification of the spectral absorption coefficient of ceria ceramics at elevated temperatures. This method is based on a relation between the measured normal emittance of an isothermal sample and the absorption coefficient.

scholarly journals The spectral absorption coefficient at 254 nm as a real-time early warning proxy for detecting faecal pollution events at alpine karst water resources

2010 ◽  
Vol 62 (8) ◽  
pp. 1898-1906 ◽  
Author(s):  
H. Stadler ◽  
E. Klock ◽  
P. Skritek ◽  
R. L. Mach ◽  
W. Zerobin ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Real Time ◽  
Early Warning ◽  
Data Communication ◽  
Spring Water ◽  
Karst Water ◽  
Spectral Absorption ◽  
Sampling Device ◽  
Spectral Absorption Coefficient ◽  
Faecal Pollution

Because spring water quality from alpine karst aquifers can change very rapidly during event situations, water abstraction management has to be performed in near real-time. Four summer events (2005–2008) at alpine karst springs were investigated in detail in order to evaluate the spectral absorption coefficient at 254 nm (SAC254) as a real-time early warning proxy for faecal pollution. For the investigation Low-Earth-Orbit (LEO) Satellite-based data communication between portable hydrometeorological measuring stations and an automated microbiological sampling device was used. The method for event triggered microbial sampling and analyzing was already established and described in a previous paper. Data analysis including on-line event characterisation (i.e. precipitation, discharge, turbidity, SAC254) and comprehensive E. coli determination (n>800) indicated that SAC254 is a useful early warning proxy. Irrespective of the studied event situations SAC254 always increased 3 to 6 hours earlier than the onset of faecal pollution, featuring different correlation phases. Furthermore, it seems also possible to use SAC254 as a real-time proxy parameter for estimating the extent of faecal pollution after establishing specific spring and event-type calibrations that take into consideration the variability of the occurrence and the transferability of faecal material It should be highlighted that diffuse faecal pollution from wildlife and live stock sources was responsible for spring water contamination at the investigated catchments. In this respect, the SAC254 can also provide useful information to support microbial source tracking efforts where different situations of infiltration have to be investigated.

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