Regression analysis of temperature-dependent mechanical and thermal properties of dielectric technical ceramics

Faoite, Daithí de; Browne, David J.; Stanton, Kenneth T.

doi:10.1007/s10853-012-6759-6

Cited by 14 publications

(6 citation statements)

References 17 publications

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“…For axial cooling, the silicon nitride GCT reaches the greatest fraction of its absolute maximum allowable operation temperature. Despite the higher room temperature thermal conductivity of beryllia, the thermal conductivity of aluminium nitride decreases more slowly with increasing temperature than beryllia does [17,28]. The aluminium nitride GCT therefore reaches a lower peak temperature than the beryllia GCT.…”

Section: Thermal Analysis Resultsmentioning

confidence: 95%

“…Suitable materials for use for the plasma discharge tube, and the properties of these materials have been considered previously by the current authors [17,28].…”

Section: Methodsmentioning

confidence: 99%

“…Temperature-dependent material property data, where available, have been obtained from references [17] and [28], for use in the current thermal-structural analyses. Temperature-dependent properties are not available for some materials.…”

Section: Methodsmentioning

confidence: 99%

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Thermo-structural modelling of a plasma discharge tube for electric propulsion

Faoite

Browne

Gamboa³

et al. 2016

Applied Thermal Engineering

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Publication informationApplied Thermal Engineering, 98 : 541-552 Publisher ElsevierItem record/more information http://hdl.handle.net/10197/8714 Publisher's statement þÿ T h i s i s t h e a u t h o r s v e r s i o n o f a w o r k t h a tAbstract Potential thermal management strategies for the plasma generation section of a VASIMR R high-power electric propulsion space thruster are assessed. The plasma is generated in a discharge tube using helicon waves. The plasma generation process causes a significant thermal load on the plasma discharge tube and on neighbouring components, caused by cross-field particle diffusion and UV radiation. Four potential cooling system design strategies are assessed to deal with this thermal load. Four polycrystalline ceramics are evaluated for use as the plasma discharge tube material: alumina, aluminium nitride, beryllia, and silicon nitride. A finite element analysis (FEA) method was used to model the steady-state temperature and stress fields resulting from the plasma heat flux. Of the four materials assessed aluminium nitride would result in the lowest plasma discharge tube temperatures and stresses. It was found that a design consisting of a monolithic ceramic plasma containment tube fabricated from aluminium nitride would be capable of operating up to a power level of at least 250 kW.

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Section: Thermal Analysis Resultsmentioning

confidence: 95%

“…Suitable materials for use for the plasma discharge tube, and the properties of these materials have been considered previously by the current authors [17,28].…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Thermo-structural modelling of a plasma discharge tube for electric propulsion

Faoite

Browne

Gamboa³

et al. 2016

Applied Thermal Engineering

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“…Temperature-averaged values of thermal diffusivity and effective thermal conductivity were calculated for this temperature range based on published property data [31,32]. The effective thermal conductivity rather than the true thermal conductivity was used, as radiation heat transfer becomes an important heat transfer mechanism in translucent media above ≈ 300 • C. The calculated temperature-averaged thermal diffusivity was 783×10 −9 m 2 ·s −1 , and the temperature-averaged effective thermal conductivity was 1.62 W · m −1 · K −1 .…”

Section: Materials Propertiesmentioning

confidence: 99%

Inverse estimate of heat flux on a plasma discharge tube to steady-state conditions using thermocouple data and a radiation boundary condition

Faoite¹,

Browne²,

Gamboa³

et al. 2014

International Journal of Heat and Mass Transfer

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The heat flux incident upon the inner surface of a plasma discharge tube during a helicon plasma discharge was estimated using an inverse method. Temperature readings were taken from the outer surface of the tube using thermocouples, and the temperature data were interpolated over the tube surface. A numerical inverse procedure based on the Alifanov iterative regularisation method was used to reconstruct the heat flux on the tube inner surface as a function of space and time. In contrast to previously-used inverse models for this application, the current model implements a thermal radiation boundary condition to realistically model the energy exchange in the device. Additionally in these experiments, steady-state operation was reached, and the accurate modelling of the steady-state condition was facilitated by the thermal radiation boundary condition. The variation of heat flux with helicon discharge power, propellant flowrate, and electromagnet current was studied, and it was found that the waste heat flux increased with applied RF power and propellant flowrate, and decreased with current supplied to the electromagnets, over the range of parameter variation tested.

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“…This framework is used in many studies on components having to withstand large temperature changes, including ceramic components under thermal shocks (Han and Wang, 2011;Cheng et al, 2015). For applications of this kind, considering the temperature dependence of the materials is essential in the processes of materials selection (de Faoite et al, 2013), structural analysis (Ching and Chen, 2007), and structural optimization (Bobaru, 2007;Boussaa, 2009).…”

Section: Introductionmentioning

confidence: 99%

Effects of superimposed eigenstrains on the overall thermoelastic moduli of composites

Boussaa

2017

Mechanics of Materials

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This study investigates the effects that an initial local eigenstrain field, when superimposed on the thermal eigenstrain field, has on the overall thermal expansion coefficients and heat capacities of thermoelastic composites. The study can also be seen as an investigation into how a local residual stress field affects these overall moduli, as initial eigenstrains are generally a source of residual stresses. The approach taken is thermodynamic. Expressions that include the superimposed eigenstrain field are developed for the overall moduli within the framework of small strain thermoelasticity with temperature dependent materials. These expressions, which are written in terms of the concentration tensors and residual fields (stress and strain fields given rise to by the eigenstrains under zero overall stress and strain, respectively), contain correction terms that are absent in the expressions developed within linear thermoelasticity. Taking into account the temperature dependence of the constituent moduli is shown to be essential to capture the effects of the superimposed eigenstrain field. A Ti-6Al-4V/ZrO2 composite is investigated for which the correction terms are found to be negligible for the heat capacities but significant for the thermal expansion coefficients. This suggests that, for applications with large temperature changes, using the linear-thermoelasticity-based expressions can affect the accuracy of the estimates of the overall moduli, and therefore the accuracy of thermostructural analyses of composite structures. The proposed expressions can be of use to estimate the overall thermoelastic moduli in contexts in which the strains remain small, temperature changes are large, and superimposed eigenstrains may be present.

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Regression analysis of temperature-dependent mechanical and thermal properties of dielectric technical ceramics

Cited by 14 publications

References 17 publications

Thermo-structural modelling of a plasma discharge tube for electric propulsion

Thermo-structural modelling of a plasma discharge tube for electric propulsion

Inverse estimate of heat flux on a plasma discharge tube to steady-state conditions using thermocouple data and a radiation boundary condition

Effects of superimposed eigenstrains on the overall thermoelastic moduli of composites

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