Thermal Barrier Effect, Non-Fourier Effect and Inertia Effect on a Cracked Plate under Thermal Shock Loading

Abstract : Thermal shock problems occur in many engineering materials and elements, which are used in high temperature applications such as thermal barrier coatings (TBCs), solid propellant of rocket-engine, pulsed-laser processing of materials, and so on. The thermal shock resistance performances and the thermal shock damages of materials, especially the interface debonding and spallation of coatings, have received considerable attention in both analysis and design. Some conventional theories, such as the Fourier’s law of thermal conduction and the quasi-static assumption of the thermoelastic body, may no longer be appropriate because of the extreme loads provoked by the thermal shock. Therefore, these conventional theories need to be enriched or revised.The objective of this thesis is to develop the solutions of the transient temperature field and thermal stresses around a partially insulated crack in a thermoelastic strip under thermal shock loading. The crack lies parallel to the heated traction free surface. The thermal conductivity of the crack gap is taken into account. Hyperbolic heat conduction theory is used in solving the temperature field instead of the traditional Fourier thermal conduction theory. Equations of motion are applied to obtain the stress fields and the dynamic stress intensity factors of the crack. The Laplace and Fourier transforms are applied to solve the thermal-elastic governing equations such that the mixed boundary value problems are reduced to solving a singular integral equations system in Laplace-Fourier space. The numerical integration method is applied to get the temperature field and stress fields, respectively. The problems are then solved numerically by converting the singular integral equations to a linear algebraic equations system. Finally, numerical inversions of the Laplace transform are performed to obtain the temperature field and dynamic stress intensity factors in the time domain.Numerical results show that the thermal conductivity of the crack gap strongly affects the uniformity of the temperature field and consequently, the magnitude of the dynamic stress intensity factors of the crack. The stress intensity factors would have higher amplitude and oscillating feature comparing to those obtained under the conventional Fourier thermal conduction and quasi-static hypotheses. It is also observed that the interactions of the thermal conductivity of the crack gap, the non-Fourier effect and the inertia effects would make the dynamic thermal shock problem more complex. The magnitude of the thermal barrier, non-Fourier and inertia effects is estimated for some practical cases.
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Wei Li. Thermal Barrier Effect, Non-Fourier Effect and Inertia Effect on a Cracked Plate under Thermal Shock Loading. Other. Université Sorbonne Paris Cité, 2016. English. ⟨NNT : 2016USPCD089⟩. ⟨tel-02165931⟩

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