Propagation and Localization of Longitudinal Thermoelastic Waves in Layered Structures

Based on the generalized dynamical theory of thermoelasticity, a transfer matrix formulation including the second sound effect is developed for longitudinal wave component propagation in a thermoelastic layer. The second sound effect is included to eliminate the thermal wave travelling with infinite velocity as predicted by the diffusion heat transfer model. Using this formulation and the periodic systems framework, the attenuation and propagation properties of one-dimensional thermoelastic waves in both continuum and layered structures are studied. Strong localization of thermal waves predicted by the analysis in the transformed domain is demonstrated in the time-spacial domain by an FFT-based transient analysis. Also, a perturbation analysis for identifying leading terms in thermal attenuation is performed, and the role of the thermal elastic coupling term in attenuation is determined. The attenuation factor, defined as the real part of the propagation constant, is obtained in thermoelastic solids. The reflection and transmission coefficients between half-spaces are also calculated to evaluate the potential practical use of the approach in thermal-based nondestructive testing. [S0739-3717(00)00403-7]

Laser-Based Transient Surface Acceleration of Thermoelastic Layers

The effectiveness of traditional surface cleaning methods, such as ultrasonically induced fluid flow, vibrational methods, centrifugal techniques, is limited to particles that require surface acceleration lower than 107m/s2. For sub-micron particles, a higher level surface acceleration is needed. In the current work, based on the generalized dynamic theory of thermoelasticity, a transfer matrix formulation including the second sound effect is developed for a layer. The transfer matrix for axisysmmetric wave propagation in the thermoelastic layer is obtained by adopting integral transforms. The second sound effect is included to eliminate the immediate arrival of thermal waves. A transfer function formulation for calculating the accelerations is developed for transient analysis. In the current work, only the surface acceleration due to transient thermoelastic wave propagation is under investigation.

Thermal (Heat) Shock Biothermomechanical Viewpoint

Thermal (or heat) shock phenomena have been observed in all organisms at the cellular level. They cause an acceleration in the rate of expression of specific genes (heat shock genes), resulting in an increase and accumulation of heat shock proteins in cells. The purpose of this study is to investigate the mechanisms of thermal shock from two different viewpoints: biothermal and biothermomechanical aspects. The former predicts more severe consequences on cells that the latter, whose thermal wave fronts are smoothed due to the coupling effects of thermoelasticity. In conclusion, it is the thermal wave propagation (the so-called “second sound” effect) which triggers a perturbation of normal gene expression. Thermotolerance is found to be inherited in the heat flux equation of the thermal wave model. The information obtained from this study can also be useful to therapeutical hyperthermia, preservation of organs and tissues, and laser and cryogenic surgery.