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Full-Text Articles in Physics

Two-Temperature Discrete Model For Nonlocal Heat Conduction, Sergey Sobolev Dec 1993

Two-Temperature Discrete Model For Nonlocal Heat Conduction, Sergey Sobolev

Sergey Sobolev

The two-temperature discrete model for heat conduction in heterogeneous media is proposed. It is shown that the discrete model contains as limiting cases both hyperbolic and parabolic heat conduction equations for propagative and diffusive regimes, respectively. To obtain these limiting cases two different laws of continuum limit have been introduced. The evolution of the two-temperature system comprises three stages with distinct time scales : fast relaxation of each subsystem to local equilibrium, energy exchange between the subsystems and classical hydrodynamics.


The Use Of Optical Beam Deflection (Obd) Technique In The Thermal Diffusivity Characterization Of Polymer Foils, J. Rantala, Lanhua Wei, P. K. Kuo, J. Jaarinen, M. Luukkala, R. L. Thomas Jan 1993

The Use Of Optical Beam Deflection (Obd) Technique In The Thermal Diffusivity Characterization Of Polymer Foils, J. Rantala, Lanhua Wei, P. K. Kuo, J. Jaarinen, M. Luukkala, R. L. Thomas

Review of Progress in Quantitative Nondestructive Evaluation

The rapid progress in development of new materials has also created more demands on their testing and characterization methods. In spite of the wide use of different plastics, there is a lack of methods to measure thermal diffusivity of polymers and other low-diffusivity materials. The diffusivity determination of oriented polymers is of particular interest: the drawing of a polymer foil orients the molecular chains, which strengthens the foil mechanically and also causes anisotropy to thermal conductivity making it higher parallel to the drawing direction than perpendicular to it. Anisotropy ratios as high as 100 have been reported [1]. The diffusivity ...


Reluctance Variation As A Result Of Lift Off For An Ac Magnetic Bridge, William F. Schmidt, Otto H. Zinke Jan 1993

Reluctance Variation As A Result Of Lift Off For An Ac Magnetic Bridge, William F. Schmidt, Otto H. Zinke

Review of Progress in Quantitative Nondestructive Evaluation

To optimize the sensitivity and minimize lift-off effects of electromagnetic NDE devices requires an understanding of the source and distribution of electromagnetic fields. This understanding is particularly difficult when conductive devices other than the sample are in the vicinity of the field. Such is the case with the modified AC magnetic bridge [1] which has a conducting insert in the vicinity of the gap in proximity to the sample.


Thermal Coating Characterization Using Thermoelasticity, Christopher S. Welch, Michael J. Zickel Jan 1993

Thermal Coating Characterization Using Thermoelasticity, Christopher S. Welch, Michael J. Zickel

Review of Progress in Quantitative Nondestructive Evaluation

Synchronous demodulation techniques have been used for some time to measure thermal radiation produced by the small temperature changes associated with elastic stress in materials, the thermoelastic effect[l]. As reviewed in [2], these measurements have been employed primarily for inferring stress distributions in materials from the associated temperature distributions. Images of stress distribution have been made most often by assembling a large number of individual synchronous component measurements using specialized equipment [3]. Other investigators [4,5] have used subtraction of stroboscopic samples to build up similar images. Recently, techniques using full-field synchronous demodulation [6,7] have been reported using ...


Fast Photothermal Inspection Of Plasma-Sprayed Coatings Of Primary Circulation Seal Rings Of A Nuclear Reactor. Part Two: After The Trial Run, R. Lehtiniemi, J. Hartikainen, J. Rantala, J. Varis, M. Luukkala Jan 1993

Fast Photothermal Inspection Of Plasma-Sprayed Coatings Of Primary Circulation Seal Rings Of A Nuclear Reactor. Part Two: After The Trial Run, R. Lehtiniemi, J. Hartikainen, J. Rantala, J. Varis, M. Luukkala

Review of Progress in Quantitative Nondestructive Evaluation

In the 1991 QNDE conference [1] we described a photothermal inspection of the plasma-sprayed coatings of two seal rings used in the main pump of the primary circulation in the PWR-type nuclear reactor. The measurements concentrated on detecting the most critical flaw type, adhesion defects at the interface between the coating and the substrate. The samples were tested immediately after they were coated and lapped, and already then two thermal anomalies could be found.