Evaluation of effective absorption coefficient during laser irradiation using of metals martensite transformation

The paper presents a method for determination of effective absorption coefficient of irradiation during action of a pulsed laser. For this purpose the solution of some axisymmetrical boundary value problem of heat conduction for half-space and the experimentally obtained polymorphous zones of transformation in the exposed materials are applied. The verification of the methodology is given for St 45 steel and the monocrystal cobalt samples.     

On Thermal Contact of Two Axially Symmetric Elastic Solids

A contact problem of two elastic convex and axially symmetric solids heated (or cooled) to temperatures of different values is considered. Pertinent formulae have been derived for relations between the contact pressure, geometrical characteristics of the solids and distributions of heat flux over the contacting region. We have analysed: 1. The problem of the loss of the contact between two solids pressed together with active heat fluxes. We discuss the cases for which the contact of the axially symmetric solids can take the form of a circle, or an annulus. 2. The problem of a paradox when the mathematically well posed contact problem of thermoelasticity leads to a physically unacceptable solution with a region of overlapping materials. Here we discuss a generalization of the cooled sphere paradox. The heat flux functions are continuously differentiable, of constant sign. The conditions have been derived for the cases when the paradox can be avoided.     

Temperature and thermal stresses in material of a pad during braking

The transient temperature field and corresponding quasi-static thermal stresses are analysed in a system consisting of a semi-space and a strip. The strip is heated on its outer surface by a heat flux with the intensity equal to the specific power of friction during braking with a uniform retardation. The evolution and distribution in depth from a surface of friction for temperatures and thermal stresses were investigated for the metal-ceramic FMK-11 material of the strip.     

Investigation of Correlation of Test Sequences for Reliability Testing of Digital Physical System Components

Russian Physics Journal - The topical problem of effective verification of digital circuits of different physical systems remains a hot topic. Devices ranging from embedded components to perform...     

Low-frequency properties of quasi-particles with arbitrary dispersion relation in ac electromagnetic and constant magnetic fields

An effective Hamiltonian for the conduction band electrons in semiconductors with arbitrary dispersion relation in both ac electromagnetic and constant magnetic fields is obtained. It is shown that the combined influence of ac electromagnetic and constant magnetic fields can qualitatively alter the properties of the dispersion relation, including its symmetry. This results in a change of the low-frequency properties of the system. A semiconductor with a quantum superlattice is used as an example of the phenomena described.     

Superbosonization Formula and its Application to Random Matrix Theory

Starting from Gaussian random matrix models we derive a new supermatrix field theory model. In contrast to the conventional non-linear sigma models, the new model is applicable for any range of correlations of the elements of the random matrices. We clarify the domain of integration for the supermatrices, and give a demonstration of how the model works by calculating the density of states for an ensemble of almost diagonal matrices. It is also shown how one can reduce the supermatrix model to the conventional sigma model.     

Verifying Digital Components of Physical Systems: Experimental Evaluation of Test Quality

Russian Physics Journal - This paper continues the study of high quality test derivation for verifying digital components which are used in various physical systems; those are sensors, data...     

Directed current due to broken time-space symmetry

We consider the classical dynamics of a particle in a one-dimensional space-periodic potential U(X) = U(X+2pi) under the influence of a time-periodic space-homogeneous external field E(t) = E(t+T). If E(t) is neither a symmetric function of t nor antisymmetric under time shifts E(t+/-T/2) not equal-E(t), an ensemble of trajectories with zero current at t = 0 yields a nonzero finite current as t-->infinity. We explain this effect using symmetry considerations and perturbation theory. Finally we add dissipation (friction) and demonstrate that the resulting set of attractors keeps the broken symmetry property in the basins of attraction and leads to directed currents as well.     

Influence of the temporal profile of the contact pressure on the maximal temperature in pad/disc tribosystem

The solution to a thermal problem of friction during braking for a pad/disc (strip/semi-space) tribosystem with a time-dependence upon friction power is obtained. The convective cooling on an upper surface of a strip and the heat transfer through a contact surface are considered, too. The influence of duration of increase in pressure from zero (at the initial moment of time) to nominal value (at the moment of a stop) on the maximal temperature for a friction pair metal-ceramic pad/cast iron disc is studied.     

Temperature field in a microperiodic two-layered composite caused by a circular laser heat source

The paper is connected with the determination of␣temperature field in a periodically layered half-space caused by a laser heating. Two types of thermal loadings distributed on a boundary of the body is considered: uniform and normal (Gaussian). The influence of geometrical and thermal parameters of the layered composite on the temperature field is analyzed. Received on 27 November 1997