Vol 62, No 10 (2017)

The critical sizes of pores, determined by surface tension forces, have been determined. It is shown that the pore size in a material cannot be lower than some critical value.

Comparative analysis of optical damage thresholds of potassium and sodium chloride surface by pulses with durations of 80 and 40 fs has been carried out. The critical radiation power in a pulse at the optical damage threshold for the ion crystals studied has been determined. An estimate of the optical damage thresholds of the sodium chloride surface by laser pulses with a duration of 20 fs is presented.

The distributed lateral load on a plate located in a gas medium has been determined. The difference in the gas pressures of the plate surfaces results in a pressure drop and a lateral force, which depends on the middle surface curvature. It is shown that both these components of the lateral force must be taken into account in the general case. The influence of the second load component is small at a small ratio of the average pressure to the elastic modulus of the plate material and at a large relative thickness of the plate. At a small relative plate thickness and a large ratio of the average pressure of the medium to the elastic modulus of the plate material, the influence of the second component of the lateral load on the bending becomes significant. Cases of both linear and nonlinear plate bending are considered.

The monotonicity of the CABARET scheme approximating the quasi-linear scalar conservation law with nonconvex flux is analyzed. The conditions of monotonicity of this scheme are obtained in the case when the speed of propagation of characteristics of the approximated equation is limited and nonnegative. As an example, the test calculations by the CABARET scheme of discontinuous solutions of the Buckley–Leverett equation are presented.

The problem on acoustic-wave reflection from the boundary of a gas−droplet mixture is considered. For the interface between the pure gas and the gas−droplet mixture at a wave inclined incidence, a nonmonotonic dependence of the reflectance on the volume content of droplets is established. The values of the critical wave-incidence angle and the volume content of inclusions at which the reflectance vanishes are found and illustrated. The possibility of occurrence of the lowest reflectance in dependence on the frequency of perturbations in a certain interval of the wave-incidence angle related mainly to the difference in the densities of the gas-droplet mixture and the pure gas is shown.

The mechanical properties of various components of the Chelyabinsk meteorite are studied. A measurement technique allowing one to obtain a strength certificate of the material by a minimum necessary number of samples with allowance for defectiveness is developed. Universal expressions for the chondritic component and impact melting have been obtained. The expressions allow one to make general estimates of the strength boundaries for LL type meteorites.