Vol 61, No 7 (2016)

The results of experiments on studying the perlite–ferrite structure in steels under short-term negative pressures are described. It is shown that in the localized deformation bands formed in the zone of interference of unloading waves, where the tension stress is lower than the dynamic strength of the material, the cementite bands in perlite are crushed, their fragments are in part dissolved and enriched with carbon, and the cementite can pass into a steady spherical form on the boundary with ferrite. At relatively high shock-wave amplitudes, the perlite in its entirety acquires a spheroidal shape.

The linear theory of damping of radial vibrations of a bubble in a liquid is constructed by taking into account the key dissipative mechanisms: thermal, viscous, and acoustic. The basic approximation of homobaricity made helps to obtain the results in a convenient and simple form. The results obtained for damping are used further in the description of the forced resonant oscillations of a bubble in an acoustic wave with the frequency equal to the eigenfrequency of the radial oscillation mode and twice as high as the frequency of the deformation oscillation mode (resonance 2:2:1). It is shown that the amplitude of deformation oscillations, which is reasonably large for breaking, is developed at a relatively small pressure amplitude of the exciting acoustic wave, and subharmonics arise in the acoustic-emission spectrum. The condition of bubble break-up is obtained for a fast and slow start of the acoustic wave.

The results of investigation of cavitation erosion of lead in various places of a hydrodynamic-generator submerged jet are presented. Features of erosion caused by the effect of flow are established. It can both strengthen the erosion intensity and weaken it in dependence on the angle of incidence. The stratification of air bubbles under the action of pressure waves is possible in the flow under the interaction with the surface of objects. The flow can change the number of air bubbles participating in the cavitation near the surface. It can also influence the mechanical effect on the surface of the tested materials inducing their nonuniform deformation. All the factors listed affect the cavitation erosion complicating considerably the physics of the process.

To estimate the epicenter coordinates of the 2011 tsunami source from mareograms recorded by two stations, we use a rapid asymptotic–numerical procedure based on the Maslov canonical operator.

It is proposed to search for solutions to the equation of continuum equilibrium satisfying additionally the Beltrami tensor equation, which describes self-transformation of a solenoidal field and is well-known in hydrodynamics for the velocity vector field; however, it has apparently still not been considered for tensor fields. A series of localized stress distributions twisting the material continuum are obtained as well as the stress distribution in the form of periodic structures in the space caused by the regular distribution of incompatible plastic deformation in an elasto-plastic solid. The obtained solutions are not known in the theory of elasticity and represent a certain interest in connection with the description of defects in a solid.

It is shown analytically and confirmed by numerical results that the influence of the initial conditions for the problem of hydraulic fracturing decays over time.