Vol 64, No 9 (2019)

The static bending and longitudinal stability of nanowires under pressure in a liquid or gas are considered. Two surface effects are taken into account. The first effect is induced by the difference in the elastic properties of a thin surface layer and the bulk of the material. The effective tensile and flexural stiffness can be higher or lower than the conventional stiffness depending on the material. The second effect is due to the action of overpressure on the circular lateral surface of the wire and the difference in the areas of the convex and concave sides of the surface arising under bending. This effect manifests itself the more strongly, the greater the ratio of pressure to the modulus of elasticity of the material and the wire length to its diameter. These effects are determined by dimensionless parameters. It has been established that a buckling of wire may occur under the action of the second effect. A possible method for determining the dimensionless parameter, which determines the differences in the elastic properties of a thin layer near the surface and the bulk material, is proposed.

The observed occurrence of nano- and microcrystals without faceting in low-temperature processes of their formation may be due to the nonclassical mechanism of crystal growth by particle aggregation and oriented attachment growth.

It has been established experimentally that an change in temperature leads to a structurally induced increase in the lubricity of liquid crystal nanomaterials due to cholesterol phase transformations. It has been shown that the minimum values of the friction coefficient almost coincide with the peak values of the dynamic viscosity within this temperature range, thereby cumulatively arguing for the ordered state of liquid crystal cholesterol structures at these temperatures. As a result, it is possible to presume the formation of helically coiled layers of liquid crystal cholesterol molecules with a high antifriction effect within this temperature range in the friction zone. It is also observed that the thickness of liquid crystal cholesterol films appearing under friction reacts sensitively to the temperature changes in the zone of contact with discoloration and energy losses.

For the first time, the equations of aeroelastic stability of a composite cylindrical shell of linearly varying thickness are obtained on the basis of the bending theory of orthotropic shells under loading with axial forces and supersonic gas flow. The solution to the equations is sought in the form of trigonometric series along the axial coordinate. The problem is reduced to an infinite system of algebraic equations by the Bubnov–Galerkin method. The characteristic equation obtained is approximated by the Lagrange polynomial, the stability of which is investigated using the Routh–Hurwitz criterion. By a numerical example, the effect of the thickness gradient, structural damping, and axial force on the critical velocity when flow by a supersonic gas around а shell of linearly varying thickness is shown. The refinement of the results of calculations carried out with the model developed amounted to almost 35% for the critical velocities as compared to those found from the model for a shell with an average thickness, which evidences the urgency of the problem solved for weight perfection of aircrafts. The approach proposed significantly extends the range of problems to be solved and allows calculating the aeroelastic stability of orthotropic cylindrical shells of linearly varying thickness in the flow around by the supersonic gas flow.

A model of preparation of an initial ocean earthquake is created for vertical impacts on the ocean layer and lithospheric plates, and the conditions of tsunami generation are found.