A nonlinear evolution equation describing the shape of a thin plastic layer compressed by rigid parallel planes is derived. The material of the layer and the contact friction are anisotropic. The similarity solutions and the classes of self-similar solutions are discussed. The large-time asymptotics is analyzed. The instability problem is considered for the spreading process for a strip.

A new dimensionless parameter is chosen in the exact solution of the problem under study. Depending on this parameter, the critical flutter velocity can range from instantaneous modular to maximum modular.

A self-similar solution to the problem of flow of a plastically anisotropic layer between parallel planes in a region with a sink is constructed. The problem can be reduced to solving an unstudied Riccati equation with a small parameter. The perturbation method is used to find two different solutions expressed in terms of quadratures.

We present a survey of the main results and scientific ideas due to the 20th century prominent scientist Aleksey Antonovich Il’yushin, which can be regarded today, at his hundredth birthday anniversary, as his scientific heritage. The survey material is arranged (mainly, chronologically) in the key directions of Il’yushin’s activities such as the theory of viscoplastic flow, hydrodynamic stability, dynamics of deformable media, supersonic aerodynamics and related flatter problems, theory of elastoplastic processes, theory of plastic flow, thermoviscoelasticity and thermodynamics, strength of polymer bodies and structures, general theory of constitutive relations in classical continuum mechanics, and nonclassical models of continuum.

The experimental and numerical study of the strain state is conducted for the spire of the Moscow University main building. The experimental data are in good agreement with the numerical results obtained according to a finite-element beam model of the spire.

The stability of an elastic plate and an elastic panel placed in a supersonic gas flow is studied in a nonlinear formulation. The gas velocity vector is directed at a small angle to them. The critical velocity of the flow is determined for various parameter values. The numerical results obtained are compared.

Представлен обзор основных результатов и научных идей выдающегося ученого XX века Алексея Антоновича Ильюшина, которые сейчас, в дни его столетнего юбилея, можно трактовать как научное наследие. Материал обзора структурирован (преимущественно хронологически) по ключевым направлениям деятельности А.А. Ильюшина: теория вязкопластического течения, гидродинамическая устойчивость, динамика деформируемых сред, сверхзвуковая аэродинамика и связанные с этим проблемы флаттера, теория упругопластических процессов, теория пластического течения, термовязкоупругость и термодинамика, прочность полимерных тел и конструкций, общая теория определяющих соотношений в классической механике сплошной среды, а также неклассические модели сплошных сред

The formulation of the strip flutter problem based on a refined expression for the excess pressure is proposed. Two cases are considered: almost transverse and almost longitudinal flow past the strip. In the first case, an exact expression for the excess pressure, fundamentally different from the formulas of piston theory, which leads to novel, little studied eigenvalue problems is obtained. In the second case, an exact expression is obtained for the flow potential and, for purely longitudinal flow, for the excess pressure also. It is shown that for purely longitudinal flow at high supersonic velocities the critical flutter velocity is equal to the phase velocity of perturbation propagation along the strip, which coincides with the results of piston theory.

The viscoplastic flow of a thin strip of material in a superplasticity state between rigid, converging parallel planes (an analogue of Prandtl's problem) is investigated. An analytical quadrature solution of the problem is constructed, asymptotically precise in the same sense as Prandtl's solution. Special cases are considered where the solution (including an approximate solution) is written out fully. The effects of superplasticity are determined.

The well-known piston theory formula for the excess aerodynamic pressure is used in the majority of works devoted to the panel flutter of shells. In this paper a refined expression for the excess pressure is proposed to take into account the irregularity of undisturbed flow parameters. The case of moderate supersonic velocities is studied in detail. The critical velocity problem is reduced to a new eigenproblem in the panel flutter theory.

It is commonly assumed that the theory based on the Kirchhoff hypotheses describes the properties inherent in the wave processes occurring in shells filled with fluids. But there are several new effects that cannot be described by this theory (in particular, the appearance of new types of waves). In this paper, we present a linearized description of axisymmetric wave motion of a perfect incompressible fluid in a multilayered cylindrical shell with allowance for shear strain; the shell is assumed to be infinite and simply supported. This description is aimed at finding new mechanical effects and hence at estimating the influence of the multiple layers and the shear strain on the wave characteristics. In a sense, it generalizes and develops well-known studies of this type.Practice necessitates deriving equations constructed under the assumption that the physical and mechanical properties of the shell material are inhomogeneous along the thickness direction or the shell is multilayered; the development of refined theories (compared with the classical theory based on the Kirchhoff-Love straight normal hypothesis) is also inspired by practice. This is primarily related to the fact that multilayered thin-walled shells made of composite materials are used in various fields of technology. It is of interest to note that, as a result of long evolution, the phenomenon of being multilayered also predominates in living organisms. For example, this is typical of big blood vessels [1] (arteries and veins).In [2], on the basis of a three-dimensional variational principle of mixed type, the equations of motion and physical relations for elastic anisotropic shells rigidly inhomogeneous in the thickness direction are derived under the assumptions of the theory of thin shells and with shear strains taken into account. It is also noted that the case of multilayered shells can be modeled by introducing functions with integrable singularities.When studying wave propagation in deformable shells containing fluid, hydroelasticity problems arise; the solution of such problems is of both theoretical and practical importance. Of topical problems in this field, problems related to pulsating blood flow in big blood vessels [3] (the theory of pulse waves) are worth mentioning. The incentive for such studies is that they can help to understand the normal operation of the blood circulatory system, predict its reaction to variations, and propose methods for artificial intervention. Thus, diagnostics, surgery, and prosthesis are closely related to biomechanics. But the applied value of such problems is not bounded by their applications in hemodynamics. They are also very important in technology because of the wide use of systems of fluid and gas transportation through pipelines with corrosion-resistant coating.

The theory of the flow of a thin layer of plastic material over surfaces developed by Il’yushin is extended to the case of an anisotropic ideally plastic material and anisotropic flow on the surface. Particular attention is given to determining the contact pressure. Two methods are proposed for solving this problem: a variational method and reduction to a Cauchy problem. The effect of anisotropy is revealed using specific examples.

The flutter of a rectangular plate with an arbitrary direction of the velocity vector relative to the plate side is studied. A numerical no-saturation algorithm is constructed to solve the eigenvalue problem. Calculation results for the critical flutter velocity and corresponding eigenmodes are given.