Vol 18, No 4 (2014)

We consider the Cauchy problem for the hyperbolic differential equation of the forth order with nonmultiple characteristics. We generalize this problem from the similar Cauchy problem for the hyperbolic differential equation of the third order with nonmultiple characteristics which solution was constructed as an analogue of D'Alembert formula. We obtain the regular solution of the Cauchy problem for the hyperbolic differential equation of the forth order with nonmultiple characteristics in an explicit form. This solution is also an analogue of D'Alembert formula. The existence and uniqueness theorem for the regular solution of the Cauchy problem for the hyperbolic differential equation of the forth order with nonmultiple characteristics is formulated as the result of the research. In the paper we consider the Cauchy problem for the system of the general hyperbolic differential equations of the forth order with nonmultiple characteristics.

Nonlocal problems for the second order hyperbolic model equation were studied in the characteristic area. The type and order of equations degenerate on the same line $y = 0$. Nonlocal condition is given by means of fractional integro-differentiation of arbitrary order on the boundary. Nonlocal condition connects fractional derivatives and integrals of the desired solution. For different values of order operators of fractional integro-differentiation within the boundary condition the unique solvability of the considered problems was proved or non-uniqueness of the solution was estimated.

The numerical solution of the static three-dimensional contact problem of the indentation of a rectangular stamp with a flat base in an elastic rough half-space in the presence of Coulomb friction and previously unknown adhesion and slip zones is obtained. Accounting for surface roughness in this problem is carried out based on the spherical model of microroughnesses by introducing the nonlinear terms describing surface microroughnesses crushing and shearing to the expression of relative displacement of the interacting bodies. The influence of the values of the friction coefficient and the parameters of the microscopic irregularities on the size and shape of the zone of adhesion and the distribution of the tangential contact stresses are analyzed. It is shown that the inclusion of surface microroughness shear forming roughness can lead to a substantial increase in the size of the zone of adhesion.

The boundary value problem of steady-state creep for thick-walled outer elliptic contour’s tube under internal pressure is considered. The approximate analytical solution of this problem for the state of plane deformation by the method of small parameter including the second approach is under construction. The hypothesis of incompressibility of material for creep strain is used. As a small parameter the value of flattening factor of the ellipse for external contour is used. Analysis of analytical solution is executed depending on the steady-state creep nonlinearity parameter and flattening factor of ellipse that is ratio of the difference of the semi-major and semi-minor axis to the semi-major axis which is outer radii of the unperturbed thick-walled tube. It is shown that with increasing of value of flattening factor to 0.1 of outer radii of tube tangential stresses in weakest section at θ = π/2 increase by 1.7-1.8 times. The results of computations are presented in tabular and graphic form.

The way of solution of the coupled boundary value problem of solid body deformation for the case of a plastically softening material is offered. The strain and stress fields obtained by the simulated undamaged construction behavior modeling under the action of fictitious forces are used as basic data for calculation. The equivalence of simulated undamaged medium strains and real medium strains is supposed. At each point of construction the damage parameter $\omega$ is calculated by means of constitutive relations of the endochronic plasticity theory. This damage parameter associates the components of the true stress tensor $\sigma_{ij}$ of simulated undamaged medium and the engineering stress tensor $\sigma^0_{ij}$ of real medium by $\sigma^0_{ij}=\sigma_{ij}/(1+\omega)$. Using the tensor $\sigma^0_{ij}$ we can calculate the generalized forces of real construction. The problems of tension of the plates weakened with centric circular hole and semicircular notches are solved and the necessary experiments are conducted. The strain and true stress fields are obtained by numerical calculation at the finite element analysis software and are used for the engineering stress of real construction computation according to the foregoing expression. Softening plasticity domains are plotted. It is found that at the moment before failure the stage of post critical deformation is implementing in the region of stress concentration, although the curve “total displacement - axial force” corresponds to the stage of plastic hardening.

The uniqueness of a solution in the small sense (in the sense of lack of infinitely close solution) is proved for the boundary-value problem of equallystressed reinforcing metal composite plates in conditions of steady creep of materials of all phases of the composition, when in addition to static and kinematic boundary conditions and boundary conditions for the densities of the reinforcement, which is natural in such problems, on the contour of the plates an additional boundary conditions are specified for angles of reinforcement. In a large sense (in the sense of significant differences solution) this problem can have multiple, but not infinitely close, alternative solutions because of the nonlinearity of the static boundary conditions and equallystressed of reinforcement. The study of the problem of uniqueness of the solution of this problem is necessary when examining the issue of correctness setting of problems of equally-stressed of reinforcement.

The paper is on the problem of classification an asteroid as potentially hazardous (PHA), namely the estimation of the MOID parameter. Minimum Orbital Intersection Distance describes the minimal distance between two confocal heliocentric orbits. Analytical, numerical and hybrid methods used for the MOID estimation are reviewed. A brief description of the K. V. Kholshevnikov and G. F. Gronchi analytical methods, which are considered to be classical, is given. The task of calculating the MOID parameter for a large number of asteroids (more than 10,000) with a maximum calculating speed and the ability to parallelize the process is set. A numerical method based on geometrical considerations concerning the location of the bodies on their orbits is proposed. Let us consider two bodies A and E. Since only the minimum distance between two orbits is required, the information on the actual position of the bodies on their orbits is insignificant. The idea is to calculate one full revolution of the body A. For each position of body A the corresponding position of the body E is calculated under the following assumption. Consider a plane P , comprising the body A and the Sun. Therefore, plane P is perpendicular to the orbital plane of the body E. Of the two points at which the plane P intersects the orbit of the body E, E is considered to be at the point that is the nearest the body A. Thus, the position of the body E will depend on the position of the body A. As a result, from the geometric assumptions on the triangle formed by the Sun and two bodies, the distance between A and E is calculated. When one complete revolution of the body A with a certain step is calculated, we receive a set of the distances between two orbits, from which we can identify the areas of the local minima of the discrete representation of the distance function (the distance between the orbits of A and E). Then, the procedure of tuning is carried out to verify and precise the values of local minima of discrete representation of the distance function. As a result, the smallest value of the local minima is considered to be the estimation of the Minimum Orbital Intersection Distance (MOID) takes. Pros of the suggested method are as follows: high speed and adjustable calculation accuracy, the suitability to the use of parallel computing. Comparative tests of the described method were carried out. The results received are consistent with the classical G. F. Gronchi method.

A quantum path integral was transformed into the real form using a complex representation of the time. Such procedure gives the possibility to specify measures for the sets of the virtual paths in continual integrals determining amplitudes of quantum states transitions. The transition amplitude is a real function of the complex time modulus. Negative time values correspond to the reverse sequence of events. The quantum evolution description in form of the virtual paths mechanical motion does not depend on the sign of the time, due to the reversibility of the classical mechanics laws. This allows to consider the negative half of the imaginary axis of the time for the path integral measure determination. In this case this integral has the form of Wiener's integral having the well-known measure. As the wave function collapse is irreversible effect, the causal chain of events cannot be changed. Thus, to describe the collapse the transformation of quantum path integrals have to be performed in upper half plane of the complex time. It is shown that the Wiener measure for the real continual integral can be continued analytically on this actual range of the complex time. This allows to use the quantum path integral for any actual range of the complex time.