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The work presented is devoted to the axisymmetric contact problems on the interaction of a rigid stamp and an elastic layer fixed on a porous elastic half-space by using the Cowin–Nunziato model. It is assumed that the stamp basis has a flat or parabolic shape and friction is absent in the contact zone. With the help of the Hankel integral transform, the problems stated are reduced to solving integral equations for the unknown contact stress by using the collocation method. The values of contact stresses and the contact area in the case of a parabolic stamp are found. The normal stresses on the interface between the elastic layer and the poroelastic half-space are investigated. The relationship between the force acting on the stamp and the corresponding displacement, which is one of the main characteristics in determining the mechanical parameters of the material by the indentation method, is investigated. A comparative analysis of the values found for various parameters of the elastic layer and the poroelastic base is carried out. The numerical results are presented in a table and in the form of graphs.

In this article, we analyze axisymmetric contact problems on the interaction of a rigid stamp with a poroelastic layer using the equations of the Cowin–Nunziato theory of poroelastic bodies. It is assumed that the stamp base has a flat or parabolic shape and there is no friction in the contact zone. The posed problems are reduced to integral equations, the main kernel part of which is the delta function, by means of special function via which the contact stresses are expressed. Using a special approximation of the integral equation kernel transform, its asymptotic solution is constructed for the case of relatively large layer thicknesses. This approach to solving integral equations of contact problems was proposed by I.I. Vorovich and was further developed by his students. Expressions for the contact stresses and the contact area in the case of a parabolic stamp are obtained in a simple analytical form. Also, a relation between the force acting on the stamp and its displacement that is one of the main characteristics in determining the mechanical parameters of a material by the indentation method is found in terms of elementary expressions. A comparative analysis of the investigated quantities for various values ​​of the parameters of porosity and layer thickness is carried out.

The axially symmetric problem of a stamp excitation of torsional oscillations in a cylindrical waveguide with periodically changing mechanical properties along the longitudinal coordinate has been studied. A section of waveguide, corresponding to the minimal period of change in mechanical properties, can consist of any number of homogeneous regions (finite cylinders) with a different length and with various elastic constants. The method, related to the construction of the special “transition operator”, which allows finding the values of the displacement vector and stress tensors on one cross-section of a waveguide by their values on another. The distance between waveguide sections equals the value of the minimal period of changing properties of the waveguide. Relations for calculating the eigenvalues of the transition operator are obtained. The study of these eigenvalues allows defining the range of frequencies when both damping and continuous oscillations can propagate in the waveguide. Contact strains under a stamp are determined for relatively large radii of the cylinder.

The paper presents numerical and experimental burst pressure evaluation of the gas seamless hot-rolled steel pipe. The main goal was to estimate mechanical toughness of pipe wrapped with composite sleeve and verify selected sleeve thickness. The authors used a nonlinear explicit FE code with constitutive models which allows for steel and composite structure failure modelling. Thanks to the achieved numerical and analytical results it was possible to perform the comparison with data received from a capacity test and good correlation between the results were obtained. Additionally, the conducted analyses revealed that local reduction of pipe wall thickness from 6 mm to 2.4 mm due to corrosion defect can reduce high pressure resistance by about 40%. Finally, pipe repaired by a fibre glass sleeve with epoxy resin with 6 mm thickness turned out more resistant than an original steel pipe considering burst pressure.

Serviceability of metal-polymeric "dry-friction" sliding bearings depends on many parameters, including the rotational speed, friction coefficient, thermal and mechanical properties of the bearing system and, as a result, the value of contact temperature. The objective of this study is to develop a computational model for the metallic-polymer bearing, determination on the basis of this model temperature distribution, equivalent and contact stresses for elements of the bearing arrangement and selection of the optimal parameters for the bearing system to achieve thermal balance. Static problem for the combined sliding bearing with the account of heat generation due to friction has been studied in [1]; the dynamic thermoelastic problem of the shaft rotation in a single and double layer bronze bearings were investigated in [2, 3].

The serviceability of polymer dry sliding bearings is governed by a number of parameters, such as the rotational velocity of the shaft, the friction coefficient, еру thermal and mechanical properties of bearing members, and hence, the resulting contact temperatures. This work was aimed at developing a calculation model of the operation of a two-layer polymer dry sliding bearing, determining the temperatures distributions and the equivalent and contact stresses in bearing members, and choosing the optimum parameters of the bearing system for which heat balance is achieved.