Improvement of nonmonotone deformation technology in plastic metal working

The production of semi-finished products made of refractory metals is considered. The advantage of parts production using combination of two types of straining with change in the straining direction: direct extrusion and equal-channel pressing is shown. The experimental investigation data of pure and simple shear for the semi-finished products processing made of tungsten and molybdenum are presented. Requirements for the tool providing diagonal flow and angular straining are formulated based on the analysis of the stress-strain state of the processes of axial symmetric extrusion and simple shear of plastically inhomogeneous body. Effectiveness evaluation of the combination of various types of fixtures and the rational sequence for using of diagonal flow and angular pressing is given. Experimental devices for practical application of the proposed technology are developed.

On modeling bodies with delaminating coatings taking into account the fields of prestresses

The paper presents a model of steady-state oscillations of an inhomogeneous body with a prestressed exfoliating coating based on a general linearized statement of the problem of the motion of a prestressed-strained elastic body. On its basis, the statement of the problem of oscillations of an inhomogeneous strip consisting of a substrate and a prestressed coating is formulated, between which there is a delamination in a certain region. Steady oscillations are caused by a load applied to the upper boundary of the coating. To calculate the oscillations of the two-dimensional structure under consideration, the Fourier transform in the longitudinal coordinate was used and the original problem was reduced to solving a number of auxiliary boundary value problems with respect to transformants of the desired functions. From the conditions that the stress functions vanish (the cover is modeled as a mathematical section) of the substrate and the coating, the operator relations are constructed in the area of delamination to calculate the opening functions. The kernels of these operator relations are singular and are integrals over an infinite interval. A study was made of the behavior of their integrands at infinity, on the basis of which special approaches were used to calculate the kernels. As a result of solving the obtained hypersingular equations with difference kernels, for which the collocation method is used, the originals of the disclosure functions are constructed. Using a similar approach for inverting the Fourier transformations, we constructed relations to calculate the originals of the displacement functions at the upper boundary of the coverage. Based on the computational experiments, an analysis is made of the influence of the initial geometric and mechanical parameters of the substrate and coating on the values of the disclosure functions in the delamination region and the displacement functions at the upper boundary of the layer. The influence of the prestress level on the amplitude-frequency characteristics (AFC) was also investigated. It was found that the most significant effect on the frequency response is in the vicinity of the frequencies of the thick resonances. Based on the information on the displacement fields, it is possible to construct schemes for identifying delamination characteristics.

Effective Deformations of Peristatic Random Structure Bar Subjected to Inhomogeneous Body-Forces

A statistically homogeneous random bar with the bond-based peridynamic properties of constituents is considered for a static case. Estimation of effective properties for the random structure peridynamic composites can be considered as a straightforward generalisation of the corresponding classical results for locally elastic composites which were obtained for both statistically homogeneous composites and homogeneous remote loading. In such a case the effective properties of both the peri-dynamic composites and locally elastic ones are described by a constant tensor of local stifness. However, even for locally elastic composites subjected to inhomogeneous loading, the effective deformations are described by a nonlocal (either the differential or integral) operator relaiting a statistical average of stresses in the point with a statistical average of strains in the vicinity of the point being considered. On the other hand, to the best authors’ knowledge, there are no academic publications analyzing the mentioned effective deformations of locally elastic composites due to prescribed inhomogeneous body-forces. Thus, the current paper deducated to the estimation of effective deformatiobs of 1D statistically homogeneous peridynamic composite bar for the prescribed self equilibrated body-forces has no known locally elastic counterpart. A sabsequent simplification is described by the dilute approximation method assuming coinsidence of the effective field (acting on the inclusions) with the applied field when interaction of inclusions is neglegible. The method is based on estimation of a perturbator introduced by one inclusion that is, in fact, the solutions of the basic problem for one inclusion inside the infinite peristatic matrix subjected to the body-force. The statistical averages of both the displacement and stresses are estimated by summation of these perturbators for all possible location of inclusions.