Ignition of gas suspensions of metallic powders in reflected shock waves

Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 25, No. 2, pp. 67–74, March–April, 1989.     

Certain effects of biaxial elastoplastic deformation of a plate with a crack

Elastoplastic deformation of a circle with a center crack with radial displacements distributed according to an elliptical rule specified on its boundary is considered. The Dugdale model of a crack is used. The numerical and approximate analytical solutions obtained are compared with one another. A relationship of crack opening and size of the plastic area at its tip to the parameter of biaxial loading, as which is used the ratio of the displacements on the main axes of deformation of the plate, is revealed. The possibiity of stable crack growth is established.Translated from Problemy Prochnosti, No. 6, pp. 20–27, June, 1990.     

The structure of lubricating layers appearing during friction in the presence of additives of mineral friction modifiers

Investigation of the structural features of the third body appearing with the help of mineral friction modifiers reveals that the crystalline phase in their composition promotes their wear resistance during running-in. It is confirmed that such additives permit metallic surfaces to run dry. This effect is due to the formation of a two-level structure on the rubbing surfaces. This structure is a mineral skeleton with a developed surface and a layer made up of the products of tribopilymerization of the lubricating material. Antifriction polymers and composite materials on their base behave like most tribosystems manifesting selective transfer and their friction surfaces acquire multilayered antifriction coatings.     

Kinetic model of mutual effect of the components on the viscosity of binary mixtures

A kinetic model describing the temperature dependence of the viscous flow of multicomponent liquids over the whole range of compositions is suggested. It takes into account the mutual influence of component molecules—either increasing or decreasing the activation energy of viscous jump of each other, which formally is equivalent to catalysis. The quantitative possibilities of the model are shown using liquid binary systems characterized by strong intermolecular interactions.     

Effect of riblets on the streaky structures excited by free stream tip vortices in boundary layer

In this study, experimental investigations were made regarding the effect of riblets on the streak instability in boundary layer. The streak instability is now regarded as a major source of the self-regeneration mechanism for the hairpin type coherent structures in turbulent boundary layer flow. Thus, it is important to control the instability to suppress the drag-inducing vortical structure in terms of drag reduction. Toward enhancing the measurement accuracy and spatial resolution, an enlarged version of riblets was applied to a streak which was artificially induced by a microwing in a laminar boundary layer. It is found that the riblets have attenuation effect on the streak instability, i.e., to reduce the spanwise velocity gradient of the quasi-streamwise streak in boundary layer.     

Population of transition states of triboactivated chemical processes

The population of transition states of friction-induced chemical processes and similar thermo-induced reactions is analyzed. Friction is shown to be a unique natural phenomenon that involves the occurrence of highly inverse transition states of chemical interaction between contact material particles, as opposed to thermally populated transition states analogous in terms of the energy level of the reactions. It is found that in evaluating the population of transition states of mechano- and thermoactivated reactions, the specific chemical interactions do not matter and only the energies of the transition states of the thermo- and mechanoactivated processes are of importance.