Mathematical simulation of a twisted pseudoplastic fluid flow in a cylindrical channel

The results of investigations of a pseudoplastic fluid twisted flow in a cylindrical channel are presented. With increase in the shear stresses caused by the flow twisting, the effective viscosity decreases. As a result, in the axial part of the channel a zone of lower pressure is formed which, at smaller flow twisting, leads to the formation of the zone of backward flows.     

Charge Photogeneration in Few‐Layer MoS2

The 2D semiconductor MoS₂ in its mono‐ and few‐layer form is expected to have a significant exciton binding energy of several 100 meV, suggesting excitons as the primary photoexcited species. Nevertheless, even single layers show a strong photovoltaic effect and work as the active material in high sensitivity photodetectors, thus indicating efficient charge carrier photogeneration. Here, modulation spectroscopy in the sub‐ps and ms time scales is used to study the photoexcitation dynamics in few‐layer MoS₂. The results suggest that the primary photoexcitations are excitons that efficiently dissociate into charges with a characteristic time of 700 fs. Based on these findings, simple suggestions for the design of efficient MoS₂ photovoltaic and photodetector devices are made.     

Numerical study of the separation characteristics of a hydrocyclone under various conditions of loading of the solid phase

The separation processes in a hydrocyclone under various conditions of loading of the solid phase are numerically studied using the Navier-Stokes equations. The separation of particles in the event of their sudden injection or sudden termination of injection to the hydrocyclone is analyzed.     

Crack growth in the process of unstable brittle fracture

We suggest a model of the transition of a crack from stable to unstable propagation with subsequent growth in the supercritical state. By using the energy balance equation for propagating cracks, we estimate the specific surface energy and crack growth rate under the conditions of unstable propagation. Unstable propagation starts with a rate which is lower than the maximum crack growth rate in the material. The specific surface energy and kinetics of the crack undergoing unstable fracture depend both on the maximum crack growth rate in the material and on the initial rate υ₀ of its unstable propagation. The rate υ₀ is largely determined by the critical size of the crack (critical stresses). Blagonravov Institute of Mechanical Engineering, Russian Academy of Sciences, Moscow. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 32, No. 6, pp. 81–86, November–December, 1996.     

Corrigendum

Addendum: The stress field for a blunt crack in an anisotropic material     

Fracture toughness diagrams of a notched body

To describe fracture toughness diagrams of notched bodies, a model of the cohesion zone near the notch root and an averaging criterion of stresses in this zone were employed. The geometric stress concentration factor and biaxiality coefficient affect greatly the shape of fracture toughness diagram. The notch root critical stress intensity factor is a decreasing function of geometric stress concentration factor. __________ Translated from Problemy Prochnosti, No. 5, pp. 142–148, September–October, 2006. Report on International Conference “Dynamics, Strength, and Life of Machines and Structures” (1–4 November 2006, Kiev, Ukraine).