Volga State University of Water Transport

About: Volga State University of Water Transport is a education organization based out in Nizhny Novgorod, Russia. It is known for research contribution in the topics: Attractor & Creep. The organization has 71 authors who have published 75 publications receiving 224 citations.

State Equations of Unsteady Creep under Complex Loading

Abstract: A mathematical model describing the unsteady creep of metals under complex loading is proposed. The results of numerical simulation of creep of St.304 steel in complex regimes of block multiaxial cyclic deformation are given. The numerical calculation results obtained are compared with the data of full-scale experiments. Creep is simulated in complex deformation processes accompanied by the rotation of main regions of stress, strain, and creep strain tensors.

Regular and Chaotic Transition to Synchrony in a Star Configuration of Phase Oscillators

Abstract: We consider two finite-dimensional models of the phase oscillators in the case of star configuration of coupling. Both systems of equations are reduced to a nonlinearly coupled system of pendulum equations. We prove that the transition from synchronous to asynchronous oscillations occurs via bifurcation of saddle-node equilibrium. In this connection the asynchronous regime can be partially synchronous rotations. We find that the reverse transition from asynchronous to synchronous regime occurs via bifurcation of homoclinic orbit both of the saddle equilibrium point and of the saddle periodic orbit. In the case of homoclinic loop of the saddle point the synchrony appears only from asynchronous mode without partially synchronized rotations. In the case of the homoclinic curve of the saddle periodic orbit the system undergoes a chaotic rotation regime which results in a random return to synchrony.

Increasing the Efficiency of a Diesel-Generator Power Plant

Abstract: A variant of a diesel generator power plant consisting of a conventional diesel-generator set and a variable-speed diesel-generator set is considered. A transformer-free topology of the power circuit of the variable-speed diesel-generator set is proposed on the basis of an active voltage rectifier, a mains inverter, and a buffer energy storage device. The block diagram for controlling a diesel-generator power plant is developed. The autonomous and parallel operation modes of the diesel-generator sets are considered. A block diagram of the speed controller on the basis of intelligent controls is proposed for the variable-speed diesel generator set. The simulation model of the diesel-generator power plant is implemented in the MATLAB/Simulink suite. Results of simulation modeling of the power plant’s dynamic operational modes under load switching are presented. The variable-speed diesel-generator set is shown to provide energy-efficient operation of the power plant and compliance with the requirements for the quality of generated electricity when the internal combustion engine runs at low energy efficient rotation speeds in the shared load mode.

Constitutive Relations of the Mechanics of a Damaged Medium for Evaluating the Creep-Rupture Strength of Structural Alloys

Abstract: The main regularities of the degradation of structural materials (metals and alloys) resulting in a decrease in creep-rupture strength were investigated. A mathematical model describing the viscoplastic deformation and damage accumulation in polycrystalline structural alloys in creep was developed using the equations of the mechanics of damaged media. The paper presents the results of experimental studies of the short-term creep of 12Kh18N9 steel and VZh-159 high-temperature alloy at constant temperature and different stresses set in the samples and the results of experimental studies of creep recovery in some structural steels. Deformation and damage accumulation were studied numerically and the results were compared with the data of full-scale experiments.