Well-posedness and energy decay of swelling porous elastic soils with a second sound and delay term

In this paper we consider a one-dimensional swelling porous-elastic system with second sound and delay term acting on the porous equation. Under suitable assumptions on the weight of delay, we establish the well-posedness of the system by using semigroup theory and we prove that the unique dissipation due to the delay time is strong enough to exponentially stabilize the system when the speeds of wave propagation are equal.

Asymptotic research of deformations and stresses of the ring that sustains the seam of elliptic bottom and conic shell

In the paper, we consider stress-deformed state of elastic system that consists of the elliptic bottom, the ring, and the conic shell. The ring is under arbitrary load, which acts in its plane.On the base of the principal differential dependencies of design of the planar circular ring, we obtain the expressions for tensions, momentum, and the angle of rotation of lateral section.

Plasticity of the gastrocnemius elastic system in response to decreased work and power demand during growth

Elastic energy storage and release can enhance performance that would otherwise be limited by the force-velocity constraints of muscle. While functional influence of a biological spring depends on tuning between components of an elastic system (the muscle, spring, driven mass, and lever system), we do not know whether elastic systems systematically adapt to functional demand. To test whether altering work and power generation during maturation alters the morphology of an elastic system, we prevented growing guinea fowl (Numida Meleagris) from jumping. At maturity, we compared the jump performance of our treatment group to that of controls and measured the morphology of the gastrocnemius elastic system. We found that restricted birds jumped with lower jump power and work, yet there were no significant between-group differences in the components of the elastic system. Further, subject-specific models revealed no difference in energy storage capacity between groups, though energy storage was most sensitive to variations in muscle properties (most significantly operating length and least dependent on tendon stiffness). We conclude that the gastrocnemius elastic system in the guinea fowl displays little to no plastic response to decreased demand during growth and hypothesize that neural plasticity may explain performance variation.

Use of electromechanical analogies in the construction and calculation of a simulation model of the process of torsional oscillations of the shaft line of an internal combustion engine

The purpose of the article is to substantiate the possibility of using electromechanical analogies in the construction and calculation of parameters of the simulation model of the process of torsional oscillations of the internal combustion engine shaft, which will allow to move from mechanical models of shafts to their electrical counterparts. Results of the research. The article clarifies the relationship between phenomena occurring in mechanical and electrical systems, mechanical and electrical analogues are established, namely force is considered as electromotive force or voltage, velocity as current, moment of inertia as inductance, spring flexibility as capacitance, coefficient friction as electrical resistance, and the kinematic scheme of the shaft line is presented in the form of a diagram of a reactive bipolar, the parameters of which are determined during analytical calculations of the kinematic scheme of the elastic system. The concept of dynamic stiffness is introduced, which is similar to the concept of reactive resistance of a bipolar. The initial data for the calculation of a linear system in which it is assumed that the pliability of the shock absorber is zero. Conclusions. According to the results of the analogies, the parameters of the simulation model were obtained. The calculation of the elastic system using the method of electromechanical analogies allowed to build a simulation model of the shaft line of an internal combustion engine.

INFLUENCE OF THE GEOMETRIC CHARACTERISTICS OF THE DISCONTINUOUS PROFILE WORKING SURFACES OF ABRASIVE WHEELS FOR PRECISION AND TEMPERATURE WHEN GRINDING

Grinding is the most common finishing method for hardened steel parts. Grinding is accompanied by a large heat release in the cutting area, under the influence of which structural changes appear in the thin surface of the processed parts, tensile stress and even microcracks, which significantly reduce the operational reliability of machines that include these parts. The use of abrasive wheels with an intermittent working surface makes it possible to reduce the temperature in the area of contact of abrasive grains with the material of the workpiece and, as a consequence, stabilize the quality of the surface layer of the workpieces. High-frequency vibrations in the elastic system of the machine, accompanying the work of an intermittent wheel, are a positive factor that reduces the energy consumption of the grinding process. However, under certain conditions of dynamic interaction of the tool with the workpiece, parametric resonance may occur, which worsens the geometric and physical-mechanical parameters of the quality of the surface layer of the processed part. The aim of the work is to realize the possibility of predicting the quality parameters of the surface layer of parts during intermittent grinding by studying the influence of the design features of the macrotopography of the working surface of abrasive wheels and processing modes on the nature of the dynamic interaction of the tool with the workpiece and the heat stress in the cutting area. It was found that the parametric vibrations of the elastic system of the machine tool can be shifted to a more stable area, due to an increase in the number of interruptions of the working surface of the abrasive wheel with a constant ratio of the length of the protrusions and depressions. The increase in the number of breaks on the wheel also contributes to a decrease in temperature in the cutting area. It was found that to maintain the stable operation of the elastic system of the machine, it is necessary to reduce the number of cavities on the grinding wheel with an increase in the cutting speed. However, both of these actions are accompanied by an increase in the heat stress of the grinding process. It has been experimentally established that for ordinary (pendulum) grinding, it is possible to achieve an increase in processing productivity by increasing the speed of the longitudinal movement of the table.