Влияние микротрещин на коэффициент Пуассона при пластическом деформировании аустенитной стали

We researched the influence of damage accumulation on the Poisson's ratio measured by echo-pulse acoustic method during plastic deformation of 12Kh18N10T steel. On the basis of the obtained experimental data we calculated the partial contributions to the change in the Poisson's ratio of damage accumulation and separation of the strain induced martensite phase. The characteristics of stable cracks forming near strain martensite particles at small degrees of plastic strain have been analyzed by computer simulation. The theoretical dependence of the change in the Poisson's ratio due to crack formation during plastic deformation has been constructed. A good agreement between the experimental data and theoretical calculations has been obtained.

About the features of the least squares method with linearization when determining nonlinear parameters of functional dependencies

The features of approximation of empirical data by functional dependence with nonlinear parameters using the two-stage least squares method are considered in this paper. A method of simplified parameter estimation by constructing a new expression that depends on the parameters in a linear way is described. To obtain the final solution, the least squares estimation of the main dependence linearized in terms of parameters is performed. The influence of various forms of noise imposed on the theoretical dependence on the approximations is modeled.

Quality estimation of the nozzle spray by measuring the brightness of the reflected light

This paper presents the results of the laboratory and numerical experiments performed to measure the sizes of transparent liquid droplets sprayed in air. The results of the laboratory experiments were mainly obtained using the Glare Point Technique (GPT) which gave information about the droplet size and the brightness of the light reflected by drops. The relationship between the brightness of the light reflected from the surface of droplets and their sizes was analyzed. Theoretically, the brightness of light scattered by a single spherical drop is proportional to the drop surface area and, accordingly, to the square of the drop diameter. It has been observed experimentally and verified numerically that the theoretical dependence obtained is relevant only for the brightest droplets because of nonuniform illumination. The results of the numerical experiments with a random sample of drops indicated the dependence of the total brightness of reflected light on the effective droplet size. It is shown that, for a fixed total volume, the total brightness of light reflected by drops is proportional to the droplet Sauter mean diameter.

DESCRIPTION OF THE PARAMETERS OF THE ELLIPSE NEEDLE DISC OF THE SOIL PROCESSING TOOL

Due to the well-known advantages, rotary tillage implements are widely used in the cultivation of many agricultural crops. Structurally, the working units of rotary implements are located (installed) on the frame, as a rule, sequentially one after the other. This reduces the maneuverability of the tillage unit, increases the material consumption of the implement and the energy consumption of the technological operation. In the rotary tillage tool developed at Kazan State Agrarian University for pre-sowing soil cultivation, these disadvantages are eliminated by installing a spiral-screw working unit and a section of active ellipsoidal needle disks on the frame coaxially. The research was carried out in order to determine and substantiate the design parameters of the elliptical needle disk. A theoretical dependence is obtained to substantiate the angle α of inclination of the major axis of the ellipsoid disk to the axis of rotation. It was revealed that its rational value must correspond to the condition: α> 44°…62°. An expression for determining the number of needles on a disk is given. The calculation carried out with a disk diameter D= 0.4 m, an angle α= 65 °, an indicator of a kinematic mode λ= 2, a mulching depth a= 0.04 m, a ridging h= 0.004 m showed that a rational number of needles per disc k= 16. Analytically, a theoretical expression for determining the angle of inclination of the needles to the axis of rotation has been derived. The calculation performed at α= 65 ° revealed that the first needle is inclined to the axis of rotation at a minimum angle jmin= 65 °, the fifth and thirteenth needles are inclined to the axis of rotation at an angle of 90 °, the ninth needle is inclined to the axis of rotation at a maximum angle jmax= 115 °. Also obtained are theoretical dependences for determining the angle of attachment of the needles on the hub and the length of the needles along the entire perimeter of the disk. The calculation showed that each needle is fixed on the disc hub at its calculated angle of inclination, equal to 29.0°...32.6°, and the length of the needles along the perimeter of the hub varies within 0.1372 ... 0.1503 m

Theoretical dependence of the strength of a plasma coating taking into account the mutual thermal effect of the sprayed particles

Перспективным способом восстановления изношенных деталей является газоплазменное напыление, позволяющее получать заданные эксплуатационные свойства поверхности. В статье теоретически вычислена вероятность взаимодействия напыляемых частиц в период их тепловой активности, зависящая от единственного параметра равного произведению числа напыленных частиц и квадрата отношения радиуса диска частицы на подложке к радиусу пятна напыления. Получено аналитическое выражение прочности плазменного покрытия на отрыв от параметров процесса напыления с учетом взаимного теплового влияния напыляемых частиц от единственного безразмерного параметра. Безразмерный параметр равен отношению произведения времени термической активности частиц, массового расхода, коэффициента прилипания, квадрата радиуса диска частицы на подложке к произведению массы частицы и квадрата радиуса пятна напыления. Gas-plasma spraying is a promising method for the restoration of worn-out parts, which makes it possible to obtain the performance properties of the surface. In the article the probability of interaction of the sprayed particles during the period of their thermal activity is theoretically calculated, depending on a single parameter equal to the product of the number of sprayed particles and the square the ratio of the radius of the disk of the particle on the substrate to the radius of the deposition spot. An analytical expression is obtained for the separation strength of a plasma coating from the parameters of the spraying process, taking into account the mutual thermal effect of the sprayed particles from a single dimensionless parameter. The dimensionless parameter is equal to the ratio of the product of the time of thermal activity of particles, mass flow rate, adhesion coefficient, square of the radius of the disk of the particle on the substrate to the product of the mass of the particle and the square of the radius of the spray spot.

Justification of the diameter of the nozzle holes of the hollow frame for flushing the fil-ter rotor of the centrifuge

The article presents a theoretical justification for the diameter of the nozzle holes of a hollow frame installed inside the filter rotor of a centrifuge. A theoretical dependence on the definition of this diameter is obtained. When determining the diameter, it was found that it is necessary to take into account the number of nozzles located on the hollow frame. This will ensure uniform and high-quality flushing of the filter rotor of the centrifuge.

Research on Determination of Water Diffusion Coefficient in Single Particles of Wood Biomass Dried Using Convective Drying Method

Determination of the mass diffusion coefficient for dried, inhomogeneous material is difficult as it depends on the drying agent temperature and the moisture content and physical structure of the material. The paper presents a method for efficient determination of the water diffusion coefficient for wood solid cuboids dried using convective drying methods. In this work, the authors define a theoretical dependence of the Fourier number on reduced water content in a convectively dried cuboidal solid, based on a simplified theoretical solution of the diffusion equation for such a body. The material for drying included shoots of common osier, robinia (false acacia), multiflora rose, and energy poplar, dried at temperatures of 40, 50, 60, 70, and 80 °C, in free convection. The obtained results differ from the theoretically anticipated changes of the coefficient.

Dependence of the ratio of squares of the velocity of acoustic waves in solids on the Gruneisen parameter

It is found that in the Leont'ev and Belomestnykh-Tesleva formulas for the Grüneisen parameter, the right-hand sides of the equalities depend on anharmonicity through the dependence of the ratio of the squared acoustic wave velocities ( v L2 / v S2) on the Grüneisen parameter γ. The theoretical dependence of ( v L2 / v S2) on γ generally agrees with experimental data for both crystals and glassy solids. The quantity ( v L2 / v S2) turns out to be a single-valued function of the ratio of the tangential and normal stiffness of the interatomic bond.

Parameters of the Infrasonic Signal Generated in the Atmosphere by a Powerful Volcano Explosion

The purpose of this work is to represent the results of performing regression analysis to fit the distance and the amplitude of the infrasonic signal generated by the explosion of St. Helens volcano, and to estimate a few signal and atmospheric parameters. The pressure amplitude in the explosion wave generated at the beginning of St. Helens volcano eruption was measured at 13 stations in the 0.9 – 39-Mm distance range; based on these data, an attempt has been made to perform a regression analysis to fit amplitude and distance. The regression based on the assumption that the infrasound propagation takes place in a waveguide where it is subject to attenuation is determined to be the most preferable regression. Based on the observations of the shock from the St. Helens volcano eruption, the shock wave energy and mean power have been estimated to be ~1016 J and ~2.3 TW, respectively. Based on the observations of the amplitude and duration of the trains of the infrasonic wave generated by the St. Helens volcano eruption, the infrasonic wave energy and mean power have been estimated to be ~1016 J and ~2 TW, respectively. Both estimates are in good agreement, but they are significantly different from those found in the literature; the latter seem to be overestimated. From the regression expression obtained, the penetration depth of the infrasonic wave is obtained to be about 33 Mm, whereas at other stations this scale length is estimated to be close to 24 Mm. Based on the theoretical dependence of the attenuation coefficient due to atmospheric turbulence, the attenuation length of the infrasound wave has been estimated for infrasound with 10–300-s periods. For 20–300-s periods, this value has been shown to be significantly larger than the values determined from the observations. Other mechanisms for attenuating the infrasonic signal are discussed (the partial radiation of the infrasonic energy through and losses due to the reflection from the waveguide walls). At the same time, the wave attenuation due to their scattering by turbulent fluctuations can be significant for the periods smaller than 20–50 s, depending on the turbulence intensity. Comparison of the regression functions obtained with the corresponding regression expressions for other sources of infrasound waves propagating in the atmosphere has been made. Keywords: volcano eruption, infrasonic wave, shock wave, signal amplitude, regression, signal attenuation

Efficiency of fire extinguishing with general purpose fire extinguishing powder in case of non-stationary interaction of its particles with burning material

Evaluation of the effectiveness of fire extinguishing by jet systems of powder fire extinguishing in conditions of non-stationary heat exchange processes and heterogeneous inhibition of active flame centers by powder particles was the aim of the work. The theoretical dependence of the amount of heat, absorbed by the particles of fire extinguishing powder, and the reaction rate of heterogeneous active centers of flame, inhibiting them, in non-stationary conditions of heat transfer, as well as inhibition reaction for fire extinguishing ink jet systems were obtained. The extinguishing of a flame with a fire extinguishing powder under non-stationary conditions is more effective, the smaller is the effective size of the powder particles, the longer is their stay in the combustion zone, and the shorter are the characteristic times of heat transfer and inhibition reaction. Comparison of the estimates of the characteristic duration of heat transfer and inhibition reaction for widely used fire extinguishing powders has shown a large inertia of the thermal mechanism of fire extinguishing, which greatly reduces its effectiveness at high speeds of powder particles in the combustion zone.