Experimental Study on Percolation Rate Characteristics of Gas-Filled Coal Bodies Based on True Triaxial Condition

To research the percolation rate of gas-filled coal based on true triaxial condition, this paper uses the three-phase coupling true triaxial servo test device to carry out the seepage test of coal, and the percolation rate of coal under different conditions of three factors such as gas pressure was measured by Darcy’s law, and the variation of percolation rate of coal was studied based on the comprehensive consideration of thermal elastic swelling deformation, expansion deformation of adsorbed gas, and compression deformation of interstitial pressure. The results are as follows: (1) When the main stress and temperature maintain unchanged, the percolation rate presents the trend which first decreases and then becomes gentle with the gas pressure; when the gas pressure and main stress maintain unchanged, the percolation rate increases with the decrease of temperature; when the pressure and temperature maintain unchanged, the changes of percolation rate present a shape of “V” with the main stress. (2) The strain curve of gas-filled coal decreases at first and then increases; that is, the percolation rate decreases gradually when the strain increases at the compression phase and elastic phase, while the percolation rate increases with the increase of strain at the yield phase and failure phase. (3) In the process of increasing volume stress, the percolation rate decreases gradually in the pore compaction stage, the percolation rate increases gradually from crack propagation to peak failure stage, and then, the percolation rate increases significantly after the peak damage. According to the test results, the percolation rate and volume strain show an inverse proportion.

A flexure-based linear guide with torsion reinforcement structures

In this work, a flexure-based (compliant) linear guide with a motion range comparable to its footprint is presented. The design consists of two folded leaf springs on which torsion reinforcement structures are added. Due to these structures, only two folded leaf springs are needed instead of a minimum of five as in pre-existing designs. The new design is compared to such a pre-existing design, after optimizing both on a support stiffness metric. The new design scores over twice as high on the support stiffness metric, while occupying a smaller (−33%) and a less obstructive build volume. Stress, build volume and manufacturing limitations are taken into account. Additionally, a variation on the new design using three torsion reinforced folded leaf springs is presented and optimized. This design occupies a build volume similar to the pre-existing design, but scores four times higher on the support stiffness metric. A prototype of the new design is built and its parasitic eigenfrequencies are measured, validating the theoretical models (Normalized Mean Absolute Error of 4.3%).

The Obtainment Process of Biopolymer Coated NPK Fertilizer and its Comparison with Analog on Berry Plants

The transition to a highly productive and environmentally friendly agricultural sector, the development and implementation of systems for the rational use of mineral fertilizers for obtaining safe and high-quality, including functional, food products is one of the main tasks allocated by the President of the Russian Federation V. V. Putin. Due to this decree, the theory of mineral nutrition has received rapid development in recent decades within scientific and technological progress in the field of analytical chemistry and physics, molecular biology, and genetics. Information on various physiological and biochemical functions of plant nutrients has been obtained, and the regularities of the distribution of elements in various parts of plants and fruits (berries) have been also generalized. The main forms of nutrients in the soil and the factors determining the bioavailability of macro and micronutrients have been identified. The aim of this research paper is to produce a biodegradable fertilizer where Azofoska Universal (N16: P16: K16) was uniformly coated within layer size by water-soluble biopolymer through continuous flow reactor V-star. The obtained samples were further tested and compared to well-known American analog slow-released fertilizer TAGROW on berry plants under greenhouse conditions within, berry root plant volume, stress resistance of plants, yield, the resulting fruits were studied for sugar levels using an RHB-32ATC refractometer. Moreover, infrared spectroscopy data for obtained biopolymer coated Azafoska Universal is illustrated in this research.

Geometric Modeling of Stress Visualization Tools Based on the Functional-Voxel Method

One of the approaches to the construction of graphic images of the stress state for the force vector applied to a point is considered in this work. Has been proposed a geometric model for a continuous medium, formed by a bunch of projection planes for each point of the examined object’s space. This permits to obtain a model for a volume vector in the form of a distributed decomposition into stress components at each point specified by a bunch of projection planes. The building a model for a volume vector, defined as a set of specified laws of direction and length, in the context of modeling stress from an applied force vector to a selected point, is based on strength of materials’ classical laws for calculation the stress state values at an inclined section. Such approach allows use a voxel graphic structure for computer representation of the simulated stress, rather than a finite element mesh. In such a case, there is no obtained result’s error dependence on the spatial position of the mesh nodal points, which is often a problem in FEM calculations. The resulting functional-voxel computer model of the volume stress vector is a structural unit for modeling the distributed load on areas of complex configuration. In this case, the elementary summation of such vectors allows any uneven distribution of the load relative to each point on the specified area. The considered approach works well with geometric models initially represented analytically in the form of a function space (for example, models obtained by the R-functional modelling – RFM-method), and reduced to functional-voxel computer models. A method for deformation modeling based on obtained stresses by means of local transformations of the function space, describing the investigated geometric object, is demonstrated.

SIMULATY OF VOLUME STRESS-DEFORMED STATE IN A REINFORCED TITANIUM-ALUMINUM COMPOSITE WHEN DETERMINING THE HARDNESS BY BRINELL

The effect of the diametrs and arrangement of titanium fibers in a fibrous composite with an aluminum matrix on the change in the stress-strain state upon indentation of a rigid spherical indenter by the Brinell method has been studied. The process of introducing a hard ball Ø 5 mm under a load of 1226 N was simulated in the SIMULIA / Abaqus software package. The distribution of plastic deformation in the cells near the surface of the deformed plate in the axial section has two maxima and almost zero near the center of the hole. The print becomes elliptical when the indenter is positioned over the axis of the titanium wire. The major axis of the ellipse is perpendicular to the axes of the wires. This is due to the restraint of aluminum deformation in this direction by titanium fibers.

Transient Pulse Test for Non-Darcy Flow Behaviors and Hydromechanical Coupling Effect of Fractured Limestone

In this paper, the transient pulse test is used to study the permeability and hydromechanical coupling effect of the fractured limestone. The permeability parameters (permeability, β factor of non-Darcy flow, and acceleration coefficient) of non-Darcy flow in fractured limestone are obtained by experimental data. The experimental results show that, in the process of transient seepage test of fractured Maokou limestone, the relationship between hydraulic pressure gradient and seepage velocity does not conform to Darcy’s law but meets Forchimer relationship. The relationship between hydraulic pressure difference and time can be fitted by quartic polynomial. The larger the confining pressure is, the more obvious the non-Darcy seepage effect of fractured rock seepage is. The seepage of rock fracture under high confining pressure is a highly nonlinear time-varying seepage. The permeability coefficient of rock decreases with the increase of volume stress. Under the action of low volume stress, the relationship between permeability coefficient and stress is more sensitive, while under the action of high volume stress, the relationship between permeability coefficient and volume stress is not significant. In the process of volume stress increasing, the β factor of non-Darcy flow appears negative. Under the action of low volume stress, the acceleration coefficient and β factor of non-Darcy flow increase, while under the action of high volume stress, the acceleration coefficient and β factor of non-Darcy flow decrease.

The study of marginal deformations of the leaf extracts with regard to plastic thinning and destruction of the material

The aim of work. The paper analyzes the process of sheet drawing and develops a method for determining the minimum curvature of the torus fillet in the formation of a cylindrical product (glass), taking into account the plastic thinning of the deformable material by the end edge of the pressing punch. Methods. The existing scheme of forming with the use of permissible coefficients of drawing and tensile strength of the material, representing the basis of deformation-force calculation, which often ignores the factor of deformation thinning and its impact on the strength of the material, which together can lead to excess of the allowable stress in the material, causing its rupture, is analyzed. A mathematical model of the volume stress state of the metal is developed, which allows to estimate the value of the thinning in the formation of the torus surface of different curvature, followed by the approximation of the values found by a polynomial function. Considering the criterion of limit loads the level of radial stresses during folding and stretching of the sheet material, taking into account its thinning, the minimum curvature of the torus surface of the glass is established. Results. The results obtained will allow to simulate the stress-strain state of the metal in the development of sheet drawing technology: to establish the value of thinning and to estimate the level of radial stresses in the formation of the torus surface rounding to prevent the destruction of the elongated glass (separation of the bottom), which guarantees quality products.

Low-Frequency Piezoelectric Accelerometer Array for Fully Implantable Cochlear Implants

We demonstrate a low-volume, stress-free, piezoelectric micro-electromechanical system (MEMS) cantilever array for fully implantable hearing aids. The 12-element spiral-matrix is sensitive to the lower part of audible frequency range (300–700 Hz) through the proper resonant frequency of the individual spirals tuned by dimensions of the cantilevers. The obtained high Q-factors (117–254) provide high frequency selectivity. The generated open circuit voltage signals could be sufficient for the direct analog conversion of the signals for cochlear multielectrode implants. By comparing different geometries we have also demonstrated that the initial stress, which is derived from silicon-dioxide (SiO2) and aluminum-nitride (AlN) layers, could be drastically reduced simply by the spiral geometry. The results of vibration measurements have shown a good agreement with the calculated resonant frequencies.