DETERMINATION OF THE COEFFICIENT OF THE DYNAMIC SHAPE OF DUST PARTICLES RELEASED IN THE AREA OF GRINDING MACHINES

При проведении работ по заточке твердосплавных инструментов абразивными кругами на универсальных заточных станках образуется значительное количество пылевых частиц. Часть пылевых частиц, в зависимости от размеров, находится во взвешенном состоянии. Длительное воздействие пылевых аэрозолей на организм рабочих может привезти к развитию большого количества профессиональных заболеваний дыхательных путей. Установлено, что на характер движения пылевых частиц в рабочей зоне и скорость их осаждения влияет такой параметр, как форма пылевой частицы. Материал для исследования и расчета был собран на предприятии ООО «Русский инструмент», которое расположено в пгт. Северный, Белгородского района. Отбор проб производился в разных зонах заточного участка. На основе имеющихся проб пылевых частиц, на базе лаборатории БГТУ им. В. Г. Шухова, были получены результаты электронной микроскопии. Целью данной работы является определение коэффициента формы пылевых частиц, с использованием существующих методик определения данного коэффициента. Полученные результаты позволяют дополнить исходные данные для разработки математической модели процессов течения пылевых частиц вблизи местного отсоса и последующего компьютерного моделирования течений пылевых аэрозолей в кожухе-пылеуловителе. When working on sharpening carbide tools with abrasive wheels on universal grinding machines, a significant amount of dust particles is formed. A certain part of the dust particles, depending on the size, is suspended. Prolonged exposure to dust aerosols on the body of machine turners can lead to the development of a large number of occupational diseases of the respiratory tract. It is established that in the working area, the nature of the movement of dust particles, as well as the rate of their deposition, is affected by such a parameter as the shape of the dust particle. The material for the study, calculation and subsequent computer simulation of the dust aerosol flows in the dust collector casing was collected at the OOO Russian Tool, which is located in the village Severny, Belgorod district. The samples were taken in different zones of the grinding area. Based on the available samples of dust particles, the results of electron microscopy were obtained at the laboratory of BSTU named after V. G. Shukhov. The purpose of this work is to describe the results obtained and determine the shape coefficient of dust particles, using existing methods for determining this coefficient. The material of the work allows us to supplement the initial data for the development of a mathematical model of the processes of the flow of dust particles near the local suction.

Study on the Aging Time Variation Law of Mechanical Properties of the Laminated Rubber Bearing in Coastal Bridges considering Frictional Slip

As an important support member in the structural system of coastal bridges, the frictional slip and the rubber aging of laminated rubber bearings will affect the service safety of the overall structure in earthquakes. In order to investigate the mechanical properties aging law of the rubber bearings considering frictional slip in the coastal bridges, a frictional slip experiment was carried out on the laminated rubber bearings. Moreover, the influence of rubber aging on the mechanical properties of the bearings with various shape coefficients was analyzed by the finite element method during the 100 years of service life of bridges. The results indicate that (1) the horizontal and vertical stiffness of the bearing increase linearly with the aging time of the rubber. The amplification of the bearing stiffness also grows with the shape coefficient of the bearing. (2) The frictional slip initiation displacement of the bearing grows with the rubber aging time. Furthermore, the larger the shape coefficient of the bearing is, the more the frictional slip initiation displacement of the bearing increases. (3) With the increase of the aging time, the equivalent viscous damping ratio of the bearing continues to increase and more energy is consumed by frictional slip. For the bearing with the shape coefficient of 16.38, the equivalent viscous damping ratio at 100 years of rubber aging time is 1.17 times higher than that of the initial state of the bearing, and 33.21% more energy is consumed through frictional slip. Given that the marine environment accelerates rubber aging and changes the mechanical properties, the effects of the frictional slip and rubber aging properties of the laminated rubber bearings on the seismic dynamic response of bridges should be considered in the seismic design of coastal bridges.

Numerical Simulation of Elbow Erosion in Shale Gas Fields under Gas-Solid Two-Phase Flow

Erosion is one of the most common forms of material failure and equipment damage in gas transmission pipelines. Shale gas fields use hydraulic fracturing whereby solid particles are often carried in the gas flow, and the pipeline is in a high-pressure state, which is more likely to cause erosion. The prediction of particle erosion regulation in gas-solid two-phase flow is an effective means to ensure the safe operation of shale gas fields. In this paper, an integrated CFD-DPM model is established to investigate the erosion of 90° elbow in a shale gas field under gas-solid two-phase flow, employing the realizable k-ε turbulence model, discrete phase model, and erosion rate prediction model. The reliability of the proposed numerical models is verified by comparing the predicted data with the experimental data. Moreover, the effects of six important factors on maximum erosion rate are analyzed, including gas velocity, mass flow rate of sand particles, particle diameter, shape coefficient of sand particles, pipeline diameter, elbow radius of curvature. Specifically, the results indicate that the gas velocity, mass flow rate and shape coefficient of sand particles are positively correlated with the maximum erosion rate, while the pipe diameter and the elbow radius of curvature are negatively correlated with the maximum erosion rate. A new correlation was developed, which included four dimensionless groups, namely Reynolds number, diameter ratio, density ratio and particle number. The correlation can be used to predict maximum corrosion rate of elbows. This work can provide data reference and theoretical basis for mitigating the erosion rate of pipelines and managing the integrity of gas pipelines.

Scots pine (Pinus sylvestris L.) cones phenotypic variation growing in provenance trials of Arkhangelsk region

The study results of phenotypic variability of Scots pine cones climatype (23 variants) in provenance trials in the Plesetsk forestry of the Arkhangelsk region, created in 1977, are given. The distribution of cones in the collection of provenance according to the forms of the apophysis proposed by Pravdin L.F. is presented, linear parameters, mass, shape coefficient and density of cones are determined. Pine provenances were conditionally divided into two groups depending on the geographical coordinates of the original plantations — western (with a latitudinal localization of climates from 68 to 55 degrees. N., but close in longitude) and eastern (with a longitude localization of climates from 40 to 73 degrees. E., but close in latitude) groups. In both groups, the distribution of cones according to the forms of the apophysis has a similar structure, the form of the apophysis f. gibba is most pronounced. The severity of the shape of the apophysis of the cone can be associated with the genetic features of the species and with the conditions of the growth place of the original plantations. Significant correlation connections between shape of cones apophysis with temperature climatic indices are established. In the collection of provenances, when growing under the same type of conditions, the length and width of the cone are equalized between offspring, however, the increase in the mass of the bump and the decrease in its density are under great genetic control, although it is associated with the geographical origin of the offspring.

Probabilistic Assessment of Roof Snow Load and the Calibration of Shape Coefficients in the Eurocodes

In modern structural codes, the reference value of the snow load on roofs is commonly given as the product of the characteristic value of the ground snow load at the construction site multiplied by the shape coefficient. The shape coefficient is a conversion factor which depends on the roof geometry, its wind exposure, and its thermal properties. In the Eurocodes, the characteristic roof snow load is either defined as the value corresponding to an annual probability of exceedance of 0.02 or as a nominal value. In this paper, an improved methodology to evaluate the roof snow load characterized by a given probability of exceedance (e.g., p=0.02 in one year) is presented based on appropriate probability density functions for ground snow loads and shape coefficients, duly taking into account the influence of the roof’s geometry and its exposure to wind. In that context, the curves for the design values of the shape coefficients are provided as a function of the coefficient of variation (COVg) of the yearly maxima of the snow load on the ground expected at a given site, considering three relevant wind exposure conditions: sheltered or non-exposed, semi-sheltered or normal, and windswept or exposed. The design shape coefficients for flat and pitched roofs, obtained considering roof snow load measurements collected in Europe during the European Snow Load Research Project (ESLRP) and in Norway, are finally compared with the roof snow load provisions given in the relevant existing Eurocode EN1991-1-3:2003 and in the new version being developed (prEN1991-1-3:2020) for the “second generation” of the Eurocodes.

Determination of Shape Coefficient in Elastic Modulus Estimation with Penetration Test

Elastic modulus is a significant parameter in design and construction for rock engineering. Rock penetration test as a convenient method to evaluate the modulus of rocks has a great potential to be used. Based on the elastic theory, the relationship between rock penetration behavior and elastic modulus was established. In order to evaluate the elastic modulus, the shape coefficient is an important parameter to be determined. However, due to many factors, the value of this parameter is still uncertain. To provide a better insight into the shape coefficient and its factors, a series of penetration tests which used several types of rock samples with different sizes were conducted to study the determination of shape coefficient under different conditions. The test results show that sample size influences the shape coefficient, and with the increase in size, the shape coefficient decreases gradually to a stable value. In contrast, confining pressure has less effect on shape coefficient, and in the moderate and low stresses region, a fixed value can be selected for the test. Different types of rocks correspond to different shape coefficients. The shape coefficient of hard rock is higher than that of soft rock. Shape coefficient should be selected reasonably according to the penetration depth in practical application, and the reason, furthermore, why back-calculated shape coefficient deviates from the theoretical value is also discussed.

Intelligent vehicle modeling design based on image processing

With the urgent demand of consumers for diversified automobile modeling, simple, efficient, and intelligent automobile modeling analysis and modeling method is an urgent problem to be solved in current automobile modeling design. The purpose of this article is to analyze the modeling preference and trend of the current automobile market in time, which can assist the modeling design of new models of automobile main engine factories and strengthen their branding family. Intelligent rapid modeling shortens the current modeling design cycle, so that the product rapid iteration is to occupy an active position in the automotive market. In this article, aiming at the family analysis of automobile front face, the image database of automobile front face modeling analysis was created. The database included two data sets of vehicle signs and no vehicle signs, and the image data of vehicle front face modeling of most models of 22 domestic mainstream brands were collected. Then, this article adopts the image classification processing method in computer vision to conduct car brand classification training on the database. Based on ResNet-8 and other model architectures, it trains and classifies the intelligent vehicle brand classification database with and without vehicle label. Finally, based on the shape coefficient, a 3D wireframe model and a curved surface model are obtained. The experimental results show that the 3D curve model can be obtained based on a single image from any angle, which greatly shortens the modeling period by 92%.

Morphological response of the leaf blades of B. pendula Roth. to the influence of man-made environmental factors

Due to the technogenic transformation of ecotopes of ash and slag dumps of Burshtyn TPP, bioindications of the environment state in the zone of their influence are an urgent issue. The morphological reaction of Betula pendula Roth. leaves under the influence of man-caused factors of Burshtyn TPP ash and slag dumps was studied. The change in the shape of the leaf blades of B. pendula under the conditions of ash and slag dumps was analysed. The degree of modification of leaf blades was evaluated through the measures of shape coefficient and elongation coefficient. The use of morphological coefficients testified to their specificity. The form coefficient indicator proved to be a sensitive marker. The change in the area of leaf blades under the conditions of high levels of anthropopression was analyzed. On the territory of ash and slag dumps there was a decrease of leaf area. At the same time, a high level of necrotization of leaf blades was recorded. The condition of plants was assessed through the index of fluctuating asymmetry of B. pendula leaf blades. As a result of the study, the foliar morphometric parameters of B. pendula were determined, which showed high morphological reactivity under the influence of man-caused load and can be used as bioindication markers for assessing the state of the environment.

Measurement and simulation validation of numerical model parameters of fresh concrete

In the numerical simulation of the macroscopic flow of the concrete, it can optimize the performance indicators of the screw conveyor and improve the uniformity of the material to be discharged in the batch production. The discrete element method is effective. The accuracy of physical parameters of this method is a key issue for the reliability of the simulation results of concrete. In this study, we measured the parameters describing the interaction between gravel, mortar, as well as between these two materials and the wall (steel). The experimentally determined parameters include the particle density, size, shape, coefficient of restitution, coefficients of static, and rolling friction. The cohesion coefficient of mortar particles for batch time was obtained by comparing the spread diameter and flow time in V-funnel experiments and simulation. After these calibration steps, the DEM parameters were validated by comparison of the mass flow rate and driving power by the batch production of screw conveying in simulations and experiments. The calculated results are proved to be close to the experimental data, which demonstrates that the measured DEM parameters are of sufficient accuracy to be used in the simulation of concrete flow performance (mass flow rate, energy consumption) in the screw conveyors.