On the issue of selecting and optimizing parameters of continuous laser welding of cast iron

Introduction. Cast iron extremely poorly tolerate thermal welding cycles, and therefore it is necessary to choose carefully the technological parameters. The main parameters of continuous laser welding are: the power of laser radiation, the welding speed, the parameters of the focusing system. The aim of the work is to determine the optimal power and speed of continuous laser welding of cast iron, depending on the geometry of the weld. In this paper, the welding seams obtained on samples of gray alloyed cast iron with a pearlitic metal base, using an LS-1 ytterbium fiber laser, are studied. Research methods. The geometric parameters of the joints were quantified in the program for quantitative analysis and image processing ImageJ. The obtained data were processed by regression analysis. To optimize the process parameters, an orthogonal plan of the passive experiment was developed, including nine experiments in which the factors varied at three equally spaced levels. The quality parameters in the passive experiment were the geometric dimensions of the weld pool and the size of the quenched zone. To solve the optimization problem, we used the methods of gray relational analysis and linear programming. Results and Discussions. The obtained regression models explain a significant proportion of the variance of the dependent variables, the regression coefficients, as well as the models themselves, are statistically significant, which indicates a close linear relationship between the seam geometry and the process parameters. The calculated shape of the weld pool depending on the radiation power and welding speed shows that the required welding seam of the required dimensions can be obtained at various process parameters which allow solving a multi-criteria optimization problem. The gray relational evaluation of the geometric parameters of the seam shows that the most correct parameters in terms of obtaining the seam of the maximum depth with the minimum width, convexity (concavity) and the quenched zone are the minimum power and maximum welding speed. The calculation of the optimal radiation power and welding speed depending on the seam depth showed that welding of small thicknesses is optimally carried out with minimal power, and the seam depth is adjusted by changing the beam speed. Welding of large thicknesses is optimal at high speed, and to increase the depth of the seam, the power must increase.

Heat Transfer Research in Blown-Through Non-Passable Heating Mains Channels. Part 2

A schematic and structural solution of regenerative-utilization heat use in centralized heat supply systems was previously proposed in order to increase the efficiency of operation of heating networks located in non-passable channels. The impossibility of creating a full-scale experimental setup covering the required range of factors and the area of their change, the complexity of a passive experiment on existing heating mains led to the need to develop a virtual model based on the ANSYS sofware package. A six-factor experiment has been carried out on this virtual model. Regression equations have been obtained to determine the pressure required to provide air purging of the channel, as well as heat exchange with pipelines of direct and return network water located in the channel, and heat exchange with soil around the channel. In addition, a regression relationship has been derived to find the integral heat flux from the listed washed surfaces to the air flow. The transition from dimensionless to natural factors has been made in the paper. The most significant factors are identified with the help of Pareto cards. The obtained dependencies have been verified in Part 1 of the paper. The adequacy of the obtained regression equations has been determined using standard statistical estimation methods based on the calculated values of the Fisher’s, Student’s and other criteria. The response surfaces are presented and analyzed using two dimensional sections for a number of factor values at fixed values of one and a change in two most characteristic, physically significant for a given response function. They have been validated on the basis of the analysis of regression dependencies. The obtained regression equations cover almost the entire range of possible diameters of heating mains, which makes it possible to use them in the development of energy-saving projects.

Heat Transfer Research in Blown-Through Non-Passable Heating Mains Channels. Part 1

To increase the efficiency of operation of heating networks located in non-passable channels, a schematic and structural solution of regenerative-utilization heat use was previously proposed and at the same time it is shown that it isdifficult to create an acceptable full-scale experimental installation or the difficulty of conducting a passive experiment on existing heating mains in non-passable channels. As an alternative solution for performing research, it is proposed to create and use a virtual experimental setup developed on the basis of the ANSYS software package, which has received wide recognition in the world. The initial results of model verification showed that the study of heat transfer and aerodynamics in blown-through non-passable heating mains using such a solution is promising. A study has been carried out using a virtual experimental setup based on a six-factor second-order rotatble plan containing 46 points on a hypersphere with six star points. It is shown that there is no need to randomize the order of conducting and repeating the study at the points of computational experiment plan. Second-order regression equations have obtained for calculating a complex of objective functions: the required air pressure to achieve a given flow rate, the intensity of heat transfer directly from the pipes of the heating main, as well as from the walls of the channel to the blown air. The geometry of the channels of typical standard sizes of heating mains, the length of the sections, the temperature of the outside air and soil, and the air flow rate in the channel have been taken as the influencing factors in the calculations. For the obtained regression equations, significant coefficients have been established and the transition from dimensionless to natural factors has been carried out. The adequacy of the obtained regression equations has been determined using standard statistical estimation methods based on the calculated values of the Fisher’s, Student’s and other criteria.

Development of a methodology for the formation and adjustment of the catalog of defense forces capabilities

The study results have made it possible to devise a methodology for the formation and adjustment of the Defense Forces Capabilities Catalog using cluster analysis and the developed tree-like system of basic indicators characterizing groups and subgroups (clusters). That enables stakeholders to form and adjust the Defense Force Capabilities Catalog with the proper quality, according to the uniform developed algorithm and defined identifiers (features). The methodology is intended for use by members of the Inter-Departmental Working Group on Defense Review, as well as working groups in the course of a separate review or capacity assessment. The Defense Force Capabilities Catalog was deconstructed into five levels of hierarchy, each of which contains interdependent typical tasks, organizational structures, and means (systems, complexes). The procedure is to analyze and clearly cluster individual capabilities of the defense forces according to certain features (requirements, characteristics) to group them and include them in the relevant groups, subgroups, and functional capabilities groups. A system of the indicators for the formation and adjustment of the Defense Forces Capabilities Catalog has been proposed, as well as a conformity criterion based on the generalized indicator, which defines the level of formation (adjustment) of the Defense Forces Capabilities Catalog. Seven steps of the procedure have been defined: from identifying individual capabilities based on their description (step 1) to verifying the acceptability of the results obtained (step 7) using the evaluation criterion and specially designed tables. The methodology was tested during a passive experiment in 2020 on the analysis of the current Defense Forces Capabilities Catalog, which made it possible to identify a series of significant shortcomings in its structure and content.

Analysis of Failures of Selected Technical Objects

The article deals with selected issues concerning tests results of failures of selected objects used in the analyzed real technical system. The main operation goal of the analyzed system is to provide passengers with safe transport services within a given quantitative range and over a given territory. The analyzed technical objects were transport means. Transport services were provided along scheduled routes. Selected features and characteristics of vehicle failures have been discussed. Vehicles used in the investigated technical object were disassembled for the needs of the research. Tests were performed with the use of the passive experiment method under real service conditions.

Mathematical models in the management of copper production: ideas, methods, examples

Presents the current status in modelling of metallurgical processes considered by the model the mathematical model used in the description of the processes of copper production and their classification. Set out a system of methods and models in the field of mathematical modeling of technological processes, including balance sheet, statistics, optimization models, forecasting models and predictive models. For specific technological processes are developed: the model of the balance of the cycle of pyrometallurgical production of copper, polynomial model for prediction of matte composition on the basis of the passive experiment, predictive model of quantitative estimation of the copper content in the matte based on fuzzy logic. Of interest to students, postgraduates, teachers of technical universities, engineers and research workers who use mathematical methods for processing of data of laboratory and industrial experiments.

Mathematical model of milk secretion in a cow’s udder

The paper proposed a mathematical model that describes the dynamics of the physiological process of milk secretion in the cow’s udder, depending on the value of the time interval that has passed since the end of the last milking. The intensity of this process, and, consequently, the cow’s milk production level, depends, among other things, on the optimal choice of the multiplicity of milkings per day with certain time intervals between milkings. The proposed model will allow to take into account these factors in the analysis and optimization of conditions for the maintenance of dairy cattle herds. The results of the research are applicable in diagnosing the state of a cow, in a comparative assessment of the effectiveness of milking multiplicity, etc. The model’s determination coefficient is 0.82 for the aperiodic link used as a model. The advantage of the proposed approach to the identification of a biological object – a cow – is the use of a passive experiment technique based on statistical processing of experimental data on yields recorded by modern information systems for the management of cattle on existing dairy farms.

FOOD HABITS OF NORTHERN DEER, CONDUCING THEIR INVASIATION BY HELMINTHS

Reindeer, in contrary to the notion of him as a ruminant animal, moreover, is able to develop strategies against ectoparasites and has a specific eating habits, increasing its chances of helminths invasion. Thus, there are reports of the reindeer eating snow soaked in human urine, brackish soil, horns of both reindeer and elks, chicks, bird eggs and excrement, as well as lemmings. Using the method of a passive experiment (observation), reindeer have been investigated in a recreational farm in the Leningrad Region (60°8′32′′N, 30°19′35′′E60.142207, 30.326466) starting from February 2018. The animals of the parent flock were brought there from the Murmansk region, and in May-June 2018 females calved. Animals are kept in a fenced area in conditions close to natural. During the growing season, they eat grass (with the addition of concentrates), in the winter they are fed with lichen. Fresh water is always available in drinkers. Photo registration of animals was carried out using a 5D Mark II (Canon) SLR camera and Xperia XA2 smartphone (SONY) camera. In addition to typical ruminant eating behavior (grazing, rumination), synchronized drinking and urination/defecation were recorded. This illustrates the route of invasion of reindeer with elafostrongylosis (previously diagnosed in these animals) – namely, through the absorption of freshwater mollusks, which, along with land gastropods, are intermediate hosts of Elaphostrongulys rangiferi. Thus, it was discovered that reindeer not only tend to avoid water consumption from reservoirs polluted with feces and urine in the presence of an alternative, but also intentionally prefer this method to compensate for the loss of minerals.

А grain harvester performance according to unloading time and modes

The paper presents an analysis of the two ways of unloading the harvester grain hopper – unloading at standstill and unloading on the move. A passive experiment has been carried out during wheat harvest by measuring the loading time of a full harvester hopper into the transport vehicle. During its time measurement it has been found that for 237.4s the harvester is stopped and does not reap and does not perform actual output. The actual grain harvester output when unloading at standstill has been determined 17.15t/h (25.22 da/h) and the actually possible output if the harvester runs the same performance and unloads on the move it will reach an output of 20.91t/h (30.74 da/h), i.e. its output will increase by 19%. It has been found out that crop harvesting times can be shortened if the method unloading on the move is used, by about one day in harvesting the crop, respectively.