Working Section Research Articles

Creep Behavior Characterization of Nickel-Based Single-Crystal Superalloy DD6 Thin-Walled Specimens Based on a 3D-DIC Method.

The thickness debit effect of creep behavior has been a focal point of nickel-based single-crystal superalloy research, and there is a need for an advanced creep deformation measurement method. This study developed a novel high-temperature creep test system based on a single-camera stereo digital image correlation (DIC) method with four plane mirrors to conduct creep tests on thin-walled specimens of a nickel-based single-crystal alloy, DD6, with thicknesses of 0.6 mm and 1.2 mm under experimental conditions of 980 °C/250 MPa. The reliability of the single-camera stereo DIC method in measuring long-term deformation at a high temperature was experimentally verified. The experimental results show that the creep life of the thinner specimen was significantly shorter. It was found the lack of coordination in the creep deformation process of the edge and middle section of the thin-walled specimens may be an important factor in the thickness debit effect according to the full-field strain contour. By comparing the local strain curve at the rupture point with the average creep strain curve, it was found that the creep rate at the rupture point was less affected by the specimen thickness during the secondary creep stage, while the average creep rate in the working section significantly increased as the wall thickness decreased. The thicker specimen usually had a higher average rupture strain and higher damage tolerance, which prolonged the rupture time.

Определение участка нарезания мелкомодульных зубьев в эксцентриковых механизмах свободного хода

Normal forces use to transfer the load makes it possible to increase load capacity and reliability of the free running mechanisms. Normal forces in the eccentric free running mechanisms are realized in engagement of the fine-module teeth that are cut on the outer cage inner surface and the outer surface of the eccentric rings. To ensure correct operation of the mechanism in jamming and wedging, value of the fine-module teeth cutting section angle should be selected from the equality condition of the radial clearance between the outer cage teeth and the eccentric ring in the entire working section. To solve the problem, calculation scheme is proposed and mathematical model is obtained that describes relationship between the fine-module cutting section angle and the mechanism geometric parameters. The nature of the main geometric parameters influence (radius, eccentricity, radial clearance, module, etc.) on the value of the teeth cutting section angle was established. It is shown that eccentricity provides the greatest influence on the working area size, radial clearance and module influences are less pronounced.

Ensuring a safe geomechanical state of the rock mass surrounding the mine workings in the Karaganda coal basin, Kazakhstan

Purpose. The research purpose is to determine the instability zones in the host rocks and the dynamics of propagation of active fracturing zones to ensure the stability of the rock mass surrounding the mine workings. Methods. The research uses a set of analytical and experimental studies to determine the dynamics of the deformation process development in the coal-rock mass surrounding the mine workings. Mathematical modeling of the stress-strain state of the rock mass surrounding the active extraction workings is performed using the numerical method of finite elements in modern AN-SYS, Mergel and KMS-III software products. Findings. The influence has been studied of the mine working section shape and the coal seam dip angle on the value of the maximum stresses that arise in the rock mass when the mine working is fastened with the roof-bolt support. The instability zones in the host rocks and the dynamics of propagation of active fracturing zones have been determined both ahead of the front of the conducted mine working and on its sides for rocks of different strength. Originality. For the conditions of the Karaganda coal basin, the dependence of a change in the development of conventional inelastic deformation zones (CIDZ) on the host rock strength has been revealed. The influence of the coal seam dip angle on the dynamics of stratifications around preparatory working has also been substantiated. In addition, new data have been obtained on the influence of the roof rock strength on the stratification of the rock mass surrounding the mine working. Practical implications. By determining instability zones in the host rocks and the dynamics of propagation of active fracturing zones, it is possible to control geomechanical processes in the border rock mass of a mine working and influence it in order to prevent the occurrence of negative rock pressure manifestations. The data obtained are the basis for the development of recommendations on the use of roof-bolting technology for fastening extraction workings to ensure their stability and reduce the cost of their operation.

Intelligent Dynamic Test System for Vehicle Engine Based on 5G Internet of Things

With the development of the automobile industry, the improvement of the reliability test level and the intelligent fault diagnosis level of the engine, as the heart component of the automobile and the assembly with the highest failure rate, becomes more and more important. In a context where technology is being upgraded, the development of intelligent automotive engine inspection system based on IoT thinking is set to become the major trend in the future. The objective of this article would be to have better knowledge about smart car engine system in the 5G IoT era. It is also through the study, a dynamic testing and characterization of the engine. The performance of the automobile engine, especially the dynamic performance, is further optimized. In this article, we focus on the PUMAOPEN test system of AVL and the system under test, the state management of the test process, and the intelligent transformation of key components. The results show that: studies and analyses the dynamic working conditions of intelligent vehicles on the Internet of Things, and compares the dynamic working conditions with the steady working conditions from qualitative to quantitative. By analyzing the influence of throttle opening change rate and speed change rate on dynamic performance and engine dynamic torque estimation, the fast sensing and response-ability in the engine testing process is improved. When the engine is accelerated by the experimental method presented in this article, and when the throttle opening is more than 30% and the engine speed varies at 100 and 200 rpm/s, the output value of the torque is higher than the output value of the steady-state torque or has little difference with the output value of the steady-state torque, and tends to be stable. In deceleration performance, the dynamic output torque of the engine is asymmetric. And it will deviate from the steady-state output torque, showing different dynamic response characteristics in different working sections. Throttle delay, overshoot characteristics, mechanical inertia, inflation coefficient, air–fuel ratio, and ignition advance angle when engine speed changes sharply will make engine dynamic characteristics deviate from steady-state characteristics.

Экспериментальное исследование накопления углеродных отложений в кислородно-метановом модельном газовом тракте

The paper considers mechanisms of the carbon deposits formation on the metal surface at contact with the gas phase containing products of incomplete combustion of the oxygen-methane generator gas. The first mechanism is the socalled mechanism of metal dust formation, which products remain on the wall surface and form the carbon deposits, the second is the mechanism of carbon deposits formation associated with the carbon particles in the gas flow, which are being deposited on the wall. An experimental system was developed with the working section being a model path of the oxygen-methane generator gas of the reducing composition; and accumulation of the carbon deposits was experimentally studied. When selecting performance characteristics of the experimental system, features of the liquid rocket engine gas path were taken into account; therefor, the experimental system was having characteristics closer to the expected characteristics of the full-scale gas path. Intensities of the deposit formation on samples of metallic material and reference quartz were compared. It was established that the main mechanism for the carbon deposits formation was precipitation of soot contained in the generator gas flow onto the wall of the gas path. The number of deposits was determined by weight. The range of the fuel components ratio was identified, where formation of the deposits was minimal

Frequency of respiratory symptoms among rice mill workers in Bangladesh: A cross-sectional study.

Rice mill workers are frequently exposed to rice dust specks containing bacteria, endotoxins, spores, and chemicals in workplaces. Consequently, they develop diverse respiratory symptoms that lead to increased disability and social burden. The present study was conducted to observe the frequency of respiratory symptoms among rice mill workers in Bangladesh. This cross-sectional study was conducted at different rice mills in Rangpur district of Bangladesh. Three hundred and forty-six rice mill workers, both male and female of 18 years and above, with a job experience of at least 3 years, were selected as study subjects. An equal number of people who had never worked at rice mills were selected from the nearby locality as the nonexposed group. Enquiries were made regarding respiratory symptoms with the help of a preformed questionnaire which contained sociodemographic characteristics, occupational history, potential confounding factors, and physical parameters. A respiratory dust sampler was used to measure workplace dust concentration. The presence of one or more respiratory symptoms was significantly higher among rice mill workers than in the nonexposed group (52.3% vs. 17.6%). Rice mill workers who worked for more than 10 h and had a working experience of more than 15 years had a higher frequency of respiratory symptoms (41.3% and 39.8%, respectively). Rice mill workers with body mass index (BMI)<18.5 also exhibited more respiratory symptoms (25.4%). All working sections had a higher-than-average dust concentration level, with the milling section being the dustiest (PM 2.5 492.1 µg/m3). This study showed an increased frequency of respiratory symptoms among rice mill workers of Bangladesh. Longer working experience and working hours, low BMI and high dust concentration levels were strongly associated with that increase in frequency.

Measurement and Numerical Simulation of Cylinder Surface Pressure under Different Air Volumes

As a classic research topic of fluid mechanics, the research on the problem of flow around a circular cylinder is essential both from the perspective of academic research and application in the engineering industry. In this paper, the surface pressure of the cylinder is measured by the experimental research on the flow around the circular cylinder, the three-dimensional modeling of the key parts of the experiment is carried out according to the one-to-one size, and the three-dimensional CFD software is used to numerically simulate the velocity field and the pressure field. The research shows that under different air volumes, the relative error between the experimental value and the simulated value of the inlet velocity in the convergence section and the working section is less than 5%. It can be considered that the results of the numerical simulation and the experimental results are within the allowable range. The relative error between the experimental value and the simulated value of pressure is less than 2%, and the numerical simulation results are consistent with the experimental results. It lays a theoretical foundation for the improvement of the flow around the cylinder experiment and its engineering application in the future.

Noninvasive Measurement Methods for Transient Flows in Wind Tunnels

The noninvasive measurement technique proposed in this paper uses the response of a Kevlar wall in a wind tunnel to infer the angle-of-attack time history of an airfoil in the working section undergoing a pitching motion. Recent work has shown that the displacement of a Kevlar wall can be measured accurately via an optical method to obtain the loading on an airfoil in a steady flow, but the feasibility of using this method on time-varying flows has yet to be explored. Based on thin airfoil theory, a model of an airfoil undergoing a sudden change in angle of attack is considered, and the pressure along the wall was found using potential flow theory. The process of relating the pressure field to the wall displacement is presented, and it is shown how the wall response can be found. The membrane response is then used to obtain estimates of the angle-of-attack time history of the airfoil through an inversion process. It was found that the response of the Kevlar wall is dominated by the effects of the circulation around the airfoil and not its wake, and so the unsteady airfoil lift is measured with the proposed method, without the need for a force balance with a fast response time. The limitations and the applications of the proposed measurement method are discussed.

Heat transfer of a modified surface with a dispersed coolant flow

The authors carried out a modification of the surface of the working section of the experimental stand, which simulates the energy-loaded elements of thermonuclear installations. The surface was modified by the knurling method, as a result of which structures with a characteristic size of 250 μm were obtained. An experimental study of the heat transfer of a modified surface with a dispersed coolant flow was carried out. The excess pressure of the coolant at the nozzle inlet was (1.5–3.5) × 105 Pa), the mass flow rate of the coolant (distilled water) was (3.9–6.1)×10-3 kg/s, irrigation density varied within (4.2–6.2) kg/(m2·s), initial temperature of the coolant 25.8–26.4 °C. As a result, experimental dependences of the heat flux density and heat transfer coefficient on the temperature of the cooled wall were obtained. The results obtained on the modified surface were compared with the results obtained on the surface without modified structures under similar operating parameters of the coolant.

Coolant temperature distribution in the model of the fuel assembly peripheral area

To evaluate the interchannel temperature transfer, the test section was created, the working section of which is a model of two neighboring cells of the peripheral region of the fuel assembly. The experimental setup is equipped with three fuel rod simulators 500 mm long. During the work, the fuel rods were connected in turn to the power source. This made it possible to determine the features of the temperature distribution in the model with uneven energy release. The power of each fuel rod simulator was up to 2000 W. A movable thermocouple and an IR camera were used for measurements.

ВЛИЯНИЕ ЭЛЕКТРОХИМИЧЕСКОЙ ОБРАБОТКИ НА СОСТОЯНИЕ ПОВЕРХНОСТНОГО СЛОЯ ЭЛЕМЕНТОВ ШТАМПОВОЙ ОСНАСТКИ

The article is devoted to studying the influence of technological parameters of electrochemical dimensional processing mode on the structure and physical and mechanical parameters of the die engraving working sections, which made it possible to recommend this method as a finishing operation in the manufacture of forging dies.

Studying multiphase flow around a vehicle moving freely to the water surface

The paper provides an experimental study of a multiphase flow around models in a large high-speed hydrodynamic tunnel with a vertical working section. Experimental dependences of drag coefficients on the cavitation number for vertical cavities are obtained. The results of cavitation flow around bodies of revolution in a vertically descending fluid flow are considered. A methodology for calculating the shape of vertical cavities under the slender-body theory is proposed. Relationships suitable for engineering evaluation are obtained for very long cavities. Numerical simulation of underwater motion is performed with models moving vertically in a nonstationary cavitation flow. The hydrodynamic loads can be evaluated through the determination of the nonstationary boundaries of a gas cavity and a linear load on a water-flown aft. The predicted results are compared with the experimental data. Validation and verification are performed by comparing the analysis results with the experimental data. The applicability of the proposed method to the determination of the hydrodynamic parameters of vehicles under multiphase flow is demonstrated.

Influence of the Chemical Activation of Aggregates on the Properties of Lightweight Vibro-Centrifuged Fiber-Reinforced Concrete

One of the most essential building materials for sustainable development is concrete. However, there is a problem with a lack of inexpensive, efficient ways to make it high-strength and ultra-dense. A promising direction is the additional processing or activation of the cheapest component of the concrete mixture—inert aggregate. The article is devoted to a promising method for the simultaneous activation of both large and small aggregates using vibro-centrifuge technology. It has been established that the activation of concrete aggregates with aqueous solutions of natural bischofite at a concentration of 6 g of dry matter per 1 L of water is the most rational and contributes the maximum increase in strength characteristics and the best values of strain characteristics. Strength characteristics increased up to 16% and ultimate strains increased to 31%, respectively, and the modulus of elasticity increased to 9%. A new improved lightweight fiber-reinforced concrete was created and an innovative technology is proposed that makes it possible to achieve savings in manufacturing due to a significant improvement in structural properties and reducing the working sections of reinforced concrete elements. Regularities between the fundamental chemical processes of the surface activation of aggregates and the physical processes of structure formation of compacted and hardened concrete were revealed. An improvement in the structure of concrete at the micro- and macro-levels was recorded due to a point decrease in crack formation at the interfaces of the “cement matrix-aggregate” and “cement matrix-fiber” phases, and a decrease in the number of micropore defects was also found. Economic efficiency reached 25–27%.

Development of prototype fritting furnace for small scale pottery producers in Nigeria

Frit is an essential material required in the composition of low temperature glazes. Unfortunately, up till the year 2020 appropriate furnace for local production of frit is scarce in Nigeria. This may be due to the prohibitive prices of customary refractory materials, exorbitant cost for construction of a standard frit furnace, and the epileptic power supply to run a frit producing plant. Consequently, previous attempts to produce frit locally ended up in losses and products froth with impurities. In this work, the continuous-flow frit kiln with a sloping floor design was modified and a prototype was constructed using locally sourced refractory. The working section was lined with highly corrosion resistance monolith produced with a ramming mass composed of zircon and kaolinite. It has a volume of 10.62 litre. The furnace runs on butane gas, it is fed with pre-treated precursor in granules form and capable of continuous production of 30 kg of frit per hour (kg/h) at 1100 oC. With the appropriate burner, the furnace achieved the optimum operation temperature of 1100oC within two hours. The design is suitable for private studio, research and educational institutions. It can also be scaled up for industrial uses.

Cultivator for Inter-row Cultivation of Cotton N.V. Aldoshin

The issues of inter-row processing of agricultural crops are considered. The article proposes a layout scheme of a wide-cut cultivator-plant feeder for cotton cultivation, design and technological solutions, including the improvement of the working sections of the machine and systems of intrasoil application of mineral fertilizers, test results for processing cotton row spacing after irrigation in the conditions of the Republic of Uzbekistan.

Совершенствование технологий химико-термической обработки для поверхностного упрочнения высоколегированных сталей авиационного назначения

The analysis of ways to improve gas nitriding method allowing for proper diffusion layers in chromium-nickel martensitic and maraging aviation steels treatment is pre-sented. The method consists in combination of different temperature conditions on change of ammonia and air concentration in the working section of the furnace. The study outcome of the microstructure and phase composition of the obtained diffusion layers are presented. The experimental data for microhardness, wear strengh properties and modulus of reselience in function of layers structure are discussed

СИНТЕЗ ПРОСТРАНСТВЕННЫХ ПЯТИ- И ШЕСТИЗВЕН-НЫХ МЕХАНИЗМОВ С ВРАЩАТЕЛЬНЫМИ ПАРАМИ ПО ДВИЖЕНИЮ ВЫХОДНОГО ЗВЕНА

The research was carried out in order to identify the optimal structural schemes of three-dimensional five- and six-link mechanisms with rotational pairs, which reproduce with the required accuracy a linear function during oscillatory and rotational motion of the output link. Spatial mechanisms, which are used as transmission and base mechanisms, make it possible to recreate the movement of the output or any working link with a given accuracy and provide the necessary rigidity, reliability and compactness of the structure. The synthesis of spatial mechanisms was carried out according to the given law of the output link. To implement oscillatory motion with working sections on the forward and reverse stroke, you can use crank-rocker five-links, in which the angles of crossing of the geometric axes of the hinges of adjacent links 4 and 5 are equal to . In a similar way, the synthesis of a spatial five-link was carried out, in which the angles of crossing the axes of the hinges of the output link α_4 and the rack α_5 are related by the dependence α_4= , by reproducing the oscillatory motion of the output balancer with the working stroke in a straight section. Optimal structural schemes of three-dimensional five- and six-link mechanisms are revealed, which reproduce with the required accuracy a linear function during the oscillatory and rotational motion of the output link. The resulting dependencies will be used to automate the optimization synthesis for the objective function of the six-link mechanism (or its five-link modification), which reproduces a linear function on a certain part of the turn of the output link with its full cranking

Shape-Dependent Strength of Al Si9Cu3FeZn Die-Cast Alloy in Impact Zone of Conformal Cooling Core.

This article presents the results of shape-dependent strength analyses in die-castings from traditional (straight-drilled) and conformal core-cooling moulds. Cores with a traditional cooling layout were made of H13 steel using machining, and the working sections of the conformal cores were made using the selective laser melting method (SLM). Two series of casts were produced in the same mould. For Series A, the mould was fitted with traditional cooling cores, and for Series B, the same mould was fitted with conformal ones. The cast specimens were subjected to two weeks of natural ageing. The strength testing of the casts determined the levels of the destructive forces. The destructive forces in the core-cooling impact zones were approximately 28% higher in the B samples than they were in the A samples. The impact of the alloy’s porosity, density, and microstructure on the strengths of the casts was demonstrated. The alloy densities in the central (broken-off) fragments of the casts from Series A were 2.6646 g/cm3; these were 2.6791 g/cm3 in the cases of casts from Series B. The values of the secondary dendrite arm space (SDAS) ranged from 6 to 13 μm in the analysed cross-section of the set of the A casts, and between 3 and 12 μm in the same zone of the set of the B casts. The results of the experimental determinations of the casts porosity levels and SDAS parameters were compared with the results of numerical simulations that were carried out in ProCAST software.

Specifying the Indicators of a Breeding Tape­Cassette Sowing Device for Sowing Grain Crops by Ears

A high efficiency of sowing grain crops by ears was noted in breeding and primary seed production. It was found that a seeder with working bodies for sowing by ears helps to significantly (up to 8 times) reduce labor intensity as well as maintain the variety purity in comparison with the use of manual labor.Research purpose To develop a seeder working section with a tape-cassette sowing device for sowing grain crops by ears in breeding and seed nurseries, and to substantiate the sowing device parameters necessary for the design of a multi-section grain seeder.Materials and methods In the course of the experiments, the authors proposed a schematic diagram, a program and a method for testing a cassette seeder working section for sowing by ears. A sample of the seed section was examined in the laboratory. The ways of ensuring the variety purity in conditions of grain natural shedding were studied. A technology of sowing ears in capsules was used.Results and discussion It was proposed to equip the seeder cassette sowing device with a device for pushing the capsule with the ear out of the cassette tape cell. A mock-up model of a spiked seed drill section was developed. The operation of the tape-cassette sowing device was checked.Conclusions The advisable parameters of the cassette tape cells specified are as follows: the inner diameter is 2.3-2.5 centimeters, the length is 14.0-16.5 centimeters, the distance between the axes is 3-4 centimeters. A formula for calculating the number of cells in a cassette tape was obtained depending on the number of tape turns in the cassette. The initial requirements and terms of reference were developed for the experimental sample of the grain drill section. The data were summarized to design a multi-section seeder for sowing with ears.

Optimization Design Based on I-GA and Simulation Test Verification of 5-Stage Hydraulic Mechanical Continuously Variable Transmission Used for Tractor

To improve the characteristics of a tractor power transmission system, make the transmission system not only meet the geometric principle but also meet the working speed requirements of the tractor, realize the continuous adjustment of the speed ratio, and solve the power interruption caused by the change of speed ratio. This paper not only proposes a new type of five-stage hydraulic mechanical continuously variable transmission (HMCVT), but also proposes a geometric design method based on I-GA. In this paper, the intersection position of each working section is introduced in the optimization design process, and six wet clutches, one brake and two planetary rows are used to achieve a flexible geometric design. The results show that the HMCVT proposed in this paper can effectively match the required speed of the tractor. After optimization, the transmission ratio characteristics are consistent with the target characteristics (the average error is about 3.27% and the common ratio is about 1.81); the simulation results based on Simulation X are highly consistent with the theoretical design values (the MAPE of 36 simulation experiments is about 0.72%); and the maximum speed of the tractor is 41.62 km/h. The proposed HMCVT design scheme and optimization design method provide a direct basis for the research and development of the composite power transmission system of tractors or other vehicles and agricultural machinery.