Low Climatic Temperatures Research Articles

36 Effects of grinding method on ileal digestibility of amino acids in different short-season corn cultivars fed to growing pigs

Abstract Decreased corn production was previously observed in Manitoba due to the low climatic temperatures; however, corn production has increased by developing corn hybrids that require low corn heat units, and therefore can grow in areas with decreased heat units. Milling technology affects feed particle size and shape, which may affect the digestibility of nutrients and growth performance of pigs. Therefore, this study aimed to determine the effects of grinding methods on the apparent (AID) and standardized (SID) ileal digestibility of amino acids (AA) in selected short-season corn cultivars fed to growing pigs. A total of 18 ileal cannulated barrows (56.8 ± 2.9 kg) were assigned to 1 of 6 dietary treatments in a triplicate 6 × 2 incomplete Latin square design with 6 diets and 2 periods to give 6 observations per treatment. Dietary treatments were arranged in a 3 × 2 factorial design with three different corn cultivars [two Manitoba-origin short-season corns (A or B) or a US-origin corn] and two grinding methods [hammer mill or roller mill]. Each ingredient was included as the sole source of protein in the diets. All diets contained 0.3% titanium dioxide as an indigestible marker. Each experimental period lasted 7 d including the first 5 d for adaptation and the last 2 d for ileal digesta collection. After feeding the experimental diets, all pigs were fed a low-protein diet for 7 d to quantify endogenous losses of N and AA for determining the SID of N and AA. Pigs were fed the diets at 2.8 times the maintenance energy requirement based on their body weight at the beginning of each period. Data were analyzed using the PROC MIXED of SAS. The statistical model included diet as fixed effect and replication, animal within replication, and period within replication as random effects. The AID of Arg, Ala, Ser, and Gly were greater (P < 0.05) in short-season corn B compared with US-origin corn. The AID and SID of His in both short-season corns were greater (P < 0.05) than in US-origin corn. The AID of His and SID of Thr in hammer-milled corns were greater (P < 0.05) than in roller-milled corns. A significant interaction was found whereby AID of Ile in hammer-milled corn was not different between short-season corn B cultivar and US-origin corn but in roller-milled corn, short-season corn B cultivar had a greater (P < 0.05) digestibility than US corn. In conclusion, the digestibility of AA was greater in short-season corn than in US corn, and pigs had greater digestibility of AA in hammer-milled corn than roller-milled corn.

СВОЙСТВА И ФАЗОВЫЙ СОСТАВ ЦЕМЕНТНЫХ РАСТВОРОВ

Introduction of complex antifreezes based on calcium formate, calcium chloride and superplasticizer Polyplast SP-1 into cement masses leads to changes in the phase composition of cement mortars. Of great importance are the developments of complex modifiers that are used for the hardening phase of cement-crushed mixtures, especially at low temperatures (down to –20 °C). The phase and structural characteristics of cement mortars have not been sufficiently studied. In this regard, the work investigated the effect of complex antifreeze additives on the properties and phase composition during the structuring of cement masses. Compressive strength reaches its maximum value (44.8 MPa) with the addition of calcium formate, calcium chloride and superplasticizer to the composition of cement pastes. X-ray diffraction analysis was carried out using a DRON-3 diffractometer. The used methods were standard. The X-ray diffraction patterns of the samples prove the high intensity of reflections of calcium hydrosilicate d = 9.69 Å, portlandite d = 4.921 Å, d = 2.632 Å, which indicates a high degree of hydration of portland cement. The combined use of calcium formate and calcium chloride promotes the activation of hydrolysis, and the addition of superplasticizer SP-1 leads to a decrease in the water-cement ratio to 0.20, which leads to an acceleration of the hardening process. Complex antifreeze additives increase the percentage ratio of crystalline phase to amorphous phase, thus, cement pastes with complex additives of 6 % (HCOO)2Ca, 3 % CaCl2, 2 % SP-1 have the highest value of degree of hydration (0.70) due to the formation of 63 % crystalline phase. Newly formed structures are typical for portlandite and dicalcium hydrosilicates. Complex antifreezes as an additive promote the activation of hydration in cement mortars, and the level of the degree of hydrolysis and the integral value of mass loss confirm this. Synergism of structure formation processes is observed at joint use of antifreeze additives in the composition of cement masses and, as a result, increases the strength of cement mortars used in construction at low climatic temperatures.

Time series modeling of spring failures of KAMAZ trucks during operation in Yakutia

The purpose of this article is mathematical modeling of the time series of failures of leaf springs of KAMAZ trucks during operation in Yakutia to determine the relationship between the rhythmological features of the series and the operating conditions in the permafrost zone. Significant harmonics of the expansion of the time series of spring failures into a Fourier series were revealed. Harmonics with periods of 12 and 6 months are associated with the seasonal nature of operating conditions. The additive model, consisting of the average monthly value of failures and five significant harmonics, approximates the dynamics of spring failures quite well. The maxima of the additive function of spring failures occur in March—April and August—September, that is, they correspond to periods of deterioration of road conditions in Yakutia. The role of road conditions as a more important destructive factor affecting the operability of KAMAZ truck springs in the permafrost zone compared to the factor of low temperatures was also shown. The novelty of this work is determined by the contribution to the solution of methodological issues of studying the operability of vehicle elements, taking into consideration seasonal operational factors and ranking their role in the occurrence of failures. The resulting models will make it possible to make short-term forecasts of the dynamics of spring failures based on the choice of significant harmonics of the Fourier decomposition. Keywords KAMAZ truck, mathematical modeling, leaf spring, operability, periodicity, low climatic temperatures, road profile

Effect of the Weld Deposit Thickness on the Impact Strength of Heat-Affected Zone of the Welded Joint

The methodology has been developed to show the functional connection of the impact strength of the heat-affected zone metal of welded joints with weld deposit thickness and, accordingly, with the consumption of welding materials during electric arc welding while constructing and repairing various metal structures and pipeline systems operating in conditions of low climatic temperatures. To reach the objective of the paper, rational intervals of cooling rates of the HAZ metal during welding low-alloy pipe steels were used, and the calculated dependences from the existing works were modified. The methodology allows increasing cold resistance of welded joints of steels of mass use by regulating the weld deposit thickness and welding consumables during electric arc welding while constructing and repairing various metal structures and pipeline systems operating in extreme conditions of the North.

Aging of Structural Materials Modified with Polymer Additives in Cold Climate Conditions

Currently, one of the main materials for the construction of buildings and structures is concrete. Improving the performance of concrete is a priority of modern scientific research. Low climatic temperatures, frequent transitions through zero degrees in the autumn-spring seasons, and other aggressive factors have a significant impact on the mechanical and operational properties of structural materials. This work presents the experience of modifying heavy concrete M200 with polymer additive Amokor KM. In the process of two summer field tests, there were obtained data on the persistence of the strength characteristics of the material at test temperatures of-60 and + 20, fractographic studies of the initial and aged samples were carried out, as a result, it was found that the modification positively affects the durability of concrete M200. Additional protective staining increases the durability of the tested materials. Keywords: concrete, strength, composite, compression, modification, durability, fractographic studies.

Analysis of operation of Volvo FH12 vehicles in Yakutia conditions

The article considers the scientific concept of the theory and practice for the study of the automotive equipment’s reliability in the extreme conditions of a cold climate. On the basis of a large statistical material collected in the data bank on the performance of equipment in the conditions of the sharply continental climate of Yakutia, the issues of reliability of Volvo FH12 vehicles operated at the low climatic temperatures are considered. Questions on the change in reliability with an increase in vehicle mileage are considered and a forecast is made of the economically optimal service life of imported Volvo vehicles. The proposed calculation methods for predicting reliability make it possible to compare the optimal service life of various brands of trucks operated in real conditions of a cold climate, which will allow transport enterprises to complete a fleet that is most adapted to work in the North. Keywords: vehicles, reliability, performance, service life, mileage, cold climate, forecast

Study of wear of contact surfaces of powder coatings and steel counterbodies under sliding friction at low climatic temperatures

The article presents the results of measuring the thermophysical data of friction units "wear-resistant coating — steel counterbody" under conditions of low climatic temperatures. The temperatures of friction pairs at various stages of wear during friction in cold and room conditions are determined. The mechanisms of wear of friction surfaces under various wear test conditions are established.

Investigation of Wear of Modified Powder Coatings under Sliding Friction at Low Climatic Temperatures

Investigation of Wear of Modified Powder Coatings under Sliding Friction at Low Climatic Temperatures

Use of climatic cold in scientific research

A review of scientific research data on the use of climatic cold carried out on the basis of institutes of the Federal research center «Yakut Scientific Center» Siberian Branch of the Russian Academy of Science is presented, natural low temperatures being used both as testing conditions and as a tool for experimental studies. The results of full-scale hydraulic tests of pressure vessels and pipes under conditions of low climatic temperatures, and under internal pressure created due to the effect of ice formation in closed cavities are presented. The results made it possible to determine the limit states of large-diameter pipelines, simulate the stress-strain state of the pipeline in thawed, freezing and frozen soils, substantiate the extension of the lifetime of pressure vessels, develop a technology for their welding, and determine the allowable size of defects in welded joints. It is shown that climatic tests of polymer, composite, construction, welding and other classes of materials provide for estimation of their service life under the impact of climatic factors. An experimental study of the response of solids to multiple collisions with ice granules at low climatic temperatures has been carried out along with the study of the processes of brittle fracture of their surface with the formation of splintery particles. Study of the effect of fibrous fillers of natural origin on the strength properties of fresh-ice based composition material revealed that introduction of fillers increases the strength characteristics of fresh ice by 2 – 3 times. It is shown that climatic features and a significant scientific potential of the Sakha (Yakutia) Republic provide for effective use of climatic cold as a tool for scientific research and solution of engineering problems in various sectors of the national economy.

Adhesive and impact strength of hybrid layered metal-polymer composites reinforced by basalt fiber

This work shows the possibility of obtaining hybrid layered metal-polymer composites based on low-carbon steel and aluminum alloys with interlayers of basalt fiber reinforced thermoplastic polymer — polyetheretherketone by methods of hot and cold bonding with the use of hot and cold curing adhesives, respectively. The adhesive tear and shear strength of composites obtained by two alternative methods and the impact strength of steel-polymer and aluminum alloy-polymer joints were evaluated. The tests of five-layered composites for impact bending on samples with “crack-arrester” type V-notch (with the orientation of the notch line across the composite layers) at temperatures of −60, +20, and +200°С were carried out. The analysis of the test results showed that the composites have increased strength at shear loads and resistance to brittle fracture at low climatic and high working temperatures. Fractographic analysis of the fracture surface of composites allowed to determine that the fracture proceeds through adhesive, cohesive, and mixed mechanisms. Cohesive fracture is initiated in the polymer layer by nucleation and crack growth along the fiber-matrix interface, as well as cracking of the basalt fibers.

Термомеханические факторы прочности, ресурса и трещиностойкости сварных соединений в условиях низких климатических температур

It is shown that solving the problems of design, fabrication and operation of the complex engineering structures is associated with the need for scientific and technological substantiation of the strength, durability, and crack resistance of the critical welded joints of their load-bearing parts, especially under the conditions of low climatic temperatures in Siberia and the North. Basis of such solutions are the results of the analytical, numerical, and experimental studies in such key areas as thermomechanical, thermochemical, diffusion, structural and mechanical features of the formation of a welded joint, including the geometry and structural inhomogeneity of welds and zones near the weld, stress concentration, presence of the defects and deformation level, residual welding stresses, as well as the kinetics of stress-strain states in the zones of the welded joints. It is noted that for ensuring and improving performance of the structures, machines, and equipment in the northern modification with the use of welding, a large complex of research, development, design, control, diagnostic, supervision, and commissioning work was developed and implemented. Among them are the creation of new structural materials with an increased level of cold resistance and the development of new welding materials, technological processes for welding and subsequent treatments with ensuring uniformity of the local mechanical properties.

The Dissolution of Olivine Added to Soil at 4°C: Implications for Enhanced Weathering in Cold Regions

Crushed olivine was added to a soil core to mimic enhanced weathering, and water was continually dripped through for ~6 months. Our experiments were conducted at 4°C, and are compared to previously run identical experiments at 19°C. Olivine dissolution rates in both experiments start out similar, likely due to fines and sharp crystal corners. However, after >100 days of reaction, the dissolution rate at 4°C was two orders of magnitude lower than at 19°C. The accumulation of heavy metals, such as Ni and Cd, was low in both experiments, but soil retention of these elements was proportionally higher at higher temperatures, likely due to enhanced sorption and formation of clays. Overall, this study suggests that olivine dissolution rates in experiments that mimic natural settings are orders of magnitude slower than in normal laboratory experiments, and that enhanced weathering may be a considerably less efficient method of carbon dioxide removal at low climatic temperatures. Both of these conclusions have implications for the application of enhanced weathering as a CO2 removal method.

Study of microgeometry of contact surfaces of powder coatings and steel contact surfaces under sliding friction in cold conditions

This article discusses the changes in the operating temperature of friction and the patterns of formation of the microgeometry of the contact surfaces of modified powder coatings and steel counterbodies during sliding friction under conditions of low climatic ambient temperatures. Comparative studies of the roughness parameters of friction surfaces “powder coating — steel counterbody” during wear tests at room and low climatic temperatures are given.

Сопротивление хрупкому разрушению и демпфирующие свойства слоистых металлополимерных композитов

One of the topical trends in modern materials science is the development and study of new layered metal-polymer composites, which are increasingly used in aerospace engineering, automotive and transport engineering. The metal base of these composites provides a high level of strength properties and impact strength, and the polymer interlayer allows obtaining high damping properties due to its ability to dissipate the energy of elastic vibrations. Of a considerable practical interest is one of the varieties of metal-polymer composite materials based on a sandwich structure — layered steel-rubber composite characterized by pronounced viscoelastic properties, which allows them to be used as vibration damping elements in transport systems. In this work, the possibility of obtaining promising layered metal-rubber composites based on low-carbon steels (Fe-2Mn-1Si steel, IF steel), aluminum alloy Al-Mg3 and heat-and-frost-resistant rubber V-14-1NTA by hot pressing is studied. The influence of the composition and design of composites on the impact strength at temperatures of 20 and −60°C and the damping ability characteristics of materials such as the tangent of the angle of mechanical losses (tg δ), the modulus of elasticity (E') and the modulus of viscosity (E'') are determined by the method of dynamic mechanical analysis. The possibility of using layered metal-rubber composites with increased resistance to brittle fracture in the region of low climatic temperatures, as well as in structural elements of transport systems with high vibration resistance is shown.

Geotechnical Monitoring of Pipeline Systems Operating Under Conditions of Permafrost (Yakutia)

Life safety on the territory of the Republic of Sakha (Yakutia) is directly related to the uninterrupted supply of energy and heat, which is caused by low climatic temperatures. Even in Central Yakutia, the average period of temperatures below 0° C is about 210 days, below −20 ° C - 138 days. The minimum temperature is distributed in the range from −47.8 ° C to −60.3 ° C. Under such natural conditions, the release of any object in gas and heat supply chain leads to disastrous consequences. In the year at gas and heat supply facilities, several dozen emergencies of varying severity are recorded, mainly in winter period. The system of oil and gas pipelines laid on the territory of the Republic of Sakha (Yakutia), mostly located in the permafrost zone, is affected by dangerous geological processes, which significantly affects its reliability and safety. For stable operation of oil and gas complex (OGC) of the Republic, an assessment of pipeline state system, based on geotechnical monitoring, is necessary. The monitoring system provides heterogeneous data, the analysis of which helps to clarify the interaction between pipeline and permafrost in various geological conditions, and allows you to evaluate and predict the condition of objects and environment.

Wear tests of modified powder coatings at low climatic temperatures

The results of comparative wear tests for sliding friction of modified powder coatings with metal counterbodies at room and low climatic temperatures are presented. For this, a special stand has been developed and manufactured for testing the wear of powder coatings in conditions of low climatic ambient temperatures. The temperature of the friction pairs "powder coating — metal counterbody" and the profiles of the friction surface of coatings and counterbodies were measured.

Analysis of the reasons for the accelerated failure of oil pipelines in the regions of the Far North and Siberia

From about the time trends of development of oil gas complex of the country requires reassess the reliability and durability of pipelines for various purposes. The reason for this trend is the gradual displacement of the producing provinces towards regions with extremely low climatic temperatures, difficult natural conditions, and highly aggressive components of the oil production. Analysis of the reasons for the accelerated destruction of pipes in the northern regions of the country made it possible to identify two main causes of failure. This is the development of corrosion- mechanical defects and insufficient cold resistance and crack resistance of materials at low climatic temperatures. The paper analyzes the role of non-metallic inclusions in increased defectiveness of steel X70 pipes, an analysis of the influence of the microstructure and non-metallic inclusions of operation the pipes in cold climate.

Elaboration of standards and quality of railway rails

Russian national standards for rails establish technical requirements, acceptance rules and quality control methods. These are very important to ensure the quality and service durability of rails. Requirements for rail production variation within a period from 1960 to the present considered, peculiarities of their accounting in the standards shown. It was demonstrated that stricter requirements to rails resulted in the development of new steel compositions, the creation and introduction of new technological processes in steel production, rail rolling and heat treatment, as well as new methods of production quality control. Basic technical requirements for rails produced according to the national standard of theRussian Federationand to the European Norm presented. It was pointed out that the current national standard GOST R 51685‒2013 was elaborated accounting the requirements of the latest foreign standard EN 3674-1:2011+A1:2017. However, the former is not equivalent to the latter because it pertains to Russian rail types and contains requirements corresponding to the Russian climatic and geographical conditions, as well as the track facilities system used by OJSC RZD. It was shown that rails, meeting the current standard requirements, in terms of operational resistivity exceed the resistivity level of best foreign analogues. At present, a new standard is being elaborated accounting the need of increasing the service life of railway rails under conditions of high load, low climatic temperatures, higher-speed combined train operation and high-speed running, and high working capacity. The list of key issues presented, that are mirrored in the new standard draft, which accounts for the goal of mastering new rail categories and the increased requirements of OJSC RZD to rails quality.

On the disperse acicular ferrite formation in the structure of cold-resistant joints under temperatures up to –70°С in MMA welding of 10KhSND steel. Part 1

The article presents an analysis of the metallurgical techniques that provide high quality electrodes for manual arc welding of low-carbon low-alloyed cold-resistant steels. It is shown that it is possible to improve technological and operational properties of welded joints at very low climatic temperatures up to –70°C implementing micro-alloying of the weld metal with nitrogen, titanium, cerium oxide and diamond nanopowder produced by detonation synthesis. The composition introduced into the electrode coating modifier mixture is identified. The cumulative effect of its components on the weld impact strength under temperature testing within the range from –20 up to –70°C was established. The matrix of the weld metal is composed mainly of disperse acicular ferrite, hardened by nanoparticles allegedly nitrides and carbonitrides of titanium and aluminum. It is shown that the centers for the crystallization of acicular ferrite are micro-sized non-metallic inclusions formed on ultrafine titanium nitrides. It was revealed that the toughness of the weld metal at low climatic temperatures is higher than toughness of joints welded by massively imported Japanese KOBELCO electrodes LB-52U. The results of the study make it possible to increase the cold resistance of welded structures for petrochemical plants and other facilities located in the Extreme North of the Russian Federation.Part 2 of the article will be devoted to the study of the welding and technological properties of coated electrodes.

Experimental study of micro-deformation of structural steel under simulation of operating conditions

Diagnostics of the load bearing capacity of machines and structures, service properties of structural materials are carried out by destructive and non-destructive methods. In the system of non-destructive methods of diagnosing and monitoring of the service properties of materials and products, radiation technologies are of particular importance, since they have instrumental capabilities for diagnosing and controlling changes in the soundness of a solid body at different structural levels. The X-ray diffractometry method provided determination of the stability of the stress-strain state of structural steel samples subjected to prolonged (over 5 years) static loads not exceeding the yield strength of the material. The purpose of the study is to determine experimentally the effect of continuous (since 2013) elastic stress and climatic factors on the change in the half-width of the diffraction line profile. It is shown that the straight-line dependence of the half-width of the diffraction line profile is maintained in the range of elastic stresses not exceeding 0.5σt. The results of changes in the microstructural state (micro-strains) identified by the characteristics of the diffraction lines profile are presented and discussed. The results of the experimental study of the effect of small steady elastic stresses reveal that periodic annual fluctuation of temperatures (2013 – 2018) does not cause a significant change in the properties of the diffraction line profile of the 08ps structural steel samples. On the contrary, low climatic temperatures contributed to the elimination of individual instrumental errors attributed to design conditions of the experiment. A sharp change in the true half-width of the diffraction line profile at the stress values σ > 0.5σt, probably indicates the minimum margin of safety of 08ps structural steel when setting the permissible stress value (σ). The revealed changes in microplastic deformation observed in structural steels in the range of elastic stresses corresponding to real operational loads require further study and analysis.