Effects of structural inhomogeneities on the steel balls resistance to loading

When conducting impact tests of protective glasses, nonunique cases of destruction of balls made of bearing steel ShKh15 were recorded. The causes of their destruction were determined. The state of the material was studied by fractographic and metallographic analysis, hardness and microhardness measurement. In the structure of the metal of all the balls, no critical defects were found such as flockens, shells and microcracks, but adverse factors were detected in the microstructure of the material, namely, the presence of fineneedle martensite with excessive carbides. It is established that the detected structural factors lead to liability to brittle fracture, an increase in the hardness of the material, a decrease in plasticity. To prevent brittle fracture of the balls and provide a reserve of plasticity of steel ShKh15 at high shock loads assessment calculations of ductility coefficient were made; and it was recommended to limit the maximum hardness of the material critical value HV=5.70 HPa (54 HRC), with the corresponding plasticity coefficient equal to 0.8.

Calculation of parameters of ecological plasticity and stability of oil sunflower varieties bred in VNIIMK

In 2016–2019 we studied ecological plasticity and stability by yield of five oil sunflower varieties. Estimation was conducted by two different methods that allow studying in details sunflower varieties by this trait. Calculation made due to S.A. Eberhart and B.А. Rusell’s method that all studied genotypes possess high ecological plasticity (coefficient of linear regression > 1). The variety Master appeared to be the most plastic (bi = 2.0). The varieties Skormas and SUR (С. 855) are the most homeostatic; their mean-squared deviation coefficients are 11.9 and 14.1, respectively. When cultivation conditions are worsened technological qualities of these varieties will be kept without any significant changes. Studying of parameters of adaptability due to R.A. Udachin’s method showed the variety Skormas is stable one, having a coefficient of resistance of stability index (R) equal to 42.9%. Less stable are the following varieties: Umnik (coefficient 25.7%), R-453 (Rodnik) – 1.9%; С. 855 – 33.2%. Calculations for the sunflower variety Master appeared to be statistically unreliable. According to our calculation of a parameter of ecological plasticity, the most responsive on improvement of cultivation conditions is the variety Master, having an intensity indicator (I) equal to 20.1%. The variety Skormas 32 with a coefficient I = 9.7% is less plastic in a range of the studied genotypes.

SPRING GRAIN QUALITY OF OMSK OAT VARIETIES IN THE EXTREME ENVIRONMENTAL CONDITIONS

The authors make a case that oat selection should have profound focus in the regions with profound contrasting weather conditions such as Western Siberia is. The adaptive variety has environmental plasticity and combines stable high productivity with grain quality. The researchers study a set of varieties of oats under the conditions of the southern forest-steppe zone of the Omsk region according to the parameters of environmental adaptability, estimated on the basis of protein concentration pro a unit of land. The experimental part of the work was carried out during 2013-2018 on the experimental fields of Omsk Research Agricultural Centre (Southern Forest Steppe, Omsk). The protein concentration in the oat grains was determined according to the Pleshkov’s method. On average, the protein concentration in chaffy oat and Hulless oat didn’t vary significantly and was equal to 408.8 and 407.4 kg/ha, respectively. Protein concentration standard of Tarsky 2, Uran, Fakel and Sibirskiy Gerkules varieties exceeded the average by 14.1-71.5 kg/ha. The authors estimated the following adaptability parameters: stress resistance (Ymin-Ymax) and compensatory capacity (Ymin+Ymax)/2 according to Rossielle, Hemblin method; ecological plasticity coefficient (O) – according to Baransky methodics; variation coefficient (V) and equation coefficient (B) – according to Armor; the level of variety stability - according to Nettevich method; coefficient of responsiveness to favorable conditions of cultivation (Kr) - by Zykin; environmental plasticity index (EPI) – by Gryaznov; coefficient of adaptability (CA) - by Zhivotkov. A comprehensive assessment of spring oats varieties, taking into account a smaller number of ranks, identified the varieties, most adapted to high protein concentration in the southern forest-steppe zone of the Omsk region: a standard chaffy variety Orion, Uran (total ranks were 37 and 36), as well as the standard of hulless oat group which is Sibirskiy golozernyy (total ranks are 72).

Response of oil flax varieties to abiotic conditions of the Middle Cis-Ural region by formation of seed yield

Studying the reaction to the abiotic conditions of the Middle Urals in 16 varieties of oil flax will allow to adapt the culture: increase its productivity and product quality. As a standard, the variety ‘VNIIMK 620’ was sown. The experiments were laid on sod-podzolic medium loamy soil in the grain-grass rotation after winter crops during 2012-2015. During the years of research, the plow layer of the experimental plots had different humus contents - medium and high, mobile phosphorus and exchange potassium - medium and very high, exchange soil acidity - slightly acidic and close to neutral. To a greater extent, by 91.5%, the change in the seed yield of the studied oil flax varieties depended on the abiotic conditions of the growing season; the share of the influence of the genotype of the variety in the formation of seed yield was 3.0%. Meteorological conditions during the years of the experiments were characterized by large fluctuations in the average daily air temperature and the amount of precipitation that fell over the months, in consequence of this the seed yield of flax oil varied in wide range over both varieties and years of study. The most favorable abiotic conditions for the formation of oil flax seeds were formed in 2014, when, during the ripening period of the seeds optimal meteorological conditions have developed with hydro thermic factor of 1.0. This contributed to obtaining the highest seed yield in 2014 - 218 g/m2. On average, over four years of research, the same response to abiotic conditions with seed yield was formed in ‘VNIIMK 620’ varieties from Russia, ‘Clark’ varieties from Holland and ‘Barbara’ from Hungary. The most plastic grade is ‘Clark’ with a plasticity coefficient bi = 1.33. The most stable seed yield is the ‘Norlin’ variety with a stability coefficient of 32.2. Russian varieties ‘LM-96’, ‘N 3829’ and foreign varieties ‘Norlin’, ‘Atalante’ proved to be the most adaptable to cultivation conditions in the agroecological conditions of the Cis-Ural region and can be considered promising in terms used as starting material in the breeding process.

Mathematical Modeling on the Residual Stresses in Coatings Due to Heat Treatments

Coatings are implemented on engineering metals and alloys to augment the surface properties such as hardness as well as resistance to wear and corrosion. Heat treatments of coated metals/alloys are performed to aid in the progress of the bonding of the coatings to the substrate. During the air cooling process, the difference in the compositions of the coating and the substrate materials causes them to cool at different rates, which leads to straining in them. The paper presents the research on the mathematical investigation to evaluate the residual stresses in coatings caused due to heat treatments and subsequent air cooling. The mathematical modelling is executed to formulate the equations to represent the residual stresses retained in the coatings due to the heat treatments and subsequent air cooling. Air cooling undergoes two stages namely the initial quenching phase and the final cooling phase. During the quenching phase, the strain was expressed by considering the elastic, plastic and thermal strain components. Poisson’s ratio, deviatoric stress differential of the modulus of plasticity, coefficient of thermal expansion and change in temperature are used to express the elastic, plastic and thermal strain components. During the final cooling phase, the strain was expressed by considering only the elastic and thermal stain components, as the plastic staining the coating material generally does not occur during the final cooling phase and occurs only during the initial quenching phase. From the strain components, the residual stresses for the coatings in the x, y and z axis were formulated. Thus, the total residual stress is the sum total of stresses caused during the initial quenching phase and the final cooling phase.

Viability of turbine blade material with a long service life

This article deals with structural features and characteristic changes that affect the mechanical characteristics after different service life in real conditions using the example of the blades of the 4th stage of turbine GTE-45-3 with an operating time of 13,000 to 100,000 hours. To study the change in the state of the material under different operating conditions, determine the degree of influence of heat treatment on the regeneration of the microstructure, and restore the mechanical characteristics of the alloy after different periods of operation, non-standard methods were used: relaxation tests on miniature samples to determine the physical yield strength and microplasticity limit and quantitative evaluation of the plasticity coefficient of the material from experimental values of hardness, which allow us to identify the changes occurring in the microvolumes of the material and predict the performance of the product as a whole.

DEFORMATION OF HORIZONTAL JOINTS’ MORTAR OF MASONRY UNDER COMPRESSION

The necessity of establishing and determining the consistency of mortars deformation in the horizontal joints of masonry is established: in the absence and development of cracks and with the exhaustion of resistance ranging from 80 – 85 % of the total deformation of masonry under short-term compression. Attention is paid to the absence of reports in the scientific literature on the conduct and results of research on the spatial stress-deformative state of the mortar in the joints of masonry under compression. The advantages of studying the secant modulus of deformation Ep are emphasized in solving various issues in the theory of operation and method for calculating the masonry. On the basis of long-term research results, the essential difference between the change in the secant modulus of cement mortars deformation E'p of varying strength of horizontal joints from the nature of its change when tested in standard samples is shown analytically and graphically. The advantages of the developed methodology for processing the results of investigations of mortars in standard samples are noted. It allows to more accurately set the actual values of normal strain modulus E0 and the ultimate relative deformation under compression. The analytical dependences of the plasticity coefficient and the secant modulus of deformations E'p are found based on processing the results of numerous studies of masonry mortars

Study on Mechanical Properties and Damage Evolution Law of Secondary Destruction Induced by Simultaneous Unloading after the Peak of the Curve of Sandstone

The research adopts the French ROCK600-50 three-axis experiment instrument and SH-II system to evaluate the acoustic emission (AE) peak of the rear axle of yellow sandstone by carrying out the confining pressure synchronous unloading experiment, and evolution of mechanical properties and characteristics of energy transformation and damage of a yellow sandstone, which is a two-damage process, the results of which have shown the following: (1) there are two damages appearing when the confining pressure is 5 MPa, 10 MPa, and 20 MPa. In contrast, these two damages do not appear when the confining pressure is 30 MPa and 40 MPa. The fracture degree and crack number of the two fractures are larger than those without two damages. (2) A failure stress release rate showed an obvious “√” trend. With the increase of confining pressure, the stress release rate of the two failures is increasing. (3) By keeping the strain of the body constant, it is determined to be the first time to destroy the warning. The two failures of rock are predicted by the inflection point of the axial strain slope. No two failures occurred, and the strain unloading process showed two characteristics. (4) Meanwhile, with the increase of confining pressure, the energy released from the peak decreases first and then increases; the law of releasing energy from one failure and two destructions is the opposite. No damage occurred two times. As the confining pressure increases, there is a continuous decrease of the energy released from the peak. As the confining pressure increases, the release rate of the primary energy decreases at first and then increases, and the rate of energy released two times is increasing. The plasticity coefficient shows the trend of increasing first and then decreasing. (5) The damage degree of the second rupture is greater than the first rupture.