Mathematical Modeling of the Process of Reduction of the Material Consumption of Gas Transmission System Elements

The new method for a comprehensive assessment of the strength, durability and material capacity of the critical elements of the main gas pipelines, taking into account the combined impact of factors causing damage (environment, corrosion, random loading, geometry variation, material defects, etc.), which are changing the bearing capacity and material capacity of these structures, is proposed. As the main damaging factor, the process of corrosion fatigue is accepted, the qualitative and quantitative assessment of which are realized by applying a set of equations of comparable fatigue lines obtained by fatigue tests carried out in air and in corrosive environment. By the joint solution of these equations, the functions of the corrosion action coefficients are obtained in a wide range of cyclic strength and durability, which in standard calculation procedures are performed only for cyclic strength and only at the inflection point of the fatigue lines (NG 5  106 cycles).The issues of reducing the material consumption and ensuring the cost-effectiveness of structures, by using relatively cheap materials for pipelines - low-carbon and low-alloy structural steels subjected to surface hardening in stressed sections of pipes (edge welds) in order to significantly increase the physical and mechanical characteristics of the used steel grades are considered. In order to increase the corrosion resistance of these sections, contemporary polymer anticorrosive coatings are used.

Cyclic behavior of late quaternary alluvial soil along Indo-Gangetic Plain: Northern India

The A.D. 1803 and 1934 Bihar-Nepal border earthquake affected Indo-Gangetic Plain with evidences of liquefaction in cities like Patna, Varanasi, Agra, and Delhi in historical past. Recent strong shaking all along the Indo-Gangetic Plains and seismic induced damage to the buildings in Bihar during Mw 7.8 Gorkha earthquake raises the concern for site specific liquefaction potential estimation of alluvial soils. Cyclic triaxial tests were conducted on soil samples from Kanpur, Allahabad, Patna city to know the cyclic behavior, estimate the dynamic soil properties and the effect of relative density, confining pressure and frequency of loading on the cyclic behavior of the soil tested. The test results indicate the cyclic strength of Allahabad soil is less than Patna and Kanpur soil. The Allahabad soil with 80% sand, 10% silt and clay each is more prone to liquefaction than Kanpur soil (82% silt, 16% clay and 2% sand) and Patna soil (10% Kankar, 95% sand, 5% silt). This study indicates soils having sand with silt percentage are more liquefiable than clean sand or silty soil. It can be concluded that the soil of Allahabad and Patna city is more prone to liquefaction than Kanpur soil.

Fatigue Behavior of Laser-Cut Sheet Metal Parts with Brazed-on Elements

Laser cutting is used in the production of formed sheet metal components. However, the cyclic load capacity is reduced compared to other subtractive processes. Laser cutting results in a significant loss of fatigue strength; however, thermal joining has its own effect on the cyclic load capacity. Accordingly, brazing causes a significant reduction in the mechanical strength. However, the open question is what consequences a combination of both processes may have on the overall fatigue strength of sheet metals. Laser-cut samples of AISI 304 with and without a brazed-on element were investigated for their microstructure and mechanical properties. The brazing process was found to have an annealing effect on the microstructure. It was further observed that the fatigue behavior of brazed specimens is dominated by inhomogeneities at the surface of the filler metal fillet located in the geometric notch of the brazed joint. Fatigue strength decreased by almost 50% compared to as-cut specimens. As long as no shared diffusion zone is formed between the laser-cut and the brazed joint, the use of laser cutting for the production of such components appears to be reasonable and does not further contribute to the loss of cyclic strength.

Study, improvement and evaluation of electro-corrosion resistance of highly effective inhibitory compositions

The studies on the improvement of boron nitrogen-containing compounds, as well as information on phase transformations in the system H3BO3-C3H4N2-H2O, based on the solubility isotherms consisting of three branches, are presented. Based on the analysis of the second branch, a new boratimidazole compound was found. A full description of its properties is given. Furthermore, the paper presents the studies on the effect of boratimidazole and emidazole on the corrosive electrolytic behavior and the main characteristics of the cyclic strength of pre-eutectoid carbon steel in neutral media. It is found that the introduction of emidazole and boratimidazole into corrosive media reduces the ionization rate of steel, reduces the density of the anode current in the passive state region and increases the main characteristics of the cyclic strength of the metal. It has been shown that emidazole has a lower inhibitory ability than boratimidazole. The obtained experimental results of gravimetric studies, electrochemical changes and corrosion-fatigue tests are in good agreement with each other and with the previously obtained data. Boratimidazole is a quite effective corrosion inhibitor and can be used to protect ferrous metals and their alloys. The development of new effective, environmentally friendly corrosion inhibitors based on boron-containing compounds is an important scientific and technical task. To develop new compositions of anticorrosive reagents, the method of physical and chemical analysis, which is the scientific basis of modern materials science, is used in this work.

Dynamic, In-situ, Nonlinear-Inelastic Response and Post-Cyclic Strength of a Plastic Silt Deposit

This study presents the use of controlled blasting as a source of seismic energy to obtain the coupled, dynamic, linear-elastic to nonlinear-inelastic response of a plastic silt deposit. Characterization of blast-induced ground motions indicate that the shear strain and corresponding residual excess pore pressures (EPPs) are associated with low frequency near- and far-field shear waves that are within the range of earthquake frequencies, whereas the effect of high frequency P-waves are negligible. Three blasting programs were used to develop the initial and pre-strained relationships between shear strain, EPP, and nonlinear shear modulus degradation. The initial threshold shear strain to initiate soil nonlinearity and to trigger generation of residual EPP ranging from 0.002 to 0.003% and 0.008 to 0.012%, respectively, where the latter corresponded to ~30% of Gmax. Following pre-straining and dissipation of EPPs within the silt deposit, the shear strain necessary to trigger residual excess pore pressure increased two-fold. Greater excess pore pressures were observed in-situ compared to that of intact direct simple shear (DSS) test specimens at a given shear strain amplitude. The reduction of in-situ undrained shear strength within the blast-induced EPP field measured using vane shear tests compared favorably with that of DSS test specimens.

A parametric study on cyclic strength of coastal sand of Digha in West Bengal, India

Stress controlled cyclic triaxial tests have been carried out on coastal sand of Digha, West Bengal, India at different frequencies, confining pressures, relative densities and number of loading cycles for determination of influence of these parameters on cyclic strength (expressed in terms of cyclic stress ratio) and initial liquefaction of Digha sand. The test results provide evidence that increasing density of sand increases liquefaction potential, though it has been found that increase in effective confining pressure reduces cyclic strength of sand. Cyclic strength of sand decreases with increase of number of loading cycles at a specific density and a particular confining pressure. It has been observed that frequency of loading cycles does have any significant influence on the number of cycles for initial liquefaction of Digha sand. An empirical correlation has been developed on cyclic strength of sand based on these parameters and it has been found that this correlation fits quite well with the observed experimental results.

Trends of manufacture and the Russian market of metallic medical products

The article describes state of the Russian market of medical instruments and equipment, the volume of production, import and export of medical instruments based on metals, and assesses the import dependence on various market segments. The comparative analysis of domestic alloys and materials produced by foreign companies has shown that Russia has developed unique alloys and steels that have no analogues abroad, with improved indicators of corrosion resistance, wear resistance, static and cyclic strength. However, metallurgical products supplied to the medical industry do not always meet the quality requirements, and medical industry enterprises use imported types of metallic products. It should be noted that for medical purposes, lowtonnage production batches are required, which are associated with increased costs. The situation is aggravated by the fact that some of the enterprises that produced low-tonnage batches of special steels and alloys were completely liquidated. In this regard, it is necessary to create a specialized manufacture of such materials. Results of the analysis of the Russian market of special metals and alloys used for medical needs are presented, and ways to solve the problem of import substitution in this market are suggested.