Influence of thick-walled cylinders length on the residual stresses generated during the single-cycle mandrelling

The paper presents methodology and results of experimental study by Sachs method the effect of length of mandrelled thick-walled cylinders made of steel grade 50 (0.5% C) with 5 mm diameter hole, outer diameter of 15 and 25 mm on residual stresses. Based on the review of studies, it was noted that this effect may be both due to uneven process of mandrelling along the cylinder length and due to zero axial residual stresses on its faces. It was found that the length of cylinders has the strongest influence on axial residual stresses. With allowances between 0.9 and 7.1% and length reduction from 40 to 10 mm, the largest absolute value of axial residual stresses decreases from 210 to 50 MPa. It was noted that when the outer diameter of cylinders is 15 mm their length significantly influence on both hoop and radial residual stresses. With the above-mentioned decrease in cylinders length, absolute values of hoop and radial residual stresses in the region adjacent to the hole, depending on the mandrelling allowance, increase (from -135 to -205 MPa and from -45 to 55 MPa respectively, when allowance is 7.1%), decrease (from -315 to -235 MPa and from -135 to -95 MPa respectively, when allowance is 0.9%) and remain almost unchanged (when allowance is 3.4%). Impact of length on these stresses is weak when the outer diameter of cylinders is 25 mm

Feasibility of the Davidenkov method for investigation of hoop residual stresses in cold expanded cylinders

Cold expansion of holes in hollow cylinders is accompanied by raise of residual stresses in the bulk of the cylinder, the largest of which are hoop residual stresses. Since hoop residual stresses affect critical performance characteristics, assessment of their nature and magnitude is one of the most significant engineering tasks. The most wide spread mechanical methods to define magnitude of hoop residual stresses are G Sachs and N N Davidenkov methods. The paper presents result of experimental studies by Sachs and Davidenkov methods of hoop residual stresses generated in hollow cylinders made of carbon steel AISI 1050 after cold expansion. It is shown that the shape of curves of hoop residual stresses calculated by the mentioned methods, depending on the hoop residual strain generated on the outer surface of the cylinder, can differ (strain is elastic) or coincide (strain is elastic-plastic). It was established that the absolute values of the stresses defined by the mentioned methods in the area adjacent to the hole differ by an average of 15%, and in the area adjacent to the outer surface differ by an average of 20%

Classification of gas reduction valve silencers at TPP gas distribution points

Gas distribution points (GDP) at TPPs are sources of intense noise. Results of noise experimental measurements originating from TPP GDP demonstrate that the sound level at a distance of 10 m could reach 110 dBA. Gas reduction valves are the source of noise in GDP. Noise emission characteristic of the gas reduction valves depends on their geometric and design parameters. To reduce the noise propagating in a low-pressure gas pipeline from gas reduction valves, various types of noise silencers are used. This paper presents results of noise experimental measurements in the vicinity of the GDP buildings at various energy enterprises. Overview and classification of silencers by various manufacturers used at TPP GDPs are provided

A second addition to the Odonata fauna of Azerbaijan

This article contains new faunistic data on 53 Odonata species based on material collected by the authors in Azerbaijan between 2013-2014 and added by revising an old collection made by A.V. Bogachev in the 1930-1940s. Of these, 13 species are new for the country: Lestes dryas, L. sponsa, L. virens, Coenagrion hastulatum, C. lunulatum, C. ornatum, C. pulchellum, Aeshna affinis, Brachytron pratense, Cordulegaster picta, Somatochlora flavomaculata, Sympetrum flaveolum, S. vulgatum. The new locality of Cordulegaster picta is the easternmost for the species. Two new populations of a very rare species Cordulegaster vanbrinkae (discovered in the country in 2011) are found. Somatochlora flavomaculata and Brachytron pratense are generally very rare in the entire Caucasus. Pantala flavescens has been rediscovered in the country 100 years after the first record. A large population of Caliaeschna microstigma, a species very rare in Azerbaijan, has been found in the northern part of the country; it represents a peculiar dark morph whose features are described in detail. Particulary discussed are the variability of Coenagrion puella-complex in Azerbaijan and diagnostic features of two other Coenagrion species closely related to each other, C. ornatum and C. vanbrinkae

Sheet metal material resources management in lean production

Industrial enterprises are responsible for increasing production waste. The purpose of the research is to develop tools of material resources management in lean production for sheet metal cutting at engineering enterprises with single or serial types of production. At the previous stages of the research, a situational analysis of the cutting process was conducted, a literature review was carried out, and the main provisions of the sorting method of sheet metal material resources after cutting were defined for dividing them into groups of business or non-business material resources. The main provisions of the proposed method are specified in this article. Further research tasks are also identified

Two new species of Cordulegaster Leach, 1815 from Azerbaijan (Odonata, Cordulegastridae)

Two new Cordulegaster species are described and illustrated by drawings, photographs and SEM images. The first one, C. plagionyx sp. nov., was discovered in NW Azerbaijan in a low-mountain forest landscape; the second, C. nachitschevanica sp. nov., occurs in the subalpine zone of Nakhichevan AR, south of the main territory of Azerbaijan. Both new taxa look generally similar to C. insignis Schneider, 1845; however, each of them reveals unique features and distinctive combinations of characters that set them apart from other species of the genus. Both new species exhibits new types of sex dimorphism previously unknown in Cordulegaster. Some traits related to the structure of male appendages and important details of colouration prevent both C. plagionyx sp. nov. and C. nachitschevanica sp. nov., from being reliably classified under any of two widely accepted groups of species within the genus Cordulegaster: the boltonii-group and the bidentata-group

BIFURCATION ANALYSIS OF THE DYNAMICAL SYSTEM FOR A THREELAYERED VALVE WITH PERPENDICULAR ANISOTROPY

The features of switching dynamics in a model of a three-layered valve have been investigated theoretically and numerically. For this purpose, the system of ordinary differential equations in the approximation of the uniform magnetization distribution for the magnetization dynamics in the valve with perpendicular anisotropy was derived. It was shown that in such a system, in contrast with the system for the in-plane anisotropy, there are only two equilibrium positions of the magnetization vector. The stability analysis of the stationary points of the system has been carried out. With its help, the classification of types of dynamics versus field and current values was performed. The regions of limit cycles existence and the regions of optimal magnetization switching were revealed

BIFURCATION ANALYSIS OF THE DYNAMICAL SYSTEM FOR A THREELAYERED VALVE WITH PERPENDICULAR ANISOTROPY

The features of switching dynamics in a model of a three-layered valve have been investigated theoretically and numerically. For this purpose, the system of ordinary differential equations in the approximation of the uniform magnetization distribution for the magnetization dynamics in the valve with perpendicular anisotropy was derived. It was shown that in such a system, in contrast with the system for the in-plane anisotropy, there are only two equilibrium positions of the magnetization vector. The stability analysis of the stationary points of the system has been carried out. With its help, the classification of types of dynamics versus field and current values was performed. The regions of limit cycles existence and the regions of optimal magnetization switching were revealed