Mechanism of Secondary Deformation of Extruded AZ31 Magnesium Alloy by Viscoplastic Self-Consistent Model

The viscoplastic self-consistent (VPSC) model is used to establish a combination of different deformation mechanisms. By using this model, axial tension and compression tests of extruded AZ31 magnesium alloy at room temperature are simulated. The influence of secondary deformation mechanism (prismatic <a> slip, pyramidal <c + a> slip, and 101¯1 compression twin) on mechanical response and texture evolution is expounded. Increased activity of the prismatic <a> slip is conducive for the improvement of flow stress in mechanical response during axial tension and for the splitting of pole densities in the {0002} pole figure during axial compression. However, increased activity of the pyramidal <c + a> slip causes the basal texture to transfer to the extrusion direction in the {0002} pole figure during axial compression. The 101¯1 compression twinning has a negligible influence on the plastic deformation and mechanical response of AZ31 magnesium alloy during axial tension and compression. However, the 101¯1 compression twinning should be included in VPSC modeling to predict the texture evolution accurately.

THE WAYS OF IMPROVEMENT OF THE METHODS OF HYPOSPADIAS TREATMENT IN CHILDREN: LITERATURE REVIEW

The relevance of the study is due to the fact that hypospadias is a congenital defect of the urogenital system in boys. The incidence rate of hypospadias differs in different countries. The main etiological factor of this defect development is a hormonal imbalance of different origin in mothers. Hypospadias can be corrected only surgically. Currently, there are a number of surgical approaches used, but still, the number of complications in the postoperative period remains high. The purpose of the article was to evaluate the outcomes of surgical correction of hypospadias in children observed after different approaches to urethroplasty involving transplanting. The authors performed a search for articles in electronic databases Pub Med, Elsevier, Scopus, Web of Science for the period from 2007 to 2018. The authors reviewed 265 articles dedicated to the correction of hypospadias by the following methods: TIP (tabularized incised plate), Mathieu, GTIP (graft tabularized incised plate) and two-stage Bracka urethroplasty. The most widespread complications mentioned in different studies were fistulas, stenosis of the urethral neo-meatus, and secondary deformation of the penis. Current approaches to surgical correction of hypospadias in children do not provide complete recovery from post-operative complications. Due to this fact, the issues of treatment of hypospadias remain relevant, requiring the development of new approaches to urethroplasty.

Numerical Investigation of Secondary Deformation Mechanisms on Plastic Deformation of AZ31 Magnesium Alloy Using Viscoplastic Self-Consistent Model

Uniaxial tension and compression of AZ31 magnesium alloy were numerically investigated via the viscoplastic self-consistent (VPSC) model to shed a light on the effect of secondary deformation mechanisms (prismatic <a> slip, pyramidal <c+a> slip, and { 10 1 ¯ 1 } contraction twinning) during plastic deformation. The method adopted in the present study used different combinations of deformation mechanisms in the VPSC modeling. In terms of the pyramidal <c+a> slip, it served as the first candidate for sustaining the extra plastic strain during the plastic deformation. The improvement of activity in the pyramidal <c+a> slip contributed to the increase in the mechanical response and the splitting of pole densities in { 0002 } pole figure during uniaxial tension. As for the prismatic <a> slip, its increasing activity was not only conducive to the improvement of flow stress in mechanical response, but also responsible for the splitting of pole densities in { 0002 } pole figure during uniaxial compression. With respect to the { 10 1 ¯ 1 } contraction twinning, it had a negligible influence on the plastic deformation of AZ31 magnesium alloy in terms of the mechanical response as well as the slip and the twinning activities. However, it is better to include the { 10 1 ¯ 1 } contraction twinning in the VPSC modeling to more accurately predict the texture evolution.

Horizontally deplacement geomasses in the continental rift geostruсtures (on the example of the Dnipro-Donets paleorift). Part 2. Structural parageneses of the reid deformation of the sedimentary cover

Formulation of the problem. The inversion stages of the structural-material evolution of the continental crust are characterized by regional scale of the deformation of volume tectonic flow of platform sedimentary rocks, which caused significant horizontally-healthy movements of tectonically activated geo-mass in the intra-plate graben-rift. The dynamic deformation of geomases manifests itself at the final stages of the geological development of such structures; therefore, it determines the main features of the systemic organization of the modern architecture of the basement and sedimentary cover complexes. Review of previous publications and studies. Secondary deformation linear slope, according to Patalakha E. (1979); Alekseev V. (1990) is considered as a set of local strike-slip zones, formed on spherically-located viscous faults, forming joint tectonic flows. The structural skeleton of tectonic flows, as the basis of the tectonic dislocation process, make offsets with the horizontally and rotational component movements. Horizontal landslides are typical disjunctive elements of the continental structures formed in the geodynamic conditions of the transtension (grabens, rifts), transpression (folded mobile belts, intra-plate activation zones), as well as the basic structural elements of the strike-slip tectonics of the sedimentary basin. The purpose of the article. The second part of the trilogy continues regional geotectonic studies of post-rift complications of the sedimentary cover structure of Dnipro-Donets Paleorift (DDP), covering the three main stages of the platform tectonic activation. Late Hercynian epoch was characterized by the formation of large linear anticlinal zones and salt-shafts against the background of the general syneclizal deflection of sedimentary basin, located within the paleorift. Cimmerian epoch of tectonic activity led to significant thrust deformations of the primary structural forms of the cover in the geodynamic setting of collision compression with intensification of the horizons of the sedimentary cover. The structural manifestation of strike-slip tectonics at Alpine epoch in sedimentary complexes are mainly horizontal displacements of geomases of blocks, lineaments, local tectonic elements and structures along dynamically interconnected coulisse of strike-slip domains. Methods. Structural kinematic analysis of transformations of the fracture systems of the Upper-Visean sedimentary complex under the influence of natural mechanism of reid tectonic flow of rocks. Results. The secondary structures of strike-slip deformation, structural kinematic parageneses, dislocations zones and subregional structural waves were identified in the structure of the platform cover, which are natural geological objects formed at the inversion stages of geological development of DDP. Scientific novelty and practical significance. The result of structural manifestation of volume tectonic flow in the platform complex was horizontal displacements of the original tectonic elements, blocks, segments, structures along dynamically-linked strike-slip domains. This is caused by the formation of secondary deformation structures of various scales, morphology and genesis, which comprise longitudinal structural waves of strips of post-rift deformations in the structure of the sedimentary cover of DDP.

The valuation of the residual and secondary deformation of the medium face zone in patients with unilateral cleft lip

Background. The treatment of patients with cleft lip and palate is a complicated medical-social problem. The residual and secondary deformations of the nose, upper lip, and dentoalveolar require surgical correction in these patients after undergoing complete reconstruction as a child. Aim. To systematize the degree of severity of the residual secondary deformation of the medium face zone in adult patients after previous surgery. Materials and methods. This scientific work was based on the results of 42 adult patients with unilateral cleft lip after undergoing complete reconstructive surgery as a child. The valuation of residual and secondary deformations of the nose, upper lip, and vestibule was performed in adults aged 25–40 years. The typical residual deformation at these locations was determined and separated into three groups and given a value. Results. We observed that 91% of the patients with unilateral cleft lip had a deformation in the medium face; of these patients, 15% had severe deformation with an absolute indication for surgery. Conclusion. The residual and secondary deformations of the medium face zone were diagnosed in 91% (80.6%–96.7%) of the patients operated using the Miro-Limberg-Obuyhovoi method in the remote period. Moreover, 15% of these deformations had an absolute indication for surgery. The three numbers used in the valuation system of the residual and secondary deformations of the medium face zone in patients with a unilateral cleft lip enable impartial and quick determination of the intensity of one or more deformations of the nose, lip, or vestibule of the mouth.

The technical aspects of using timber in the construction of forest roads

This study is on the ecological aspects and interest of the State Forest National Forests Holding (SF) units in reinforcing the ground subgrade by using timber raft construction and brushwood mattresses in forest road construction. The aim of the study was to analyse the technical parameters of forest roads made on a ground subgrade reinforced with timber raft construction and brushwood mattresses. As part of the research, the scope of SF units’ application of technological solutions and the parameters of existing forest district roads made on a timber substructure were determined. A road with reference sections using different variants of subgrade reinforced with timbers logs (oak, pine) and brushwood mattresses were studied. The technical parameters of features ensuring usability, such as, among others, the bearing capacity of the pavement, were selected for the analysis. The ability of the tested pavements to support vehicle axle loads was determined based on the deflection of the surface as well as the primary (MEI) and secondary (MEII) deformation modulus with a calculated deformation indicator (I0). The deformation modulus ME of the pavement and road subgrade were determined using a VSS plate with a diameter of 300 mm. It indicated a large range of results of secondary deformation of surfaces using timber raft construction (107-204 MN·m-2) and brushwood mattresses (26-58 MN·m-2), which are dependent mainly on the diameter of the logs used, their arrangement and the road fill used.

Some Studies on the Bulging Characteristics of Cold-Upset Steel Preforms

Present investigation pertains to establish the bulging characteristics of sintered steel preforms under cold upsetting. Cylindrical preforms of Fe-0.8%C and with 1%Mo and 2%Mo of 86% initial theoretical density and 0.4 initial aspect ratio have been produced through conventional powder metallurgy techniques. These preforms were further subjected to secondary deformation, that is, cold upsetting under nil and zinc stearate lubricant conditions. The results obtained from this experiment were used to study the bulging characteristics with densification and hoop stress. An empirical equation is determined between these parameters and is found to follow a power law relationship.