Bulletin PNRPU. Mechanical engineering, materials science

The results of research and development of technology of plasma arc welding penetration with simultaneous wire feeding non-ferrous metals and complex alloys. The optimal conditions for the formation of the weld combined process. Mathematical relationship set wire feed speed from the geometrical characteristics of the junction and the wire diameter. The obtained results allow us to pick up the necessary arc welding is penetrating the formation of high-quality and defect-free connection. Described the possibility of the wire, which is implemented in a way that maintains the balance of power factors on the front wall of the liquid bath. The evaluation of different ways of presenting the filler wire to the tail section and the front edge of the weld pool. Experiments were conducted with various embodiments of the filler wire feed on the leading edge of the crater cavity. In the first embodiment, the filler wire fed from the touch surface and the second embodiment applied to a wire weight. Given macro shots penetrating arc plasma welding of aluminum, titanium and complex alloys with the most favorable one for the formation of the joint. The principal possibility of obtaining defect-free welds at the lowest cost and high performance.

In this article the influence electro-spark under nitrogen environment technological aluminium deposit, on microstructure, hardness and impact toughness (KCU) on temperature minus 40 °С executed by manual arc welding and welding under gumboil without and after tempering at temperatures 200-500 °C, was considered. Welding procedure was carried on conventional parameters for low carbon base metal 12 mm thickness. Technological deposit changes pearlite dispersibility and retained austenite morphology in all considered welds. Hardness of the built-up metal after manual arc welding and holiday sharply decreases, and when welding under gumboil practically doesn't change, irrespective of application of a technological underlayer. Positive influence of a technological underlayer on impact strength at manual arc welding is revealed. The tempering influence was negatively for all welds.

Work is devoted to modelling of process of formation of structure elements during the high-energy influence on a surface of a metal alloy by means of pulsed laser. At high speeds of cooling of a metal melt after action of a laser impulse in a surface layer is formed a metastructural condition of the alloy. The sizes of proeutectoid constituents in such structure are 0,1-0,4 mcm. The mathematical model of proeutectoid constituents formation is developed for the description of conditions of structure formation at pulse laser action. At the heart of this model are put thermodynamic conditions of formation of proeutectoid phases. Distribution of energy of formation of a nucleation center of a proeutectoid phase to interatomic bond in its crystal lattice is used as the basic approximation of model. In this model superficial energy of a nucleation center is considered as total energy of not compensated superficial bonds. It allows to present expression for energy of a nucleation center in the form of function of its linear size. Features of a crystal structure of a proeutectoid phase in terms of atom coordination environment is considered by this function. With use of offered model have been carried out calculations of the critical sizes of nucleation centres of carbides and borides which are formed during modifying of a surface of steels by means of pulsed laser with use of the alloying composition. Results of calculations by offered model have shown the good coordination with experimentally observed allocating of sizes of proeutectoid phases. Besides, the analysis of competitive conditions of formation of proeutectoid phases of different stoichiometric composition has allowed to explain features of structural content of layers on a surface of steels during modifying by means of pulsed laser.

The article describes an overview of the practical principles in assessing the ballistic characteristics of non-metallic materials in terms of mechanical and physical properties are presented and principles of assessment of ballistic properties of the articles made of nonmetallic materials. Presents the methodology for assessing the ballistic properties of the density and compaction, as well as Young's modulus, shear modulus and compression modulus. Techniques based on the determination of the Hugoniot elastic limit, a semi-infinite penetration test, the test of the depth of penetration test, the firing pin stop, combined test penetration and stopping, the method of fixing the target geometry, the tandem method principles and definitions of the ballistic limit. The presented techniques are varied, unlike the methods for determining the class of bullet resistance, however, among them there is no dedicated as standard, making it difficult to assess the materials with similar properties. The authors also represent a rare kind of test for the comparative evaluation of ballistic properties by analyzing the target fragmentation after its defeat drummer. The data of fragmentation analyzes conducted for samples of synthetic mineral alloys destroyed high-velocity impact produced by a railgun.

The article discusses the structure formation of mineral phases melt synthetic mineral alloy with the phenomena liquation differentiation. The process of structure formation can be divided into four stages: Stage 1 - The thermodynamic changes homogeneous melt; Stage 2 - bundle or Binodal alloy decay into two immiscible liquids and loss of crystalline phases in the “precipitate”; Stage 3 - monotectic reaction in the liquid phase; Stage 4 - crystallization homogeneous acidic liquid. Influence binodal decay is expressed in selectivity capturing one of the liquids in the form of inclusions occur spotty distribution of components in a variable composition and appearance of individuals of irregular shape that follows the shape of one of the liquid phases of two-phase melt. In the context of immiscibility occurs common mineral association, each member of which grew out of the two liquids. Identification of patterns of manifestation of low-temperature stable immiscibility in melts siminalah allows us to conclude that the role of segregation in the structure formation is reduced not only to the formation of various mineral phases as to the direct effect of segregation on the overall process of structure, composition and structure of crystallizing phases of mineral aggregates.