No 2 (2018)

Modern methods of laser processing of the materials are actively introduced into production. However, their wide application in engineering is hampered by the high energy intensity of the processes and the unexplored complex high-speed processes of such processing technologies. This paper covers the hybrid laser technologies for processing materials, in particular, laser-field hardening of metals. The theoretical study of laser interaction with metal is carried out; it is shown that the laser radiation reflection index and the depth of its penetration depend on the electrical conductivity of a skin layer. The study determined the main interrelations between the quality parameters of a treated layer and the parameters of the laser-field technological complex. The paper gives the results of the study on hybrid laser-field hardening of steels widely used in engineering (Steel 10, Steel 45, and Steel 65G) in the electrostatic field. It is shown, that the electrostatic field superposition on a treatment zone leads to the increase in the depth and hardness of a hardened layer through the directed motion of electrons deep into metals. The authors offer a mathematical model for the temperature field distribution in metal under the influence of laser radiation that considers the electrostatic field superposition and allows investigating the dynamics of the hybrid laser hardening. The limitation of the increase in the rate of material cooling by the electrons directional motion in the electrostatic field is mathematically substantiated. The specific values of the electrostatic field influence coefficient are calculated. It is shown, that when superposing the external field, the threshold, critical value of the density of the laser radiation power causing the melting of the treated surface increases. The authors offer the specific mathematical models to be used when preparing a production for determining the required laser radiation power and the strength of the electrostatic field. Based on the results of the study, the principal process scheme is offered, and the laser-field technological complex facility is designed and manufactured.

The paper considers such important phenomenon in radio components as the cleavage in multicomponent materials. Composite materials are the important class of radio materials, thus the improvement of complex of their properties has the important fundamental and applied significance and is the up-to-date sector of the material science. The improvement of composite materials contributes to their wider application and production of new radio components. Alongside with the composite materials properties’ improvement, the compounds where other elements, for example, rare-earth (alloys with praseodymium or samarium) are applied are of considerable interest. The paper studies the influence of thermoelastic stresses on the performance capacity of radio components containing composite materials, identifies physical factors influencing most greatly the operational suitability of the products with the composite materials. The author had an objective to study the mechanisms of initiation and behavior of a thermoelastic breakdown in a composite material containing the inclusions, in particular, air inclusions. For example, metal-based composite material contains dozens of inclusions of various compositions. As a rule, composite materials contain air inclusions the influence of which should be taken into account as well. The electrical strength and the service life of the details produced from the non-homogeneous composite materials within the strong electric fields depend on the content of air inclusions and their shape. The paper presents the calculation of the electric field strength in the inclusions and near them. The author considered the process taking place in an ellipsoidal inclusion under the influence of strong electric field and analyzed the relative influence of large inclusions’ shape on the hardening mechanism. The processes for small and large inclusions in a composite material and their influence on the destruction of the details caused by the discharges in the inclusions are considered separately. The influence of complex external action (different temperatures, etc.) is studied. It is identified that the heat generation caused in the strong high-frequency fields by the ionization in air inclusions in composite materials can be significant and, under the strong external actions, the destructive stresses can occur. The uneven heating of a composite material leads to the appearance of destructive thermoelastic stresses and to the cleavage of radio components caused by the heat generation in large inclusions.

While repairing the metallic structures of tanks, main and process pipelines of oil and oil products transportation system, high porosity of welds can be observed. As a reason of high porosity, the change of chemical composition and metal structure resulting from the environmental effect including the contact with oil and oil products can be considered. The dominant factors affecting the high pore-formation while repairing the elements of pipeline transportation system which were described earlier in the research literature with respect to the special characteristics of continuous wire welding in the carbon dioxide environment are the high hydrogen and carbon content in the molten weld pool, high cooling rate of metal, strain aging of the ferritic-pearlitic steels, and the hydrogen embrittlement. The conclusion about the reasons for high porosity is made. The authors carried out some studies which verified the increased hydrogen and carbon content in the metal under the influence of operational factors and what is more, in metal at the side of contact with oil products, the hydrogen content by weight on the inside of sample is twice as big as the hydrogen content by weight on the outside of it. The carbon content on the side of contact with oil is 20 % more than that on the inside. Based on the research, the authors offered a number of techniques for decreasing the weld metal porosity under factory conditions of PAO “Transneft”: the increase of heat input rate of welding within the established range of welding modes; the preliminary thermal treatment of used steel with the following slow cooling for the decrease of free carbon.

One of the effective means of improving the efficiency of the operations of work materials mechanical processing is the rational use of the ultrasonic vibrations energy (UVE). To develop the recommendations on the selection of the UVE direction and amplitude, within the grinding process, the study of the kinematics of interaction of a grinding wheel and a workpiece is carried out. The authors suggested the analytic dependences to calculate the velocity of displacement of an abrasive grain against a workpiece, the number of abrasive grains contacting with the workpiece, and the Ra parameter of surface roughness when grinding with the UVE. Using these dependencies, the numerical simulation for various conditions and grinding mode is carried out. It is determined that when applying vibrations to the workpiece in the direction coinciding with the vector of the operating velocity of a grinding wheel, to decrease the frictional force within the contact zone of a wheel with a workpiece, the vibrations with the frequency going beyond the frequency range of the industrial ultrasonic devices are required. The applying of vibrations in the direction perpendicular to the processed surface causes the significant increase in the altitude parameters of the roughness of this surface. When applying vibrations in the direction coinciding with the wheel axis, minimal altitude roughness parameters are achieved, and due to the intermittent contact of grains with the workpiece it is possible to decrease the friction ratio, consequently, it is reasonable to apply UVE in the same direction. To apply vibrations to a workpiece, the authors used the device where the workpiece is being fixed between the vibration sender and the bearer and is considered to be one of the parts of the vibrating system. The experimental study carried out when flat grinding of blank parts made of 3H3M3F and 12H18H10T steels allowed determining that the applying of vibrations with the amplitude of 2A_z=6…9 µm in the direction coinciding with the wheel axis ensures the decrease in the grinding force by 10…15 %, wheel wear by 25…40 %, Ra roughness parameter by 12…15 %.