Applied Mechanics and Materials Vol. 756

Abstract: Several ways of technical diagnostics have been researched. General aspects have been considered of the mechanism diagnostics by vibroacoustic signals. The assessment of the vibroacoustic engine diagnostics method is provided. On the basis of a laptop computer, a portable diagnostic complex has been elaborated for the pre-assessment of combustion engine mechanisms' condition using parameters of a vibroacoustic signal. For technical assessment of combustion engines a diagnostic scheme has been proposed for mechanical components by vibration parameters.

Abstract: The effect of hydrogen embrittlement on the plastic flow of aluminum alloy D1 was investigated. The studies were performed for the test samples of aluminum alloy subjected to electrolytic hydrogenation in a three electrode electrochemical cell at a controlled constant cathode potential. It is found that the mechanical properties and plastic flow curves of aluminum alloy are affected adversely by hydrogen embrittlement. The hydrogenated counterpart of alloy has a lower degree of ductility relative to the original alloy. The deformation diagrams were examined for the deformed samples of aluminum alloy. These are found to show all the plastic flow stages: the linear, parabolic and pre-failure stages would occur for the respective values of the exponent n from the Ludwik-Holomon equation. Microhardness tests were performed for as-treated aluminum alloy D1. Using scanning electron microscopy method, the changes in the fracture surface were investigated.

Abstract: New static-pulse treatment method was offered to increase contact pitting resistance of machinery parts. This method forms cold-worked layer with high hardness located deep in the part. The static-pulse treatment method is characterized by important feature that helps to form various levels of hardening uniformity of the surface layer. For the first time undertaken studies provided recommendations relating to uniformity of surface layer mechanical hardening, which increases contact pitting resistance of machinery parts made of 45, 40H, 35HGSA steel.

Abstract: The article provides a tribological basis of a new deformation-thermal method to make the surfaces friction materials for plain bearings the improved anti-friction properties (high score resistance, running-in and others) by creating a modified surface layer. The method is based on the use of surface plastic exposure with the subsequent realization of the effect of thermal return of a thin surface layer. A number of most important descriptors of friction ensuring a durability of tribosystems in extreme conditions was considered. Basing of the laws of solid mechanics, principles of material science and regularities of friction and wear, the possibilities of transformation of these values in a favorable direction by using the new method were estimated. The experimental conditions for samples of bearings alloys used in modern reciprocator are given. The results of experimental study of tribodeformational effects for these alloys for a baseline option and with a preliminary modified surface layer are presented. A possibility in principle for the substantial increase of service properties of study group of materials basing on use of the presented method of modification is indicated.

Abstract: The technique was developed with the purpose of definition of parameters for surface layer uniformity after mechanical hardening. It was found that one of the most effective methods of surface plastic deformation that provide precise adjustment of uniformity level of surface layer hardening is presented by static-pulse treatment technique. This method helps to develop hardened surface layer 8 mm deep with virtually uniform or heterogeneous structure.

Abstract: This paper describes the regularities of structuring of surface roughness at surface plastic deformation in order to revise calculation of operating modes at the design stage of the technological process. The formula of roughness profile that allows calculating its general parameters has been obtained.

Abstract: The possibilities of application of various designs of shock mechanisms for hardening by surface plastic deformation were considered. The measuring methods of their energy characteristics were shown.

Abstract: The influence of the welding current and method of gas shielding in MAG welding on the content of silicon and manganese is considered. Results of study of the welded specimens of steels 45 and 30HGSA when applying welding wire of different formulas and different types of gas shielding (traditional shielding and two-jet shielding) are given. It is established that in MAG welding the value of the welding current and the speed of the gas flow from the welding nozzle have a considerable impact on the chemical composition of the weld metal. The consumable electrode welding under double-jet gas shielding provides the directed gas-dynamics in the welding area and enables controlling the electrode metal transfer and the chemical composition of a weld.

Abstract: The paper provides the results of experimental study of how the technological characteristics (amount of spatter, stability of the welding process) of manual metal arc welding (MMA) depend upon power supplies providing various kinds of energetic impact upon the electrode metal (inverter power supply, diode rectifier). It was established that inverter power supplies (as they reduce peak loading) provide better quality of welds (more stable process, lower amount of spatter) and this reduces the fabrication cost due to the reduction of deseaming operations, lower welding material consumption as well as improving the service reliability of the welding constructions.

Abstract: In the paper the authors provide the method for calculating the heat content of the molten electrode metal droplets according to the energy parameters of the power supplies for manual metal arc welding. It was established that the type of the welding power supply has a significant impact upon the temperature, mass and active surface area of the electrode droplets.