Browsing by Author "Pleshakov, Eduard"
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Item Failure analysis of a motor vehicle suspension helical spring(Lviv Politechnic Publishing House, 2020) Bohun, Lidia; Pleshakov, Eduard; Shvachko , Sergiy; Lviv Polytechnic National UniversityThe purpose of this work is to reveal the cause of the failure of the motor vehicle rear suspension barrel-shaped spring with the progressive elasticity characteristic and predict measures to increase the lifetime of springs of this type. The fracture of the spring occurred on the middle coil, which operates under conditions of more severe stress in comparison with other coils. The chemical composition of the spring material, determined by X-ray fluorescence spectral and microstructural analyzes, corresponded to chromium-silicon steel 54SiCr6. In terms of structure and mechanical properties, the spring material met the standards. No traces of decarburization were detected, and no crack initiation, caused by non-metallic inclusions, was found in the material of the fractured spring. Macroscopic examination of the spring surface did not reveal any cracks, scratches, dents, traces of blows with stones and marks of spring coiling tool. Instead, extensive areas of exfoliation of the protective coating were found. The metallographic analysis revealed selective corrosion in the form of pitting damage in places of exfoliation of the protective coating. The fatigue crack propagates from the certain deep pit with the reorientation of the crack plane along the spiral surface to the central axis of the coil wire. After depletion of the safety margin, the spring broke down quickly. The fast fracture zone contains steps of the river pattern formed due to the spiral reorientation of the fracture surface. The research can be used to understand the importance of adhesive strength and wear resistance of protective coatings on the spring surface. Their local exfoliation causes subsequent corrosion damage to the spring, which stimulates its fatigue fracture.Item Influence of heat treatment modes on the performance characteristics of resistive cermet coatings(Lviv Politechnic Publishing House, 2020) Kovbasiuk, Taras; Duriagina, Zoia; Kulyk, Volodymyr; Pleshakov, Eduard; Kushpir, Vasyl; Lviv Polytechnic National UniversityDielectric and resistive coatings based on glass ceramics with nickel boride additives have been synthesized. It was found that the microstructure of the resistive coating consists of a large number of phases. X-ray fluorescence analysis revealed the presence of Ni and Cr borides in the structure of the resistive layer. It was found that the change in the structure and specific surface resistance of resistive pastes practically does not affect the temperature coefficient of resistance of the synthesized resistive tracks.Item Innovation technologies in training specialists in engineering materials science(Publishing House of Lviv Polytechnic National University, 2015) Duriagina, Zoya; Bohun, Lidiya; Pleshakov, Eduard; Tepla, TetianaThe aim of educational program TEMPUS is the integration of Eastern countries in the Bologna process. Participating of Lviv Polytechnic National University in project “Modernization of two cycles (MA, BA) of competence-based curricula in Material Engineering according to the best experience of Bologna Process – 543994-TEMPUS-1-2013-1-BE-TEMPUS-JPCR” allows to improve the quality of training of specialists in the field of materials science. Directions of “MМATTENG” project realization by Applied Material Science and Materials Engineering chair, implementation of computer-integrated technologies within the project, formation of modernized educational programs, trainings and retrainings of lecturers, seminars on the base of EU Universities, enterprises and companies-developers of software products and formation of the common research centers of materials science with participation of leading foreign and home companies are described in this article.Item Methods of rolled copper wire properties improvement(Lviv Polytechnic Publishing House, 2015) Duriagina, Zoya; Dvorianyn, Khristyna; Shvachko, Sergiy; Pleshakov, Eduard; Tepla, Tetiana; Lviv Polytechnic National UniversityHot cracks of rolled copper are the most wide spread type of discards under continuous casting which are eliminated with difficulty. In industrial production of rolled copper wire at the plants of Ukraine the amount of oxygen in the obtained rods does not exceed the standard values. In this paper it is proposed to subject the melt to ultrasonic treatment to degassing process and the formation of homogeneous, dispersive sub dendrite structure of the rolled copper.