Reference on the research, scientific and organisational activities of Prof. SYDORETS Volodymyr M.

Sydorets was born in 1956 in Kyiv, Ukraine. He graduated from the Taras Shevchenko National University of Kyiv, Faculty of Physics. Physicist (M.D.) in “General Physics, Theoretical Physics” (1978). Candidate of Sciences (Eng.), (Ph.D.) in “Theoretical Electrical Engineering” (1992). Doctor of Engineering (Dr. Sci.) in “Theoretical Electrical Engineering” (2009). Staff member of the E.O. Paton Electric Welding Institute of the National Academy of Sciences of Ukraine since 1973, Leading Researcher of the Department for Gas Discharge Physics and Plasma Devices since 2009, Professor in “Welding and Related Processes and Technologies” (2013).
     Sydorets is the well-known specialist in area of electrodynamics of welding arc, laser and laser-arc welding. The main directions of his work are related with investigation of welding arc, stability of “welding arc - power source” system, study of laser beam properties and its interaction with metals as well as peculiarities of laser-arc discharge.
     Sydorets has made significant contribution in development of theory and practice of welding arc. In particular, he provided physical grounds of model of dynamic welding arc, which was developed at the E.O. Paton Electric Welding Institute. This allowed considering nonlinear properties and arc thermal inertia as well as its generalizing for the case of gas blown arcs, that is important for description of plasma processes and arcs with variable length necessary for consumable welding definition. Area of application of the generalized arc model was expanded for description of dynamics of arc geometry size, i.e. length and radius of column, which allowed solving the problems of acoustic and dynamic force action of the arc.
     Welding arc simulator was developed by him based on arc model. It was used during resource saving testing of welding power sources without application of welding consumables, namely electrodes, wires, gases etc. The simulator allows rendering different modes of welding without operator-welder, in particular, different types of short-circuit metal transfer from fine droplet one to globular. Demonstration of the simulator in Technical University of Hanover was highly appraised.
     He was in charge of optimizing the modes of pulse stabilizing of process of alternating current welding of corrosion-resistant steels using the arc model. Mechanical properties of produced welded joints are as good as properties of similar joints produced using direct current. This allowed proposing this method for use in welding of critical structures, in particular, ammonia transporting pipelines, and to replace direct current power sources with improved welding transformers, characterized by simple design and safety at operation under field conditions.
     To the most extent the efforts of V. Sydorets helped to support the world priority of the E. O. Paton Electric Welding Institute in fundamental investigations of deterministic chaos in electric circuits with welding arc. He published a monograph based on the results of these investigations. It is revealed that infinite cascade of bifurcations for period duplication in RLC-circuit with arc results in appearance of a strange attractor, i.e. non-periodic self-oscillations which are called deterministic chaos. V. Sydorets provided for a classification of elementary patterns of bifurcation diagrams of RLC-circuit with arc. It is based on properties of similarity, self-similarity and scale-invariance of these patterns. Two physical properties, i.e. softness or rigidity of appearance and reversible or non-reversible process at inversion change of bifurcation parameter, allowed him outlining three typical elementary patterns of bifurcation diagrams. Isolated areas of the bifurcation diagrams were found using determined fold structure of periodic solutions for RLC-circuit with arc. He proved that dynamics of the nonlinear circuits with electric arc is described by one difference equation and this provides for apparent advantages in comparison with description by three differential equations.
     Sydorets receives fruitful results combining his theoretical investigations with practical developments. He developed a stabilized drive system for rotation of circular saw blades in laser welding-up of cutting edge which is implemented in Poltava town as well as developed, produced and implemented a pipe heating system for deposition of corrosion-resistant coatings at “Chernigivnaftogaz” enterprise (Priluki town). Effect of welding power sources on power mains and other welding sources due to generation of current upper harmonics was investigated. Developed are the filters of upper harmonics being recommended for application in welding production in order to improve electromagnetic compatibility of welding power sources.
     Sydorets actively participates in laser researches. He developed a procedure for calculation of perspective models of laser with axial pumping as well as for calculation of slab laser. Software for n-axis manipulator of laser complex was developed. Perspective results were received in modelling of mode of deep penetration laser welding.
     In recent years he has been intensively investigating a laser-arc discharge which is used in development of new perspective technologies of laser-arc and laser-plasma welding. He studied quasi-static volt-ampere characteristics of combined laser-arc discharge, peculiarities of functioning of feedbacks in power sources of laser-arc discharge, amplitude-frequency characteristics of self-oscillations in a circuit with laser-arc discharge and technological characteristics of laser-arc discharge oscillations. The results of these investigations formed a basis for technology of high-speed welding of sheet metals. Application of this technology to welding of stainless steel and aluminum alloys demonstrated its perspectives.
     Sydorets researches the peculiarities of formation of weld spots in resistance micro-welding of precision elinvar alloys being used in instrument-making and echo ranging equipment. Based in the results of these researches new power sources were developed under the leadership of V. Sydorets. These sources are able to reproduce set current waveform that provides for not only high quality of the joint (absence of spatter and burn through), but preserve elinvar properties in weld spot and heat effected zone.
     He is an active member of scientific society. In particular, he regularly makes reports at the international scientific conferences. V. Sydorets is a member of Organizing Committee and a chairman of plenary sessions at the International Scientific Conferences on “Laser technologies in welding and materials processing” and “Mathematical modelling and information technologies in welding and related processes”, hold by the E. O. Paton Electric Welding Institute.
     Large attention is given to international cooperation. In the resent year V. Sydorets acted as an executive in charge for successfully fulfilled joint Ukrainian-Russian projects DFFD-RFFD “Modeling of processes of heat- and mass transfer in molten pool, keyhole and plasma plume at deep penetration laser welding of metals”  and “Investigation of interaction processes of plasma combined laser-arc discharge with dispersed metallic materials during laser-microplasma cladding”.

Main publications:

1. N. Sydorets, I.V. Pentegov (2013) Deterministic Chaos in Nonlinear Circuits with Electric Arc. Kyiv: International Association "Welding" (in Russian)
2. I.V. Pentegov, V.N. Sidorets (1990) Energy Parameters in a Mathematical Model of a Dynamic Welding Arc. Welding International, 4 (4), 272-275