There are developed over 100 projects, themes and tasks in the field of welding. They are:
- International projects – 5
- Projects ordered from abroad – 10
- Tasks from co-ordination programs – 3
- Projects, themes and tasks ordered by state bodies – 15
- Projects of NF “Researches” – 5
- Projects, themes and tasks from the plans of IMS-BAS – 70
On this basis more than 40 unique technologies were developed.
- IWSD – Implementation of International Guidelines for Welded Structural Designer Training
- “Improvement of the safety of large welded constructions by local explosive treatment” – project under NATO program “Science for Peace” – NATO SFP 973409
- “Modeling and numerical determination of nitrogen redistribution as result of the thermal diffusion during welding of nitrogen alloyed austenitic stainless steels” – joint project of the Institute of Metal Science and Technical University in Braunschweig, Germany. The project is funded by Foundation “Volkswagen”.
- “Calculation of hydrogen redistribution during welding” – joint project of the Institute of Metal Science and Technical University in Braunschweig, Germany. The project is funded by the German Research Society.
- “Investigation and development of welding technological processes for metals and construction components and treatment of the metal constructions welded joints by explosion” – Co-ordination Center of the countries-members of COMECON for the issues of “Welding”, Subject 37.
- “Investigation of the mechanism of cold crack formation in the zone adjacent to the weld” and Subject 188.8.131.52
- “Comparative investigation between TU-2 (test with sets and samples of different toughness) and ТЕККЕН”, task 19.2 of COMECON
“New concept for formation and development of natural welding stresses”
According to it the reason for the formation of welding stresses is the interaction between the local insusceptibility of the welded joint and the natural welding deformations (thermal and structural), provoked by the source of energy. In the frames of this concept the following are developed:
- Phenomenological models for the formation and development of the natural welding deformations and stresses in case of internal and external hampering of the joints which take into account the insusceptibility effect, structure transformations and deformation strengthening.
- Theoretical model for the kinetics of the transverse deformations and shifts, characteristic stages in their progress and size being defined in dependence of the type of the welded joint insusceptibility. The model is experimentally proved.
- Criteria are defined for the welded joints insusceptibility – local degree of insusceptibility, intensity (basic and relative) of the local degree of insusceptibility and generalized characteristics are introduced (seam eccentricity and linear energy of welding), taking into account the effects of the welded construction and welding technology, respectively.
Qualitatively new approach is developed for quantitative assessment of the welded joint resistance against formation of cold welding cracks, including:
- Original method for test and quantitative assessment of the welded joints stability and the resource of technological strength in the process of austenite disintegration and transformation during welding and subsequent cooling based on the delayed loading of the welded joint by the natural welding stresses.
- Technological set of module samples allowing test and assessment of the resistance of various types of welded joints (butt, corner, Т- shaped) against cold crack formation. By variation of the intensity of the local degree of insusceptibility, a critical value is achieved when cold crack occurs.
Theory of residual welding stresses relaxation and increase of the safety of the welded joints and constructions by local explosion effect covering:
- A new hypothesis and theoretical model describing the process of residual welding stresses reduction by local explosion treatment checked and verified by a series of experiments and practical applications. In the dilution zone behind the shock wave front, there is adding up of the temporary tensile stresses provoked by the dynamic impulse with the tensile residual welding stresses which results in plastic elongation of the metal. The relatively long duration time of tensile loading behind the shock wave front provides the possibility for translation of the dynamic yield strength in direction of the static one. In addition, the occurrence of vibrations in the welded joint also contributes for reduction of the dynamic yield strength. All these processes lead to transformation of the deformation elastic component into plastic with retention of the total deformation. As a result, the residual welding stresses decrease and redistribute.
- New criteria, that permits quantitative assessment of the local explosion treatment effectiveness.
- Increase of the safety of the welded constructions by residual welding stresses relaxation through local explosion treatment and improvement of the welded joints characteristics. It is found out that the improvement of the mechanical characteristics is due to the changes both in the microstructure and in the dislocations field and density in the welded joint metal.
Development of the theory of high alloyed austenitic stainless steels weldability, in particular:
- A method is developed for examination of the diffusion processes in high alloyed Cr- Ni and Cr – Mh steels in non-isothermal conditions and there are found out the coefficients of nitrogen diffusion in the temperature range 800 – 1450 degrees for Cr- Ni and Cr -Mh steels.
- A new equation is defined for the nickel equivalent valid for nitrogen concentration from 0,4 to 0,8 %. It is found out that with increase of nitrogen concentration in the welding seam, the content of delta ferrite in it decreases and at certain conditions, a pure austenitic structure could be obtained.
Modeling and simulation of welding processes.
- Original computer models are made describing the welding heat source and the temperature field in the welded joint, the fields of the temporary and residual welding deformations and stresses, the microstructure and hardness in the heat affected zone.
Development and supplementing of the theory of diffusion weld in vacuum, in particular:
- Suggested theoretical model of the process of physical contact realization during diffusion welding in vacuum of steel-alumina ceramics joints.
- Suggested theoretical model for assessment of the isothermal holding time during diffusion welding in vacuum of metal and ceramics required for realization of physical contact over the whole bonding area based on the kinetic theory of dislocations.