Viktor Kvasnytskyi

The regularities governing the formation of temperature fields and the geometric parameters of penetration during laser welding of thin-walled cylindrical shell–end element structures made of aluminum alloys were investigated. Three welding schemes were considered: welding of 7075 alloy in an argon atmosphere at a reduced pressure of 170–190 Pa and at atmospheric pressure (105 kPa), as well as welding of a dissimilar 5083–7075 joint in an argon atmosphere at reduced pressure. Laser welding was performed at a power of 400 W and a welding speed of 66.7 mm/s. The experimental investigations were combined with finite-element modeling of thermal processes using a calibrated volumetric conical heat-source model. It was determined that, for alloy 7075, the penetration depth increases to 1.0 mm while the weld width simultaneously decreases to 0.38–0.40 mm, whereas at atmospheric pressure these values are 0.47 and 0.60–0.67 mm, respectively. Experiments showed that, during welding at reduced pressure, the structure is heated to 38–40 °C at a distance of 2–3 mm from the fusion line. The results obtained show that reduced pressure can be an effective process parameter for localizing welding heating.

Purpose. To systematize modern machine learning (ML) methods for the intelligent control of wire arc additive manufacturing (WAAM) and to identify priority directions for further research. Research methods. Critical analysis and synthesis of information from contemporary scientific publications; systematization of machine learning methods according to WAAM tasks – regression models (Random Forest, LightGBM, artificial neural networks), computer vision architectures (CNN, U-Net, YOLO), recurrent networks (LSTM), reinforcement learning methods, and physics-informed neural networks (PINN). Results. Modern ML methods for the intelligent control of WAAM have been systematized according to key technological tasks: predicting the geometric shape and dimensions of deposited beads, analysing the geometric dimensions of the weld pool using computer vision, and adaptive process control. The authors describe the web-based software (CAM system) they developed, which incorporates artificial intelligence, implements the full cycle from a 3D model to control code (G-code), and provides recommendations on deposition modes. Scientific novelty. A holistic systematization of machine learning methods for WAAM intelligent control is proposed, linking ML model types to specific technological tasks and outlining under-researched directions, in particular the application of physics-informed neural networks and digital twins for adaptive process control. Practical value. The developed software enables automation of WAAM process preparation – from 3D-model processing to G-code generation and deposition mode selection – improving the accuracy, reproducibility, and efficiency of additive manufacturing.

The object of the study is the welded joint of thin wires made of nitinol alloy. The problem of ensuring the formation of a joint of wires with a diameter of 0.8 mm made of nitinol alloy was solved based on determining the influence of laser welding modes on structural changes in the material of the weld. Based on the use of scanning electron microscopy, micro-X-ray spectral (EDS) analysis, a study of the properties of the material of the welded joint of the nitinol wires was performed. The joint was obtained by welding with an ytterbium fiber laser. It was confirmed that laser welding in an argon atmosphere is able to ensure the high-quality formation of a welded joint without macrodefects while maintaining the superelasticity of the joint material (within the shape memory effect). Two laser welding modes were used with a constant applied laser radiation energy. The duration of the laser radiation action and the multiplicity of such action were varied. At the same time, structural changes in the weld material, which are caused by the multiplicity of laser heating, involve the formation of enlarged zones of the eutectic TiNi + TiNi3 from metastable nanophases of titanium nickelides. The number of such grains decreases with the depth of the weld. Detection of structural changes and establishment of a decrease in the number of point phase inclusions with an increased nickel content in the weld can be a regulating factor for optimizing the structure of the welded joint material. In the welded joints made, when it is bent at an angle of 30°, the residual deformation does not exceed 10%. The results of the study of the structure of the welded joint of nitinol wires made by laser welding are promising and can be used in the conditions of manufacturing nitinol wire connections by welding medical products

The object of the study is a permanent joint of thin wires made of nitinol alloy. The problem of ensuring the formation of a joint of wires made of nitinol alloy was solved based on minimising changes in the structure of the welded joint material relative to the materials being joined. The properties of the welded joint material of the nitinol were studied using scanning electron microscopy and micro-X-ray spectral analysis. The studied permanent joint was obtained by TIG, microplasma (PAW) and capacitor discharge (CDW) welding. It was found that TIG welding can ensure the proximity of the microstructures of the wire and welded joint materials under conditions of sufficient protection in an argon atmosphere. Such TiNi welded joints have a welded joint material that retains its superelastic properties (within the limits of the shape memory effect). Capacitor discharge welding allows the joint to be brought closer to the required level of microstructure of the weld material. The results of mechanical tests demonstrated the limited capabilities of joints made of thin nitinol wires. At the same time, the appearance of only newly formed TiNi + TiNi₃ eutectics in the weld material and a sufficient level of restoration of the welded joint shape give reason to consider capacitor discharge welding promising for joining thin nitinol wires. PAW leads to the formation of a significant amount of oxides in the weld and an increase in the number of Ti₂Ni inclusions, which leads to brittle fracture of the welded joint even at low degrees of deformation. The results of the study can be used, in particular, for the manufacture of nitinol wire joints in medical devices.

Assessment of the residual stress-strain state (SSS) at MIG welding of aluminium alloys structures is relevant, because of the need to predict formation of residual stresses and strains, which may lead to lowering of fatigue strength of such a structure. Therefore, the research is devoted to...

The objective of this study is to investigate the formation of the structure and stress–strain state in the joints of AISI 304 stainless steel with a thickness of 2 mm and produced by welding with laser and plasma energy sources. It is established that the microhardness and parameters of the grain and subgrain structures of the welded joint material differ with respect to the dimensions of crystallites, grains, and subgrains according to the welding process. It is shown that, in terms of structure formation, including substructural features, the most favorable structures of 2 mm AISI 304 welded joints are formed by laser–plasma welding. It is predicted that the residual stressed state is less localized with the application of laser–plasma welding than laser welding, and it is characterized by a lower level of residual stresses compared to plasma welding. In all the cases, the maximal stress values are concentrated in the HAZ, and the value obtained using laser–plasma welding is in an intermediate position (431.7 MPa) between those of the laser (443 MPa) and plasma (413.7 MPa) processes. With laser–plasma and laser welding, displacements (deformations) are minimal and close to 0.2 mm. The method of electron speckle interferometry was used, and the results reveal that the error between the calculated and experimental values of equivalent stresses is no more than 6%, which is acceptable. The results of mechanical testing show that, under uniaxial tension, the strength of the welded joints made of AISI 304 steel using laser–plasma and laser welding is the highest and equal to 97% of that of the base metal.

The objective of this study was the additive microplasma powder deposition of 3D metal products. The regularities of the influence of technological parameters of additive microplasma deposition of spatial objects using the powder filler material of a Fe–Cr–Ni–B–Si system on the formation of the microstructure and stress–strain state of 3D product material were studied in this work. Product walls with a layered metal structure with a deposited layer height of about 650 µm and 3.0–3.5 mm thickness were formed as a result of additive microplasma deposition of the HYF–103 powder of a Fe–Cr–Ni–B–Si system. The deposited metal ensured a high ultimate strength (above 600 MPa). The finite element method was used to derive the solution of the thermomechanical problem of additive deposition of 3D prototypes («cylinder», «triangular prism», «square prism», «reverse cone», «straight cone») with HYF–103 powder. The equivalent stresses of the highest magnitude (565 MPa) were predicted in the model sample of the “reverse cone” type, and the lowest stresses (552 MPa) were present in the sample of the “straight cone” type. For all the models, the maximal values of radial movements corresponded to the range of 0.22–0.28 mm. The respective technological mode of deposition was selected to minimize the stress–strain state of the produced 3D objects.

The Paton Welding Journal, 2023, №11. International Scientific-Technical and Production Journal «The Paton Welding Journal» «The Paton Welding Journal» has been published monthly since 2000 in English, ISSN 0957-798X. «The Paton Welding Journal» is a cover-to-cover English translation of the «Avtomaticheskaya Svarka» (Automatic Welding) journal. The «Avtomaticheskaya Svarka» journal has been published monthly since 1948 in Russian, ISSN 005-111X.

Automatic Welding, 2023, №11. Journal «AVTOMATICHESKAYA SVARKA» Monthly scientific-technical and production journal. ISSN: 0005-111X, Since 1948. Russian version of «The PATON Welding Journal» Text in Russian, contents and summaries in English. The Journal presents a wide range of scientific-technical and promotion information in the field of technologies, equipment and materials for welding, surfacing, brazing, and deposition of protective coatings.