In this study, hardfacing and a flux-cored/self-shielded powder wire of the FCAW-S-90G13N4 type was employed to produce and investigate the deposits of high-manganese steel. The effects of high-frequency mechanical impact (HFMI) treatment on the microstructure, hardening, and scratch resistance of the deposits were studied to evaluate and predict the impact wear resistance of the hardfacing deposits under controlled impact load conditions. As observed by XRD, SEM, and nanoindentation, the microstructure of deposited metal comprised a soft austenite matrix, dispersed hard carbides, and an epsilon phase (similar to 26 vol.%). The wear resistance is thus not controlled by carbides alone but arises from the synergistic action of a hard carbide network within a ductile matrix. HFMI resulted in twinning, an increase in dislocation density, a grown volume fraction of epsilon (>60%) and alpha '-martensite. The interaction between twins, martensites, and dislocations provides a double/triple increase in microhardness (from HV0.2 = 2.78 GPa to HV0.2 = 6-7.69 GPa). After HFMI, scratch tests showed lower restored depths of scratch tracks and a 36-68% deceleration in the wear rate regarding those of the initial deposit. The underlying wear mechanisms were assessed accounting for the SEM observations of the scratch track morphologies and a 'counterbody penetration vs. shear stresses ratio' map. The initial plastic deformation-related mechanism (wedge/pile-up formation) changed by HFMI to ploughing. The obtained results allow one to evaluate and predict the impact wear resistance of the hardfacing deposits under controlled impact load conditions.
The objective of this article is to optimise the deposition modes and the content of exothermic additions (EAs) in the core filler in Fe-C-Cr-Ti with Cu additions hardfacing. To achieve this, JMatPro Release 7.0, Sente Software Ltd., 2016 material characterisation software was used to simulate and calculate the equilibrium phase structure and composition of the Fe-C-Cr-Ti-Cu alloy during the welding thermal cycle. A synergistic approach combining the Taguchi-Analysis of Variance (ANOVA)-Factorial design (FD) method with the standard hybrid Taguchi-ANOVA-Principal Component Analysis (PCA)-Grey Relational Analysis (GRA) is used and justified to optimise factors and develop mathematical models for parameters in the L9 orthogonal experimental design. The study examines how the transfers of deoxidisers depend on the content of exothermic additions in the cored wire filler (EA) and the contact tip-to-work distance (CTWD), while the behaviour of carbide formers is influenced by wire feed speed (WFS) and present arc voltage at the power source (Uset). The research specifically investigates the Fe-C-Cr-Ti-Cu system and the role of copper in stabilising austenite. Findings show that high Cu concentrations (7 wt.%) enhance hardenability by 13%, effectively suppressing pearlite transformation and expanding the bainite region. The desired chemical composition of the deposited metal is determined by the distribution of selected factors, as measured by the transfer coefficients of each element.
This study introduces a hybrid optimization method to enhance the melting characteristics and weld bead morphology of flux-cored wire hardfacing with exothermic addition into the core filler. The Taguchi Design of Experiments (L9 orthogonal array) was used to analyze the effects of key conditions on multiple melting characteristics. The hybrid Taguchi-GRA-PCA effectively identified the best parameter combination, resulting in a significant improvement in overall melting performance. The impact of welding modes on weld bead parameters and melting characteristics was examined. It was determined that the optimal amount of the exothermic addition CuO-Al introduced into the flux-cored wire filler should be a medium level (EA = 28 wt.%). Results showed that wire feed speed WFS and EA had the greatest effect on MOR and DR, while EA and CTWD mainly influenced SF and De. It has been determined that the content of the exothermic additive has a significant impact on the melting process of filler materials, affecting the melting characteristics and weld bead morphology. It has been found that the melting characteristics of deposition rate and spattering factor can be used to optimize welding modes and characterize most output parameters of the welding/surfacing process.
Purpose. To substantiate and describe a methodology for developing the physical fitness of students in grades 7-9 in general secondary education institutions of rural territorial communities through the use of football. Materials and Methods. An analysis was conducted of contemporary international and national publications on school football programs, recreational football, and small-sided games as a means of developing adolescents’ motor abilities, as well as regulatory and methodological documents on the organization of physical education in general secondary education institutions. Pedagogical modeling (goals, principles, content, conditions), design of training load (volume, intensity, interval structure), and construction of a system of control and assessment were applied. For monitoring, accessible field tests (speed, agility, endurance, strength qualities) were proposed, and a subjective rating of perceived exertion (RPE) scale was used to control intensity. Results. The methodology is structured into three blocks (organizational-content, training-methodological, and control-assessment) and includes a detailed algorithm for its implementation over 10-12 weeks with 2-3 sessions per week. The priority of small-sided games is substantiated as a universal tool for simultaneous teaching of technical and tactical actions and the development of endurance, speed, agility, and strength. An indicative calendar plan of the cycle, an algorithm for in-lesson load adjustment, a minimum list of equipment for a rural school, and a monitoring battery that allows tracking individual progress and timely load correction are presented. Conclusions. The proposed methodology is suitable for implementation in rural general secondary education institutions and combines the learning outcomes of the variable module «Football» with a safe increase in physical fitness and motivation for physical activity. Its practical value lies in the availability of ready-made solutions for organizing mixed groups, dosing intensity (through small-sided game formats and intervals), pedagogical control, and «school-community» partnership. Further research should focus on experimental verification of the methodology’s effectiveness and refinement of assessment standards with regard to age, sex, and initial fitness level.
The results of 3-D computer modeling of the total scattering cross section (TSCS) and the extinction cross section (ECS) for various silver nanoparticle structures in the optical band are presented. For modeling an electrodynamic method based on solving the set of Müller boundary integral equations (IEs) was used. The developed calculation techniques involve calculation of the electromagnetic (EM) responses of nanoparticle groups while taking into account their EM interaction, and allow studying the optical properties of 3-D nanoparticle structures of various configurations. Such results are important at the stage of creating nanomaterials with specified properties.
