Simulation techniques are useful tools for study and research of new welding technologies, and for the rapid development of new control algorithms and control units as are power source circuits, and welding current or voltage controllers. The objective in this research is to combine the simulation of Gas Metal Arc Welding (GMAW) process models with the simulation models of inverter based power machines. The GMAW process is considered as an electrical circuit and the mathematical model is based on physical descriptions of several parts of GMAW process, as are the electric circuit of power supply, the arc dynamics, and the electrode melting process. To establish the validity of the proposed GMAW model, a simple welding application was simulated and welding parameters ware derived from experimental conditions. Next, the simulation model of full-bridge DC-DC converter is presented and the discrete PI controller for welding current feedback control is proposed. Both models, the GMAW model and the inverter power supply model, are combined and simulated together.
COBISS.SI-ID: 15757078
The subject of this paper is a surface-integrity analysis of Ni-Co-Mo laser cladded maraging steel (EN 10027-2, W. No. 1.2799). Experiments were performed on 3.3 kW Nd:YAG laser system with coaxial injection of Ni-Co-Mo powder alloy that integrates various modes of laser beam guidance and different degrees of overlapping. The specimens were subsequently solution and precipitation annealed in order to examine a precipitation hardening of the newly formed material using the scanning electron microscopy (SEM) with a microprobe for energy-dispersive spectroscopy analysis, supported by microhardness tests. The residual stresses were determined by a hole-drilling method, using the integral method for residual stresses calculation. Favourable compressive residual stresses are generated in laser cladded layers due to a phase transformation from austenite to lath-martensite. The optimal selection of laser cladding process parameters enables efficient and cost-effective maintenance of damaged surfaces on the vital parts of die-casting tools, made from 1.2799 maraging steel.
COBISS.SI-ID: 12049435
The laser surface remelting (LSR) process is applied to modify the surface properties of nodular cast iron and is suitable for manufacture of various machine and tool parts. Usually, studies of surface remelted layers include microstructural and microchemical analyses, measurements of residual stresses, and various wear and corrosion tests. This paper will represent microstructural and microhardness analyses of the thin surface layer after laser remelting of nodular cast iron 500-7. Particular attention is paid to fatigue crack initiation and propagation tests. Crack initiation and growth behavior was assessed under bending test conditions. The comparison is made between as-received nodular cast iron 500-7 and the same material, where one of the surfaces is altered with the LSR process. As the crack propagation is perpendicular to the laser remelted layer, the specimens with a thin laser surface remelted layer exhibited higher resistance to fatigue crack growth in the low stress intensity factor range ?Kth than as-received nodular cast iron specimens. Also, ?KIC is higher in the case of the laser remelted surface.
COBISS.SI-ID: 12120091