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This paper focuses on the mathematical and numerical modeling of the electric arc + laser beam welding (HLAW) process using an innovative model of the Yb:YAG laser heat source. Laser energy distribution is measured experimentally using a UFF100 analyzer. The results of experimental research, including the beam profile and energetic characteristics of an electric arc, are used in the model. The laser beam description is based on geostatistical kriging interpolation, whereas the electric arc is modeled using Goldak's distribution. Hybrid heat source models are used in numerical algorithms to analyze physical phenomena occurring in the laser–arc hybrid welding process. Thermal phenomena with fluid flow in the fusion zone (FZ) are described by continuum conservation equations. The kinetics of phase transformations in the solid state are determined using Johnson–Mehl–Avrami (JMA) and Koistinen–Marburger (KM) equations. A continuous cooling transformation (CCT) diagram is determined using interpolation functions and experimental research. An experimental dilatometric analysis for the chosen cooling rates is performed to define the start and final temperatures as well as the start and final times of phase transformations. Computer simulations of butt-welding of S355 steel are executed to describe temperature and melted material velocity profiles. The predicted FZ and heat-affected zone (HAZ) are compared to cross-sections of hybrid welded joints, performed using different laser beam focusing. The obtained results confirm the significant influence of the power distribution of the heat source and the laser beam focusing point on the temperature distribution and the characteristic zones of the joint. [ABSTRACT FROM AUTHOR]

The paper concerns numerical simulations of progressive hardening include phase transformations in solid state of steel. Abaqus FEA software is used for numerical analysis of temperature field and phase transformations. Numerical subroutines, written in fortran programming language are used in computer simulations where models of the distribution of movable heat source, kinetics of phase transformations in solid state as well as thermal and structural strain are implemented. Model for evaluation of fractions of phases and their kinetics is based on continuous heating diagram and continuous cooling diagram. The numerical analysis of thermal fields, phase fractions and strain associated progressive hardening of elements made of steel were done.

This work concerns issues of mathematical modelling of phase transformations in steels during a high-speed high-power heat source welding processes. The analysis of the influence of thermal cycle parameters such as: heating rate, cooling rate and the maximal heating temperature on the kinetics of phase transformations during heating and cooling is performed. The verification of classical mathematical and numerical models of phase transformations is presented in relation to advanced welding methods using a high-speed high-power heat source on the basis of data found in the literature and experimental research. [ABSTRACT FROM AUTHOR]

Numerical analysis of thermal treatment processes is an important issue to be considered by contemporary laboratories dealing with industrial designing in general. Phenomena associated with heat treatment are complex and not yet adequately explained. Improvement in this field of numerical solutions is particularly forced by industry which, striving for deployment of state of the art technologies and reduction of costs, is demanding continuous enhancement of tool thermal treatment. Phase transformations, in particular in cooling processes, involve considerable changes in kinetics that are not always associated with external thermal impact. Analyses of experimental data allowed developing many mathematical models to measure volume fractions of phase transformations in solid state. The Johnson-Mehl Avrami equation and generalised Kolmogorov equation are the two primary models applied in almost all tests evaluating transformation of austenite into ferrite, bainite and martensite. In order to calculate the martensitic phase volume fraction, usually the Koistinen-Marburger equation, or any of its modified formulas, are used. [ABSTRACT FROM AUTHOR]

This work concerns mathematical and numerical modelling of temperature field during hybrid welding process using Yb:YAG laser and electric arc in GMAW method. Numerical analysis is performed taking into account the motion of liquid steel in the fusion zone. Yb:YAG laser power distribution is determined on the basis of experimental research made on TruDisk 12002 laser. Geostatistical Kriging method is used in the interpolation of Yb:YAG laser power intensity distribution. Temperature field and melted material velocity field in the fusion zone of hybrid welded sheets made of S355 steel are obtained on the basis of numerical solution of continuum mechanics equations in Chorin's projection method and finite volume method. Experimental research of laser beam profile is performed in order to verify the correctness of developed heat source model. Fusion zone and heat affected zone geometry is predicted on the basis of calculated temperature field in the cross section of hybrid welded joint. [ABSTRACT FROM AUTHOR]