Numerical Modelling Of Thermal And Structural Phenomena In Yb:YAG Laser Butt-Welded Steel Elements

Abstract

MODELOWANIE NUMERYCZNE ZJAWISK CIEPLNYCH I STRUKTURALNYCH W ELEMENTACH STALOWYCH SPAWANYCH DOCZOŁOWO WIĄZKĄ LASERA Yb:YAGThe numerical model of thermal and structural phenomena is developed for the analysis of Yb:YAG laser welding process with the motion of the liquid material in the welding pool taken into account. Temperature field and melted material velocity field in the fusion zone are obtained from the numerical solution of continuum mechanics equations using Chorin projection method and finite volume method. Phase transformations in solid state are analyzed during heating and cooling using classical models of the kinetics of phase transformations as well as CTA and CCT diagrams for welded steel. The interpolated heat source model is developed in order to reliably reflect the real distribution of Yb:YAG laser power obtained by experimental research on the laser beam profile.On the basis of developed numerical models the geometry of the weld and heat affected zone are predicted as well as the structural composition of the joint.Keywords: Laser welding, heat transfer, phase transformations, numerical modelling, Kriging method Praca dotyczy modelowania numerycznego zjawisk cieplnych i strukturalnych w procesie spawania laserem Yb:YAG z uwzględnieniem ruchu ciekłego materiału w jeziorku spawalniczym. Pole temperatury i pole prędkości ciekłej stali w strefie przetopienia otrzymano z numerycznego rozwiązania równań mechaniki ośrodków ciągłych metodą projekcji Chorina i metodą objętości skończonych. Przemiany fazowe w stanie stałym analizowano podczas nagrzewania i chłodzenia bazując na klasycznych modelach kinetyki przemian fazowych oraz wykresach CTA i CTPc-S. W celu wiarygodnego odzwierciedlenia rzeczywistego rozkładu mocy lasera Yb:YAG opracowano model interpolowany źródła, wykorzystujący badania doświadczalne profilu wiązki laserowej. Na podstawie opracowanych modeli numerycznych prognozowano geometrię spoiny i strefy wpływu ciepła oraz skład strukturalny złącza.

Numerical estimation of temperature field in a laser welded butt joint made of dissimilar materials

“…The numerical analysis of heat transfer in the Abaqus software is based on the energy conservation equation and Fourier's law, expressed as follows [6,13]:…”

“…Temperature field is expressed in the criterion of weighted residuals method. Simulations are carried out in Lagrange's coordinates, where coordinates of the center of heat source is determined at each time step, depending on the welding speed [6]. Equation (1) is completed by the initial condition…”

“…Perfect contact at the interface between joined parts is assumed in the developed numerical model of butt joints [6,16]. The finite element mesh is used to provide good quality results with not long duration of the time simulation.…”

“…Most often arc welding or laser beam welding are used in in this type of joints. Each of these technologies involves specific conditions of heat distribution in the analyzed joints [3,6,7]. The quantity of heat impact into the welded material has a significant effect on the microstructure change and joint deformation [7,8].…”

“…View of welded beads for laser welded butt joint [9] Due to the cost of experiments, numerical modeling becomes a useful tool for analyzing the relevant technological parameters of the process [10,11]. Numerical modeling can greatly reduce costs of experimental research at the initial stage of construction design [6,9,12]. An important case of study in numerical research is a reliable representation of the real process and the appropriate adaption of mathematical and numerical models of the analyzed phenomena.…”