Modelling and Analysis of Phase Transformations and Stresses in Laser Welding Process / Modelowanie I Analiza Przemian Fazowych I Naprężeń W Procesie Spawania Laserowego

Abstract

The work concerns the numerical modelling of structural composition and stress state in steel elements welded by a laser beam. The temperature field in butt welded joint is obtained from the solution of heat transfer equation with convective term. The heat source model is developed. Latent heat of solid-liquid and liquid-gas transformations as well as latent heats of phase transformations in solid state are taken into account in the algorithm of thermal phenomena. The kinetics of phase transformations in the solid state and volume fractions of formed structures are determined using classical formulas as well as Continuous-Heating-Transformation (CHT) diagram and Continuous-Cooling-Transformation (CCT) diagram during welding. Models of phase transformations take into account the influence of thermal cycle parameters on the kinetics of phase transformations during welding. Temporary and residual stress is obtained on the basis of the solution of mechanical equilibrium equations in a rate form. Plastic strain is determined using non-isothermal plastic flow with isotropic reinforcement, obeying Huber-Misses plasticity condition. In addition to thermal and plastic strains, the model takes into account structural strain and transformation plasticity. Changing with temperature and structural composition thermophysical parameters are included into constitutive relations. Results of the prediction of structural composition and stress state in laser butt weld joint are presented.

Quantification of Interdependent Dynamics during Laser Additive Manufacturing Using X‐Ray Imaging Informed Multi‐Physics and Multiphase Simulation

“…To determine the phase transition, a simple enthalpy‐porosity formulation was used based on refs. [ 88 , 89 , 90 ]. The phase transformation was bound by the liquidus and solidus temperatures.…”

Modeling of Yb:YAG Laser Beam Caustics and Thermal Phenomena in Laser–Arc Hybrid Welding Process with Phase Transformations in the Solid State

“…The heat flux due to material evaporation depends on alloy constituents and can be defined as follows [35,44,45]:…”

“…Based on the data given in [35,44], a unified model of average evaporation flux is considered in the temperature range (T L ; T max ), where T max is the maximum temperature of the thermal cycle and T L is the liquidus temperature:…”

“…The laser power is absorbed in the ionized vapor and transferred to the walls of the "keyhole", forming the weld pool. The mechanism of material melting by a laser beam, considered in engineering practice as a simplified model without recoil pressure, is usually recognized as a volumetric heat source model [35,39,46,47]. In this work, the volumetric heat source power distribution is calculated assuming interpolated distribution in the radial direction, with the "keyhole" considered a truncated cone with a linear decrease in energy intensity with material penetration:…”

“…Changes in the HAZ microstructure, including phase transformations and grain growth, are the cause of significant changes in the properties of this area compared to the base material. Different heating and cooling conditions during heat treatment contribute to the emergence of various structures in the HAZ, which leads to different mechanical properties [30][31][32][33][34][35].…”