Numerical Simulation Of Temperature And Stress Field In Fibre Laser Keyhole Welding Orienting Prediction Of Weld Shape

Weld shape directly resulting from thermal process, is an important assessmentcriteria of weld quality in laser keyhole welding. It is of theoretical and practicalengineering significance to model the thermal process in laser keyhole welding to predictweld shape and validated it with experment results. For fibre laser keyhole welding,existing thermal source can not consider well and reasonably the energy distribution, even,most models are constructed for a narrow range process parameters, rarely predicting theweld shape in both full-penetration and partial-penertration laser welding.In this paper, a3D FEA model about301L stainless steel was established fortemperature and stress field analsis in fibre laser keyhole welding. Considering thecharasteristics of fibre laser keyhole welding, an advanced combined heat source wasbrought up, which is consist of a surface heat flux and a cylindrical heat source withincreasing peak heat fulx through the depth, based on the combined heat source which isconsist of a surface het flux and cylindrical heat source, and on that basis, an FEA methodfor calculating temperature and stress field is proposed. In order to verify the FEA modelfor temperature field, a system for detecting thermal cycles in laser welding is set up,which is assisted by Labview software on the hardware basis of USB data acquisitionboard and quick response thermocouples. Detection results indicated that the model isreliable. Ultimately, the prediction of weld shape in full-penetration and partial-penetrationlaser welding was realized well, using revised thermol source parameters got fromassociation of experement and simulation results.Via the comparisom and error analysis of predicted and practical shape and size, theauthor found that, as for partial-penetration laser welding, heat model parameters isinsensitive to laser power and welding speed change, so that, small error appears in thiscase. While, in another case, only the error of weld shape waist size is relatively bigger,except that, other sizes like top width, bottom width, depth of weld are generally identical with experement results.Finally stress field was analysed in the condition of laser power at3kW and weldingspeed at1m/min. The simulation results of residual stress distribution is accordance withtheoretical description.