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RISS 인기검색어
- 검색키워드
- 저자 : John O. Milewski (검색결과 2 건)
- 무료
- 기관 내 무료
- 유료
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Numerical analysis of weld pool oscillation in laser welding
조정호,Dave F. Farson,Kendall J Hollis,John O. Milewski 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.4
Volume of fluid (VOF) numerical simulation was used to investigate melt flow and volumetric oscillation of conduction-mode pulsedlaser weld pools. The result is compared to high speed video stream of titanium laser spot welding experiment. The total simulation timeis 10ms with the first 5 ms being heating and melting under constant laser irradiation and the remaining 5 ms corresponding to resolidificationof the weld pool. During the melting process, the liquid pool did not exhibit periodic oscillation but was continually depressedby the evaporation recoil pressure. After the laser pulse, the weld pool was excited into volumetric oscillation by the release ofpressure on its surface and oscillation of the weld pool surface was analyzed. The simulation model suggested adjusting thermal diffusivityto match cooling rate and puddle diameter during solidification which is distinguishable from previous weld pool simulation. Thefrequency continuously increased from several thousand cycles per second to tens of thousands of cycles per second as the weld poolsolidified and its diameter decreased. The result is the first trial of investigation of small weld pool oscillation in laser welding althoughthere have been several reports about arc welding.
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Weld pool flows during initial stages of keyhole formation in laser welding
Cho, Jung-Ho,Farson, Dave F,Milewski, John O,Hollis, Kendall J Institute of Physics [etc.] 2009 Journal of physics. D, applied physics Vol.42 No.17
<P>Weld pool transport phenomena during the transition from conduction-mode laser spot welding to keyhole laser spot welding of titanium were studied by numerical simulation. A range of laser powers were simulated and temperature dependent evaporation recoil pressure and cooling were applied as boundary conditions on the weld pool surface. Simulation results predicted a complex time-varying flow pattern during weld pool development. The surface-normal flow at the weld pool centre oscillated between upwards and downwards during the simulation time due to interaction of competing effects of evaporation recoil and surface tension pressures and laser heating and evaporation cooling. The results show that the laser weld pool flow dynamics play a key role during the transition from conduction-mode laser welding to keyhole welding.</P>
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