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Arc interaction and molten pool behavior in the three wire submerged arc welding process
Kiran, Degala Venkata,Cho, Dae-Won,Song, Woo-Hyun,Na, Suck-Joo Elsevier 2015 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.87 No.-
<P><B>Abstract</B></P> <P>A three-dimensional numerical heat transfer and fluid flow model is developed to understand the temperature distribution and molten pool behavior in a three wire submerged arc welding process. The model solves the equations of the conservation of mass, momentum, and energy along with the volume of fluid method. The volume of fluid method is used to track the shape of the free surface. Further, a physical model is developed to estimate the arc center displacement. For a given welding condition, connecting the leading electrode with direct current electrode positive polarity, the middle and trailing electrodes with trapezoidal alternating current waveform displayed deeper weld pools when compared to the sine waveforms. Within the range of welding conditions considered in the present work, weld width is significantly influenced by the leading arc whereas the penetration by the middle and trailing arcs. The computed weld width and penetration are in fair agreement with the corresponding experimental results.</P>
CFD based visualization of the finger shaped evolution in the gas metal arc welding process
Cheon, Jason,Kiran, Degala Venkata,Na, Suck-Joo Elsevier 2016 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.97 No.-
<P><B>Abstract</B></P> <P>A CFD based numerical study of the gas metal arc welding process was used to visualize momentum flow in the produced fingertip shaped molten pool. Arc process models were employed with temperature-independent material properties in a phase, and measured process parameters. The results of the welding simulation were in good agreement with the etched cross-section microscopy and temperature history of the experimental results. Molten pool speed information was utilized to track momentum flow in the weld pool using color maps and streamline plots. As results, it was determined that the droplet impingement momentum first strikes the bottom of the molten pool and digs a deep fingertip penetration. Then, the droplet impingement momentum detours backward at a deep level and moves forward at a shallow level, and widens the molten pool width.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The CFD GMAW simulation results were in good agreement with experimental results. </LI> <LI> The droplet impingement momentum was tracked velocity information. </LI> <LI> Initially the droplet digs a deep fingertip penetration. </LI> <LI> Next, the droplet impingement momentum detours backward at a deep level. </LI> <LI> And it moves forward at a shallow level, and widens the molten pool width. </LI> </UL> </P>
CMT 와이어-아크 적층 공정에 대한 용융풀 거동 분석
조대원(D. W. Cho),Degala Venkata Kiran(D. V. Kiran) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월
본 연구는 Cold Metal Transfer 로 Wire Arc Additive Manufacturing 시 발생하는 용융풀 거동에 대한 해석을 수행하였다. 초고속 카메라로 실시간으로 변하는 아크의 전류, 전압, 아크 형상을 동기화하여 계측하였으며 이를 토대로 실시간으로 변하는 아크 모델(아크 열원, 전자기력, 아크 압력)에 대한 모델링이 가능하였고, 아크가 주기적으로 On/Off 되는 시간을 고려하여 시간에 따른 과도해석을 수행하여 아크가 점멸하였을 경우 용융금속이 이행되는 과정도 모사할 수 있었다. 본 연구에서 활용하는 용적 이행 특성과 아크가 주기적으로 On/Off 되는 특성을 활용하여 실제적으로 유사한 비드 형상을 얻을 수 있었다. 특히 이러한 특성을 검증하기 위해 동일한 입열에서 아크 형상과 전류, 전압이 시간에 관계 없이 유지되는 경우, 아크 형상은 변하지만 전류, 전압이 일정한 경우, 실제와 비슷하게 아크 형상 및 전류, 전압이 시간에 따라 변동되지만 용적이행이 Spray 모드인 경우에 대해 비교 분석을 수행하였다. 결론적으로는 아크가 실시간 변하는 특성뿐만 아니라 용착 금속이 이행되는 특성을 모두 고려해야 실제와 유사한 비드 형상을 얻을 수 있게 되었다. 결론적으로 실험 결과와 해석에 사용한 모델과의 비교 분석을 통해 본 연구에 적용한 모델의 적합성을 확인할 수 있었다.
Cho, Dae-Won,Kiran, Degala Venkata,Na, Suck-Joo Pergamon Press 2017 International journal of heat and mass transfer Vol. No.
<P><B>Abstract</B></P> <P>A three-dimensional numerical heat transfer and fluid flow model is developed to understand the temperature distribution and molten pool behavior in a low-current submerged arc welding process. The model solves the equations of the conservation of mass, momentum, and energy along with the volume of fluid method. The volume of fluid method is used to track the shape of the free surface. Further, this paper suggests a flux wall boundary model to simulate flux-wall guided transfer for a single-wire low-current submerged-arc welding process. This study simulates how porosity can be trapped in the V-groove joint with a flux-wall guided transfer. The computed weld width and fusion-zone shape are in fair agreement with the corresponding experimental results.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Flux-wall guided metal transfer model is developed. </LI> <LI> CFD simulation for low current SAW process is done. </LI> <LI> Molten pool behaviors by flux-wall guided transfer and spray model for low-current SAW were analyzed. </LI> </UL> </P>