Effect of surface tension on melt pool dynamics during laser pulse interaction

Abstract

A previously developed model for simulation of recoil-pressure induced melt displacement during laser pulse interaction has been upgraded to include the restraining effect of surface tension. The results of numerical simulations of melt displacement/ejection during laser welding and drilling using this enhanced model are presented. In particular, the dependences of the threshold pulse energies for melt displacement and melt ejection as functions of laser pulse duration, beam radius and beam intensity distribution are computed and analysed.

Experimental determination of temperature threshold for melt surface deformation during laser interaction on iron at atmospheric pressure

“…Let us consider the case of figure 1, where the central part is depressed due to P and the melt in the centre is redistributed to the periphery as an extruded rim [21]. The curvatures of the melt deformation in the central and rim parts are expressed by R and r m , respectively.…”

“…In order to estimate the curvature r m of the rim, we assume that the rim extruded above the sample surface is represented by a part of a torus which is cut at the sample surface, as in ref. [21]. This extruded volume should be provided from the depressed volume in the central part.…”

Porosity in millimeter-scale welds of stainless steel : three-dimensional characterization.

“…While the field has benefited from significant investigations to further understand and model heat :: material interaction among high power density laser welds [9,[11][12][13] , a portion of these investigations have focused specifically on the formation of porosity and its driving forces. Among these works, prevailing hypotheses assert that porosity seen in laser welds largely results from intermittent molten pool collapse brought about by a fluctuating imbalance between ablation recoil pressure, molten liquid surface tension and impacting pressure [14][15][16][17] .…”

“…Significant efforts have been undertaken by other investigators to model weld pool dynamics and even relate molten fluid flow to the final microstructure. Among these efforts, the most developed of computational models have centered around interactions due to surface tension [9] , resolving velocity and temperature fields [89,90] and/or combining energy balance with three-dimensional fluid flow models [12] . The observance of the transition to a recessed weld pool surface here is noteworthy as it clearly documents a specific set of processing parameters around which such an event occurs.…”

“…Later work [5] focused on providing understanding and corrective measures for related effects of laser welding, such as shape distortions. By the mid-2000's Sandia began integrating modeling heavily into investigations to more accurately determine the fundamental heat :: material interaction over a variety of laser and GTA welding processes [6][7][8][9][10] . While not an exhaustive list, the aforementioned do highlight the progression of Sandia's publicly available work in the field.…”