January 2007
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Truchas Software Applications Extended within Complex

As part of the ASC Engineering Verification and Validation (V&V) Project, the Los Alamos casting simulation software Truchas has been assessed for extending its application to other problems such as welding within the DOE Nuclear Weapons Complex.

Truchas is a 3D casting simulation code, a product of the ASC-funded Telluride project. Truchas simulates the entire casting process: flow of molten alloy, heat transfer, solidification of alloy, induced stresses, etc.

Two QuickTime movies generated from Truchas simulations show 3-D animation sequences of weld pool development in two cases of laser spot welding. The color scale is temperature (Kelvin), and the number at the top right corner indicates time (t) (in seconds). At t = 0, a laser beam is activated to heat and melt stainless steel at a spot on its top surface for a duration of 4ms. After the beam is turned off, the weld pool begins to cool and completely re-solidifies at 6.6 ms. Black arrows indicate velocity vectors, which also mark the presence of liquid (i.e., define the weld pool region). The two movies illustrate opposite signs of the parameter dσ/dT the coefficient of change of surface tension with respect to temperature. The simulations show that for a positive coefficient, the flow is downward in the center, giving rise to a deeper weld penetration, as compared with the case for a negative coefficient (see also figure, below). While the simulation is 3-D, the 2-D representation shown in these movies represent a slice of the calculation results at the center of the simulation. This study employed experimental data from the LANL Welding and Joining Team and the Sandia Joining and Coating Department, in collaboration with Penn State University researchers for the validation problems.

Two simulations compared at equivalent times.

Comparison of the two simulations at equivalent times. Black horizontal line is artificially inserted to assist in ascertaining deeper weld penetration in the simulation, at left (positive coefficient). Explanations contributed by Kin Lam, LANL.

 

QuickTime movie 1 [2.9 MB]

QuickTime movie 2 [2.8 MB]