Dissertation
CAPILLARY FLOW OF A BRAZING ALLOY IN NORMAL AND MICRO-GRAVITY CONDITIONS: COMPUTATIONS
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2021
DOI:
https://doi.org/10.7273/000003360
Handle:
https://hdl.handle.net/2376/122602
Abstract
The hole-filling problem arises from application of brazing for repairs in space under micro-gravity conditions. The negligible effects of gravity and dominance of capillary forces can be approximated under terrestrial conditions, provided that the hole and the quantity of liquid are small, as quantified by the Bond number. We report experimental results, modeling, and analysis, of the hole-filling problem using the liquid aluminum brazing alloy on aluminum substrate. Depending on the hole size, the capillary driven flow may result in the hole being either filled or not filled. The equilibrium problem (energy minimization) has multiple solutions in some regions of the parameter space. Therefore, the experimental outcomes may depend on the availability of sufficiently strong perturbation, required to dislodge the system from a meta-stable equilibrium. In general, a deeper and narrower hole favors the filled outcome.In addition, we consider features of an anomalous flow which includes: (i) an abrupt or a gradual recession of the contact line, and (ii) receding contact angle drop and an overshoot over the non-wetting surface. To analyze the mechanics of such flow, we use the phase field formulation for capillary flows with the diffusive motion of the triple line. The novel diffusive boundary condition with the time-evolving quasi-equilibrium contact angle is formulated and implemented into the phase field model. We discover that the observed anomalies in capillary flow are qualitatively explained by two factors: (1) Time evolution (ageing) of the quasi-equilibrium contact angle and, (2) high viscosity of the partially molten braze. We also discover that for the given flow geometry, the transition from the initial to the final configuration may follow two distinct topological paths: one is characterized by a coalescence of liquid-solid contact domains, the other by a contact line separation. The selection of the two paths in the configurational space is dependent on both contact ageing parameters and viscosity.
Finally, we investigate the effects of gravity of molten alloy on a combined wetting/non-wetting configuration. The experimental and computational results were tested under terrestrial and micro-gravity conditions. We find that the wetting distance increases as the inclined angle of the setup changes.
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Details
- Title
- CAPILLARY FLOW OF A BRAZING ALLOY IN NORMAL AND MICRO-GRAVITY CONDITIONS: COMPUTATIONS
- Creators
- Konstantinos Ioannis Lazaridis
- Contributors
- Sinisa Dj Mesarovic (Advisor)Prashanta Dutta (Committee Member)Nikolaos Voulgarakis (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Mechanical and Materials Engineering, School of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 93
- Identifiers
- 99900652205301842
- Language
- English
- Resource Type
- Dissertation