Prediction of the Fillet Mass and Topology of Aluminum Brazed Joints

The topology of brazed joints can be predicted a priori with minimal empirical input. It is demonstrated that when one predicts with sufficient precision the mass of filler metal destined to flow into the joint zone, joint topology can be determined with assurance by using the proposed methodology and numerical modeling using a finite element code. The numerical approach to determination of brazed joint topology is based on the principle of minimum potential energy of the equilibrium membrane of the molten metal at the onset of solidification. The theoretical predictions of fillet mass and joint shapes are corroborated with experimental data, and independently with the numerical predictions obtained using general-purpose Surface Evolver interactive software. The predictions of the numerical modeling indicate not only whether or not the joint formation would likely be acceptable vs. the selection of materials and process parameters, but also all the important geometrical features of a joint and data necessary for determination of mechanical and thermal integrities of various brazed structures. Without an empirical input, best results are obtained when the residual layer is predicted by using a non-equilibrium assumption for modeling the clad melting prior to flow. If the empirical input is utilized, the best results are obtained when the residual layer is measured in situ.