Modelling of ceramic to metal brazed joints—a fracture mechanics finite elements approach

ABSTRACT Increasingly, in many aerospace and combustion engine applications, alloys are being coated by protective layers of ceramic, which are usually subjected to large thermal stresses. In spite of the progress in coating and brazing technology, many problems remain to be resolved. One of the tools recently employed to analyze such problems is the finite element method (FEM). Researchers have applied this method to verify the effects of irregularities, which are the major cause of crack initiation and debonding in the brazed components. On the other hand, this problem, which is analogous to the cracked media problem, has been examined by linear elastic fracture mechanics (LEFM). Unfortunately, the analytical solution to this problem is quite complex in nature, and is solvable only for simple geometrical cases. In this study the braze problem is analyzed by a special purpose fracture mechanics finite element program. The applicability of this program is shown, and the results are verified against the analytical complex solution. This results are also compared to the results obtained by ordinary an finite element program. The advantages in using special purpose fracture element for this type analysis is also discussed.