Determination of crack initiation in an interior cold-weld by combining reverse engineering and digital image correlation analysis

摘要

Micro-electronic devices very often contain joints which are vital for operation, but are no longer accessible after assembly. This is especially true for cold welds, as they are formed by applying a certain contact pressure. Isolating the joint by cutting would inevitably relax this contact pressure and seriously disturb or even destroy the joint. A solution to this problem is presented in terms of a multi-step reverse engineering approach. First, the geometries of the components in question are precisely determined by CT-analysis. Then the dynamic assembly process is simulated, and the spatial distribution of contact stresses is derived. A cohesive zone model is introduced which represents the cold-weld zone. Then the assembled component is subjected to mechanical loading, and its deformation field is determined using digital image correlation. Monitoring points susceptible to the onset of damage can be determined from the simulation model, and their deformation is recorded during the tests. It is shown that this procedure gives reliable estimates of the critical loads required for crack initiation.