Optimization of an Ultrasonic Non-Destructive Evaluation Technique for Laser Brazing

Brazing joins two sheets along a seam using a filler metal. In the brazing process, the filler metal is heated, along with the parts to be joined, to a temperature above the melting temperature of the filler material. This allows the filler metal to wet the surfaces of the parts to be joined through capillary action, resulting in the formation of metallic bonds, ultimately forming the joint. Brazing, like all joining methods, is also susceptible to process variations. These process variations can include wear of the laser, plate misalignment, and external temperature changes. If left unchecked, such variations can eventually lead to the formation of defects, which bring a joint outside of the performance criteria specified in its engineering design. As such, reliable evaluation of these joints ensuring adequate quality is of great importance. To do this, the development of a non-destructive evaluation technique based on ultrasound phased array measurement has been investigated and determined viable in its application. In this work, we explore refinements to the imaging process, including the use of multi-angle acquisition, optimizations related to the array geometry, and the selection of an optimal coupling medium. These optimizations allow for improved robustness of the imaging process with the resulting comparison to prior acquisition techniques discussed