Modal analysis for the non-destructive testing of brazed components

In brazing processes, the formation of defects within the brazing joint due to deviations in brazing process and material is a recurring problem. These affect the component quality as well as the component properties. In this study, modal analysis is fundamentally investigated as a potential tool for non-destructive testing of brazing joints as well as for fast quantification of the precision of the brazing process. The aim of the investigation is to detect defects in brazed components. For this purpose, test specimens in defect-free and defect-containing form are brazed by means of a high-vacuum furnace. The subsequent recording and real-time analysis of the oscillation behavior of these test specimens is to be used to evaluate the quality of these brazed joints. A method, developed specifically for this purpose, automatically evaluates the recorded oscillation profile based on several defined frequency positions. For the first time, the results show that a reproducible classification of brazing seam quality into OK and not-OK can be made by comparing several frequency positions with already known oscillation profiles.