Logarithmic damping decrement in the diagnosis of welded joints

The article presents a vibrodiagnostic, non-destructive assessment method of welded joints where damping decrement change was used. SHM importance in sea constructions was discussed. Responses received while inspection (registered by acceleration sensors) provide diagnostics that require mathematic processing to extract the important characteristics of examined welded joints that were recorded and to assess quality of the joint. A method based on calculation of the damping decrement which changes over time as the response changes was presented in the paper. Due to complicated course of the responses, the damping decrement was calculated using approximation of the responses by many mathematical functions. The result of the analysis shows that the damping decrement change over time allows assessing quality of the joint when used in welded plates. Elements vital to carrying out examination of welded plates using vibrodiagnostic method were discussed, an calculation algorithm and example results of applicating this method at welded plates with several different detects were presented.