Applying Laser-Ultrasonic and Acoustic-Emission Methods to Nondestructive Testing at Different Stages of Deformation Formation in Friction Stir Welding

The results of applying laser-ultrasonic and acoustic-emission nondestructive testing techniques to study the processes of deformation and fracture of friction-stir-welded joints are presented. The load-strain diagrams were obtained and the mechanical characteristics of the samples of welded joints made of an aluminum-magnesium alloy were determined. The laser ultrasonic method, based on the acoustoelasticity effect, was used to measure the mechanical stresses arising in welded joints during uniaxial loading of specimens in the elastic range. Acoustic emission signals arising during the tension strain of the samples of welded joints were recorded. It has been established that the nature of the distribution of the parameters of acoustic emission occurring during the destruction of faulty welded joints has some distinctive features. The activity and total acoustic-emission count were considered as informative parameters under the conditions of static uniaxial loading of the samples of welded joints.