LAUSR

The presence of residual stresses in components can contribute to cracking and reduction of fatigue life. Therefore, residual stress assessment in structures is essential for optimization of the structures’ design. The attention of this paper is focused on how acoustic emission signals caused by the tensile tests of the friction stir welded aluminum plates are expected to vary depending upon the residual stress inside the material. To this aim, the distribution of residual stresses in two friction stir welded aluminum specimens was firstly evaluated by ultrasonic stress measurement. The hole-drilling method was also utilized to validate the obtained results. AE signals were then introduced into the tensile tests while the generated AE signals were captured using AE sensor. The obtained AE signals were analyzed using statistical features including crest factor, cumulative crest factor and sentry function. It was found that the crest factor could be used to identify the presence of the residual stresses while the trends of sentry function are in good agreement with the results of crest factor and cumulative crest factor which make it possible to discern the stress severity of friction stir welded specimens.