Application of acoustic emission and laser optoacoustics at various stages of defect formation during friction stir welding

Abstract

This paper covers basic aspects of laser ultrasound and acoustic emission non-destructive testing methods in application of monitoring friction stir welds during its deformation and fracture. Stress-strain curves for such welds were obtained and the mechanical characteristics of welded joints of aluminum-magnesium alloy were determined. Using acoustic elastic effect levels of mechanical stresses were measured. Signals of acoustic emission, stimulated by one-axis loading, were registered and analyzed. It was established that acoustic emission during deformation and fracture of samples of welded joints is associated with the course of the process of plastic flow of the material. The nature of the distribution of acoustic emission parameters in the destruction of welded joints with defects has distinctive features. In conditions of one axis quasi static loading rate event count acoustic emission is the most informative parameter.