Acoustic Emission as an Indicator of Laser-cutting Quality

The paper presents results of an analysis of acoustic emission (AE) signals captured in the course of laser cutting of a steel sheet, and the analysis of the signals characteristic of particular phenomena occurring after the cutting process. In the course of cutting, continuous signals, which are related to the quality achieved of the laser cut, are measured. After laser cutting characteristic AE bursts in the specimen material, which are results of a thermal influence, can be detected. A relation between the AE bursts and dross formation at the lower edge of the cut is shown. The presence of dross is an important indicator of poor quality of laser cutting. The investigation on laser cutting was conducted on an unalloyed steel DC04 sheet and on austenitic stainless steel X5CrNi18-10 sheet of 1,5 mm in thickness. These grades of steel sheet are frequently used in the production of body components in the automotive industry. In this case laser cutting and welding are often used to give a final shape to functional components. The same physical mechanism in the cut formation at both steels, however, resulted in a considerable different cut quality, which was indicated by the AE signals captured after the cutting process. Further on, an application of AE measurement during laser cutting of a larger deep-drawn product, where the magnitude of residual stresses and, consequently, because of cutting, relaxation and distortion of the cut part are important, is shown.