Detection of defects in bulging processes by means of dynamic laser speckle

Abstract

The method described in this paper has been used to determine the moment when defects appear in the form of strain localization and grooves in the Marciniak bulging tests. In this method based on dynamic laser speckle, the sheet is illuminated by laser. Interference after reflection from the specimen surface creates a characteristic image of bright and dark spots. Specimen surface changes related with deformations and movements cause changes in the shape and size of spots, which are presented by authors in the form of speckle activity image. In order to identify the type of defect, the additional 3D microscopy measurements were performed. This paper presents analysis of the changes in the speckle activity image during the bulging process which enabled the defects identification during the bulging process.